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Abstract: The lubricants of the future have to be more environmentally adapted, have a higher level of performance. Synthesis esters (SEs) which can be used as raw materials for biodegradable lubricant base oils are increasing in popularity due to superior technical properties. Direct esterification of trimethylolpropane (TMP) with fatty acid in a solvent free system, by immobilized lipase from Candida sp. 99–125 was studied. Investigations of important factors were carried out involving temperature, time, enzyme amount, substrates molar ratio and water content. For 2g caprylic acid, under the optimal conditions, with 0.4g immobilized lipase, at substrates molar ratio 1:10 (TMP to acid), temperature 40°C and water content controlled under 0.8% (w/w), the total conversion of fatty acid with TMP reached up to 96% and the formation of trisubstituted TMP esters reached 93%. Water content controlled during esterification process was found to be critical for high yield of direct esterification. [Copyright &y& Elsevier]

Biolubricants produced by chemically modifying vegetable oils are promising to replace mineral-based lubricants. However, the performances of biolubricants synthesized through traditional chemical modification routes, such as transesterification/esterification, epoxidation with further ring opening, and estolide formation, cannot satisfy the demands of extreme conditions. Meanwhile, complicated multi-step reactions cause expensive costs, which hinders their large-scale application. In this study, pelargonic acid (PA) derived from the cleavage of oleic acid was esterified with trimethylolpropane (TMP) to produce branched-chain esters (tri-TMP esters) catalyzed by the lipase (Candida sp. 99–125), focusing on batch stability of the lipase, thermal-oxidation stability and lubrication performance of the product. The lipase maintained high activity for 4 continuous batches in 5 L enzyme reactor with the conversion of PA > 96% and the accumulation of tri-TMP esters > 84% in each batch. The obtained tri-TMP esters had a pour point of − 56 °C, a viscosity index of 137, and a flash point of 276 °C. Anti-oxidation stability test and thermogravimetric behaviors showed that the biolubricant had favorable thermal-oxidative stability. Friction tests verified that the product displayed excellent lubrication performance with a minimum coefficient of friction (COF) of 0.099 and an average wear spot diameter (WSD) of 221.5 µm. The green and high-selective synthetic pathway fills the defect of existing routes for the preparation of biolubricants from chemically modified vegetable oils. [Display omitted] • Lipase-catalyzed synthesis of branched-chain esters based on PA and TMP was proposed. • The lipase maintained high activity for 4 continuous batches. • The tri-TMP esters has superior low-temperature performance and thermal-oxidative stability. • This biolubricant displayed excellent lubrication performance in HFRR tests. [ABSTRACT FROM AUTHOR]