alkaline modified zirconia based catalyst for biodiesel

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Jul 5, 2011 - The removal of oxygen during the thermal processing also removes any ..... However, the presence of water accelerated formation of methyl ester. ..... the continuous production of methyl oleate (FAME) with high conversion.
ALKALINE MODIFIED ZIRCONIA BASED CATALYST FOR BIODIESEL PRODUCTION FROM WASTE COOKING PALM OIL

WAN NOR NADYAINI BINTI WAN OMAR

UNIVERSITI TEKNOLOGI MALAYSIA

PSZ 19:16 (Pind. 1/07)

UNIVERSITI TEKNOLOGI MALAYSIA DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT

Author’s full name :

WAN NOR NADYAINI BINTI WAN OMAR

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:

28 SEPTEMBER 1985

Title

:

ALKALINE MODIFIED ZIRCONIA BASED CATALYST FOR BIODIESEL PRODUCTION FROM WASTE COOKING PALM OIL ________________________________________________ ________________________________________________

Academic Session :

__2010/2011_______________________________________

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ALKALINE MODIFIED ZIRCONIA BASED CATALYST FOR BIODIESEL PRODUCTION FROM WASTE COOKING PALM OIL

WAN NOR NADYAINI BINTI WAN OMAR

A thesis submitted in fulfilment of the requirements for the award of the degree of Master of Engineering (Chemical)

Faculty of Chemical Engineering Universiti Teknologi Malaysia

JULY 2011

I declare that this thesis entitled “Alkaline Modified Zirconia Based Catalyst For Biodiesel Production From Waste Cooking Palm Oil” is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.

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Name

: WAN NOR NADYAINI WAN OMAR

Date

: 5th July 2011

iii

To everyone who love me and to all my love You’re are my friend, my love and my strength.

~ No pain no gain ~

ACKNOWLEDGEMENTS

Alhamdullillah, thanks to ALLAH s.w.t for HIS guidance and bless; I have finish my thesis project and finally have fulfil the demanding task of completing the thesis report. In preparing this thesis, I gained wonderful experiences, which is useful in the future. I am also was in contact with many people, researchers, academician and practitioners. They have contributed toward my understanding and thought. I would like to express my deep and sincere gratitude to my supervisor, Prof. Dr. Nor Aishah Saidina Amin . Her wide knowledge and her logical way of thinking have been of great value for me. Her understanding, encouraging and personal guidance have provided a good basis for the present thesis. Without her continue support and interest, this thesis would not have been the same as presented here. Besides, I wish to express my warm and sincere thanks to Pn. Roslindawati Haron and other colleague for the time, concern and friendship that they have present to collaborate in organizing the project My warm thanks are due lab assistant En Latfi, for cooperation and knowledge that we had shared together. I am also indebted to Ministry of Science, Technology & Innovation (MOSTI) for awarded me with national science fellowship (NSF) and Ministry of Higher Education (MOHE) for supporting the project under the Fundamental Research Grant Scheme (FRGS), Vote 78402. Besides, thank to all UTM staff especially SPS, RMC and UNIPEM for cooperation that had been given. Thanks also to Centre Point Café for the consideration to supply the waste cooking oil sample for my study. Last but not least, thanks to my beloved family, and friends for always understanding, supporting and encouraging me.

ABSTRACT

A new heterogeneous

catalyst for simultaneous esterification and

transesterification of waste cooking palm oil (WCPO) into their corresponding alkylester was successfully developed via wet-impregnation of alkaline nitrate salts with zirconia. The characteristics and catalytic activities of the alkaline modified zirconia catalysts (i.e. Mg/ZrO2, Ca/ZrO2, Sr/ZrO2, and Ba/ZrO2) in biodiesel production from WCPO were investigated. The alkaline modified zirconia catalysts are defined as a mesoporous catalyst which has large pore volume, surface area and also has suitable pore diameter for biodiesel production. Besides, alkaline modified zirconia catalyst increased the amphoteric nature of zirconia. Thus, the catalysts had high basicity and acidity amount. Among the catalysts, Sr/ZrO2 catalyst displayed the best characteristics and the most suitable catalytic activity for esterification and transesterification reaction in biodiesel production from WCPO. The performance of Sr/ZrO2 was studied in batch and continuous processes. Response surface methodology (RSM) and central composite design (CCD) were employed to explore the relationship of process variables (i.e. methanol to oil molar ratio, catalyst loading, reaction time, and reaction temperature) on methyl ester (ME) yield and free fatty acid (FFA) conversion as well as to find the optimum process condition. Reaction time and reaction temperature were found to be the limiting parameters for the batch process, with methanol-oil ratio for the continuous process. ME yield of 79.7% was produced in the batch process at 115.5oC, 169 min, 29:1 methanol-oil molar ratio and 2.7 wt% catalyst loading. Meanwhile, 93.61% of ME yield was produced from the continuous process at 153oC, 0.79 g oil g cat-1 h-1, 27:1 methanol-oil molar ratio and the catalyst can be reused for three times. The final products were found to be in a reasonable agreement with ASTM standard in term of the important physical properties.

vi

ABSTRAK

Satu pemangkin heterogenus baharu yang mampu mengesterifikasi dan mengtransesterifikasikan secara serentak sisa minyak masak kelapa sawit (WCPO) kepada alkil-ester masing-masing berjaya dihasilkan melalui impregnasi basah garam alkali nitrat dengan zirkonia. Ciri-ciri dan aktiviti katalitik mangkin zirkonia alkali terubahsuai seperti Mg/ZrO2, Ca/ZrO2, Sr/ZrO2, dan Ba/ZrO2 dalam penghasilan biodiesel daripada WCPO telah dikaji. Mangkin zirkonia alkali terubahsuai ditakrifkan sebagai mangkin mesoporos yang mempunyai isipadu liang yang besar, luas permukaan dan diameter liang yang sesuai untuk penghasilan biodiesel. Selain itu, mangkin zirkonia terubahsuai meningkatkan sifat amfoterik zirkonia. Oleh itu, mangkin mempunyai jumlah keasidan dan kealkalian yang tinggi. Di antara mangkin-mangkin, Sr/ZrO2 menunjukkan ciri-ciri yang terbaik dan aktiviti katalitik yang sesuai bagi tindakbalas esterifikasi dan transesterifikasi dalam penghasilan biodiesel daripada WCPO. Prestasi Sr/ZrO dikaji dalam proses berkelompok dan berterusan. Kaedah respon permukaan (RSM) dan rekabentuk komposit pusat (CCD) telah digunakan untuk mengkaji hubungan pembolehubah proses seperti nisbah metanol kepada minyak, muatan mangkin, masa tindakbalas dan suhu tindakbalas terhadap hasil metil ester (ME) dan penukaran asid lemak bebas (FFA) dan juga untuk mendapatkan keadaan proses yang optimum. Masa dan suhu tindakbalas didapati menjadi parameter penghad kepada proses berkelompok, dan nisbah minyak kepada metanol bagi proses berterusan. 79.7% hasil ME telah dihasilkan melalui proses berkelompok pada 115.5oC, 169 min, 29:1 nisbah molar metanol- minyak dan 2.7 % berat muatan mangkin. Sementara itu, 93.61 % hasil ME telah dihasilkan daripada proses berterusan pada 153oC, 0.79 g minyak g mangkin-1 j-1, 27:1 nisbah metanol-molar minyak dan mangkin boleh diguna semula sebanyak tiga kali. Produk akhir didapati mencapai piawai ASTM dari segi ciri-ciri fizikal yang penting.

TABLE OF CONTENTS

CHAPTER

TITLE

TITLE PAGE

i

DECLARATION

ii

DEDICATION

iii

ACKNOWLEDGEMENTS

iv

ABSTRACT

v

ABSTRAK

vi

TABLE OF CONTENTS

vii

LIST OF TABLES

xi

LIST OF FIGURES

xii

LIST OF SYMBOLS AND ABBREVIATIONS

1

2

PAGE

xviii

LIST OF APPENDICES

xx

INTRODUCTION

1

1.1 Background of Research

1

1.2 Statement of Problem

7

1.3 Hypothesis of Research

8

1.4 Objectives of Research

8

1.5 Scope of Research

8

1.6 Significant of Research

9

LITERATURE REVIEW

10

2.1

10

Biodiesel Production Process

viii 13

2.1.2 Acid Transesterification Reaction

14

2.1.3 Two-step Catalyzed Transesterification

15

2.1.4 Lipase Catalysed Transesterification

16

2.1.5 Supercritical Transesterification

18

2.2

Potential Feedstocks

20

2.3

Reaction of triglyceride in Biodiesel Production

23

2.3.1

Transesterification and Esterification

24

2.3.2

Hydrolysis

29

2.4

3

2.1.1 Base Catalysed Transesterification

Heterogeneous Catalyst in Transesterification

31

2.4.1

Metal Oxide

31

2.4.2

Transition Metal Oxide

33

2.4.3

Modified Zircornia

34

2.4.4

Solid Acid Catalyst

35

2.4.5

Mixed Metal Oxide

35

2.5

Effect of Parameter over Biodiesel Production

36

2.6

Continuous Process of Biodiesel

37

2.7

Catalyst Characterization Method

38

2.8

Biodiesel Standardization

42

METHODOLOGY

44

3.1

Research Methodology Approach

44

3.2

Material and Equipment

46

3.3

Experimental

48

3.3.1

Catalyst Preparation

48

3.3.2

Catalyst Characterization

49

3.3.3

Pre-test of Catalyst

51

3.4

3.5

Performance of the Catalyst

52

3.4.1

Batch Biodiesel Production

52

3.4.2

Continuous Biodiesel Production

54

Product Analysis

56

3.5.1

FAME Determination Using GCMS

56

3.5.2

Physico-chemical Properties

57

ix 3.6

4

Formulation of Response

58

RESULT AND DISCUSSION

59

4.1

59

Development of Alkaline Modified Zirconia Catalyst for Biodiesel Production 4.1.1 Characterization of Catalyst

59

4.1.1.1 Crystallinity

59

4.1.1.2 Physico-Chemical Properties of Catalyst

63

4.1.1.3 Basicity and Acidity

65

4.1.2 Screening of Alkaline Modified Zirconia in

70

Batch Process 4.1.3 Relationship of Basicity and Acidity of Modified

73

Catalyst on Biodiesel Production 4.1.4 Possible Mechanism Suggestion for

75

Simultaneous Esterification and Transesterification. 4.2

Influence of Process Variables on the Biodiesel

77

Production Over Sr/ZrO2 in Batch Process 4.3

Optimization of Biodiesel Production from Waste

80

Cooking Palm Oil via Response Surface Methodology over Sr/ZrO2 4.3.1 Response Surface Methodology (RSM)

80

4.3.2 Biodiesel Production in One-Pot Stainless Steel

81

for Batch Process 4.3.2.1 Design of Experiment

81

4.3.2.2 Validity of Model

82

4.3.2.3 Interaction of Process Variable

88

4.3.2.4 Optimization of ME Yield

96

4.3.3 Biodiesel Production in Packed Bed Reactor for

97

Continuous Process. 4.3.3.1 Design of Experiment

97

4.3.3.2 Validity of Model

98

4.3.3.3 Interaction of Process Variables

103

x

4.4

5

4.3.3.4 Optimization of ME Yield

108

4.3.3.5 Reusability of Catalyst.

109

Characteristic of Biodiesel

110

4.4.1

Observation of Biodiesel

110

4.4.2

Physical Properties of Biodiesel

114

CONCLUSIONS AND RECOMMENDATIONS

116

5.1

Conclusions.

118

5.2

Recommendations

REFERENCES

120

APPENDICES A-E

129

LIST OF TABLES

TABLE NO

TITLE

PAGE

2.1

Summarize of instrument for catalyst characterization

40

2.2

Summarize of instrument for catalyst characterization

41

(continue)

2.3

Biodiesel Specification Standard.

43

3.1

The FFA profiles and properties of WPCO

46

4.1

The physicochemical properties of ZrO2 and the modified

62

zirconia catalyst

4.2

Total acidity and basicity of ZrO2 and the modified zirconia

70

catalyst

4.3

Experimental range and level coded

82

4.4

CCD and Experimental Result

83

4.5

ANOVA analysis

84

4.6

Predicted analysis of optimum condition for ME yield

96

xii 4.7

Comparison between predicted and experimental responses

97

at the optimum condition obtained from RSM.

4.8

Experimental range and level coded

98

4.9

CCD and Experimental Result

99

4.10

Analysis of variance (ANOVA) for product yield

101

4.11

Predicted analysis of optimum condition for ME yield

109

4.12

Comparison between predicted and experimental responses

109

at the optimum condition obtained from RSM.

4.13

The ME component from GC-MS analysis

111

4.14

The properties of ME

114

LIST OF FIGURES

FIGURE NO

1.1

TITLE

Transportation Diesel Oil Consumption for Asia Country

PAGE

2

(including Middle East)

1.2

Transportation Diesel Oil Consumption over the World

3

1.3

Transesterification of Triglycerides

5

2.1

Basic Scheme for Biodiesel Production.

12

2.2

Types of Biodiesel via Trasesterification

12

2.3

Prices of Potential Biodiesel Feedstock

23

2.4

Reaction Pathways of Biodiesel Production

24

2.5

Transesterification Reaction

24

2.6

Mechanism of the Base-catalyzed Transesterification of

25

Vegetable Oils

2.7

Mechanism of the Base-catalyzed Transesterification of Vegetable Oils for Heterogeneous Catalyst

26

xiv 2.8

Mechanism of the Base-catalyzed Transesterification of

27

Vegetable Oils for Ca-La Mixed Oxide Catalyst

2.9

Mechanism of the Esterification of Vegetable Oils

28

2.10

Mechanism of the Esterification of Vegetable Oils for

29

Heterogeneous Catalyst

2.11

Saponification of 1) Triglyceride and 2) FFA.

30

2.12

Hydrolysis of 1) Triglyceride and 2) FAME

30

2.13

Transesterification mechanism with presence CaO

32

3.1

Research Methodology Approach

45

3.2

GC chromatograph analysis of WCPO sample

47

3.3

Catalyst Preparation Process

49

3.4

Instruments for Catalyst Characterization; a) XRD and b)

50

FESEM

3.5

Instruments for Catalyst Characterization; a) TPDRO and b)

50

Quantachrome Autosorb-1

3.6

Schematic Diagram of Batch Reactor

53

3.7

Biodiesel Production Flow Chart

53

3.8

Side view of the reactor

54

3.9

Scheme Flow Sheet of PBR Process

55

xv 3.10

Transesterification Reaction in Packed Bed Reactor.

56

3.11

Agilent Technologies 6890N GC-MS

57

4.1

XRD Pattern of Catalyst a) ZrO2 and b) ZrO2, c) Mg /ZrO2,

61

d) Ca /ZrO2, e) Sr/ZrO2, f) Ba/ZrO2 after Calcinations at 650oC in 5h.

4.2

64

FESEM Monograph of a)ZrO2 b)Ca/ZrO2 c)Mg/ZrO2 d)Sr/ZrO2 e)Ba/ZrO2

4.3

CO2-TPD Profiles for Modified Zirconia Catalyst

66

4.4

NH3-TPD Profiles for Modified Zirconia Catalyst

68

4.5

Catalytic Activity of Modified Catalyst at 3wt% Catalyst

71

o

Loading, 6:1 Methanol to Oil Molar Ratio, 5hr and 60 C.

4.6

Possible Chemical Reaction Path in Biodiesel Production

72

4.7

Effect of Total Basicity and Acidity of Catalyst on Catalytic

74

Activity at 3wt% Catalyst Loading, 6:1 Methanol to Oil Molar Ratio, 5hr And 60oC.

4.8

Possible Mechanism of Simultaneous Esterification and

76

Transesterification Reaction

4.9

Effect of Molar Ratio of Methanol to Oil on ME yield at

78

o

3wt%, T=120 C

4.10

Effect of Catalyst Loading on ME Yield at T=120oC,30:1 Methanol-oil Ratio.

79

xvi 4.11

Effect of Reaction Temperature on ME yield at 3wt%, 30:1

79

Methanol-oil Ratio.

4.12

Flow of RSM Study

80

4.13

Parity Plot for a) ME Yield and b) FFA Conversion

86

4.14

Pareto Chart of ME Yield and FFA Conversion

87

4.15

Response Surface Plot of the Combine Methanol-oil Ratio

89

and Catalyst Loading on a) ME Yield and b) FFA conversion at 120oC for 3hr.

4.16

Response Surface Plot of the Combine Methanol-oil Ratio

90

and Reaction Time on a) ME Yield and b) FFA Conversion at 3wt% of Sr/ZrO2 and 120oC.

4.17

Response Surface Plot of the Combine Methanol-oil Ratio

92

and Reaction Temperature on a) ME Yield and b) FFA Conversion at 3wt% of Sr/ZrO2 for 3hr.

4.18

Response Surface Plot of the Combine Reaction Time and

93

Catalyst Loading on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar ratio and 120oC

4.19

Response Surface Plot of the Combine Reaction

94

Temperature and Catalyst Loading on a) ME Yield and b) Conversion at 30:1 Methanol to Oil Molar ratio for 3hr.

4.20

Response Surface Plot of the Combine Reaction Time and Reaction Temperature on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar ratio and 3wt% of Sr/ZrO2

95

xvii 4.21

Parity Plot for a) ME Yield and b) FFA Conversion on

100

Continuous Biodiesel Production.

4.22

Pareto Chart of a) ME Yield and b) FFA Conversion

102

4.23

Response Surface Plot of the Combined Methanol-oil Ratio

105

and Reaction Temperature on a) ME Yield and b) FFA Conversion at 0.79 g oil g cat-1h-1.

4.24

Response Surface Plot of the Combine Methanol-oil Ratio

106

and Reaction Time on ME Yield at 125oC

4.25

Response Surface Plot of the Combine Reaction Time and

107

Reaction Temperature on ME Yield at 20:1 Methanol-oil Molar Ratio.

4.26

ME Yield of Biodiesel Production from WCPO at 27:1

110

o

Methanol-oil Molar Ratio, 181 min, 153 C.

4.27

The Final Product Mixture Settle overnight for Batch (left)

111

and Continuous (right) at their Optimum Condition.

4.28

WCPO (left) and ME (right)

111

4.29

GC Chromatograph Analysis of Upper Layer Product (ME)

113

LIST OF FIGURES

FIGURE NO

1.1

TITLE

Transportation Diesel Oil Consumption for Asia Country

PAGE

2

(including Middle East)

1.2

Transportation Diesel Oil Consumption over the World

3

1.3

Transesterification of Triglycerides

5

2.1

Basic Scheme for Biodiesel Production.

12

2.2

Types of Biodiesel via Trasesterification

12

2.3

Prices of Potential Biodiesel Feedstock

23

2.4

Reaction Pathways of Biodiesel Production

24

2.5

Transesterification Reaction

24

2.6

Mechanism of the Base-catalyzed Transesterification of

25

Vegetable Oils

2.7

Mechanism of the Base-catalyzed Transesterification of Vegetable Oils for Heterogeneous Catalyst

26

xiv 2.8

Mechanism of the Base-catalyzed Transesterification of

27

Vegetable Oils for Ca-La Mixed Oxide Catalyst

2.9

Mechanism of the Esterification of Vegetable Oils

28

2.10

Mechanism of the Esterification of Vegetable Oils for

29

Heterogeneous Catalyst

2.11

Saponification of 1) Triglyceride and 2) FFA.

30

2.12

Hydrolysis of 1) Triglyceride and 2) FAME

30

2.13

Transesterification mechanism with presence CaO

32

3.1

Research Methodology Approach

45

3.2

GC chromatograph analysis of WCPO sample

47

3.3

Catalyst Preparation Process

49

3.4

Instruments for Catalyst Characterization; a) XRD and b)

50

FESEM

3.5

Instruments for Catalyst Characterization; a) TPDRO and b)

50

Quantachrome Autosorb-1

3.6

Schematic Diagram of Batch Reactor

53

3.7

Biodiesel Production Flow Chart

53

3.8

Side view of the reactor

54

3.9

Scheme Flow Sheet of PBR Process

55

xv 3.10

Transesterification Reaction in Packed Bed Reactor.

56

3.11

Agilent Technologies 6890N GC-MS

57

4.1

XRD Pattern of Catalyst a) ZrO2 and b) ZrO2, c) Mg /ZrO2,

61

d) Ca /ZrO2, e) Sr/ZrO2, f) Ba/ZrO2 after Calcinations at 650oC in 5h.

4.2

FESEM Monograph of a)ZrO2 b)Ca/ZrO2 c)Mg/ZrO2

64

d)Sr/ZrO2 e)Ba/ZrO2

4.3

CO2-TPD Profiles for Modified Zirconia Catalyst

66

4.4

NH3-TPD Profiles for Modified Zirconia Catalyst

68

4.5

Catalytic Activity of Modified Catalyst at 3wt% Catalyst

71

Loading, 6:1 Methanol to Oil Molar Ratio, 5hr and 60oC.

4.6

Possible Chemical Reaction Path in Biodiesel Production

72

4.7

Effect of Total Basicity and Acidity of Catalyst on Catalytic

74

Activity at 3wt% Catalyst Loading, 6:1 Methanol to Oil Molar Ratio, 5hr And 60oC.

4.8

Possible Mechanism of Simultaneous Esterification and

76

Transesterification Reaction

4.9

Effect of Molar Ratio of Methanol to Oil on ME yield at

78

o

3wt%, T=120 C

4.10

Effect of Catalyst Loading on ME Yield at T=120oC,30:1 Methanol-oil Ratio.

