D-Optimal Design Optimization for Esterification of Palm Fatty Acids Distillate with Polyhydric Alcohols for Biolubricants Production

Plant-based biolubricant is crucial to be developed and adopted for many industries. This is due to the presence toxicity risk, climate change, energy security as well green-environmental approach issues. The utilization of palm oil processing industries by-product, palm fatty acid distillate (PFAD-based biolubricants is one way of green environment approach. A synthesis of polyol esters based on PFAD for biolubricants was carried out. The esterification of PFAD with high degree polyhydric alcohols trimethylolpropane (TMP), di-trimethylopropane (di-TMP), pentaerythritol (PE) and di-pentaerythritol (Di-PE) in the presence of sulphuric acid (H2SO4) catalyst have been performed. The optimization of the esterification reaction process was evaluated using D-optimal design based on three reaction parameters; H2SO4 concentration (%) for the catalyst, esterification time (h) and esterification temperature (°C). The chemical structure of the synthesized polyol esters was characterized and confirmed by using FTIR and NMR (1H and 13C) spectroscopies. The results showed that PFAD-based polyesters of PFAD-TMP ester successfully produced in high yields of 93% compared to others. The synthesized PFAD-based polyesters showed good lubrication properties with high viscosity indices in the range of 141-187, pour points (-5 to 5 oC), flash points (230-360 oC), and oxidative stability temperature (188-301 °C), respectively. The ester functional group presence in their chemicals structure of PFAD-based polyesters showed positive impact on the lubrication properties. The study indicated that the PFAD-based polyesters are plausible to be used as industrial biolubricants application.