Diss. ETH No 16399. Quantification of Evolved Species in. Hyphenated Thermal
Analysis -. MS -. FTIR Spectroscopy Systems. A dissertation submitted to the.
Research Collection
Doctoral Thesis
Quantification of evolved species in hyphenated thermal analysis - MS-FTIR spectroscopy systems Author(s): Eigenmann, Florian Publication Date: 2005 Permanent Link: https://doi.org/10.3929/ethz-a-005124797
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ETH Library
Diss. ETH No 16399
Quantification of Evolved Species in
Hyphenated MS
-
FTIR
Thermal
Analysis
Spectroscopy Systems
A dissertation submitted Swiss Federal Institute of Technology Zurich
for the
-
degree
to
the
(ETH)
of Doctor of Technical Sciences
presented by
Florian
Eigenmann
Dipl. Chem.-Ing. born 5
ETH
July
1973
citizen of Waldkirch
(S G)
accepted on
the recommendation of
Prof. Dr. A. Baiker, examiner Prof. Dr. M. MorbidelU, co-examiner
2005
Seite Leer
/1
Blank leaf
\
dedicated to the
allowing to
reference samples
measure
the
difference...
Seite Leer / Blank leaf
Acknowledgment
I would like
Firstly,
for his support, both
plete port
express my sincere
to
gratitude
and this work whenever it
was
Prof. Dr. Alfons Baiker
and the
personally and scientifically,
my doctoral thesis in his group. I very much me
to
opportunity
appreciate no matter
necessary,
his efforts
to com¬
to
sup¬
how difficult the
circumstances.
Moreover, I would like
ing the duty of the
thank Prof. Dr. Massimo Morbidelli for accept¬
to
co-examiner in this thesis.
I furthermore thank Dr. Marek
his valuable like
suggestions
teacher and
a
and the
mentor
as
to
and very valuable
help
in
Special
Emmerich
Many Dr. Marco
during the being
acknowledge
generating
are
to
Burgener
Dr.
in
Andy Gisler,
by
turn
to
"ups
numerous
to me
(Bruker) and
settling
discussion and the
Rager (Bruker),
Netzsch GmbH
(Germany).
Dr. Wolf-Dieter
the TA-FTIR system.
Dr. Nikiaus
and Stefan Hannemann for
last years, but also the
friends I could
Gast
Jürgen
(Netzsch) for their support to
Dr. Albrecht
solutions offered
also due
thanks go
was
lots of fabulous ideas, which
the continuous interest,
suggestions given by
solving experimental thanks
the last years. He
big help during
well
for constructive discussions,
experimental investigations.
resulted in several successful I would like
Maciejewski
Künzle, Dr. Leo Schmid,
sharing
not
only
an
office
and downs" of a doctoral thesis and for
in order
to
discuss both scientific and
general
VI
topics. Additionally
sphere. Especially ing
members for
Frauchiger, Nils
van
I thank the whole
I would like
spending
Dr. Markus
a
Rohr,
to
my efforts
to
acknowledge
Ramin for the careful
rereading
ETH and
often
was
cial thank is due
to
Achter (Students
unforgettable joining
my
an
rowing
and
moments.
RowingClasses
Keresszegi, Erika Wolf,
sport
success
Zusammenfassung.
was an
contrast to
important
part of my time
scientific research, Therefore
to
a
thank also all the
in ASVZ and
lot
of
crew
World Record
hold in 2004
largest RowingClass,
spe¬
a
Poly-
times
and
members who
were
good
especially Kaspar Egger rowing ideas,
the
at
members of the GC-Achter 00-05 and the
Iten for their support in many of my crazy
with the
show
Jan-Dierk Grunwaldt and Micha
Professors) for sharing I wish
the follow¬
mates
Opre stop smoking will
also Dr.
of the
essential
the
atmo¬
Micha Ramin and Simon Diezi. In addition I
make Zsuzsanna
daily business,
pleasant
time in and outside the ETH: Dr. Simon
Dr. Reto Hess, Dr. Csilla
also in the future. I
Besides the
for the
mention besides my office
good
Vegten, Ronny Wirz,
whish, that
Baiker-group
such at
and Heiner
as
a
Guinness
the ETH
by
121
rowers.
Finally,
I would like
throughout all
to
thank my
family
these years of my education.
and my friends for their support
Seite Leer / Blank leaf
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Table of Contents
1
Acknowledgment
v
Table of Contents
ix
Summary
xiii
Zusammenfassung
xvü
Introduction 1.1
General
1
Aspects
of Thermal
Analysis
1.1.1
Thermogravimetry (TG)
1.1.2
Differential Thermal
1 2
Analysis (DTA)
and Differential
Calorimetry (DSC) 1.2
2
3
Hyphenated Techniques
2
in Thermal
1.2.1
Mass
1.2.2
Fourier Transform Infrared
Analysis
Spectrometry (MS)
1.3
Pulse Thermal
1.4
Scope
1.5
References
Scanning 3 4
(FTIR) Spectroscopy
Analysis
6 7
of this Thesis
7 8
Experimental
15
2.1
Simultaneous Thermal
2.2
Hyphenated
2.3
Pulse Thermal
Analysis
Evolved Gas
Analysis
Analysis
Quantitative Calibration of
FTIR
15 17
19
Spectroscopic Signals
25
3-1
Introduction
25
3.2
Experimental
28
3.2.1
Pulse Calibration
29
X
3.3
3.2.2
Pinhole Calibration
30
3.2.3
Differential Calibration
30
Results and Discussion
31
3-3.1
Quantification
of FTIR
Signals Using
Gases
3-3.2
Quantification
of FTIR
Signals by Liquids
3.3.3
Quantification
of FTIR
Signals Using
3.3.4
Comparison
31 37
Solids
51
of the Calibration Methods
54
3.4
Conclusions
56
3.5
References
57
4 Influence of
Measuring
Conditionson the
Quantification of
FTIR
Signals
61
4.1
Introduction
61
4.2
Experimental
64
4.3
Results and Discussion
65
4.3.1
Influence of Sample Mass and Concentration of the Gas
4.3.2
Influence of Parameters of Data-Acquisition and Carrier Gas ..69
66
4.4
Conclusions
81
4.5
References
82
5 Gas
Adsorption
Studied
on
Zeolites
85
5.1
Introduction
85
5.2
Experimental
88
5.3
Results
89
5.3.1
Influence of Thickness of Adsorbent Bed
90
5.3.2
Influence of Temperature
92
5.3.3
Influence of Carrier Gas Flow
95
5.3.4
Determination of the
Adsorption
Heat
97
5.4
Discussion
100
5.5
Conclusions
104
5.6
References
105
6 Selective
Catalytic
Oxides 6.1
Introduction
Reduction of NO
by NH3
over
Manganese-Cerium
Mixed 109 109
XI
6.2
Experimental
Ill
6.3
Results and Discussion
113
Behavior
6.3.1
Adsorption
6.3.2
Redox Behavior
6.3.3
Catalytic Activity
114 119
in SCR
123
6.4
Conclusions
131
6.5
References
132
Final Remarks
135
List of Publications
139
Curriculum Vitae
143
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Summary
In
thermoanalytical investigations
gas-solid
reactions
processes
or
potential
of simultaneous
species, such
of the
pulse
calibration
by relating
quantity of probe So to
thermogravimetry-mass
the
mass
was
only applied
quantitative
and
to
signals
FTIR was
or
FTIR
thermo-
or
the introduction
provides
qualitative analysis was
analyzed species,
concentration of the on
improved by
of
signals
a
to
quantitative
injected
the
combined TA-MS and its extension
thesis. Furthermore the influence of several
gas
spectrometry
This method
spectrometric
qualitative analysis
gas.
far, PulseTA®
TA-FTIR for
as
the
techniques, enabling
analysis (PulseTA®).
thermal
of the
systems. The
multi-component
in
occurring
spectroscopy has been further
gravimetry-FTIR
composition
important, especially when investigating decomposition
evolved gases is very
evolved
the determination of the
signals
checked
has been
them
experimental
parameters such
temperature and flow
investigated.
by relating
the main target of this
to
The
the
reliability
amount
rate
as
of the carrier
of quantifying FTIR
of evolved gases measured
bythermogravimetry. Comparisons zation of several
which as a
was not
with
a mass
important
significantly
reference for
spectrometer in tandem allowed
precise optimi¬
parameters for FTIR spectroscopy. MS
affected
assessing the
by
the
experimental conditions,
accuracy of quantification
by FTIR.
analysis, was
The
used
quanti-
XIV
fication
of the
(NaHC03)
or
spectroscopic signals
dehydration (CuS04
5
•
verified
was
the
by
decomposition
of compounds with well known
H20)
stoichiometry. The linear
dependence
tion of FTIR data.
vaporization
of
Systematic
tional calibration
studies
(varying
For the
stream.
several methods, of
pulse
calibration and
applying different organic liquids
applied tion of
on
nitrogen
by
studying adsorption
rier gas
provided
processes. The
of FTIR two
the
as a
and
as
probe
same
concentration of the
desorption
temperature
experimental
gases)
of
signals
methods based
to
gas
rate
of
to
at
either or,
as
conven¬
mentioned
liquids, the
on
we
car¬
applied
evaporation
were
studied
the
was
and selective reduc¬
atmospheric
investigate
analysis
acidity of a
widely applied.
cat¬
PulseTA
pressure. Continu¬
molecules in the
dynamics
physisorbed species
car¬
of physisorption
is shown
to
depend
on
bed. An
important advantage of
methods,
is that pretreatment of
sample
programmed desorption Integral
by
gas into the
determine the
pulsed probe
classical volumetric
set-up.
isothermal
on
thermal
adsorption
to
adsorbent, determination of the kind and as
possible
calibrating
molecule is
desorption
opportunity
PulseTA®, compared
well
is
quantifica¬
water.
such
carrier gas flow and thickness of the
the
of the
ammonia. In order
of ammonia
monitoring of the
ous
signals
and the
range of in situ calibra¬
quantification, pulse
catalytic studies,
oxides
alyst, adsorption allows
and
these methods of
in different
method based
concentrations of target
quantification
liquids
enabled easy
application
amount
of
amount
and differential calibrations. These methods
liquids: pinhole
Based
a new
of FTIR
quantification
above, by the injection of a known rier gas
on
further widen the
liquids
tions. For gases the
injected
spectroscopic signals (peak area)
of
integral intensity
between the
heats of
amount
can
of preadsorbed gases,
all be carried
adsorption
out
and the
using
amount
as
the of
XV
chemisorbed ammonia
were
found
agree well with values
to
in litera¬
reported
ture.
Finally gen oxides
TA-FTIR-MS
by
ammonia
responding metal their
catalytic ered
a
nitrates
using the
Mn/(Mn+Ce)
by NH3.
clear correlation between the
mixed oxide
catalyst
a
and
measurements
ments
(NOx, NH3)
NH3 of the
are
adsorbed
reactants
that there
on
showed similar
was
no
indicated that
at
concern¬
uncov¬
properties
and the
found for
adsorption
uptakes
was
studies indicated
adsorption
separate
measure¬
interference between adsorbed
reactants.
100-150 °C
NOx
cor¬
PulseTA
on
separate sites. Consecutive
investigations by changing the
whereas adsorbed
tions used.
investigated
of these
dependence
from the
behavior in the selective
These studies based
showed
no
as
sequence of admittance of reactants
nitrogen
Rideal type mechanism where adsorbed ammonia
phase,
prepared
molar ratio Mn/(Mn+Ce) of 0.25, whereas the activity
indicating
Mechanistic
were
composition. Highest activity to nitrogen formation was
with
NOx
reduction of nitro¬
mixed oxides. Mixed oxide
properties and
much lower for the pure constituent oxides. The that
catalytic
citric acid method and
redox
adsorption behavior, reduction of NOx
in selective
manganese-cerium
over
with different molar ratio
catalysts
ing
applied
was
formation follows
reacts
with
NOx
significant reactivity
an
Eley-
in the gas
under condi¬
Seite Leer / Blank leaf
Zusammenfassung
In
thermoanalytischen Untersuchungen
gas
analysis, EGA)
sehr
wichtig,
ist die
Analyse
der
Untersuchugen
insbesondere bei
setzungsvorgängen oder Gas-Feststoff-Reaktionen, die auftreten. Das Potential tative
Analyse
kombinierten trie-FTIR
von
gasförmigen
wurde durch die
erweitert. Diese Methode
Bisher wurde die PulseTA
wendet. Das
quantitative
quali¬
Produkte mit Hilfe der
Signale
Einführung
ermöglicht
mit der
Hauptziel und
nur
der
eine
Pulsthermoanalyse
quantitative
eingespritzten Menge
dieser Arbeit
qualitative Analyse.
in kombinierten TA-MS war
die
Temperatur
und der
Kalibri¬
des Prüf¬
der FTIR
Signale
wurde
der entwickelten Gase
wurden.
zu
bezog,
TA-FTIR für die
des
Trägergases
auf die
Zuverlässigkeit der Quantifi¬
indem
die durch
ange¬
analysierenden Komponenten,
untersucht. Die
überprüft,
zu
Systemen
einiger wichtiger experimen¬
Strömungsgeschwindigkeit
Signale wurde systematisch
zierung
Erweiterung
Der Einfluss
teller Parameter, wie der Konzentration der
Menge
Mehrstoffsystemen
in
Beziehung gebracht werden.
gases in
FTIR
Zer¬
Thermogravimetrie-Massenspektrometrie oder Thermogravime-
erung, indem MS oder FTIR
der
von
kombinierten Techniken, insbesondere die
der sich entwickelnden
Spektroskopie
(PulseTA®)
Gasphase (evolved
man
die
Signale
Thermogravimetrie
auf die
gemessen
XV111
Vergleiche
mierung einiger wichtiger experimenteller pie.
Die MS
Analyse,
gen beeinflusst
der
welche nicht
Signale
(Q1SO4
Die lineare
glichte
von
integralen
eine einfache
tifizierung
Für die
Signalen.
zwischen der
Signale
einer bekannten
Quantifizierung
thoden, die auf der
Quantifzierung oder
von
und die
der FTIR
Quan¬
Prüfgase) möglich, oder,
Signale
von
in den
der
basieren:
gezeigt,
die
dass die
wurden
Desorption
Zentren
die
zwei Me¬
am
Beispiel
wurde die Puls¬
angewandt,
von
Untersuchung
Stickoxiden der
Adsorp¬
Normaldruck. Die kontinuierliche Auf¬
injizierten
von
wie
Katalysatoroberflächen
Moleküle im
liefert die
Trägergas
Dynamik der Physisorptionsprozesse zu bestimmen. Desorptionrate
der
und Wasser getestet.
selektiven Reduktion
ermöglichte
unter
an
ver¬
Splintloch- (Pin¬
verschiedener Prozesse
katalytischen
der Konzentration der
Möglichkeit,
durch die Ein¬
Flüssigkeiten,
Quantifizierungsmethoden,
von sauren
durch Ammoniak. Die PulseTA
zeichnung
Kalibrierung
Trägergasstrom.
Diese Methoden wurden
Untersuchung
Bestimmung
tion als auch der
der Flüs¬
FTIR Daten. Für Gase ist die
Verdampfung von Flüssigkeiten
Verfolgung
überprüft.
untersucht, nämlich die Pulskalibrierung und
für die
die
Dehydratisierung
ermö¬
Menge des Kalibriergases
Basierend auf den getesteten
Beispiel
spektroskopi¬
eingespritzten Menge
Quantifizierung verschiedener organischen Flüssigkeiten
zum
der
entweder durch herkömmliche
hole-) und Differentialkalibrierung.
thermoanalyse
Genauigkeit
spektroskopischen Signale
Intensität der
Konzentrationen der
schiedene Methoden
Die
Opti¬
experimentelle Bedingun¬
Zersetzung (NaHC03)
Quantifizierung
der FTIR
(unterschiedliche
spritzung
durch
Substanzen mit bekannter Stöchiometrie
Abhängigkeit
und der
sigkeiten
FTIR
wurde durch die
H20)
5
•
signifikant
die
Spektrosko¬
Parameter für die FTIR
wurde, diente als Referenz für die Bestimmung der
Quanitifzierung von
schen
erlaubten
massenspektrometrischer Analyse
mit
physisorbierten Species
vom
Es wurde
Trägergas-
XIX
strom
und
PulseTA
,
von
der Schichtdicke der Probe
verglichen
bierten Gases, sowie die
werten
von
die
Vorteil der
und
Menge
des adsor¬
gleichen experimentellen
Einrich¬
und
Integrale Adsorptionswärmen
können.
die
chemisorbiertem Ammoniak stimmten gut mit den Literatur¬
überein, welche mit anderen Methoden ermittelt wurden.
Schliesslich wurde mit Hilfe Reduktion untersucht.
von
von
TA-FTIR-MS die selektive
Stickoxiden durch Ammoniak
Zitronensäuremethode
den
an
hergestellt
Redox-Eigenschaften
Mangan-Cer-Mischoxiden
an
entsprechenden
Metallnitraten mittels der
und hinsichtlich des
katalytischen
und des
katalytische
mit unterschiedlichem molarem Verhältnis
Mischoxidkatalysatoren
Mn/(Mn+Ce) wurden
der
in der
wichtiger
Methoden, ist, dass die
Bestimmung der Art
Desorption
untersucht werden
Mengen
Ein
mit klassischen volumetrischen
Vorbehandlung des Adsorbens,
tung
abhängt.
Adsorptionsvermögens,
Verhaltens untersucht. Diese
Studien, die auf der PulseTA® basierten, zeigten eine deutliche Korrelation zwischen der
dieser
Abhängigkeit
mensetzung auf. Höchste Aktivität wurde für den 0.25
Katalysator
gefunden,
niedriger
war.
Eigenschaften bezüglich
und der Mischoxidzusam¬
selektiver Stickstoff-Produktion
mit einem molaren Verhältnis
während die Aktivität für die reinen
Die
Adsorptionsstudien zeigten,
dass
Mn/(Mn+Ce)
Oxidkomponenten
NOx und NH3
an
von
viel
unter¬
schiedlichen Zentren adsorbiert werden. Konsekutive
Adsorptionsmessungen
zeigten ähnliche Adsorptionsmengen
wie sie durch separate
der Reaktanten
Messungen ausschloss.
erhalten
wurden,
Untersuchungen
Zuführungsreihenfolge 150 °C
bezüglich
eine Interferenz zwischen den Adsorbaten
was
zum
Reaktionsmechanismus
der Reaktanten
(NOx, NH3)
Stickstoff-Produktion auf einen
hin, wobei absorbiertes Ammoniak
mit
NOx
in der
unter
Variation der
wiesen zwischen 100-
Eley-Rideal-Mechanismus Gasphase reagiert,
während
XX
absorbiertes gungen
NOx
zeigte.
keine bedeutende Reaktivität
unter
den verwendeten Bedin¬
1
Chapter
Introduction
1.1 General
Thermal
and
Aspects of Thermal Analysis
analysis (TA)
is
well-known
a
quantitative information about
mainly
solid
materials, such
set
of
techniques enabling qualitative
the effects of various heat
catalysts, polymers, pharmaceuticals, clays
as
minerals, metals and alloys. The
change of the
formed under
conditions and
enthalpy
due
studied. A
techniques
strictly controlled to
physical
and chemical
widely accepted that
study
the
treatments
can
reveal
changes
phenomena occurring
between
and
temperature in the system is per¬
definition of thermal
relationship
on
mass
and
in the material
analysis (TA)
sample property
a
in
is:
group
a
of
and its tempera¬
ture.
There
are
different thermal methods
properties, including: ature
ning
difference
heat
(calorimetry),
(differential
calorimetry),
thermal
mass
allowing
the
temperature
analysis),
(thermometry),
heat flow
(thermogravimetry),
of several
measurement
rate
temper¬
(differential
mechanical
scan¬
properties
(thermomechanical analysis), electrical properties (dielectric thermal analysis) pressure
(thermomanometry
thermobarometry), optical properties (ther-
thermoluminescense),
moptometry
or
coustimetry)
or structure
most
or
acoustic
(thermosonimetry
(thermodiffractometry).
Here
important techniques: thermogravimetry (TG),
we
focus
or
thermoa-
on
the three
differential thermal anal¬
ysis (DTA) and differential scanning calorimetry (DSC).
