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An assessment of the minimum requirements for a countercurrent multistage extractive reaction process for the enzymatic hydrolysis of methyl octanoate with immobilized lipase in undiluted media was made. For simulation, UNIQUAC parameters for the quaternary reaction system containing methyl octanoate, octanoic acid, methanol, and water at 48.5 °C and atmospheric pressure and the equilibrium conversion, as a function of the initial water content, were determined. For a one-equilibrium stage reaction, good overall agreement, with respect to the liquid-phase compositions between experiments, and results from chemical and phase equilibrium calculations, based on Gibbs free-energy minimization, was obtained. A subsequently performed analysis of the influence of the stage number and solvent:feed ratio, using commercial flowsheet simulation software, showed that, in a countercurrent process, five equilibrium stages are required to obtain octanoic acid with a purity exceeding mass fractions of 0.95 at comparably moderate water excess.

The esterification of benzoic acid with n-hexanol, n-octanol, 2-ethyl hexanol and n-decanol was investigated in detail. An analysis of the reaction kinetics of esterification in the presence of different commercially available chemical catalysts was carried out. The effects of catalyst type and loading on the reaction rate were studied. Although the considered reaction is bimolecular, it showed a first-order behavior, and a linear dependence with respect to the catalyst concentration was observed. Hence, a new approach is presented to describe the reaction kinetics accurately over a wide range. The application of biotechnological synthesis applying different enzymes as catalysts offers an interesting alternative besides chemical synthesis. Especially an esterase from Bacillus subtilis immobilized on Sepabeads EC-EP showed high stability and was applied for 2 days in the synthesis of hexyl benzoate. Nevertheless, the chemical reaction route remains superior with respect to the catalyst activities under the applied conditions, which were 25 kU/g for the chemical reaction and 0.7 kU/g for the best enzymatic conversion.

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