Kinetic analysis of acetic acid and ethanol esterification catalyzed by ionic liquids

Concentrated sulfuric acid as catalyst has problems including corrosion and unable to recover. 1-sulfonate butyl -2- methyl pyridine bisulfate ionic liquid was used as a catalyst in this study, and its effects on kinetic properties in the synthesis of ethyl acetate via acetic acid and ethanol esterification was investigated. The impact of factors on reaction conversion was investigated under the conditions of temperature 313.15-333.15 K, catalyst concentration 0.07-0.27 mol∙L-1 and acid-alcohol molar ratio 0.56-1.5. The non-ideal homogeneous (NIH) model of kinetics was established based on the two-stage reversible reaction mechanism, and the NRTL activity equation was adopted to correlate the non-ideal properties of the mixed liquid. Parameters such as kinetic constants, reaction activation energy and pre-exponential factors in the model were obtained by fitting kinetic data. The results show that the reaction rate increased gradually with the increase of temperature and concentration of ionic liquid catalyst, but the equilibrium conversion stayed unchanged and the highest conversion was obtained with molar ratio of acid to alcohol = 1. The positive reaction activation energy was 49.48 kJ•mol-1 and the negative reaction activation energy was 53.78 kJ∙mol-1. The positive predigital factor was 7.25×105 L2∙mol-2∙min-1 and the negative predigital factor was 3.87×105 L2∙mol-2∙min-1. The predicted values of the model were consistent with the experimental values, which indicates that the NIH model is suitable for the kinetic study. © 2021, Editorial Board of "Journal of Chemical Engineering of Chinese Universities". All right reserved.