Evolved gas analysis of coal-derived pyrite/marcasite

The products evolved during the thermal decomposition of the coal-derived pyrite/marcasite were studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR–MS) technique. The main gases and volatile products released during the thermal decomposition of the coal-derived pyrite/marcasite are water (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved product H₂O is mainly released at below 300 °C; (2) under the temperature of 450–650 °C, the main evolved products are SO₂ and small amount of CO₂. It is worth mentioning that SO₃ was not observed as a product as no peak was observed in the m/z = 80 curve. The chemical substance SO₂ is present as the main gaseous product in the thermal decomposition for the sample. The coal-derived pyrite/marcasite is different from mineral pyrite in thermal decomposition temperature. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanations have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials.     

Soft ionisation analysis of evolved gas for oxidative decomposition of an epoxy resin/carbon fibre composite

Soft ionisation mass spectrometry was used to investigate the oxidative decomposition of an epoxy resin/carbon fibre composite using thermogravimetry (TG) coupled with mass spectrometry (MS). Through comparison between decomposition in air and in argon, it was recognized that the first step of the oxidative decomposition of the epoxy resins was similar to the decomposition in argon. During the devolatilisation process, the oxidative decomposition underwent a thermal decomposition leading to the formation of a large amount of volatile products which were subsequently oxidized into water and carbon dioxide. The gas produced in the thermal decomposition was not oxidized completely leaving some organic volatiles in the emissions. Using soft ionisation, the components of the evolved gases were identified by mass spectrometry.     

Analysis of a Complex Gaseous Mixture by TG-MS and TG-FTIR

The thermal decomposition of sodium ethyl xanthate (SEX) was used to compare the techniques of pyrolysis-gas chromatography-mass spectrometry (py-GC-MS), thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and TG-MS. In the py-GC-MS analysis, SEX was pyrolysed at 400°C in an inert atmosphere. Major gases evolved were carbon disulfide, diethyl sulfide, ethanol, and carbonyl sulfide. The TG of SEX exhibited a sharp mass loss at 201°C (42.3%) and a gradual mass loss at 217-325°C (20.8 %). The MS spectra of the evolved gases were complex due to overlapping of molecular, isotope, and fragment ion signals. Using the MS in selected ion monitoring mode, the major gases evolved were found to be carbon disulfide and carbonyl sulfide. The FTIR spectra of the evolved gases displayed vibrational frequencies due to alkanes, carbonyls, carbonyl sulfide, and carbon disulfide. From the analyses it was concluded that py-GC-MS provided unambiguous gas identification. Interpretation of the MS results was reliant on the py-GC-MS results, and the FTIR data was limited to identifying gases with very characteristic vibration frequencies. This revised version was published online in July 2006 with corrections to the Cover Date.     

TG-DTA/FT-IR method for analyzing thermal decomposition mechanism of polyesters

An attempt to estimate the thermal decomposition mechanism of polymers using the simultaneous TG-DTA/FT-IR system was summarized. The library search of FT-IR spectra at various temperatures and of the subtraction spectrum obtained by subtracting the spectra at different temperatures were used to determine the types of evolved gases from poly(ethylene terephthalate) and poly(butylene terephthalate) at given stages of decomposition. The quantitative analysis of evolved gases was carried out using the specific gas profiles at the specific absorption band. The kinetic parameters were estimated from both TG and spectroscopic curves measured at various heating rates.     

Pyrolysis mechanism of urazole by evolved gas analysis

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

热分析-质谱联用中逸出气体的脉冲热分析定量方法

利用脉冲热分析技术(PulseTA)实现对热分析-质谱(TA-MS)联用系统中逸出气体质谱信号的定量,考察了多种实验参数如不同载气流速、温度以及分析样品量等因素对热分析-质谱联用系统中逸出气体质谱信号定量校正的影响.实验结果表明,利用PulseTA对TA-MS联用系统中逸出气体CO2定量结果与理论计算值的相对误差约2.85%.同时利用TG-DTG-MS联用技术对氮化铟(InN)粉体的热分解行为进行研究,在氩气气氛下InN粉体的热分解过程一步完成,InN粉体在550～750℃得到相应的正离子质谱峰:N2+(m/z=28),所释放的N非常接近InN中N的理论含量.利用PulseTA技术检测到InN粉体受热分解放出氮气质量的实验测量值与理论计算值的相对误差约为1.36%.     

