Kinetics of the bulk reaction between terephthalic acid (TPA) and ethylene oxide (EO) was studied under high pressure. Tertiaryamine, especially, triethylamine was used as a catalyst throughout the experiments.
The effects of stirring speed and particle size on the yield of Bis (2-hydroxylethyl) terephthalate (BHET) were experimentally investigated. It was found that stirring speed and particle size had no effects on the yield of BHET and reaction rates. On the basis of these findings, it was concluded that the reaction occurred only in the liquid phase. Also the effects of the pK-value of tertiary amines were investigated on reaction rates and the yield of BHET. It was shown that the pK-value of amines crucially affected the yield of BHET and reaction rates. Based on these results, a reaction mechanism of the synthesis of BHET from TPA and EO in solvent free system was proposed.
The effects of EO/TPA mol-ratio and the amounts of catalyst on the yield of BHET and reaction rates was studied experimentally. The results were consistent with the proposed reaction mechanism.
Rate constants were obtained from experimental data, and the value of $k_1$ and $k_2$ at the temperature of 90℃ from the model were found to be 0.04499 (mol/kg. min), 3.30693(mol/kg.min), respectively. The activation energy of the reaction was found to be 8.28 (kcal/mol) from $k_1$.
