Preparation of a coal tar pitch-based solid acid catalyst and its esterification activity in ethyl acetate production

In this work, carbon-based solid acid catalysts have been prepared by a series of treatments for coal tar pitch (CTP). The modified coal tar pitch (MCTP) modified with trichloroacetic acid was sulfonated by concentrated sulfuric acid. An orthogonal array design was used to optimize the preparation conditions. The catalyst from MCTP had a higher acid density than from CTP. It possessed an acid site density of 7.01 mmol g−1 under the optimum conditions (sulfonation temperature of 155 °C, reaction time of 12 h and sulfuric acid/MCTP mass ratio of 3:1). FT-IR spectroscopy was used for structural analysis. The elemental composition and acid site density for the solid acid were analyzed by elemental analyzer and volumetric titration, respectively. The catalytic ability of the solid acid was observed through the esterification reaction of ethyl acetate. The results showed that the yield of ethyl acetate with 86.67 wt% was obtained under the best conditions of the single factor tests (reaction time of 60 min, ethanol/ethanoic acid mass ratio of 3:1, catalyst dosage of 5 wt%). The catalysts retained satisfactory catalytic activity for esterification of ethyl acetate after five catalytic cycles.