Application of Quaternary Ammonium-Based Deep Eutectic Solvents as Catalysts for the Glycerolysis of Free Fatty Acids

Nonedible waste sourced lipids such as fatty acid distillates,brown grease, and animal tallow, among many others, are excellentalternatives for expanding the feedstock inventory for biodiesel synthesis.A quaternary ammonium-based deep eutectic solvents (DESs) was usedas a catalyst in the glycerolysis of free fatty acids (FFAs) in thisstudy. Reaction optimization was carried out with oleic acid as themodel molecule, followed by an in-depth examination of the reactionmechanism. Optimum conditions such as 130 degrees C and 10 wt % catalystdosage with 10 min of reaction time gave an equilibrium conversionof 94%. The catalyst was found to remain in the glycerol phase allowingits reuse. Palm fatty acid distillate, brown grease, and crude glycerolwere utilized for testing the novel DES at optimum conditions. FFAconversion was found to be 94% for both palm fatty acid distillateand brown grease. In the case of crude glycerol, FFA conversion decreasedproportionally to the impurity level. Water was responsible for restrictingequilibrium conversion and decreasing catalyst recyclability, necessitatingfurther research into effective removal during the reaction. Aggressivenitrogen purging to remove water during the reaction pushed the reactiontoward near-completion in 60 min. The catalyst reusability study showeda drop in equilibrium conversion to 62.5% at the end of the 5th cycle,even when water was removed.

Automated summary

Nonedible waste sourced lipids such as fatty acid distillates, brown grease, and animal tallow are excellent alternatives for biodiesel synthesis. A quaternary ammonium-based deep eutectic solvents (DESs) was used as a catalyst in the glycerolysis of free fatty acids (FFAs). Optimum conditions of 130 degrees C and 10 wt % catalyst dosage with 10 min of reaction time gave an equilibrium conversion of 94%.