OXIDATIVE COUPLING OF METHANE TO HIGHER HYDROCARBONS

Abstract

This review has attempted to extract principles from the literature that would help to understand the fundamental nature of oxidative coupling of methane over solid surfaces. It appears that many catalysts and reagents generate gas-phase methyl radical intermediates which undergo subsequent hydrocarbon building steps in the gas phase. In parallel steps, CO//x is formed from both methane and hydrocarbon products. The relative contributions from each source depend on the reaction conditions. The nature of the active sites for initial methane activation is not well understood except for one irreducible oxide, Li/MgO. For this irreducible oxide, EPR combined with a matrix isolation technique has indicated that paramagnetic sites are responsible for the formation of methyl radials. For other types of oxides, there are a number of proposed active species, but the evidence for these is slight. 64.