Gel Resin Supported Ionic Liquids as Solid Acids for Esterification Reaction

In response to the problem that the conventional concentrated sulfuric acid catalyst for esterification reactions are prone to corrosion and generate large amounts of acid-containing wastewater, highly efficient gel resin-loaded ionic liquid solid acid (SA-ILs) catalysts were prepared by a one-pot method of loading ionic liquids onto gel resins. It is shown that the gel resin carrier has a strong water-absorbing structure, and the ionic liquids are covalently loaded on the gel resin carrier through chemical bonding, leading to SA-ILs catalysts with excellent acidity and good structural stability. With an optimal ionic liquid loading of 11% and acid density of 3.25 mmol·g −1 ,the synthesized SA-ILs catalysts showed good catalytic performance in the transesterification reaction between acetic acid and ethanol at 80 °C for 1.5 h. The catalyst dosage was 10 wt% of the total mass of acetic acid and ethanol, and the ethanol to acetic acid addition was at a molar ratio of 1.5:1. Ethyl acetate yields of up to 81% were achieved after the reaction. The catalyst also showed slightly decrease of the catalytic performance after reused for five cycles. The lower activation energy of the catalyst is proved to be the key to facilitate the catalytic transesterification reaction. Graphical Abstract