Catalytic acetylation of glycerol with acetic anhydride

We studied the acetylation of glycerol with acetic anhydride using different solid acid catalysts. The results indicated that at 60 °C, zeolite Beta and K-10 Montmorillonite showed 100% selectivity to triacetin within 20 min, with a molar ratio of 4:1. Amberlyst-15 acid resin yielded 100% triacetin after 80 min, whereas niobium phosphate gave diacetin and triacetin in 53% and 47% selectivity, respectively. All catalysts were more selective to triacetin than the uncatalyzed reaction. By contrast, zeolite Beta gave poor yield of triacetin when acetic acid was used as acetylating agent. The different behavior was explained in terms of the stabilization of the acylium ion intermediate.