Metallocene-derived, isolated MoVI active centres on mesoporous silica for the catalytic dehydrogenation of methanol

Abstract

Isolated Mo^VI active sites have been grafted onto the inner surfaces of MCM-41 mesoporous silica via a molybdocene dichloride precursor, to generate a catalyst which has been tested for the oxidative dehydrogenation of methanol. Mo K-edge X-ray absorption spectroscopy shows that, after calcination, at low Mo loadings (ca. 1 mol% with respect to SiO₂), isolated MoO₄ species are generated on the surface, whereas at higher loadings (ca. 4 mol%) there is some evidence for the formation of polymeric oxo-molybdenum species. Catalysis tests show that lower Mo loadings on the MCM-41 silica lead to higher selectivity for the production of formaldehyde, in contrast to the results of previous studies of isolated Mo species on pure silica, which report that methyl formate is the major product.