Tungstophosphoric heteropolyacid supported onto neutral alumina: characterization and synthesis of acetals and ketals

Tungstophosphoric acid (HPW) catalyst supported on the neural alumina was studied. It was prepared by means of an equilibrium and incipient wetness impregnation technique. Solution of HPW in 50% V/V ethanol-water was used to impregnate Al2O3 at 25°C. It was found that the catalyst containing 30% PW by calcination at 500°C showed a higher catalytic activity in the synthesis of acetals and/or ketals. In the following condition, that is, the molar ratio of aldehyde/ketone to glycol being 1:1.5, the mass fraction of the catalyst used was 0.5%, and the reaction time was 1.0 h; the yields of ketals and acetals could reach up to 60.5%-86.7%. Moreover, it could be easily recovered and reused.