Oxidative dehydrogenation of propane: Developing catalysts containing VOX, V-P-O and V-Mg-O species supported on MCM-41 and activated carbon

Abstract

Abstract Catalysts containing V-Mg-O species supported on activated carbon (AC), obtained from sugar-cane straw, were prepared and evaluated in the propane ODH reaction. Two conditions containing different molar amounts of Mg and V where prepared, one (condition II) with higher molar amounts of magnesium and vanadium than condition I, but the ratio of Mg/V = 1:2 was kept constant. For comparison purposes, the same preparation methodology was used but with MCM-41 as support, instead. The physicochemical properties of these catalysts were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Laser Raman spectroscopy (RS) and Scanning electron microscopy, coupled with energy dispersive microscopy (SEM-EDS). For the first time the nature of V-Mg-O species on an activated carbon surface was investigated. The electron environment around vanadium was evaluated by XPS, revealing the coexistence of V2O5 crystallites with highly dispersed species of Mg-V-O and P-V linkages on the surface. Vanadium enrichment was observed on the surface of those supported on activated carbon, especially for the preparation containing higher amounts of V and Mg. All the AC and MCM-41 supported catalysts were active and selective in ODH of propane into propylene and were stable for, at least 24 h, of reaction. The stability was attributed to the presence of the Mg-V linkages at the catalysts surface, while Phosphate CPO groups still exists, despite of the formation of V-P linkages.