Propylene production via propane oxidative dehydrogenation over VOx/γ-Al2O3 catalyst

Abstract

This study contributes with a new vanadium oxide catalyst supported on γ-Al2O3 especially designed for propane ODH under oxygen-free conditions. This catalyst is prepared with different vanadium loadings (5–10wt.%) via wet impregnation using ammonium metavanadate as a precursor. The prepared catalyst is characterized using BET surface area, H2-TPR, NH3-TPD, O2 chemisorption, Laser Raman Spectroscopy, pyridine FT-IR and XRD. The characterization of the supported VOx/γ-Al2O3 catalysts by Raman spectroscopy reveals that monomeric VOx species are dominant at low vanadium loadings. Polymeric VOx species increase, however, at higher loadings until surface monolayer coverage is reached. Pyridine FTIR and NH3-TPD reveal that this VOx/γ-Al2O3 catalyst shows progressive acidity reduction with vanadium addition while compared to bare alumina. This controlled acidity reduction is achieved with a higher Brønsted acidity. The performance of the prepared catalysts is established having in mind possible industrial propane ODH applications. This is accomplished using a CREC Fluidized Bed Riser Simulator at 475–550°C and at atmospheric pressure. Successive propane injections for ODH experiments (without catalyst regeneration) over a partially reduced catalyst show that the prepared catalysts display promising propane conversions (11.73–15.11%) and propylene selectivities (67.65–85.89%) at 475–550°C. Propylene selectivity increases while that of COx decreases as the degree of catalyst reduction augments with consecutive propane injections. Under such oxygen-free conditions oxygen from the catalyst lattice is consumed via propane ODH. This demonstrates that a controlled degree of catalyst reduction is very desirable for high propylene selectivity in ODH.