The homogeneous base-catalyzed methanolysis of sunflower oil in the presence and absence of tetrahydrofuran (THF) as a co-solvent was studied in a continuous cocurrent upflow reciprocating plate reactor (RPR). The measurements of the dispersed phase drop size demonstrated the effects of the THF concentration on the Sauter-mean drop diameter and the drop size distribution in both non-reactive (methanol/oil) and reactive (methanol/KOH/oil) systems. The presence of THF shifted both heterogeneous systems to the stable homogeneous emulsion consisted of small dispersed phase drops. The triacylglycerol (TAG) conversion degree was measured in the reactive system. The sigmoidal kinetics was observed in the absence and presence of THF at lower THF concentrations (<= 10% of the oil mass). This shape was explained by the existence of the initial TAG mass transfer controlled region followed by the irreversible second-order reaction controlled region. However, at the highest THF concentration (30% of the oil mass) the irreversible and reversible second-order reaction kinetics was used to describe the variation of TAG conversion degree with time. The proposed kinetic models satisfactorily fitted the experimental data. (C) 2015 Elsevier B.V. All rights reserved.