New families of catalysts for the selective oxidation of methane

Abstract

The catalytic performance of 11 chemically distinct crystalline solids, all of which have layered structures of either the Sillen, perite or bipox type in which infinite sheets of [Bi₂O₂]²⁺ or [PbBiO₂]⁺ are interleaved with other layers such as chloride ions, metal chlorides or tungsten oxide, is reported. Several kinds of well characterized Sillen structures, designated X₁, X₂, X₃, X_N, as well as regular intergrowths thereof, were tested. Some of these monophasic materials show good C₂ selectivity with ratios of C₂H₄/C₂H₆ ranging from ca. unity to in excess of 30 at temperatures close to 1000 K for the oxidative coupling of methane. Scope exists for further structural modification and the design of superior catalysts of other bismuth-containing solids based on fluorites and pyrochlores.