Adsorption and reaction in the transesterification of ethyl acetate with methanol on Lewatit K1221

The reaction kinetics of the liquid-phase transesterification of ethyl acetate with methanol to methyl acetate and ethanol have been investigated in a temperature range from 303.15 K to 333.15 K as a model reaction for the transesterification of triglycerides in the production of biodiesel. The reaction has been catalyzed by the acidic ion-exchange resin Lewatit K1221. The effect of the initial reactant molar ratio and the temperature on the reaction kinetics was investigated and kinetic models, based on pseudo-homogeneous (PH), Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms, were used to describe the reaction rate. Because of the pronounced non-ideality of the reaction mixture, the kinetics were expressed in terms of activities. Additional experiments, based on a D-optimum design of experiments, were performed to obtain more precise parameter estimates as required for final model discrimination. The kinetic model with the surface reaction of adsorbed methanol with ethyl acetate from the bulk as the rate-determining step according to an Eley–Rideal mechanism was found to best describe the observed kinetics. The corresponding rate equation agrees with a reaction mechanism in which physically adsorbed methanol reacts with protonated ethyl acetate.

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► Alcohol physisorption is most prominent in transesterification on ion-exchange resins.
► Eley–Rideal kinetics occur with alcohol adsorption and rate-determining surface reaction.
► The ester is protonated and reacts with teh alcohol after a prior physisorption.