The irreversible formation of methane in the system ethane-ethylene-hydrogen

Abstract

The irreversible formation of methane in the system C 2 H 6 ⇌ C 2 H 4 + H 2 has been studied by mass-spectrometric analysis and by kinetic methods. The methane is formed directly both from the ethane by a unimolecular reaction, little affected by nitric oxide, and from ethylene by a second-order reaction. In the formation from ethane in the presence of nitric oxide roughly two molecules of this are consumed for each molecule of methane (in marked contrast with the relatively small consumption in the decomposition of the higher paraffins). It is concluded that the major mode of production of methane from ethane is the reaction C 2 H 6 → CH 4 + CH 2 , the methylene suffering varying fates according to circumstances. From the ethylene-hydrogen side the methane arises by a primary condensation of ethylene followed by elimination of methane from the polymer. This is succeeded by further condensation and methane eliminations until a product approaching carbon in composition is left. Appreciable amounts of benzene are formed from some of the intermediates. In general, the amounts of the major products in the early stages of all the reactions are quite closely proportional to the pressure changes.