Glycerolysis of free fatty acid in vegetable oil deodorizer distillate catalyzed by phosphonium-based deep eutectic solvent

Abstract

Abstract Esterification of free fatty acids in a low-grade oil with glycerol, the by-product of transesterification, has been proposed as one possible method to reduce the cost of raw materials for biodiesel production. The glycerolysis reaction recycles the byproduct glycerol to create a much more efficient and cost-effective process. However, the glycerolysis reaction involves challenges, including its requirement of high temperature. This study is the first to apply the deep eutectic solvent (DES) as a catalyst for glycerolysis reaction to convert free fatty acid (FFA) in vegetable oil deodorizer distillate (VODD) being a waste product from the oil refining process into glycerides. The effects of temperature, catalyst dosage, and time on the esterification efficiency of fatty acid conversion were explored. The reaction progress and product solubility were studied by FT-IR and GC. The results revealed that the reaction reached equilibrium at an approximate free fatty acid (FFA) conversion of 90%. The reaction was a second-order reversible reaction, using 8 wt% catalyst loading lowered activation energy to 58.80 J/mol. The optimum condition was determined as 160 °C, 5 wt% DES loading, and 10 min reaction time.