2
Chapter
1.1.1
Thermogravimetry (TG)
1
The definition of TG
and
Analysis stance
given by
as
the International Confederation for Thermal
Calorimetry (ICTAC)
is measured as
a
is:
a
technique
function oftemperature
in which the
whilst the substance is
subjected to a
controlled temperature program. A controlled temperature program •
ing
the
mon
•
the
Heating or cooling mass
the
change
Therefore,
or
Additionally the
rate,
and monitor¬ most com¬
The DTG which the
or
data
are
usually presented
change
curve
be
can
(DTG),
curve
in
mass
which
also allows the
of mass loss has
teristic temperature
depicting
a
presented as
which is
temperature. The DTG
changes
rate
temperature and
monitoring
the
as
mass
a
of the
plot
loss
on
mass
the ordinate
gains plotted upwards.
mass
mass
thermogravimetric time
constant
some
temperature (the TG curve), with the
downwards and
subtle
at
thermogravimetric
plotted
ing
constant
function of time, called isothermal TG.
as a
time
against
defined
function of temperature. This is the
as a
sample
against
tial
at some
can mean:
mode of operation.
Holding mass
change
sample
sub-
of a
mass
curve
are not
ready
plot
a
point
rate
discernible
differen¬
or
of mass
useful in on
change
display¬
the TG
curve.
determination of the temperature
maximum and
the
of the
particularly
is
easily
the derivative
provides
an
at
additional charac¬
of inflection of the
investigated
TG
curve.
1.1.2 Differential Thermal
Analysis (DTA)
and Differential
Scanning
Calorimetry (DSC) Differential thermal
(DSC) have had ment
a
analysis (DTA)
great
impact
on
and differential
material science
of a great number of physical and chemical
scanning calorimetry
by enabling
properties.
the
These
measure¬
techniques
Introduction
have allowed elucidation of endothermic and exothermic processes in
temperature range. Some of the
analytical
methods include
these processes,
specific
measured
physical properties
melting, crystallizations
DTA state
lytic
are
temperatures,
enthalpy
which could be monitored
properties
transition
DSC and
by
oxidative and reductive reactions, solid
chemisorption, combustion, polymerization, curing
and
cata¬
reactions.
According
to
ICTAC:
difference
In DTA, the temperature
material is measured as material are
rial is measured material are
(DTA
as a
a
in energy
are
simultaneous thermal
to
of mass
while the substance and reference
into
a
substance and
a
reference
while the substance and
two
main thermal
(TG) and changes
measured
simultaneously.
mate¬
reference
analysis techniques
in heat
capacity of the sample
Such
combination is called
a
analysis (STA).
Hyphenated Techniques
The
success
of simultaneous
analytical
input
combine
1.2
ventional
reference
controlled temperature program.
advantageous
DSC),
a
controlled temperature program.
function of temperature,
measurements
or
between the substance and
function oftemperature,
difference
subjected to
It is often
that
a
subjected to a
In DSC, the
so
of
capacity, liquid crystal transitions, vaporization,
heat
dehydration, decomposition,
reactions,
wide
a
these thermal
by
sublimation, solid-solid transition, thermal conductivity and glass temperature. Chemical
3
in Thermal
techniques
methods with
an
has led
to
STA system.
Analysis the
coupling
Analytical
of other
con¬
methods such
as
MS, FTIR spectroscopy, GC, condensation of volatiles and their chemical
Chapter
4
1
have proven
analysis from
a
goals
of coupling these
sample
tem
and
to
data
sets
that
as
it
be suitable for
to
undergoes
thermal
techniques
eliminate the
problems
gas
have those which
the
monitor
can
most
Due
to
the
probably
is
universal
most
resulting
are
generally
course
done
taining key fragment
compounds.
Much
for
technique
currents
for
linking
et
are
but clear of the
develop¬ experi¬
al. [1-3].
of the
of the gas
MS is
systems
Their identification is the main
together with
thermal
investigated
reaction. The
qualitative MS
analysis
aids
anal¬
recorded spectrum with references
by comparing the
con¬
ions and their relative intensities for known elements and
more
and the
difficult, but
very
relationship
amount
published by Gohlke a mass
composition,
which
of the
One of the earliest reports of the was
samples
analyzing multicomponent
products.
technique,
i.e. the determination of the
(EGA)
sys¬
compare
from the first
by Materazzi
spectrometer
and
to a
is the
important
pretation of mass spectrometric data, which needs the
the ion
to
MS and FTIR. The
hyphenated techniques
in gaseous
of the TA-MS
interpreting the
ysis
trying
single
conditions. There
the gaseous
possibility of continuous monitoring
and reactions
in
of a
Spectrometry (MS)
the
application
evolved
continuously the composition
mental attempts has been reviewed in detail
1.2.1 Mass
specificity
experimental
useful methods
of TA-MS and TA-FTIR
product
STA system. The main
associated with
are
analyze
to
an
enhance the
collected under different
were
phase. Therefore,
ment
that
the gaseous in
treatment
are to
many detection methods available
advantage
analyzing
quantitative
inter¬
calibration of the system,
between the observed intensities of
analyzed species.
coupling
of MS with evolved gas
analysis
Over the years several
designs
Langer [4].
TG/DTA system have been
reported
in lit-
Introduction
Raemaeker and Bart
erature.
main
of TG-MS
development
Table 1 -1
:
Raemaekers
1965
[5]
a
gave
detailed review and summarized the
settings (cf.
Table
1-1). One of the pioneers of
History of thermogravimetry-mass spectrometry and Bart [5].
Usefulness of MS
TG
to
[29]; (Friedman [30] 1968
Zitomer [31]
1968
Wiedemann
al.
up
to
1996. Table taken from
coupling suggested by Wendlandt et al. [28] and Gohlke et al. Py-TOFMS for plastics thermal decomposition studies)
describes
designs unique et
5
TG-TOFMS instrument; first
application
to
polymers
[32] develop Mettler-Balzers TG-QMS instrument with direct
vacuum
coupling al. [33] describe
TG-CT-MS arrangement
1969
Stanton
1975
Advanced
1977
Critical review of simultaneous
et
coupling systems
Baumgartner 1979
a
et
al. [36];
for
TG-QMS [34] TG-QMS couplings [35];
high
temperature TG/DTG/DTA-MS
[38] with two-stage pressure reduction system (quantitative interface);
magnetic
sector
instrument
First Du Pont-Du Pont TG-MS apparatus
1982
Development of TG-APCI QMS [42]
>1982
Strong improvement
1983
Commercially
1984
Shushan
al.
in data
collection; software development [43,44]
[49] describe TG-APCI MS/MS; Holdiness [50] and Dollimore
1997
Development of simultaneous TG-modulated (STMMBA) by
Behrens
et
al. [51]
developments
Introduction of Stanton Redcroft-VG commercial apparatus [52,53]
et
molecular beam
mass
spectrometry appara¬
al. [54]
Reviews of application of TG-MS for
al.
to
[40,41]
1986/87
1987/88
coupling of TG
available TG-MS interface [45-48]
review TG-MS instrumental
tus
equipment
[39]
1980
et
by
of Linseis-Leybold-Heraeus TG-MS instrument [37]
development
Introduction of commercial Netzsch
introduction of TG-CIMS
polymer
characterization
by
Chiu [55] and Jones
et
[56] of capillary
1988/91
Optimization
1991
TG-MS,-FFIR Conference in
1993
Hi-Res TG-MS
1994
Development of high sensitivity orifice-skimmer coupling [62]
1997
Special
sampling
coupling by
system [57,58]
Würzburg [59]; application
Lever
et
of TG-LVMS
by Yun
al. [60]
al. [61]
commercial Netzsch-Balzers instrument with
issue of Thermochimica Acta
et
on
TG-MS
improved
Chapter
6
the
1
hyphenated
this system
on
TA-MS
technique
Netzsch, later other manufacturers put
was
(former
the marked: Mettler, Perkin Elmer, TA Instruments
Pont) and others.
Mass spectrometers used for
coupling mainly originate
Du
from
Balzers, VG, Finnigan and Sciex.
1.2.2 Fourier Transform Infrared
The
(FTIR) Spectroscopy
of FTIR spectroscopy with
coupling
a
thermal
EGA is another well-established method for the
Although
suggestion for using
the
FTIR in EGA
analysis
analysis
was
unit
to
perform
of gaseous
first made
by
species.
Low
[6]
in
1967, and while experimental results obtained from coupling of TA and FTIR spectroscopy
were
reported
in 1981
available until 1987 [8-10].
was not
[7], the commercial
Up
to
that time
cation of evolved gases from TG has been carried
reports
on
studies
introduced new
•
on
powerful
using hyphenated
the market
by
TA-FTIR
e.g. Netzsch in
method with the
work
most
out on
were rare.
coupling on
TA-FTIR
the identifi¬
TA-MS systems and
The TA-FTIR system
cooperation
with Bruker offers
a
following advantages:
Functional group identification and
specific compound analysis
on
the
basis of vibrational spectra. •
Simultaneous
•
Reference
spectral
spectral
information
libraries for
over
On the other hand it is rather difficult
pounds
with similar functional groups,
nuclear gases
not
showing
distinguish hydrocarbons
many
species.
250 000
species.
on
to use
moreover
IR absorbance
above
C3H6.
IR
to
analyze
FTIR
mixtures of
cannot
(e.g. 02, N2)
or
com¬
detect homo-
does
not
readily
Introduction
1.3 Pulse Thermal
Pulse Thermal increase the
Analysis
Analysis (PulseTA )
potential
was
developed
of conventional thermal
ket in 1997. The basis of the PulseTA
in 1996
analysis,
technique
of the desired gas into the inert carrier gas
changes
in the
progress. In
makes it
as
possible
well
injected,
enthalpy
addition, with
reactions caused MS
and
as
to
by
the
TA-MS
coupling
offers three
stream
the
of a
injection and
mar¬
specific
monitoring
or
TA-FTIR systems, PulseTA
phase composition changes resulting
injected pulses.
the FTIR
PulseTA
gas
on
to
which result from the incremental reaction
coupled
analyze
in order
[11]
and arrived
is the
amount
mass
7
The PulseTA
box
Depending
systems.
can
on
from the
be used with
the type of gas
primary options for the investigation
of gas-
solid reactions: •
•
•
Injection
of gas which
Injection
of gas which adsorbs
Injection
of inert gas in order
PulseTA
reacts
chemically with
nism of decomposition of solids
1.4
In
removal
Scope
recent
calibrate was
spectroscopic signals.
applied
for
investigation
of:
properties of gold catalyst [13,14],
catalytic mecha¬
[15,16], redox properties of ceria [17-20], and
of this Thesis
years
hyphenated techniques involving
more
situ
quantification
important.
exploring
the solid.
[16,21-27].
and
to
to
in combination with MS
combustion of methane [11,12],
NOx
on
solids.
The aim of this thesis
from TA-MS
PulseTA
and
to
thermal
was to
TA-FTIR.
analysis
extend the
Special
became
application
more
of in
effort has been devoted
finding optimal measuring conditions,
which allow
Chapter
8
quantification FTIR
1
of spectroscopic
complement
linking
of TA
series) enables Another
to
each other, for studies of
both
a
complete
more
important
the
sites
catalysts (Chapter 5)
as
(Chapter 6).
and the
on
parallel
in
application
investigation
over
or
in
the acidic
mixed oxides
to
by
of the evolved gases
crucial issue and lead
a
in
of the mechanism of the
quantification
results which would have been difficult
of PulseTA
assessing
manganese-cerium
catalyst was
the
the
of ammonia for
In both studies the
during reaction/adsorption esting
study was
adsorption
selective reduction of nitric oxides ammonia
(either
evaluations.
aspect of this
research such
reactions the
complex gas-solid
MS and FTIR spectrometer
catalytic on
in TA-FTIR-MS systems. Since MS and
signals
gain by
to
inter¬
experimental
other
methods.
1.5 References
[1]
S. Materazzi,
Appl. Spectrosc.
Rev. 32
(1997) 385.
[2]
S. Materazzi,
Appl. Spectrosc.
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[3]
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[4]
R.S. Gohlke, H.G.
[5]
K.G.H.
[6]
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C.A.
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Raemakers, J.C.J. Bart, Thermochim. Acta 295 (1997) In: W.
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[7]
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Cody,
L.
Lodding, Editor,
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Compton,
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Wieboldt, G.E. Adams,
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1.
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Lowry, RJ. Rosenthal,
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[10]
Solomon,
PR.
Charpenay, J. Whelan, J. [11]
M.
Maciejewski,
CA.
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Tschan, W.D. Emmerich, A. Baiker,
R.
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Maciejewski,
M.
Bassilakis, Z.Z. Yu, S.
R.
Appl. Pyrolysis
Anal.
Muller,
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[12]
Carangelo,
M.A. Serio, R.M.
9
Koeppel,
R.
A.
Baiker, Catal. Today 47
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J.-D. Grunwaldt,
M.
Maciejewski,
O.S.
Becker,
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Fabrizioli, A. Baiker,
J. Catal. 186(1999)458. [14]
M.
Maciejewski,
Phys. [15]
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Maciejewski,
M.
Fabrizioli, J-.D. Grunwaldt, O.S. Becker,
Phys.
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3
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E.
A.
W.-D.
Emmerich,
A.
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[16]
E.
Ingier-Stocka
E, M.
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Thermochim. Acta 432
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E.
Rocchini, A. Trovarelli, J. Llorca, G.W. Graham, WH. Weber, M.
Maciejewski, A. Baiker, J. [18]
WJ. Stark, L. Mädler,
M.
Catal. 194 (2000) 461.
Maciejewski,
S.E. Pratsinis and A.
Baiker, J.
Catal. 220 (2003) 35.
[19]
H. Schulz H,
WJ. Stark,
Mater. Chem. 13
[20]
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Wögerbauer,
Maciejewski,
S.E. Pratsinis, A. Baiker,
J.
(2003) 2979.
WJ. Stark, J.D. Grunwaldt, Chem. Mater. 17
[21]
M.
M.
Maciejewski,
S.E. Pratsinis, A. Baiker,
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M.
Maciejewski,
A.
M.
Maciejewski,
M.M.
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[22]
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Wögerbauer,
74(2001)
1.
Schubert, A. Baiker, Cat.
Lett.
10
Chapter
[23]
C
1
Wögerbauer,
M.
Maciejewski,
A.
Baiker, U. Göbel, J. Catal.
201
(2001) 113. [24]
C
Appl.
Baiker,
Catal. B 34 (2001)
Wögerbauer,
M.
Maciejewski,
Wögerbauer,
M.
Maciejewski,
A.
Baiker, J. Catal. 205 (2002) 157.
Maciejewski,
T.
Burgi,
A.
11.
[25]
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M. Piacentini, M.
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A. Baiker,
Top.
Catal. 30
71.
[27]
M. Piacentini, M.
[28]
WW
[29]
R.S.
[30]
H.L.
[31]
F.
[32]
R.
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H.L.
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Wendlandt,
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Gohlke, H.G. Langer, Anal. Chem. 37 (1965) 25.
Friedman, J. Appl. Polym. Sei. 9 (1965) 651.
Zitomer, Anal. Chem. 40 ( 1968) 1091.
Giovanoli, H.G. Wiedemann, Helv. Chim. Acta 51 (1968) 1134. Friedman, Thermochim. Acta
Eppler,
In: I. Buzas,
1
(1970)
199.
Editor, Therm. Anal., Proc. ICTA,
4th, Mtg. date 1974 Vol. 3, Heyden and Son, London (1975) 1049.
Eppler,
Selhofer, Thermochim. Acta 20 (1977) 45.
H.
[35]
H.
[36]
E.
Baumgartner,
E.
[37]
W
Lampen and
G.
[38]
W.D.
Emmerich, E.
[39]
K.W
Smalldon, R.E. Ardrey, L.R. Mullings, Anal. Chim. Acta 107
(1979)
Nachbaur, Thermochim. Acta 19 (1977) 3.
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327.
[40]
J. Chiu, AJ. Beattie, Thermochim.
[41]
R.L. Hassel
[42]
S.M.
1,
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(to
Dyszel,
Du
In: B.
Wiley Heyden,
Acta 40
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Chichester (1982) 272.
[43]
H.K. Yuen, G.W.
Mappes,
Introduction
11
W.A. Grote, Thermochim. Acta 52
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143.
Till,
[44]
G.
Vârhegyi,
[45]
E.
Kaisersberger,
M.
[46]
E.
Kaisersberger,
Intl.
[47]
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Kaisersberger,
W-D.
[48]
E.
E
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[49]
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[50]
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Dollimore, G.A. Gamlen, T.J. Taylor, Thermochim. Acta 75 (1984)
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[51]
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Warrington, Journ. Calorim.,
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114(1987)47. [53]
E.L.
Charsley, N.J. Manning,
Therm.
Thermodyn.
S.B.
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E.G.
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D.L.
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Schwanebeck, H.W. Wenz, Fresenius Z. Anal. Chem. 331 (1988)
61.
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Kopplungen
der Instrument¬
für die Kunststoff- und Kautschukindus¬
12
Chapter
[59]
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1
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für die Kunststoff- und Kautschukindustrie
[60]
Y Yun, H.L.C.
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Seite Leer / Blank leaf
Seite Leer / Blank leaf
Chapter
2
Experimental
This
chapter describes
of the the
analytical
the
methods.
experimental
of the
Specific descriptions
general
experiments
features
given
are
in
pertinent chapters.
2.1 Simultaneous Thermal
The heart of the is
setup used and reports
a
2-1.
calorimetry (DTA/DSC)
The results of both
reaction is
single
not
affected
by
measurements.
neously with
mass
changes
corrected for
mass
loss
nates
the uncertainties
caused
by
the
or
are
are
techniques
different
be
experimental
are
to
the
same
as
the target
conditions which
can occur
easier
to
interpret and enthalpy changes
gain. Moreover, simultaneous
inhomogenity
in
analysis/differen¬
directly compared,
arising with separate TG
investigated.
schematically presented
applied simultaneously
can
analysis
addition, the thermal effects measured simulta¬
In
temperature control. This is reactions
which is
and differential thermal
Thermogravimetry (TG)
tial thermal
sample.
thermal up used for the simultaneous
Jupiter®,
Netzsch STA 449 C
Figure
with
experimental set
Analysis
and geometry of
thermal
analysis
can
be
elimi¬
and DTA/DSC measurements,
samples
especially significant
and
when
inaccuracy
in the
complex multistage
16
Chapter 2
J DSC
sample
carrier
gas outlet
(MS-GC-FTIR)
/ furnace
TG
sample
carrier
sample
carrier
radiation shield
protective tube thermostatic control vacuum
seal
reactive gas
protective gas
(QH^
evacuation
inductive displacement transducer
system
electromagnetic compensation system
tight
vacuum
Fig.
2-1
Scheme of thermoanalyzer: Netzsch STA 449 C Jupiter
:
Characteristic for the instrument TG
(drift
ments
to
150 °C) in the
after the
liquids
a
very
and
narrow
FTIR
signal
injection before the thermoanalyzer.
through
due
sharp
to
a
much
larger volume (TA)
com¬
In that
and FTIR
prominent backmixing phenomena
occur¬
in the TA-chamber.
3.2.2 Pinhole Calibration This method with
was
used
organic liquids
placed
to
or
calibrate the FTIR spectra when
water.
in the crucible closed
(0.1, 0.5, 50 ml min"
25 mg of the
the lids with
calibration
investigated liquid
pinholes with
mm). The heating and flow
and 2
1
by
Usually
making
rate
was
different diameters
were
10 K
min"1 and
respectively.
,
3.2.3 Differential Calibration Last method allows
gation
of the
carrying
out
the calibration of the FTIR
decomposition (or desorption)
process
signal
during
and investi¬
one run.
up consists of two crucibles: the first contains the
liquid used for the
and the second
quantification
FTIR
signal
perature
one
the
obtained
(25-50 °C)
investigated sample.
during vaporization
or
during a
The
of the
non-isothermal
liquid
run
at
carried
The
set
calibration
is based
on
the
low,
constant tem¬
out
with low heat-
Quantitative
ing
rate
up
to
temperature of the solid
The
sample.
rate
of vaporization
very broad range
by varying
experiments
normally performed applying
30 min 10 K
were
followed
by
the
min"1. The sample
25 mg and the
overlapping
mass
the temperature and the
of the calibrated
of decomposed
of the calibration and
the
liquid
ing
the isothermal
sample was
with
liquid
was
The carrier gas flow
before
was set to
25-50 ml min'
in
a
diameter. The of about
period
of
rate
in the range of 10-
100-200 mg. In order
of the
beginning
changed
heating
a
processes, it
measuring
be
pinhole
reference material used for the calibration had run,
can
31
decomposition
isothermal
an
decomposition period
mass
Spectroscopic Signals below the
lying significantly
temperature
a
Calibration of FTIR
was
to
avoid
important that
fully evaporated
decomposition
dur¬
of the solid.
