LAMELLAR PEROVSKITES MI (AN-1BNO3N+1) CATALYSTS FOR OXIDATIVE COUPLING OF METHANE

The aim of this work concerns the study of new lamellar perovskites M(I) (An-1BnO3n+1) as catalysts for the oxidative coupling of methane. The main results show that: Substitution in an octahedral site (B) strongly modifies both activity and selectivity. In this site niobium (an element of Group V) leads to a more selective catalyst. Substitution either of the A cation in the perovskite site or of the interlamellar cation (M(I)) modifies the selectivity more than the activity. An increase in the thickness (n) of the layer decreases both activity and selectivity. It can be considered as a structural effect in the oxidative coupling of methane. Variations of catalytic properties can be correlated to the covalent character of the B-O bond. The reactional center can be described as a polaron created at a structural defect, the existence of very localized centers being less probable at such high temperatures.