Oxidative dehydrogenation of ethylbenzene to styrene with CO2 over Al‐MCM‐41‐supported vanadia catalysts

Abstract

Catalytic performance of Al‐MCM‐41‐supported vanadia catalysts (V/Al‐MCM‐41) with different V loading was investigated for oxidative dehydrogenation of ethylbenzene to styrene (ST) with CO2 (CO2‐ODEB). For comparison, pure silica MCM‐41 was also used as support for vanadia catalyst. The catalysts were characterized by N2 adsorption, X‐ray diffraction (XRD) pyridine‐Fourier‐transform infrared spectroscopy, H2‐temperature‐programmed reduction, thermogravimetric analysis (TGA), UV‐Raman, and diffuse reflectance (DR) UV–vis spectroscopy. The results indicate that the catalytic behavior and the nature of V species depend strongly on the V loading and the support properties. Compared with the MCM‐41‐supported catalyst, the Al‐MCM‐41‐supported vanadia catalyst exhibits much higher catalytic activity and stability along with a high ST selectivity (>98%). The superior catalytic performance of the present V/Al‐MCM‐41 catalyst can be attributed to the Al‐MCM‐41 support being more favorable for the high dispersion of V species and the stabilization of active V5+ species. Together with the characterization results of XRD, TGA, and DR UV–Vis spectroscopy, the deep reduction of V5+ into V3+ during CO2‐ODEB is the main reason for the deactivation of the supported vanadia catalyst, while the coke deposition has a less important impact on the catalyst stability.