Biodiesel is considered a viable alternative to the use of diesel. Transesterification is the most used method of biodiesel production and usually occurs in batch reactors and requires several minutes or hours to achieve high yield rates. However, this process has been recently tested in microreactors. One of the most important elements of these microreactors is the micromixer, which should perform a quick and efficient mixing of reactants. Micromixers with circular obstructions split and recombine the flow stream, increasing the interaction of chemical species. Therefore, we carried out numerical simulations of Jatropha curcas oil-ethanol mixing and reaction in micromixers with circular obstructions. Three different micromixers were investigated: T-channel, T-channel with circular obstructions and T-channel with alternate circular obstructions. A mixing study was conducted for Reynolds number ranging from 1 to 160 and residence times for reaction of 0.20-100 s. The T-channel with alternate circular obstructions showed the highest degree of mixing (0.99). The presence of obstacles improved the conversion of species. Maximum conversion was 99.07% CT-channel), 99.01% (T-channel with circular obstructions) and 99.09% (T-channel with alternate circular obstructions). The effectiveness of using channels with circular obstructions in biodiesel synthesis was numerically demonstrated. (C) 2015 Elsevier B.V. All rights reserved.