.
3.3 Results and Discussion
We
have
investigated
described above. The gases and
3.3.1 The
liquids
application
FTIR in
in the calibration
a
FTIR
of PulseTA
by comparing simultaneous
decomposed
position 2
presented examples
Quantification of
illustrated
was
the three methods of calibration
—>
results obtained
by
means
of
of FTIR
a
occurs
H20
+
heating
rate
according
C02
to
of 10 K
Eq.
signals
thermogravimetry
PulseTA®-FTIR experiment. 36.15
+
of both,
Gases
quantitative interpretation
under helium with
Na2C03
application
signals
procedure.
Signals Using
for
of sodium bicarbonate
NaHC03
describe the
of FTIR
mg of
is
and
NaHC03
min'1. The decom¬
1:
(1)
Chapter
32
In order
injected
to
3
the FTIR
quantify
before and after the
of C02,
signal
decomposition
of
of C02
were
NaHC03 (Figure 3-1A).
The
two
1 ml
pulses
B
12.34 mg
50-
30-
pulaa
20-
10-
//b.osII
at 50 *C
\
puis«
at 250 'C
// /4,5o\ll
V
HI/2-7s\\I
20
time / mln
2
4
amount of
Fig.
3-1
:
A: 3-D
the
FTIR-diagram of
6
C02
present
8
in the
10
sample
of the calibration
12
14
/ mg
(2 pulses) and the evolved
decomposition Relationship between amount NaHC03. and sample intensity of C02 traces recorded in TA-FTIR system. C: FTIR function of amount of C02 present in the sample. as by a
B:
of evolved
gases
during
C02
in the
Amount of C02 found
mean
the
value of the
perature of the
of the
injected pulses
of the evolved
signal
injected gas was
decomposition
of the
integral intensities
integral intensity
Spectroscopic Signals
Calibration of FTIR
Quantitative
28 °C. The
C02
amount
calculated from these data
quantification
intensity
of FTIR
NaHC03 Figure
were
method. In order
signals
and
amount
decomposed.
The
to
corresponds
check the
of evolved
9236
was
tem¬
the
during
confirming
the accuracy
dependence
between the
traces
amounts
presented
are
of in
3-IB.
Figure
3- 1C shows the relation between the
derived from FTIR obtained linear
(peak areas) presented
and
case
and the
signals
dependence amount
from 0.64
integral
12.34
milligrams
of evolved
a
intensity C02
of the FTIR
have been
(Eq. 2)
was
101/99
a.u.,
signals
injected
independent
=
investigated.
C02
The
traces
wide range: in the
C02. the
on
At each temperature
into the carrier gas stream; the
shape
and
pulses
two
integral intensity
of the temperature (50 °C: 101/100
950 °C: 101/98
/
was
C02
sample.
intensities of
of evolved gas has been hold in to
of evolved
of C02 present in the
amount
between the
amount
The influence of the temperature (in the TA chamber)
of
The
9.52 mg, which
to
species, different
resulting C02
while
a.u.,
a.u.
of C02 formed
agrees well with the stoichiometric value of 9.47 mg,
of the
1727
was
33
a.u.,
/
350 °C:
a.u.).
}[j^(v)
1
*
-r-
methanol
'^^T^
time / min
02
04 w
Fig.
3-4:
A: FTIR spectra of
B: methanol and
pendence
binary liquid
methylformate traces
between the
as a
integral intensity
D: resulted FTIR absorbance ratio
06
(methanol)
/
06
mgVmg
mixtures of methanol and
function of the mixtures
of the FTIR
vs. mass
ratio
signals
on
methylformate.
composition.
the mixture
(W) of methanol in the
C: The de¬
composition. binary mixtures.
Quantitative
is in
principle possible
to
limitation is the poor
ous
stirring As
liquids, the
is an
not
possible
example
we
Calibration of FTIR
obtain the
vapor-liquid equilibrium data,
mixing (natural
in the
commonly
convection
only).
but
Note, that
a
seri¬
sample
used TA-FTIR systems.
of quantification of FTIR spectra
present the determination of the
decomposition
41
Spectroscopic Signals
amount
of sodium bicarbonate and
by pulse of
water
dehydration
calibration with evolved
during
of copper sulfate
pentahydrate. Figure 3-5A and
shows the
decomposition
water traces
of 106.5 mg
recorded
during
NaHC03 according
20
30
two
to
calibration reaction
pulses
(1). The
40
time / min
during decomposition of 106.5 mg NaHC03 (A) and 48.9 mg CuS04 5 H20 (B). Heating rate: 10 K min"1, carrier gas: 50 ml min"1, Injected water volumes: 10 JLLl (A), 2.5 |ll (B). Fig.
3-5:
Pulse calibration:
water-traces •
recorded
42
Chapter
mean
the
3
value of the
integral
integral intensity of
amount
formed
injected
during
the
intensities of the
of the
water
of the evolved
signal
10.0 mg
was
decomposition
injected pulses
(ca.
10
was
H20
was
The
(4.1).
445
515
The
a.u.
of
amount
calculated from these data
while
a.u.,
H20
corresponded
to
10.87 wt.%, which agrees well with the stoichiometric value of 10.69 wt.%,
confirming the
the accuracy of the
decomposition
due
to
corroborated
the evolution of C02 and
ric value
and
was
amounts to
shows the
dehydration
of 48.9 mg
dration of the
sponded
to
During
firmed
of FTIR
the further
respectively).
The
the observed
mass
of
loss
36.85 wt%, while the stoichiomet¬
recorded
H20. two
calibration
pulses
At lower temperatures the
dehy¬
during
two
steps; the observed
well with the evolved
agreed
at
mass
loss
corre¬
of
water
amount
amount
(between
about 220 °C
(dehydration
and stoichiometric
mass
of
48 and 52 min)
monohydrate),
losses
(7.17 and
of water determined from the FTIR of the
injected
2.41 mg
decomposition peak was 7-24
results and the reaction
gravimetric
analysis:
stoichiometry
(26.35 wt.%).
paring the integral intensity of the
5
•
molecules evolved
water
TG
was
occurred in
dehydration
by experimental
intensity
CuS04
25.82 wt.% and
the residual
H20
water traces
pentahydrate
by means
by the
method. The
36.90 wt.%.
Figure 3-5B
found
quantification
(ca.
2.5
con¬
7.21 wt.%,
traces
pü)
as
by
water
com¬
and the
wt.% which is in accord with the
stoichiometry.
Pinhole Calibration
During
the
pinhole
gas stream, but
by
a
linear
calibration the
placed
heating
into the
ramp. For
compound
thermoanalyzer
liquid
mixtures
is
not
and
injected
into the carrier
vaporized isothermally
(cf. binary mixtures)
it is
or
impor-
tant
select
to
related
ization of
3-6 shows the
pinhole sizes.
nol remarkable
mass
In this case,
.
losses
40
Due were
the low
recorded
immediately
T-
'
1
SO
certain
a
amount
T—''"
'
1
60
70
accurate
an
t
80
'
—\
90
100
I"
1
1
1
40
1
SO
1
1
00
1
1
1
70
1
80
1
1
00
1
1
1
100
1
1
1
120
1
1
p
130
r~~\
1
140
150
'
Mi
'
40
30
I
3-6:
sample
indicated
on
25 mg,
the
heating
curves.
rate:
loss
during evaporation
1
'
"
'
50
i"
"»
SO
'
1
1
1
40
1
1
60
1
1
80
1
1
p
100
'
'
'
'
100
r-
110
/ 'C
1
|
120
1
90
80
70
even
r,M-'
140
""T
160
'"
'
"I
160
'
200
temperature / °C
Pinhole calibration of
mass:
measure¬
using larger pinhole
temperature
110
starting
of the substance will evaporate
temperature / *C
Fig.
after or
lid
mass
pans
of acetone and etha¬
boiling points
temperature / *C
30
of
during vapor¬
(C) and hexanol (D) from the
water
to
determine
to
because
r——'—-r
30
overlapping
recorded
signals
especially when working without
sizes, it is difficult
(cf. Figure 3-6A)
losses and FTIR
mass
(A), ethanol (B),
acetone
with different
avoid
to
bands.
absorption
Figure
ment.
characteristic wavenumber interval
a
43
Spectroscopic Signals
Calibration of FTIR
Quantitative
acetone
(A), ethanol (B),
10 K min"
,
flow
rate:
water
50 ml min"
(C) and heaxanol (D), ,
pinhole
diameters
are
44
at
Chapter 3
room
temperature, which in turn, will disallow
between the with tion
a
amount
pinhole
at room
of
size of 0.1
sary
to
achieve
loss in the
pressure)
higher
accurate
water
beginning of the experiment
of
the
liquids,
some
than 25 mg.
amount
due
of the
mass
measurements were
loss of the
started
The detailed results of the relative standard deviation
boiling points ranging at
Table 3-3 :
can
and
was
from 56 °C at
introduce
the a
(acetone)
beginning
to
the
rate
mass
(vapor was
liq¬
mg.
listed in Table 3-3. The
liquids with
154 °C (hexanol). The vapor¬
of the
error
by
of the calibration
smaller than 4% for all four
significant
Pinhole calibration: FTIR
are
pinhole
recorded. The cali¬
precisely 25.0
calibrations
a
isothermal part of
some
mass
the base¬
substance used
was not
the
vaporiza¬
were neces¬
high evaporation
sample
was
lids
caused
calibrating
exactly when
pinhole
(RSD)
low temperatures
its start, which
the
at
For ethanol
uncertainty
During experiment settling
uid, measured by the internal TA balance,
ization
to
acetone
even no
A lid
traces.
which started
trace,
and hexanol
calibration. To avoid
the temperature ramp the
bration
and for
relationship
of FTIR
prevent the
integration of the recorded peak.
enough
mm was
intensity
to
necessary
mm was
temperature and obtain the FTIR
line and enabled proper size of 2.0
and
evaporated liquid
the
finding
experiment
during
integral intensity
the
recorded
or even
pinhole
before
calibration
during vaporization
of
liquids (acetone, ethanol, water and hexanol) from pans covered by lids with various pinhole sizes. Peak areas were determined at their characteristic wavenumber and 25 mg of different
normalized
Sample
to
an
average of 100
0.1
mm
a.u.
0.5
mm
acetone
98.7
-
ethanol
97.2
-
water
102.0
hexanol
104.2
1.0
mm
2.0
mm
no
lid
RSD / %
101.1
101.5
98.6
1.52
99.1
102.8
100.9
2.38
98.8
99.2
1.78
98.1
100.2
3.73
-
-
102.7
94.8
45
Quantitative Calibration of FTIR Spectroscopic Signals
procedure,
also
was
reported by Slager
highly volatile compounds (e.g. occurred before the TGA
affects
intensity of the
backmixing, resulting can cause
in
started.
actually
crucial factor in the calibration recorded
signals.
of the
does
desorption
or
spectroscopic signals
has been
MS-TA system
In order
[11].
pinhole method, experiments
to
study
were
The real progress of the
curve
(DTG) that indicates the
shape
carrier gas flow
carried
out
evaporation rate
of the
of the recorded
3-7 shows the
normalized in order
signals.
carrier gas flow
in
a
prominent
phenomenon
single
stage due
to
and intensity of
shape
on
some
of
us
the calibration
for the
by
the
with different carrier gas flow
is reflected
mass
change.
by
the derivative TG
This progress has been
spectroscopic signals
of the FTIR
quantification
to
heated with 10 K allow
to
as a
investigate
the
function of the
a
the
leads
to
presented
signals using pinhole
carrier gas flow
rate.
25 mg
min"1. All DTG and FTIR curves
comparison
The results
rate
and results in
backmixing (cf.
higher
rate.
sample of ethanol was
tem
the
this influence
(2.0 mm) calibration of ethanol when varying the
the FTIR
to
intensities of the recorded
not occur
on
This
the recorded FTIR spectra which allowed
of the
leads
to more
analyzed quantitatively by
rates.
Figure
rate
signals.
integral
The influence of the flow
overlapping signals.
to
Low flow
that
procedure,
observed spectra, but increases the residence time of
significant tailing
when the reaction
changes
methanol) significant evaporation
and
difficulties in the evaluation of the
compared
[21]. They found that for
molecules in the TA-FTIR system and leads
evaporated
signals
a
intensity and shape of the
maximum
the
acetone
run was
The carrier gas flow is
and Prozonic
of flow
in
rate
Figure
influence
3-7
clearly
on
the
were
shape
of
indicate that low
increase of the residence time in the TG-FTIR sys¬
long tailing of the
recorded FTIR
comparison of the real
rate
of the
traces
due
to
evaporation
prominent
process rep-
46
Chapter 3
'
A
5mlmln1
20 ml
mm
27
50 ml
mln1
65 ml
DTG
FTIR
5 min i
1
35 ml mln
mln1
JIJLJL 25000
0 00
0 01
0 03
0.02
flow"1
Fig.
3-7
heating rate: 10 K min'1, the integral intensity and
tween
the
(thin) and
DTG
the flow
to
resented 20 ml
by
mass
al.
(ml
to
min"
the
transfer
thermoanalytical
varying carrier FTIR (thick lines).
flow defined
), which
delayed a
linear
are
as
B:
sample size: The relationship be¬ rate,
the ratio of
marked
FTIR
flow
on
volume
the data.
for
traces
relationship
injected
the
flow
of
between FTIR absor-
and
(by
convection and
mass
spectrometric
diffusion) curves
on
was
the relation
reported by
[11].
Although, for the
ml"1
reciprocal values of the flow rate (Figure 3-7B). A detailed study
of the influence of
et
curve
reciprocal
However, there exists
bances and the
between
of carrier gas
rate
DTG
min'1).
Roduit
/ min
006
0 05
A: Pinhole calibration of ethanol with
:
25 mg,
(1 ml)
0 04
the best accordance between DTG and FTIR
highest flow rate
of 65 ml
min'1,
in further
traces was
found
experiments generally a flow
Quantitative
to
min"1
of 50 ml
rate
used. This flow
was
nation of different
TG-steps
in
a narrow
De la Guardia and coworkers
critical parameter in vapor
analytical sensitivity of 50 ml
[17] used
min'1,
stated that
The main
a
good compromise
temperature window.
spectrometric analysis which
which allows
a
20
(60 ml
rate
of the
carrier gas flow
TG
or
min"1)
of
one
this method temperatures up
of the FTIR peratures
to
obtain the
FTIR
the
run.
As shown
boiling point
for the calibration.
however, affect the process
low it in situ. Therefore
we
flow
in the carrier gas
al.
FTIR
same
it
et
can
be
requires
signals.
dependence between
signal required
can,
to
a
minimize the differences between ther¬
pinhole-calibration
experimental
is
affects the
nitrogen
in his studies with the
evolving species
rate to
DTG) and
disadvantage
be done in
necessary
a
rate
h"1 sampling frequency. Marsanich
beside uncontrolled
mentioned above, lies in the fact that the calibration and
can not
are
be
sampling frequency. They selected
higher diffusivity
a
moanalytical (e.g.
as
to
(8.7 ml) and FTIR path length (123 mm). Generally,
higher minimal
loss,
proved
[23] found that the carrier gas flow
FTIR
phase
and the
similar flow
a
gas cell volume
a
rate
47
Spectroscopic Signals
high analytical sensitivity and sampling frequency allowing discrimi¬
achieve
rate
Calibration of FTIR
developed
to
be
and
by Slager
of the
mass
Application
investigated,
applied
decomposition
at
al.
[21], using
calibrating
loss and
mass
substance
integral intensity
of such if one
high
tem¬
wants to
another method in
fol¬ our
laboratory, which will be discussed next.
Differential Calibration
The differential calibration is based ization of
a
liquid compound
and simultaneous
monitoring,
losses and intensities of FTIR
at
on
the isothermal
or
non-isothermal vapor¬
different temperatures, with low
in differential time
signals. Figure
heating
rates
periods, corresponding
mass
3-8A shows the
principle
of this
48
Chapter
3
ethanol i
1
0
20
specified
the
same
rate:
time
50 ml min"1. B: Linear
Crucible diameter
method
was
applied
for
mm
ing
time intervals
the
Figure the
same
on
the
are
indicated
mm
for
(5 min)
integral
and
by
plotted against
the TG
additionally the
time intervals
absorbances
on
water
(10 min)
signal.
same
is
were
the
This
mass
for
The very
over
liquids during
the temperature
curve.
calibration.
at
temperatures
measured
during
con¬
loss Am recorded dur¬
dependence
relationship
depicted.
of absorbance
of evolved
amount
isothermal calibration with ethanol
time intervals
3-8 B where
longer
dependence between the integral
for ethanol and 17-0
between 30 and 70 °C. The stant
r—
100
various temperatures. Interval time:
at
Corresponding temperatures 7.5
1
1
80
loss / mg
(5 min ethanol and 10 min water)
time interval.
1
SO mass
A: Differential calibration of ethanol
3-8:
5 min, flow a
loss / mg "i
40
HO
Fig.
mass "
r
is
presented
in
collected
during
good regression
coeffi-
water
Quantitative
(r2
cients obtained for ethanol accuracy of the
high
amount
periods
of
(observed
s
signals
signals
did
ml
of the reaction
course
14.1
to
significantly
period
and the
evaporation
is
this
During
are
the
experimental
(flow of 20
s
set-up.
beginning of the reaction
steady state
performed period of
the
this
of the
delay (flow:
in the
was
min'1). mass
Data
loss and
50 ml min"
)
placed
in
of the FTIR traces, but the
phenomenon. two
The target
in the isothermal mode
relationship
sam¬
separate pans which
thermogravimetric at
between the
evaporated liquid
can
are
The
runs.
relatively
low
intensity of the
be determined in
a
few
which increases the accuracy of the calibration. After
of the calibration
the TG
by
tailing
conventional
during
amount
periods
affected
sample
as
to some
curve,
liquid,
the second
which is indicated
experimental according
by
the end of the
stage is started, to
during
the chosen tempera¬
ramp. This in situ calibration is shown in
tion
chosen
(DTG curve) and that of measured
which the temperature in the system is raised ture
exact
influence the calibration results. At low flows the back-
not
prominent leading
differential time
on
one
had been reached. The 5.6 seconds
first calibration
loss
in
lag between
few minutes after
during a
weighed continuously
signal
species
ml
and the calibration
mass
arbitrarily
min"1)
was not
temperature.
the time
(for flow of 65
became
calibration
total
with the
signals
between the real
FTIR
signal
of the FTIR
DTG curve) and the appearance of the FTIR
collection occurred
ple
0.9975) indicate the
=
thermobalance in
by
of evolved
measurement
on
range of 4.3
mixing
(r2
water
of time allowed the extension of the method for the simultaneous cali¬
Depending on the flow rate,
FTIR
measured
49
Spectroscopic Signals
technique.
integral intensity
evaporated liquid
bration and
FTIR
0.99998) and
calibration
applied
The correlation of the
=
Calibration of FTIR
by FTIR of the
evolved
water
Figure
formed
3-9 which
depicts
during dehydration
the
quantifica¬
of sodium bicar-
Chapter
50
Fig.
3-9
Differential calibration:
:
NaHC03 (A) 50
(B)
3
and 200 mg
ml min'1. The
CuS04
mass
during decomposition of 200 mg H20 (B). Heating rate: 10 K min'1, carrier gas: 25 (A),
water-traces
5
recorded
of water used for the calibration
35 mg (B). Interval time: 10 min. Crucible diameter: 7.5
bonate and copper sulfate
pentahydrate. Figure
recorded
and
to
during calibration
reaction
10 min
H20 was
was
was
(Eq. 1). 2039
5045
The
a.u.,
a.u.
