Optimization of biolubricant production process from biodiesel of Non-edible rapeseed using response surface method (RSM)

Oil-based lubricants are a stable source for lubricating moving parts in mechanical systems. Low oxidative stability and high pour point are the major problems of vegetable oils that prevent their extensive use as a lubricant. In this study, two-stage transestrification method was used to improve the disadvantages of non-edible rapeseed oil. In the first step, methyl ester of non-edible rapeseed oil was produced by transestrification method using an ultrasound power. In the second step, using ultrasound power the reverse transesterification reaction of methyl ester with tri-methyl propanol was examined. In order to increase the reaction rate of biolubricant production, the ultrasound system was used, which is a new way to production of biolubricant. The ultrasound power by creating the phenomenon of cavitation causes proper mixing and improving the mass transfer and increasing the biolubricant production rate. The effects of independent variables such as pulse, amplitude, and time on the efficiency and energy consumption was investigated using RSM method. It should be noted that the variables such as temperature, the molar ratio of methyl ester to tri-methyl propanol, catalyst concentration, and vacuum pressure were considered constant. The biolubricant yield and energy consumption were 82.2% and 116.726 kJ under the optimized conditions, i.e., a pulse of 40%, an amplitude of 82.01%, and a reaction time of 60 min. The biolubricant was confirmed using nuclear-hydrogen magnetic resonance spectra (H-NMR). The physical and chemical properties of the synthesized biolubricant have been evaluated by measuring standards. The biolubricant prepared (using ultrasonic method) from non-edible rapeseed oil complies with the criteria dictated by ASTM D6751 standards. The physical and chemical properties of the synthesized biolubricant conform to the reference lubricant (ISO VG 10). Regarding the results, it was found that using ultrasonic system the biolubricant can be produced in much less time than the traditional method. The bioubricant production with ultrasonic system can be introduced as a new method to the world.