Physicochemical and catalytic properties of grafted vanadium species on different mesoporous silicas

Vanadium modified mesoporous silicas type MCM-41, MCM-48, and SBA-15 are obtained by a solid state method. The samples are characterized and compared at the different steps of their preparation by X-ray diffraction, N2-physisorption, FTIR, UV–vis, XPS, and TG-TPR. Samples catalytic activity is tested in ethylacetate oxidation. Formation of various vanadium species, mainly isolated and small oligomeric ones, grafted to the support surface silanol groups, is observed. It is found that the state and the properties of the vanadium species depend on the porous characteristics of the silica host matrix. The nature of the catalytic active center in the ethylacetate oxidation is discussed.

Isolated and small oligomeric vanadium species are prepared by a solid state reduction technique from V2O5 and mesoporous silica of types MCM-41, MCM-48, and SBA-15. The reduction usually leads to increase in the catalytic activity and selectivity to partial ethylacetate oxidation. It was hypothesis on the key role of the oligomeric catalytic active centers, containing vanadium species in a mixed valence, which formation is facilitated for the more opened 3-D structure of MCM-48.Figure optionsDownload as PowerPoint slide