Green synthesis and property analysis of biolubricants

Abstract: A biolubricant's molecular structure is crucial in determining its physicochemical and tribological characteristics. In this study, five triesters such as trimethylolpropane-triisostearate (T-IS), trimethylolpropane-triisooleate (T-IO), trimethylolpropane-trioleate (T-OA), glycerol-triisooleate (G-IO) and glycerol-trioleate (G-OA) have been synthesized via esterification of glycerol/trimethylolpropane with the respective free fatty acids (FFAs). FFAs such as methyl-branched isostearic and isooleic acids used for these T-IS, T-IO and G-IO triester’s synthesis were previously made via skeletal-isomerization of naturally derived oleic acid using a reusable zeolite catalyst. Any unreacted FFAs from the esterification were recycled for the next batch synthesis, resulting in little to no waste being produced. The synthetic triesters' chemical structures have been identified with NMR, LC-MS, FTIR and GC-MS. Physicochemical and tribological characteristics of these triesters have been compared to each other and with that of high-oleic sunflower oil and polyalphaolefin, common lubricant base oils to demonstrate how the differences in molecular structure can influence their properties. According to lubricant property analysis all five of the synthesized triesters have potential to be employed as biolubricants.