Ethyl esters were synthesized by simultaneous esterification and transesterification reactions, using Jatropha curcas L. oil as raw material and sulphated zirconia (SZ) as catalyst. SZ catalysts were synthesized by the precipitation method, and the final pH of each precipitation was 6, 7 and 8 (SZ6, SZ7 and SZ8, respectively). X-ray diffraction showed the presence and intensity of a tetragonal crystal phase, which was associated with acidity and activity of the catalysts. In addition, the BET surface area was directly proportional to the pH of precipitation. During the catalytic tests it was observed that the most acidic sample (SZ8) had the highest catalytic activity for simultaneous esterification and transesterification, resulting in a 59.4% yield of ethyl esters. Furthermore, the catalyst had activity for separate esterification and transesterification reactions, and both were influenced by the mechanism of the simultaneous reactions. It could also be seen that, in reactions at different acidity levels, free fatty acids influenced the reaction mechanism, such that for high acid contents (14.29%), higher ethyl ester yields and faster reaction rates were obtained compared with lower acid contents (2.39%). (C) 2016 Elsevier B.V. All rights reserved.