Studies of catalysis in partial oxidation of methane to syngas(II) - Chemisorbed species, energetics and mechanism

Abstract

The characteristic study, by means of in-situ IR spectroscopy, Of chemisorbed species on the Ni-catalysts for the partial oxidation of methane (POM) to syngas demonstrated the existence of CHx(a) and HxCO (a) adspecies on the functioning Ni-catalysts. Several designed experimental investigations on the reactivities of methane with CO2 and with O-2, respectively, over the Ni-catalysts, and of CO2 with the prereduced Ni-catalyst, as well as of the deposited carbon with CO2 and with O-2, respectively, have been carried out and the results were unfavorable to the two-step mechanistic interpretation proposed for the POM reaction. By means of the BOC-MP Approach, energetics of a set of elementary reactions, which may be involved in the POM process, on the clean (111) surface of Ni, Fe, Cu and Pd, respectively, has been studied. The results of the experiments and the calculation of the present work favor the direct catalytic dissociation-plus-surface oxidation-plus-further dehydrogenation mechanism as the dominant pathway making major contribution to the POM reaction.