Modeling of oxidative transformations of light alkanes over heterogeneous catalysts

Abstract

An approach to modeling catalytic oxidative transformations of light alkanes (LAs) based on the use of thermochemical data is developed. The fact that LAs are virtually not adsorbed on the surface of oxidation catalysts seriously limits the possibility of experimentally studying the mechanisms of their transformations. In addition, LAs, the least reactive organic compounds, are oxidized at elevated temperatures even on the most active catalysts, a circumstance that makes the contribution from the homogeneous process to the overall conversion rate significant. For this reason, it is necessary to develop multilevel models capable of describing of the elementary reactions of LAs and intermediate products of their transformations (including free radicals of various types) with active sites of catalysts as well as the process as a whole. The proposed approach, based on the experimental data on the thermochemical properties of redox active sites, is applicable to describing processes occurring in the presence of an oxide catalyst. It makes it possible to estimate the kinetic parameters of the elementary interactions of molecules and radicals with active sites in reduced and oxidized states, that is, to solve the problem of the initial stage of modeling of a multistep process. A number of examples of applying this approach to studying oxidative transformations (partial oxidation and oxidative coupling) of methane, oxidative dehydrogenation of C2–C4 alkanes, and reoxidation of catalysts are considered. The prospects of modeling the heterogeneous-homogeneous oxidation of light alkanes are discussed.