8.90 mg. The
integral
while the
The
amount
amount
lated from these data
decomposition
of
at
50 °C
3-9A shows the
of the
of evolved
during
corresponds
to
(A) and
water
during
the
water
trace
NaHC03 according
of 200 mg
integral intensity
formed
25 mg
mm.
of the FTIR absorbance
H20
was ca.
over
signal the
the interval of of the evolved
calibrating
decomposition
stage
calcu¬
10.98 wt.%, which agrees well with the
Quantitative Calibration of FTIR Spectroscopic Signals
stoichiometric value of 10.69 wt.%, the differential
Figure
quantification
3-9B shows
the observed evolved
amount
During
loss
mass
the
corresponding
CuS04
recorded •
5
corresponded
H20. to
decomposition starting
of
at
determined from FTIR
water
to
with
1071
3.3.3
integral intensity
Quantification of
At the first step of
decomposition
agreed
well with the
about 220 °C
(45 min), the
based
traces
loss agrees well
mass
7.21 wt.%,
vs.
on
applied
calibration data
was
signal
a.u).
FTIR
Solids
Signals Using
with solid calibration materials. In this
into the TG-FTIR system the calibration substance vent
The
respectively).
Some of the methods described above for the calibration of FTIR
also be
water
release of 12.68 mg of water results in FTIR
7.26 wt.% (mass loss due an
calibration and
24.90 wt.% and
with the stoichiometric value (7-35 wt.% amount
accuracy of
during differential
evolved: the observed
monohydrate
the
good
by FTIR (25.64 wt.%).
of water found
to
the very
method.
water traces
of 200 mg
decomposition
corroborating
51
case,
must
signals
before
could
injection
be dissolved in
a
sol¬
that possesses different characteristic FTIR bands than the calibration sub¬
stance.
Figure salicylic
3-10A shows the spectra recorded
acid
(ASA
or
spectra of the main and
phenol.
aspirin)
products
at
during decomposition
260 °C under
from
The bands used for the
of
dry and wet conditions,
IR-library:
acetic
quantification
acetyl-
and the
acid, salicylic acid (SA)
were
1800 cm"
(acetic acid)
and 3300 cm"1 (SA).
Figure
3-10B
position of 21.5
depicts
mg
the acetic acid and SA
aspirin
under
dry
and
wet
traces
recorded
during decom¬
(saturation of the
carrier gas
by
Chapter 3
52
JL
/\
phenol
salicylic acid acetic acid, (S
e o
É
.wet
-dry /*\-
m3500
3000
2500
1500
21
wavenumber /
1000
cm"1
wet. 29 wt.%
Jl
c
e
fV salicy|ic
FTIR
dry. acetic acid 100-
TG
80
I
4°
8
20
E
o
25 wt.%
wet: 24 wt.%
43 wt.%
57 wt.%
temperature / °C
Fig.
3-10:
A: Extracted spectra recorded
260 °C under
wet
during decomposition
approximately
B: Acetic acid and
traces.
wave-
salicylic acid
during decomposition of 21.5 mg aspirin under wet and dry conditions and done after the TA, imme¬ pulses injected before decomposition: Injections
recorded
calibration
were
diately before
the FTIR-transfer-line.
purging through
water at
30
°C) conditions.
10 mg SA dissolved in 100 ml ethanol
\i\ of the SA/ethanol avoid the show
at
(thick line) and dry conditions. The window of the characteristic
number is marked and used for further time-resolved traces
of aspirin
mixture
crystallization
were
was
injected
For the calibration
used. Two after the
|xl
of acetic acid and
thermoanalyzer
of SA in the TA chamber. Gravimetric
clearly a two-step-decomposition
57 wt.% for the first and second step,
two
in order
traces
to
(TG)
dry
conditions
(43
whereas
during the
reaction
of aspirin under
respectively),
solution of
a
and
Quantitative Calibration of FTIR Spectroscopic Signals
under
conditions the
wet
acid is evolved main
mainly
in
decomposition a
first step,
decomposition product
tion of
phenol
FTIR under
wet
conditions
slightly higher
was
(24 and 25 wt.%) for both conditions. Robeiro
mass
loss in
to
which agrees with
our
tion of acetic acid and
a
loss of 42.8% followed
results.
evaporation
by means
of ASA and SA.
of chromatography but
TG-FTIR system,
same
different flow able
flow
rate
carrier flow
the SA
heated transfer-line
high (50 SA
on
ml
possible
flow
rate
acetic acid
by Jackson
because of the
generate
directly
dry
of
con¬
almost the
reported
also
a
57.2% in the second step, mass
They
were not
on
was
loss
to
the evolu¬
able
quantify
to
it.
the FTIR spectra of the SA
heated under
nitrogen
with
al. [25], who found consider¬
et
high boiling point narrower,
the top of the
to
identified the evapo¬
of
salicylic
acid. With
but in TGA system
instability problems of the balance.
on
(200 °C)
the FTIR spectrometer and
high
The fact, that
thermoanalyzer just
cold spots in the system. This
acquisition due
to
the
kept
before the
the flow
peaks
in
Figure 3-10B),
procedure slightly
sharpness
and the short distance between
would result in much ment.
means
rate
min"1), leads to accurate quantification and avoids condensation of
accuracy of the data
high
acid
the IR responses would be
rates can
injected
salicylic
and pressures
peak broadening
higher
we
rates
by
attributed the first
They
To characterize the influence of the gas flow in the
evolu¬
consecutive steps, between 120 and 400 °C. The first step up
260 °C occurred with
ration process
were
al. [24]
et
by
than under
of the acetic acid
amounts
°C) the
additionally the
of evolved SA found
same
two
260
(ca.
temperature
about 360 °C
amount
(29 wt.%)
ditions (23 wt.%). However, the
at
well resolved. Acetic
are not so
higher
at
is SA and
is observed. The
steps
53
of the
injection position
but condensation
larger error than
some
peaks
or
lowers the
caused
by the
and IR cell (cf.
resublimation of SA
peak cutting in
the calibration seg¬
Chapter 3
54
3.3.4
of the Calibration Methods
Comparison
Table 3-4 compares the results of the
quantification
using
methods, pulse calibration (PC) and differential calibration (DC).
two
in situ
The
comparison
is based
the
on
amounts
of water evolved
tion of sodium bicarbonate and copper sulfate
with well-known
decompose recorded
of the FTIR spectra
quantification between
Table 3-4:
Comparison
obtained by
pulse calibration (PC)
of the
gravimetric or
(RSD) is calculated based
Sample
on
compounds
thermogravimetric
accuracy of the
applied
curves
proce¬
spectroscopic signals. and
spectroscopic results
differential calibration (DC)
of sodium bicarbonate and copper sulfate
Both
pentahydrate.
and the
comparing the
allow
simultaneously
dures used for the
stoichiometry
during decomposi¬
pentahydrate.
of
water
evolution
during the decomposition
The relative standard deviation
TG and FTIR results.
method
step
stoich.
NaHC03
1
PC
10.69
NaHC03
1
DC
10.69
FTIR
TG
-
-
RSD / %
10.87
1.68*
10.98
2.71a
5
H20
1
PC
28.84
25.82
26.35
2.05
5
H20
1
DC
28.84
24.90
25.64
2.97
CuS04
5
H20
2
PC
7.21
7.17
7.24
0.98
CuS04
5
H20
2
DC
7.21
7.35
7.26
1.22
CuS04 CuS04
•
RSD is related
to
the stoichiometric
expected value.
The relative standard deviation FTIR
results
(RSD)
is calculated based
on
TG and
results, except the decomposition of sodium bicarbonate, where TG are
neously,
expected
not
taken into
i.e. in the
same
account
results
are
C02
and
water
evolved simulta¬
temperature range. Here the RSD is related
stoichiometric value
spectroscopic
because
only.
All deviations between
to
gravimetric
lower than 3% which corroborates the
good
the
and
accuracy
Quantitative Calibration of FTIR Spectroscopic Signals
of the situ, in
applied one
methods. The fact that both these methods could be
experimental
run,
calibration
time-consuming
of injecting the fluid before
hyphenated
range of the can react
underlines their
after the
TG-FTIR
sample (allowing
with the
investigation
less
application
before the TA,
of adsorption
or
gas-
anal¬
simple quantitative
TA allows
in
opportunity
the
technique. Fluids, injected
injection after the
solid reactions), whereas
The
thermoanalyzer widens
e.g. the
applied
potential. They offer a much
procedure than generally applied. or
55
ysis of the evolved species. The
pinhole
calibration. The results
quantification
pinhole
presented
of volatile
extends the scope of
significantly
calibration method
in this
compounds.
confirmed its
study
The
and different temperature ramps
use
liquid
applicability
of different diameters of the
during
calibration
provides
opportunity of calibrating FTIR signals with liquids having very different oration
(vapor pressure)
rate
at room
achieved calibrations for methanol, acetamid with this method
experimental the
amount
parameters
found
cal of the flow
(e.g.
by means
a
constant
dimethyl changing
We showed that
proportional to
pinhole
method is its e.g.
acetone.
already during sample handling
the relation between the
amount
and
the
recipro¬
of evaporated
application
with
Part of the calibra¬
experiment settling,
liquid
and the FTIR
inaccurate.
The differential method, described in this paper, further tunities of
[21]
rate.
tion agent evaporates
integral signal
formamide and
the
evap¬
and Prozonic
application.
of FTIR absorbance is
possessing very low boiling point as
substances
Slager
flow rate, however,
flow rate) limits this
Another serious limitation of the
rendering
temperature.
xylene, dimethyl
using
for
liquid
and Marsanich
calibrations
et
al.
by
the
vaporization
extents
the oppor¬
methods described
[18,21]. Especially high volatile materials (e.g.
by Slager acetone,
56
Chapter
ethanol)
can
3
applied
be
without any limitations for
method. For the calibration, the
chosen differential time interval
of the
experiment, where already significant are
are
only
a
certain, arbi¬
taken, omitting the ill-defined
trarily
TA-FTIR data
data from
experimental
with this
quantification
losses may
mass
occur
start
before the
collected.
3.4 Conclusions
The methods of quantification of FTIR
techniques,
less
time-consuming the
as
solid reactions
tages of the
monly very can
calibration
quantification (cf. chapter 6)
pulse
used
quantification
performed
procedure which
of
in
facts and minimizes
a
and
significantly
run
experimental
errors
application
range of the TG-FTIR
(e.g.
gas-
of solids. The main advan¬
are:
compared
simplicity,
to
the
com¬
accuracy and
experiment
decreases the influence of
arte¬
shift of the base-line in FTIR cell,
flow, etc.) which
technique,
which is
characterizing reactions involving solids reactions. The extension of the
solid-liquid
quantification
be used in different stud¬
can
bias the
quantifica¬
FTIR spectra. The described calibration methods widen the
on
uid and
and easy and
The fact that both the calibration and
tion based
decomposition
applications
can
decomposition
of the FTIR spectra
single
differen¬
pulse and
adsorption phenomena (cf. chapter 5),
influence of changes in the carrier gas
able tool for
the
on
and differential calibration methods
good reproducibility. be
based
described in this work, allow in situ
tial
ies, such
signals
signals
in
very sensitive and reli¬
and gases such
as
complex
quantification by applying liq¬
solutions opens up further
of spectroscopic
a
coupled
opportunities
in the
area
TG-FTIR-MS systems.
of
Quantitative Calibration of FTIR Spectroscopic Signals
57
3.5 References
[1]
Magri,
S. Materazzi, R. Curini, G. D'Ascenzo, A.D. Acta 264
(1995)
Thermochim.
75.
[2]
S. Materazzi,
Appl. Spectrosc.
Rev. 33
(1998)
[3]
S. Materazzi,
Appl. Spectrosc.
Rev. 32
(1997) 385.
[4]
A.B.
Kiss, Acta Chim.Acad. Sei. Hung. 61 (1969) 207.
[5]
CA.
Cody,
[6]
P.B.
[7]
J.O. Lephardt, Appl. Spectrosc.
[8]
M.
[9]
L.C.K. Liau, T.C.K.
189.
Dicarlo, B.K. Faulseit, Am. Lab. 13 (1981) 93.
L.
Roush, J.M. Luce, G.A. Totten, Am. Lab. 15 (1983) 90.
Mittleman, Thermochim.
Yang,
Rev. 18
Acta 166
D.S.
(1982) 265.
(1990)
301.
Viswanath, Appl. Spectrosc. 51 (1997)
905.
[10]
M.E Cai, R.B.
[11]
B.
Roduit, J.
Smart, Energy Fuels 7 (1993) 52.
Baldyga,
M.
Maciejewski,
A.
Baiker, Thermochim.
Acta
295 (1997) 59.
[12]
M.
Maciejewski,
[13]
M.
Maciejewski,
A.
Baiker, Thermochim. Acta 295 (1997) 95.
CA. Muller, R. Tschan, W.D. Emmerich, A. Baiker,
Thermochim. Acta 295
[14]
J. Wang,
[15]
E.
B.
McEnaney,
Lopez-Anreus,
S.
(1997) 167. Thermochim. Acta 190
Garrigues,
M. de la
(1991) 143.
Guardia, Analyst 123 (1998)
1247.
[16]
A. Perez-Ponce,
Guardia, Analyst [17]
K.
F.J. Rambla, J.M. Garrigues, 123
Garrigues,
M. de la
(1998) 1253.
Marsanich, F. Barontini,
390(2002) 153.
S.
V.
Cozzani, L. Petarca, Thermochim. Acta
58
Chapter 3
[18]
F. Barontini, K.
Marsanich, V. Cozzani, J. Therm. Anal. Cal. 78 (2004)
599.
[19]
M.
Muller-Vonmoos, G. Kahr, A. Rub, Thermochim. Acta
20
(1977)
387.
Gonzalez, Catal. Lett. 54 (1998) 5.
[20]
B.H. Li, R.D.
[21]
T.L.
[22]
F. Barontini, E. Brunazzi, V. Cozzani, in Proc. 5th SKT 2003,
Slager,
RM. Prozonic, Thermochim. Acta 426
(2005) 93. Netzsch,
Selb, Germany, 2003, p. 37. [23]
A. Perez-Ponce,
lyst [24]
123
J.M. Garrigues,
S.
Garrigues,
M. de la
Guardia,
(1998) 1817.
Y. Asakura
Ribeiro, A.C.F. Caires, N. Boralle, M. Ionashiro, Thermo¬
chim. Acta 279 (1996) 177.
[25]
R.S.
Ana¬
Jackson,
A.
Rager,
Thermochim. Acta 367 (2001) 415.
Seite Leer / Blank leaf
Seite Leer / Bl&nk leaf
Chapter
4
Influence of
Measuring Conditions on the Quantification of Spectroscopic Signals
FTIR
4.1 Introduction
A
disadvantage
of classical thermal
probe sample during coming can be
the
overcome
analysis (TA)
measurement are
is that gases released from the
normally
by coupling TA with
rier-Transform-Infrared (FTIR) spectroscopy,
mass
as
it
not
analyzed.
(MS)
spectrometry was
This short¬
shown in the
or
Fou¬
previous
chapter. Besides the identification of evolved gases, their
[1-6] of
or
MS
[4,7-9] spectrometry has been addressed. The
quantification
application
of
spectrometric signals
on
the
composition.
pulse technique
First
investigated
in
Chapter
stoichiometry
of the
decomposition
using ammonia,
et
al.
method
3
the
quantifi¬
combined with TA sys¬
al. [8,10]. The extension
was
FTIR
time-consuming and requires
et
into the TA-FTIR system. Marsanich tion
common
reported by Maciejewski
coupled technique known
is
of gaseous mixtures with well-defined
cation of evolved gases based tems was
quantification by
to
by decomposing
process and
FTIR-TA
solids with
by injection
of liquids
[11] applied the gas-pulse calibra¬
carbon monoxide and carbon dioxide.
They
introduced
Chapter 4
62
vaporization technique of liquid samples for calibration
the
procedure was applied
nals. Similar
Quantification using facilitated
by the
ties of the ion
also
MS combined with the
fact that the linear
current
by Slager
and the
relationship of the
amount
In contrast,
by
evolved gases
recording
quantification
calibration
ally
the data
MS when ters
must
such
high
amount
time in FTIR is
acquisition
choosing
the
of
match that evolved
closely
poor
spectral
only
injected
in
a
(e.g. are
32
the
concentra¬
single-point
with that
cm"1).
also
wide
complicated
small
by
gas
a
time resolution.
high
a
only comparable
resolution
is
generally
time is
acquisition
during decomposition.
e.g. residence time in the IR-cell
as
is hold in
analyzed species
of evolved gases in TA-FTIR systems is
consequently
technique
between the observed intensi¬
the fact that the Lambert-Beer's law is often valid
tion range, and
calibration
be achieved with
can
sig¬
and Prozonic [12].
pulse
concentration range. Furthermore the MS data
short and
of the FTIR
Addition¬
applied
in
The other parame¬ for
important
achieving
accuracy in data collection.
A closer look
reported
on
the
TA-FTIR studies indicates that in certain
significantly
from the
Table 4-1 [4,6,12-20]. describes the ratio below
used
tribute
to
or
equal
one
indicate that
the
which
of
indicate to
most
the
a
big
can
of FTIR
investigations
acquisition
the various
Some
traces.
are
listed
in
time and residence time
of the recorded
traces:
values of this
likelihood that each molecule could be
some
signal thereby lowering
in
the conditions deviate
cases
integral intensity
likely
applied
quantification
TA-FTIR
precision and completeness
especially important, peaks,
for
Comparison
detected and contributed one
for
optimal settings
conditions
experimental
above
conditions
experimental
of recorded
traces.
of the target molecules did
the accuracy of
if pulse calibration is
result in the situation that under
not con¬
quantification.
applied, resulting extreme
in
Values
This is
generally sharp
conditions
(high
Influence of Measuring Conditions
Table 4-1
:
Comparison
of TA-FTIR systems with different
Ref.
Apparatus
on
the
measuring conditions.
Reso-
Co-
Acq.
Flow
Vol. IR
Resid.
lution
adding
time
rate
cell
time
scans
s
min"1
ml
s
cm"1
ml
63
Quantification
Quot.
Acq.
Resid.
Bruker IFS 28
[13]
4
10
-10
15
8.7
34.8
0.3
Perkin Elmer
[14]
8
4
-4
89
-10
-7
0.6
Digilab
FTS 60
[4]
8
16
-5
50
6
7.2
0.7
Bruker
Equinox
[15]
4
16
9.5
60
8.7
8.7
1.1
Bruker
Equinox
[16]
4
17.5
35
8.7
14.9
1.2
556
25
1.2
-
[17]
-
-
[6]
8
16
Midac / Nicolet
[12]
4
Nicolet
[18]
16
Bruker Vector 22
[19]
Perkin Elmer
[20]
IBM IR 85
Digilab
FTS 7
Magna
quotient of acquisition
30
-
t/ t
13
10
6
7.2
1.8
60
100
30
18
3-3
3
-3
50
0.49
0.6
5
2
16
75
100
19.7
11.8
6.4
-
-
-60
95
4.8
3
20
are not
fully
32-45
time divided per residence
time) the pulses
recorded.
Preliminary investigations clearly improper experimental settings spectra
by
the
pulse technique.
on
The
indicated
a
the accuracy of the
importance of this
cation of FTIR in combined TA-FTIR systems has
tematically
the influence of the
interpretation of FTIR traces.
significant
experimental
influence
of
quantification
of IR
aspect for proper
appli¬
prompted
conditions
on
us to
the
study
sys¬
quantitative
64
Chapter 4
Experimental
4.2
Experiments
pulse
two
or
gases
were
devices
out on a
enabling injection
Netzsch STA 449 of a certain
gaseous mixtures into the carrier gas
(Figure 2-5
tem
carried
Additionally cies after the
the
of
option
bypassing
thermoanalyzer (into
calibration without
contact
of the
the
the
bration is less
model 5850E, based
(purity to
on
rate was
a
transfer-line)
calibrating pulse
200 ml min
.
The
to a
the FTIR spectrometer
with the
flow
mass
were
by
used
were
used
as
passed through mass
carrier gases with flow was
connected
by
a
rates
a
heated (ca. 200 °C)
from
heated
(ca.
leaving
capillary
to a
equipped
with
a
MCT detector and a
123
mm
an
espe¬
path length
and
the cell
was
compounds
temperature of 200 °C. The whole FTIR compartment
minimize the
water
and
additionally
and carbon dioxide
spectra. The resolution of the collected spectra and co-addition of 4
Helium and
spectrometer.
continuously purged by nitrogen to
sam¬
and therefore cali¬
sensing technique.
