Synthesis of Hf/SBA-15 Lewis acid catalyst for converting glycerol to value-added chemicals

Hf/SBA-15 catalyst containing highly ordered two-dimensional hexagonal mesoporous silica with a large surface area is prepared in a facile one-step sol–gel method with hafnia content ranging from 2.5 to 10%. The synthesized catalyst is characterized by X-ray diffraction analysis, N2 adsorption–desorption isotherm, scanning electron microscope and transmission electron microscope. The oxidation state and Lewis acidic properties of 10% Hf/SBA-15 are investigated by diffuse reflectance UV–Vis technique, X-ray photoelectron spectroscopy and pyridine-adsorbed FT-IR analysis. The catalytic activity of Hf/SBA-15 is employed in the acetalization of glycerol with acetophenone and benzaldehyde, order of activity of the catalyst is 10 > 5 > 2.5% Hf/SBA-15. The 10% Hf/SBA-15 is given 43 and 21% selectivity of six-membered (1,3-dioxane) and five-membered (1,3-dioxolane) acetals. Hence, this catalyst is further exploited in the acetalization of glycerol with substituted acetophenone and benzaldehyde. The catalyst could be recycled for five times without a significant decrease in activity.