Transesterification of sunflower oil in microchannels with circular obstructions

The present paper studied numerical and experimentally the transesterification reaction between sunflower oil and ethanol with NaOH catalyst in microchannels with circular obstructions. The micromixer design influence on fluid mixing and oil conversion was investigated for a range of operating conditions: Reynolds number (Re = 0.1-100), Temperature (25-75 °C), ethanol/oil molar ratio (6-12), and catalyst concentration (0.75 wt%-1.25 wt%), using three microchannel configurations (Length = 35 mm; Width = 1500 μm; Height = 200 μm): T-shape - channel without obstructions; MCO - channel with 3 obstructions ensemble - equally disposed over longitudinal length; MWO - channel with 7 obstructions ensemble. The MCO micromixer was based on literature work, and the MWO is a totally new micromixer design. Experimental tests were conducted in similar conditions in microreactors using these micromixers (Length = 411 mm) made of polydimethylsiloxane. The MCO configuration presented the highest performance (mixing index of 0.80 at Re = 100), oil conversion of 81.13% at 75 °C, molar ratio of 9 and catalyst concentration of 1%. Experimental results showed high conversions for MCO and MWO configurations (99.99%) at 50 °C, molar ratio of 9 and catalyst concentration of 1%, with a residence time of 12 s.