ZnSe windows. To avoid condensation of low volatile
was
spe¬
flow controllers, Brook's
mass
low-volume gas cell (8.7 ml) with
to a constant
investigated
Bruker Vector 22 FTIR spectrometer. Gases
The FTIR spectrometer is
heated
were
used, which enabled
was
sharper signals
thermoanalyzer
Pfeiffer Omni Star GSD 301 O
cially developed
controlled
thermal
99.999%, PanGas)
°C) transfer-line
200
the sys¬
flowing through
(vide infra).
accurate
The carrier gas flow
12.5
different
thermoanalyzer by injecting
This alternative method results in much
argon
or two
used.
mainly
ple.
of one
Volumes of 0.25, 0.5, 1.0 and 2.0 ml
Chapter 2).
in
amount
stream
with
analyzer equipped
scans
per spectrum
was
molecular sieves
background
was set
applied.
in the recorded
between 1 and 32
As
a
were
cm'1
consequence spectra
Influence of Measuring Conditions
recorded with
were
MS
ing
to
charge
monitored Data
temporal ratios
versus
FTIR
for
C02
temperature
acquisition
time
was
tion time could
only
be
or
and
H20
The few characteristic
species.
m/z=44 and 18,
time in the
cost
on
the inte¬
the FTIR chamber result¬
multiple
respectively)
were
ion detection mode.
relatively short, generally about
applied
on
65
resolution.
of the evolved
traces
(e.g.
spectral
performed directly after
measurements were
in similar
mass
applied
Quantification
depending
time resolution of about 2-20 s,
a
methods and
gration
the
on
2
s.
Such
acquisi¬
an
of low resolution i.e. 32 cm"
in the
FTIR system.
NaHC03 (p.a. Merck) ence
samples with
and
well known
CuS04
mass
of NaHC03
of CuS04
mass
5
For the gas
moanalyzer.
loop
of
a
H20
were
a
wide range of
home-made device valve
sample
In order
to
injected generally
A standard
used
C02
as
refer¬
In order
to
concentrations the
sample
50 mg.
which had been
composition.
known volume
a
were
varied between 2 and 420 mg, while the
rotary
a
given volume,
gated sample.
was
injections
It contains
gas of known
was
H20 (Fluka AG)
stoichiometry of the decomposition.
check the behavior of the system in
sample
5
heating
rate
was
placed
before the ther¬
enabling a carrier gas
previously
quantify
before the
to
purge the
filled with the calibration
the FTIR
signals, pulses
decomposition of the
of 10 K min'1
was
applied
of
a
investi¬
for all decom¬
positions.
4.3 Results and Discussion
From
preliminary investigations
parameters
can
it
emerged
affect the accuracy of the
that the
following experimental
quantification
of FTIR
signals:
sam-
Chapter 4
66
pie
mass,
place of the injection of the calibrating gas,
of the spectrometer and were
compared with
icant
optimization
of the FTIR
the
on
Sample
of PulseTA
increase of the accuracy
to
Mass and Concentration of the for
C02
Target
Gas
quantitative interpretation of FTIR signals
Figure
of C02 where different
TA-FTIR-MS system.
signif¬
method.
the Lambert-Beer's-Law.
example
MS data, which allowed
simultaneously gained
quantification
application
based
the
flow, resolution
time in the IR cell. FTIR data
of the various parameters and led
4.3.1 Influence of The
accordingly acquisition
carrier gas
traces
4-1 shows the of the gas
amounts
were
pulse
monitored
were
using
calibration
injected
two
is
using
into the
characteristic
50^ «
1
402350
,
3
cm"1
1 3600
CO ~~
30-
1
cm'' .
_
8
4000
3500
3000
2500
wavenumtwr /
n
20-
co
f-i—3600 cm"1 VV
()
2000
1500
cm''
A
1
LI
1 ml
0.5 ml
J
2 ml 1
cm"'
,
I
i
10-
0-
2350
IL. 0.25 ml
i
1
i
i
10
20
30
40
time / min
Fig.
4-1
:
intensity of C02 signals recorded in TA-FTIR system for the wavenumbers 2350 cm"1 and 3600 cm'1, respectively. Carrier gas:
Pulse calibration:
characteristic 100 ml min"
He, resolution: 4
cm"
.
Inset:
IR-spectrum of C02.
Influence of Measuring Conditions
), which
is
much lower FTIR
are
integral
shown in
intensity,
intensities /
Figure
(overtone band, peak-3600 and interferes with
(Eq.
2 in
4-2 :
F
1
1
1
0.0
0.5
1.0
1.5
Relationship cm"
between
injected
from
at
quantification
cm"
pur¬
), which shows
bands in the
same
region.
from calibration
pulses
1-
2.0
volume / ml
volume and
regions:
integral intensity
of evolved
C02
solid circles: 3600 cm" and open cir¬
.
The absorbance of the evolved recorded
67
4-2.
measured in TA-FTIR system for different IR cles: 2350
water
Chapter 3) resulting
injected
Fig.
Quantification
for identification and
widely applied
poses and 3780—3480 cm'
The
the
regions, namely 2450-2150 cm"1 (asymmetric stretch, peak-
wavenumber 2350 cm"
on
2350 cm"
than
at
was
much
3600 cm" and this led
linearity during injections
observed for 2 ml
C02
of higher
injections deviated by
amounts
larger
to a
for the
significant
of C02.
Integral
13.9% from the linear
traces
deviation
intensities
dependence
for
Chapter 4
68
the
traces
earity was
recorded for 2350 observed
Figure 4-3
whereas for 3600 cm"
relationship
and the
dependence
between
between the
traces
integral intensity
gained
of the
(13 mg of evolved C02). Quantification based ever,
could be achieved
spectral sample was
even
resolution of 4 cm" masses over
obtained
using
small non-lin¬
100 mg
the
up
and
at
2350
signal
C02
and
sample (ca. rate
mg of evolved
decomposed
as
determined
cm"1 show
the band
on
carrier flow
a
(ca. 26
signal
400 mg
to
at
of the
mass
of evolved
integral intensity
the TA-FTIR system. The
using
only
(-3.2%).
shows the
sample (NaHC03)
cm'1,
mass
up
to
3600 cm"
at
105 mg
C02)
of 50 ml min"
C02)
no
linear
linear
a
50 mg ,
how¬
with
a
He. For
relationship
cm"1 biasing quantification.
2350
80000
3 «
60000
o
(overflow)
200
sample
Relationship between the gral intensity of evolved C02 measured Fig.
4-3
:
open circles: 2350 cm"
mass
.
500
300 mass
of the
/ mg
investigated sample (NaHC03)
and inte¬
in TA-FTIR system: solid circles: 3600 cm"
Carrier gas: 50 ml min"
He, resolution: 4 cm"
.
and
Influence of Measuring Conditions
4.3.2 Influence of Parameters of
on
the
Data-Acquisition
Quantification
and Carrier Gas
Figure
4-4 illustrates the influence of the parameters of data
other
experimental
recorded shows tion
was
injected can
be
on
the
recorded with different
made before the gas with the
injected
thermoanalyzer,
investigated sample
into the carrier gas
resolutions.
but in the
has
by-passing
case
traces
C02. Figure
where
4-4a
the
injec¬
contact
of the
Generally
be avoided, the
to
calibrating
the TA chamber. This
,4cm1
100 ml
of 1 ml
injection
spectral
acquisition and
intensity of C02
and
shape
the TA-FTIR system after
using
pulses
conditions
69
gas
procedure
(6)
mm'1 (24) Ar (39) 50 ml
mln"1 (57) 25 ml
time /
Fig. es
4-4:
min1 (139)
time / mln
mm
Influence of the
experimental conditions
recorded in TA-FTIR system after
(> 1% of maximal intensity) before TA,
(C02
(C02
traces at
resolution 4
traces at
3600
cm"
,
cm"1).
(C02
the
on
shape and intensity of C02 trac¬
injection of 1 ml C02. Numbers of recorded data points
given in btackets. A: Carrier gas: 50 ml min" He, injection 2350 cm"1). B: Carrier gas: 50 ml min" He, injection after TA, are
C: Carrier gas: 100, 50 and 25 ml min"1 He,
traces at
tion before TA, resolution 4
cm"
injection
2350 cm" ). D: Carrier gas: 50 ml min" ,
(C02
traces at
2350
cm"
).
before TA,
He and Ar,
injec¬
4
Chapter
70
leads
much
to
which allows
the small distance between
points
the
at
much lower than in the
tively large
same
case
in
Figure
where the
broader
in
Figure
on
nificantly
data-points
of the evolved gas. Similar tative calibration of mass
zone
higher diffusivity
(marked
gas
Due
.
in
brackets)
passed through
points
increases with
not
concentra¬
only by low¬
in helium result in
to
of the
higher diffusivity
of helium enables the collection of sig¬
in helium
significantly
gas.
of different carrier gas. The
C02 pulses
which results in better
C02
was
the rela¬
injected
maximal
be caused
can
than in argon due
dependence was
of
to
the number of
in dilution of the
by the application
description
observed
of the real
by Roduit et al. by quanti¬
compared
increases to
traces
to
the
argon, the mixed-flow
to
leading
to
peak broadening.
of certain
injections
amount
of
into the carrier gas is smaller in helium than in argon.
illustrates the
relationship
tion time and the residence time of
between IR-resolution, the
injected
molecules.
and NO spectra recorded with different
and 32 cm"1. The
application
of high
spectral
e.g.
acetylene
and
hydrogen cyanide.
For
Figure 4-5A
spectral
resolution
tification of specific mixtures where the vibrational as
sensor
cm"
spectrometric signals [7]. They found that due
in the TA chamber
Figure 4-5
C02
3600
intensity
shape and intensity of FTIR signal
signal
However, the maximal concentration due
C02
at
lowering of the
to
of the
Application
gas in helium.
more
the
4-4D show that
peaks (larger tailing)
investigated
much
tailing
carrier gas flow but also
presented
signal
4-4C. The number of recorded data
tions in the FTIR cell. The
results
injected
maximal
huge
detecting
resulting
decreasing flow rate leading additionally
ering the
a
carrier gas flow
volume of the TA chamber
presented
and
injection
The influence of the carrier gas flow is
the weaker
quantification using only
recorded data
with
sharper peaks (Figure 4-4B)
NO,
at
acquisi¬
shows the
resolutions between 1
(2
signals
cm"
) allows
of both gases
higher resolution,
quan¬
overlap
even
dif-
Influence of Measuring Conditions
on
Quantification
the
71
c (0 o
2600
2200
2000
wavenumber /
flow / ml
1800
1600
cm'1
min1
a) d
9
resolution /
Fig.
4-5
:
Influence of selected
corded with different
spectral
centration of both gases:
ca.
spectral
resolution of FTIR: A:
1 % in He. B:
Relationship
chamber)
between
are
and NO spectra
re¬
scaled up (xlO). Con¬
acquisition time, spectral
in TA-FTIR system. Number of
averaged
4.
ferentiation between olution has
a
isotopes
significant
is
possible. However,
drawback in
increase the accuracy of quantification
has
C02
resolutions. Intensities of NO spectra
resolution and residence time (FTIR scans:
cm1
to
be decreased, which
can
dynamic at a
the
TA
given flow
application
experiments. rate,
the
only be achieved by lowering
of high
In order
acquisition
the
res¬
spectral
to
time
résolu-
Chapter 4
72
tion,
shown in
as
poral acquisition comparable
The
of 21.5
the
to
quantification
Figure 4-5B. High resolution, s,
and low resolution time of
acquisition
in this
as
be
to
quantify properly
to
in the gas cell estimated
strictly
by
the
Figure 4-5B (carrier
dependences presented required
for
the
when
example,
For
10.4
in this
using
a
or
1 cm"
,
data
through
allows
figure
of the traces,
not
be
The
needs
residence time it is
residence time
maximal resolution
a
quantification.
accurate
of 50 ml min" than 4
cm"1.
time
larger
a
(residence
For
higher
than 10.4
resolu¬
(11.7
s
min"1 part of the
target gas
species will not be accounted for, leading to erroneous quantification. investigating the influence of the experimental
integral intensity allowing
exact
of FTIR
to
the IR
experiments we compared previous
independent study.
signals
of the
apply
applied
we
the data obtained
integral
experimental conditions,
This observation allowed
pretation
to
an
us to use
intensity of IR signals
conditions
independent
obtained in different
technique,
studies [8,10] the of
has
one
comparison of signals
studies, parallel
our
ml
s
time
s,
When
using a flow of 50
upper
comparison of both
The
enabling
as an
and 21.5
respectively),
therefore when
mean
the system, is shown
choosing
rate
higher
acquisition
mean
long acquisition
too
reciprocal scale).
carrier flow
s), the resolution should
tions, i.e. 2
used for
between the volume of the IR cell
quotient
gas flow:
good description
a
a tem¬
in 2.1 s, the latter is
correlated with the
analyzed species.
compartment and the carrier gas flow line in
32 cm"
results in
spectrometric signals
mass
time of the evolved gas in the FTIR gas cell. For
impossible
cm"1,
e.g. 1
study.
time has
acquisition
as
mass
on
the
reference
experiments.
In
our
spectrometry. In all
by both techniques. As reported
intensities of MS as
signals
are
in
almost
also corroborated in the present
the MS
signal
as a
reference for inter¬
obtained under different conditions.
Influence of Measuring Conditions
In order
compare the FTIR results obtained
to
mental set-ups with the MS results,
signals
MS
and
tative FTIR
injected a
provides a reasonable
analysis. Figure
in He recorded
by
a
corresponding
4-6 shows the
that
acquisition
(2.1
s
times in this
for FTIR and 2
s
for
integral
signal
73
different
experi¬
integral
largest
correctness
case were
almost the
of the
quanti¬
intensities of 1 ml
C02
recorded
using
amount
the factor F is
illustrated in
as
intensities of FTIR and
FTIR and MS. For the FTIR
MS
Quantification
by using
criterion for the
low resolution of 32 cm"1 where the
lected and
the
introduced the ratio F
we
4-6. F is the normalized ratio between
Figure
on
signal
of data
points
deliberately set same
for both
are
to
col¬
1. Note
techniques
MS).
50-
3.5
-3.0
40-2.5
_o
ca
0.5-
0.0-
0
10
20
30
60
50
40
time / min
Fig.
4-9 :
calibration of the
Influence of the carrier gas flow
(injection
decomposition (ml min"1).
of 1 ml
C02)
traces are
and
on
the
shape
decomposition
of FTIR
of 20 mg
normalized. Carrier gas flow
signals
measured
NaHC03.
rates are
during
The intensities
indicated
on
the
curves
Influence of Measuring Conditions
traces are
normalized. With
increasing
compared to the decomposition ) show
50 cm"
decomposition
a
traces.
larger tailing, The
traces.
is shown in
Figure 4-9
Quantification
the calibration
as
On the other
clearly
quantification 4-10. This
Figure
intensities of the calibration and
integral
gas flow. The
ison of
rate
the
peaks
amount
integral
the upper part of the
plot.
emerges from
figure depicts
calibrating
the
sample
dependence on
determined
compar¬
amount can
E 13 CD C
rati0.^tomB2-94 25000: -2
cd -"
of the
is shown in
decomposition peaks
The deviation from the stoichiometric
in
the carrier
by
-4
^
and
presented
traces
decomposition signals
intensities of calibration and
become
hand, lower flow rates (25
of the FTIR
of C02 evolved from the
77
significantly
and the value of their maximal concentration increases
sharper
or
flow
on
CD T3
^decomposition
20000'
&
o O
1
S
15000'
S
10000"
-0 CO
S 5000'
-
100
12.5
200
flow / ml min"
Fig. nals
Dependence
4-10: on
of the
the carrier gas flow. The
integral amount
Figure.
tion of 1 ml
C02
The
of evolved
C02 determined
decomposition sig¬
from the
comparison of
decomposition (open circles) signals is presented in stoichiometric value for the sample mass 20 mg NaHC03
calibration (solid circles) and part of the
intensities of the calibration and
amounts to
2.94.
the upper and
injec¬
Chapter 4
78
easily
be
more
the
seen
when
narrow
increasing
However,
disadvantage, flow in
rate
e.g. when
visible also in
of the
tailing
reactions have
This
signal.
more
to
phenomenon the real
thermogravimetric
4-11
depicting
the
6
occurring
stages
25^
CO
50
difficulty
in
clearly
a
Lower
visible
of the reaction
(DTG, dotted line) This aspect is
multistage dehydration
The results illustrate the
dehydration
is
course
curve
also
cases,
investigated.
be
represented by spectrometric signals.
Figure
pentahydrate.
consecutive
multistage
the differential
differs from those
broad
relatively
of low carrier gas flows has, in certain
The lower the flow rate, the
represented by
influences much
decomposition.
application
increases the
Figure 4-9:
fate
the
course
calibration than the
during
obtained
peaks
signals resulting from
the flow rate, which of
clearly
of copper sul¬
separation
of the
in the range 60-120 °C. The
two
water
A
(\ ;V\
-_
iooJ
8 co
CO
co
3
t\V_^
„100E -
90-
change
o
8
70"
TG
CD
E
eo
•
50
i
'
100
150
250
200
3C
temperature / °C
Fig.
4-11
:
carrier gas flows. curves
during dehydration of 50 mg CuS04 5 H20 measured at different Heating rate: 10 K min"1, carrier gas: He, flow rates are indicated on the
Water
'
traces
(ml min"1). Corresponding TG
traces are
shown in the lower part.
Influence of Measuring Conditions
traces
fied
recorded
properly
due
to
partial ovetlap.
of these
splitting
heating
rate,
system and
79
be
quanti¬
In contrast,
can
can
using
cannot
carrier gas flow of
a
be determined. Note that
also be achieved
by
e.g.
decreasing
the
however that lowers the concentration of the detected gas in the
consequently the
by pulse
spectra
peaks
two
example indicating
An
Quantification
carrier gas flows of 25 and 50 ml min"
min"1 the contribution of these peaks
100 ml
better
using
the
on
accuracy of quantification.
how the
procedure
calibration with gases
mental parameter
settings
is
in
given
can
quantification
of the
be influenced
by
Figure 4-12, which
of FTIR
different
experi¬
presents the
C02
"
CO -
,
134.7%
S c ca
o CO
COSHB
(23)/
[(4)
V^
\
co
:
! v*>
99.8%
my
-
—i—
i
i
30
40
i
i
10
0
20
5
time / min
Example of quantification of FTIR traces by pulse technique during decomposi¬ tion of 20 mg NaHCOj. Numbers of recorded data points (> 1% of maximal intensity) are 4 given in brackets. A (open circles): Carrier gas 200 ml min"1 Ar, resolution 1 cm" (pulse: Fig.
4-12
:
,
points).
Calculated
amount
of C02 in the
sample amounted to
134.7% of the stoichiometric
value. B (solid circles): Carrier gas 50 ml min"1 He, resolution 4 99.8% of C02
was
determined.
cm'1, (pulse:
57
points).
Chapter
80
recorded
traces
according to
2
4
calibration
during
the
and
pulses
of
decomposition
NaHC03
following reaction (Eq. 1):
NaHC03 —> Na2C03
H20
+
(1)
C02
+
technique with different experimental set-ups A and B reported in Figure 4-12. C02 amounts (%) quantified by MS and FTIR related to sto¬ ichiometric value are given. F is the normalized ratio between integral intensity of FTIR and
Table 4-2 :
Results of the
MS calibration
pulse
calibration
signal (decomposition peaks
were
normalized). F/-
FTIR/%
MS / %
Set-up A
(open circles)
102.9
134.7
0.76
B
(solid circles)
99.2
99.8
0.99
Table 4-2 compares the results of the
Figure 4-12 using pulse
recorded
traces
different
experimental
amounts
of C02 evolved
to
quantification
shown in
parameters. The
the stoichiometric value.
Experiment
using high spectral
(200 ml min"1 Ar) led
temporal
low
high
to a
resolution
large
error
resolution (collection of
maximal
the calibration
intensity significantly
pulse
were
only
B
(solid circles)
regards quantification:
a
flow
was
rate
the calculated
shows the used: the
high
that
error
sharp pulse
carrier gas flow
quantification.
