Thermal decomposition pressure behaviour

Ebner, W. B. etal., Proc. 8th Power Sources Symp., 119-124, 1982 An ARC study of the thermal and pressure behaviour of actual electric batteries under various atypical conditions showed the major contributions to the exothermic behaviour as the reactions between lithium and acetonitrile, lithium and sulfur and the decomposition of lithium dithionite. The first reaction can generate enough heat to trigger other exothermic rections. The hazards associated with the various parameters are quantified. 

TG-MS is ideally suited to reveal differences in pressure behaviour during thermal decomposition of materials. This has been illustrated by Mol [144] in TG-MS analysis of toluene diisocyanate (TDI) and methylene bis-4-phenol isocyanate (MDI)-based polyurethanes, where the observed greater increase in pressure for the TDI polyurethane than for the MDI derivative indicates a higher loss of low molecular weight fragments. This is not possible to deduct from the TG curves alone. Such indications are of great... 

For many seemingly simple processes, complex kinetic behaviour has been observed, such as the thermal decomposition of CaC03 and the dehydration of CaC204 H20, both of which produce a single gaseous product and, therefore, are often considered as model or standard single-step processes. However, these are reversible processes, and their kinetics are determined not only by die temperature, but also by the equilibrium and actual pressure of the gaseous product. 

Finally, Fig. 2.22 illustrates the kinetic curve behaviour for the source reactant and the end product of ethane thermal decomposition. The calculations assume that the process proceeds at a temperature of 1,100 K and at an initial pressure of the gas mixture 2 atm. One should remember that, in this case, it is considered an approximate solution obtained in the framework of the approximation about a steady-state course of the process. 

In all instances, soft ionization of the analyte molecules is achieved, i.e. generally little fragmentation is observed. Obviously, there are a number of parameters other than the solvent composition that determine the ionization behaviour, e.g. analyte properties, temperatures, pressure. The temperature plays an important role because of its many influences on the ionization behaviour, but also on the production of ions due to thermal decomposition of thermolabile analytes. In most cases, thermal decomposition of analytes already takes place in the... 

The explosive decomposition of the solid has been studied in detail [6], The effect of moisture upon ignitibility and explosive behaviour under confinement was studied. A moisture content of 3% allowed slow burning only, and at 5% ignition did not occur [7], Thermal instability was studied using a pressure vessel test, ignition delay time, TGA and DSC, and decomposition products were identified [8], The presence of acyl chlorides renders dibenzoyl peroxide impact-sensitive [9], There is a further report of a violent explosion during purification of the peroxide by Soxhlet extraction with hot chloroform [10], Residual traces of the peroxide in a polythene feed pipe exploded when it was cut with a handsaw [11]. The heat of decomposition has been determined as 1.39 kJ/g. The recently calculated value of 69° C for critical ignition temperature coincides with that previously recorded. 

Thermal unimolecular reactions usually exhibit first-order kinetics at high pressures. As pointed out originally by Lindemann [1], such behaviour is found because collisionally energised molecules require a finite time for decomposition at high pressures, collisional excitation and de-excitation are sufficiently rapid to maintain an equilibrium distribution of excited molecules. Rice and Ramsperger [2] and, independently, Kassel [3] (RRK), realised that a detailed theory must take account of the variation of decomposition rate of an excited molecule with its degree of internal excitation. Kassel s theory is still widely used and is valid for the chosen model of a set of coupled, classical, harmonic oscillators. 

Differences and similarities in the behaviour of reactions induced thermally and by CO2 laser radiation at relatively high pressures have been described in several cases. Decomposition of CH3CF2CI with a CW laser source takes place with a rate constant equal to the thermal value at 200 Torr, but vibrational and translational degrees of freedom appear not to be completely equilibrated at lower pressures. 

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