CARBON-HYDROGEN BOND ACTIVATION OVER TUNGSTEN CARBIDE CATALYSTS

Tungsten carbides with surface areas ranging from 4 to 39 m(2)/g were prepared by the temperature-programmed carburization of tungsten oxide and nitride powders with pure CH4 or a 48.9% CH4 in H-2 mixture. Oxyg en uptakes on the carbides were low most likely because of the presenc e of graphitic carbon at the surface. Nevertheless, the carbides were active and selective for the dehydrogenation of butane at temperatures between 623 and 723 K and atmospheric pressure with and without H-2 i n the reactant feed. With H-2 in the feed, the higher surface area car bides (greater than or equal to 36 m(2)/g) were as active as a Pt-Sn/g amma-Al2O3 catalyst, but their selectivities were different. Without H , in the feed, the selectivities of the carbides were similar to those of the Pt-Sn/gamma-Al2O3 catalyst, but their reaction rates were 1-3 orders of magnitude lower. The high surface area materials were also a ctive for the hydrogenolysis of butane. Because the catalytic properti es of the carbides varied with the average particle size, we concluded that butane dehydrogenation was structure-sensitive over these materi als, and suspected that this behavior was due to variations in the sur face stoichiometry as well as the particle faceting.