Propane Oxidative Dehydrogenation on BiP1-xVxO4 Supported Titania Catalysts

Authors

• Mbarka Ouchabi ¹
• Loulidi Ilyasse * ²
• Mahfoud Agunaou ¹

1. Laboratory of Catalysis and Corrosion of Materials, Chouaïb Doukkali University, Faculty of Sciences El Jadida, BP. 20, El Jadida, Morocco
2. Laboratory of Chemistry and Biology Applied to the Environment, Faculty of Sciences, Moulay Ismail University, BP 11201-Zitoune, Meknes, Morocco

Abstract

The molecularly dispersed BiP_1-xV_xO₄/TiO₂ supported materials, with x varying from 0 to 1, were prepared by impregnation of Bismuth, Phosphorus, and Vanadium on a Titanium Oxide TiO₂ support. Their structures were characterized by different techniques including X-ray diffraction, Spectroscopic Raman, temperature-programmed reduction of the catalysts in H₂ (H₂-TPR), and by the methanol oxidation reaction. This very sensitive technique provided us with relevant information on the nature of the catalytic active sites (acid-base and redox) of the phases dispersed on the support. The characterization results show the structural evolution of BiP_1-xV_xO₄ species, from isolated BiPO₄ crystallites for x =0, to BiVO₄ crystallites x =1. The oxidation of methanol showed the acidic properties of the BiPO₄/TiO₂ catalyst, through the formation of dimethyl ether as the major product of the reaction. The substitution of phosphorus by vanadium promotes the formation of formaldehyde, confirming the presence of redox sites. These catalysts were examined in the oxidative dehydrogenation (ODH) of propane to propene.  For x > 0.5, dispersed BiVO₄ exhibited higher levels of propane ODH than BiPO₄ crystallites, consistent with their greater reducibility probed by temperature-programmed reduction of H₂ and the presence of redox sites confirmed by methanol oxidation, with good selectivity to propene. Catalysts with x = 0, were less selective to propene due to favorable propylene combustion during its formation. A thorough understanding of the intrinsic catalytic properties of the BiP_1-xV_xO₄/TiO₂ oxides and in particular the BiPO₄ and BiVO₄ crystallites provides relevant information on the structural requirements of the propane ODH reaction, of interest for the design of more efficient Bi-P-V-O based catalysts for propene production. The results show that all substituted catalysts exhibit significant propene selectivity. In addition, the BiP_0.7V_0.3O₄/TiO₂ catalyst exhibits high activity with good propene selectivity. This catalytic activity was correlated with high reducibility.

Highlights

• The molecularly BiP1-xVxO4/TiO2 supported materials, with x varying from 0 to 1 were prepared characterized
• The oxidation of methanol showed the acidic properties of the BiPO4/TiO2 catalyst.
• The presence of redox sites.
• All substituted catalysts exhibit significant propene selectivity.
• The catalytic activity was correlated with high reducibility

Graphical Abstract

Keywords

• BiP1-xVxO4/TiO2 catalyst
• Methanol oxidation
• Propane oxidative dehydrogenation