Authors:J. Gutiérrez-Ortiz, Beatriz de Rivas, R. López-Fonseca, and J. González-Velasco
The catalytic behaviour of ceria, zirconia
and ceria–zirconia mixed oxides in the temperature-programmed degradation
of toluene and n-hexane was analysed by
means of evolved gas analysis (mass spectrometry). Pure cerium oxide resulted
the most active catalyst in the oxidation of both compounds. This fact revealed
the crucial role of the surface oxygen species in the decomposition of this
type of hydrocarbons. The low affinity of CeO2 for
H2O and CO2, the major oxidation
products, may be also responsible for the observed highly active catalytic
Authors:Mohammad R. Saraji-Bozorgzad, Thorsten Streibel, Markus Eschner, Thomas M. Groeger, Robert Geissler, Erwin Kaisersberger, Thomas Denner, and Ralf Zimmermann
thermophysical parameters as well as to observe chemical reactions. For more thorough and detailed investigations of the sample composition, a chemical investigation of the evolved gases, i.e., evolvedgasanalysis (EGA), is indispensable [ 1 ]. Depending on the
Authors:A. J. Parsons, S. D. J. Inglethorpe, D. J. Morgan, and A. C. Dunham
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.
The association of anomalously high levels of ammonium with both metallic and energy mineral deposits is of potential use
in mineral exploration. Conventional geochemical methods for detecting NH4 often provide only whole-rock NH4 values and do not identify the specific minerals hosting NH4. They may also lack sensitivity or be prone to interference. Evolved NH3 analysis is shown to be capable of distinguishing between different NH4-bearing minerals and can detect NH4 values down to 120 ppm in rocks hosting silver-gold vein mineralization. Fully quantitative determination of NH4 by this method is not possible as the NH3 evolved from minerals during heating partially oxidised; however, amounts of evolved NH3 do show a moderate positive linear correlation with NH4 content determined by a modified Kjeldahl method.
Authors:D. Price, M. Reading, R. Smith, H. Pollock, and A. Hammiche
Micro-thermal analysis employs a scanning probe microscope fitted with a miniature resistive heater/thermometer to obtain
images of the surface of materials and then perform localised thermo analytical measurements. We have demonstrated that it
is possible to use the same configuration to pyrolyse selected areas of the specimen by rapidly heating the probe to 600–800°C.
This generates a plume of evolved gases which can be trapped using a sampling tube containing a suitable sorbent placed close
to the heated tip. Thermal desorption-gas chromatogaphy/mass spectrometry can then be used to separate and identify the evolved
gases. This capability extends the normal visualisation and characterisation by micro-thermal analysis to include the possibility
of localised chemical analysis of the sample (or a domain, feature or contaminant). The isolation and identification of natural
products from a plant leaf are given as an example to illustrate this approach. Preliminary results from direct sampling of
pyrolysis products by mass spectrometry are also presented.
Thermal analysis combined with evolved gas analysis has been used for some time. Thermogravimetry (TG) coupled with Fourier
transform infrared (FTIR) spectroscopy(TG/FTIR), Thermogravimetry (TG) coupled with mass spectrometry (TG/MS), and Thermogravimetry
(TG) coupled with GC/MS offers structural identification of compounds evolving during thermal processes. These evolved gas
analysis (EGA) techniques allow to evaluate the chemical pathway of the degradation reaction by determining the decomposition
products. In this paper the TG/FTIR, TG/MS, and Pyrolysis/GC-MS systems will be described and their applications in the study
of several materials will be discussed, including the analysis of the degradation mechanisms of organically modified clays,
polymers, and coal blends.
In order to obtain a better understanding of the pyrolysis mechanism of urazole, molecular orbital (MO) calculations and evolved
gas analysis were carried out. The MO calculations were performed using the density functional method (B3LYP) at the 6-311++G(d,p)
levels by Gaussian 03. The geometrical structure of urazole and its tautomers were examined theoretically. Identification
and real-time analysis of the gases evolved from urazole were carried out with thermogravimetry-infrared spectroscopy (TG-IR)
and thermogravimetry-mass spectrometry (TG-MS). The evolved gases were identified as HNCO, N2, NH3, CO2, and N2O at 400 °C, but were different at other temperatures.
For complex decomposition reactions, traditional methods, such as TG and DSC cannot fully resolve all of the steps in the
reaction. Evolved gas analysis (EGA) offers another tool to provide more information about the decomposition mechanism. The
decomposition of sodium bicarbonate was studied by TG, DSC and EGA using a simultaneous thermal analysis unit coupled to a
FTIR. The decomposition of sodium bicarbonate involves two reaction products H2O and CO2, which are not evident from either TG or DSC measurements alone. A comparison of the reaction kinetics from TG, DTG and EGA
data were compared.
A recently-developed quadrupole mass spectrometer system specifically designed for thermal analysis studies, has been linked
to a thermobalance and a simultaneous TG-DTA unit, for evolved gas analysis. The performance and applicability of the system
is illustrated by examples from four fields of study