Ultrasound-assisted acetylation of glycerol for triacetin production over green catalyst: A liquid biofuel candidate

Abstract

Upgrading of crude glycerol to high value-added chemical products is an attractive process in biomass conversion and biorefinery industry. In this work, production of triacetin (TAG) from direct conversion of glycerol with acetic acid over SO3H-glycerol-carbon catalyst assisted with ultrasound was investigated for the first time. The catalyst was synthesized from glycerol via in-situ carbonization and sulfonation. The significant factors for TAG production obtained from 2 k factorial design were in the order of reaction temperature > ultrasonic power > reaction time. The TAG selectivity (100%) was successfully achieved in mild conditions. Kinetic studies indicated that ultrasound-assisted acetylation reaction followed first-order reaction while an activation energy of 51.08 kJ/mol was obtained. For comparison between as-synthesized catalyst with various commercial solid acid catalysts, the glycerol conversion turnover rate toward TAG was considerably highest on SO3H-glycerol-carbon with the rates exhibited in the order of SO3H-glycerol-carbon > Amberlyst-35 > H-USY > SiO₂-Tosic acid > Al2O3. The SO3H-glycerol-carbon also exhibited excellent reusability for 10 consecutive cycles without any decreasing in glycerol conversion and TAG selectivity after regeneration process was carried out. The obtained results indicated that the contribution of catalyst acidity with ultrasonic power was responsible for determining TAG selectivity.