Synthesis of citronella acetate by lipase catalyzed transesterification in ionic liquid and its kinetics

Abstract

In this paper, the lipase catalyzed transesterification of citronellol with vinyl acetate was investigated in ionic liquid. Firstly, six kinds of ionic liquids and six kinds of lipases from different sources were screened. The results showed that the lipase from Pseudomonas fluorescens had the best catalytic effect in the ionic liquid [bmimn][TF2]. The factors affecting the transesterification were optimized, and the optimal reaction conditions were as follows: the molar ratio of vinyl acetate to citronellol was 3:1; the reaction temperature was 40 °C; the amount of enzyme was 10 mg/mL; the rotating speed of the shaker was 200 r/min. When the concentration of substrate was below 500 mmol/L, no inhibition of substrate was found, while the inhibition of product was not negligible. The reuse of the lipase was studied, and the results showed that the catalytic activity of the lipase decreased by 20% after 7 times. The kinetic study showed that the reaction was a ping-pong bi-bi reaction mechanism with the inhibition of citronellyl acetate. The reaction kinetics model was established, and the parameters of the model were fitted by MATLAB software. The fitting values and the experimental values were in good agreement, and the relative error was only 7.75%.

Keywords:
citronellyl acetate; lipase; ionic liquid; transesterification; kinetics