Ethyl acetate as extracting solvent and reactant for producing biodiesel from spent coffee grounds: A catalyst- and glycerol-free process

Abstract

Oil was extracted from spent coffee grounds (SCGs) using ethyl acetate at atmospheric pressure; then, the ethyl acetate–SCG oil mixture was reacted under supercritical conditions, which involve a catalyst-free process. Moreover, ethyl acetate reacted with glycerol to form triacetin, which dissolves in biodiesel and acts as a fuel additive. Using this approach, the solvent removal step and glycerol byproducts are eliminated. The highest fatty acid ethyl ester contents of 91.80 wt% ± 1.62 wt% and 86.44 wt% ± 2.12 wt%. were obtained under optimal conditions in batch and continuous reactors, respectively. Based on gas chromatography–mass spectrometric analysis, no trace of glycerol was detected and triacetin was yielded at 4.22 wt%. This novel process simultaneously minimizes the number of chemicals used and the amount of waste generated because it employs only dried SCGs and ethyl acetate as the feedstock.