Thermal studies of cobalt,iron and tin metalloporphyrins

A free-base tetraphenyl porphyrin (TPP) and its corresponding metalloporphyrins (MTPP) where M = Co, Fe and Sn were synthesized and characterized by UV–visible spectroscopy, FTIR and ¹Hnmr spectroscopy. Thermal studies of these porphyrins were carried out in synthetic air from room temperature to 800 °C using thermal analyser. The residues of MTPP after thermal treatment were qualitatively analysed, which showed the presence of corresponding metal oxides. Further, the above MTPP were subjected to thermogravimetry–evolved gas and mass spectrometry (TG–EGA–MS) analysis for the detailed information about evolved gases at their corresponding decomposition temperatures. This information may be used to predict the probable mechanism for ring opening of the macromolecular porphyrins.     

Thermal behavior and evolved gases analysis of 1,2,4-triazole-3-one derivatives

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

Application of simultaneous thermal analysis mass spectrometry and stable carbon isotope analysis in a carbon sequestration study

The simultaneous analysis of evolved gases and the determination of stable isotope composition (delta13C) as part of a thermal analysis experiment have been used to (a) distinguish bulk chemical hosts for carbon (C) and nitrogen (N) within a soil and (b) track labelled C within a soil sequestration experiment. C3 and C4 dung was applied to a pasture soil, and soil samples taken for analysis. The results of thermogravimetry-differential scanning calorimetry-quadrupole mass spectrometry-isotope ratio mass spectrometry (TG-DSC-QMS-IRMS) show that the proportion of more refractory C (lignin-like) is greater for the dungs than for the soil organic matter (SOM), and that this increases with time within the soil. Analysis of evolved gases shows that nitrogen is associated with the decomposition of more refractory C, and is not so strongly associated with the labile C component. IRMS analysis distinguished C3 and C4 dung, and allowed the amount of C from these sources to be estimated for the soil samples. Most dung C enters the refractory SOM fraction. This paper demonstrates the potential of TG-DSC-QMS-IRMS in the investigation of SOM.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Influences of evolved gases on the thermal decomposition of zinc carbonate hydroxide evaluated by controlled rate evolved gas analysis coupled With TG

The influences of atmospheric CO₂ and H₂O on the kinetics of the thermal decomposition of zinc carbonate hydroxide, Zn₅(CO₃)₂(OH)₆, were investigated by means of controlled rate evolved gas analysis (CREGA) coupled with TG. Although CO₂ and H₂O were evolved simultaneously in a single mass-loss step of the thermal decomposition, different effects of those evolved gases on the kinetic rate behavior were observed. No distinguished effect of atmospheric CO₂ was detected within the possible range of self-generated CO₂ concentration. On the other hand, apparent acceleration effect by the increase in the concentration of atmospheric H₂O was observed as the reduction of reaction temperature during the course of constant rate thermal decomposition. The catalytic effect was characterized by the decrease in the apparent activation energy for the established reaction with increasing the concentration of atmospheric H₂O, accompanied by the partially compensating decrease in the pre-exponential factor.     

Evolved Gas Analysis of Some Solid Fuels by TG-FTIR

FTIR spectrometry combined with TG provides information regarding mass changes in a sample and permits qualitative identification of the gases evolved during thermal degradation. Various fuels were studied: coal, peat, wood chips, bark, reed canary grass and municipal solid waste. The gases evolved in a TG analyser were transferred to the FTIR via a heated teflon line. The spectra and thermoanalytical curves indicated that the major gases evolved were carbon dioxide and water, while there were many minor gases, e.g. carbon monoxide, methane, ethane, methanol, ethanol, formic acid, acetic acid and formaldehyde. Separate evolved gas spectra also revealed the release of ammonia from biomasses and peat. Sulphur dioxide and nitric oxide were found in some cases. The evolution of the minor gases and water parallelled the first step in the TG curve. Solid fuels dried at 100°C mainly lost water and a little ammonia. This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigation of polymers by a novel analytical approach for evolved gas analysis in thermogravimetry

A newly developed measurement technique for evolved gas analysis in thermogravimetry, viz. a thermo balance coupled to comprehensive gas chromatography/single photon ionization mass spectrometry (TG–GC × SPIMS), has been applied to investigate the thermal degradation of two polymers (polycarbonate (PC) blended with ABS and PVC). This detection method provides a two-dimensional analysis of the evolved gaseous products. TG relevant data is obtained as well as an improved resolution power to separate isobaric molecular structures without losing any fraction of the samples. In addition, this solution is not associated with any extension of the measurement time. The assignment of the substance pattern to distinct species is improved compared to solely using MS without a preceding separation step. Furthermore, hitherto undetected compounds when compared to applying TG–SPIMS without GC such as benzonitrile and its methylated derivatives have been found in the evolved gases from the thermal degradation of PC/ABS blend. Finally, a first estimation of the limit of detection has been carried out, yielding 400 ppt for styrene and 500 ppt for toluene from the thermal decomposition of PC/ABS blend.     