Due
rate
to
the
points during injection) and the
lower values of the
resulting
found
4
were
and
in the FTIR
C02 originating from the decomposition
Experiment
cm"1)
(1
on
of sodium bicarbonate related
had been introduced when unsuitable parameters observed
is based
(open circles)
A
significantly
calibration with
comparison
during decomposition
of the FTIR and MS
integral
intensities of amount
of
conditions
as
in overestimation of the
reaction.
performed
of 50 ml min"
under was
optimized
chosen and
spectral
reso-
Influence of Measuring Conditions
lution
was set to
and led
pulse
4
cm"1,
which
to a more accurate
and FTIR results obtained rated that
the
Quantification
proper
experimental
C02
trace.
MS
(B) corrobo¬
conditions
quantification of spectral signals
81
the calibration
points during
determination of the evolved
using
accuracy of the
high
57 data
provided
on
can
be achieved
with both TA-MS and TA-FTIR. We have shown the
tions, in order
to
such
data
acquisition
into
account
time
when
of FTIR
signals.
improve
the
Several param¬
quantify evolved gases by the pulse technique.
carrier flow rate,
eters
as
importance of choosing adequate experimental condi¬
resulting the
setting
We
injection location,
hope
quantification
from the
spectral
experimental
optimal the
study helps
gas and
injected
resolution have
conditions
that the present
of
amount
be taken
to
for calibration
practitioner
to
of evolved components in combined TA-FTIR
investigations.
4.4 Conclusions
Quantification MS
using
mental sen
or
of evolved gases
FTIR spectroscopy
settings. Quantification
experimental
most
are:
to
resolution leads
to
separation of the
shown for the
based
on
properly
spectral
the
analysis by
careful
FTIR is
pulse technique of the
optimization
strongly
analysis
is
affected
only
by
quantification by
of CuS04 chosen
•
5
the cho¬
means
resolution and carrier gas flow
reaction steps
experi¬
little affected. The
of TA-
rate.
flow poor time resolution. Low carrier gas
to
dehydration
MS system with
requires
be considered in gas
the choice of the
spectral poor
thermal
parameters, whereas MS
important factors
FTIR
during
rate
High leads
during multistage decompositions, H20.
experimental
The
application
as
of a TA-FTIR-
conditions allows
an
easy and
Chapter 4
82
less
time-consuming
ent
studies, such
as
in situ calibration
the
quantification
gas-solid reactions (cf. chapter 6)
and
procedure
which
of adsorption
can
be used in differ¬
phenomena (cf. chapter 5),
decomposition of solids (cf. chapter 3).
4.5 References
[1]
Magri, Thermochim.
S. Materazzi, R. Curini, G. D'Ascenzo, A.D.
Acta 264
(1995) 75.
[2]
S. Materazzi,
Appl. Spectrosc.
Rev. 33
(1998) 189.
[3]
S. Materazzi,
Appl. Spectrosc.
Rev. 32
(1997) 385.
[4]
M.
[5]
L.C.K. Liau, T.C.K.
Mittleman, Thermochim. Acta 166 (1990) 301.
Yang,
D.S.
Viswanath, Appl. Spectrosc. 51 (1997)
905.
[6]
M.F. Cai, R.B. Smart,
[7]
B.
Roduit, J.
Baldyga,
Energy M.
Fuels 7
(1993) 52.
Maciejewski,
A. Baiker, Thermochim. Acta
295 (1997) 59.
[8]
M.
Maciejewski,
CA.
Muller,
R.
Tschan, WD. Emmerich,
A.
Baiker,
Thermochim. Acta 295 (1997) 167.
[9]
J. Wang,
[10]
M.
[11]
K.
B.
McEnaney, Thermochim.
Maciejewski,
A.
Acta 190
(1991) 143.
Baiker, Thermochim. Acta 295 (1997) 95.
Marsanich, F. Barontini, V. Cozzani, L. Petarca, Thermochim. Acta
390(2002) 153.
Slager,
[12]
XL.
[13]
E. Post, S.
(1995)
1.
EM. Prozonic, Thermochim. Acta 426
(2005)
93.
Rahner, H. Mohler, A. Rager, Thermochim. Acta 263
Influence of Measuring Conditions
[14]
I.
on
the
Quantification
83
Pitkanen, J. Huttunen, H. Halttunen, R. Vesterinen, J. Therm. Anal.
Cal. 56 (1999) 1253.
[15]
F. Barontini, K.
Marsanich, V. Cozzani, J. Therm. Anal. Cal. 78 (2004)
599.
Jackson, A. Rager, Thermochim.
[16]
R.S.
[17]
R.
[18]
A. Perez-Ponce,
Bassilakis, R.M.
lyst [19]
A.I.
123
(1998)
Carangelo,
M.A.
J.M. Garrigues,
S.
Acta 367-368
Wojtowicz,
Garrigues,
(2001) 415.
Fuel 80 (2001) 1765.
M. de la Guardia, Ana¬
1817.
Balabanovich, A. Hornung, D. Merz, H. Seifert, Polym.
Degrad.
Stab. 85 (2004) 713.
[20]
WM.
Groenewoud, W de Jong, Thermochim. Acta 286 ( 1996) 341.
Seite Leer / Blank leaf
Chapter
Gas
Adsorption
5
Zeolites
Studied
on
PulseTA®
catalytic
5.1 Introduction
In this
chapter
described. try, the
an
Using hyphenated
quantity
gas
is
sion of
species
provide
sites. The selective
monolayer,
in the
(adsorp-
gas
and the various thermal effects combined with the
information
chemisorption,
atoms
a
is
The determination of the
on
the
and
amount
i.e. formation of a
nature
accessible
on
is
expressed
the surface
to
of active surface
strongly bound
allows the determination of the metal surface
number of metal
area
adsorbed
and metal
disper¬
the ratio of the total
as
the total number of metal
sample.
measurement
volumetry
spectrome¬
is studied.
supported catalysts. Dispersion
The
research is
with differential
adsorption
which includes the processes involved whenever
of adsorbed
above process
atoms
analysis-mass
brought into contact with a solid (adsorbent).
amount
in
frequently used method for characterizing heterogeneous catalysts
adsorption,
tive)
simultaneous thermal
of adsorbed gas and their heat of
scanning calorimetry (DSC) A very
of
important application
and
of gas
gravimetry,
chromatography
or
well
gas thermal
previously pretreated adsorbate gas. The
as
uptake as
is carried
with
out
dynamic
conductivity [1].
and evacuated, is contacted
amount
static methods such,
by
flow In
by
techniques
volumetry, a
known
of adsorbed gas is determined
such
the
as
as
gas
catalyst,
quantity
of the
by measuring
the
Chapter
86
5
pressure after the
versus
equilibrium
pressure.
understanding the method, the
Recently,
a
nature
amount
new,
so
of the
catalytically active sites [2-4].
of adsorbed gas is measured
called
element
tapered
technique has been developed that offers in
a
fixed bed
mass
reactor
is determined
element
probe
molecules
[7], the
In
bypass
the
contrast to
the
maximum adsorbed
Dynamic
methods of measuring
they
than static methods because tinuous flow
technique,
detector
stream
determined
adsorption
desorbing
(generally
a
thermal
An
been
on to
et
more
al.
well
convenient
systems. In the
by
is flushed
species.
inert gas
an
After
con¬
cooling
at a
to
the
the adsorbate gas until the down¬
conductivity cell) the
modification of the conventional
recently reported by
which
Rebo
shows
a
adsorptive
constant
is
gas
once more
investigate possible reversible adsorption.
interesting
instrument
faster and
vacuum
phase composition. After purging with an inert gas, switched
of the
systems.
all adsorbed to
none
reported by
as
oscil¬
tapered
of the
The
sample.
the
by TEOM correspond
are
require
temperature, the flow is switched
required
however,
pretreated catalyst
the
temperature sufficient for
frequency changes
not
sample.
measuring mass changes
passed through
gravimetric
do
gravimet¬
the
conventional microbalances,
amounts
with values obtained in conventional
In the
in
helps
oscillating microbalance (TEOM)
are
sample holder,
with calo¬
which
by weighing
method for
a
while reaction gases
by monitoring
[5,6].
lating
adsorption,
of
amount
Volumetry combined
allows the determination of the heat of
rimetry
ric
the
the
i.e.
adsorption isotherm,
allow the determination of the adsorbed gas
is established. Successive doses of gas
adsorption equilibrium
was
equipped
Brown and Rhodes
with
a
permitted switching between
tive gas in the carrier gas. The
gravimetric
method has
[8]. A combined TG-DSC
pneumatically operated three-way valve, a
sample
and pure carrier gas was
dosed with the
a
blend of 5%
adsorptive
in
reac¬
a con-
Gas
trolled
phase
stepwise
prerequisite irrespective
ena,
is
ture
always
involves
a
probe
lead
to a
tion
higher
temperatures
thermodynamic equilibrium
between the
not
not ensure
energetically
that
begin
to
that each dose of adsorptive
mobility
The
technique
for
of the
In
common
practice,
equipments.
makes it
possible
surements.
are
low
too
of physisorbed mole¬
stronger active sites would be
can
enough
interrogate
at
the
adsorption
tempera¬
all of the available
adsorbed molecules
adsorp¬
checked
be
can
which has become
amount
desorption
of desorbed
process, this
the determination of the
a
by
com¬
very
species
being
to
demonstrate that
we
study
all these
compared
to
amount
and indi¬
related
to
the
of adsorbed
species,
different
experi¬
study of the desorption require
Here
set-up. Results of ammonia
technique
mobility
hand,
between adsorbate and the surface.
the heat of adsorption and the mental
On the other
characterization [10]. The information collected
catalyst
the temperature range of the
energies
and low.
fill [9].
from TPD studies contains the type and
bond
[4].
allow sufficient
temperature-programmed desorption (TPD),
cates
gas
used. The choice of tempera¬
high
coverage of the surface
before weaker sites
sites.
mon
composition of the
High
Adsorbate molecules should be mobile ture so
87
molecules and the active surface sites, whereas low tempera¬
cules and thus do
populated
technique
between
achieve
to
temperatures do
adsorption
of the
compromise
reduce the time needed
tures
Zeolites
investigating adsorption phenom¬
selection of temperature, when
Proper
adsorbed
the
by repeatedly switching
on
the adsorbent.
over
a
fashion
Adsorption Studied
pulse
phenomena using
adsorption
measurements
corresponding
thermal the
same
by
means
analysis [11] experimental of the
data derived from volumetric
pulse mea¬
Chapter
88
Experimental
5.2
Experiments with two
a
carried
were
different pure gases
10 ml.
controlled mass
flow
200
by mass
flow
of injected gas could be
amount
amount
(Pt crucible, o.d.=6.8
from
a
remove
amount
these
mm,
on
the
out on
adsorption the
at
200
ammonia and
of chemisorbed ammonia
isotherms, according
to
the
a
through bridging
0.67
nm x
0.70
nm
20-400 mg
was
where
investigated.
with the
with those same
reac¬
measuring
evacuated in order was
to
measured. The
generally applied procedure [12].
tetrahedrally a
as
adsorbents,
are
coordinated Al and Si three-dimensional pore
interconnected channels of dimensions 0.53 a
to
experiments
process
was
heated
a
calculated from the difference between
was
oxygens. ZSM-5 has
Mordenite possesses
in the
second isotherm
The zeolites, ZSM-5 and mordenite, used minosilicates made up of
ml))
by the pulse technique
°C, the system
thermal
25-30 mg for DSC
ca.
measurements
to
spectrometer
mass
Micromeritics ASAP 2010 system. After
isotherm
physisorbed
ml)
by
0.01
rate was
on a
connected
quadrupole
adsorption
compare the results obtained
carried
was
or
flowing
stream
changed from
volume 0.085
o.d.= l6.4mm, volume 1.0
conventional method, volumetric
tants were
the first
to
Balzers
to a
of one
used. The flow
of the adsorbents varied from
the influence of the bed thickness In order
were
thermoanalyzer
The
°C) stainless steel capillary
(alumina crucible,
amount
controllers, Brooks's model 5850E, based
sensing technique.
measurements
certain
gaseous mixtures into the carrier gas
0.25, 0.50 and 1.0 ml volumes
420. The
QMG
or
the system. The
Mainly
thermoanalyzer equipped
Netzsch STA 409
out on
(Netzsch) enabling injection of a
device
pulse
through
(ca.
5
nm
x
0.57
nm
crystalline aluatoms
bonded
structure
with
and 0.55
nm.
two-dimensional channel system with dimensions
and small
perpendicular
pores with dimensions 0.29
nm x
Gas
0.57
nm
[13]. The zeolites were received
AG. After calcination
NH4N03
at
they
500 °C
and heated in air
to
the
the gases adsorbed
able.
were
used
Additionally,
as
silica-titania
Ni-5256 E3/64)
(Engelhard
used
89
90 °C with 1 M
at
thermoanalyzer
then
until
change
a
500 °C
was
to
detect¬
argon
(purity
commercial nickel
catalyst
and helium
and
to
cooled down
they were
no mass
and carrier gases,
aerogel [14]
were
Zeolites
obtain the H-form. Before the
heated in the
equilibrated
adsorptive
exchanged
to
(purity 99-98%, PanGas)
Ammonia
99.999%)
ion
during handling,
temperature and
measuring
were
were
on
in the Na form from Chemie Uetikon
500 °C for 2h
adsorption experiments samples to remove
Adsorption Studied
or
respectively.
adsorbents.
as
5.3 Results
Figure
5-1 shows the
from
series of ammonia
a
mass
changes
pulses,
technique. Strong, virtually
injected
ammonia occurred
and weak
of the H-ZSM-5 zeolite
and illustrates the
irreversible
weight water
by
6 in
loss
Figure 5-1,
amount
depicts at
features of the
pulse
of the
4 resulted in both strong
where
took
no
place.
further
The
mass
the temperature range of the
gain at steady state,
changes
desorption
temperatures above 550 °C is due
as
mass
6
were
detectable,
of chemisorbed ammonia. The second part of the exper¬
from the zeolite, the
205-550 °C, nal.
resulting
(reversible) adsorption phenomena, whereas during pulses 5 and
represents the iment
200 °C
adsorption (chemisorption)
during pulses 1-3, pulse
only weak adsorption (physisorption) indicated
typical
at
confirmed
desorption
to
(TPD). The
the evolution of residual
of ammonia
by monitoring the
process
m/z =15
occurs
mass
in
the range
spectrometric sig¬
Chapter
90
5
3.0
2.5
-
2.0
-
Ol
E
1.5
Ol Ol
1.0
«S .e u t/i
vi
nj
0.5
5
0.0
-0.5
Time / min
Fig.
5-1
monia
Mass
:
at
200 °C. The
10 K min"
.
The
In the ence
changes of H-ZSM-5
on
zeolite after exposure
desoiption after
amount
the 6th
was
initiated
of chemisorbed ammonia is marked
following, experimental
the
pulse
adsorption
series of pulses of 1 ml
to a
as
by heating
am¬
at a rate
of
0.
influ¬ parameters which have the greatest
process under
dynamic conditions,
were
investigated.
These parameters embrace: thickness of the adsorbent bed in the crucible,
tem¬
perature and carrier gas flow.
5.3.1 Influence of Thickness of Adsorbent Bed The conditions for mal for the not
flow
tion due
gas-solid
through to
effects and
mass
the
transport in the
experimental set-up
are not
typical thermoanalyzers
sample bed,
influence the kinetics of the
this
can
check the
reproducibility
to
study the
opti¬
the gas does
interaction. As in all
diffusional limitations. In order to
used
adsorp¬
influence of diffusion
of the method, the
sample
mass was
Adsorption
Gas
varied
over
amount
a
range from 10
to
independent of crucible
of the
was
sample
used
mass
at
°C, related
200
i.e. the bed
(open symbols
to
of zeolite, did
and lower
amount
The
ammonia
(solid symbols). However,
influence the
not
use
mass
100
_J
specific
the
same
kind
of the DTA cruci¬ in
amount
a
thicker bed
of chemisorbed
significantly
/ mg
i
l_
i
250
200
150
I
i
91
adsorbent, is
the thickness of the bed
Sample 50
that the
1 g of
(smaller diameter), resulting
ble with its different geometry
Zeolites
provided
thickness,
Figure 5-2A).
in
on
Figure 5-2A shows
400 mg.
of chemisorbed ammonia
Studied
500 o
£
•|
O«
450
•
IL
O
-o
o
E Ë
a"
(0
"8 -S
400
o 1/1
£
4
N2
+
and NO, and the consump¬
catalysts
are
suitable for
temperature window 300-400 °C At
appli¬ higher
Chapter 6
110
temperatures (> 400 °C) nitrous oxide is formed [3]. One of the
leading
tions
to
nitrous oxide is: 4 NO
Catalysts working their
NH3
02
3
+
—>
4
significant
N20
+
6
have been shown
NH3 (a)
+
NO
(g)
NH2 (a) OH
(a)
O
SCR of NO
+
+
ions
on
transition metal
(1)
(2)
NH3 (a) (a)
—>
NH2 (a)
OH
+
N02 (a)
(g)
—>
NH2NO (a)
N02 (a)
—>
O
NO
and Mn
oxides [5] :
—>
+
support,
amide-nitrosoamide type mechanism for SCR of NO
Vi02 (g)
+
Ce02
FTIR studies and the knowl¬
02(g)—>20 NH3 (g)
the
MnOx(0.3)-
(a)
+
(3)
(a)
(4) _>
N2 (g)
HN02 (a)
+
H20 (g)
(5) (6)
Selective
NH3 (a)
N2 (g)
—>
They
HN02 (a)
+
—>
Catalytic
NH4N02 (a)
—>
+
the
on
H20 (7)
sorption
and
perature
NOx reduction
can
be
in
catalyst with
a
considerable
reactants, we
known
to
the
the
a
applied pulse
relationship
how the
properties,
to
thermal
analysis
further this
Best
sorptive NOx
content
between
for sorp¬
of 25%.
about manganese-
behavior of
adsorption
catalytic
combined with
knowledge.
content was
tem¬
in SCR, there is still rela¬
behavior in SCR.
varied from 0
spectroscopy
mass
In order
composition of the manganese-cerium the manganese
of low
properties
gained
properties
redox behavior of the mixed oxide and
have
them for
of
interactions
development
manganese
has been
knowledge
concerning
and FTIR spectroscopy
insight
to use
oxidizing atmosphere.
cerium mixed oxides and their favorable
tively little
[10-14] studied the
oxides
broadly applied
an
found for
were
al.
adsorption
(< 150 °C). The combination of nitrogen oxide
low temperatures
catalysis
et
manganese-cerium
at
Although,
Machida
catalyst [7-9].
removal
tion of NOx
111
2H20 (g)
+
of nitrogen oxides with
these
NH2NO (a)
by NH3
concluded that the initial step of the SCR process is the
ammonia
Here
Reduction of NO
to
gain
some
mixed oxides affect to
100 at.%.
Experimental
6.2
The
MnOx-Ce02 catalysts
from aqueous solutions [6,7]. were
dissolved in
ratio of citric acid
mixture
was
water
to
stirred
110 °C for 12
were
prepared by
Manganese nitrate,
a
cerium nitrate and citric acid
and mixed in the desired
metal components
at room
standard citric acid method
proportions and the
(manganese
and
cerium)
was
temperature for 1 hour. The solution
hours, resulting
in
a
was
molar
1.0. The
dried
at
porous, foam-like solid. The foam-like pre-
Chapter 6
112
calcined in air
cursor was
oxides
face
the
the
determined
instrument. Before
The
catalysts
are
measurement
the
samples
as
rep¬
The BET
sur¬
Micromeritics ASAP 2010
were
of the mixed oxide
area
a
denoted
Mn(0.25)
composition (MnOn)025(CeO2)075.
by N2 adsorption using
150 °C The BET surface
m2
procedure.
same
represents the molar ratio of Mn/(Mn+Ce), e.g.
x
catalyst with
area was
of 20-30
the
prepared using
were
Mn(x), where resents
500 °C for 2 hours. The pure manganese and ceria
at
was
degassed found
g"1, while that of the pure MnOx and Ce02
to
were
in
vacuum
at
be in the range
3 and 15
m
g'1,
respectively. reduction-oxidation behavior and SCR
Adsorption, were
carried
device
enabling injection
of
certain
a
gaseous mixtures into the carrier gas amount
of injected gas
controlled mass
(ca.
flow
200
by
was
1.0
to a
generally
50
or
step of 0.01° and 0.3
were
passed through mass
to
carried
s
rate was
thermal
on a
by
a
heated (ca. 200 °C) amount
heated
leaving
capillary to
of the
a
catalyst
out on a
Siemens D5000
powder X-ray diffracto-
in step mode between 10 and 80° 20 with
a
step4.
