Synthesis of 2-Hydroxyethyl Esters from Castor Oil as Lubrication Bio-Additive Candidates for Low-Sulfur Fossil Diesel

Abstract

The present work aims to study the synthesis of 2-hydroxyethyl esters from castor oil and its lubrication properties, promising as a lubrication bio-additive in low sulfur diesel fuel. This compound has been successfully synthesized from castor oil and ethylene glycol. The oil to ethylene glycol molar ratio was adjusted to 1:10, and the catalyst loading was used at 9% mole oil. Then, the mixture was refluxed for 5 h. The product components were characterized using GC-MS. The standard ASTM method was used to study the kinematic viscosity and lubrication. The product was dominated by 2-hydroxyethyl esters (94.16%), di-ester (1.12%), and cyclic ester (1.92%). The analysis of friction coefficient and wear scar diameter (WSD) using High-Frequency Reciprocating Rig (HFRR) shows the coefficient of friction and WSD of the product better than reference diesel fuel. From the results of this study, the 2-hydroxyethyl ester of castor oil, especially 2-hydroxyethyl ricinoleate, is the main responsible for the lubricating properties. Thus, 2-hydroxyethyl esters of castor oil can be proposed as an alternative bio-additive to improve the lubrication of low-sulfur fossil diesel fuels.

A Review on the Impact of Bio-Additives on Tribological Behavior of Diesel Fuels

“…In 1993, the United States (US) Environmental Protection Agency (EPA) mandated the use of low-sulfur content diesel fuel with sulfur levels <500 ppm. However, since 2006, the most recent EPA requirements have mandated that refineries producing ultralow-sulfur diesel (ULSD) fuel must generate <15 ppm of sulfur [18]. Since 2007, ULSD has been mostly used in Europe and America, so they are reported to have the world's lowest lubricity diesel fuel.…”

“…The physicochemical characteristics of vegetable oil are determined by the fatty acid makeup [18]. The amount of double bonds and the length of the carbon chain are used to identify fatty acids.…”

“…Fuel is used to overcome resistance from the tires, brakes, transmission, and engine in addition to the energy released by the car's decreased kinetic energy when its speed is lowered. Diesel engines have larger mechanical frictional losses than petrol engines due to the presence of high-pressure pumps in the fuel delivery system (for example, piston-crank pin journal, piston ring-cylinder wall, fuel pump element, and several auxiliary assemblies) [18]. It is also possible to reduce fuel consumption by 1.5%-2.5% if mechanical friction losses are reduced by 10% [19].…”