Several mesoporous TaxW10-x mixed oxides prepared from TaCl5 and WCl6 in the presence of poly block copolymer surfactant Pluronic P-123 were examined as potential solid acid catalysts. Amorphous wormhole-type mesopores were observed in samples with x values from 3 to 10, whereas W-rich samples (x = 0-2) formed nonmesoporous structures with crystallized tungsten oxide (WO3). The acid strength increased with addition of W for mesoporous TaxW10-x oxides, and mesoporous Ta3W7 oxide exhibited the highest acid catalytic activity for the Friedel-Crafts alkylation of anisole and the hydrolysis of disaccharides. The results are compared with those of nonporous Ta2O5-WO3, HTaWO6 nanosheets, which were a solid acid obtained by exfoliation and aggregation of layered HTaWO 6 with strong Brønsted acid sites in the interlayer, and a range of conventional solid acid catalysts. Mesoporous Ta-W oxides exhibited a turnover rate higher than that of nonporous Ta2O5-WO 3 and HTaWO6 nanosheets, indicating that the mesoporous structure is an advantageous environment for the strong acid sites, because of the high surface area and easy reactant accessibility.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry