Microwave assisted synthesis of a VOx-modified disordered mesoporous silica for ethylbenzene dehydrogenation in presence of CO2

Abstract

The aim of the study was to investigate the effect of different vanadium loading incorporated into hexagonal mesoporous silica (HMS) support on texture, speciation of vanadyl complexes and catalytic performance. These catalysts are prepared with different vanadium loadings (5–30 wt.%) using solution impregnation technique with ammonium metavanadate as a precursor followed by calcination and microwave treatment, and denoted as Cal-x. and MW-x, respectively. The structure of the prepared catalysts are then characterized utilizing the X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area measurements, ammonia temperature programmed desorption (TPD-NH3), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), Raman Spectroscopy and Ultraviolet–visible spectroscopy (UV–vis). The characterization of the supported VOx/HMS catalysts by Raman spectroscopy reveals that monomeric VOx species are dominant for MW-catalysts loadings. All prepared catalysts were tested in the oxidative dehydrogenation (ODH) of ethylbenzene (EB) in the presence of carbon dioxide (CO2). The results revealed that the optimum catalytic activity and the selectivity to styrene production were obtained using 20 wt.% V2O5/HMS (MW-20) catalyst.