Home – Home – Jornals – Chemistry for Sustainable Development 2022 number 1

A review of systematic studies of unbranched radical-chain reactions by the example of pyrolysis of hydrocarbons and dichloroethane with the participation of heterogeneous catalysts is presented. It is shown that the determining role in catalytic pyrolysis is played not by the concentration of surface or gas-phase active centres but by the total concentration of free radicals per unit reaction volume, which determines the heterogeneous-homogeneous nature of the process. Four types of surface impact on the process have been identified: inhibitory, neutral, accelerating the heterogeneous or homogeneous components of the process. A phenomenological model of these reactions and experimental evidence of its validity are proposed. For catalysts that accelerate the homogeneous component, the effect of “ignition” of the catalyst activity is detected, and its nature is explained. The concept of catalysis spheres is introduced - the areas above the catalyst with an increased concentration of radicals. Its dimensions and conditions of existence are determined. Experimental criteria for the emergence of the sphere are determined. Techniques of purposeful selection and synthesis of catalysts, selection of methods of technological arrangement of radical-chain heterogeneous-homogeneous processes are shown.