REACTION-PATH ANALYSIS OF A HOMOGENEOUS METHANE OXIDATIVE COUPLING MECHANISM

A literature mechanism describing the kinetics of homogeneous methane oxidative coupling is investigated by differential reaction-path analysis. The concentration data base was constructed by simulating gas phase methane coupling in an ideal plug-flow reactor under isothermal conditions. The dominant creative and destructive channels of major species are identified along the reaction path, thus providing valuable insight into the interaction between selective and non-selective submechanisms. Intermediate oxygenated compounds produced by partial oxidation of vinyl and methyl radicals are shown to sustain and promote methane conversion by supplying considerable fractions of active chain carriers (HO2, OH, H). Simulations with limiting kinetic models indicate that improved yields are to be expected from coupling surfaces which inhibit the partial oxidation of vinyl radicals, diminish the gas-phase hydroperoxy radical pool, and catalyze selective and secondary non-selective reactions requiring direct participation of oxygen.