AbstractIn recent years, there has been a growing demand for environmentally friendly epoxides made from vegetable oils. Therefore, the use of materials from renewable resources, was implemented in this study with natural zeolite as a catalyst being chosen over synthetic zeolite because synthetic zeolite mostly consists of strong corrosive materials. The aims of this research to determine the effect of catalyst concentration on the relative conversion of oxirane (RCO). RCO was the highest at 30 min of the reaction for sunflower oil, being 72% at 80°C using a 0.25 g concentration of catalyst. Meanwhile, for palm oil, the highest RCO was only 52% at 80°C. Lastly, MATLAB software was used to develop a mathematical model for determination rate constant. In this model, the Runge–Kutta method of the fourth order was combined with genetic algorithm optimization to for development of kinetic model that best fitted with the experimental data.