Influence of the MCM-41 morphology on the vanadia deposition by a molecular designed dispersion method

Abstract

Spherical, irregular and gyroidal MCM-41 were used for the deposition of VO x by the molecular designed dispersion method (MDD), in liquid phase, using vanadyl acetylacetonate. The molecular designed dispersion method using metal complexes on a highly porous support is a suitable method to prepare high quality catalysts. Deposition of VO(acac) 2 was carried out at room temperature and with a decreasing temperature gradient. The porous characteristics and coordination environment of the supported vanadium oxide was studied by a combination of different techniques such as N 2 adsorption/desorption, FT-Raman and FTIR-PAS. The results show that vanadia is present at the surface of the pore walls. Different morphologies of the support materials has no influence on the reaction mechanism for the VO(acac) 2 deposition. However, the vanadium loading is significantly influenced by the morphologies of the support. The spherical MCM-41 gives the highest loading of vanadium, although it has a smaller surface area, pore volume and pore diameter than irregular and gyroidal MCM-41. Dye adsorption experiments prove that MCM-41 with various morphologies have different accessibilities, which is also related to differences in the vanadium loadings.