Structural Characterization and Oxidehydrogenation Activity of CeO₂/Al₂O₃and V₂O₅/CeO₂/Al₂O₃Catalysts

Structural characterization and oxidative dehydrogenation activity of CeO 2 /Al 2 O 3 and V 2 O 5 /CeO 2 /Al 2 O 3 catalysts for ethylbenzene (EB) to styrene were investigated systematically. The CeO 2 /Al 2 O 3 catalyst was prepared by a deposition precipitation method, and a theoretical monolayer equivalent of 10 wt % V 2 O 5 was dispersed over its surface by a wet impregnation method to obtain the V 2 O 5 /CeO 2 /Al 2 O 3 catalyst. To understand thermal and textural stability, the synthesized catalysts were subjected to calcination at various temperatures (773−1073 K). Physicochemical characterization was performed using X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, and BET surface area techniques. The XRD and RS results suggested that the CeO 2 /Al 2 O 3 sample is thermally quite stable up to 1073 K and that the ceria exists in the form of an over layer on the surface of the alumina support. In the case of the V 2 O 5 /CeO 2 /Al 2 O 3 sample, no crystalline V 2 O 5 was observed from XRD results, indicating a highly dispersed form of vanadium oxide on the CeO 2 /Al 2 O 3 carrier when calcined at 773 K. The XPS peak shapes and the corresponding electron binding energies indicate that the dispersed vanadium oxide selectively interacts with the ceria portion of the CeO 2 /Al 2 O 3 support and forms a CeVO 4 compound at higher calcination temperatures. Formation of CeVO 4 is also established from XRD and RS measurements. Both CeO 2 /Al 2 O 3 and V 2 O 5 /CeO 2 /Al 2 O 3 samples were tested for oxidative dehydrogenation of EB to styrene by using dry air as an oxidant. The V 2 O 5 /CeO 2 /Al 2 O 3 catalyst exhibits more conversion and selectivity than CeO 2 /Al 2 O 3 . The time-on-stream experiments further reveal that the V 2 O 5 /CeO 2 /Al 2 O 3 catalyst exhibits stable activity and selectivity without fast deactivation.