Thermal decomposition of copper(II) and zinc carbonate hydroxides by means of TG-MS

Summary For the quantitative analyses of evolved CO₂and H₂O during the thermal decomposition of solids, calibration curves, i.e. the amounts of evolved gases vs. the corresponding peak areas of mass chromatograms measured by TG-MS, were plotted as referenced by the reaction stoichiometry of the thermal decomposition of sodium hydrogencarbonate NaHCO₃. The accuracy and reliability of the quantitative analyses of the evolved CO₂and H₂O based on the calibration curves were evaluated by applying the calibration curves to the mass chromatograms for the thermal decompositions of copper(II) and zinc carbonate hydroxides. It was indicated from the observed ratio of evolved CO₂and H₂O that the compositions of copper(II) and zinc carbonate hydroxides examined in this study correspond to mineral malachite, Cu₂CO₃(OH)₂, and hydrozincate, Zn₅(CO₃)₂(OH)₆, respectively. Reliability of the present analytical procedure was confirmed by the fairly good agreement of the mass fraction of the evolved gases calculated from the analytical values with the total mass-loss during the thermal decompositions measured by TG.     

Study on thermal decomposition of polymers by evolved gas analysis using photoionization mass spectrometry (EGA-PIMS)

Photoionization mass spectrometry (PIMS) with vacuum ultraviolet (VUV) light source provides an efficient and fragmentation-free method for the soft ionization of gaseous compounds, in order to facilitate an understanding of thermal decomposition behavior and chemical composition of polymeric materials. The PIMS was applied to the evolved gas analysis (EGA) system equipped with a skimmer interface which is constituted based upon a jet separator principle between a vacuum MS chamber and an atmospheric sample chamber in a furnace. A photoionization source with a deuterium (D₂) lamp was closely installed to the vacuum ionization chamber of a mass spectrometer to improve the ionization efficiency. The thermal decomposition of typical polymers in inert gas atmosphere was investigated by the EGA-PIMS and the resulting PI mass spectrum was characterized satisfactorily by only the parent ions with no contribution as a result of fragmentation during the ionization. The results suggested that the EGA-PIMS was an especially powerful and desirable in situ thermal analysis method for polymeric materials which evolve organic gases simultaneously and concurrently. The combination of EGA equipped with skimmer interface with no change of evolved gaseous species and PIMS with fragmentation-free during the ionization is described briefly, and the effective results are presented by comparing with EGA using conventional electron impact ionization mass spectrometry.     

Thermal analysis/evolved gas analysis using single photon ionization

A simultaneous thermogravimetry/differential scanning calorimetry device (STA) was coupled to single photon ionization time of flight mass spectrometry (SPI-TOFMS) for evolved gas analysis (EGA). Thermal resolution with thermogravimetric signals (TG/DTG) is delivered by STA. On-line coupled EGA with SPI-TOFMS retains the thermal information from the STA and substantiates these with correlating mass spectra. The application of vacuum ultraviolet (VUV)-photons (8–12 eV) for soft ionization, allows almost fragment-free ionization. Thus, it becomes possible to interpret mass spectra of complex matrices, like natural products evolving simultaneously several molecules, without an additional separation step. The STA–SPI-TOFMS on-line coupling offers the possibility to track subset mass traces during one STA run. Focusing on material-depended mass traces, differentiation of organic matrices is obvious. In this work two types of research cigarettes, 3R4F and CM6 were used. While the 3R4F cigarette is composed of a blend of different tobacco sorts and different curing methods, the CM6 research cigarette consists of pure flue cured tobacco. The advantages of coupling on-line chemical analysis methods to thermal analysis (TA) are in the context of the achieved thermo-molecular signatures.     