500 °C
cooled down
change was
a
or
the system. The
connected
was
spectrometer. The
adsorption experiments
thermoanalyzer
mass
flowing through
pulse
different gases
Bruker Vector 22 FTIR spectrometer. Gases
using the Cu-IC^ radiation
they were
one or two
a
100 mg.
analysis was
Before the
with
ml, if not otherwise specified. The flow
Pfeiffer Omni Star GSD 301 O
meter
stream
of
sensing technique. The thermoanalyzer
°C) capillary
XRD
amount
flow controllers, Brook's model 5850E, based
mass
the FTIR spectrometer
was
measurements
thermoanalyzer equipped
Netzsch STA 449
out on a
activity
to
to remove
the
the
the gases adsorbed
measuring
detectable (cf.
catalyst samples
Ammonia
heated in the
during handling,
temperature and
chapter 5).
were
then
equilibrated until
no
(purity 99.98%, PanGas)
Selective
nitric oxide
and helium
(purity 99-98%, Messer)
(purity 99-999%, PanGas)
were
Reduction of NO
Catalytic
used
113
5% oxygen in helium
or
adsorptive
as
by NH3
and carrier gases, respec¬
tively. Redox-experiments 1
3 K min was
were
and each 50 °C
injected
followed
by
a
performed
one
pulse
under helium with
of 1.0 ml
reoxidarion
pulse
a
heating
rate
of
hydrogen (99-999%, PanGas)
of 1.0 ml oxygen
(99.999%,
Pan-
Gas). SCR
activity
50 ml min' After the
using
02,
due
to
method
adsorption
the
pulse
method
nitrogen
the
cerning
stream
and the formed
evolution
applied
suitability
their
injected
was
of the
N02,
during
tested
pulse
NO and
NH3
of
was
and
changed
until
H20
was
down
uptake
no mass
injected
were
monitored
monitored
experiment,
the
5% NO,
to
were
to
by
allowed
FTIR.
quanti¬
[15,16]. The reliability of the
reaction
by repetitive method for
cooling
pulses (1 ml)
N2, N20
rate
following procedure:
equilibrated
the end of each
at
total gas flow
the
(He)
recorded. Then ammonia
was
of nitrogen,
fying
was
to
a
500 °C and
the carrier gas flow
while the evolution of
pulses
at
at
out
according
balance helium, and the system
by MS,
more,
pulse
temperature)
into the carrier gas
The
the
carried
were
preparation period (calcination
desired reaction
5%
measurements
runs
on
each
discriminating
activity was confirmed by corresponding
tests
sample. the
using
Further¬
samples a
con¬
continuous
microreactor.
6.3 Results and Discussion
Analysis
of the structural and textural
mixed oxides
by X-ray
diffraction and
properties
of the
nitrogen adsorption
manganese-cerium corroborated that
114
Chapter 6
the structural and textural
similar
6.3.1 In
a
and
to
those
NH3
on
of the
reported by Machida et
Adsorption
first step
properties
we
samples
al. in their
used in this studies
were
original work [10,11].
Behavior
have
investigated
selected
samples.
the
As
of the
adsorption
an
reactant
gases
NO/02
6-1 shows the
example, Figure
mass
20
A
1 5
„, en c m
1-0
NOx adsorption
2U2>N
Xs^"^
-
1 27 mg
.c
o us
05
/
NHj adsorption 1
i
00 0
07mg
20 min
B
10xNO„ 1 5
-
I
N.°.
NO,
NOi
Nt|^
NH,
.:::!:::....::
E
.-.i. 00 9mg
1 0
1 28 mg
u
05
«
-
(0
E 00
20 min,
•
-0 5
time /
Fig.
6-1
:
Change
of the
mass
due
adsorption of NOx and NH3 on Mn(0.75) at 100 °C, ml min'1, volume of the pulses: 1.0 ml, carrier gas: 5%
to
catalyst mass: 100 mg, flow rate: 50 02/He. A: separate adsorption of one
changes
of the
mm
gas. B: consecutive
sample containing
75% Mn
adsorption
(Mn(0.75))
-
first
at
NOx,
100 °C
then
NH3.
resulting
Selective
from 5%
carrier gas. It illustrates the
02/He
irreversible
Strong, virtually
during the
first
further
no
mass
adsorbed
versibly
into
pulse technique.
of the
injected
gas
3 and 4 resulted in both
The
steady
at
detectable, represents the
were
corresponding
listed in Table 6-1.
gain
mass
mg of
NOx
with
of irre¬
and 0.07 mg of with different
content
of 25-75 at.%
Mn
a
amount
samples
results for all
Samples
state, i.e.
NH3 adsorption on various manganese-ceria mixed oxides. Up¬ (coverages) determined by pulse thermogravimetry; NO pulses in helium (©nq)' NO
Table 6-1
takes
changes
occurred. The
(chemisorbed) species (1.27
NH3, Figure 6-lA). content are
features of the
pulses, subsequent pulses
115
pulses, respectively,
adsorption (chemisorption)
adsorption (physisorption)
when
Mn
two
typical
by NH3
(reversible) adsorption, whereas during further pulses only
strong and weak
weak
Reduction of NO
of a series of ammonia and nitric oxide
injection
occurred
Catalytic
pulses
NO,
:
in 5%
(0nh3 c)
and
N02
02,
and
balance helium
(6N02),
and ammonia
pulses
in
helium, chemisorbed
physisorbed (0NH3 c+p).
6NO / plmol g
Sample
l
6N02 / \lmo\ g'1 0NH3
c
/
plmol g'1
ÖNH3c+p/ Jlmol g'1
Mn(0.00)
77
196
0
6
Mn(0.10)
160
422
6
55
Mn(0.25)
197
559
41
135
Mn(0.50)
167
483
41
118
Mn(0.75)
70
276
41
106
Mn(1.00)
7
22
0
21
showed
highest uptakes
for chemisorbed ammonia, whereas
physisorbed ammonia, NO, ing 25
at.% Mn.
adsorbed
Generally on
compared
pure oxides
and
to
NH3.
NO/02
were
the mixed oxides
Lowest
Mn203 (Mn(1.00))
and
highest
for the
uptakes sample
due
to
contain¬
considerably more NO/02 was measured for the
adsorption uptakes
were
Ce02 (Mn(0)).The
total ammonia
uptake
Chapter
116
6
(physisorbed
and chemisorbed, cf.
Mn
seemed
14
content
(0);
(0.10);
23
27
to
correlate
(0.25);
Particularly interesting ments
of the
clearly
indicate that
and that
reactant
are
gases
NO/02
coadsorption
has
curve
adsorption
of ammonia. The
tion of both gases
Figure
the
are
(0.75);
20
the results of
presented
in
and
are
NH3
6-IB
mass
same as
Figure
gains
in the
on
(sample):
the
uptakes of
when the gases
NOx
measure¬
measurements
different surface sites
at
adsorption
Note the values of 1.27 and 1.28 mg for
arately.
6-IB. These
that resulted from case
g'
m
(1.00).
adsorbed
the
areas:
subsequent adsorption
influence
depicts
3
with different
samples
their BET-surface
virtually no
gases. The
in
to
(0.50);
24
of the
Figure 6-12A)
of the
reactant
NOx followed by
subsequent adsorp¬ were
adsorbed sep¬
and 0.07 and 0.09 mg
for ammonia for separate and consecutive
adsorption, respectively (Figure
and B).
of ammonia
ferent
Figure
6-2
catalysts
at
100 °C The
determined after 20 min small
all
on
of the
to
amount
desorption
of
the
on
irreversibly
into the carrier gas stream, is
to
the
adsorption uptake
measurements
programmed desorption Figure 6-3A.
The
is shown in
tored
NOx adsorption indicate
FTIR after
100-400 °C is due
traces
to
of
amount
representative example
ammonia
over
the dif¬
adsorbed ammonia,
relatively
weakly, reversibly
manganese-ceria catalysts depends
in situ temperature
by
adsorption
on
the Mn
con¬
investigated samples.
Subsequent
jected
curves
On the other hand, the
catalysts.
adsorbed ammonia tent
the TG
depicts
6-1A
occurs
to
the evolution of
in the range 100-250
(Figure 6-3B).
Note that the
N20 during desorption.
the
measurements
as
major part
were
that the
confirmed
mass
The
sub¬
(TPD).
desorption profiles
nitrogen dioxide.
°C,
samples
A
moni¬
loss between
desorption
by monitoring
of
FTIR
of adsorbed ammonia is oxidized
Selective
Catalytic
Reduction of NO
by NH3
117
0.4
0.3-
E 0.25 / 0.23 mg
0)
0.50 / 0.20 mg 0.75/0.18 mg
iz
CO
tn
w co
E
T"
40
20
60
time / min
Fig.
Mn(0.75) 1.0
ml,
versibly are
of the
Change
6-2:
°C,
100
at
catalyst
carrier gas: He.
due
mass:
Manganese
indicated
on
the
100 mg, flow
mass
of
adsorption rate:
maximal
change due
NH3
uptake
mass
to
by
,
due
volume of the to
irreversibly
pulses: and
irreversibly adsorbed ammonia only
the
pulse technique
is very similar
breakthrough
al. [12] showed
by
curves
DRIFT
for
on
to
the
catalyst composition
that found
determining
by
the
Machida
studies, that the NOx uptake increased
increased, suggesting chemisorption via oxidation of NO. The fact that observed in the desorbed gas
Based
et
on
is adsorbed
et
NOx uptake.
lower temperature and when the oxygen concentration in the gas feed
of Machida
re-
curves.
al. [13] who measured et
Mn(0.25), Mn(0.50),
on
50 ml min"
dependence of NOx (NO/02) adsorption
determined
Machida
to
content,
adsorbed ammonia and the
The
at
mass
only the presence of N02
was
we
confirms the conclusion
al. [11]. FTIR studies
on
Yang and coworkers [5,6] proposed
manganese-cerium mixed
oxides
on
that ammonia
Lewis acid sites subse-
Chapter 6
118
T"1 T'"
f—I—I—I—I—i—i—|—i—i—i—i
100
150
200
|
I
I
I
A: FTIR
6-3:
Mn(0.50) NH3
He,
at
traces
N02
10 °C, carrier gas: 5%
recorded
heating-rate:
during TPD
10 K min"
quently transforming nism
recorded
after
400
TPD after
during
NH3 adsorption
i.e.
NO/02
measurements
by
clearly
the
to
on
10 K
NOx adsorption
min"1.
Mn(0.50)
B: FTIR
at
step 3 of the
exposure leads
to
desorption profiles
indicate that
interfere, supporting that these species
sites.
350
02/He, heating-rate:
NH2 according
which is corroborated
adsorption
traces
I—?—I—I—|—i—i—i—r
N20
on
and
100 °C, carrier gas:
.
into
(cf. Introduction),
(N02)
not
and NO
|
300
/ °C
temperature
Fig.
I
250
proposed
adsorbed nitrite shown in
Fig.
mecha¬
species
3A. Our
NO/02 and NH3 adsorption do
are
adsorbed
at
different surface
Selective
Catalytic
Reduction of NO
by NH3
119
6.3.2 Redox Behavior In order
alysts
to
check the
and their
temperature
by
reactivity in
reoxidation. As
pulses
cant
at
between redox
SCR their redox behavior
programmed reduction (TPR) reducing agents
The behavior of nia
possible dependence
ammonia and
due
to
Figure
pulses, only
ammonia
cat¬
investigated by both,
hydrogen
Mn(l.OO) and Mn(0.50) during
occurs
of the
and differential reduction followed
100 °C and 300 °C is shown in
reduction
was
properties
were
applied.
interaction with
6-4. At 100 °C a
small
no
ammo¬
signifi¬
adsorption uptake
1.0300 °C
100 °C 0.8. +
0.6-
E
0.4-
0.00 mg
Mn(1.00)K.
\
H
Mn(1.00)
0.2 O) c
03 JO
0.0Mn
u
w
E
(0.50)
+
-0.2
0.07 mg
7*
Mn
(0.50)
-0.4. -0.6
-0.8-1.0-
—r~
—|—
50
100
—,—
200
150
250
time / min
Fig.
6-4:
changes resulting from 1 °C, sample mass: 100 mg.
Mass
100 °C and 300
is observed. However,
at
300 °C
(0.72%) which corresponds
to
an
ml
NH3 pulses
over
Mn(0.50) shows extent
a
Mn(1.00) and Mn(0.50)
weight
of reduction of
ca.
at
loss of 0.72 mg
68%, assuming
Chapter 6
120
that
Mn203
Mn(0.50)
at
ammonia
by
the lattice oxygen. After
due
monitored, with to
of the
change at
maximum
due
mass
not
this temperature
to a
lead no
to
any
that reoxidized the reduced
mixed oxides,
sponding observed
mass
a
catalyst
in the
followed
the initial
by
mass
loss observed
was
in formation
resulting
to
oxygen
mass
mass
by
an
oxygen
physisorption)
and
pulses
at
this
corroborating
and tem¬
that
at
ammonia exposure. At 200 °C,
by desorption
and reduction, both
loss indicated the reduction of
mass was
in
regained after an
hydrogen
TG. Mn
mass
of the
hydrogen pulses
and evolution of N20
oxygen
pulse
to
content
575 °C
are
of the
in the
indicated
manganese-cerium and
catalysts on
the
corre¬
curves.
The
reduction increased with the manganese content, for
negligible
reducibility
NH3/He. Beyond
for Mn(0.50) followed
species. Further
TPR-profiles
during
a
sample.
monitored
loss
into the carrier
shown). Figure 6-5B shows the
not
adsorption (chemi-
change
losses recorded up
only
differential and 1 ml
as
mass
pure ceria
the lattice oxygen
NH3 pulse
was
catalyst by ammonia and
6-6 shows the
pulses
in 5%
250 °C. Further
The observed
occurring simultaneously.
Figure
Mn(0.50)
reduction occurred due
however, weak adsorption
pulses
by
of physisorbed ammonia
perature did
the
at ca.
150 °C, which resulted in
desorption
of
nitrogen (observed by MS,
and
and oxidation of
of the process.
profile
the oxidation of ammonia
water
pulse
a
oxygen
catalyst by ammonia started
150 °C, reduction of the
was
injecting
catalyst
with
NH3
(before the reduction step) could be regained after
mass
shows the TPR
Figure 6-5A ca.
strong reduction of the
pulses, indicating the reversibility
few
of
to
Thus the interaction of
Mn304.
to
300 °C leads
the initial
stream
gas
reduced
is
catalyst,
were
which reoxidized the
change
was
the
injected
observed. In order
experimental
strategy
each 50 °C followed
catalyst (Figure 6-7).
by
Below 200 °C
to
check the
was
changed
1 ml oxygen no
reduction
Reduction of NO
Catalytic
Selective
by NH3
121
temperature / *C 100
50
•
150
200
250
t
i
i
....
....
.
300
350
400
450
i
i
i
i
...
....
....
....
.
500 .
200 "C
E
0.1-
0.034 mo
time / min
Fig.
A: FTIR
6-5:
Mn(0.50), carrier
N20, H20 and NH3 recorded during heating of 50 mg NH3/He, 10 K min"1; 50-150 °C desorption of NH3(a), above
traces
gas: 5%
of
due to NH3 pulse on 100 mg Mn(0.50) Change of the followed by 02 pulse at 150 °C (only NH3 adsorption and desorption of physisorbed species) and 200 °C (NH3 adsorption, desorption and catalyst reduction followed by reoxidation by
150 °C: reduction
by NH3.
B:
mass
oxygen).
observed but with
was
increased the
significantly.
Mn(1.00) did
not
increasing In
temperature
contrast to
show the
mass
loss due
to
hydrogen pulses
the total reduction shown in
largest
mass
loss
at
Figure 6-6,
temperatures below 400 °C.
Thus different reduction behaviors emerge when total and differential reduc¬ tion
are
considered, which
is
important when relating
catalytic activity of the samples,
as
will be done in the
the redox behavior next
chapter.
to
the
Chapter 6
122
0-
0.00 / 0.24 mg
ÏÏ.1Ô ;o.4fa fflg0.25 / 0.86 mg -1
-
E 0.50/2.11 mg
-2-
œ en c
co ^ o
-3-
ID to
CO
E -4-
1.00/5.27mg
-5-
100
400
300
200
temperature
Fig.
6-6:
TPR of Mn(x)
the
catalyst
and
mass
catalysts
in 5%
loss from 50 mg
in He,
H2
sample
600
500
/ °C
heating rate:
is indicated
on
the
5 K
min"1,
Mn
content
in
curves.
E CD US
m as
CO
E
0.5 mg
I
200
150
'
250
'
—TT—i—|—i—i—r-
i
300
temperature
Fig.
6-7:
Redox-behavior ofMn(x)
composition. 3 K
1 ml
min"1, sample
catalysts
H2 pulses followed by
mass:
100 mg. Mn
content
400
350
as a
450
500
550
/ "C
function of the temperature and
1 ml
02 pulses
in the
catalysts
each 50 °C.
is indicated
on
catalyst
heating the
rate:
curves.
Selective
6.3.3
Catalytic Activity
In order
oxides
to
by means
stream
gas
investigate the
123
by NH3
in SCR SCR
activity of the various manganese-cerium mixed
pulse technique, NH3 pulses were injected into
of the
5% NO/5%
containing
02,
balance helium.
continuous system corroborated that the
criminating
Reduction of NO
Catalytic
pulse
the SCR activities of the different
Activity
method
was
tests
a
carrier
using
a
suitable for dis¬
manganese-cerium
mixed oxide
catalysts. The influence of the temperature ucts
to
of the SCR reaction and the
ammonia
the
pulses
experiment
Above 100 °C but
at
are
were
shown in
50 °C there
change Figure
used for the
only negligible was
a
the
on
of the
mass
6-8. The
quantitative
mass
distinct
composition
gain
of catalyst
two
N2-pulses
due
the reactions to
prod¬
Mn(0.25) due at
the end of
calibration of the FTIR
change during mass
of the gaseous
was
formation of
signal.
observed,
NH4N03.
ci
3
time / min
Change of the mass (TG) of Mn(0.25) and spectroscopic signals of N2 and N20 recorded during pulses of NH3 at different temperatures. Catalyst mass: 100 mg, flow rate 50 ml min"1, carrier gas: 5% NO, 5% 02 balance He. Fig.
6-8:
Chapter 6
124
Ammonium nitrate formation showed also
mixed oxide
composition, showing
deposited NH4NO3 (sample):
on
0.15
100 mg
a
maximum for
samples
due
mg
0.19
(1.00). The formation of NH4N03
results of the fresh Results of this
to
analysis
of the
catalyst
are
depicted
in
Figure
the Mn-Ce
on
Mn(0.75). The
amounts
confirmed
after reaction
1.62
(0.75);
by comparing at
the
50 °C with TA
aqueous solution of
6-9.
of
of 1 ml reactive gas
injections
was
catalyst impregnated by
analysis
dependence
(0); 0.45 (0.10); 0.34 (0.25); 0.96 (0.50);
were:
results of the thermal
clear
a
Decomposition
NH4N03.
of NH4N03
3 CO
£> (=
.£
8 c CO
e o
_o CO
350
temperature / °C
NH3, H20, NOx and N2 traces recorded during decomposi¬ tion of the deposited material on the catalyst (Mn(0.50)) after NH3 and NOx co-adsorption at 50 °C (thick lines) and during decomposition of the NH4N03 impregnated catalyst Fig.
Comparison
6-9:
of the
(Mn(0.50)).
shows that this salt is stable up
to
150-200 °C For the
with the aqueous solution of NH4N03 the evolution
H20
are
similar
as
those observed
catalyst impregnated of NOx,
N2 and
of the solid
deposit
profiles
during decomposition
Selective
formed
on
the
NOx profiles
catalyst
probe
model for temperature perature with
by NH3
lower temperatures. The small shift in the
at
explained by
the different
and reference
sample. According
could be
in the
NH4N03
Reduction of NO
Catalytic
programmed
increasing sample
mass
Table 6-2 lists the results of the
reactions
peaks
of
amount
are
to
shifted
a
to
125
N2 and
deposited
quantitative
higher
tem¬
[17].
comparative activity
tests
of the
catalysts
Catalytic Performance of Mn-Ce mixed oxides: N2 / N20 yield (%) at different temperatures. Catalyst mass: 100 mg, flow rate: 50 ml min" atmosphere: 5% NO, 5% 02
Table 6-2:
,
balance He.
