A series of rare-earth neodymia supported vanadium oxide catalysts with various V205 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 hy 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 desorprion of ammonia (NH3-TPD) and found that
the total acidity gets increased with the percentage of vanadia loading. XRD and FT1R 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 V205-Nd203 catalysts was probed in the liquid phase hydroxylation of phenol and the
result show that the present catalysts are active at lower vanadia concentrations.
Manju, Kurian; Sugunan, S(Elsevier, January , 2006)
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Abstract:
Wet peroxide oxidation (WPO) of phenol is an effective means for the production of diphenols, which are of great industrial importance. An added advantage of this method is the removal of phenol from wastewater effluents. Hydroxylation of phenol occurs efficiently over mixed iron aluminium pillared montmorillonites. An initial induction period is noticed in all cases. A thorough study on the reaction variables suggests free radical mechanism for the reaction.