Utilization of criterial equations for quantitative processing of thermogravimetric results

Abstract

A system of criterial equations is proposed for determining the parameters of kinetic equations by thermogravimetric results. The criterial equations take into account the particularities of the effect of each parameter on the shape and position of the TG curve. It is shown that the method ensures uniqueness of the solution obtained, which best fits to the experimental data.Although TG is widely used to study the kinetics of solid-phase reactions, reports of various authors cannot always be considered as reliable.The factors affecting the quality of mathematical description of processes taking place under non-isothermal conditions may be divided into two major groups: those connected with the authenticity of the experimental procedure, and those related to the selection of the method for quantitative description of TG results.In this paper we do not deal with the authenticity of the experiments, and assume that the experimental data are reliable, i.e. the temperature recorded is equal to the temperature of the sample studied (and the temperature is constant in the whole sample), and that the distortions of mass loss caused by apparatus and other noises can be neglected. About the details of the procedure regarding the above requirements see [3,5].For the mathematical description of chemical processes taking place in solid phase, the equation of formal kinetics is utilized most frequently, assuming that the temperature dependence of the rate of reaction follows the Arrhenius law:or for the case of uniform temperature increase: d~/dT = (Z/q) exp (-E/RT)(I -~)"