Improving biodiesel yields from waste cooking oil using ionic liquids as catalysts with a microwave heating system

Biodiesel made from waste cooking oil (WCO) can be used to effectively reduce the raw material cost as well as solve the problem of waste oil disposal. This study investigates the use of the ionic liquid 4-allyl-4-methylmorpholin-4-ium bromine (IL; [MorMeA][Br]) as a catalyst and a microwave heating system for improving biodiesel yields from WCO. Experimental results indicate that [MorMeA][Br] catalyst can increase WCO biodiesel yields and decrease the use of NaOH catalyst by 0.25 wt.%. The best yield of WCO biodiesel is 89.1% under IL1NaOH0.75 catalyst (1 wt.% [MorMeA][Br] + 0.75 wt.% NaOH), a methanol-to-oil molar ratio of 9, a reaction time of 6 min, and a microwave temperature of 70 °C. The IL catalyst was recyclable and thermally stable with a yield close to 98% after the catalyst was used for 7 times repeatedly.