Continuous flow through a microwave oven for the large-scale production of biodiesel from waste cooking oil

This report presents a method for producing large quantities of biodiesel from waste cooking oil (WCO). Preliminary studies on optimization of the WCO transesterification process in a continuous-flow microwave reactor are carried out using commercial SrO as a catalyst. The SrO catalyst can be separated and reused for five reaction cycles without loss in activity. Challenges like mass flow and pressure drop constraints need to be surmounted. SrO nanoparticles deposited on millimeter-sized (3–6 mm) silica beads (41 wt% SrO/SiO₂) are prepared and evaluated as a substitute for the SrO catalyst. A WCO conversion value to biodiesel as high as 99.2 wt% was achieved with the reactor packed with 15 g of 41 wt% SrO/SiO₂ catalyst in 8.2 min with 820 mL of feed. Excellent performance of the fixed-bed catalyst without loss in activity for a lifetime of 24.6 min converting a feed of 2.46 L to FAME was observed.