Oxydehydrogenation of n-butane over promoted MgV-oxide based catalysts Original Research Article

Magnesium vanadate, Mg2V2Ox, and promoted systems of the composition Mg4V2M2Ox, where M = Mo, W, B, Al, Ga, Sb and (SbP), were synthesized, characterized and evaluated for the oxydehydrogenation of n-butane in the temperature range 400–500°C and atmospheric pressure. The selectivities to butene/butadiene of the majority of the promoted catalysts are, at 500°C and constant n-butane conversion (2%), substantially higher than those of the base system: Sb(87), SbP(82), B(82), Mo(68), Al(62), base(55), W(50). The superior selectivities of the antimony and boron containing compositions are probably primarily due to the formation of ternary MgVSb-oxide Mg1−xSbV2/3xO3.5) and MgVB-oxide (Mg1−xBV2/3O2.5) phases, contributing to the structural site isolation of the paraffin activating vanadium sites; the stabilization of the V4+ or lower oxidation states; and their possible interaction with an inferred supra-surface Sb-oxide phase. Highest butene/butadiene per pass yields were obtained with a Mg4V2Ga2Ox catalyst (5.2% at 7.9% conversion, at 500°C, 1 atm, C40/O2/N2 = 5/1/20, and WHSV = 13 h−1). The only composition yielding measurable amounts of furan was the W promoted catalyst.