79

xvi 4.11

Effect of Reaction Temperature on ME yield at 3wt%, 30:1

79

Methanol-oil Ratio.

4.12

Flow of RSM Study

80

4.13

Parity Plot for a) ME Yield and b) FFA Conversion

86

4.14

Pareto Chart of ME Yield and FFA Conversion

87

4.15

Response Surface Plot of the Combine Methanol-oil Ratio

89

and Catalyst Loading on a) ME Yield and b) FFA conversion at 120oC for 3hr.

4.16

Response Surface Plot of the Combine Methanol-oil Ratio

90

and Reaction Time on a) ME Yield and b) FFA Conversion at 3wt% of Sr/ZrO2 and 120oC.

4.17

Response Surface Plot of the Combine Methanol-oil Ratio

92

and Reaction Temperature on a) ME Yield and b) FFA Conversion at 3wt% of Sr/ZrO2 for 3hr.

4.18

Response Surface Plot of the Combine Reaction Time and

93

Catalyst Loading on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar ratio and 120oC

4.19

Response Surface Plot of the Combine Reaction

94

Temperature and Catalyst Loading on a) ME Yield and b) Conversion at 30:1 Methanol to Oil Molar ratio for 3hr.

4.20

Response Surface Plot of the Combine Reaction Time and Reaction Temperature on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar ratio and 3wt% of Sr/ZrO2

95

xvii 4.21

Parity Plot for a) ME Yield and b) FFA Conversion on

100

Continuous Biodiesel Production.

4.22

Pareto Chart of a) ME Yield and b) FFA Conversion

102

4.23

Response Surface Plot of the Combined Methanol-oil Ratio

105

and Reaction Temperature on a) ME Yield and b) FFA Conversion at 0.79 g oil g cat-1h-1.

4.24

Response Surface Plot of the Combine Methanol-oil Ratio

106

and Reaction Time on ME Yield at 125oC

4.25

Response Surface Plot of the Combine Reaction Time and

107

Reaction Temperature on ME Yield at 20:1 Methanol-oil Molar Ratio.

4.26

ME Yield of Biodiesel Production from WCPO at 27:1

110

o

Methanol-oil Molar Ratio, 181 min, 153 C.

4.27

The Final Product Mixture Settle overnight for Batch (left)

111

and Continuous (right) at their Optimum Condition.

4.28

WCPO (left) and ME (right)

111

4.29

GC Chromatograph Analysis of Upper Layer Product (ME)

113

LIST OF APPENDICES

APPENDIX

TITLE

PAGE

A

Example calculation for ME determination

129

B

Calculation of crystallite size of zirconia

130

C

Temperature Programmed Desorption (TPD) flowsheet

132

D

Response surface methodology

137

E

Publication

142

CHAPTER 1

INTRODUCTION

1.1

Background of Research

The depletion of world fossil fuel reserve is due to the increasing energy consumption demand each year. The energy demands also contribute to the increment of the oil prices. In 1990, Malaysia consumed about 2015 million liters diesel oil in transportation sector, and the consumption increased about 5432 million liter in 2003. Figure 1.1 exhibits the diesel consumption in transportation sector for each country in Asia (including Middle East) for 1990, 2000 and 2003.China consumed the highest diesel oil in Asia, followed by Japan in 2003, while Malaysia was on the eighth places (Earthtrends website, 2008).

2

Diesel oil consumption (million liter)

40000

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Figure 1. 1: Transportation Diesel Oil Consumption for Asia Country (including Middle East) (Source: Earthtrends website, 2008)

As shown in Figure 1.2, developed countries consumed higher diesel fuel than high income countries. In 2008, Asia was at the fifth place. Since the diesel fossil fuel is consumed faster than it is formed, the fossil fuel is a limited source (Srinegar, 2005). The diesel fossil fuel is formed from non-renewable sources where they cannot be reproduced. The fuel needs about 100 years to form. Therefore, the replacement for the energy sources is essential because of the increasing energy demand.

3

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Figure 1. 2: Transportation Diesel Oil Consumption over the World (Source: Earthtrends website, 2008)

Over the last decades, significant amounts of research have been carried out in order to find new renewable and sustainable energy sources as an alternative petrol fuels. From the research, they found that the vegetable oils or animal fats have potential as an alternative fuel (Knothe, 2005b). The first demonstration of vegetable oils (VOs) as a fuel was done at Paris Exposition in 1900. During the exposition, a diesel engine, which was designed for petroleum by the French Otto Company, was run wholly using peanut (arachide) oils without any modification. Although without modification in engine, the engine worked smoothly until none of onlookers was aware over the incident (Knothe, 2005b). After that, many researchers and scientists studied the application of VOs as an alternative fuel for diesel engine such as Rudolf Diesel, St. Petersburgh, Walton and many more. Rudolf Diesel (1858-1953) is the one who invented motor engine that bears his name (Knothe, 2005b).

4 Nowadays, a fuel from vegetable oils is well-known as biodiesel. From ASTM, biodiesel was defined as mono alkyl ester of long fatty chain fatty acids (FAs), which was derived from a renewable lipid feedstock. It was a promising renewable source well before the energy crisis in 1970s and early 1980s. Knothe (2005b) reported that the first introduction of the term ‘Biodiesel’ in technical writing was in a Chinese paper published in 1988. The next paper using this term appeared in 1991 and from there, the used of word of ‘biodiesel’ in the literature expanded exponentially until now.

Biodiesel had become a focal point for alternative diesel fuel since it has been proved as an environmental friendly fuel due to its free of sulfur and aromatic compound by many researchers (Canakci, 2007, Marchetti et al., 2007, Nie et al., 2006, Zullaikah et al., 2005). The characteristics of biodiesel are similar to diesel fossil fuel. It has a proper viscosity, boiling point and higher cetane number. Therefore, it releases a better exhaust emission. Biodiesel also has a high flash point, which leads to a safer handling and storage (Knothe, 2005a). Peterson and Möller (2005) also reported biodiesel is biodegradable and non-toxic. In addition, biodiesel is considered as a renewable fuel since it is derived from renewable domestic resources, thus dependency on preserving petroleum could be reduced.

Biodiesel can be produced from vegetable oils or animal fats by subjected to a chemical reaction termed as transesterification. In transesterification, vegetable oils or animal fats is reacted in the presence of the catalyst with an alcohol to give the corresponding alkyl esters of the fatty acid (FA) mixture that is found in the parent vegetable oils or animal fats.

5

Figure 1. 3: Transesterification esterification Reaction of Triglycerides

Generally, the most common common way to produce biodiesel is by alkaline transesterification. Triglycerides are the main components of vegetable oil which consist of three long chain of fatty acids esterified to a glycerol backbone. When triglycerides react with an alcohol, the three fatty acid chains chain are released from the glycerol skeleton and combined combine with the alcohol to yield fatty acid methyl esters (FAME). Glycerol is i produced as a byproduct in the process. The reaction of transesterifications could be enhanced with the presence of alkaline catalysts catalyst such as potassium hydroxide, sodium hydroxide, and sodium methoxide or sodium ethoxide. The important reaction action parameters for for the transesterifications are ratio of alcohol to vegetable oil, temperature, amount of catalyst loading, rate of agitation and amount of water and FFA present in reaction mixture. Instead of ethanol, methanol can also be used to produce ce alkyl ester from f vegetable oils due to the low price of methanol. methanol However the use of different alcohols will bring about a few differences regarding regard to the kinetics of reaction. Therefore, the selection of the alcohol was based on cost and performance consideration onsideration (Zhang et al., 2003).

Instead of alkaline transesterification, biodiesel could also be produced from acidic transesterification, enzymatic transesterification or supercritical methanol. However, Marchetti et al. (2007) reviewed that the performancee of these methods was not as well as alkaline transestrification. The acid transesterification needs need a long reaction time and excess methanol, while enzymatic transesterification is a very expensive method due to the cost of lipase. Meanwhile, supercritical supercritic methanol

6 required high energy consumption. Thus, alkaline transesterification was the best method for biodiesel production.

However, the ultimate challenge to reduce the cost of production is feedstock selection. The source of biodiesel usually depends on the crops amenable to the regional climate. In United States, soybean oil is the most common biodiesel feedstocks. While, in Europe and tropical countries such as Malaysia, the rapeseed (Canola) oil and palm oil are the source for biodiesel, respectively (Zullaikah et al., 2005). Gui et al. (2008) reported that, 84% of the world biodiesel production was from rapeseed oil followed by sunflower oil (13%), palm oil (1%), soybean and 2% from others. It seemed that edible oil was widely used as biodiesel sources. This phenomenon will bring imbalance to the food supply and demand market besides deforestation and destruction of ecosystem problems. Thus, the researchers need to tune their mind to find up other alternative feedstocks for biodiesel such as nonedible oil or waste edible oil.

The biodiesel had been well established via base transesterification of various refined vegetable oils in methanol solvent with presence of potassium hydroxide or sodium hydroxide as catalyst. But, the process had several drawbacks such as high energy and methanol consumption, difficulty glycerol recovery and a large amount of alkaline waste water produced (Halim et al., 2009). Meanwhile, the cost of production increase due to the cost of feedstock. However, the waste edible oil or non-edible oil can replace the refine vegetable oil. Thus, the ultimate challenge still lies on the development of catalyst and transesterification process to improve the biodiesel yield, quality and the process. A stable and high basicity catalyst is needed in order to convert free fatty acid (FFA) and triglyceride in oil to achieve high conversion and yield in the transesterification processes. Moreover, the continuous process is promising for the large scale production.

7 1.2

Statement of Problem

Replacing refined vegetable oil with non-edible oil such as waste cooking palm oil (WCPO) might reduce the yield of biodiesel production due to high level of FFA and water presence in WCPO. The FFA existence leads to a soap formation since FFA would react with a homogeneous alkaline catalyst. Subsequently, the post treatment process which is washing step will be difficult and large amount of alkaline waste water will be discharged. In order to overcome the crisis, the development of heterogeneous catalyst for biodiesel production is a promising method since the heterogeneous catalyst can be filtered out.

However, the presence of FFA still causes same problem. The FFA is more reactive with the presence of high acidity catalyst via esterification reaction while, triglyceride reacts better with the presence of high basicity catalyst. Some of the researchers proposed two-step catalyzed processes to overcome the problem but, the process required more equipment. Thus this has become a challenge to develop a new heterogeneous catalyst with both high basicity and acidity sites to promote both reactions at the same time.

In addition, a continuous process is more reliable for a large production than batch process basically. The continuous transesterification process is more effective using a packed (fixed) bed reactor (PBR) than a continuous stir tank reactor (CSTR). PBR would lower the cost by simplifying the product separation, shorter reaction time and greater production capacity (Narasimharao et al., 2007).

The newly catalyst and continuous process will be valuable for biodiesel production from edible oil waste. Both of them are able to convert free fatty acid and triglyceride, thus, improve the production process and reduce the cost of biodiesel production. Reprocess of the WCPO also will provide an economically viable solution for waste management.

8 1.3

Hypothesis of Research

The hypothesis of the research is that an alkaline-modified heterogeneous catalyst will have high acidity and basicity in order to perform very well in biodiesel production from WCPO which have a high FFA.

1.4

Objectives of Research

The objectives of research are:

i.

To develop and characterize the alkaline-modified zirconia catalyst

ii.

To screen the modified catalyst in batch processes.

iii.

To investigate the performance of the most potential alkaline modified zirconia catalyst for biodiesel production in batch and continuous processes.

1.5

Scope of Research

The catalyst was produced by an impregnation of aqueous solution alkaline nitrate salt and zirconia as a support. The alkaline nitrate salts are limited to a group number 2 in a periodic table. The physical and chemical properties of the catalyst were characterized using BET, XRD, FESEM, NH3-TPD and CO2-TPD to study the properties of the catalyst.

9 The alkaline-modified zirconia catalyst was screening out at the same condition in batch process in order to find the most potential catalyst for biodiesel production. Then, the process variables such as methanol-oil molar ratio, reaction time and catalyst loading were determined with presence of the most potential catalyst.

Next, the performance of the most potential catalyst was carried out in a methanolysis batch process, at a laboratory scale. Then, the relationship of process variables (i.e:reaction temperature, molar ratio, and catalyst loading) were analyzed using STATISTICA Statsoft software to obtain optimum condition. The important properties of product (FAME) were characterized and compared to FAME characteristic of ASTM 6751-02.

In addition, the performance of the most potential catalyst was carried out in a continuous process as well. The relationship of process variables such as reaction temperature, reaction time and methanol to oil ratio were studied and the recommended optimum condition for both processes was found using a STATISTICA Statsoft software. Subsequently, the important properties of product (FAME) were characterized and compared to FAME characteristic of ASTM 675102.

1.6

Significant of Research

The research found the alternative catalyst and method for biodiesel production from a low cost feedstock with high FFA level. The research also comes up with the prototype of a packed bed reactor system which helping for ease of separation of the desired products and regeneration of the heterogeneous catalyst.

CHAPTER 2

LITERATURE REVIEW

2.1

Biodiesel Production Process

Since hundred years ago, researchers all over the world have studied the potential of vegetable oil as a fuel. It was started by Rudolf Diesel who was invented the diesel engine. The number of the studies increased year by year due to fuel demand and environmental problem. Recently, the biodiesel plants have been established around the world with various refined vegetable oils as a feedstock. Different methods for biodiesel production from different sources of fuel had been developed by researchers and scientists since different sources of fuel have different characteristic.

Based on Ma and Hanna (1999), the biodiesel can be carried out by four ways; direct use or blending, thermal cracking (Pyrolysis), microemulsion, and transesterification. Direct use of vegetable oils and/or the use of blends of the oils had generally been considered to be unsatisfactory and impractical for both direct and indirect diesel engines. The high viscosity, acid composition, free fatty acid content, as well as gum formation in the vegetable oil due to oxidation and polymerization during storage and combustion, carbon deposits and lubricating oil

11 thickening are obvious problems in this method. Meanwhile, a thermal cracking and pyrolysis method produces a fuel that is chemically similar to petroleum-derived gasoline and diesel fuel. The removal of oxygen during the thermal processing also removes any environmental benefits of using an oxygenated fuel. It produces some low value materials and, sometimes, more gasoline than diesel fuel (Ma and Hanna, 1999).

On the other hand, all microemulsions with butanol, hexanol and octanol met the maximum viscosity requirement for No. 2 diesel. In a 200 h laboratory screening endurance test, no significant deteriorations in performance were observed, but irregular injector needle sticking, heavy carbon deposits, incomplete combustion and an increase of lubricating oil viscosity were reported (Ma and Hanna, 1999). Transesterification is the preferably process used to make biodiesel fuel as it is defined in Europe and in the USA. The process has been widely used to make methyl esters for detergents and cosmetics manufactures (Ma and Hanna, 1999)

However, over of the process, transesterification of natural oils and fats was chosen as the best method due to an engine performance such as carbon deposit and engine durability. The purpose of the transesterification process is to lower down the viscosity of the oil or fat. The high viscosity of vegetable oils causes the problem to diesel engine such as carbon deposit in the engine and engine durability (Demirbas, 2008). In transesesterification process, viscosity of vegetable oil or fat reduces without affecting the heating value of the original fuels (Canakci, 2007). Figure 2.1 shows the basic scheme for biodiesel production.

Transesterification of vegetable oil to produce alkyl ester can be carried out with the presence of catalyst or without catalyst as shown in Figure 2.2. However, most of the researchers or scientists reported that higher yield of biodiesel was produced with the presence of catalyst.

12

Figure 2. 1 Basic Scheme for Biodiesel Production (Source:Sharma et al., 2008)

BIODIESEL PRODUCTION PROCESSES

WITH CATALYST





Base Catalyzed Transesterification Trans of the vegetable oil

WITHOUT CATALYST

Acid Catalyzed Transesterification

•Supercritical Supercritical Process

of the vegetable oil •

Lipase catalyzed transesterification trans



Esterification ( Pretreatment of FFA) and transesterification of the vegetable oil

Figure 2. 2 Types of Biodiesel Production via Transesterification

13 2.1.1

Base Catalyzed Transesterification

The base-catalyzed transesterification of vegetable oils proceeds faster than the acid-catalyzed reaction. Due to this reason, together with the fact that the alkaline catalysts are less corrosives than acidic compounds, industrial processes usually favor base catalysts, such as alkaline metal alkoxides (Demirbas, 2008) and hydroxides (Demirbas, 2008, Leung and Guo, 2006, Vicente et al., 1998) as well as sodium or potassium carbonates (Di Serio et al., 2005). Alkaline metal alkoxides (as CH3ONa for the methanolysis) were reported by Demirbas (2008) as the most active catalysts, since they give very high yields (> 98%) in short reaction times (30 min) even if they are applied at low molar concentrations (0.5 mol%). The author also stated that potassium methoxide is more active than sodium methoxide. However, sodium methoxide is more preferable since potassium methoxide has a high heat of reaction with methanol.

On the other hand, alkaline metal hydroxides (KOH and NaOH) are cheaper than metal alkoxides but less active(Leung and Guo, 2006). Nevertheless, they are a good alternative since they can give the same high conversions of vegetable oils just by increasing the catalyst concentration up to 1 or 2 mol%. Leung and Guo (2006) had studied the methanolysis of used frying oil, in the presence of methanol/oil molar ratio of 7.5:1 at 70 °C, reaction time 30 min. They had found the biodiesel yield reach to 85.3% with presence of 1.1wt% NaOH, while 86% for 1.5wt% KOH and 89 % for 1.3wt% CH3ONa.

Although base catalyzed tranesterification is effective to produce biodiesel, the process has several drawbacks such as high methanol consumption. A large excess of alcohol shifts the equilibrium to the products side and thus ensures total conversion to the esters. After completion of the transesterification reaction, the biodiesel phase is separated from the more dense glycerin phase by gravitational settling or centrifugation. However, an excessive amount of alcohol makes the recovery of the glycerol difficult, so that the ideal alcohol/oil ratio has to be

14 established empirically, considering each individual process (Furuta et al., 2004, Halim et al., 2009). The process also produce large amount of alkaline waste water. After the separation, the methyl esters, which still contain large amounts of residual alcohol, traces of dispersed glycerin and unreacted sodium hydroxide or soaps, are cleaned by a water wash. Remaining water and poorly water-soluble impurities, such as the unreacted feedstock or the mono- and diglycerides, are removed by further steps such as distillation or stripping. Therefore, the process requires high energy.

The base catalyzed transestrification process is sensitive to absence of water. Even if a water-free alcohol/oil mixture is used, some water is produced in the system by the reaction of the hydroxide with the alcohol. The presence of water gives rise to hydrolysis of some of the produced ester, with consequent soap formation. This undesirable hydrolysis of ester and saponification of FFA reaction reduces the ester yields and considerably makes the recovery of glycerol more difficult due to the formation of emulsions. Furthermore, the hydrolysis of methyl ester increased acidity of oil (Yan et al., 2009a)

2.1.2

Acid Catalyzed Transesterification

The acid catalyzed transesterification process is catalyzed by BrØnsted acids, which is well known as esterification processs. Preferably, a sulfonic and sulfuric acid is used as a catalyst in the process. These catalysts give very high yields in alkyl esters, but the reactions are slow (Demirbas, 2008). They require temperature above 100 °C and more than 3 h to reach a complete conversion. Biodiesel production by acid- catalyzed transestrification is the second conventional way of making biodiesel after base catalyzed transesterification. Freedman and Pryde work had been reviewed by Marchetti et al. (2007) where the methanolysis of soybean oil (at 65 °C) took 50hr to reach a complete conversion of the vegetable oil (> 99%), in the presence of 1 mol% of H2SO4, with an alcohol/oil molar ratio of 30:1, while the butanolysis (at 117

15 °C) and ethanolysis (at 78 °C), using the same quantities of catalyst and alcohol, took 3 and 18 h, respectively. Marchetti and Errazu (2008) then showed that the conversion of 30% of triglycerides was reached after 4h, at 45oC, 6:1 ethanol to oil ratio and 2.2wt% of catalyst.

Zhang et al. (2003) reported that the acid-catalyzed process using has proved to be technically feasible with less complexity than the alkali-catalyzed process. However, the process requires large amount of methanol and larger reactor size as well as larger distillation column. In addition, the equipment which made from stainless steel is required since it can tolerate to corrosive material (acid sulfuric).

2.1.3

Two-step Catalyzed Transesterification

Wang et al. (2007) had developed the two-step catalyzed process which used waste cooking oil (WCO) as feedstocks. The process involved acid catalyzed and based catalyzed. The FFA in WCO reacted with methanol by using ferric sulfat as an acid catalyst in the first step via esterification reaction. Then, un-reacted triglycerides from the first step were transesterified with methanol with the presence of KOH as a based catalyst in the second step. The conversion rate of FFA reached 97.22% when 2wt % of ferric sulfat with presence 10:1 methanol-oil molar ratio was reacted at 95oC for 4h. The final product with 97.02% yield of biodiesel, obtained after the unreacted triglyceride from first step reacted at 65oC, 1h and 6:1 methanol-oil molar ratio in second step.

Another research done by Zulaikkah et al. (2005) showed the methanolysis of rice bran oil with had high FFA level using two-step acid catalyzed process. The first step was carried out at 60oC for 2h. Then, the reaction product was used as the substrate for the second step which was carried out at 100oC. 96% of FAME content

16 was produced for total reaction time of 8h with two-step acid catalyzed process. On the other hand, the performance of two step base catalyzed process at room temperature was investigated by Çayli and Küsefoğlu (2008). They also found that two-step processes gave a better yield than the one step process. But, the process is more complex process and uses more equipments than one-step process (Zhang et al., 2003).

