Synthesis and Optimization Process of Ethylene Glycol-Based Bio-lubricant from Palm Kernel Oil (PKO)

Abstract

Internationally exploited lubricants are derived from coal and petroleum. Due to their high consumption and effects of their long-term pollution on the environment, it is imperative to use renewable and cheap feedstock for the synthesis of bio-based lubricants. This study presents the synthesis and optimization process of Ethylene Glycol (EG) based bio-lubricant from palm kernel oil. Palm Kernel Methyl Ester (PKME) was synthesized at a reaction time of 60 min, a molar ratio of oil: methanol 1:6, a temperature of 60 oC, and catalyst of 1 % wt/wt (in-situ transesterification) via reactive extraction. Box-Behnken design (BBD) in response surface methodology (RSM) was applied to this experimental layout. The effects of molar ratio, reaction time, and temperature on the synthesis of palm kernel bio-lubricant (PKBL) were evaluated. The PKBL structure was characterized by Fourier Transform Infra-Red (FT-IR) and Gas Chromatography-Mass Spectrometry (GC-MS) analysis, showing favorable lubricating properties. The PKME yielded 94.53 wt% based on the weight of the oil, while transesterification of the in situ derived PKME with EG yielded 93.08 wt% of the EG ester (Bio-lubricant). The maximum bio-lubricant recovery was 81.48 wt% obtained at a molar ratio of 3:1, time of 2.48 h, and temperature of 135 oC. The temperature and mole ratio were established to be the most significant terms. PKBL characteristics conformed to ISO VG criteria and had a high potential for bio-lubricant feedstock.