Chemical and Thermal Decomposition

Pyrolysis, also termed thermolysis (Greek pur = fire thermos = warm luo = loosen), is a process of chemical and thermal decomposition, generally leading to smaller molecules. Semantically, the term thermolysis is more appropriate than pyrolysis, since fire implies the presence of oxygen and hence of reactive and oxygen-bearing intermediates. In most pyrolysis processes, however, air is excluded, for reasons of safety, product quality, and yield. 

Zhulanova, V.P., Barmov, S.I., Pugachev, V.M., Ryabykh, S.M. Products of the radiation-chemical and thermal decomposition of mercury fulminate. High Energy Chem. 35, 26-32 (2001)... 

Kanzawa, A., Y. Arai, 1981. Thermal energy storage by the chemical reaction (Augmentation of heat transfer and thermal decomposition in the CaO/Ca(OH)2 powder), Solar Energy, 289-294. 

The heat of decomposition (238.4 kJ/mol, 3.92 kJ/g) has been calculated to give an adiabatic product temperature of 2150°C accompanied by a 24-fold pressure increase in a closed vessel [9], Dining research into the Friedel-Crafts acylation reaction of aromatic compounds (components unspecified) in nitrobenzene as solvent, it was decided to use nitromethane in place of nitrobenzene because of the lower toxicity of the former. However, because of the lower boiling point of nitromethane (101°C, against 210°C for nitrobenzene), the reactions were run in an autoclave so that the same maximum reaction temperature of 155°C could be used, but at a maximum pressure of 10 bar. The reaction mixture was heated to 150°C and maintained there for 10 minutes, when a rapidly accelerating increase in temperature was noticed, and at 160°C the lid of the autoclave was blown off as decomposition accelerated to explosion [10], Impurities present in the commercial solvent are listed, and a recommended purification procedure is described [11]. The thermal decomposition of nitromethane under supercritical conditions has been studied [12], The effects of very high pressure and of temperature on the physical properties, chemical reactivity and thermal decomposition of nitromethane have been studied, and a mechanism for the bimolecular decomposition (to ammonium formate and water) identified [13], Solid nitromethane apparently has different susceptibility to detonation according to the orientation of the crystal, a theoretical model is advanced [14], Nitromethane actually finds employment as an explosive [15],... 

However, pyrolysis is rapid, avoids sample wet chemical workup, avoiding sample loss and contamination, and has a low sample requirement. It allows the determination, in a single step, of polymeric materials (with in situ hydrolysis of the hydrolysable polymers and thermal decomposition of the nonhydrolysable polymers) and low molecular weight components [16]. As a result, pyrolysis is a relatively fast and inexpensive technique, especially if compared with the classical wet analytical procedures that are required prior to GC/MS analyses. 

The formation of novel silicon-rich synthetic zeolites has been facilitated by the use of templates, such as large quaternary ammonium cations instead of Na+. For instance, the tetramethylammonium cation, [(CH3)4N], is used in the synthesis of ZK-4. The aluminosilicate framework condenses around this large cation, which can subsequently be removed by chemical or thermal decomposition. ZSM-5 is produced in a similar way using the tetra-.n-propyl ammonium ion. Only a limited number of large cations can fit into the zeolite framework, and this severely reduces the number of [AIO4] tetrahedra that can be present, producing a silicon-rich structure. 

The chemical and thermal stability of the fluorophosphine complexes is markedly increased in every case over the chlorophosphine complexes, none of the latter being volatile. The stability of the fluorophophine complexes as compared with the parent carbonyl is also noteworthy. While nickel carbonyl is distillable only with considerable decomposition, tetrakis(trifluorophosphine)nickel-(0) is far more stable on distillation at atmospheric pressure, and can also conveniently be handled in a high-vacuum system. 

The central thesis of the theory of the non-steady combustion of powders and explosives developed by Ya.B. in this article is the assumption of rapid readjustability of the gas phase of combustion compared to thermal changes in the condensed phase, which allows us to consider the gas phase as quasi-steady. This fundamental property of burning condensed materials allows us not only to significantly simplify the solution of the problem by reducing it to an analysis of the non-steady temperature distribution in the surface layer of the condensed material, but also not to carry out a detailed analysis of the complex structure of the combustion zone above the material (the multi-stage character of the chemical transformation, thermal decomposition, and gasification of the dispersed particles of condensed material and other processes). 

Furthermore, properties of chemical and thermal resistances are expected when the fluorinated groups are located in the main chain. Thus the authors investigated the fluorinated chain/functional group stability. So far, aromatic groups are usually used but the syntheses require many steps and therefore the yields are still poor. However, novel and interesting polymers have been prepared. They have glass transition temperatures higher than 200 °C, decomposition-temperatures which reach 400 °C and a satisfactory softness which represents the weak point of the non fluorinated thermostable products. 

Singlet oxygen can be generated by a variety of chemical reactions including decomposition of H202, peroxyacids, and thermal decomposition of ozonides (Section 11-3) such as (Ph0)3P03 or Na2M08, M=Mo or W, in basic aqueous systems.18 In the reactions... 

As a rule dipyrylenes are characterized by chemical and thermal stability, but under special conditions cleavage of the ethylene bond can be achieved. Thus, on heating with thionyl chloride followed by treatment with water, the tetraphenyl derivative (52c) is converted into 2,6-diphenyl-4l/-pyran-4-one.50,108 Only decomposition products were isolated with the corresponding methoxyphenyl derivative (52d). 

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