Synthesis, characterization and catalytic activity of Nd2O3 supported V2O5 catalysts

A series of rare-earth neodymia supported vanadium oxide catalysts with various V2O5 loadings ranging from 3 to 15 wt.% were prepared by the wet impregnation method using ammonium metavanadate as the vanadium precursor. The nature of vanadia species formed on the support surface is characterized by a series of different physicochemical techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area, diffuse reflectance UV-vis spectroscopy (DR UV-vis), thermal analysis (TG-DTG/DTA) and SEM. The acidity of the prepared systems were verified by the stepwise temperature programmed desorption of ammonia (NH3-TPD) and found that the total acidity gets increased with the percentage of vanadia loading. XRD and FTIR results shows the presence of surface dispersed vanadyl species at lower loadings and the formation of higher vanadate species as the percentage composition of vanadia is increased above 9 wt.%. The low surface area of the support, calcination temperature and the percentage of vanadia loading are found to influence the formation of higher vanadia species. The catalytic activity of the V2O5-NA(2)O(3) catalysts was probed in the liquid phase hydroxylation of phenol and the result show that the present catalysts are active at lower vanadia concentrations. (c) 2005 Elsevier B.V. All rights reserved.