Thermodynamic analysis for esterification of abietic acid with methanol by group-contribution method

The esterification of abietic acid with methanol was selected as a probe reaction.The thermodynamics of reaction was analyzed by group-contribution method.The reaction enthalpy,entropy,Gibbs free energy and equilibrium constant were calculated in the temperature range of 473—653 K and the pressure range of 0.1—20 MPa.The effects of temperature and pressure on the reaction were also discussed.The calculation indicates that the reaction enthalpy is-46.31—-10.10 kJ·mol-1 and free energy is-53.26—-25.49 kJ·mol-1,showing an exothermic and spontaneous reaction.The equilibrium constant is 136.32—748.89 at standard pressure and(1.1×104)—(3.2×104) in the range of 5—20 MPa.The experimental results show the conversion of abietic acid of 85.94%—94.89% and 73.80%—81.20% without catalyst in super/subcritical methanol,which is in agreement with thermodynamic calculation by the group-contribution method.