Synthesis and Evaluation of Octyl Methylimidazolium Oleate and Octyl Methylimidazolium Stearate as Lubricant Additives

Thuy Thi Le Bui

Abstract: The study reports the synthesis of octyl methylimidazolium oleate ([OMIM][Oleate]) and octyl methylimidazolium stearate ([OMIM][Stearate]) from octyl methylimidazolium chloride and fatty acids. The synthesized ionic liquids were characterized using FT-IR and 1H NMR spectroscopy. The effects of reaction temperature, reaction time, and reactant molar ratio on synthesis yield were systematically investigated. The optimum conditions were a [RCOOH]/[OMIM] molar ratio of 1.3, temperatures of 70?C and 78?C, and reaction times of 6 h and 7 h for [OMIM][Oleate] and [OMIM][Stearate], respectively. Under these conditions, yields of 88.5% and 80.7% were obtained. When combined with reduced graphene oxide, the ionic liquids improved dispersion stability in lubricant and enhanced friction reduction. Among the two additives, [OMIM][Oleate] exhibited superior dispersion stability and tribological performance, demonstrating its potential as an environmentally friendly lubricant additive.

Keywords: Ionic liquids, Octyl methylimidazolium, Oleate, Stearate, Reduced graphene oxide, Lubricant additives, Tribology, Green chemistry