Synthesis, characterization and activity of magnesium phosphate supported V2O5 catalysts for SO2 oxidation
M. Sadiq1, A. Sahibed-dine1, M. Baalala1, M. Bensitel1*, C. Lamonier2, E. Payen2, J. Leglise3
1 Laboratoire de Catalyse et Corrosion des Matériaux, Université Chouaib Doukkali,
Faculté des Sciences d’El Jadida, B.P. 20, El Jadida 24000 Morocco.
2 Laboratoire de Catalyse, UMR.CNRS.8010, Université de Lille 1, 59650 Villeneuve d’Ascq. Lille, France.
3 DRRT, 2 rue Grenet Tellier, 51038 Châlons en Champagne, France.
* Corresponding author. E-mail: email@example.com
Received: 14 September 2006; revised version accepted: 26 July 2007
A series of vanadium oxide catalysts with V2O5 loading ranging from 3 to 12 wt.%, have been prepared by impregnating a magnesium phosphate Mg3(PO4)2 support synthesized by coprecipitation. The solids obtained were investigated as-synthesized or after calcination by various physicochemical techniques. Using N2 adsorption, the catalyst specific surface area was found to decrease with the increase in vanadium content. The decrease was bigger than expected by diluting the porous MgP support with bulk V2O5. TPR profiles of catalysts exhibit only a single peak at low vanadium content. It’s due to the reduction of surface vanadia. UV-Vis diffusion reflectance spectroscopy was used to determine the nature and coordination of surface species. Vanadium ions preferentially exist on the support surface as isolated tetrahedrally coordinated (VO4). From X-ray diffraction, the solids appeared to be mostly amorphous with part of a crystalline V2O5 phase that was revealed at high vanadia loading. These results were confirmed by IR spectroscopy. The oxidation SO2 to SO3 in the gas phase at 673-773 K was used as test reaction. The catalyst with the highest V2O5 content was found to be the most active.
Keywords: magnesium phosphate, Mg3(PO4)2, supported vanadia catalysts, SO2 oxidation, characterization by DRX, FTIR, BET, TPR, UV-Vis.