Abstract：The synthesis of dioctyl phthalate (DOP) involves mono-(2-ethylhexyl) phthalate (MEHP) formation firstly by phthalic anhydride (PA) with 2-ethyl hexanol (2-EH) and further esterification between MEHP and 2-EH to generate DOP, and the second reaction is reversible and the controlling step. Since MEHP conversion is usually demanded to be over 99.5%, the influence of DOP hydrolysis cannot be neglected. The thermodynamic properties were calculated by Benson, Ducros and Ruzicka-Domalski group contribution methods. The vapor-liquid equilibrium composition and reaction equilibrium constants of the controlling reaction as well as the kinetics with tetrabutyl titanate as catalyst were investigated experimentally in batch reactor. The result of thermodynamic experiments showed that the enthalpy and entropy of the reaction between MEHP and 2-EH were 17.91 kJ/mol and 54.64 J/(K·mol) respectively, and this reaction was endothermic with increasing entropy which was consistent with the theoretical calculation result. The activity coefficient of water and 2-EH in this reactive system was fitted well using Redlich-Kister equation. The kinetic model of reversible reaction between MEHP and 2-EH was established, both the forward and backward reaction can be treated as second-order reactions, and parameter regression showed that the activation energy and pre-exponential factor of the forward reaction were 83.49 kJ/mol and 1.75×107kg/(mol·min) respectively.