2.1.4

Lipase Catalyzed Transesterification

Although the enzyme-catalyzed transesterification processes are not yet commercially developed, recently lipase catalyzed transesterification

has been

reported as a promising method to produce biodiesel from low cost feedstocks like WCO which has high FFA level and water (Furuta et al., 2004, Halim et al., 2009, Nie et al., 2006, Yagiz et al., 2007). This is due to the ability of lipase enzyme to catalyze both transesterification and esterification reaction with no complex operation (Marchetti et al., 2007).

Most of the problems with both base and acid catalyzed transesterification processes could be overcome by using immobilized lipases. Immobilization of lipases on, mainly, water insoluble carriers, helps in their economic reuse and in the development of continuous bioprocesses. Immobilization also facilitates the separation of products, enhances lipase properties such as thermostability and activity in non-aqueous suitable support and technique of immobilization is important in the process (Knežević et al., 2004).

Yagiz et al. (2007) studied the comparison of immobilized lipase (LipozymeTL IM) on hydrotalcite and zeolites. Hydrotalcite was shown to be the best support material for lipase than zeolite. It produced 92.8% biodiesel yield after 105h at room

17 temperature. In same year, Royon et al.(2007) presented the performance of enzymatic-solvent system for biodiesel production from cotton seed oil. The methanolysis yield of 97% was observed after 24h at 50oC in the system. Gao et al. (2006) investigated the potential of macroporous resin as a support and studied the performance of the immobilize enzyme in low aqueous media. The study was carried out stepwise methanol addition. The conversion rate of 97.3% was obtained when crude enzyme/resin weight ratio was 1.92:1 and water content 15% at 40oC under pH 7.4. Halim et al. (2009) presented a statistical and experimental design to optimize packed bed height and substrate flow rate for a continuous packed bed reactor. The author also studied the effect of mass transfer in the packed bed reactor.

However, the immobilized lipase enzyme is sensitive to polar solvent such as methanol, water and glycerol (Ting et al., 2008). In order to overcome these problems, Ting et al. (2008) carried out the study on the combination of enzymatic and esterification reaction. The soybean oil has been hydrolyzed to convert triglyceride into FFA in the first step, and then the FFA was esterified with methanol in presence of acid catalyst such as sulfuric, hydrochloric, nitric, and phosphoric or acetic acid.

On the other hand, enzymatic system with co-solvent was explored by several researchers (Kamaruddin et al., 2008, Nie et al., 2006, Royon et al., 2007). The nonpolar solvent such as hexane and t-butanol were unable to strip any of water from the enzyme, and then the catalytic activity of enzyme was sustained.

The common parameters that had been studied such as solvent, temperature, pH, type of microorganism which generates the enzyme and etc, have been optimized in order to establish a suitable condition for an industrial application. However, the reaction yields as well as the reaction times are still unfavorable compared to the base-catalyzed reaction systems(Nie et al., 2006).

18 2.1.5

Supercritical Transesterification

Generally, at ambient conditions, triglycerides and FFA, known as relatively non-polar compounds, are not very soluble in methanol, a well-known polar compound. Therefore, when methanol is mixed with triglycerides or FFA in the absence of catalyst, the reaction system is essentially heterogeneous. Thus, two insoluble phases are formed, allowing very little contact between the triglyceride and methanol. The lack of intimate contact explains the long reaction times needed to produce biodiesel.

However, when the methanol is subjected to supercritical condition, there are numbers of unusual properties inhibited (Gerpen and Knothe, 2005). The methanol is no longer a distinct liquid or vapor phase, but rather in fluid phase (Schulte, 2007). In this phase, the thermophysical properties of methanol would changes. The mass diffusivity will increase while the viscosity will decrease. The density of methanol can be manipulated over a large range through relatively small changes in temperature and pressure. These properties allow the supercritical methanol to be used as a tunable solvent with superior mass transfer characteristic (Schulte, 2007). In addition, the polarity of methanol also will decrease. At the critical point, methanol will start behaves like a non-polar compound. Thus triglyceride or FFA can be completely dissolved in methanol and the rate of reaction can be dramatically improved. In the meantime, the methanol become functioning as an acid catalyst (Schulte, 2007).

A reaction temperature of 350 °C and a molar ratio of methanol to oil of 42 to 1 were considered to be the best condition. Since supercritical methanol has a hydrophobic nature with a lower dielectric constant, non-polar triglyceride can be well solvated with supercritical methanol since at the critical point, methanol starting to behave like non-polar and form a single phase oil/methanol mixture. Thus, the oil to methyl ester conversion rate was found to increase dramatically in the supercritical state of methanol (Saka and Kusdiana, 2001).

19 Moreover, Saka and Kusdiana (2001) investigated the transesterification reaction of rapeseed oil in supercritical methanol without using any catalyst. The non-catalytic supercritical alcohol transesterification reaction also has been studied by Demirbas (2008). He reported the conversion rises to 50-95% for the first 10 min. However, the presence of water accelerated formation of methyl ester. The author reported that without the catalyst, the conversion achieves 50-95% after 8 min and 60-90% after 1 min if the catalytic supercritical alcohol transesterification is used. Kusdiana and Saka (2004) discussed the effects of water on biodiesel fuel production by supercritical methanol treatment. Warabi et al. (2004) had studied the reactivity of triglycerides and FAs in various types of alcohol in supercritical alcohol transesterification process. The formation of methyl ester is depended on the length of alcohol for transesterification of triglyceride, while for esterification of FAs, the conversion did not depend on the alcohol types.

The advantage with supercritical methanol is that the 95% conversion of oil complete in 10 min of reaction time. Moreover, FFA presences in WCO could also be converted efficiently to methyl ester in supercritical methanol, and eventually increased the yield of methyl ester from WCO. In addition, because the process was non-catalytic, the purification of products after the transesterification reaction was much simpler and more environmentally friendly compared to the alkali-catalyzed method in which all the catalysts and saponified products had to be removed to obtain biodiesel fuel (van Kasteren and Nisworo, 2007). But, in the same time, higher molar ratio (40:1) is employed. The supercritical condition was based on the effect of relationship between pressure and temperature upon the thermophysical properties of the solvent, such as dielectric constant, viscosity, specific weight and polarity. There was a decrease in the dielectric constant of methanol in supercritical state (Sharma et al., 2008).

20 2.2

Potential Feedstock

In selecting the right process for biodiesel production, the main important part that needs to be considered is feedstock issue, since in biodiesel production process, types of feedstock are very significant because the cost of raw material will contribute to the higher cost of production (Marchetti et al., 2007, Narasimharao et al., 2007).

Biodiesel’s characteristics and performance as a fuel is depending on its composition, and the fuel composition has to be stringently monitored to avoid unfavorable impacts on the environment and engines. The final biodiesel composition depends on the composition of initial feedstock, as well as on the reaction conversions and process separation efficiencies. The thermo-physical properties of biodiesel depend upon factors such as chain length, branching, and degree of saturation of feedstocks Impurities in biodiesel, either due to sidereactions, un-reacted feedstock, or non-fatty acid constituents, may increase pollutants.

Biodiesel can be produced from any vegetable oil (such as rapeseed, soybeans, cottonseed, peanuts, corn, olives, sesame seeds, and so on) or animal fat. Oils and fats are primarily composed of triacylglycerols (TAGs) or triglycerides (TGs). TGs are a form of lipid comprised of three fatty acid molecules attached to a glycerol backbone. Oils and fats can also contain lesser amounts of diacylglycerols (DAGs), which contains one glycerol and two fatty acids, and monoacylglycerol (MAGs), which contains one glycerol and one fatty acid.

The chemical composition of biodiesel and its combustion properties depend on the composition of the feed used for manufacturing. Increasing the average chain length of fatty acids enable the production of biodiesel with a higher cetane number

21 that have been reported to correlate with lower NOx exhaust emissions (Knothe, 2005a).

The degree of unsaturation in a fatty acid molecule affects its reactivity. Saturated Fatty Acids (SFAs) contain no reactive double bonds; Monounsaturated Fatty Acids (MUFAs) contain one double bond, while Polyunsaturated Fatty Acids (PUFAs) contain two or more double bonds. Unsaturation in a fatty acid chain significantly lowers its cetane number (Knothe, 2005a) and increases NOx emissions. Moreover, unsaturation increases the tendency to undergo an oxidative degradation (rancidity), which may decrease the lubricity of biodiesel, and thus contribute to a gum formation in the engine.

Although the initial feedstock of biodiesel affects the quality of biodiesel, the feasibility of feedstock also needs to be considered. Commonly, the biodiesel feedstock is determined on the crops amenable to the regional climate. In the United States, soybean oil is the most preferable biodiesel feedstock, with rapeseed (canola) oil in Europe and, palm oil for tropical countries(Zullaikah et al., 2005). Gui et al. (2008) reported that about 84% of the world biodiesel production is met by rapeseed oil, sunflower oil (13%), palm oil (1%) and soybean oil and others (2%).

Since more than 95% of the biodiesel feedstock is from edible oil, there are many claims that a lot of problems may arise. By converting edible oils into biodiesel, food resources are actually being converted into automotive fuels. It is believed that a large-scale production of biodiesel from edible oils may bring a global imbalance to the food supply and demand market (Gui et al., 2008). Furthermore, the line between food and fuel economies is blurred as both fields are competing for the same oil resources. In other words, biodiesel competed with food industry for oil crop plantation. Cultivable land has been used to grow fuel instead of used to grow food. In reality, this trend was observed in a certain part of this world. There has been an extensive development oil crops plantation in order to fulfill the continuous increasing demand for biodiesel in the past few years. However, the

22 ending stocks of vegetable oils are continuously decreasing due to increasing production of biodiesel. Eventually, with the implementation of biodiesel as a substitute fuel for petroleum-derived diesel oil, this may lead to the depletion of edible-oil supply worldwide.

Besides the competition of fuel and food, biodiesel production from edible oil gives negative impact of on our planet especially deforestation and destruction of ecosystem. The growth of oil crop plantations for biodiesel production on a large scale has caused deforestation in countries such as Malaysia, Indonesia and Brazil since more and more forest has been cleared for plantation purposes. In order to overcome this devastating phenomenon, suggestions and research have been made to produce biodiesel by using alternative or greener oil resources such as non-edible oils. In India, nearly half a dozen states have set aside a total of 1.72 million hectares of land for Jatropha cultivation and small quantities of Jatropha biodiesel are already being sold to the public sector oil companies. In this context, the next question that comes in mind would be if the use of non-edible oil overcomes the short-comings of using edible oil. Or rather it just simply diverts the issue and not solving it completely as plantations for non-edible oils still requires large plantation land areas. Alternatively, waste from edible oil (WEO) can be used instead, but is it sufficient to meet the demand of biodiesel. Besides, numerous researches had been done to study the potential of WEO as feedstocks ((Canakci, 2007, Felizardo et al., 2006, Gui et al., 2008, Leung and Guo, 2006, Tsai et al., 2007, Wang et al., 2007). WEO such as waste cooking oil (WCO) can be classified as either yellow grease or brown grease based on FFA content in the oil. Yellow grease is defined as oils and fats that have FFA content less than 15% while in brown grease, the FFA level is more than 15%. Usually yellow grease can be collected from cooking establishment, food processing, and restaurant and fast food shops while yellow grease can be found in animal fats that is from meat packaging processing (Canakci, 2007). From him, the FFA content in WCO is usually in range 5% to 30%.

23 Figure 2.3 shows the price for biodiesel feedstock in October 2007. As can be seen, the price of yellow grease is lower than others refined vegetable oils. Therefore, the WEO or WCO is the better choice for biodiesel production.

Figure 2. 3: Prices of Potential Biodiesel Feedstock (October 2007)(Source:Schulte, 2007).

2.3 Reaction of Triglyceride in Biodiesel Production

Normally there are two main hydrocarbon compounds in vegetable oil. There are triglycerides or fats and FFA. These compounds would react to produce fatty acid alkyl ester (FAAE) via two main reactions; esterification and transesterification by introducing alkaline catalyst and suitable alcohol such as methanol. Besides, the un-desired reaction known as hydrolysis could lead the reaction at certain condition. Figure 2.4 shows the possible reaction pathways of the reaction in biodiesel production as been suggested by Yan et al. (2009a) and Kusdiana and Saka (2004).

24

Figure 2. 4: Reaction Pathways of Biodiesel Production (Source:Yan et al., 2009a)

2.3.1

Transesterification and Esterification Est

Transesterification and esterification are common reactions reaction for biodiesel production. Transesterification is a reaction of the ester group with alcohol (e.g.: methanol) in the presence of catalyst to produce another ester (fatty acid methyl ester) and a glycerol co-product. co While, esterification is a carboxylic acid group react with alcohol in the presence of catalyst to produce ester and water. (Figure 2.5)

Figure 2. 5: Transesterification Reaction

25 The overall process of transesterification is basically a sequential and reversible reaction (Ma and Hanna, 1999, Schuchardt, 1998). 1998). Diglycerides and monoglycerides are formed as intermediates where triglycerides are first reduced to diglycerides. Then, the diglycerides are subsequently reduced to monoglycerides followed by reduction of monoglyceride to fatty acid esters. The order of the reaction changess with the reaction reacti conditions (Ma and Hanna, 1999).

Figure 2. 6: Mechanism of the Base-catalyzed Base catalyzed Transesterification of Vegetable Oils (Source:Schuchardt, 1998)

he mechanism of transesterification According to Schuchardt et al. (1998), the reaction is shown as Figure 2.6. 2. The first step (Eq. 1) is the reaction of the base with the alcohol, producing an alkoxide and the protonated catalyst. The nucleophilic attack of the alkoxide at the carbonyl group of the triglyceride and generates a tetrahedral intermediate (Eq. 2) from which the alkyl ester and the corresponding anion of the diglyceride are formed (Eq. 3). The latter latter deprotonates the catalyst, thus regenerating the active species (Eq. 4), which is now, be able to react with a second molecule of the alcohol, and starting another catalytic cycle. Diglycerides and

26 monoglycerides are converted by the same mechanism to to a mixture of alkyl esters and glycerol.

On the other hand, Yan et al. (2009a) have suggested the mechanism of transesterification reaction with the presence of heterogeneous catalyst which contents Lewis basic site (Figure 2.7) based on the Eley-Rideal Rideal type of mechanism. mechanism The transesterification takes place between the adsorbed methanol and triglyceride. Methanol is adsorbed on the Lewis base site (B-) of the catalyst and forms oxygen anion. The nucleophilic attacks attack of alcohol to the esters and produces a tetrahedral intermediate. Then the hydroxyl group breaks and forms two kinds of ester.

Base catalyzed Transesterification of Vegetable Oils Figure 2. 7: Mechanism of the Base-catalyzed for Heterogeneous Catalyst (Source:Yan et al., 2009a).

Yan et al.(2009b) (2009b) also proposed a new possible mechanism for transestrificationn of triglyceride with methanol with the presence of Ca-La Ca mixed oxide catalyst (Figure 2.8). They reported that the methanol and triglycerides are

27 adsorbed on the two neighboring free catalytic sites. Methanol can absorb on both Bronsted and Lewis base sites of the catalyst. Then, the nucleophilic attacks the absorbed ester to form a tetrahedral intermediate. Thus, two kinds of ester form (FAME and diglyceride) after the -C-O- bond breaks.

Figure 2. 8: Mechanism of the Base-catalyzed Transesterification of Vegetable Oils for Ca-La Mixed Oxide Catalyst (Source:Yan et al., 2009b)

Meanwhile, mechanism of the esterification of vegetable oils which reported by Schuchardt et al. (1998), is shown in Figure 2.9. Monoglyceride is the starting material, and can be extended to di- and triglycerides. The protonation of the carbonyl group of the ester leads to the carbocation II which, after a nucleophilic attack of the alcohol, produces the tetrahedral intermediate III, which eliminates glycerol to form the new ester (IV) and regenerate the catalyst H+. According to this mechanism, carboxylic acids can be formed from reaction of the carbocation II with water present in the reaction mixture. This suggests that an acid-catalyzed

28 sterification should be carried out in the absence of water, in order to avoid the transesterification competitive formation of carboxylic acids which reduce the yields of alkyl esters.

Figure 2.9: Mechanism of the Esterification of Vegetable Oils O (Source:Schuchardt, 1998)

In addition, Yan et al. (2009a) also had suggested the mechanism of esterification (Figure 2.10). 2.10). The esterification takes place between the adsorbed fatty acids and free methanol. The interaction interaction of the carbonyl oxygen of fatty acid with the Lewis acidic site (L+) of the catalyst forms carbocation. The nucleophilic attack of alcohol to the carbocation and produces a tetrahedral intermediate. During esterification, the tetrahedral intermediate eliminates water molecule to form one mole of methyl ester.

29

Figure 2. 10: Mechanism of the Esterification of Vegetable Oils for Heterogeneous Catalyst (Yan et al.,, 2009a). 2009a)

2.3.2

Hydrolysis

The hydrolysis is a side reaction in biodiesel production. The reaction is take place because of water presence in alkaline transesterification process. The base hydrolysis of an ester is sometimes called a saponification tion (Figure 2.11). 2.11) The catalyst such as sodium odium hydroxide (NaOH) and potassium hydroxide (KOH) which are well established catalyst in biodiesel production. (Felizardo et al.,, 2006, Phan and Phan, 2008, Vicente et al., al. 1998) might lead to the saponification in the process. The triglyceride reacted to sodium hydroxide with the presence of water to produce glycerol and a mixture of of salts of the long chain carboxylic acids or supposed to be soap. The reaction is the way most of soaps are manufactured (Solomons and Fryhle,

30 transesterification three steps of washing are needed 1998). In conventional alkaline transesterification, for purification of crude biodiesel process. The process produced produce large amount waste water and soap since the crude biodiesel contained contained alkaline catalyst. The soap production in biodiesel process affected affect to the production of biodiesel. It would w reduce the yield of FAME. Therefore, the reaction needs to be avoided avoid in biodiesel reaction.

(1)

(2)

Figure 2. 11: Saponification of 1) Triglyceride and 2) FFA. FFA

(1)

(2)

Figure 2. 12: Hydrolysis of 1) Triglyceride and 2) FAME(Yan (Yan et al., 2009a).

31 On the other hand, the acid hydrolysis of triglyceride and FAME (Figure 2.12) produces a FFA with the presence of acid catalyst and water. The hydrolysis of FAME is a backward acid catalyzed esterification of carboxylic acid reaction (Solomons and Fryhle, 1998). This can be avoided by utilizing the excess of alcohol. Meantime, the hydrolysis of triglyceride can be avoided in biodiesel production by employing the excess methanol at higher reaction temperature to shift the equilibrium to the products side. However, Kusdiana and Saka (2004) showed the presence of hydrolysis reaction gave an advantage in supercritical methanol since the esterification became faster at higher temperature.

2.4 Heterogeneous Catalyst in Transesterification

The heterogeneous catalyst is more preferable than the homogeneous catalyst since it can be easily separated from the final product by filtration and prevents the consumption of large volume of water. Besides, the filtered solid can be regenerated and reused. Furthermore, some of heterogeneous catalysts have the ability to simultaneously catalyze transesterification and esterification reaction. Thus, the heterogeneous catalyst has been widely studied by using high FFA feedstocks. The heterogeneous catalysts that commonly used by researchers include alkaline earth oxides, zeolites, hydrotalcites and etc.

2.4.1

Metal Oxide

The application of a heterogeneous catalyst, such as metal oxide, mixed metal oxide and modified metal oxide have been studied aggressively by researchers (Granados et al., 2007, Kim et al., 2004, Xie et al., 2006, Yan et al., 2009a). CaO had been tested by Granados et al. (2007) for its feasibility. The experiments

32 confirmed that CaO could be used as a catalyst for the the transesterification reaction without significant deactivation up to eight runs with a significant amount of CaO. After a year, Kouzu et al. (2008) had proposed a mechanism of transesterification of triglyceride with methanol; using CaO (Figure ( 2.13). ). On the other hands, Liu et al.(2007) had studied the performance of strontium oxide (SrO) as a solid base catalyst for biodiesel production from soybean oil. The biodiesel yield exceeds to 95% within 30 min at 65oC, 12:1 methanol-oil oil molar ratio and presence of 3wt % of SrO. SrO showed the excellent catalytic activity and stability due to its strong basicity and long catalyst lifetime.

Figure 2. 13: Transesterification Transeste mechanism with presence CaO (Source:Kouzu et al., 2008)

33 2.4.2

Transition Metal Oxide

Beside alkaline metal oxide group, the researchers also paying attention to the transition metal oxide such as zinc oxide (ZnO) and zirconia(ZrO2). The transition metal oxides have unique properties. They have amphoteric nature which could be either acid catalyst or base catalyst if the catalyst is well pre-treated. The catalyst made from these metals is also stabile at high temperature.

The methanolysis of soybean oil with presence of ZnO modified with alkali earth metals as a catalyst had been carried out by Yang and Xie (2007). They studied the catalytic activity of these catalysts in transesterification. The catalytic activity of the catalyst showed a correlation with their corresponding basic properties. ZnO loaded with 2.5mmol Sr(NO3)2/g, followed by calcination at 873K for 5h, by using this catalyst the conversion of triglyceride rise to 94.7% with the presence of 5wt% catalyst and 1:12 oil-methanol molar ratio at 65oC after 5h.

