Mesoporous alumina catalytic material prepared by grafting wide-pore MCM-41 with an alumina multilayer

An alumina multilayer grafted on the surface of MCM-41 produced a mesoporous material with the surface chemical functionality of alumina. The starting MCM-41 material (WPMCM) with a wide pore size distribution, a surface area of 858 m²/g, an average pore diameter of 8.2 nm and a pore volume of 1.75 cm³/g was synthesized by expanding the cetyltrimethylammonium chloride (CTAC) surfactant micelles with mesitylene at a high solubilizant/CTAC ratio of 10. Successive grafting consisting of aluminum butoxide anchoring followed by hydrolysis and calcination steps yielded a gradual increase of the aluminum content in WPMCM. Tetrahedral Al in the silica pore walls and clusters of a separate octahedral Al alumina phase were identified. Four grafting cycles produced a material with a surface area of 542 m²/g and a mean pore diameter of 4nm containing 38 wt.% Al₂O₃ that displayed chemical surface functionality of pure alumina. The activity of this material in the alkylation of phenol with methanol was 2.3 times higher than the activity of a reference alumina (460 m²/g). The highest activity of grafted alumina in cumene cracking and isopropanol dehydration was achieved at 21 wt.% Al₂O₃. Independent measurements of surface charging in aqueous solution, of [Mo₇O₂₄]^6- anions adsorption and of surface acidity indicated that the material grafted with alumina and the reference alumina display similar chemical functionality.