MIXED OXIDES DERIVED FROM VANADIUM SUBSTITUTED LAYERED DOUBLE HYDROXIDES AS CATALYSTS PRECURSORS FOR SO2 OXIDATION

Abstract

Layered double hydroxides in which aluminum was partially substituted by vanadium in the hydrotalcite-like layer were synthesized by a coprecipitation method.The effects of the substitution on the physicochemical properties of the samples were studied by using various techniques such as: X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS).After the thermal treatment the resulted mixed oxides were tested, for the first time, as catalysts for the process of SO 2 oxidation.The XPS results show that vanadium exists on the surface as a mixture of V 3+ and V 5+ but the surface vanadium is consumed during the catalytic process.XRD results point the formation of V 2 O 5 , vanadium containing mixed oxides and also the formation of a spinel phase, after calcinations at 1073 K for 5 hours.A direct correlation was obtained between the vanadium content of the samples and their catalytic activity: for a temperature value equal by 723 K a molar conversion of 85% was obtained for the sample containing 2.1% vanadium surface coverage.