A strategy for assessing thermal hazards of chemical manufacturing processes is presented with an emphasis on new developments in the areas of the desired and decomposition reaction research. In the case of the desired reaction, the application of a computer program, CAMEO, for assessing synthetic reaction pathways, and enthalpies, and for evaluating the chemistry of specific failure modes is demonstrated. For the decomposition reaction, an unexpected decomposition destabilization phenomenon in mixtures was observed, which clearly demonstrated the need for chemical/solvent mixture testing to provide reliable thermochemical data for reaction hazard assessment. An application of the reaction mixture hazard evaluation strategy to a chemical process is presented.
Authors:F. Lemos, M. Muraro, J. Zukerman-Schpector, É. Cavalheiro, and E. Dockal
The iron(II) complex of the Schiff bases trans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn), manganese(II) and vanadyl complexes of the Schiff bases cis- andtrans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn) were prepared and characterized by IR spectroscopy, and elemental analysis.
These new complexes were submitted to thermal analysis (TG and DSC) under dynamic air atmosphere. The differences in the decomposition
profiles were related to the structure of isomers and decomposition intermediates were characterized according to their X-ray
diffraction pattern and by their infrared spectrum.
The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The
salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC
methods up to 1200C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and
carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values
of the transition enthalpy were determinated.
The chemical-physical decomposition processes that occur in a brake pad heated to 1000C have been studied. This temperature
can be reached when a brake pad is applied. Thermogravimetry and differential thermal analysis were used in combination with
evolved gas analysis, and image analysis using a scanning electron microscope.
A brake pad is essentially a mixture of iron, carbon and binder. Combined techniques have been used,because of chemical reaction
overlap, to determine how and at what temperature the binder decomposes, the coal and graphite combust and the iron oxidises.
This work enables the development of brake pads that are stable at high temperature.
Authors:Gy. Pátkai, I. Körmendy, and A. Körmendy-Domján
-Domján , A. ( 1998 ): A C-vitamin bomlásának modellezése . (The modelling of vitamin C decomposition.) Research report, project: OTKA T 014965, task: 2.1. Szent István University, Faculty of Food Science, Department of Canning Technology , Budapest
A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO4 and Ca3UO6. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ1 symmetric stretching modes of the (CO3)2- units are observed at 1094, 1087 and 1075 cm-1 in agreement with three structurally distinct (CO3)2- units. At 100°C, two bands are found at 1089 and 1078 cm-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.
The mineral stichtite was synthesised and its thermal decomposition measured using thermogravimetry coupled to an evolved
gas mass spectrometer. Mass loss steps were observed at 52, 294, 550 and 670�C attributed to dehydration, dehydroxylation
and loss of carbonate. The loss of carbonate occurred at higher temperatures than dehydroxylation.
The kinetics and mechanism of the dehydration and decomposition of heteropolyacids of molybdenum, tungsten and vanadium (H3+xYx+M12O40mH2O;
Y=Si, P; M=Mo, W) were studied. The data obtained on the dehydration kinetic parameters correlate with the expected structures,
of these crystal hydrates, the IR data and X-ray phase analysis.