Anaerobic oxidation of butane to butadiene over magnesium molybdate catalysts .1. Magnesia supported catalysts

A potential new process to styrene monomer from n-butane consists of oxidation of n-butane to butadiene followed by dimerization of butadiene to 4-vinylcyclohexene (VCH) and oxydehydrogenation of VCH to styrene. In this paper we report a catalyst which provides 40%-50% conversion of n-butane at 80% selectivity to butadiene and the n-butenes when exposed to 5-10 s pulses of n-butane followed by air regeneration. The optimum catalyst consists of 15%-25% MoO3 dispersed on MgO. The addition of small amounts of alkali metal compounds are used to minimize the production of carbon oxides. Characterization of these catalysts by laser Raman spectroscopy and XANES indicates that octahedral polymolybdates and micro crystals of MgMoO4 are initially the major species at molybdenum loadings corresponding to maximum activity on fresh catalyst. Designed experiments have resulted in models predicting the relationship of selectivity and conversion for various process conditions.