Biodiesel production with enhanced fuel properties via appropriation of non-edible oil mixture using conjoint ultrasound and microwave reactor: Process optimization and kinetic studies

Abstract

Current study investigates a novel simultaneous application of microwave and ultrasound irradiation (MW + US) via appropriation of raw castor oil (RCO) and waste cooking oil (WCO) blends for transesterification aiming on process optimization, reaction kinetics, and energy analysis. Applying Box-Behnken design, effect of process variables viz., methanol/oil ratio, KOH loading, reaction time, and blended oil ratio of RCO + WCO on biodiesel production was analyzed. First time, blended oil ratio as a process variable is studied and found to be most significant variable. The optimized conditions observed were methanol/oil ratio: 8.42:1, KOH loading: 0.52 w/w%, reaction time: 9.04 min, and blended oil ratio RCOWCO: 61RCO39WCO with experimental and predicted yield of 93.12 ± 0.24% and 92.81% respectively. First-time reaction kinetics study performed on RCO + WCO blended oils exhibited that reaction follows pseudo−1st-order kinetic with 2.5 times lower activation energy as compared to mechanical stirring process. Conjoint technique showed better energy dissipation with significantly reduced specific energy consumption. The physicochemical properties of RCOWCO biodiesel were found comparable to gasoline-diesel and international biodiesel standards. In comparison to castor oil biodiesel, blended oil biodiesel physicochemical properties improved significantly (esp. calorific value improved by 6–12%) and can be used as a renewable fuel to blend with petro-diesel.