Intensification of Transesterification for Biodiesel Production in a Submerged Rotating Packed Bed-Helical Coil Reactor

Efficient biodiesel production was essential for reducing emissions and supporting carbon-neutral energy systems. Base-catalyzed transesterification has been widely used to produce fatty acid methyl esters (FAMEs) for biodiesel production. To overcome the mass transfer barrier between the liquid–liquid heterogeneous phases, this work developed a submerged rotating packed bed-helical coil (SRPB-HC) reactor to intensify transesterification via high-speed rotation of the SRPB packing and Dean vortices in the HC. Liquid–liquid dispersion was observed by a microscopy measurement system. The SRPB-HC reactor significantly intensified the liquid–liquid heterogeneous dispersion. The minimum Sauter mean droplet diameter ( d 32 ) reached 8.63 μm in the SRPB-HC with a narrow size distribution. NaOH-catalyzed transesterification was conducted, and the FAME yield was quantified by gas chromatography. A FAME yield of 99.27% was achieved in the SRPB-HC at the reaction temperature of 55 °C, rotational speed of 1200 r/min, throughput of 300 mL/min, catalyst loading of 1 wt % NaOH, and methanol/oil molar ratio of 6 with a residence time of 5.61 min. Fuel properties of the produced biodiesel satisfied the requirements specified in ASTM D6751. Compared with conventional reactors, the SRPB-HC offered a clear advantage in shortening reaction time while achieving higher yields at a higher throughput, demonstrating the potential for continuous transesterification for biodiesel production.