Immobilized lipase-catalyzed esterification for synthesis of trimethylolpropane triester as a biolubricant

Synthetic oleochemical esters of polyols and fatty acids are biodegradable and possess desirable technical and ecological properties. Trimethylolpropane (TMP) triester has been widely applied as a hydraulic fluid. TMP triester was effectively synthesized by lipase-catalyzed esterification from TMP and high oleic fatty acid from palm oil using an immobilized lipase. The immobilized lipase was prepared with liquid Lipozyme TL 100 L from Thermomyces lanuginosus with Duolite A568 as a carrier. The effects of temperature, enzyme loading, vacuum level, and water activity of the enzyme on the synthesis of TMP triester were investigated. The optimum temperature, enzyme loading, and vacuum level were 60 °C, 15% (based on total substrate), and 6.7 kPa, respectively. The optimum water activity range of the enzyme was 0.5-0.9. Under the optimum conditions, the maximum conversion reached up to 95% after 9 h. No significant differences in physical properties were observed between TMP triester from this study and a commercial TMP triester prepared by chemical catalyst.