Utilization of carbon dioxide as soft oxidant for oxydehydrogenation of ethylbenzene to styrene over V2O5–CeO2/TiO2–ZrO2 catalyst

Vanadium oxide and cerium oxide doped titania–zirconia mixed oxides were explored for oxidative dehydrogenation of ethylbenzene to styrene utilizing carbon dioxide as a soft oxidant. The investigated TiO2–ZrO2 mixed oxide support with high specific surface area (207 m2 g−1) was synthesized by a coprecipitation method. Over the calcined support (550 °C), a monolayer equivalent (15 wt.%) of V2O5, CeO2 or a combination of both were deposited by using wet-impregnation or co-impregnation methods to make the V2O5/TiO2–ZrO2, CeO2/TiO2–ZrO2 and V2O5–CeO2/TiO2–ZrO2 combination catalysts, respectively. These catalysts were characterized using X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature preprogrammed reduction (TPR), CO2 temperature preprogrammed desorption (TPD) and BET surface area methods. All characterization studies revealed that the deposited promoter oxides are in a highly dispersed form over the support, and the combined acid–base and redox properties of the catalysts play a major role in this reaction. The V2O5–CeO2/TiO2–ZrO2 catalyst exhibited a better conversion and product selectivity than other combinations. In particular, the addition of CeO2 to V2O5/TiO2–ZrO2 prevented catalyst deactivation and helped to maintain a high and stable catalytic activity.