Acidic catalysis of microporous polyoxometalate H3PW12O40/SiO2 in acetal reaction between benzaldehyde and ethylene glycol

Microporous Keggin-type polyoxometalate material was synthesised by supporting H3PW12O40 into a silica matrix via a sol-gel technique. The silica-supported 12-tungstophosphoric acid ( H3PW12O40/SiO2) obtained is insoluble and readily separable porous materials with uniform micropores (0.57 nm) and a high specific surface area (350.5 m(2)/g) in oxygen-containing polar solvents. H3PW12O40/SiO2 was characterized by infrared spectrophotometer (IR), ultraviolet-visible spectrophotometer (UV-vis), inductively coupled plasma (ICP), thermogravimetric analysis (TGA) and Brunner-Emmett-Teller method (BET) measurements. H3PW12O40/SiO2 obtained catalyzed the acetal reaction between benzaldehyde and ethylene glycol to produce 2-phenyl-1, 3-dioxolane more efficiently than the typical solid acids such as SO42- /ZrO2, Nafion-H and H-ZSM-5. Conversion was 93.8 % for benzaldehyde during the reaction period of 2 h. H3PW12O40/SiO2 kept its initial activity during three times of reuse. The initial acetal reaction follows a second-order kinetics model at 298 K.