Esterification of Glycerol with Acetic Acid over Highly Active and Stable Alumina-based Catalysts: A Reaction Kinetics Study

S. A. Rane, S. M. Pudi and P. Biswas

Abstract
The catalytic activity of Cu- or Ni monometallic and Cu-Ni bimetallic (Cu/Ni ratio = 3, 1, 0.33) catalysts supported on γ-Al2O3 and SO42–/γ-Al2O3 catalysts were evaluated for esterification of glycerol. The reactions were performed in a batch reactor under reflux at standard reaction conditions: temperature 110 °C, atmospheric pressure, glycerol to acetic acid molar ratio 1:9, and catalyst loading 0.25 g. The best catalytic activitywas observed over 2 M SO42–/γ-Al2O3 catalyst, which showed the glycerol conversion of 97 % within 2 hours of reaction. At this condition, the selectivity to glyceryl monoacetate (MAG), glyceryl diacetate (DAG), and glyceryl triacetate (TAG) were 27.0%, 49.9 % and 23.1 %, respectively, after 5 h of reaction. After three consecutive runs, the 2 M SO42–/γ-Al2O3 catalysts showed superior performance and no loss in activity was observed. The reaction kinetics results over 2 M SO42–/γ-Al2O3 catalyst showed that the dependence on the reaction rate to glycerol concentration was of pseudo-second order, while the activation energy was found to be 106 kJ mol–1.

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Keywords
glycerol esterification, Cu-Ni bimetallic catalysts, SO42–/γ-Al2O3 catalyst, stability, DAG and TAG selectivity