Beside ZnO, alumina also has showed good performance as a support. Kim et al. (2004) developed Na/NaOH/γ-Al2O3 as a base heterogeneous catalyst. The catalyst was found to have a higher basicity and gave a satistified yield of FAME at 60oC for 2h with the presence of 9:1 methanol-oil ratio and n-hexane as co-solvent. On the other hand, sodium alumina also had been studied by Arzamendi et al.(2007). Zeolite was also investigated since it made a good support for many catalysts in many processes. Furthermore, Suppes et al.(2004) reported that the performance of Zeolite-X was excellent at high temperature (140oC). Based on a study by Noiroj et al. (2009), KOH/Al2O3 is more reactive than KOH/NaY.

34 2.4.3

Modified Zircornia

The potential of various types of solid acid and base catalyst had been carried out by Jitputti et al. (2006). They investigated six types of heterogeneous catalysts ZrO2, ZnO, SO42-/SnO2, SO42-/ZrO2, KNO3/KL zeolite and KNO3/ZrO2. These catalysts had shown the potential to be used as heterogeneous catalysts for the transesterification. However based on methyl ester yield, SO42-/ZrO2 gave the highest and ZrO2 the lowest yield compared to others. The reaction was carried out at 200oC, 6:1 methanol-oil molar ratio, and 3wt% catalyst.

On the other hand, López et al. (2007) had studied the effect of calcination temperature of tungstated zirconia (WZ) in transesterification and esterification reaction since the calcination temperature affect the physicochemical properties, such as the crystalline structure and molecular structure of the metal oxide over layer, acid site density and strength. From the study, they found that 800oC was an optimum calcination temperature for WZ.

Furthermore, Furuta et al. (2006) had tested the amorphous zirconia solid catalysts, TiO2/ZrO2 (11 wt% Ti) and Al2O3/ZrO2 (2.6 wt% of Al) and reported more than 95% conversion. The reason for this was the amphoteric nature of the zirconia. But, the temperature required was quite high i.e. 448–473 K. Furuta et al. (2004) also tested a mixed solid super acid, sulfated tin oxide (STO), sulfated zirconium-alumina (SZA) and tungstated zirconia-alumina (WZA). Although STO showed the highest acid strength, WZA was more suitable for the process since WZA activity was good for esterification as well as the transesterification. These catalysts were also active at high temperature (200-300oC). Also, the comparison of tungstated zirconia (WZ) and sulfated zirconia (SZ) has been investigated by Park et al.(2008). Park and friends had concluded that WZ were found to be effective in esterification and transesterification of FFA and triglycerides.

35 2.5.4

Solid Acid Catalyst

The potential of solid acid was also studied by Peng et al. (2008). They have investigated the potential of SO42-/TiO2-SiO2 as a solid acid to esterify the triglyceride into their corresponding methyl ester. SO42-/TiO2-SiO2 had a large specific surface area which ensured a good contact between the reactant and catalyst and pore diameter 10.8nm was big enough for reactant and product to pass through the channels. However, the catalyst also required high temperature (200oC). On the other hand, ion exchange resins were studied by Marchetti et al.(2007), ShibasakiKitakawa et al. (2007) and Özbay et al.(2008). The type of catalyst was limited since the cost is expensive.

2.4.4

Mixed Metal Oxide

Mixed metal oxide as a bifunctional catalyst was prepared by Yan et al. (2009a). They studied the performance of this mixed metal oxide catalyst on the transesterification, esterification and hydrolysis processes. Zn-La metal oxide was prepared by a co-precipitation of nitrate salt of zinc and lanthanum. The catalyst with 3:1 ratio of zinc to lanthanum showed the best catalytic activity since it had the highest basic and acid sites beside active on transestrification and esterification, and no hydrolysis activity. However, high temperature and a large amount of methanol were required to esterify the unrefined and waste oil with presence of Zn-La metal oxide catalysts.

Although many heterogeneous catalysts had been studied in previous researches, none of the catalysts had been used as a commercial catalyst in biodiesel production due to a leaching problem and stability of the catalyst. Therefore, the development of a new heterogeneous catalyst needs to be carried out in a future

36 research. Based on the previous studies, zirconia had a potential to be a good catalyst in the process due to redox properties of zirconia (Lotero et al., 2005, Wang et al., 2000).

2.5 Effect of Parameter over Biodiesel Production

The main factors affecting to transesterification are molar ratio of glycerides to alcohol, catalyst, reaction temperature and time and the contents of FFA and water in oils and fats. An excess of the alcohol favors the formation of the products. On the other hand, an excessive amount of alcohol makes the recovery of the glycerol difficult, so that the ideal alcohol/oil ratios need to be established empirically, considering each individual process. Leung and Guo (2006) reported that the methanol has a polar hydroxyl group which reacted as an emulsifier causing emulsification. Hence, a separation process of ester layer from the water layer becomes difficult.

The commonly accepted molar ratio of alcohol to glyceride is 6:1 for base catalysed transesterification. Acid catalysed esterification and supercritical alcohol transesterification require large amount of methanol. Veljkovic et al. (2006) used 18:1 molar ratio during acid esterification and 6:1 molar ratio during alkaline transesterification. Wang et al. (2006) reported that the conversion of WCO increased rapidly when methanol to oil molar ratio exceed to 16, but decreased when molar ratio exceed to 20.

The amount of catalyst can accelerate the reaction of transesterification at the right condition. The recommended amount of base used is between 0.1 and 1% w/w of oils and fats, while for acid are between 1-4% (Marchetti et al., 2007). However, an excess amount of catalyst used can cause side reaction known as saponification.

37 On the other hand, reaction temperature also would affect to the transesterification process. Normally the researchers maintained the reaction temperature at methanol boiling point (60oC) because temperature higher than this will evaporated the methanol and produces much lesser FAME yield. A study by Leung and Guo (2006) showed that temperature higher than 60oC had negative impact on the product yield of neat vegetable oil, but had a positive impact for waste vegetable oil. The high temperature is favorable to increase the solubility of oil in methanol and improve the oil to methanol contact. Besides, the higher reaction temperatures speed up the reaction and shorten the reaction time. The reaction is slow at the beginning for a short time and proceeds quickly and then slows down again. Base catalyzed transesterifications are basically finished within one hour.

Kusdiana and Saka (2004) observed that water could pose a greater negative effect than fatty acids in a conventional alkaline transesterification; hence the feedstock should be water free. However, the presence of water had negligible effect on the conversion when using lipase as a catalyst (Demirbas, 2008).

2.6 Continuous Process for Biodiesel Production

General process of biodiesel production is a batch process. Only a few studies were carried out using a continuous process by application of a packed bed reactor (PBR) (Furuta et al., 2004, Halim et al., 2009, Shibasaki-Kitakawa et al., 2007). Normally, the continuous process via PBR was carried out for supercritical, enzymatic or ion-exchange processes. Kusdiana and Saka (2004) and (Warabi et al., 2004) had studied the effect of various alcohol and the potential catalytic free condition for biodiesel production in flow-type supercritical biomass conversion systems which used tube reactor for continuous process. Besides, Shibaki-kitakawa et al. (2007) reported that the expanded bed reactor packed with the resin permitted the continuous production of methyl oleate (FAME) with high conversion.

38 On the other hand, Halim et al. (2009) had carried out the application of PBR with presence of C. antartica lipase enzyme for a continuous process of biodiesel. The PBR was used since the multiphase reaction solid-liquid, was involved in a heterogeneous catalyst. The PBR was employed also because it allowed reuse of the enzyme without the need of a prior separation, and able to handle substrates of low solubility by using large volumes containing low concentrations of substrate. Besides the ratio between substrate and enzyme was much lower in a PBR than in conventional batch reactors, and it resulted in higher reaction performance. Furthermore the PBR was suitable for a long-term and industrial scale production, since it was different from a stirred-tank reactor where enzymes granules would be susceptible to break because of the mechanical shear stress. In addition PBR system was more cost effective than batch operation (Halim et al., 2009).

In other study, Bournay et al. (2005) had carried out a new heterogeneous catalyst process which used two fixed bed reactors in series. The both reactors were fixed with a mixed oxide of zinc and aluminium. In addition, Furuta et al. (2004) had investigated the potential of amorphous zirconia catalyst for biodiesel production. They had synthesized biodiesel from soy bean in a fixed-bed continuous flow reactor.

2.7 Catalyst Characterization Method

The physical, chemical and structural properties of the catalysts were characterized via various techniques. Among the techniques that had been involved and regularly used for catalyst characterizations are X-ray powder diffraction measurement (XRD), BET measurement, nitrogen adsorption isotherm (NA), themperature programmed desorption (TPD) and Pyridine IR-spectroscopy (Py-IR).

39 XRD method was employed to characterize and identify the internal structure (crystallite), bulk phase, and composition of catalyst in crystalline phase (Noiroj et al., 2009). The surface area and pore size of catalyst were determined by the Brunauner-Emmet-Teller (BET) measurement. Meanwhile, NA is widely used to determine the total surface area and characterize the texture structure of solid porous in NA isotherm. Both NA analysis and BET equation can also be used for total surface area determination. Using pyridine adsorption as a probe molecule is a useful technique to identify the acid sites of solid by monitoring it with IR spectroscopy. Pyridine constitutes with Bronsted and Lewis acid centers of various surface complex, which display the IR-spectra peaks at different wavelengths. Appearences of a band at 1450 cm-1 is assigned to the vibration mode of pyridine adsorbed onto lewis acid sites. This provides information about Lewis acid sites. Appearance of a band at 1540 cm-1 is due to pyridine ions formed at the expense of bronsted acid sites. Both complexes yield at band 1490 cm-1 that attributed to both Lewis and Bronsted acid sites.

X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), was used to determine the quantitative atomic composition and chemistry. It is a surface analysis technique with a sampling volume that extends from the surface to a depth of approximately 50-70 Angstroms. Alternatively, XPS could be utilized for sputter depth profiling to characterize thin films by quantifying matrix-level elements as a function of depth. XPS is an elemental analysis technique. Meanwhile, Temperature-programmed desorption (TPD) is normally used to calculate the acidity of the solid catalyst. Useful information on both concentration and strength of sites can be provided by TPD technique to identify the acidity and basicity of catalyst. Table 2.1 summarizes the previous study on catalyst characterization.

Table 2. 1: Summarize of instrument for catalyst characterization Instrument

Test

References

X-ray powder diffraction (XRD)

• To characterize and identify the internal structure,

(Di Serio et al., 2006, Granados et al., 2007, Juan

crystallinity, bulk phase, and composition in

et al., 2007, Noiroj et al., 2009, Xie et al., 2006,

crystalline phase (dispersion of promoter on

Yan et al., 2009a)

support) of catalyst X-ray Photoelectron spectra (XPS)

• To determine the state of the surface of the catalyst

(Granados et al., 2007, Yan et al., 2009a)

X-ray fluorescence (XRF)

• To determine the bulk composition of catalyst.

(Noiroj et al., 2009)

spectroscopy

• To determine the metal ion content

Brunauner-Emmet-Teller (BET)

• To determine surface area and pore size of catalyst

(Di Serio et al., 2006, Juan et al., 2007, Noiroj et al., 2009, Yan et al., 2009a)

Scanning electron microscope (SEM) Transmission electron microscopy

• To study the morphology of catalyst such as size

(Xie et al., 2006, Yan et al., 2009a)

and structure. • To study structure of catalyst

(Juan et al., 2007)

• To observe desorbed molecules from the surface

(Noiroj et al., 2009)

(TEM) Temperature-programmeddesorption (TPD)m

when surface temperature is increased • The interaction of molecules in catalyst.

41

Table 2. 1: Summarize of instrument for catalyst characterization (continue) Instrument

Test

References

CO2-TPD

• To determine the basic properties.

(Di Serio et al., 2006, Noiroj et al., 2009)

N2-adsorption/desorption isotherm

• To determine textural properties such as pore

(Di Serio et al., 2006, Juan et al., 2007)

diameters of catalyst. Pyridine adsorption

• To determine the density of acid site of catalyst.

(Liu et al., 2006)

Evolved gas analysis by mass

• To monitor decomposition od catalyst.

(Granados et al., 2007)

• To analysis the functional group in catalyst

(Granados et al., 2007, Juan et al., 2007, Xie et

• To observe the absorption of vibration of spectrum.

al., 2006)

Thermo gravimetric analysis (TGA)

• To determine the loading of promoter on support

(Liu et al., 2006)

Hammett indicators

• To determine the basic strength of solid catalyst

(Xie et al., 2006)

spectroscopy (EGA-MS) Fourier transform-infrared spectra

42 2.8

Biodiesel Standardization

Many countries had developed their biodiesel standards such as United States (US), Germany, and Europe. Germany and Europe had developed biodiesel standards for soybean methyl ester and their biodiesel standard codes were DIN E51606 and EN 14214, respectively (Masjuki et al., 2008), while US was ASTM 6751. EN 14214 was representing biodiesel standards for European countries who were the member of the European Committee for Standardization (CEN). These standard had been developed to avoid the operational problem when using the biodiesel in diesel engine.

In these standards, restrictions were placed on the individual contaminants by inclusion of items such as free and total glycerol for limiting glycerol and acylglycerol, flash point for limiting residual alcohol, acid value for limiting free fatty acids and ash value for limiting residual.

Furthermore, several biodiesel properties had been highlighted because they gave a large effect on the diesel engine performance; Cetane number and kinematic viscosity. Cetane number was a prime indicator for diesel fuel quality. It was a dimensionless descriptor of the ignition quality of a diesel fuel. Kinematic viscosity affect to the atomization of a fuel upon injection into the combustion chamber and thereby, ultimately, the formation of engine deposits. These two properties had been discussed deeply by Knothe (2005a) in The Biodiesel handbook.

Table 2.2 shows biodiesel specification following US, Europe and typical diesel standard. In addition to the biodiesel standards, analytical standards were also developed for the purposed of including them as prescribed method in biodiesel standard.

43 Table 2. 2: Biodiesel Specification Standard. Properties

ASTM 6751

EN 14214

Diesel

Density at 15oC (g/cm3)

-

0.86-0.9

0.8

Flash point (oC)

130

120

54

Water and sediment (%vol)

0.05

-

0.05

Water content (mg/kg)

-

500

-

Kinematic viscosity, 40oC

1.9-6.0

3.5-5.0

2.3

Ash (mass %)

-

-

0.01

Sulfated ash (mass %)

0.02

0.02

-

Sulfur (mass %)

0.05

-

-

Copper strip corrosion

No. 3

No. 1(3h/50oC)

1B

Cetane number, min

47

51

50

Free glycerin (mass %)

0.02

0.02

-

Total glycerin (mass %)

0.24

0.25

-

(mm2/s)

(Source: Knothe., 2005a)

CHAPTER 3

METHODOLOGY

3.1

Research Methodology Approach

The research methodology can be divided into three phases; synthesis and screening the heterogeneous catalyst, optimization of batch and continuous biodiesel synthesis, respectively. The detail summary of the methodology is shown in Figure 3.1.

45

Figure 3. 1: Research Methodology Approach

46 3.2

Material and Equipment

WCPO was collected from the university’s cafeteria. The FA composition of the oil sample was determined using GC-MS, while the kinematic viscosity, water content, and acid value were analyzed using ASTM 445-94, D95-83 and 644 respectively (Table 3.1). Figure 3.2 shows the GC chromatogram of the WCPO. Analytical grade reagent of methanol (98%), isopropanol (98%) and standard solution 0.1N potassium hydroxide were purchased from Qrec, NZ. Magnesium nitrate (Fisherbrand, UK), calcium nitrate (GCE laboratory, Singapore), strontium nitrate and barium nitrate (Merck, Germany) were in salt form meanwhile, zirconia (ZrO2) as a support and n-hexane in GC grade were purchased from Merck, Germany.

Table 3. 1: The FFA Profiles and Properties of WPCO Free Fatty Acid profiles

%

Palmitic acid (16:0)

29.49

Linoleic acid (18:2)

9.08

Oleic acid (18:1)

61.43

Physical properties Acid value (mg KOH/mg)

5.08

Density @150C,kg/l

0.8979

API Gravity

26.0

Kinematic Viscosity @400C,cSt

47.58

Water Content, %vol

0.00

Figure 3.2 shows the most component present in WCPO which was identified by an Agilent Technologies 6890N GC-MS and hexane as a solvent. The major component in WCPO is 9-octadenoic acid or its common name is oleic acid with the molecule formula is C18H34O2 and, the second component is hexadecanoic acid or commonly known as palmitic acid with C16H32O2 of molecule formula.

47

Figure 3. 2: GC Chromatograph Analysis of WCPO Sample

48 Palmitic acid is from saturated fat family, while oleic acid is from unsaturated fat family. The saturated fat family has higher melting point than unsaturated fat family because of the Van Der Waals attractions present for saturated FFA (Solomons and Fryhle, 1998). The palmitic acid usually can be found in palm oil. Therefore, it can be declared that the samples of waste are from palm oil based or known as WCPO.

Meanwhile, the stainless steel batch reactors which were equipped with temperature controlled and stirring system was used for the batch transesterification. The continuous system was equipped with pump, stainless steel tube reactor, vertical furnace and separating funnel were set up.

3.3

Experimental

3.3.1

Catalyst Preparation

Alkaline modified zirconias were prepared via wet impregnation of aqueous solution of alkaline nitrate salt and zirconia as a support. Impregnation of ionic metal into the base catalyst took place through several steps. It begins by mixing the base catalyst as a support with the metal solution followed by drying, calcination and finally cooling (Figure 3.3).

49

Figure 3. 3: Catalyst Preparation Process

atalyst preparation technique by Yang and Xie (2007) whose have used zinc Catalyst oxide catalyst was used as a guideline for the catalysts preparation in this study. Yang and Xie (2007) had preparedd the zinc oxide modified with alkali by calcinated the catalyst 500oC for 5h. In the study, the support had been changed to zirconia and the calcinations temperature had been increased in order to increase the efficiency of catalyst decomposition. First, 14wt% aqueous salt solutions (0.1 0.1 mol/l) mol/l were stirred with 15g support at room temperature for 2h. The slurry mixture was then evaporated at 110oC until all the water evaporated. After that, the catalyst was calcined at 650oC for 5h then the catalysts were wer kept in incubator before used.

3.3.2

Catalyst Characterization

The physical, chemical and structural properties of the parent and modified catalyst were characterized characteriz in order to understand more about the catalyst behavior. Powder X-ray ray diffraction (XRD) was employed to identify the crystallography of the catalyst. The XRD patterns were taken with a Bruker D8 Advance diffractometer,

50 which has a Dynamic Scintillation Detector with low background (0.4 cps) and high dynamic range (up to 2 x 106 cps) allowing allowing rapid data acquisition for most samples (Figure 3.4a) which was located at P23, Mechanical Faculty, UTM. UTM The diffractometer uses Cu K α radiation (40 kV 40 mA) with a wavelength (λ) of 1.54 Ǻ.. The samples were recorded from 15o to 80o (2θ) with step scan of 0.05o every 1s. The he phases were identified using the power diffraction file (PDF) database (JCPDS, international Centre for Diffraction Data). Data) (b)

(a)

Figure 3. 4:: Instruments for Catalyst Characterization; a) XRD and b) FESEM

The he morphological study of the catalysts was analysed using a Field Emission Scanning Electron Microscopy (FESEM) ( (Figure 3.4b) which is located at Ibnu Sina Institut, UTM. The FESEM is equipped with high resolution at 1nm (15kV) and 2.2 nm (1kV) with the maximum 2 nA probe current and without changing the objective lens aperture size. The specimen’s size will be up to 200 mm diameter. In addition, an energy dispersive X-ray X spectrometer (EDS) is attached to this system.

(a)

(b)

Figure 3. 5:: Instruments for Catalyst Characterization; a) TPDRO and b) Quantachrome Autosorb-1 Autosorb

51 Carbon dioxide (CO2) and ammonia (NH3) Thermal-Programmed-Desorption (TPD) as represented in Figure 3.5a were used for basic and acid sites determination, respectively. The "heart" of the system is a special reactor that can be sealed from the external environment. Catalysts, after the sample activation, can be stored without time limits under a suitable inert gas atmosphere and safely transferred for analysis. The TPDRO 1100 features two independent reactor connections: one is used for catalyst pre-treatment and the other for the analysis. Finally, the instrument is equipped with dedicated software controls in real time of the activation steps, the analytical cycle and contains routines for data processing (baseline subtraction, integration, reporting, etc.). About 0.2g of catalyst was filled in a reactor, treated under 250oC for 10 min in N2 (20ml/min), and then CO2 (for CO2-TPD) and NH3 (for NH3-TPD) were introduced with a ramp of 1oC/min for 1h (30ml/min). After purged with N2 at room temperature for 30min to remove the CO2 and NH3 in a gas phase, the sample was heated from room temperature to 900oC with a ramp of 10oC/min and 30ml/min gas flowrate in He.

The total surface areas, pore volume, diameter of pore as well as the structure of the microporous material of catalyst were determined using isotherm nitrogen (N2) adsorption at at 77 K. Before adsorption measurements, all the samples were outgased for 20 h at 100oC. Quantachrome Autosorb-1 instrument (Figure 3.5b) is designed for the surface area and pore size analysis of powdered and porous materials.

