Castor oil based biolubricant: optimization of the synthesis process and investigating its effects on two-stroke engine parameters

Abstract Biolubricants are new generation of lubricants, which are vegetable based, renewable and eco-friendly. In this study, trimethylolpropane ester (biolubricant) was synthesized from castor oil methyl ester through transesterification reaction. The reaction was optimized using response surface methodology (RSM) and the optimal parameters were obtained for maximizing the reaction yield. In continuation, the physicochemical specifications of the purified product was measured and met the requirements of ISO-VG lubricant standard. The castor oil based biolubricant then was mixed with gasoline with 1:10 volumetric ratio and was used in a 200 cc two stroke petrol engine to investigate its effects on the performance and exhaust emissions of the engine. The optimal conditions for biolubricant synthesis reaction were obtained as the methyl ester to TMP molar ratio of 4.78:1, reaction temperature of 139.9°C, and the catalyst (potassium carbonate) concentration of 1.4%. In this optimum condition, the reaction yield was obtained as 96.13%. The engine tests results showed that the engine power and torque increases by 2.89% and 1.97%, respectively using castor oil based biolubricant compared with SAE10 oil. Moreover, the brake specific fuel consumption (BSFC) of the engine fuelled with biolubricant had a 4.6% decrease compared to the commercial two-stroke engine oil. It was also found that the produced castor biolubricant can significantly decrease the carbon monoxide and unburned hydrocarbons emissions of the engine by nearly 153% and 59%, respectively in comparison with SAE10 oil.