Nonedible waste sourced lipids such as fatty acid distillates,
brown grease, and animal tallow, among many others, are excellent
alternatives for expanding the feedstock inventory for biodiesel synthesis.
A quaternary ammonium-based deep eutectic solvents (DESs) was used
as a catalyst in the glycerolysis of free fatty acids (FFAs) in this
study. Reaction optimization was carried out with oleic acid as the
model molecule, followed by an in-depth examination of the reaction
mechanism. Optimum conditions such as 130 °C and 10 wt % catalyst
dosage with 10 min of reaction time gave an equilibrium conversion
of 94%. The catalyst was found to remain in the glycerol phase allowing
its reuse. Palm fatty acid distillate, brown grease, and crude glycerol
were utilized for testing the novel DES at optimum conditions. FFA
conversion was found to be 94% for both palm fatty acid distillate
and brown grease. In the case of crude glycerol, FFA conversion decreased
proportionally to the impurity level. Water was responsible for restricting
equilibrium conversion and decreasing catalyst recyclability, necessitating
further research into effective removal during the reaction. Aggressive
nitrogen purging to remove water during the reaction pushed the reaction
toward near-completion in 60 min. The catalyst reusability study showed
a drop in equilibrium conversion to 62.5% at the end of the 5th cycle,
even when water was removed.