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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]

Due to the poor biodegradability and toxicity of mineral-based lubricants, the development and application of plant-based biolubricants are increasing. However, low stability and poor low temperature performance restrict plant oils to use as lubricants directly. Hence, the paper tried to find an efficient and green way to modify the plant oil derivate oleic acid and obtained high-performance biolubricants. This study demonstrated that modification of oleic acid through epoxidation combined with ring opening reaction, and further esterification, was an efficient strategy for modifying unsaturated fatty acids for the biolubricant production. Meanwhile, catalytic effects of ionic liquids were compared with other catalysts. The results indicated that ionic liquid [HMIm][PF6] is an efficient catalyst for the ring opening and esterification for the synthesis of biolubricants with different kinds of fatty acids. Modified biolubricants from this research exhibited excellent viscosity index (>116) and low temperature performance (pour point < −48 °C). The results of high frequency reciprocating friction experiments exhibited superior lubrication performance of the lubricant. These findings provide a new green and efficient method for improving plant oils as biolubricants. Image 1 • Green way to produce high-performance biolubricant from oleic acid was developed. • Esterification after epoxide ring-opening is efficient for lubricant production. • Catalytic effects of ionic liquids were compared with other reported catalysts. • Biolubricant from this research exhibited excellent low temperature performance. [ABSTRACT FROM AUTHOR]

Due to the poor biodegradability and toxicity of mineral-based lubricants, the development and application of plant-based biolubricants are increasing. However, low stability and poor low temperature performance restrict plant oils to use as lubricants directly. Hence, the paper tried to find an efficient and green way to modify the plant oil derivate oleic acid and obtained high-performance biolubricants. This study demonstrated that modification of oleic acid through epoxidation combined with ring opening reaction, and further esterification, was an efficient strategy for modifying unsaturated fatty acids for the biolubricant production. Meanwhile, catalytic effects of ionic liquids were compared with other catalysts. The results indicated that ionic liquid [HMIm][PF6] is an efficient catalyst for the ring opening and esterification for the synthesis of biolubricants with different kinds of fatty acids. Modified biolubricants from this research exhibited excellent viscosity index (>116) and low temperature performance (pour point < −48 °C). The results of high frequency reciprocating friction experiments exhibited superior lubrication performance of the lubricant. These findings provide a new green and efficient method for improving plant oils as biolubricants. Image 1 • Green way to produce high-performance biolubricant from oleic acid was developed. • Esterification after epoxide ring-opening is efficient for lubricant production. • Catalytic effects of ionic liquids were compared with other reported catalysts. • Biolubricant from this research exhibited excellent low temperature performance. [ABSTRACT FROM AUTHOR]

To reduce the environment pollution from biolubricant synthesis, in this study, we developed a green and efficient strategy for the preparation of octylated branched biolubricant from waste cooking oil (WCO): (1) WCO was first hydrolyzed by a lipase (Candida sp. 99–125) to produce unsaturated fatty acids (UFAs), the latter was subsequently concentrated by urea complexation; (2) Next, we synthesized new esters using the UFAs as substrate via esterification with 2-ethylhexanol employing lipase (Novozym 435) and the new esters products were further epoxidated; (3) After that, the epoxy group was attacked by a low-cost nucleophilic reagent, octanoic acid, to prepare octylated branched biolubricant using an recyclable ionic liquid, [HMIm][PF 6 ], as catalyst. After three recycling times, [HMIm][PF 6 ] remained catalytic activity with a conversion yield of 81.22% and selectivity of 82.10%. The obtained product showed excellent lubricant properties, such as low pour point of −61 °C, high viscosity index of 149 and high thermal-oxidation stability (onset temperature of 326.35 °C and oxidative onset temperature of 312.06 °C). The high frequency reciprocating rig (HFRR) measurement demonstrated that lubrication performance (friction coefficient of 0.09 and wear spot diameter of 203 μm) was much better than that of mineral based lubricant with the same viscosity grade. Therefore, this study provided a critical synthetic strategy for preparing high-performance biolubricants from WCO. Image 1 • An innovative strategy of biolubricant preparation from waste cooking oil was proposed. • Modification on unsaturated sites catalyzed by lipases and ionic liquid. • [HMIm][PF 6 ] remained high stabilization after three recycling times. • Biolubricant exhibited excellent pour point, thermo-oxidative stability and lubrication performance. [ABSTRACT FROM AUTHOR]