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

Spherical, irregular and gyroidal MCM-41 were used for the deposition of VOx 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 N2 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.