3.3.3

Pre-test of Catalyst

The pre-testing of the catalyst was held initially to determine suitable condition for catalyst screening tests. The reactor set up for pre-test is same as transesterification reaction process (section 3.4). The condition of experiment was maintained at 6:1 methanol-oil molar ratio, 3wt% of catalyst loading and 60oC for

52 5h. Since the type of alkaline modified zirconia catalyst had not been study yet, the process variables for the catalyst screening was selected based on few references. The reaction temperature and methanol to oil ratio was choose based on a standard for methanol-based transesterification (Gerpen and Knothe, 2005). Meanwhile, the amount of catalyst loading was selected based on a few heterogeneous biodiesel productions studies which 3wt% of catalyst was found. (Jacobson et al., 2008, Liu et al., 2007, Peng et al., 2008).

3.4

Performance of the Catalyst

3.4.1

Batch Biodiesel Production

The transesterification process was performed in a 250ml autoclave equipped with a stirrer. The schematic diagram was illustrated in Figure 3.6. Figure 3.7 shows the flow of biodiesel production in a batch process. Pre-determined amount of oil, methanol and catalyst were added into the reactor, and the reaction was allowed to proceed in a batch mode for specific reaction time. Then, the mixture was cooled to room temperature and filtered with a vacuum filter and leave overnight in a separating funnel for separation process. Finally, the product was collected and analyzed using GCMS (Section 3.5).

53

Water out TT

Water in Pressure Transmitter

Metal cover PT

Thermocouple

Heater

Cooler

Safety jacket

Magnetic bar stirer Magnetic stirer

E-1 E-2

Figure 3. 6: Schematic Diagram of Batch Reactor

Figure 3. 7: Biodiesel Production Flow Chart

54 3.4.2

Continuous Biodiesel Production

The continuous biodiesel production was carried out in a 300mm high x 10mm diameter stainless steel 316 tube. The reactor was equipped with a heater jacket and temperature controller (carbolite). Prior to reaction, the Sr/ZrO2 in powder form was diluted with a catalyst bead, which is 5mm diameter of stone to increase the reaction surface and loaded into the tube reactor as shown in Figure 3.8. Figure 3.9 shows the scheme flow sheet of the system, while Figure 3.10 photographs of the system set up in laboratory. The reactor was heated to desired temperature (90-180 o

C). WCPO and methanol were pumped into the reactor at weight hourly space

velocity (WHSV) = (0.65-0.95) h-1 with the required ratios of methanol to oil (10:130:1) for 3h. The process condition of the reaction was designed by STATISTICA 8.0 version software. The mixture of products from reactor was collected in round bottom flask and heated at 60oC to recycle any excess methanol to the tank of methanol. Then, the mixture was cooled to room temperature and leave overnight in a separating funnel for separation process. Finally, the product was collected and analyzed using a GC-MS following describing method in section 3.5. The production rate of FAME is (5-10) ml/h.

Figure 3. 8: Side View of the Reactor

55

Figure 3. 9: Scheme Flow Sheet of PBR Process.

56

Figure 3. 10: Transesterification Reaction in Packed Bed Reactor.

3.5

Product Analysis

3.5.1

FAME Determination Using GCMS

The solution was analysed in an Agilent Technologies 6890N Gas Chromatograph- Mass Spectroscopy with an inert mass selective detector 5975 (Figure 3.11). The capillary column is an Agilent 19091S-433 HP-5MS (30mm x 250µm x 0.25µm) and helium was used as a carrier gas. The oven temperature of GC was held at initial temperature of 80oC for 0.5 min and then ramped to a final temperature of 250oC at a rate of 10oC/min, held for 5 min, with a total run time of 42 min. the injector temperature was 325oC and that of the detector was 250oC. Helium gas was flow at 2 ml/min.

57

Figure 3. 11: Agilent Technologies 6890N GC-MS.

3.5.2

Physico-chemical Properties

The physico-chemical properties of the biodiesel were determined using a standard method as follows:

1. Density (ASTM D1298) 2. Kinematic Viscosity, 40oC (ASTM D445) 3. Cetane index (ASTM D976)

58 3.6

Formulation of Responses

The important response in biodiesel production is conversion of FFA and methyl ester (ME) yields. Conversion of FFA can be defined as the difference of acid value (AV) of the sample and product over the initial acid value of the sample (Wang et al., 2007), which is represented by equation 3.1.

Conversion

AV final  of FFA (%) =  1 − AV initial 

  × 100 % , 

(3.1)

Where: AVfinal

= Acid value of upper layer product

AVinitial

= Acid value of oil

Meanwhile, the percentage of ME yield can be calculated using eq 3.2.

ME yield (%) =

FAME area from GCMS (%) × weight of product × 100 % (3.2) weight of WCPO sample

CHAPTER 4

RESULT AND DISCUSSION

4.1

Development of Alkaline Modified Zirconia Catalyst for Biodiesel Production

4.1.1

Characterization of Catalyst

4.1.1.1 Crytallinity

The XRD diffractograms of pure and modified zirconia are depicted in Figure 4.1. The crystal structure of pure ZrO2 (pattern a) was primitive monoclinic, with lattice parameter (in nm) of 5.150, 5.2116 and 5.3173 for a,b and c at 90o, 99.23o and 90o, respectively. The crystal structure of ZrO2 was sustained after 5h calcination at 650oC since neither additional peak nor broadening peak were detected (pattern b). Besides, the Mg/ZrO2 (pattern c) and Ca/ZrO2 catalysts (pattern d) exhibited similar patterns with the parent ZrO2 with no additional peak attributed to magnesium (Mg) or calcium (Ca) was observed, respectively. These indicated that Mg or Ca was incorporated into ZrO2 lattice to form homogeneous crystalline structure known as solid solution without changing the structure of ZrO2. Therefore, the crystal structure

60 of ZrO2 in Mg/ZrO2 and Ca/ZrO2 was sustained since the crystalline structures of modified zirconia were almost like the parent ZrO2 in pattern a {, 2006 #28}.

On the other hand, the XRD pattern of Sr/ZrO2 (pattern e) exhibited predominantly peaks of similar monoclinic ZrO2 as the parent with additional peaks of Sr/ZrO2 at 30.811o. The crystal structure of Sr/ZrO2 was detected as primitive orthorhombic, with lattice parameter (in nm) of 5.7862, 5.8151 and 8.196 at 90o for a,b and c, respectively. A distinguish observation was detected for Ba/ZrO2 XRD diffractogram. The crystal structure of zirconia transformed from monoclinic to rhombohedral (Rh) hexagonal when barium (Ba) metal was loaded on the support. The crystal structure of Rh-hexagonal ZrO2 have a lattice parameter (in nm) were 5.6295 for a=b, 15.5925 for c and 90o (α=β) and 120o (γ). In addition, the presence of BaNO3 peak was detected in the XRD pattern indicating the incomplete transformation of BaNO3 to BaO at 650oC.

The crystallite size (Table 4.1) was calculated from the highest ZrO2 crystal XRD diffractogram peak for each catalyst using Scherrer formula. The calculation was shown in Appendix B. Among the screened catalysts, only Ba/ZrO2 crystallite size was considerably larger whilst the crystallite sizes for Mg/ ZrO2, Ca/ZrO2, and Sr/ZrO2 were almost similar. The modification of parent ZrO2 with alkaline earth metals decreased the crystallite size of ZrO2 except for Ba/ZrO2. The smaller crystallite sizes of Mg/ZrO2, Ca/ZrO2, and Sr/ZrO2 suggested that strong interaction between the alkaline metal and Zr species enhanced the dispersion of alkaline metal on ZrO2 support. A similar trend was found by Yan et al. (2009a). Larger ZrO2 crystallite size in Ba/ZrO2 catalyst was confirmed by the change in the crystal structure of the parent ZrO2. The crystal structure of parent ZrO2 remained as monoclinic for Mg/ ZrO2, Ca/ZrO2, and Sr/ZrO2. Nevertheless, the crystal structure of ZrO2 for Ba/ZrO2 was changed to Rh- hexagonal crystal structure which was usually found in ceramic production. Normally, the crystal structure of the ZrO2 is a monoclinic or tetragonal (Garcia et al., 2008, Park et al., 2010a, Park et al., 2010b, Peters et al., 2006, Rack Sohn et al., 2001, Sree et al., 2009, Sunita et al., 2008). The

61 change in the surface structure may also result r from surface re-crystallization and formation or elimination of active sites (Fogler, 2006).

Figure 4. 1: XRD Pattern attern of Catalyst a) ZrO2 and b) ZrO2, c) Mg /ZrO2, d) Ca /ZrO2, e) Sr/ZrO2, f) Ba/ZrO2 after Calcinations at 650oC in 5h.

62

Table 4.1: The Physicochemical Properties of ZrO2 and the Modified Zirconia Catalyst. Catalysts

α

Pore Diameter, Dpore

b

Pore Volume, VPore

(m2/g)

(cc/g)

(nm)

(nm)

(nm)

ZrO2

2.70

0.011

16.62

384

45.007

Mg /ZrO2

4.17

0.023

19.49

252

42.752

Ca /ZrO2

5.21

0.033

18.35

246

42.757

Sr/ZrO2

12.97

0.083

25.51

356

42.757

Ba/ZrO2

20.31

0.128

30.12

416

58.185

a

from N2-absorption

b

calculated from FeSEM

c

calculated from XRD results using Debye-Scherrer equation (Appendix B)

Particle size

c

Surface Area, SABET

Crystal Size

63 4.1.1.2 Physico-Chemical Properties of Catalyst

The alkaline earth metal was dispersed on zirconia in order to change the physico- chemical properties of zirconia, and their catalytic activity performance on biodiesel production should be increased as well. The physical properties of parent and modified ZrO2 are tabulated in Table 4.1. The surface area, pore volume and pore diameter increased when Mg, Ca, Sr, and Ba metals were loaded on zirconia in accordance to the order of the element size in the periodic table. The increment in surface area might be due to the strong interaction of the alkaline metal with ZrO2 support, which reduced the surface diffusion of Zr, inhibited sintering and stabilized the crystal surface of ZrO2.

On the other hand, Jacobson et al. (2008) reported the pore structure was a primary requirement for an ideal solid catalyst for biodiesel production since a typical triglyceride molecule has a pore diameter of approximately 58Å (5.8nm). The larger average pore diameter and interconnected pores would minimize diffusion limitations of reactant molecules. Consequently, the reactant molecules (oils) easily diffused into the interior of the catalyst and became in contact with more acid-basic active sites on catalyst, then shows better catalytic activity (Fogler, 2006, Jacobson et al., 2008).

Besides, all the catalysts could be defined as mesoporous catalyst since the pore diameter of each catalyst was in intermediate range between 2nm (micropore) and 50nm (macropore). The mesoporous catalyst has been widely used for biodiesel production in previous studies (Alba-Rubio et al., 2010, Albuquerque et al., 2009, Jacobson et al., 2008, Juan et al., 2007, Peng et al., 2008, Samart et al., 2009). In addition, the specific pore volume which represents the total internal volume per unit mass of catalyst would facilitate the reaction by amplifying the reaction surface. Therefore, the alkaline modified zirconia appeal to be the best catalyst in biodiesel production since it has a high pore diameter and large surface area.

64

a

b

c

d

e

Figure 4. 2: FESEM Monograph of a)ZrO2 b)Ca/ZrO2 c)Mg/ZrO2 d)Sr/ZrO2 e)Ba/ZrO2 .

The particle morphology of the catalysts was captured via FESEM, and the monograph of each catalyst is demonstrated in Figure 4.2. The parent and modified ZrO2 exhibited well- shaped crystalline particles (Figure 4.2a). Each alkaline earth metal doping on zirconia displayed different texture distribution on zirconia. Mg (Figure 4.2b) metal as well as Ca metal (Figure 3c) homogeneously dispersed on

65 zirconia surface. However the zirconia crystal still remained. Meanwhile, the Sr metal (Figure 3d) was widely disseminated on zirconia surface covering it. On the other hand, the zirconia structure was altered with Ba metal loading (Figure 3e) as small amount of Ba metal was observed to be dispersed on the zirconia surface. The monographs of FESEM endorsed the crystalinity result of XRD.

Apart from morphology study of the catalyst, the particle size of each catalyst was determined from Figure 4.2 and tabulated in Table 4.1. As can be observed, the alkaline earth metal presence on zirconia surface reduced the particle size of the modified catalyst for Ca, Mg and Sr metals, respectively but for Ba metal, the particle size increased corroborating the trend in the crystallite size of ZrO2. The same trend of study was reported by Alba-Rubio et al. (2010).

4.1.1.3 Basicity and Acidity

Carbon dioxide adsorption-desorption technique usually enables to determine the strength of basic sites present on the catalyst surface together with total basicity. The CO2-TPD profiles for pure and all the modified zirconia is illustrated in Figure 4.3. The curve patterns of sample constituting a main CO2 desorption peaks were detected between 200°C and 1000oC. According to Wen et al. (2010), the desorption peak observed at 100-425oC can be accredited as weaker, 425-550oC as moderate and over than 550oC as stronger basic strength. The basic strength of the catalyst was generated due to isolated O2− anions located in the particular position of the mixed oxide surface (Sree et al., 2009).

66

Figure 4. 3: CO2-TPD Profiles for Modified Zirconia Catalyst.

67 Different desorption peaks were observed for parent ZrO2 and all the modified catalysts. A small desorption peak can be observed at 416oC for the parent ZrO2. This indicated that the parent ZrO2 had a weaker basic site by itself. The basic site of the parent ZrO2 increased with loading of earth metal accordingly to the order of electropositive tendency of the element (i.e MgBa>Ca. Thus, it is likely that the activity of the catalysts is independent of the electropositive tendency of the element, but possibly dependent on other factors such as active site which will be discussed in the next section (section 4.1.3).

On the other hand, it was observed biodiesel production over Mg/ZrO2 produced soap as the final product. The soap was in bright brown colour and was not soluble in oil and water. Similar observation was cited by Liu et al. (2007a) who reported that MgO provided higher catalytic activity than CaO, but the soap formation could not be avoided.

Figure 4. 6: Possible chemical reaction path in biodiesel production

73

4.1.3 Relationship of Basicity and Acidity of Modified Catalyst on Biodiesel Production

Previous researchers focus on a few catalyst characteristic such as BET surface area, pore diameter as well as crystalinity to study the catalytic activity of the catalyst in biodiesel production (Sree et al., 2009, Sun et al., 2010, Yan et al., 2009b). Only the few study were investigated the influence of basicity or acidity of the catalyst (Sree et al., 2009, Sun et al., 2010). Figure 4.7 illustrates the relationship of basicity and acidity on ME yield and FFA conversion. The trend in the figure indicated the ME yield was not concurrent with total acidity or basicity of the catalyst. As can been seen, Ba/ZrO2 exhibited the highest total acidity as well as basicity, but the ME yield was the lowest among the modified catalyst. This can be explained by the XRD results where the changes of ZrO2 structure to Rh-hexagonal crystal structure contributed to higher crystallite size and influenced the catalytic activity. Thus, the low ME yield and FFA conversion over Ba/ZrO2 can be attributed to the catalysts had been deactivated.

Conversely, Mg/ZrO2 which has the second highest acidity recorded lower ME yields and FFA conversion, respectively compared to Sr/ZrO2. Meanwhile, Ca/ZrO2 with the third highest acidity gave a lower ME yield compared to Sr/ZrO2 as well. This indicated that, the esterification reaction led the biodiesel production instead of transesterification for Mg/ZrO2, Ca/ZrO2 and Ba/ZrO2 as well as parent ZrO2 due to the conversion of FFA was higher than ME yields. This tendency could be attributed to higher amount of acid sites present in Mg/ZrO2, Ca/ZrO2 and Ba/ZrO2 compared to Sr/ZrO2.A notable observation was observed for Sr/ZrO2. The ME yield was the highest over Sr/ZrO2, but the FFA conversion was lower compared to Mg/ZrO2. This indicated that the transesterification reaction led the biodiesel production instead of esterification reaction with presence of higher basicity sites on Sr/ZrO2.

74 In overall, the catalytic activities of these catalysts are depends more on the basicity than the acidity sites since the Sr/ZrO2 (i.e contain high basicity) shown higher ME yield than Mg/ZrO2 (i.e contain high acidity). Therefore, Sr/ZrO2 was screened for future study since it gave higher ME yield and reasonable FFA conversion. Furthermore, simultaneous transesterification and esterification could be confirmed by this study since both reactions led on converting WCPO into corresponding methyl hyl ester in the presence of the catalyst containing higher basic and acid sites (Yan et al., al. 2009a).

50

ME Yield

45

Conversion

5

basicity 40

4

Acidity

35 3

25

2

20 1 15 10 0 5 0

-1 ZrO2

Mg/ZrO2

Ca/ZrO2

Sr/ZrO2

Ba/ZrO2

Figure 4. 7: Effect of total basicity and acidity of catalyst on catalytic c activity at 3wt% catalyst loading, 6:1 methanol to oil molar ratio, 5hr and 60oC.

mmol/g

%

30

75 4.1.4

Possible Mechanism Suggestion for Simultaneous Esterification and Transesterification

Research conducted by Yan et al.(2009a) suggested that the simultaneous esterification and esterification reaction should occur in presence of acid and basic sites in the catalyst. Therefore, a simultaneous mechanism of transesterification and esterification reaction is proposed in this study since evidence of acid and basic sites with different strengths for each catalyst are readily available from NH3-TPD and CO2-TPD profiles. The support i.e. zirconia surface provided the acid and basic sites for the catalyst. However, metal doping on the zirconia surface increased the strength and amount of the acid and basic sites. Both sites play important role in biodiesel production. Figure 4.8 postulates simultaneous esterification and transesterification mechanism for biodiesel production from WCPO. This possible mechanism is following the basic of esterification and transesterification reaction mechanism that has been proposed by previous studies (Schuchardt, 1998, Yan et al., 2009a).

As an overall, the chemical reaction involves three steps; adsorption, surface reaction and desorption (Fogler, 2006). In this case, carbonyl group of FFA adsorbs on acid site and methanol adsorb on the basic site of the catalyst to produce carbocation and oxygen anion for esterification and transesterification, respectively in the first step. Then, at the surface of catalyst (step 2), nucleophilic attacks carbocation and oxygen anion at the each hydroxyl group of methanol and carbonyl group of triglyceride for esterification and transesterification reaction, respectively. The nucleophilic attack would generate tetrahedral intermediate. Finally (Step 3), the final product (FAME) forms from desorption of hydroxyl group and alkyl triglycerides from catalyst surface after breaking the –OH and –C–O– bond, respectively. While, the deprotonates catalyst will regenerates the active species for starting another catalytic cycle. Besides, H2O and glycerol also will forms from esterification and transesterification reaction after the catalytic cycle complete.

76

Figure

4.

8:

Possible

Transesterification Reaction. eaction.

Mechanism

of

Simultaneous

E Esterification

and

77 4.2

Influence of Process Variable on the Biodiesel Production over Sr/ZrO2 in Batch Process

In biodiesel production, several process variables could influence the yield of biodiesel such as molar ratio of triglycerides (oil) to alcohol, catalyst loading, reaction temperature and reaction time. The best combination of the process variables could save the production cost in an effective way. Previous studies (Felizardo et al., 2006, Jitputti et al., 2006, Leung and Guo, 2006, Liu et al., 2007, Wang et al., 2007) had proved that the yield of biodiesel could be increased by introducing an excess amount of methanol to shift the equilibrium to the right-hand side. A large amount of methanol is required to avoid the backward direction of transesterification from occurring. Besides, the reaction temperature and catalyst loading were important as well as reaction time in order to minimize the cost of production. The effect of these three variables has been studied by conducting three series of experiment. The range of experiment for these three variables were determined first, then in each series of experiment, two process variables were kept constant at center point and one process variable was varied in the range to study the effect of it on biodiesel production. The range of experiment was determined based on possibility of the catalyst performance since the type of catalyst has not been studied before.

Figure 4.9 illustrates the effect of methanol loading on oil for biodiesel production from WCPO in the presence of Sr/ZrO2. The figure indicated that slightly different of ME yields can be observed for a different amount of methanol loading. The rate of methyl ester formation increased with increment of methanol to oil ratio. However, methanol loading over 30:1 molar ratio had decreased the ME yield. This occurs because of the catalyst might be dilute with presence of excess methanol. Apart from methanol loading, the biodiesel production would depend on catalyst loading. The effect of catalyst loading on ME yield is shown in Figure 4.10. The figure indicated that the catalyst loading slightly significant on ME yields. There are slightly increments of ME yields with increment of Sr/ZrO2 amount. But, Sr/ZrO2

78 loading beyond 4wt% decreased the ME yields. Instead of catalyst loading and methanol ratio, reaction temperature of the process exaggerated significantly biodiesel production from WCPO with presence of Sr/ZrO2. As shown in Figure 4.11, the catalyst performed very well at a lower reaction temperature. As an overall, the best reaction conditions for biodiesel production are finding based on ranges from Figures 4.9-4.11.

80 70 ME yield (%)

60 50 40

30:1

30

40:1

20

20:1

10

10:1

0 0

60

120

180

240

300

Time (min) Figure 4. 9: Effect of Molar Ratio of Methanol to Oil on ME Yield at 3wt%, T=120oC.

79

80

ME yield (%)

70 60 1wt% 2wt%

50

3wt% 40 4wt% 30 0

60

120

180

Time (min) Figure 4. 10: Effect of Catalyst Loading on ME Yield at T=120oC,30:1 Methanol-oil

ME yield (%)

Ratio.

100 90 80 70 60 50 40 30 20 10 0

80⁰C 100⁰C 120⁰C 140⁰C

0

60

120

180

240

300

Time (min)

Figure 4. 11: Effect of Reaction Temperature on ME yield at 3wt%, 30:1 Methanoloil Ratio.

