Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1-18:1), the H2SO4 concentration (0.5-2 wt.%), reaction temperature (55-70 degrees C), and reaction time (5-20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H2SO4, 65 degrees C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%. (C) 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.