Effect of ceria on the structure and catalytic activity of V2O5/TiO2–ZrO2 for oxidehydrogenation of ethylbenzene to styrene utilizing CO2 as soft oxidant

The present study was undertaken to investigate the influence of ceria on the physicochemical and catalytic properties of V2O5/TiO2–ZrO2 for oxidative dehydrogenation of ethylbenzene to styrene utilizing CO2 as a soft oxidant. Monolayer equivalents of ceria, vanadia and ceria–vanadia combination over TiO2–ZrO2 (TZ) support were impregnated by a coprecipitation and wet impregnation methods. Synthesized catalysts were characterized by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature programmed reduction, transmission electron microscopy and BET surface area methods. The XRD profiles of 550 °C calcined samples revealed amorphous nature of the materials. Upon increasing calcination temperature to 750 °C, in addition to ZrTiO4 peaks, few other lines due to ZrV2O7 and CeVO4 were observed. The XPS V 2p results revealed the existence of V4+ and V5+ species at 550 and 750 °C calcinations temperatures, respectively. TEM analysis suggested the presence of nanosized (<7 nm) particles with narrow range distribution. Raman measurements confirmed the formation ZrTiO4 under high temperature treatments. TPR measurements suggested a facile reduction of CeO2–V2O5/TZ sample. Among various samples evaluated, the CeO2–V2O5/TZ sample exhibited highest conversion and nearly 100% product selectivity. In particular, the addition of ceria to V2O5/TZ suppressed the coke deposition and allowed a stable and high catalytic activity.