An efficient two-phase reaction of ethyl acetate production in modified ZSM-5 zeolites

Most of the commercial processes for ethyl acetate (EAc) production are via liquid-phase esterification. Owing to the thermodynamic limitations, the overall yields of EAc are confined to 67% with equimolar reactant feeds of acetic acid and ethanol. The reactions were conducted at 363-400 K, with molar ratio of ethanol/acetic acid = 1.5 and with LHSV = 1 h(-1). One of the critical parameters in this novel EAc synthesis process is the reaction (esterification) temperature. It was kept between the liquid- and gas-phase operation regimes at which some 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, both the equilibrium conversion constraint for the liquid-phase regime and the larger reactor volume requirement for the gas-phase reaction has been overcome. In this study, the one-pass ethanol conversion was successfully improved from 67 to 85 mol%. In addition, the solid acid catalysts used in this novel process have low impact to the environment and cause no corrosion to the reactor wall. These catalysts had continued performance for 2200h. Evaluation also shows that half of the process water and one-third of the consumption of purification steam can be saved. (C) 2003 Elsevier B.V. All rights reserved.