Esterification of Sebacic Acid in Near-Critical and Supercritical Methanol

Diesters of sebacic acid find various applications as plasticizers, solvents, and lubricants. Noncatalytic esterification of dibasic acids under near-critical and supercritical alcohol conditions was conducted for the first time. Esterification of sebacic acid (decanedioic acid) and methanol was chosen as a candidate reaction. The effect of molar ratio of methanol to sebacic acid, temperature, addition of water, and pressure was studied on the yields of the diesters and monoesters. A maximum molar yield of 87% with a selectivity of 16 between monoester and diester was obtained at 623 K with a molar ratio of 5:1 within a reaction time of 25 min. A kinetic model was developed to correlate the experimental data, and activation energies were computed using the Arrhenius equation. The effects of addition of water and pressure on the yield and selectivity show that esterification is fairly water resistant and could be carried out at operating pressures much lower than the critical pressure of methanol.