New Lubricant from Used Cooking Oil: Cyclic Ketal of Ethyl 9,10-Dihydroxyoctadecanoate

Abstract

A new ketal cyclic from ethyl 9,10-dihydroxyoctadecanoate with acetone had been synthesized by reflux and sonochemical method. The synthesis was performed via several steps of reaction, i.e.: transesterification, hydrolysis, oxidation with 1% KMnO4 in basic condition, esterification, and ketalization. The structures of the products were confirmed by FTIR, GC-MS, 1H- and 13C-NMR spectrometers. Direct transesterification of used cooking oil produced a mixture of ethyl ester in 82.94% yield meanwhile hydrolysis of this mixture gave free fatty acids mixture in 88.46% yield. Hydroxylation reaction of free fatty acids mixture yielded a white powder of 9,10-dihydroxyoctadecanoic acid in 46.52% yield. Esterification of 9,10-dihydroxyoctadecanoic acid and ethanol catalyzed by sulfuric acid with reflux condition for 4 hours and sonochemical method, respectively yielded 90% and 93.8% of ethyl 9,10-dihydroxystearate. In the other side, the utilization of KSF montmorillonite as catalyst conducted with reflux gave 52% in yield of ester. Furthermore, the use of acetone in 45 minutes sonochemical method with montmorillonite KSF catalyst gave cyclic ketal (ethyl 8-(2,2-dimethyl-5-octyl-1,3-dioxolan-4-yl)octanoate) as a yellow viscous liquid in 53.30% yield. From physicochemical properties –density, kinematic viscosity, viscosity index, total acid number, total base number and iodine value- gave the conclusion that this novel compound is potential biolubricant candidates to be developed.