Selective Oxidative Conversion of Propane to Olefins and Oxygenates on Boria-Containing Catalysts

Catalysts consisting of boria supported on Al2O3, TiO2, ZrO2 and MgO were studied in the partial oxidation of propane at 550 °C. The highest propene yield amounted to 22 % (S = 45 - 48 %) on B2O3/Al2O3; in addition, yields to C1-C3 oxygenates of up to 8 % were achieved (S = 28 %). Surface and bulk composition of the B-Al-O catalysts were investigated using 11B NMR, XRD and XPS to elucidate the factors determining propane conversion, product distribution and catalyst deactivation. It was shown that the coordination of boron influences catalyst activity; trigonal BO3 species being present in both crystalline and amorphous phases are active in the dehydrogenation of propane to propene. The water formed during the reaction causes the loss of these species most probably as boric acid. The catalyst consisting of amorphous boria revealed high initial activity but resulted in faster volatilization of boria compared to a catalyst consisting of crystalline B2O3 and aluminium borates. Oxygenates formation was favoured in the presence of an Al6B8O21 phase.