Biodiesel production assisted by 4-allyl-4-methylmorpholin-4-ium bromine ionic liquid and a microwave heating system

• Ionic liquids have been used as environmental solvents/catalysts for reactions.
• Microwave can increase reaction rate, product yields, and purity of products.
• The used ionic liquid ([MorMeA][Br]) can be used as catalysts for biodiesel.

This study investigates the use of the ionic liquid 4-allyl-4-methylmorpholin-4-ium bromine (IL; [MorMeA][Br]) as a catalyst together with a microwave heating system for improving methyl ester yields. The highest yield (99.4%) catalyzed with IL1NaOH0.75 catalyst (1 wt% [MorMeA][Br] + 0.75 wt% sodium hydroxide (NaOH)), was achieved at a methanol-to-oil molar ratio of 9, a reaction time of 6 min and a microwave temperature of 70 °C. Under the operating conditions studied, our findings identified the parameter ranges where yields increase with increasing methanol concentrations, catalyst concentrations and reaction temperatures. Furthermore, the reduction of yields was observed in the case with the excessive addition of methanol concentrations due to the elevated solubility of glycerol that reverses the reaction. Also, yield reduction was found in the excessively high concentration of catalyst that increases glycerin due to saponification. The increased glycerin that decreases the production of biodiesel was observed as well when the reaction temperature is elevated. Microwave heating system has better performance and offers a fast route of biodiesel production, which is also more energy-efficient and cost-effective.