Selective oxidation of ethanol on V-MCM-41 catalysts

Abstract

Catalysts V-MCM-41 with different V contents (0.09-0.90 wt.%), synthesized by the template ion-exchange (TIE) method, have been investigated for acetaldehyde production by selective oxidation of ethanol, studying the effects of reaction temperature, O2/ethanol molar ratio and V content of the catalyst. The catalysts were characterized by X-ray diffraction (XRD), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), diffuse reflectance UV–vis spectroscopy (UV–vis-DR), N2 adsorption and Fourier transform infrared spectroscopy (FT-IR) with pyridine adsorption. All the catalysts showed good structural regularity and high specific areas. Analysis by UV–vis-DR showed the presence of different V species: isolated V cations incorporated to the siliceous structure or on the pore wall, clusters with different sizes and segregated nano-oxides in different proportions depending on the V content. Under the reaction conditions explored, the maximum acetaldehyde selectivity (90.5%) was reached at 623 K but the maximum yield (48% yield with 77% selectivity) was reached at 673 K, using a feed molar ratio O2/ethanol = 1. The activity of the catalysts decreased with the increase in V contents, due to the different type and increasing aggregation of V species, the most active catalyst being the one with the highest dispersion of isolated tetrahedral V species.