80 4.3

Optimization of Biodiesel Production from Waste Cooking Palm Oil via Response Surface Methodology over Sr/ZrO2

4.3.1

Response Surface Methodology (RSM)

Most of the biodiesel production experiments were designed by changing one separator at a time (COST) ((Liu et al., 2006, Sree et al., 2009, Yan et al., 2009a). The design will contribute to a larger number of experiments to be studied. Moreover, the reaction system can be poorly understood since more than one variable can simultaneously influence the system. Therefore, statistical approach is suitable since the relationship between the values of some measureable response variable(s) and those of a set of experimental factors presumed to affect the response(s) are quantified. In addition, the best value or values of the response(s) could be determined.

Variable selection Design of experiment

DOE spreadsheet

Experiment

Mathematical model Analysis of Data

Validity of Data

Find relationship

Optimization Figure 4. 12: Flow of RSM study

81 In most cases, the relationship of the variables and measured response is either too complex or unknown, thus the empirical approach is necessary. RSM is governed by certain laws that can be approximated by deterministic relationship between the best conditions (levels) of the factors to optimize a desired output. RSM is a set of techniques designed to find the “best” value of the response and at least gain the better understanding of the overall response system. The method was developed by Box-Wilson, Box-Hunter, Bradley, Davies and Hunter. The techniques are employed before, during and after regression analysis (Cornell, 1990).

The RSM studies of biodiesel have been carried out by well established software such as Design expert, Statistica, and Mini Tab. Even though the software is different, the flow of study is similar. Figure 4.12 shows the flow of RSM study. The main step of RSM study is consist of design of experimental (DOE) and the subsequent analysis of the experimental data mostly validity of the data are examined before the optimization can be carried out (Appendix D).

4.3.2 Biodiesel Production in One-Pot Stainless Steel for Batch Process

4.3.2.1 Design of Experiment

The range and level coded of the transesterification process variables are listed in Table 4.3. The four variables are methanol to oil molar ratio (X1), catalyst loading (X2), reaction times (X3) and reaction temperatures (X4). Each variable consists of three different levels from low (−1), to medium (0) and to high (1). A central composite design (CCD) with full 24 factorial designs (four factors each at two levels), eight star point and two center point was employed. The total number of experiments was 26 augmented 24 experiments with two replications at center point. The complete CCD matrix of and the results are given in Table 4.4. The percentage

82 of methyl ester (ME) yield (Y1) and the conversion of oil (Y2) were taken as the response of the design experiment.

Table 4. 3: Experimental Range and Level Coded Factors

Symbol

Range and Levels -1

0

+1

Molar ratio methanol: oil

X1

20:1

30:1

40:1

Catalyst loading, wt%

X2

2

3

4

Reaction Time, min

X3

120

180

240

Reaction Temperature

X4

90

120

150

4.3.2.2 Validity of Model

The full quadratic models were established by using the method of least squares. The predicted ME yield and FFA conversion models are shown in eqs (4.4) and (4.5):

Y1 = −188.582 + 3.258 X 1 + 13.369 X 2 + 1.040 X 3 + 1.895 X 4 2

2

2

− 0.037 X 1 − 1.932 X 2 − 0.001X 3 − 0.002 X 4

2

(4.4)

− 0.081X 1 X 2 + 0.003X 1 X 3 − 0.011X 1 X 4 + 0.013X 2 X 3 − 0.023X 2 X 4 − 0.006 X 3 X 4

Y2 = −192.048 + 4.623 X 1 − 0.266 X 2 + 0.774 X 3 + 1.978 X 4 2

2

2

− 0.050 X 1 − 0.843 X 2 − 0.001X 3 − 0.003 X 4

2

(4.5)

− 0.198 X 1 X 2 + 0.004 X 1 X 3 − 0.011X 1 X 4 + 0.056 X 2 X 3 + 0.001X 2 X 4 − 0.005 X 3 X 4

83 Table 4. 4: CCD and Experimental Result

Manipulated variables

Responses

X1

X2

X3

X4

Y1

Y2

Molar ratio

Catalyst

Reaction

Reaction

Ester

Conversion

(MeOH:oil)

loading

time

Temperature

yield

(%)

(wt%)

(min)

(oC)

(%)

20 (-1)

2 (-1)

120 (-1)

90 (-1)

59.56

48.73

20 (-1)

2 (-1)

120 (-1)

150 (1)

73.55

69.02

20 (-1)

2 (-1)

240 (1)

90 (-1)

67.56

50.00

20 (-1)

2 (-1)

240 (1)

150 (1)

53.76

40.00

20 (-1)

4 (1)

120 (-1)

90 (-1)

59.34

43.88

20 (-1)

4 (1)

120 (-1)

150 (1)

69.90

53.00

20 (-1)

4 (1)

240 (1)

90 (-1)

65.45

56.00

20 (-1)

4 (1)

240 (1)

150 (1)

45.32

50.00

40 (1)

2 (-1)

120 (-1)

90 (-1)

56.39

54.80

40 (1)

2 (-1)

120 (-1)

150 (1)

74.56

68.59

40 (1)

2 (-1)

240 (1)

90 (-1)

84.46

80.00

40 (1)

2 (-1)

240 (1)

150 (1)

34.78

42.31

40 (1)

4 (1)

120 (-1)

90 (-1)

52.89

40.00

40 (1)

4 (1)

120 (-1)

150 (1)

54.89

56.44

40 (1)

4 (1)

240 (1)

90 (-1)

74.85

72.69

40 (1)

4 (1)

240 (1)

150 (1)

40.23

40.00

30 (0)

3 (0)

180 (0)

120 (0)

76.67

67.94

9.42 (-α)

3 (0)

180 (0)

120 (0)

61.82

42.00

50.58 (+α)

3 (0)

180 (0)

120 (0)

62.41

57.00

30 (0)

0.94 (-α)

180 (0)

120 (0)

65.67

63.00

30 (0)

5.06 (+α)

180 (0)

120 (0)

73.45

71.45

30 (0)

3 (0)

57 (-α)

120 (0)

64.75

53.65

30 (0)

3 (0)

303 (+α)

120 (0)

45.76

50.00

30 (0)

3 (0)

180 (0)

58 (-α)

67.06

50.67

30 (0)

3 (0)

180 (0)

182 (+α)

70.54

68.00

30 (0)

3 (0)

180 (0)

120 (0)

74.61

70.00

84

Table 4. 5: ANOVA Analysis.

Sum of Squares(SS)

Degree of Freedom(d.f)

Mean Squares (MS)

F-value

F0.05

Regression (SSR)

2807.32

14

200.52

3.39

>2.74

Residual

649.87

11

59.08

Total (SST)

3457.29

25

Regression (SSR)

2958.53

14

211.32

3.22

>2.74

Error (SSE)

722.50

11

65.68

Total (SST)

3681.03

25

Sources FFA conversion Model

ME yield model

85 Meanwhile, analysis of variance (ANOVA) was applied in order to check the experimental data was adequate and fitted the model. Parity plot (Figure 4.13) compares the observed experimental ME yield and conversion with the predicted values. The R2 value for predicted ME yield is 0.8037; that is, 80.37% of the variability in the data is accounted to the model. For conversion, the R2 value is 0.8102 indicating 81.02% of the variation of data can be explained by the model. According to Haaland (1989), the empirical model is adequate to explain most of the variability in the assay reading which should be at least 0.75.

The common indicator in ANOVA analysis to identify the significant of the model in STATISTICA software is F-value, which had been explained by Cornell (1990). The ANOVA analysis (Table 4.5) indicates that the empirical models for ME yields and conversion give good predictions at high confidence level (95%) since the F-values for ME yield and conversion are higher than the tabulated F-value (F0.05, 14,11)=

2.74) which are 3.39 and 3.32, respectively. Figure 4.14 shows the student’s t-

distribution values in a Pareto chart and the corresponding p-values of the variables in eqs (4.4) and (4.5).The p-value serves as a tool to check the significance of each coefficient. The corresponding coefficient with smaller p-value or the greater magnitude of t-value denotes more significance into the model. Generally, a 5% level of significance is sufficient. As illustrated in Figure 4.14, the largest effect on ME yield and conversion is the interaction of linear term of reaction time and reaction temperature, which implied the largest t-value (-5.031) and smallest p-value (0.000). Linear term of reaction time could also be regarded as significant variable in ME yield. Meanwhile, the quadratic term of catalyst loading and reaction temperature are significant in conversion of FFA.

86 85

a)

80 75

Predicted Values

70 65

R2=0.8037

60 55 50 45 40 35 25

30

35

40

45

50

55

60

65

70

75

80

85

90

Observed Values

80

b) 75 70

Predicted Values

65

R2=0.8102

60 55 50 45 40 35 35

40

45

50

55

60

65

70

75

80

Observed Values

Figure 4. 13: Parity Plot for a) ME Yield and b) FFA Conversion

85

87

a)

b)

Figure 4. 14: Pareto Chart of ME Yield and FFA Conversion onversion

88 4.3.2.3 Interaction of Process Variables

The empirical model is plotted as a three-dimensional surface representing the responses (ME yield and conversion) as a function of two factors within experimental range considered (Figures 4.15 to 4.20). Figure 4.15 illustrates the relationship of methanol-oil ratio and catalyst loading at 3 hr and 120oC on ME yield and FFA conversion. ME yield (Figure 4.15a) and FFA conversion (Figure 4.15b) increased with increasing amount of methanol up to a critical catalyst loading. The overloading of methanol would dilute the catalyst and reverses the reactions since transesterification and esterification are reversible. The same pattern has been reported by Srilatha et al. (2009). However, the FFA conversion increased when the catalyst loading increased as illustrated by the elliptical nature of the contour plot in FFA conversion and the circular nature in ME yield. Similar trends were also observed by Meng et al. (2008) and Srilatha et al. (2009).

The relationships of methanol-oil ratio and reaction time on ME yield and FFA conversion are exhibited in Figures 4.16a and 4.16b portraying the circular nature of the contour plot at 3wt % Sr/ZrO2 loading and 120oC. This explained that, the interaction of methanol-oil ratio and reaction time has a smaller effect on ME yield and FFA conversion. ME yield and FFA conversion increased to the maximum, then decreased after overloading methanol and having longer reaction time. Meanwhile Figures 4.17a and 4.17b illustrate the elliptical nature of the contour plot for methanol-oil ratio and reaction temperature interaction. The ME yield and FFA conversion increased with increasing methanol and higher reaction temperature after 3h in presence of 3wt% Sr/ZrO2.

ME Yield,%

89

> 70 < 70 < 60 < 50 < 40

oa din g

,w

t%

M

ati il R o ol an eth

o

FFA Conversion,%

Ca tal ys tL

> 60 < 60 < 50 < 40 < 30 < 20

Ca ta l

ys t

Lo ad in

g, wt %

M

oi olan h t e

lR

o ati

Figure 4. 15: Response Surface Plot of the Combine Methanol-oil Ratio and Catalyst Loading on a) ME Yield and b) FFA Conversion at 120oC for 3hr.

ME Yield,%

90

> 70 < 70 < 60 < 50 < 40 < 30 < 20 < 10

oi olan h t Me

mi n

o ati lR

ion,% FFA Convers

Re ac tio nT im e,

> 60 < 60 < 40 < 20 70 < 70 < 60 < 50 < 40 < 30 < 20 < 10

tio n

Te mp er atu re ,

M

o

C

a eth

l no

lR -o i

ati

o

FFA Conversion,%

Re ac

> 60 < 60 < 40 < 20 70 < 70 < 60 < 50 < 40 < 30

nT

im e,

mi n

ys tal Ca

w g, din a o tL

t%

FFA Conversion,%

Re ac tio

> 60 < 60 < 50 < 40 < 30 < 20

Re a

c ti on

Ti

m

e,

m

in

ta Ca

t lys

t% g ,w n i ad Lo

Figure 4. 18: Response Surface Plot of the Combine Reaction Time and Catalyst Loading on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar Ratio and 120oC.

ME Yield,%

94

> 70 < 70 < 60 < 50 < 40

on T

em pe ra tur e,

ys tal Ca

o

C

tL

w g, din a o

t%

FFA Conversion,%

Re ac ti

> 65 < 65 < 60 < 55 < 50 < 45

Re a

c ti on

Te m

pe

ra tu re ,

o

C

ys tal Ca

t

t% ,w ing d a Lo

Figure 4. 19: Response Surface Plot of the Combine Reaction Temperature and Catalyst Loading on a) ME Yield and b) FFA Conversion at 30:1 Methanol to Oil Molar Ratio for 3h.

ME Yield,%

95

> 80 < 80 < 60 < 40 < 20 60 < 60 < 40 < 20 4.10

Residual

471.875

6

78.646

Total (SST)

6761.465

15

Regression (SSR)

5793.364

9

643.707

9.38

4.10

Residual

411.718

6

68.620

Total (SST)

6205.082

15

Sources ME yield

FFA conversion

102

a) p-value Factor 0.001

X1

0.001

X22

0.041

X32

0.047

X1X2

0.056

X12

0.183

X2

0.438

X1X3

0.558

X3

0.829

X2X3

6.128 -5.716 -2.601 2.500 2.370 1.505 -0.830 0.620 -0.226 p=.05 Standardized Effect Estimate (Absolute Value)

b) p-value Factor

0.000

X1

0.002

X 12

0.036

X 32

0.075

X2

0.092

X 22

0.248

X 1X 3

0.267

X 1X 2

0.526

X 2X 3

0.912

X3

6.823 -5.217 -2.688 -2.148 -2.007 1.224 -1.278 -0.673 0.115 p=.05 Standardized Effect Estimate (Absolute Value)

Figure 4. 22: Pareto Chart of a) ME Yield and b) FFA Conversion.

103 As illustrated in Figure 4.21, the largest effect on ME yield and FFA conversion are the linear term of molar ratio of methanol to oil (X1); which implied the largest t-value (6.128 and 6.823) and smallest p-value (0.001 and 0.000), respectively followed by quadratic term of molar ratio of methanol to oil (X12); which implied the largest t-value (-5.217 and -5.716) and smallest p-value (0.001 and 0.002), respectively at approximate 99% significant level, respectively. Meanwhile, quadratic term of WHSV (X32) and interaction of linear term methanol-oil molar ratio (X1X2), and showed the significant effect on ME yield at 96% singnificant level. On the others hand, quadratic term of WHSV and linear term reaction temperature showed the significant effect on FFA conversion at 97% and 96% singnificant level, respectively. Furthermore, others variable offer less significant effect on ME yield and FFA conversion in the process.

4.3.3.3 Interaction of Variable Study

The empirical model (eqs. 4.6 and 4.7) was plotted as a three-dimensional surface representing the responses (ME yield and FFA conversion) as a function of two factors within experimental range considered (Figures 4.23-4.25). As can be observed from these three figures, large amount of methanol loading on the reaction enhanced the ME yield and FFA conversion with the presence of Sr/ZrO2 in the continuous biodiesel production. This has been agreed by the Pareto chart before (Figure 4.22) which showed the linear and quadratic term of methanol-oil ratio give the largest effect on biodiesel production. Figure 4.23 illustrates the interaction of methanol-oil molar ratio and reaction temperature at 0.79 g oil g cat-1 h-1 on ME yield and FFA conversion. The elliptical nature of contour plot was observed for the both responses. However, the contour plot of ME yield is more ellipse than FFA conversion. This indicated that, the interaction of methanol-oil molar ratio and reaction temperature showed the largest effect on ME yields than FFA conversion. As illustrated in Figure 4.23, lower reaction temperature and methanol loading give low ME yield and FFA conversion. This is might due to insufficient amount of

104 methanol loading into the reaction offer the backward transesterification or esterification reaction since the both reactions are irreversible which converted the FAME into the FFA. Besides, triglycerides will be cracked into FFA when the high reaction temperature employed at lower methanol loading. In addition, the ME yield and FFA conversion increased rapidly after amount of methanol loading was enlarged particularly at higher reaction temperature. This indicated that, an amount of methanol loading was adequate and the backward reaction can be avoided as well. But, at lower reaction temperature, overloading methanol might reduce the ME yield and FFA conversion, respectively due to inactivation of the catalyst (Srilatha et al., 2009, Sunita et al., 2008).

The relationships of methanol-oil molar ratio and WHSV on ME yield and FFA conversion is exhibited in Figure 4.24, the figure portraying the elliptical nature of the contour plot at 125oC. There is slightly effect of WHSV on ME yield and FFA conversion. This indicated that longer residence time (WHSV) did not promise the ME yield or FFA conversion would increase. However, the ME yield increased to the maximum with presence of the plenty amount of methanol, and then decreased after overloading methanol or having longer residence time.

On the other hand, the reaction temperature contributed a small effect on biodiesel production as clarified in Figures 4.23 and 4.25. This is might due to the special features of the newly modified which is has both acid and basic site. The site of catalyst plays the role in the reaction. While, Figure 4.25 depicts the effect of WHSV and reaction temperature interaction in presence of 20:1 methanol-oil ratio on ME yield. The interaction of these two variables indicated less impact on ME yield and conversion as indicated in the Pareto chart and represented by circular nature of contour plot. Larger ME yield can be attained at higher reaction temperature and longer residence time. The same patterns have been studied by Sunita et al. (2008).The result showed that the reaction is endothermic (Marchetti and Errazu, 2008).

105

Figure 4. 23: Response Surface Plot of the Combine Methanol-oil Methanol Ratio and Reaction Temperature on a) ME Yield and b) FFA Conversion at 0.79 g oil g cat-1h-1

106

Figure 4. 24: Response Surface Plot of the Combine Methanol-oil Ratio and WHSV on a) ME Yield and b) FFA conversion at 125oC.

107

Figure 4. 25: Response Surface Plot of the Combine WHSV and Reaction Temperature on a)ME Yield and b) FFA Conversion at 20:1 Methanol-Oil Molar Ratio.

108 As a conclusion, an adequate amount of methanol loading on reaction is the most significant factor for both ME yield and FFA conversion. However with the presence of moderate reaction temperature and WHSV, the ME yield and FFA conversion can be maximized.

4.3.3.4 Optimization of ME Yield

The process condition of biodiesel production from WCPO was optimized in order to obtain the highest ME yield for this system. The response surface analysis indicated that the predicted optimum ME yield was 99.55% at methanol to oil molar ratio = 27:1, reaction temperature= 153oC and WHSV = 0.79 g oil g cat-1 h-1 as tabulated in Table 4.11.

Additional experiment was carried out to validate the

optimization result obtained by the response surface analysis. The experimental and predicted ME yields are reported as 93.61 % and 99.55%, respectively, with 5.14% error as tabulated in Table 4.12. The error was considered small as the observed values was within the 5% level of significance. The standard deviation obtained from the ANOVA table is used to derive the confidence intervals. Therefore, the optimization of ME yield of WCPO transesterification with RSM studied was operating at molar ratio methanol to oil = 27:1, reaction temperature= 153oC and WHSV =0.79 g oil g cat-1 h-1. The optimum process condition is favourable since the previous studied reported that the reaction temperature is at 200oC (Sun et al., 2010, Yan et al., 2009a), and about 3h (Sun et al., 2010) and 5h (Yan et al., 2009a) reaction time with the presence of a large amount of methanol to achieve high ME yield.

109 Table 4. 11: Predicted Analysis of Optimum Condition for ME Yield

Observed

Critical

Observed

Minimum

Values

Maximum

2

27

37

Reaction temperature (oC) 63

153

187

WHSV (g oil g cat-1 h-1)

0.79

1.04

Factor

Molar ratio (MeOH:oil)

0.52

Table 4. 12: Comparison between Predicted and Experimental Responses at the Optimum Condition Obtain from RSM.

Responses

Predicted Value

Observed Value

Error (%)

Ester Yield (%)

99.55

93.61

5.14

4.3.3.5 Reusability of Catalyst

The reusability of the catalyst is studied under the recommendation optimum reaction condition; 153oC, 0.79 g oil g cat-1 h-1, and 27:1 methanol-oil molar ratio. The catalyst was reused after washing it with methanol for a few times to remove the impurities in the tube, and then calcined at 650oC for 5h in air for each cycle. Figure 4.26 illustrates the activity of Sr/ZrO2 after reused for six cycles. The activity of Sr/ZrO2 gradually decreased. The same trend was observed by Liu et al. (2007), where the biodiesel yield was slightly decreased after SrO catalyst being used for 10 times due to catalyst loss during the experiment at 65oC at 30min each time. Besides, Zabeti et al.(2010) also reported that the biodiesel yield slightly decreased after two cycles with the presence of CaO/Al2O3 catalyst.

ME yield (%)

110

100 90 80 70 60 50 40 30 20 10 0 1

2

3

4

5

6

Reusability

Figure 4. 26: ME yield of biodiesel production from WCPO at 27:1 methanol-oil methanol molar ratio, 181 min, 153oC.

4.4

Characteristic of Biodiesel

4.4.1

Observation of Biodiesel

There are two layers formed in this study as can be observed from Figure 4.27.. The upper layer is FAME (yellow in colour) and bottom is glycerol (dark colour). There are re similarities observation are observed for batch and continuous process as shown in Figure 4.27. 4.2 In previous study which homogeneous catalyst was used, the catalyst would sink onto the bottom or suspend in glycerol and the soap would form if it wass washed washe in water (Canakci, 2007, Felizardo et al., 2006, Leung and Guo, 2006, Wang et al., 2007). But in this study which iss using heterogeneous catalyst, the catalyst can be separated from another layer by filtration since the

111 catalyst is insoluble in oil or methanol. The following figure (Figure 4.28) 4.2 depict the changing colour of darker WCPO into yellowish ME.

