Continuous transesterification of palm olein oil using supercritical methanol was investigated in the absence of a catalyst. The variables studied were reaction temperature (270-350 degrees C), pressure (20-40 MPa), and residence time (5-25 min), with a methanol-to-oil molar ratio of 40. Preheating at 245 degrees C was used to form a homogeneous phase in the absence of thermal decomposition of palm olein oil. The activation energies and reaction activation volumes of the fatty acid methyl ester (FAME), and those of the individual components (C16:0, C18:0, C18:1, and C18:2 methyl esters), were calculated. The entropies of activation (Delta S double dagger) of the transesterification reactions were also obtained. As the transesterification of vegetable oil in supercritical methanol included a strongly negative (-175 J/mol K) entropy of activation, transesterification required harsh conditions. (C) 2011 Elsevier B.V. All rights reserved.