Keywords: Palm stearin; Fischer esterification; pentaerythritol; biolubricant; renewable sources

Abstract

Palm stearin was converted to biolubricant through the chemical modification process. Saturated palm stearin fatty acids (SPSFA) and unsaturated palm stearin fatty acids (UPSFA) were reacted with pentaerythritol (PE) via Fischer esterification to produce SPE-ester and UPE-ester. Both esters were successfully synthesized in a three-necked round bottom flask based on four parameters, and these were reaction temperature, reaction time, sulphuric acid (H2SO4) concentration as a catalyst and the molar ratio of reactants fixed to 5:1 for both SPSFA:PE and UPSFA:PE. About 69% of SPE-esters and 61% of UPE-esters were produced. Products characterization was performed by Fourier transformation infrared spectroscopy, proton, and carbon nuclear magnetic resonance (1H- and 13C-NMR) spectroscopy analysis techniques. The presence of ester carboxyl band, v(C=O) was at 1742 cm-1 for both SPE-ester and UPE-ester. SPE-ester and UPE-ester recorded their pour point at 44ºC and 9ºC, the flash point at 243ºC (SPE-ester) and 232ºC (UPE-esters), viscosity index about 140 (SPE-ester) and 151 (UPE-ester), oxidative stability at 269ºC for SPE-ester and 238ºC for UPE-ester. SPE-ester and UPE-ester could be categorized as ISO VG 46 and ISO VG 100 grade lubricant, respectively.