Influence of acidic properties of different solid acid catalysts for glycerol acetylation

Abstract

The glycerol esterification with acetic acid is studied in this work using propylsulfonic functionalized mesoporous silica (Pr-SO3H-SBA-15), and compared with H-ZSM-5 and H-Beta zeolites. The reaction was carried out in a batch reactor using a 6:1 molar ratio of acetic acid to glycerol. The initial TOF for the glycerol conversion was significantly higher in the propylsulfonic mesoporous silica, as compared to the two zeolites. These two catalysts have acid sites densities (μmolm−2) that are less than half than that displayed by the SBA-based catalyst. It was possible to obtain 96% conversion in 2.5h, with 87% selectivity to the products of interest diacetylglycerol (DAG) + triacetylglycerol (TAG), being the ratio DAG/TAG=1.7. The catalyst deactivates partly due to sulfonic groups loss and to coke deposition during the reaction, as observed when it was used in a second reaction cycle without any treatment in between cycles. The catalyst lost activity, but maintained the selectivity, associated to a non-selective site poisoning.