Biodiesel (fatty acid methyl/ethyl esters) is a popular possible alternative to fossil fuels due to the potential exhausting of traditional fuels and increasing price of petroleum together with environmental concerns. In the present work, biodiesel production from the esterification of the free fatty acid oleic acid with ethanol over aminophosphonic acid resin D418 has been studied, and the effects of experimental factors such as amount of D418, reaction temperature and molar ratio of ethanol to oleic acid on the conversion ratio were evaluated. The process optimization using response surface methodology (RSM) was performed and the interactions between the operational variables were elucidated. The optimum values for maximum esterification percentage can be obtained by using a Box-Behnken center-united design with a minimum of experimental work, and the oleic acid conversion reached 92.02 +/- 0.74% with the molar ratio of alcohol to oleic acid being 14:1 and a content of 10.2 wt.% D418 catalyst at 115 degrees C. Moreover, the kinetics for the esterification catalyzed by D418 catalyst has been studied, and the pseudohomogeneous (PH) model has been used to simulate the experimental data. (C) 2012 Elsevier Ltd. All rights reserved.