Efficient Catalytic Processes for the Preparation of Ethyl Acetate

• Main Authors: Kuo-Ching Wu, 吳國卿
• Other Authors: Yu-Wen Chen
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/78816145192868615861

博士 === 國立中央大學 === 化學工程與材料工程研究所 === 92 === Ethyl acetate (EAc) is an important feedstock in chemical industry. Most of the commercial processes for EAc production are via liquid-phase esterification. Owing to the thermodynamics limitation, the overall yields of EAc are confined to 67% with equimolar reactants feed of acetic acid and ethanol. Consequently, there are 30% of unreacted reactants with azeotropic by-products of ethanol-water, ethanol-EAc and ethanol-water-EAc. To separate these impurities is laborious and energy consuming. Over 90% of overall energy supply of EAc production is consumed by the separation of ethanol-water-EAc azeotropes. The key factor is ethanol. Owing to its difficulty in separating by direct distillation, the most plausible way is water extraction to reduce the ethanol content in EAc followed by azeotropic distillation for purification. In order to improve the EAc distillation process, a high-efficiency, low energy-consuming esterification process has been developed. In this study, the one-pass ethanol conversion was successfully improved from 67mol.% to 85mol.% while the ethanol concentration was decreased from 14wt.% to 6.5wt% without changing the flow sheet of traditional esterification process. One of the critical parameters in this novel EAc synthesis process is the reaction (esterification) temperature. By keeping it between the liquid-phase and gas-phase operation regimes during which parts of the reacting composition were vaporized. The major consideration is based on the equilibrium constants in the gas-phase reaction which are higher than those in the liquid-phase. The initial reaction stage in the liquid-phase has the advantage of smaller reactor size and more efficient contacting with the catalysts. As the equilibrium had been achieved in the final gas-phase, a higher conversion of ethanol was obtained due to the equilibrium constant constraints. Consequently, either of the equilibrium conversion constraint for the liquid-phase regime and larger reactor volume requirement for the gas-phase reaction has been overcome. In addition, the solid acid catalysts used in this novel process has low impact to the environment without corrosion to the reactor wall. These catalysts had been passed for performance after 2200 h of duration. Evaluation also shows that half of the process water and one-third of consumption of purification steam can be saved