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 400C 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 201C (42.3%) and a gradual mass loss
at 217-325C (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
small flow rates through the TG instrument in order to increase the gas exchange rates and to prevent peak broadening.
In the present article, we report about the development and test of a TG-FTIR system for the thermal analysis of substances
Authors:F. Barontini, K. Marsanich, and V. Cozzani
The TG-FTIR technique was used in the present study to investigate the thermal degradation behaviour of materials containing
brominated flame retardants under fire conditions. Time-temperature profiles and oxygen concentrations typical of selected
fire scenarios were reproduced in the thermogravimetric analyzer, while the characterization of the gaseous products generated
was performed by the simultaneous FTIR analysis. FTIR analysis combined with the use of specific calibration procedures allowed
the quantitative estimation of the gaseous products evolved as a function of experimental conditions. The results obtained
allowed the straightforward assessment and the comparison of the quantities of hydrogen bromide formed in the oxidation and
thermal degradation of pure brominated flame retardants and of flame retarded materials of industrial interest. Hydrogen bromide
yields resulted dependent on the experimental conditions used, such as oxygen concentration and heating rate. Although TG-FTIR
experiments only provide a representation of the actual heterogeneous combustion products in real fire conditions, the coupled
TG-FTIR technique proved to be a straightforward experimental methodology allowing one to obtain reference data on the nature
and quantities of the macropollutants generated in a fire.
Authors:Yu-Chuan Chou, Tung-Feng Hsieh, Yu-Chen Hsieh, Chun-Ping Lin, and Chi-Min Shu
Multi-walled carbon nanotubes (MWCNTs) have remarkable properties. However, their thermal stability characteristics, which
may represent potential hazards during the production or utilization stage, concern unsafe or unknown properties researches.
Our aim was to analyze the thermokinetic parameters of different heating rates by differential scanning calorimetry (DSC)
and thermogravimetric analyzer (TG), and then to compare thermal decomposition energy parameters under various conditions
by well-known kinetic equations. MWCNTs were acidified via nitric acid (HNO3) in various concentrations from 3 to 15 N and were characterized by means of Fourier transform infrared (FTIR) spectrometry.
For original and modified MWCNTs, we further identified the thermal degradation characteristics of the functional group by
TG-FTIR. Finally, we established an effective and prompt procedure for receiving information on thermal decomposition characteristics
and reaction hazard of MWCNTs that could be applied as an inherently safer design during normal or upset operation.
Detailed thermal analysis of manganese(II) complexes with a-amino acids were carried out. The thermal degradation is multi-stage.
Dehydration of complexes is the first mass loss step. Anhydrous compounds are unstable and decompose to Mn3O4 in air or to MnO in inert atmosphere. The intermediate solid products were identified by TG method and TG/FTIR combined technique.
Among others solid residues, the presence of MnSO4, MnBr2 and Mn(CH3COO)Cl was found. In the gaseous products of decomposition of organic ligand H2O, NH3, CO2, CO, aromatic and non-aromatic hydrocarbons and very probably cyanoacetic acid and dimethyl sulfide occurred. Inorganic ions,
i.e. Cl-, Br-or So42-remain in the solid products of decomposition or are lost as HCl, HBr or SO2.
Identification and monitoring of gaseous
species released during thermal decomposition of pure thiourea, (NH2)2C=S
in argon, helium and air atmosphere have been carried out by both online coupled
TG-FTIR and simultaneous TG/DTA-MS apparatuses manufactured by TA Instruments
(USA). In both inert atmospheres and air between 182 and 240°C the main
gaseous products of thiourea are ammonia (NH3) and
carbon disulfide (CS2), whilst in flowing air sulphur
dioxide (SO2) and carbonyl sulphide (COS) as gas phase
oxidation products of CS2, and in addition hydrogen
cyanide (HCN) also occur, which are detected by both FTIR spectroscopic and
mass spectrometric EGA methods. Some evolution of isothiocyanic acid (HNCS)
and cyanamide (NH2CN) vapours have also observed mainly
by EGA-FTIR, and largely depending on the experimental conditions. HNCS is
hardly identified by mass spectrometry. Any evolution of H2S
has not been detected at any stage of thiourea degradation by either of the
two methods. The exothermic heat effect of gas phase oxidation process of
CS2 partially compensates the endothermicity of the
corresponding degradation step producing CS2.
Authors:János Madarász, Ana Brăileanu, Maria Crişan, Malina Răileanu, and György Pokol
Thermal decomposition of an amorphous precursor for S-doped titania (TiO2) nanopowders, prepared by controlled sol–gel hydrolysis–condensation of titanium(IV) tetraethoxide and thiourea in aqueous
ethanol, has been studied up to 800 °C in flowing air. Simultaneous thermogravimetric and differential thermal analysis coupled
online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) have been applied for analysis
of released gases (EGA) and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication
techniques of the aimed S:TiO2 photocatalysts with photocatalytic activities under visible light. The precursor sample prepared with thiourea, released
first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 240 °C in two stages, ammonia
(NH3) from 170 to 350 °C in three steps, and organic mater (probably ether and ethylene) between 140 and 230 °C. The evolution
of CO2, H2O and SO2, as oxidation products, occurs between 180 and 240 °C, accompanied by exothermic DTA peaks at 190 and 235 °C. Some small
mass gain occurs before the following exothermic heat effect at 500 °C, which is probably due to the simultaneous burning
out of residual carbonaceous and sulphureous species, and transformation of amorphous titania into anatase. The oxidative
process is accompanied by evolution of CO2 and SO2. Anatase, which formed also in the exothermic peak at 500 °C, mainly keeps its structure, since only 10% of rutile formation
is detected below or at 800 °C by XRD. Meanwhile, from 500 °C, a final burning off organics is also indicated by continuous
CO2 evolution and small exothermic effects.
Authors:Kairi Otto, Petra Bombicz, János Madarász, Ilona Oja Acik, Malle Krunks, and György Pokol
atmospheres by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) or FTIR spectrometric gas cell (TG-FTIR).
Preparation of samples
Authors:I. Pitkänen, J. Huttunen, H. Halttunen, and R. Vesterinen
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 100C mainly
lost water and a little ammonia.
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.