Kinetics of the Esterification Reaction of Adipic Acid with 1,6-Hexanediol Catalyzed by Tetrabutyl Titanate

In this paper, the esterification reaction for a batch reactor between adipic acid (AA) and 1,6-hexanediol (1,6-HD) catalyzed by tetrabutyl titanate (Ti(OBu)4) was studied in the temperature range of 413-443 K. A kinetic model based on the assumption of 3.5-order reaction was proposed to describe the variation of carboxyl group concentration with time. The kinetic data demonstrated that the model was suitable to the esterification reaction. The rate constant was obtained through global optimization method-genetic algorithm procedure and the activation energy ( Ea = 80.16 ± 4.41)kJ/mol) of the esterification reaction was calculated through the Arrhenius equation. The effects of initial 1,6-HD/AA molar ratio (α) and the amount of catalyst on the esterification was also investigated. The results showed that (i) the conversion of carboxyl group increases obviously when the α value increases from 1.1 to 1.2, but it does not change much when the α value is larger than 1.2; and (ii) the rate constant of the esterification increases with the concentration of Ti(OBu)4 in the range of 0.36-5.66 mmol/kg.