STUDY ON THE OXIDATIVE COUPLING OF METHANE - XRD AND XPS STUDY OF TIO2-BASED CATALYSTS PROMOTED BY DIFFERENT ADDITIVES

The catalytic performance of Mn/TiO2, La-Mn/TiO2, Li-Mn/TiO2 and Li-La -Mn/TiO2 for the oxidative coupling of methane (OCM) was investigated. The catalysts were characterized with XRD and X-ray photoelectron spe ctroscopy (XPS). The results revealed that catalyst Li-La-Mn/TiO2 exhi bited high activity and C-2 selectivity, Ti in this catalyst existed i n the Ti(IV) state; Li could promote the formation of lanthanum titana te via the interaction of La and TiO2, the formed La2Ti2O7 and La-4 Ti 9O24 distributed in the inner surface layer and Mn existed in the oute r surface layer in low valence number. The high activity and C-2 selec tivity of catalyst Li-La-Mn/TiO2 were intimately related to the valenc e number of Mn, Li, La and to their distribution on the catalyst surfa ce layer.