100 °C
50 °C
Sample
200 °C
150 °C
250 °C
300 °C
Mn(0.00)
55/-
71/-
73/-
75/-
68/-
60/1
Mn(0.10)
59/-
85/-
88/-
89/-
87/1
76/7
Mn(0.25)
67/-
98/1
99/1
97/3
88/5
80/11
Mn(0.50)
65/-
91/2
95/5
93/7
87/13
75/23
Mn(0.75)
62/-
78/2
81/6
82/8
76/15
59/32
Mn(l.OO)
54/1
69/1
81/4
72/6
66/14
52/28
with different manganese ent
temperatures. The
cantly
with
increasing of
N20
content.
activity
manganese
is very low for pure
addition.
Selectivity
of nitrous oxide
were
differ¬
at
signifi¬
nitrogen decreases
with
to
nitrogen
was
°C, beside N2, only very small
dependence
of the
of the various Mn-Ce mixed oxides is shown
6-10. At all temperatures the best
selectivity
given
ceria, and increases
observed. The temperature
catalytic performance (N2-yield) Figure
to
are
reaction temperature and manganese content, whereas the formation
increases. At temperatures below 150
amounts
in
N2 and N20 yields (%)
Mn(0.25) and
catalyst concerning conversion the
highest N2-yield (99%)
and was
Chapter 6
126
Fig.
N2 yield
6-10:
function of the temperature and
as a
catalyst composition (marked
curves) obtained during pulsing of NH3, carrier gas: 5% NO, 5% 02 balance
found with this
catalyst
at
SCR-performance
150 °C The
lowing sequence: Mn(0.25)
>
Mn(0.50)
>
Mn(0.10)
>
on
He.
decreased in the fol¬
Mn(0.75)
>
Mn(0.00)
>
Mn(l.OO). In order over
these
gain
some
catalysts
sequence of
for
to
reactant
a
pulses
in oxygen
series of
pulses
catalyst Mn(0.50)
in
was
Figure
containing
further
phase
no
were
performed
6-11A. First the
were
catalyst
(5% 02/He) till
injected,
but
they
was
complete consumption
resulted
of the adsorbed ammonia
NOx pulses
be detected anymore and the
no
catalyst
mass
NO
to
in
was
NH3
injection
NOx
by
shown
by NOx
only
upon
significant nitrogen
are
exposed
saturation
the adsorbed ammonia reacted with the
tion occurred. After four
in which the
changed. Representative examples
nitrogen production was observed. However,
NOx pulses,
till
experiments
carrier gas
achieved, then NH3 pulses
adsorption,
into the mechanism of low-temperature SCR
insight
of
in the gas
the SCR
reac¬
formation could
(TG) reached the
same
value
as
Selective
Catalytic
Reduction of NO
by NH3
127
J3 CD
t T3 C
CD
1 'S
time /
Fig.
6-11
100 qC,
N2 production
:
catalyst mass:
due
to
pulses
100 mg, flow
rate:
mm
(NOx and NH3) over Mn(0.50) at min"1, carrier gas: 5% 02 balance He. A: cat¬
of reactive gas
50 ml
alyst was saturated first by NOx, then further NH3 pulses were injected and they resulted only in adsorption, no N2 production was observed, further NOx(g) pulses reacted with NH3(a) forming nitrogen (ER-mechanism) until NH3(a) is completely consumed. B: After saturation by NOx following pulses were injected: 1: 1 ml NH3 and 4 ml NOx simultaneously, N2 yield: 72% 2: 1 ml NH3, 3: 4 ml NOx, N2 yield: 37%, 4: 1 ml NH3, 5: 1 ml NH3 followed by 4 ml with
NOx
delay of 1
a
before ammonia with
min, N2
yield:
55%
that all adsorbed ammonia reacted
injection, corroborating
NOx.
To further elucidate the role of adsorbed ammonia in the SCR reaction,
several
NH3 pulses
oxidative
pulses
as
presented
of NOx
72%. The TG
were
curve
ammonia which was
removed in the
in
Figure
shows first
reacts
after
by
a
complete adsorption
6-1 IB. First,
distinct
mass
mass
loss due
with the gaseous
introduced
(pulse
No.
2)
preceding SCR reaction.
of NOx under
an excess
one
pulse
simultaneously injected resulting in
tion of both gases followed
ammonia
in the presence of
injected
atmosphere (5% 02/He),
and ammonia
four
were
to
gain the
a
to
NOx
of ammonia and
nitrogen yield
of
mainly physisorp¬
consumption of adsorbed
NOx species.
in order
As
due
a
of both,
an
to
Then
one
pulse
of
readsorb the ammonia
consequence the
mass
of the
cata-
Chapter 6
128
lyst
reached the
pulse
or
pulse (No.
phase does
in gas
3 in
but the
pulse
ammonia
adsorption. During
was
pulse
minute. This
ammonia
lower
by
ca.
was
the fifth
followed
by a
yield
was
still
a
the
in order
no
we can
conclude that
and lead
mixed oxides is
adsorbed ammonia
reacts
minor
importance
be attributed
with
that
to
investigations
presented
Eley-Rideal
with NOx from the gas
proposed by Yang and the
slow
HN02 (a) (step 7)
ments
an
in this
HN02 (a) can
not
study and
24%
originating
carried
on
out
NOx
coworkers is
applied.
formation
NOx (g).
in the
tem¬
in the gas
these observations
This
on
the
implies
that step
mainly contributing
type step 7
seems to
(step 6)
or
reaction of NH3 on
the
investigations.
to
be of
Whether this behavior has
be discriminated based
needs further
from
type mechanism, where
phase.
Langmuir-Hinshelwood
under the conditions
to too
to ca.
100—150 °C the dominant mechanism of SCR
at
N2 formation, whereas
physisorbed
of
simultaneous introduction of both
formation occurred. Based
manganese-cerium
5 of the mechanism
IB) injection
NOx delayed by
amount
desorption
of
equilibrium
adsorbed ammonia reacted with
series of analogous
significant nitrogen
1). Then the
6-1
of four ml
decrease of the to
Figure
indicated that in the absence of perature tange 100-150 °C
phase
significant
to
No.
reach
to
5 in
injection
due
(pulse
ammonia
higher compared
only irreversibly
and
injected leading
pulse (No.
during
obtained
In the third
NOx species.
half of that observed when the gaseous
physisorbed
resulted in
nitrogen yield than
experiment
was
(cf. Figure 6-2)
20%
No. 3, where
pulse
was
delay
gases. However, the
This
yield
NOx
repeated (pulse No.4)
ammonia
of an ammonia
with adsorbed
not react
reacted with chemi- and
NOx
observed, indicating that NH3 either
was
6-1 IB) 4 ml
Figure
nitrogen production,
one
before the SCR reaction. During the ammonia
as
nitrogen production
no
adsorbed
value
same
to
(a)
pulse experi¬
Catalytic Reduction
Selective
(a)
OH
N02 (a)
+
NH3 (a) ->
HN02 (a)
+
N2 (g)
+
interesting
It is
SCR is
an
—>
Yang [7]
and
zero
to
with respect
coverage of ammonia
NH3 species
et
+
at
120 °C
was
form
ER
through
a
react on
By
proceeds
an
NO
was
catalyst
of
reside
et
al.
[21]
tracer
tigation catalytic
of the
relationship
on
the main
between
behavior. The results in
and
Most of
V205
based
where
N02
studies
they
found that it is
with ammonia and
to react
et
al. [22]
aminooxy
with gaseous
suggested
reacts
species. They proposed or
groups
also
adsorption behavior, B and C
redox
two
different
are
involved. inves¬
properties
clearly
an
from the gas
objective of our study, namely the
Figure 6-12A,
to
reported a different mecha¬
species reacting
mechanism. Marban
SCR mechanisms, in which ammonium ions
Finally we come back to
that adsorbed
(Eley-Rideal mechanism)
the surface
with the surface active ammonia
pressure
surface in the presence of oxygen
isotopic
on
NO
to
proposed by Inomata et al. [19].
via adsorbed ammonia
Eley-Rideal
MnOx/Al203
Langmuir-Hinshelwood mechanism, the
of Qi
that the surface
investigated partial
in the over
imply
in the literature deal with SCR
mechanism
means
not
This would
mechanism, in which N02 (or the less reactive NO)
phase
study
(Langmuir-Hinshelwood mechanism).
reported
that NO does
that the SCR NO
phase
with both, gas
[20] proposed
nism of this reaction.
that the dominant mechanism of
for SCR
nitrogen and water, whereas Ozkan
possible
H20
reaction order of one with respect
virtually constant proposed
al. [18]
(ad) and NH3 (ad)
a
NH3, respectively.
to
can react
proposal
our
catalysts. An Eley-Rideal (ER) al.
+
type mechanism is in line with the kinetic
the mechanistic studies
et
NH2NO (a)
—>
(7)
reactive nitrite intermediates
Takagi
(6)
HN02 (a)
NH4N02 (a)
that
note
who found
Kijlstra
(a)
2H20 (g)
Eley-Rideal
and
range.
O
—>
129
by NH3
of NO
and
indicate that
Chapter 6
130
Fig.
6-12 :
Dependence of the amount of adsorbed N02 (NO puls¬ (NO pulses in He) and NH3 (NH3 pulses in He), chemi- and phys¬
A: Adsorption behavior:
02/He), NO isorbed or only chemisorbed, es
in 5%
catalyst composition, catalyst mass: 100 mg, flow rate: 50 ml min"1. B: Redox properties: Mass loss due to 1 ml H2 pulsed over 50 mg of function of catalyst as a function of temperature and catalyst composition. C: N2 yield as a the
catalyst composition
NO, 5% 02 balance He.
at
100 °C
on
the
and temperature obtained
during pulsing
of NH3, carrier gas: 5%
Selective
these
properties change strongly
cerium oxides and that there is
Catalytic
with the a
Reduction of NO
composition
by NH3
of the manganese-
correlation between
striking
131
adsorption
behavior, redox behavior and catalytic properties in SCR. Pulse thermal sis combined with
tool for
elucidating such
for all these
proved
spectroscopy and FTIR
mass
a
correlation because it
to
be
analy¬
very suitable
a
provides quantitative
measures
properties.
6.4 Conclusions
The selective reduction of NOx
catalysts
of different
combined with oxides Mn
content
their
on
to
composition, showing a
the
maximum for
Ce mixed oxide
proceeds
to
via
and the
catalytic
an
Eley-Rideal
an
Eley-Rideal mechanism,
with gaseous
adsorption
NOx
to
a
form
nitrogen
at
or a
100-150 °C
water.
of
similar
striking
cor¬
pulse
on
Mn-
Langmuir-Hin¬
where the adsorbed
and
a
behavior in SCR. The
mechanism
a
improved catalytic
discriminate whether the SCR reaction
shelwood mechanism. The studies indicate that via
of the mixed
samples with
composition of the mixed oxides, indicating
allowed
technique applied
reacts
activity
and NO, and of the redox behavior revealed
properties
analysis
thermal
the pure constituents oxides. Studies of the
relation between these
produced
using pulse
spectroscopy and FTIR. The SCR
NH3
reactants,
dependence
studied
of about 25 at.% Mn. All mixed oxides showed
activity compared both
manganese-cerium mixed oxides
over
composition has been
mass
depended on
by NH3
nitrogen
was
NH3 species
132
Chapter 6
6.5 References
Bosch,
F.
Janssen, Catal. Today
[1]
H.
[2]
V. I.
[3]
M.
[4]
K. Kawamura, A. Hirasawa, S.
(1988) 369.
2
Parvulescu, P. Grange, B. Delmon, Catal. Today 46 (1998) 233.
T.
Koebel, M. Elsener, M. Kleemann, Catal. Today 59 (2000) 335.
Higo,
R.
Aoki,
H.
5.
[5]
G.
R. T.
[6]
G. S.
[7]
G.
[8]
G. S.
[9]
G.
Qi,
[10]
M.
Machida, Catal. Lett. 5 (2002) 91.
[11]
M.
Qi,
Qi,
R. T.
R. T.
Qi,
Yang,
Chang, Appl.
Yang,
R.
217
Chang,
Yang, Appl. Catal.
Machida,
Catal. B 51 (2004) 93.
Yang, J. Phys. Chem.
Yang, J. Catal.
R. T.
R. T.
R.
M. Uto, D.
Chem. 13
Phys.
Ishikawa, K. Adachi, S. Hosoki, Rad.
(1979)
Qi,
Kimura, T Fujn, S. Mizutani,
B 108
(2004) 15738.
(2003) 434. Catal. Lett. 87 (2003) 67. B 44
Kurogi,
(2003) 217-
T.
Mater. Chem.
Kijima, J.
11
(2001) 900. [12]
M.
Machida, M. Uto, D. Kurogi, T. Kijima, Chem. Mater.
12
(2000)
3158.
(2000) 3165.
[13]
M.
Machida, D. Kurogi, T. Kijima, Chem. Mater.
[14]
M.
Machida, A. Yoshii, T. Kijima, Int. J. Inorg. Mater.
[15]
M.
Maciejewski, A. Baiker, Thermochim. Acta 295 (1997)
[16]
M.
Maciejewski,
C. A.
12
2
(2000) 413. 95.
Müller, R. Tschan, W. D. Emmerich, A. Baiker,
Thermochim. Acta 295 (1997) 167.
[17]
D. A. M. Monti, A.
[18]
W. S.
171
[19]
Kijlstra,
D. S.
Baiker, J. Catal. 83 (1983) 323. Brands, H. I. Smit,
E. K.
Poels,
A.
Bliek, J. Catal.
(1997)219.
M. Inomata, A.
Miyamoto,
Y.
Murakami, J. Catal. 62 (1980) 140.
Selective
[20]
M.
Takagi,
Catalytic
Reduction of NO
by NH3
T. Kawai, M. Soma, T. Onishi, K. Tamaru,
133
J. Catal.
(1977)441. [21]
U. S.
[22]
G.
Ozkan,
Y. P.
Cai, M. W. Kumthekar, J. Catal. 149 (1994) 390.
Marban, T. Valdes-Solis, A.
B.
Fuertes, J. Catal. 226 (2004) 138.
50
Seite Leer / Blank leaf
Final Remarks
The present
mal
analysis by
careful
the
FTIR is
strongly
analysis
is
gas
pulse technique using
optimization
only
by
Among
accurate
possibilities
the various
advantage
evolved or
sess
similar
severely
fragmentation
affect the
showed that
a
use
ions
of MS
Micro GC
packed columns,
strategy may be suitable four columns in
or
using
parallel,
identification of the evolved
resolu¬
spectral
poor time
reso¬
analysis
chromatography (GC).
The
the gases
identify
reactions, which is difficult when using
FTIR for
released
may pos¬
vibrational spectra which
extremely
efficiency every
provides
during TA,
quantification. Preliminary
short and
analysis
which
be considered in
to
separate and
one can
overlapping
increases the to run
gas
simultaneously or
to
of combining TA with evolved gas
parallel
FTIR. Gases and vapors,
MS
micro
or
on
quantification.
of this method is that
during multistage
factors
resolution leads
(EGA), another promising method would be great
based
parameters, whereas MS
the choice of the
are:
High spectral
rate.
lution, which is crucial for
important
of TA-FTIR
means
tion and carrier gas flow
most
requires
FTIR spectroscopy
or
experimental
the chosen
little affected. The
quantification by
MS
ther¬
during
experimental settings. Quantification
of the
affected
of evolved gases
quantification
showed that the
study
of the
two
the
species. However,
narrow
minutes with
opportunity a
limitation
for
results
capillaries
separation
can
and
process. This
two or
optional
separation
compared
to
and
FTIR
136
or
MS systems is that: the
method is less tems,
accurate
quantification
because of the
of the evolved gases with the
relatively poor time
which is discussed for FTIR and MS methods in
The extension of the present system
provide
further
where neither MS
resolution in GC sys¬
chapter
4.
TA-MS-FTIR-GC system would
analytical possibilities particular
adsorption phenomena, cal tool.
to a
pulse
nor
for
gas-solid
FTIR is the
reactions and
appropriate analyti¬
Seite Leer / Blank leaf
Seite Leer / Blank leaf
List of Publications
List of
The on
publications
related to the thesis
following list summarizes chronologically
pertinent chapters of the thesis
this thesis. The
Calibration of
"Quantitative
the
publications which are are
Spectroscopic Signals
given
based
in brackets.
in Combined TG-FTIR
System" F.
M.
Eigenmann,
Maciejewski,
A.
Baiker, Thermochim. Acta (in press)
(Chapter 3)
"Influence of
Signals F.
Measuring
in TA-FTIR-MS
Eigenmann,
M.
Conditions
on
the
Quantification
of
Spectroscopic
System"
Maciejewski,
A.
Baiker, J. Therm. Anal. Cal. (in press)
(Chapter 4)
"Gas F.
Adsorption
Eigenmann,
(Chapter 5)
Studied
M.
by
Pulse Thermal
Maciejewski, A. Baiker,
Analysis"
Thermochim. Acta 359 (2000) 131.
140
"Selective Reduction of NO
Relation between F.
Eigenmann,
by NH3
adsorption,
M.
over
redox and
Maciejewski,
A.
Manganese-Cerium
catalytic
Baiker,
Appl.
Mixed Oxides:
behavior"
Catal. B 62 (2005) 311.
(Chapter 6)
publications
List of other
Following publication research
G.
published during
the thesis but
covers
another
topic.
"Continuous Pt/TS-1
was
Epoxidation
of
Propylene
with
Oxygen
and
Hydrogen
on a
Pd-
Catalyst"
Jenzer,
T.
Gen. 5304
Mallat, M. Maciejewski, F. Eigenmann, A. Baiker,
(2000)
Appl.
Catal. A-
1.
Patents
"Process for the Production of Molybdenum Oxide,
Molybdenum
Oxide pro¬
duced from this Process and Use thereof" R.
Nesper,
Eur. Patent
F.
Krumeich,
Appl.
M.
Niederberger,
No. 01810072.7, 2001
Technology (ETH),
Zürich
(Switzerland)
A.
Baiker, F. Eigenmann
Applicant:
Swiss Federal Institute of
141
List of Conference Contributions
"Pulsthermoanalyse:
pling Days (2nd F.
Eigenmann,
proceedings,
Neue
SKT
M.
oral
1999) from
Maciejewski,
F.
M.
poster and oral
Maciejewski,
proceedings,
F.
M.
oral
Adsorption
Chemical
1999 in Selb
(Germany),
A. Baiker,
FTIR
a
workshop.
Signalen", Analytica,
28-31
Maciejewski,
presentation
Studied
Society 2000,
Eigenmann,
A.
13
April
2000 in
Baiker,
of Spectroscopic FTIR
2000) from
SKT
Eigenmann,
"Gas
April
presentation.
"Quantitative Calibration
F.
von
für STA-FTIR", 2nd Selber Cou¬
(Germany),
Eigenmann,
Days (3rd
18-22
presentation and leading
"Quantitative Kalibrierung München
Möglichkeiten
M.
A.
and
May
Signals", 3rd
2000 in Bad Orb
Coupling
(Germany),
Baiker,
leading a workshop.
by Pulse Thermal Analysis",
Fall
Meeting
of the Swiss
(Switzerland),
Lausanne
Maciejewski,
Selber
A.
Baiker,
poster.
"Methanol Oxidation Studied Swiss Chemical F.
Eigenmann,
poster.
by
Pulse Thermal
Analysis",
Society 2001, Zürich (Switzerland),
M.
Maciejewski,
A.
Baiker,
Fall
Meeting
of the
Curriculum Vitae
Name
Florian
Date of Birth
5
City
of Birth
July
Eigenmann
1973
Zürich
Citizen of
Waldkirch (SG)
Nationality
Swiss
Education
1986-1992
Kantonsschule Zürich-Wiedikon
Graduation with Matura
1993-1998
ETH
B
Zürich, Chemistry Department
Chemical
Engineering Studies
Graduation
1999-2005
Type
as
Dipl.
Chem.
Ing.
ETH
ETH Zürich, Institute for Chemical and Doctoral Thesis under the
Supervision
Bioengineering
of Prof. Dr. A. Baiker