LAUSR

This paper deals with the systematization and classification of the theory of thermal decomposition of solid materials. We analyze the main innovations during the 130 years since the publication of the classic works by van’t Hoff in 1884 and Arrhenius in 1889. These innovations concern mainly the mechanism and kinetics of decomposition. In kinetics three different models are considered, the van’t Hoff thermodynamic model, the activation model of Arrhenius, and the thermochemical model developed by the present author. The two latter models are respectively based upon the Boltzmann statistical theory of the energy distribution of activated particles and the statistical theory of evaporation due to Langmuir. The activation model is inconsistent with the thermodynamic model because of the different mode in which temperature impacts reaction rate: via the relative concentration of active particles, in the first case, and through the equilibrium constant, in the second. The thermochemical model describes the impact of temperature on the rate in the same manner as the thermodynamic model and is therefore suitable for a detailed interpretation of decomposition kinetics. For about 30 years, it has been experimentally tested and described in dozens of papers and in two monographs. However, because of the negative opinion of the ICTAC Kinetics Committee, it has until now laid in shadow of the old activation model. To overcome the lasting crisis in the kinetics of heterogeneous reactions, it is necessary to promote discussion of the current situation and search for appropriate ways to replace activation model by the thermochemical model.