Synthesis and application of trialkyl methyl ammonium oleate and trialkyl methyl ammonium stearate as additives for lubricants

Abstract

This research aims to synthesize bio-based ionic liquids (ILs) derived from Aliquat and long-chain fatty acids (oleic and stearic acid) to enhance the dispersion stability and tribological performance of reduced graphene oxide (rGO) in lubricant oils. The [Aliquat][Oleate] and [Aliquat][Stearate] ionic liquids were synthesized via a two-step method, with their molecular structures successfully verified through FT-IR and ¹H-NMR spectroscopy. Experimental results indicated that [Aliquat][Stearate] required more rigorous synthesis conditions (90°C for 9 hours) compared to [Aliquat][Oleate] (85°C for 8 hours) at an optimal molar ratio of [RCOOH]/[Aliquat] = 1.3. Under these parameters, high yields of 80.1% and 83.2% were achieved, respectively. Furthermore, the synthesized ILs significantly improved the stability of rGO within the lubricant base. Tribological testing demonstrated that additives formulated with rGO and ILs effectively minimized the friction moment of the motor; specifically, additives containing [Aliquat][Oleate] and [Aliquat][Stearate] yielded friction reductions of 64% and 60%, respectively, compared to 58% for pure rGO. These findings highlight the practical significance of using ionic liquids as effective surfactants to prevent rGO aggregation, offering a robust solution for developing high-performance, stable nano-lubricants for industrial engine applications.