Figure 4. 27: The Final inal Product Mixture Settle Overnight for Batch atch (left) and Continuous (right) at their Optimum Condition. C

Figure 4. 28: WCPO (left) and ME (right)

112 Meanwhile, the most methyl ester present in upper layer is shown in Figure 4.29 and tabulated in Table 4.13. As can be observed, the main ME produced in the study was 9(Z)-octadecenoic acid (oleic acid), methyl ester and hexadecanoic acid (palmitic acid), methyl ester. In addition, dodecanoic acid (lauric acid), methyl ester, octadecanoic acid (stearic acid), methyl ester, 9(Z) -hexadecenoic acid (palmitoleic acid), methyl ester and methyl tetradecanoate (myristic acid methyl ester) were formed as well. This is not surprising since they are the main component in WCPO.

Table 4. 13: The ME Component from GC-MS Analysis. Retention time

Area (%)

Library/ID

10.009

1.12

Dodecanoic acid, methyl ester

12.310

1.46

Methyl tetradecanoate

14.223

3.35

14.481

31.40

9-Hexadecenoic acid, methyl ester, (Z)Hexadecanoic acid, methyl ester

16.092

0.08

Octadecanoic acid, methyl ester

16.202

55.79

9-Octadecenoic acid (Z)-, methyl ester

16.351

5.39

9-Octadecenoic acid, methyl ester, (E)-

113

Figure 4. 29: GC Chromatograph Analysis of Upper Layer Product (ME).

114 4.4.2

Physical Properties of Biodiesel

The physical properties of biodiesel produced at predicted optimum condition were determined accordingly by ASTM method to compare quality of the product with the biodiesel standard specification ASTM 6751-02. The comparison is important to ensure that the product have the commercial value beside its have high percentage of yield. In this study, three elements of physical properties which are density, kinematic viscosity and cetane number have been tested for the sample of biodiesel produced from batch and continuous processes at predicted optimum condition, respectively. These three elements are selected since they are important parameters of fuels and roughly give reflection of fuel composition. Table 4.14 tabulates the physical properties of biodiesel.

ASTM 6751-02 standard showed the density of biodiesel was in range of 0.87g/ml and 0.89 g/ml. The property is important generally in airless combustion system because it influences the effectiveness of atomazation of the fuel (Felizardo et al, 2006). Based on the result obtained, the densities of biodiesel for both samples have the average density which is 0.87 g/ml (Table 4.14). This is because both biodiesel have very nearly the same carbon, hydrogen and oxygen contents. Therefore, the density of the biodiesel produced met with ASTM standard.

Table 4. 14: The Properties of ME.

ASTM 6751-02

Batch

Continuous

Density @150C, g/ml

0.87-0.89

0.87

0.87

Kinematic Viscosity

1.9-6.0

4.58

4.45

45-65

58

55

Physical properties

@400C,cSt Cetane number

115

The kinematics viscosity of the biodiesel was also analyzed. The kinematics viscosity is very important property due to the main objective in methanolysis of vegetable oil via transesterification or esterification process is to reduce the viscosity of vegetable oil. Based on Canakci (2007), the vegetable oil can be used in diesel engine due to their low volatility and high cetane number. However, the numerous engine-related problems will happen if the raw vegetable oil was used in the diesel engine because of it has high viscosity. Based on ASTM standard, the kinematics viscosity at 40oC must be between 1.9 and 6.0 cSt to ensure that the biodiesel can be used in diesel engine. The kinematic viscosity of the biodiesel samples that was produced in this work was laid within the range. The kinematic viscosity is 4.58 and 4.45 cSt for batch and continuous processes, respectively (Table 4.14). This indicates that the biodiesel has a good flow characteristic at lower temperature, and can be used in cold climate area without any problem. Therefore, the biodiesel that were produced from this method can be used in diesel engine without any modification.

In addition, the cetane number (CN) is important in order to improve the emission. CN rates the ignition properties of diesel fuels. It is measure the ignition delay when it is compressed. The higher value of CN offers more efficient of the fuel. Biodiesel should have a higher CN than petrodiesel because of its oxygen content. Studies have correlated the ignition quality with all the regulated emissions (Knothe, 2005a). As ignition delay is reduced, the combustion process starts earlier and emissions (primarily carbon monoxide and hydrocarbons) are reduced. Therefore, as tabulated in Table 4.14, the CN of both samples are in range of ASTM 6751-02. The value of the CN is higher than diesel fuel which is 50 (Knothe, 2005a). Thus, the biodiesel can improve the emission.

CHAPTER 5

CONCLUSIONS AND RECOMMENDATIONS

5.1

Conclusions

The alkaline modified zirconia heterogeneous catalyst which has an ability to convert simultaneously esterification and transesterification of WCPO into their corresponding alkyl-ester was successfully developed. The catalysts were prepared via wet impregnation of alkaline nitrate salts with zirconia, and characterized using XRD, FESEM, BET and CO2-NH3-TPD. The screening and catalytic activities of alkaline modified zirconia i.e. Mg/ZrO2, Ca/ZrO2, Sr/ZrO2, and Ba/ZrO2

as

heterogeneous catalyst in biodiesel production from waste cooking palm oil (WCPO) have been investigated. Among of the catalysts, Sr/ZrO2 catalyst exhibited the greatest catalytic activity for esterification and transesterification reaction in biodiesel production from WCPO. The XRD results showed that Sr/ZrO2 was successfully prepared at 650oC calcination temperature, after aging for 2hr in air with presence of Sr/ZrO2 peak while the Mg/ZrO2 and Ca/ZrO2 catalysts form a solid solution. On the other hand, Ba/ZrO2 was unsuccessfully prepared at the 650oC calcination time since the Ba(NO3)2 presence after the calcination. Besides, the physico- chemical properties of zirconia increased with the presence of alkaline metal on ZrO. The alkaline modified zirconia catalysts were defined as a mesoporous

117 catalyst which has a large pore volume and surface area which a suitable pore diameter for biodiesel production.

On the other hand, alkaline modified zirconia catalyst increased the amphotheric nature of zirconia which is the basic site of catalyst as well as acid site. Thus, the alkaline-modified zirconia catalysts have high basicity and acidity amount. The right combination of the acid-basic sites of alkaline modified catalyst which was found in Sr/ZrO2 helped in balancing the reaction to occur. Sr/ZrO2 exhibited higher catalytic activities for the simultaneous transesterification and esterification of biodiesel even though it had moderate basic and acid sites compared to other alkaline modifieds. The basic sites of Sr/ZrO2 led to transesterification reaction while the acid site led to esterification reaction of the WCPO in biodiesel production. Besides, the effects of operating process conditions such as methanol to oil ratio, reaction temperature and catalyst loading on biodiesel production in presence of Sr/ZrO2 also were investigated in a batch process.

The further study was carried out to explore the relationship of process variable i.e. methanol to oil molar ratio, catalyst loading, reaction time, and reaction temperature on the ME yield and FFA conversion in batch processes as well as to find the optimum process conditions. The study applied RSM technique which was carried out via Statistica Software. The experiments were designed using central composite design (CCD) by applying 24 full factorial designs with two centre points. Based on the experimental results obtained, all the variables; molar ratio methanol to oil, catalyst loading, reaction time and reaction temperature gave a significant effect on the heterogeneous biodiesel production from WCPO. However, interaction of reaction time and reaction temperature gave the largest effect on FFA conversion and ME yield. Thus, reaction time and reaction temperature acted as limiting parameters in batch process. 79.7% maximum methyl ester yield was produced at predicted optimum methanol to oil molar ratio = 29:1, catalyst loading = 2.7 wt%, reaction time =87 min and reaction temperature =115.5oC.

118 In order to expand the ME yield production from WCPO with the presence of Sr/ZrO2, a continuous biodiesel production in a packed bed reactor (PBR) has carried out. The experiments were performed in a stainless steel tube reactor in range of (90180)oC, (0.65-0.95) g oil g cat-1 h-1, and 10:1 to 30:1 methanol-oil molar ratio. The catalyst loading was fixed (2.7wt %) since the effect of catalyst loading was found insignificant at the range of study in batch process. CCD with 23 full factorial designs with two centre points and RSM were employed to design the experiment and to explore the effect of process variables as well as to predict the optimum process condition, respectively. An adequate amount of methanol loading on reaction was found to be the most significant factor for both ME yield and FFA conversion. However with the presence of moderate reaction temperature and reaction time, the ME yield and FFA conversion can be maximized. In addition, the reusability of Sr/ZrO2 was also studied in the continuous production. The results showed that the 93.61% of ME yield produced from the process at 153oC, 0.79 g oil g cat-1 h-1, 27:1 methanol –oil molar ratio. Moreover, the catalyst can be reused for three times. Hence, the Sr/ZrO2 catalyst was found to be an effectiveness heterogeneous catalyst for the conversion of WCPO to biodiesel.

Furthermore, the clear yellow liquid has been obtained in this study. The liquid product contained oleic acid methyl ester (C18:1) and palmitic acid methyl ester (C16:0) as a main component which was analyzed by GC-MS. In addition, the final products were found to be in reasonable agreement with ASTM standard for the important physical properties. The properties are viscosity, density and cetane number.

5.2

Recommendations

For the sake of reducing cost of the process, the research was developed a new heterogeneous catalyst which has ability to simultaneous esterification and

119 transesterification of WCPO into their corresponding alkyl-ester. The catalyst was successfully produced by impregnation of alkaline salt and zirconia. However, there are a lot of studies should be carried out in order to commercialize the type of the catalyst. Since the catalyst was prepared at one point preparation condition, the catalyst preparation condition parameters such as calcination temperature and aging time as well as metal loading should be varied to find more effectiveness of heterogeneous catalyst. Besides, catalyst preparation method such as co-precipitation or gel precipitation method should be studied as well.

In addition, the effect of FFA and water content process parameters on biodiesel production is recommended to be studied in order to understand more about the reactions. Moreover, study on several types of feedstock also can help to commercialize the system. Besides, the kinetic study should be carried out for batch and continuous processes in order to provide the information for reaction rate determination, and it easier to predict the process via stimulation.

REFERENCES

Alba-Rubio, A. C., Santamaría-González, J., Mérida-Robles, J. M., Moreno-Tost, R., Martín-Alonso, D., Jiménez-López, A. and Maireles-Torres, P. (2010). Heterogeneous Transesterification Processes by Using CaO Supported on Zinc Oxide as Basic Catalysts. Catalysis Today. 149: 281-287. Albuquerque, M. C. G., Azevedo, D. C. S., Cavalcante Jr, C. L., Santamaría-González, J., Mérida-Robles, J. M., Moreno-Tost, R., Rodríguez-Castellón, E., JiménezLópez, A. and Maireles-Torres, P. (2009). Transesterification of Ethyl Butyrate with Methanol Using MgO/CaO Catalysts. Journal of Molecular Catalysis A: Chemical. 300: 19-24. Arzamendi, G., Campo, I., Arguiñarena, E., Sánchez, M., Montes, M. and Gandía, L. M. (2007). Synthesis of Biodiesel with Heterogeneous NaOH/Alumina Catalysts: Comparison with Homogeneous NaOH. Chemical Engineering Journal. 134: 123-130. Bournay, L., Casanave, D., Delfort, B., Hillion, G. and Chodorge, J. A. (2005). New Heterogeneous Process for Biodiesel Production: A Way to Improve the Quality and the Value of the Crude Glycerin Produced by Biodiesel Plants. Catalysis Today. 106: 190-192. Canakci, M. (2007). The Potential of Restaurant Waste Lipids as Biodiesel Feedstocks. Bioresource Technology. 98: 183-190. ÇaylI, G. and Küsefoglu, S. (2008). Increased Yields in Biodiesel Production from Used Cooking Oils by a Two Step Process: Comparison with One Step Process by Using TGA. Fuel Processing Technology. 89: 118-122.

121 Chongkhong, S., Tongurai, C. and Chetpattananondh, P. (2009). Continuous Esterification for Biodiesel Production from Palm Fatty Acid Distillate Using Economical Process. Renewable Energy. 34: 1059-1063. Cornell, J. A. (1990). How to Apply Response Surface Methodology. US: Am Soc Qual Control: Statistic Devision. Demirbas, A. (2008). Comparison of Transesterification Methods for Production of Biodiesel from Vegetable Oils and Fats. Energy Conversion and Management. 49: 125-130. Di Serio, M., Tesser, R., Dimiccoli, M., Cammarota, F., Nastasi, M. and Santacesaria, E. (2005). Synthesis of Biodiesel Via Homogeneous Lewis Acid Catalyst. Journal of Molecular Catalysis A: Chemical. 239: 111-115. Di Serio, M., Ledda, M., Cozzolino, M., Minutillo, G., Tesser, R. and Santacesaria, E. (2006). Transesterification of Soybean Oil to Biodiesel by Using Heterogeneous Basic Catalysts. Industrial and Engineering Chemistry Research. 45: 3009-3014. Earthtrends Website.

http://earthtrends.wri.org/searchable_db Accessed on 30

November 2008. Felizardo, P., Neiva Correia, M. J., Raposo, I., Mendes, J. F., Berkemeier, R. and Bordado, J. M. (2006). Production of Biodiesel from Waste Frying Oils. Waste Management. 26: 487-494. Fogler, H. S. (2006). Elements of Chemical Engineering, 4th ed.Upper Sadle River, Pearson Education, Inc. Furuta, S., Matsuhashi, H. and Arata, K. (2004). Biodiesel Fuel Production with Solid Superacid Catalysis in Fixed Bed Reactor under Atmospheric Pressure. Catalysis Communications. 5: 721-723. Furuta, S., Matsuhashi, H. and Arata, K. (2006). Biodiesel Fuel Production with Solid Amorphous-Zirconia Catalysis in Fixed Bed Reactor. Biomass and Bioenergy. 30: 870-873. Gao, Y., Tan, T.-W., Nie, K.-L. and Wang, F. (2006). Immobilization of Lipase on Macroporous Resin and Its Application in Synthesis of Biodiesel in Low Aqueous Media. Chinese Journal of Biotechnology. 22: 114-118.

122 Garcia, C. M., Teixeira, S., Marciniuk, L. L. and Schuchardt, U. (2008). Transesterification of Soybean Oil Catalyzed by Sulphated Zirconia. Bioresource Technology. 99: 6608-6613. Gerpen, J. V. and Knothe, G. (2005). Biodiesel Production: Basics of the Transesterification Reaction. In: Knothe, G., Gerpen, J. V.andKrahl, J. (eds.) The Biodiesel Handbook. (pg 26-41). Urbana, Illinois: AOCS Press. Granados, M. L., Poves, M. D. Z., Alonso, D. M., Mariscal, R., Galisteo, F. C., MorenoTost, R., Santamaría, J. and Fierro, J. L. G. (2007). Biodiesel from Sunflower Oil by Using Activated Calcium Oxide. Applied Catalysis B: Environmental. 73: 317-326. Gui, M. M., Lee, K. T. and Bhatia, S. (2008). Feasibility of Edible Oil Vs. Non-Edible Oil Vs. Waste Edible Oil as Biodiesel Feedstock. Energy. 33: 1646-1653. Gerpen, J. V. and Knothe, G. (2005). Biodiesel Production: Basics of the Transesterification Reaction. In: Knothe, G., Gerpen, J. V.andKrahl, J. (eds.) The Biodiesel Handbook. (pg 26-41). Urbana, Illinois: AOCS Press. Haaland, P. D. (1989). Experimental Design in Biotechnology, Marcel Dekker Inc. Halim, S. F. A., Kamaruddin, A. H. and Fernando, W. J. N. (2009). Continuous Biosynthesis of Biodiesel from Waste Cooking Palm Oil in a Packed Bed Reactor: Optimization Using Response Surface Methodology (RSM) and Mass Transfer Studies. Bioresource Technology. 100: 710-716. Jacobson, K., Gopinath, R., Meher, L. C. and Dalai, A. K. (2008). Solid Acid Catalyzed Biodiesel Production from Waste Cooking Oil. Applied Catalysis B: Environmental. 85: 86-91. Jitputti, J., Kitiyanan, B., Rangsunvigit, P., Bunyakiat, K., Attanatho, L. and Jenvanitpanjakul, P. (2006). Transesterification of Crude Palm Kernel Oil and Crude Coconut Oil by Different Solid Catalysts. Chemical Engineering Journal. 116: 61-66. Juan, J. C., Zhang, J. and Yarmo, M. A. (2007). 12-Tungstophosphoric Acid Supported on Mcm-41 for Esterification of Fatty Acid under Solvent-Free Condition. Journal of Molecular Catalysis A: Chemical. 267: 265-271.

123 Kamaruddin, A. H., Halim, S. F. A. and Fernando, W. J. N. (2008). Lipase-Mediated Transesterifiction of Waste Cooking Palm Oil for Biodiesel Production. Proceeding of Natural Resources and Energy Environment Seminar. Kyoto, Japan. 35-43. Kim, H.-J., Kang, B.-S., Kim, M.-J., Park, Y. M., Kim, D.-K., Lee, J.-S. and Lee, K.-Y. (2004). Transesterification of Vegetable Oil to Biodiesel Using Heterogeneous Base Catalyst. Catalysis Today. 93-95: 315-320. Knežević, Z. D., Šiler-Marinković, S. S. and Mojović, L. V. (2004). Immobilized Lipases as Practical Catalysts APPTEFF. 35: 1-280. Knothe, G. (2005a). Cetane Numbers-Heat of Combustion-Why Vegetable Oils and Their Derivatives Are Suitable as a Diesel Fuel. In: Knothe, G., Gerpen, J. V.andKrahl, J. (eds.) The Biodiesel Handbook. (pg 76-80). Urbana, Illinois: AOCS Press. Knothe, G. (2005b). History of Vegetable Oil-Based Diesel Fuels. In: Knothe, G., Gerpen, J. V.andKrahl, J. (eds.) The Biodiesel Handbook. (pg 4-16). Urbana, Illinois: AOCS Press. Komers, K., Skopal, F. and Cegan, A. (2010). Continuous Biodiesel Production in a Cascade of Flow Ideally Stirred Reactors. Bioresource Technology. 101: 37723775. Kouzu, M., Kasuno, T., Tajika, M., Sugimoto, Y., Yamanaka, S. and Hidaka, J. (2008). Calcium Oxide as a Solid Base Catalyst for Transesterification of Soybean Oil and Its Application to Biodiesel Production. Fuel. 87: 2798-2806. Kusdiana, D. and Saka, S. (2004). Effects of Water on Biodiesel Fuel Production by Supercritical Methanol Treatment. Bioresource Technology. 91: 289-295. Leung, D. Y. C. and Guo, Y. (2006). Transesterification of Neat and Used Frying Oil: Optimization for Biodiesel Production. Fuel Processing Technology. 87: 883890. Liu, X., He, H., Wang, Y. and Zhu, S. (2007). Transesterification of Soybean Oil to Biodiesel Using SrO as a Solid Base Catalyst. Catalysis Communications. 8: 1107-1111.

124 Liu, Y., Loreto, E. and Jr, J. G. G. (2006). A Comparison of the Estrification of Acetic Acid with Methanol Using Heterogeneous Versus Homogeneous Acid Catalysis. Journal of Catalysis. 242. López, D. E., Suwannakarn, K., Bruce, D. A. and Goodwin Jr, J. G. (2007). Esterification and Transesterification on Tungstated Zirconia: Effect of Calcination Temperature. Journal of Catalysis. 247: 43-50. Lotero, E., Liu, Y., Lopez, D. E., Suwannakarn, K., Bruce, D. A. and Goodwin Jr, J. G. (2005). Synthesis of Biodiesel Via Acid Catalysis. Industrial and Engineering Chemistry Research. 44: 5353-5363. Ma, F. and Hanna, M. (1999). Biodiesel Production: A Review. Bioresource Technology. 70: 1-15. Marchetti, J. M. and Errazu, A. F. (2008). Esterification of Free Fatty Acids Using Sulfuric Acid as Catalyst in the Presence of Triglycerides. Biomass and Bioenergy. 32: 892-895. Marchetti, J. M., Miguel, V. U. and Errazu, A. F. (2007). Possible Methods for Biodiesel Production. Renewable and Sustainable Energy Reviews. 11: 1300-1311. Masjuki, H. H., Kalam, M. A. and Shioji, M. (2008). High Performance Gas Engine with Direct Injection. Proceeding of Natural Resources and Energy Environment Seminar. Kyoto, Japan. 198-209. Meng, X., Chen, G. and Wang, Y. (2008). Biodiesel Production from Waste Cooking Oil Via Alkali Catalyst and Its Engine Test. Fuel Processing Technology. 89: 851-857. Narasimharao, K., Lee, A. and Wilson, K. (2007). Catalyst in Production of Biodiesel: A Review. Biobased Materials and Bioenergy. 1: 19-30. Nie, K., Xie, F., Wang, F. and Tan, T. (2006). Lipase Catalyzed Methanolysis to Produce Biodiesel: Optimization of the Biodiesel Production. Journal of Molecular Catalysis B: Enzymatic. 43: 142-147. Noiroj, K., Intarapong, P., Luengnaruemitchai, A. and Jai-In, S. (2009). A Comparative Study of KOH/Al2O3 and KOH/NaY Catalysts for Biodiesel Production Via Transesterification from Palm Oil. Renewable Energy. 34: 1145-1150.

