Lubricity Performance of Ethylene Glycol Ester from Soybean Oil as a Lubricity Enhancer Bio-Additive for Low-Sulfur Diesel Fuel

The present study aims to show the tribological properties of soybean oil's ethylene glycol ester (SOEGE) and its effect on low-sulfur diesel fuel lubrication.  The SOEGE or 2-hydroxyethyl ester was synthesized by a transesterification reaction of soybean oil and ethylene glycol with a potassium carbonate catalyst. The product was characterized using Gas Chromatography-Mass Spectrometry (GC-MS). Then, the lubricity of commercial diesel fuel (Pertadex) and SOEGE were tested alone using the High-Frequency Reciprocating Rig (HFRR) machine. Its mixture form with various product doses in Pertadex (0.2, 0.4, 0.6, 0.8, and 1% v/v) was also tested with the same apparatus. This study showed that the product's coefficient of friction and Wear Scar Diameters (WSD) were 0.057 and 154.4 m, respectively. This value is lower than Pertadex and Fatty Acids Methyl Ester (FAME) of Soybean oil from the literature. Furthermore, adding products into Pertadex can reduce the coefficient of friction and WSD of Pertadex. The Pertadex coefficient of friction was reduced from 0.161 to 0.135 after the addition of 0.8% product. At a concentration of 1% product, WSD Pertadex was successfully reduced by 39.42%. These phenomena imply that ester ethylene glycol has an excellent lubricating effect on low-sulfur diesel. This work's findings open opportunities for other researchers to develop alternative lubricating bio-additives for low-sulfur diesel through the in-depth study of tribochemistry or tribosurface.