Development of Biolubricants from Vegetable Oils for Non-Internal Combustion Engine Applications
Abstract
The promise of vegetable-based CEs in the lubrication industry lies in their ability to provide superior lubrication, thermal stability, and compatibility with various metals. The presence of unsaturated free fatty acids in the carbon chain of triglycerides and tertiary β-hydrogen group in the glycerol backbone causes low thermal and oxidative stability. Thus, this study investigated a cost-effective methodology that has been developed to produce biobased CEs with improved thermal and oxidative stability. This involves the conversion of vegetable oil triglycerides into trimethylolpropane (TMP) esters through a two-step transesterification-transesterification and a two-step hydrolysis-esterification process. To further increase the thermal and oxidative stability, an epoxidation reaction was performed in order to remove the C=C double bonds in the canola oil trimethylolpropane (COTMP) ester structure using tert-butyl hydroperoxide (TBHP) as an oxidizing agent in the presence of a heterogeneous catalyst. The conversion, selectivity, oxirane oxygen content (OOC), and iodine value of the final epoxidized canola oil trimethylolpropane (ECOTMP) ester was 95.2%, 98.62%, 4.12%, and 3.4 mg I2/g, respectively.
This work has focused on the conversion of vegetable oils to saturated complex esters through several chemical modifications (e.g., hydrolysis, esterification/transesterification, and epoxidation) and demonstrated the effective use of metal complexes as heterogeneous catalysts in the epoxidation reaction. The novelty of this study is the formulation of biolubricants with outstanding wear scar diameter (WSD) from vegetable oils and the development of a heterogeneous catalyst for epoxidation reaction to increasing the conversion, selectivity, and OOC of the final product.