Influence of nature of catalyst on biodiesel synthesis via irradiation-aided transesterification of waste cooking oil-honne seed oil blend: Modeling and optimization by Taguchi design method

Abstract Biodiesel synthesis from waste cooking oil (WCO) and honne (Calophyllum inophyllum) seed oil (HSO) blend with heterogeneous (calcined Ba(OH)2 and calcined biomass waste (CBW) from Enterolobium cyclocarpum) and homogeneous (KOH) catalysts via two-step irradiated-transesterification process was evaluated in this study. The modeling and optimization of the two processes were studied using Taguchi orthogonal array technique. The factors considered for the esterification process were methanol/WCO-HSO ratio (10:1–30:1), time (2–8 min), heating power (150–450 W), and H2SO4 dosage (0.5–1.5 wt%). In contrast, the factors considered for the transesterification process were methanol/WCO-HSO ratio (6:1–12:1), time (1–7 min), heating power (150–450 W), and catalyst dosage (1–2.5 wt%). Minimum FFA of 0.50% was attained using methanol/WCO-HSO ratio of 30:1, time of 2 min, heating power of 150 W, and H2SO4 dosage of 1.5 wt%. For the transesterification of WCO-HSO blend, the optimum values are methanol/WCO-HSO ratio of 6:1, time of 1 min, heating power of 450 W, and KOH dosage of 1.75 wt% with a biodiesel yield of 99.4 wt%; methanol/WCO-HSO ratio of 6:1, time of 1 min, heating power of 300 W, and calcined Ba(OH)2 dosage of 1.75 wt% with a biodiesel yield of 98.8 wt%; and methanol/WCO-HSO ratio of 6:1, time of 4 min, heating power of 450 W, and CBW dosage of 1.75 wt% with a biodiesel yield of 100 wt%. The processes catalyzed with synthetic KOH and Ba(OH)2 reached maximum biodiesel yield faster than the crude CBW. The biodiesel quality obtained in this study shows that all three fuels met the American standard specifications and could thus serve as substitutes for fossil diesel.