125 Özbay, N., Oktar, N. and Tapan, N. A. (2008). Esterification of Free Fatty Acids in Waste Cooking Oils (WCO): Role of Ion-Exchange Resins. Fuel. 87: 1789-1798. Park, Y. M., Lee, D. W., Kim, D. K., Lee, J. S. and Lee, K. Y. (2008). The Heterogeneous Catalyst System for the Continuous Conversion of Free Fatty Acids in Used Vegetable Oils for the Production of Biodiesel. Catalysis Today. 131: 238-243. Park, Y. M., Chung, S. H., Eom, H. J., Lee, J. S. and Lee, K. Y. (2010a). Tungsten Oxide Zirconia as Solid Superacid Catalyst for Esterification of Waste Acid Oil (Dark Oil). Bioresource Technology. 101: 6589-6593. Park, Y. M., Lee, J. Y., Chung, S. H., Park, I. S., Lee, S. Y., Kim, D. K., Lee, J. S. and Lee, K. Y. (2010b). Esterification of Used Vegetable Oils Using the Heterogeneous WO3/ZrO2 Catalyst for Production of Biodiesel. Bioresource Technology. 101: S59-S61. Peng, B. X., Shu, Q., Wang, J. F., Wang, G. R., Wang, D. Z. and Han, M. H. (2008). Biodiesel Production from Waste Oil Feedstocks by Solid Acid Catalysis. Process Safety and Environmental Protection. 86: 441-447. Peters, T. A., Benes, N. E., Holmen, A. and Keurentjes, J. T. F. (2006). Comparison of Commercial Solid Acid Catalysts for the Esterification of Acetic Acid with Butanol. Applied Catalysis A: General. 297: 182-188. Phan, A. N. and Phan, T. M. (2008). Biodiesel Production from Waste Cooking Oils. Fuel. 87: 3490-3496. Peterson, C. L. and Möller, G. (2005). Biodiesel Fuels: Biodegradability, Biological and Chemical Oxygen Demand, and Toxicity. In: Knothe, G., Gerpen, J. V.andKrahl, J. (eds.) The Biodiesel Handbook. (pg 145-160). Urbana, Illinois: AOCS Press. Royon, D., Daz, M., Ellenrieder, G. and Locatelli, S. (2007). Enzymatic Production of Biodiesel from Cotton Seed Oil Using t-Butanol as a Solvent. Bioresource Technology. 98: 648-653. Rack Sohn, J., Kwon, T. D. and Kim, S. B. (2001). Characterization of Zirconium Sulfate Supported on Zirconia and Activity for Acid Catalysis. Bulletin of the Korean Chemical Society. 22: 1309-1315.

126 Saka, S. and Kusdiana, D. (2001). Biodiesel Fuel from Rapeseed Oil as Prepared in Supercritical Methanol. Fuel. 80: 225-231. Samart, C., Sreetongkittikul, P. and Sookman, C. (2009). Heterogeneous Catalysis of Transesterification of Soybean Oil Using KI/Mesoporous Silica. Fuel Processing Technology. 90: 922-925. Schuchardt, U. M. (1998). Transesterification of Vegetable Oils: A Review. J. Braz. Chem. Soc. 1: 199-210. Schulte, W. B. (2007). Biodiesel Production from Tall Oil and Chicken Fat Via Supercritical Methanol Treatment. University of Arkansas:Master. Sharma, Y. C., Singh, B. and Upadhyay, S. N. (2008). Advancements in Development and Characterization of Biodiesel: A Review. Fuel. 87: 2355-2373. Shibasaki-Kitakawa, N., Honda, H., Kuribayashi, H., Toda, T., Fukumura, T. and Yonemoto, T. (2007). Biodiesel Production Using Anionic Ion-Exchange Resin as Heterogeneous Catalyst. Bioresource Technology. 98: 416-421. Solomons, T. W. G. and Fryhle, C. B. (1998). Organic Chemistry, 7th ed.new york, John Wiley & Sons,Inc. Sree, R., Seshu Babu, N., Sai Prasad, P. S. and Lingaiah, N. (2009). Transesterification of Edible and Non-Edible Oils over Basic Solid Mg/Zr Catalysts. Fuel Processing Technology. 90: 152-157. Srilatha, K., Lingaiah, N., Devi, B. L. A. P., Prasad, R. B. N., Venkateswar, S. and Prasad, P. S. S. (2009). Esterification of Free Fatty Acids for Biodiesel Production over Heteropoly Tungstate Supported on Niobia Catalysts. Applied Catalysis A: General. 365: 28-33. Srinegar, T. B. (2005). Catalytic Cracking of Palm Oil to Gasoline Using Zeolite Catalysts. Universiti Teknologi Malaysia:Master Sun, H., Ding, Y., Duan, J., Zhang, Q., Wang, Z., Lou, H. and Zheng, X. (2010). Transesterification of Sunflower Oil to Biodiesel on ZrO2 Supported La2O3 Catalyst. Bioresource Technology. 101: 953-958. Sunita, G., Devassy, B. M., Vinu, A., Sawant, D. P., Balasubramanian, V. V. and Halligudi, S. B. (2008). Synthesis of Biodiesel over Zirconia-Supported Isopoly and Heteropoly Tungstate Catalysts. Catalysis Communications. 9: 696-702.

127 Suppes, G. J., Dasari, M. A., Doskocil, E. J., Mankidy, P. J. and Goff, M. J. (2004). Transesterification of Soybean Oil with Zeolite and Metal Catalysts. Applied Catalysis A: General. 257: 213-223. Tan, K. T., Gui, M. M., Lee, K. T. and Mohamed, A. R. (2010). An Optimized Study of Methanol and Ethanol in Supercritical Alcohol Technology for Biodiesel Production. The Journal of Supercritical Fluids. 53: 82-87. Ting, W.-J., Huang, C.-M., Giridhar, N. and Wu, W.-T. (2008). An Enzymatic/AcidCatalyzed Hybrid Process for Biodiesel Production from Soybean Oil. Journal of the Chinese Institute of Chemical Engineers. 39: 203-210. Tsai, W.-T., Lin, C.-C. and Yeh, C.-W. (2007). An Analysis of Biodiesel Fuel from Waste Edible Oil in Taiwan. Renewable and Sustainable Energy Reviews. 11: 838-857. van Kasteren, J. M. N. and Nisworo, A. P. (2007). A Process Model to Estimate the Cost of Industrial Scale Biodiesel Production from Waste Cooking Oil by Supercritical Transesterification. Resources, Conservation and Recycling. 50: 442-458. Veljkovic´, V. B., Lakic´evic´S.H., Stamenkovic´O.S., Todorovic´Z.B. and Lazic, M. L. (2006). Biodiesel Production from Tobacco (Nicotiana Tabacum L.) Seed Oil with a High Content of Free Fatty Acids. Fuel. 85: 2671-2675. Vicente, G., Coteron, A., Martinez, M. and Aracil, J. (1998). Application of the Factorial Design of Experiments and Response Surface Methodology to Optimize Biodiesel Production. Industrial Crops and Products. 8: 29-35. Wang, Y., Pengzhan Liu, S. O. and Zhang, Z. (2007). Preparation of Biodiesel from Waste Cooking Oil Via Two-Step Catalyzed Process. Energy Conversion and Management. 48: 184-188. Wang, Y., Huang, W. Y., Wu, Z., Chun, Y. and Zhu, J. H. (2000). Superbase Derived from Zirconia-Supported Potassium Nitrate. Materials Letters. 46: 198-204. Wang, Y., Ou, S., Liu, P., Xue, F. and Tang, S. (2006). Comparison of Two Different Processes to Synthesize Biodiesel by Waste Cooking Oil. Journal of Molecular Catalysis A: Chemical. 252: 107-112.

128 Warabi, Y., Kusdiana, D. and Saka, S. (2004). Biodiesel Fuel from Vegetable Oil by Various Supercritical Alcohols. Applied biochemistry and biotechnology. 113116: 793-801. Wen, Z., Yu, X., Tu, S.-T., Yan, J. and Dahlquist, E. (2010). Synthesis of Biodiesel from Vegetable Oil with Methanol Catalyzed by Li-Doped Magnesium Oxide Catalysts. Applied Energy. 87: 743-748. Xie, W., Peng, H. and Chen, L. (2006). Transesterification of Soybean Oil Catalyzed by Potassium Loaded on Alumina as a Solid-Base Catalyst. Applied Catalysis A: General. 300: 67-74. Yagiz, F., Kazan, D. and Akin, A. N. (2007). Biodiesel Production from Waste Oils by Using Lipase Immobilized on Hydrotalcite and Zeolites. Chemical Engineering Journal. 134: 262-267. Yan, S., Salley, S. O. and Simon Ng, K. Y. (2009a). Simultaneous Transesterification and Esterification of Unrefined or Waste Oils over Zno-La2o3 Catalysts. Applied Catalysis A: General. 353: 203-212. Yan, S., Kim, M., Steven, O. S. and Simon Ng, K. Y. (2009b). Oil Transesterification over Calcium Oxides Modified with Lanthanum. Applied Catalysis A: General. 360: 163-170. Yang, Z. and Xie, W. (2007). Soybean Oil Transesterification over Zinc Oxide Modified with Alkali Earth Metals. Fuel Processing Technology. 88: 631-638. Zhang, Y., Dubé, M. A., McLean, D. D. and Kates, M. (2003). Biodiesel Production from Waste Cooking Oil: 1. Process Design and Technological Assessment. Bioresource Technology. 89: 1-16. Zabeti, M., Daud, W. M. A. W. and Aroua, M. K. (2010). Biodiesel Production Using Alumina-Supported Calcium Oxide: An Optimization Study. Fuel Processing Technology. 91: 243-248.

APPENDIX A

EXAMPLES CALCULATIONS OF ME YIELDS AND CONVERSION

A. FFA Conversion

AV of WCPO = 5.08 AV of Upper layer = 2.60

FFA Conversion =

5.08 − 2.60 × 100 5.08

= 48.73%

B. ME yield

Total area of ME from GCMS=73.08%=0.7308 weight of oil = 20g Weight of upper layer=16.3g

ME yield =

0.7308 × 16.3 × 100 20

= 59.56%

APPENDIX B

CALCULATIONS OF CRYSTALLITE SIZE OF ZIRCONIA

The mean crystallite size (Dβ) of the zirconia species of alkaline modified are determined from the highest line-broadening peak of the catalyst, using the Scherer equation,

‫ܦ‬ఉ =

‫ߣܭ‬ ߚ ܿ‫ߠݏ݋‬

where λ is the synchrotron wavelength, K is a particle shape factor, taken as 0.94 for spherical particles, β is the full-width at half maximum height (FWHM) in radians and θ is the diffraction angle.

Example calculations of the crystallite size of zirconia species detected in the Sr/ZrO2 catalyst: K

=

0.94

λ

=

1.54 Å (for Cu-Kα radiation)

β

=

0.2o

131 π

=

0.2° ×

=

0.0034911



=

28.243

θ

=

14.1215

cos θ

=

0.9698

Hence, the crystallite size of ZrO2

180°

଴.ଽସ × ଵ.ହସ

= ଴.଴଴ଷସଽଵଵ ×଴.ଽ଺ଽ଼ = 427.5655 Å = 42.756 nm

The summary of calculations is tabulated in Table A.1.

Table A 1: Summary calculations of crystallite size of zirconia

Catalysts

β

Β (rad)



θ

Cos θ

Saiz Å

nm

ZrO2

0.19

0.00331656

28.218

14.109

0.9698

450.0690

45.0069

Mg/ZrO2

0.20

0.00349111

28.193

14.0965

0.9699

427.5215

42.75656

Ca/ZrO2

0.20

0.00349111

28.232

14.116

0.9698

427.5656

42.75215

Sr/ZrO2

0.20

0.00349111

28.243

14.1215

0.9698

427.5656

42.75656

Ba/ZrO2

0.15

0.00261833

36.318

18.159

0.9502

581.8467

58.18468

APPENDIX C

TEMPERATURE PROGRAMMED DESORPTION (TPD) FLOWSHEET

133 A) NH3-TPD FOR ACIDITY DETERMINATION

TPD/R/O 1100

Thermo

Electron

Standard Data Report Run Nr.:538 File: C:\Data1\Prof Taufiq\UTM-Yani\TPD-NH3\Analysis\Mg_ZrO2.110 Comment: Operator: aqil Room Temperature 26°C Atmospheric Pressure 1000hPa

Sample Producer: yana-UTM Name: Mg/ZrO2 Mass: 0.2178 g Info: Preparation:

Sample-Code: 0 Customer-Code: 0 Support: Metals: 0

Pretreatment Name: Pretreatment N2 Info: On Instrument: Instrument 1 with Ser.Nr.20022899 on Right Oven Started: 4/30/2010 at 2:00:51 PM finished 2:43:53 PM

Phase With Gas T [°C] Hold for [min] Cleaning Nitrogen 1: Nitrogen 2: Off 3: Off 4: Off

Flow [ccm/min] Start at T [°C] Ramp[°C/min] Stop at 20 20

Off Off

5 30

0

End Pretreatment with Oven Off

TPD/R/O Method Name: TPD-NH3analysis Info: On Instrument: Instrument 1 with Ser.Nr.20022899 on Right Oven Started: 4/30/2010 at 3:26:30 PM finished 5:53:42 PM Gas Port when Ready: (b) Helium Gas Port when End: (b) Helium Sample rate: 1s Gain: 10 Polarity: Positive

[°C]

With Gas Hold for [min] Helium

Flow [ccm/min] Start at T [°C]

Ramp°C/min Stop at T

20

10

Results Amount gas adsorbed:

2349.95146 µmol/g

50

900

60

134

Baseline Start at 6.4579 min 812.75362 mV. Stop at 124.1683 min 937.10145 mV

Calibration Use Calibration Factor: 8.601615 *10e-7 mmol/mVs

Peaks #

Start [min]

Stop [min] Maximum [min]

T [°C]

Integral [mVs]

71.2500 40.0830 67.91 114.8000 85.0330

439

404060.81

884

190966.31

[µmol/g]

[%]

1 4.6167 1595.76470 2 71.8330 32.09

754.18673

135 B) CO2-TPD FOR BASICITY DETERMINATION

TPD/R/O 1100

Thermo

Electron

Standard Data Report Run Nr.:1260 File: C:\Data1\Dr Taufiq\UTM-Yani\SAMPLE 3.110 Comment: Operator: Suziana Room Temperature 26°C

Atmospheric Pressure 1000hPa

Sample Producer: YANI-UTM Name: Mg/ZrO2 Mass: 0.2067 g Info: Preparation:

Sample-Code: 0 Customer-Code: 0 Support: Metals: 0

Pretreatment Name: TPD CO2-Pretreatment On Instrument: TPDRO 1100 with Ser.Nr.20022899 on Left Oven Started: 11/18/2009 at 1:24:57 PM finished 3:48:42 PM

Phase With Gas T [°C] Hold for [min] Cleaning Nitrogen 1: Nitrogen 2: Carbon Dioxide 3: Nitrogen 4: Off

Info:

Flow [ccm/min] Start at T [°C] Ramp[°C/min] Stop at 20 20 30 20

Off Off Off Off

30 1

5 10 60 30

250 50

End Pretreatment with Oven Off

TPD/R/O Method Name: TPD CO2 On Instrument: TPDRO 1100 with Ser.Nr.20022899 on Left Oven Started: 11/18/2009 at 4:16:05 PM finished 5:52:29 PM Gas Port when Ready: (b) Helium Gas Port when End: (b) Helium Sample rate: 1s Gain: 10 Polarity: Positive

[°C]

With Gas Hold for [min] Helium

Info:

Flow [ccm/min] Start at T [°C]

Ramp°C/min Stop at T

30

10

50

900

10

136

Results Amount gas adsorbed:

36.10499 µmol/g

Baseline Start at 18.1298 min -2.14493 mV. Stop at 91.9847 min -4.92754 mV

Calibration Use Calibration Factor: 7.982650 *10e-7 mmol/mVs

Peaks #

Start [min]

Stop [min] Maximum [min]

T [°C]

Integral [mVs]

[µmol/g]

38.5500

30.5670

344

5091.05

19.66138

54.2000

45.7670

495

2350.51

9.07757

87.2170

77.2500

807

1907.34

7.36604

[%]

1 22.5170 54.46 2 38.1670 25.14 3 69.2670 20.40

APPENDIX D

RESPONSE SURFACE METHODOLOGY

B.1

Design of Experiment

DOE is a collection of encoded settings of the process variables. Each process variables is called an experimental factor. Each combination of settings for the process variables is called a run and a measure of process performance is called a response. The explanatory variable which is selected and the values to be used during the actual experimentation have been recognized as DOE spreadsheet.

For RSM study, a Box-Wilson Central Composite design, commonly called a central composite design (CCD) is effective instead of a Box-Behnken design in order to design the experiment. The CCD consists of 2-level full factorial design (2k vertices of a k-dimensional “cube”) coded as ±1, star point (2k vertices of a kdimensional “star”) coded as ±α and center point replicates (n0≥1) coded as 0. Figure B.1 shows graphically the structure of CCD for three variables.

138

Figure B.1: Generation of a central composite design for three variables

B.2

Generating Of Mathematical Model

Then, analysis of data will generate the mathematical model in order to explain the relationship of each variable and then optimize the process. Normally, the full quadratic model del of response is established by using the method of least squares is employed:



y    ∑   β     β   ∑ 



β  

(B.1)

with y being the predicted response whilst xi is the coded factor value, βo is the offset term, βi, is the linear terms, βii the squared terms, and βij is the interaction terms.

139 B.3

Validity of Model

The model will be test in order to check their validity. There are three type of checking that is:

a. The fit quality of the model can also be checked from their Coefficient of Correlation (R) and Coefficient of Determination (R2)

 Coefficient of Correlation (R) reveals acceptability about the correlation between the experimental and predicted values from the model.  Coefficient of Determination (R2) reveals a proportion of total variation of the observed values of activity (Yi) about the mean explained by the fitted model

R2=SSR/SST

(B.2)

where: SSR= sum of square of regression SST= total sum of square

b. The adequacy of the fitted model is checked by ANOVA (Analysis of Variance) using Fisher F-test

 The F-value is a measurement of variance of data about the mean based on the ratio of mean square (MS) of group variance due to error.

F-value =

MS regression MSresidual



SSR/DFregression SSE/DFresidual

(B.3)

140 where: SSR= sum of square of regression SSE= sum of square of error/residual DFregression=degree of freedom of regression DFresidual=degree of freedom of residual

 The F-value is compare to F table (Fp−1,N−p,α)) at significant level of confident where p−1 is DFregression, N−p is DFresidual and α-value is level of significant.  In general, the calculated F-value should be greater than the tabulated F-value to reject the null hypothesis, where all the regression coefficients are zero.

c. The significance of the model parameters is assessed by p-value and t-value.  T-Value is measure how large the coefficient is in relationship to its standard error

T-value = coefficient/ standard error

(4.4)

 P-value is an observed significance level of the hypothesis test or the probability of observing an F-statistic as large as or larger than Fvalue.  The small values of p-value  the null hypothesis is not true.

141 B.4 Illustrating the Mathematical Model

The effect of the combination of process variable on overall response based on mathematical model can be interpreted by three- dimensional surface and/or twodimensional contour plots in RSM study. The plot illustrates a response as a function of two independent variables for experimental range considered. The two independent variables are representing on two of axes (x-axis and y-axis) and response desirability is representing on the third axis (z-axis). The level of response is representative by colour or types of line for both type of graphic (surface and contour plot). In 3D surface plots, z-axis is clearly shown instead of in 2D contour plot. In 2D contour plots, the z-axis is represented by the region of contour plot. The graphic feature of contour plot may interpret the meaning of the relationship for two independent variables on the response.

APPENDIX E

PUBLICATIONS

Paper

W.N.N. Wan Omar, N. Nordin, M.Mohamed and N.A.S. Amin. (2009). A TwoStep Biodiesel Production from Waste Cooking Oil: Optimization of Pre-Treatment Step. Journal of Applied Science. 9 (17): 3098-3103. S.E.E. Misi, W.N.N. Wan Omar, and N.A.S. Amin. (2010). Heterogeneous Esterification of Free Fatty Acid to Biodiesel. The Journal of the Institution of Engineers, Malaysia 71 (3):35-45. W.N.N. Wan Omar and N.A.S. Amin (2011). Optimization of Heterogeneous Biodiesel Production from Waste Cooking Palm Oil via Response Surface Methodology. Biomass and Bioenergy 35: 1329-1338. W.N.N. Wan Omar and N.A.S. Amin (2011). Biodiesel Production from Waste Cooking Palm Oil over Alkaline Modified Zirconia Catalyst. Has been submitted to Fuel Processing Technology Journal.

143

W.N.N. Wan Omar and N.A.S. Amin (2011). Continuous Biodiesel Production from Waste Cooking Palm Oil. To be submitted to Renewable Energy Journal.

Proceeding

W.N.N. Wan Omar, N. Nordin, M.Mohamed and N.A.S. Amin. (2009). A TwoStep Biodiesel Production from Waste Cooking Oil: Optimization of Pre-Treatment Step. Proceeding of 3rd International Conference on Chemical and Bioprocess Engineering in conjunction with 23rd Symposium of Malaysian Chemical Engineer (SOMChE 2009).Kota Kinabalu, Sabah, Malaysia.

Poster

W.N.N. Wan Omar and N.A.S. Amin. (2010). Continuous Biodiesel Production from Waste Cooking Palm Oil in a Packed-bed Reactor. Poster presentation of 1st National Conference on Natural Resources (NCNR 2010). Kota Bharu, Kelantan.