Boron-Containing Catalysts for the Oxidative Dehydrogenation of Ethane/Propane Mixtures

Oxidative dehydrogenation (ODH) of ethane and propane feeds has been examined under a variety of temperatures, flow rates, and gas compositions in a fixed bed reactor using boron nitride-based catalysts either promoted with various metal oxides or supported on silica. Tests performed at low conversion in the presence of a large amount of N2 diluent indicated that addition of MgO to boron nitride (BN) led to a ∼10-fold increase in alkane conversion, with a drop in the C2–C3 olefin selectivity from 90% to 79%. Testing using concentrated feeds with small amounts of diluent (3%) indicated that metal-oxide promoted BN catalysts could maintain C2–C3 olefin selectivities as high as 65% at high alkane conversion (∼60%). Catalyst productivity values under these conditions approached 16 kgolefins kgcat –1 h–1. Under nondilute conditions, the catalysts appear to act as initiators of radical reactions at the surface, after which the radicals desorb into the gas phase and undergo propagation steps.