Preparation and Physicochemical Properties of a New Biolubricant from Epoxidized Fatty Acids and Diethylene Glycol Monomethyl Ether

In this work, a new way of biolubricant synthesis is described using diethylene glycol monomethyl ether (DEGME) as a novel coreactant for the dual etherification and esterification of epoxidized mixed fatty acid (EO), catalyzed by p-toluenesulfonic acid (p-TSA) as a catalyst. A constant EO:DEGME molar ratio of 1:2 was used for the reaction, and different catalyst loadings (2.6 wt %), temperatures (120 °C), and reaction times (5 h) were used. Under the optimum operating condition, a conversion of 100% was reached, and the ester-based biolubricants with a yield of 89.9% were attained. The final lubricants were primarily made of mono- and diesters. Physicochemical characteristics, including kinematic viscosity, viscosity index, pour point, acid value, and moisture content, were assessed using accepted ASTM methods. Among the basic stocks created, ester-based lubricants showed good characteristics such as the kinematic viscosity of 47.8 cSt at 40 °C and 8.3 cSt at 100 °C, a high viscosity index of 150, a pour point of −1 °C, a low acid value of 0.24 ± 0.02 mg KOH/g, and a low moisture content of 0.01 ± 0.005%. Our research provides a cost-effective and environmentally friendly method for creating high-performance biolubricants with tunable kinematic viscosity range, high viscosity index, and low water impurity. This innovative palm fatty acid-based biolubricant leads to potential industrial utilizations such as hydraulic oil, transformer oil, and metal cutting fluid.