OXIDATIVE CROSS-COUPLING OF METHANE AND TOLUENE OVER LICL-ADDED CO3O4

A LiCl-added Co3O4 has been found to be one of the most active catalysts for oxidative cross-coupling of methane and toluene. The reaction was examined at temperatures higher than 823 K and at a higher methane/toluene ratio than 10. In order to understand the whole network of this reaction, the kinetic studies on the homocoupling of each reactant have been carried out. The results suggested a Langmuir-H inshelwood type mechanism for both reactants; i.e., the rate-determining step is at the abstraction of hydrogen from methane or from toluene, forming methyl or benzyl species on the surface, respectively, or liberating the corresponding alkyl radicals into the gas phase. The coupling of the alkyl intermediates produces each coupling product, i.e., C2 and C14 compounds. Under methane and toluene cofeed conditions, the formation of C8 compounds (ethylbenzene and styrene) can be explained in terms of the coupling of methyl and benzyl intermediates. Although a large difference between the reactivities of methane and toluene made it difficult to carry out the kinetic studies on the cross-coupling of methane and toluene, the results were well interpreted in terms of the reaction mechanisms proposed for the oxidation of methane and that of toluene. © 1992.