OXIDATIVE DEHYDROGENATION OF BUTANE OVER ORTHOVANADATES

The oxidative dehydrogenation of butane was studied over NdVO4, SmVO4, EuVO4, and Ba3(VO4)2 at 500 and 540°C. It was found that NdVO4 and SMVO4 were both quite active and selective for dehydrogenation, but EUVO4 was less selective although very active. The products were butenes, butadiene, carbon oxides, and small amounts of CZ and C3 hydrocarbons. The selectivities for butenes over NdVO4, SMVO4, mixed V-Mg-oxide, and Mg3(VO4)2 were found to be the same, but V-Mg-0 was much more selective for butadiene than the other catalysts were. Ba3(VO4)2 was selective, but both its activity and selectivity declined with time on stream due to the formation of BaCO3. These oxides also showed different behaviors in temperature-programmed reduction and reoxidation. These observations can be explained by a model that relates the redox behavior of a catalyst to the availability of oxygen at the active site and thus to the catalytic behavior. © 1990.