KOH-catalyzed synthesis of biodiesel was carried out in capillary microreactors with inner diameters of 0.25 or 0.53 mm, with unrefined rapeseed oil and cottonseed oil as raw materials. The influences of the methanol to oil molar ratio, the residence time, the catalyst concentration, the reaction temperature, and the dimension of the capillary on the production of biodiesel were examined. Theā¦