Surface and catalytic properties of V2O5-TiO2/SO42- catalysts for the oxidation of methanol prepared by various methods

The influence of the preparation method on the surface and catalytic properties of sulfated vanadia-titania catalysts has been studied. V2O5-TiO2/SO42- (VTiS) catalysts with 25 wt% V2O5 and 0.2-6.5 wt% S were prepared by co-precipitation, sol-gel and mechanical grinding methods and calcined at 723 K in air. The structural properties were characterized by O-2 chemisorption and laser Raman spectroscopy (LRS). The surface acidity was determined by the techniques of NH3 adsorption microcalorimetry and pyridine adsorption infrared spectroscopy (FT-IR). Catalytic tests of oxidation of methanol to dimethoxymethane (DMM) were performed at atmospheric pressure in a fixed-bed micro-reactor. The Raman spectra revealed that vanadia existed in the form of a crystalline V2O5 phase. The results of ammonia adsorption of microcalorimetry showed a much lower heat of adsorption for samples with high content of SO42-. Meanwhile, pyridine adsorption of FT-IR showed that both Lewis and Bransted acid sites were present on the surface of all VTiS catalysts. The catalytic performance was also influenced by the preparation methods. VTiS-CP catalyst, prepared by co-precipitation, exhibited the highest DMM yield with a DMM selectivity of 86% for 61% methanol conversion at 423 K. (C) 2009 Elsevier B.V. All rights reserved.