Acetalization of aldehydes and ketones over H4[SiW12O40] and H4[SiW12O40]/SiO2?

Catalysis Science & Technology Pub Date: 2014-04-08 DOI: 10.1039/C4CY00021H

Abstract

H4[SiW12O40] (H-SiW12) is demonstrated to be able to efficiently catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol. Nevertheless, the possible leaching and the recycling of H-SiW12 are two major disadvantages that largely restrict its further application in industry. Moreover, H4[SiW12O40] tends to deactivate strong proton sites due to the small surface area of 10 m2 g?1. Due to interactions with surface silanol groups, the proton sites of polyoxometalates (POMs) on SiO2 are less susceptible to deactivation. As such, immobilization of H4[SiW12O40] onto SiO2 leads to the heterogeneous catalyst H4[SiW12O40]/SiO2 (H-SiW12/SiO2), which can catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol selectively and efficiently without the need of a drying agent. The acetalization process can proceed smoothly at a relatively low temperature under solvent-free conditions. The catalyst of H4[SiW12O40]/SiO2 can be recycled at least ten times without an obvious decrease in its catalytic activity. As far as we know, the TONs of the H-SiW12/SiO2-catalyzed acetalization of cyclohexanone with ethylene glycol, and benzaldehyde with 1,3-propanediol are the highest reported so far.

Graphical abstract: Acetalization of aldehydes and ketones over H4[SiW12O40] and H4[SiW12O40]/SiO2
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