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 CC), ethanol/oil molar ratio (6-12), and catalyst concentration (0.75 wt%-125 wt%), using three microchannel configurations (Length = 35 mm; Width = 1500 mu m; Height = 200 mu m): 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 degrees C, molar ratio of 9 and catalyst concentration of 1%. Experimental results showed high conversions for MW and MWO configurations (99.99%) at 50 degrees C, molar ratio of 9 and catalyst concentration of 1%, with a residence time of 12 s. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.