Synthesis of terpinyl acetate by lipase-catalyzed esterification in supercritical carbon dioxide

Terpinyl acetate was successfully synthesized from α-terpineol and acetic anhydride in supercritical carbon dioxide (SC-CO2) by enzymatic catalysis. Five different lipases (Candida rugosa type VII, Amano PS, Amano AP-6, Amano G and Lipozyme RM IM) as biocatalysts for the terpinyl acetate synthesis were compared. An esterification extent of 53.0% was obtained in continuous operation using acetic anhydride as acyl donor and C. rugosa lipase as enzyme at 10 MPa and 50 °C for 1.5 h. Temperature in the range of 35–50 °C demonstrated that the yield of terpinyl acetate increase with temperature increase in the current study. Operating at a α-terpineol/acetic anhydride molar ratio 3.0, the conversion of alcohol decreased, probably due to an inhibitory effect on enzyme by high concentration of acetic anhydride or by formation of acetic acid. However, the enzyme activity still remained more than 50% after 10.5 h repeated esterification in a batch under optimized conditions.