Catalysis with carbides

Recent research in this field has led to very interesting developments in two areas: the use of SiC as a support material and the use of new transition metal carbides as active catalyst phases. The high thermal conductivity of SiC and the fact that it can be formed form carbon that has any shape or porosity, due to the ‘shape memory effect’, are strong positive attributes for future development. The transition metal carbides that are active catalytic phases, are also showing promise as a novel catalytic materials in several reactions, including three-way auto-exhaust catalysts and hydrocarbon selective dehydrogenation of isomerization reactions. Particularly exciting is the discovery that Mo oxycarbide can selectively isomerize n-heptane with good selectivity, contravening existing wisdom that only acidic catalysts can isomerize pentane and hexane but not heptane without production of extensive cracked side products. A new surface phase oxycarbide has been discovered that may be described as a carbon stabilized sheer structure of a MoO3 surface plane. That is, the sheer planes contain carbon atoms which stabilize the partially reduced structure of MoO3 and block its reduction to MoO2.