Continuous catalytic epoxidation of biodiesel for sustainable production of bio-based plasticizers using molecular oxygen

• Continuous epoxidation of biodiesel was performed with a packed-bed reactor. • Oxygen gas was used as an oxidant and exhibited good reaction performance. • Unsaturated FAMEs were epoxidized with over 95% conversion and 70% selectivity. • Oxidation of epoxidized products generated dihydroxy and carboxylic compounds. • Separation methods recovered liquid, gas, and solid substances for recycling. A continuous catalytic epoxidation process using molecular oxygen and heterogeneous catalysts was evaluated for the first time to produce epoxidized biodiesel. Soybean oil-based biodiesel and 10 wt% Mn/Al 2 O 3 were used as the feedstock and catalyst, respectively. The continuous epoxidation process used oxygen gas as the oxidant in place of hydrogen peroxide, enabling easy recycling. Over 95% of the unsaturated FAMEs in the feedstock were converted to epoxides at 160 °C and 10 bar with 10 ccm of oxygen gas, yielding over 70% selectivity to epoxides. The recovery of gas, liquid, and solid phases was successfully achieved by simple liquid–gas separation and 2-stage distillation. An integrated epoxidation process was proposed to produce bio-based plasticizers with continuous separation of the products, solvent, and oxidant for recycling.