Propane Oxidative Dehydrogenation on BiP۱-XVXO۴ Supported Silica Catalysts

The molecularly dispersed BiP۱-xVxO۴/SiO۲ supported oxides, with x varying from ۰ to ۱, were prepared by impregnation of Bismuth, Phosphorus, and Vanadium on silica. Their structures have been characterized by different techniques: X-ray diffraction, Raman spectroscopy, Temperature-Programmed Reduction of catalysts in H۲ (H۲-TPR), and methanol oxidation reaction. This very sensitive technique provided us with relevant information on the nature of the active sites (acid-base and redox) on the surface of the catalysts. The results of the characterization show the structural evolution of the vanadium species of the isolated crystallites from V۲O۵ for x =۰.۳ and x =۰.۵, to BiVO۴, with the disappearance of BiPO۴, with the increase of the vanadium content from x=۰.۵ to x = ۱. The oxidation of methanol showed the basic properties of the BiPO۴/SiO۲ catalyst, by the formation of carbon dioxide as the major product of the reaction. The substitution of phosphorus with vanadium promotes the formation of formaldehyde, confirming the presence of redox sites on these substituted catalysts. These catalysts were examined in the Oxidative dehydrogenation (ODH) of propane. For x ≥ ۰.۵, the dispersed BiVO۴ exhibited significant activity in propane ODH than the BiPO۴ and V۲O۵ crystallites, with good selectivity to propylene and acrolein, consistent with their high reducibility confirmed by H۲-TPR, and the presence of redox sites shown by the oxidation of methanol. The catalyst with x = ۰ was less selective for propylene due to the favorable combustion of propylene during its formation. Such an understanding of the intrinsic catalytic properties of the BiP۱-xVxO۴/SiO۲ oxides and in particular, the BiPO۴ and BiVO۴ crystallites provides new information on the structural requirements of the propane ODH reaction, beneficial for the design of more efficient Bi-P-V-O based catalysts for propylene and acrolein production.

کلیدواژه ها:

Oxidative dehydrogenation ، Propane ، Propylene ، Acrolein ، BiP۱-xVxO۴/SiO۲