Oxidative dehydrogenation of ethylbenzene to styrene with CO 2 over Al‐MCM‐41‐supported vanadia catalysts

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 CO 2 (CO 2 ‐ODEB). For comparison, pure silica MCM‐41 was also used as support for vanadia catalyst. The catalysts were characterized by N 2 adsorption, X‐ray diffraction (XRD) pyridine‐Fourier‐transform infrared spectroscopy, H 2 ‐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 V 5+ species. Together with the characterization results of XRD, TGA, and DR UV–Vis spectroscopy, the deep reduction of V 5+ into V 3+ during CO 2 ‐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.