A non-conventional biodiesel process route from waste palm fatty acid distillate and ethyl acetate via esterification

Abstract

The high cost and food competition associated with conventional biodiesel feedstocks limit its widespread adoption. This research investigates using palm fatty acid distillate (PFAD), a low-cost industrial by-product which is high in free fatty acids (FFAs), as a sustainable feedstock. A novel glycerol-free esterification route was developed employing ethyl acetate as acyl acceptor and sulfuric acid as catalyst, producing fatty acid ethyl esters (FAEEs) and valuable acetic acid as by-product. The characterization of PFAD confirmed its high FFA content of 91.78 ± 0.62%, then the Taguchi method was employed to systematically optimize key reaction parameters: reaction time (2-4 h), temperature (55-75 °C), catalyst amount (3-9 wt%), and ethyl acetate to PFAD molar ratio (5:1-15:1). Taguchi orthogonal design revealed that the ethyl acetate to PFAD molar ratio had the most significant impact on FFA conversion and time had the lowest impact. Optimal conditions were identified as 4 h, 65 °C, 6 wt%, and 15:1 molar ratio, yielding a predicted maximum FFA conversion of 87.74%. Experimental validation under these conditions achieved an average conversion of 86.28, confirming excellent agreement with the prediction. This research presents one of the first systematic Taguchi optimizations of PFAD esterification using ethyl acetate, offering a greener, glycerol-free pathway compared to conventional methanol-based processes. The proposed route contributes to sustainable biodiesel production from waste products, aligning with global renewable energy goals and economic viability.