Structural characterization and oxidehydrogenation activity of CeO2/Al2O3 and V2O5/CeO2/Al2O3 catalysts

Structural characterization and oxidative dehydrogenation activity of CeO2/Al2O3 and V2O5/CeO2/Al2O3 catalysts for ethylbenzene (EB) to styrene were investigated systematically. The CeO2/Al2O3 catalyst was prepared by a deposition precipitation method, and a theoretical monolayer equivalent of 10 wt % V2O5 was dispersed over its surface by a wet impregnation method to obtain the V2O5/CeO2/Al2O3 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 CeO2/Al2O3 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 V2O5/CeO2/Al2O3 sample, no crystalline V2O5 Was observed from XRD results, indicating a highly dispersed form of vanadium oxide on the CeO2/Al2O3 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 CeO2/Al2O3 support and forms a CeVO4 compound at higher calcination temperatures. Formation of CeVO4 is also established from XRD and RS measurements. Both CeO2/Al2O3 and V2O5/CeO2/Al2O3 samples were tested for oxidative dehydrogenation of EB to styrene by using dry air as an oxidant. The V2O5/CeO2/Al2O3 catalyst exhibits more conversion and selectivity than CeO2/Al2O3. The time-on-stream experiments further reveal that the V2O5/CeO2/Al2O3 catalyst exhibits stable activity and selectivity without fast deactivation.