Continuous flow extraction of biodiesel produced in a packed-bed reactor using supercritical carbon dioxide and tetrahydrofuran as solvents

Abstract

The concurrent process of biodiesel (FAME) extraction and triglyceride methanolysis was carried out by using supercritical carbon dioxide (SC–CO2) and tetrahydrofuran (THF). This study explored the integration of SC-CO2 extraction facilitated catalyst-free transesterification efficiently at low temperatures with practical biodiesel productivity. The work started with studying the transesterification kinetics of triglycerides using different molar ratios of methanol under various SC-CO2 conditions in the presence of THF solvent. The elementary second-order kinetics associated with the mass transfer limiting factor satisfied the experimental results from all different mixing ratios. A four-factorial Box-Behnken Design (BBD) coupled with the ANOVA was employed to optimize the FAME recovery by the reaction-extraction processes with continuous two streams of SC-CO2 and 10% v/v THF-methanol mixture. The optimum predicted FAME recovery was 95.47% w/w at 71.93 °C, 186.67 bar using the substrate ratio 12.16. The supercritical fluid-assisted dispersion feature was characterized through the Peclect number (Pe) obtained from the volumetric dispersion model (VDM). The Pe could indicate suitable substrate mixing for the process operation and design to enhance production efficiency. The feasibility of upscaling the process to the commercial level was proposed with preliminary economic consideration, which could suggest process improvements in further research and technological development.