Enhancement of biodiesel production from waste cooking oil: ultrasonic- hydrodynamic combined cavitation system

Abstract

ABSTRACTConcerning the growing need for energy resources and reduction of fossil fuels, researchers seek for the use and development of biofuels. Among the biofuels, biodiesel has captured the attention of researchers since it deals with the oil cost and embraces environmental benefits. Aiming at continuous and optimal biodiesel production, the current study examines the effects of the residence time of hydrodynamic reactors, catalyst concentration, methanol-to-oil ratio, and ultrasound power on methyl esters yield. To optimize the transesterification reaction of the waste oil, the response surface method was used. Results of the study indicated that the increase of residence time results in an increase of the methyl esters yield, but following the time up to 90 s, the methyl esters yield decreases. The increase of catalyst by 1% leads to the increase of the methyl esters yield, and up to 1.25% the catalyst concentration, the methyl esters yield decreases by 7%. The increase of methanol-to-oil ratio up to 6:1 results in an increase of yield, and up to 8:1 methanol-to-oil ratio, the methyl esters yield follows an increasing trend with a slight slope. The optimal conditions in this study were 60 s residence time, 1% catalyst concentration, 6:1 methanol-to-oil ratio, and 250W ultrasound power, and that the methyl esters yield, as well as the consumed energy, were obtained 90.45% and 21.52 kJ, respectively. In conclusion, the suggested method is suitable for biodiesel production based on the methyl esters yield and energy consumption.