Effects of melamine phosphate on the thermal decomposition and combustion behavior of reconstituted tobacco sheet

In this paper, first the MP-modified reconstituted tobacco sheet (RTS) was prepared by a paper-making process. Thermogravimetric analysis coupled to Fourier transform infrared spectrometer (TG-FTIR) had been used to investigate the influences of melamine phosphate (MP) on the thermal decomposition and the formation of evolved volatile products of RTS. TG-FTIR results illustrated that the incorporation of MP into RTS could retard the thermal decomposition of the major components of RTS and meanwhile lead to the formation of more thermally stable char. Moreover, the main gases released during the pyrolysis of RTS and MP-modified RTS were H₂O, CO₂, CO, NH₃, carbonyl compounds, alcohols, phenols, alkanes, and alkenes. The presence of MP changed the formation of evolved volatile products of RTS obviously. The effects of MP on the combustion behavior of RTS were studied by micro-scale combustion calorimetry and cone calorimetry. Results demonstrated that the formation of combustible gases was mainly determined by the thermal decomposition stage occurred in the temperature range of 150–600 °C. The incorporation of MP into RTS influenced the release of fuel gases and the char formation in the process of the thermal decomposition of RTS, and eventually retarded the flammability and combustibility of RTS.     

Study on thermal degradation of cattlehide collagen fibers by simultaneous TG–MS–FTIR

Leather was useful materials since dawn of human history for excellent properties, but thermal degradation mechanism was not very clear yet. In this paper, much progress has been made in elucidating the thermal stability and thermal degradation mechanism by thermoanalytical study in argon. Thermogravimetric analysis simultaneously coupled with mass spectrometry and Fourier transform infrared spectrometry was employed to study the thermal degradation of cattlehide collagen fibers through in-depth analysis of the evolved gas. Thermogravimetry analyses carried out on sample, deprived from any residual catalyst and highlighted a two-step thermal degradation. New evidence demonstrates that the process during temperature range from 373 to 513 K was phase transformation. Photographs of polarizing microscope confirmed the conclusion. The decomposition of cattlehide collagen fibers starts at about 523 K. The cattlehide collagen fibers may undergo the process of melting, oxidation and decomposition. In decomposition, more than three steps take place. The mass spectra and Fourier transform infrared spectrometry stated clearly that double bond of carbon to oxygen, carbon to sulfur and carbon to nitrogen were destroyed firstly because the carbon dioxide, carbon monoxide and ammonia evolved simultaneously. The second peak of carbon monoxide in mass spectra indicated that some organic fragments were decomposed above 1073 K which confirmed that thermal degradation of leather is more than three steps.     

Thermal decomposition mechanisms common to polyurethane,epoxy, poly(diallyl phthalate), polycarbonate and poly(phenylene sulfide)

Thermal decomposition of polyurethane, epoxy, poly(diallyl phthalate), polycarbonate, and poly(phenylene sulfide) was examined using a combination of thermal and chemical analysis techniques. Thermal gravimetric analysis with simultaneous analysis of evolved gases by Fourier transform infrared spectroscopy, differential scanning calorimetry, and gas chromatography coupled with Fourier transform infrared spectroscopy were used to obtain rate data, determine enthalpy changes, and identify decomposition products. Examination of the evolved decomposition products indicated a common set of chain scission mechanisms involving the aromatic moieties in each of the polymer materials studied.     

Melting behaviour and evolved gas analysis of xylose

Two enantiomeric forms of xylose were identified as α-D-xylopyranose and α-L-xylopyranose by powder diffraction. Their melting behaviour was studied with conventional DSC and StepScan DSC method, the decomposition was studied with TG and evolved gases were analyzed with combined TG-FTIR technique. The measurements were performed at different heating rates. The decomposition of xylose samples took place in four steps and the main evolved gases were H₂O, CO₂ and furans. The initial temperature of TG measurements and the onset and peak temperatures of DSC measurements were moved to higher temperatures as heating rates were increased. The decomposition of L-xylose started at slightly higher temperatures than that of D-xylose and L-xylose melted at higher temperatures than D-xylose. The differences were more obvious at low heating rates. There were also differences in the melting temperatures among different samples of the same sugar. The StepScan measurements showed that the kinetic part of melting was considerable. The melting of xylose was anomalous because, besides the melting, also partial thermal decomposition and mutarotation occurred. The melting points are affected by both the method of determination and the origin and quality of samples. Melting point analysis with a standardized method appears to be a good measure of the quality of crystalline xylose. However, the melting point alone cannot be used for the identification of xylose samples in all cases.