In this study, 40 % CaO/γ-Al2O3 catalyst was used for biodiesel production from corn oil. A transesterification reaction was done for 5 h at a temperature of 65 ˚C in the presence of corn oil, methanol (methanol to oil molar ratio of 12:1), and CaO/γ-Al2O3 catalyst (6 wt. % ). Catalyst used in this study was synthesized using the sol-gel method. In this method, two parameters of gelation temperature and nitric acid concentration were used as variables in the catalyst synthesis step, and experiments were designed using central composite design (CCD). The results indicate that the optimal point is achieved at a gelation temperature of 70 ˚C and nitric acid concentration of 0.050 mol/L; in such conditions the purity and yield of produced biodiesel are 87.89 % and 79.10 %, respectively. Moreover, 40 % CaO/γ-Al2O3 catalyst was synthesized using the impregnation method and the same reaction conditions were used. The catalyst synthesized by the sol-gel method in optimal conditions and catalyst synthesized by impregnation method both were reused five times each. Catalyst reuse reduces the purity and yield of the produced biodiesel, because in each case of catalyst use, some amount of CaO is extracted by methanol. In addition, the leaching rate of CaO in the catalyst synthesized by the impregnation method was greater than that of the catalyst synthesized by the sol-gel method; consequently there is more reduction the activity of the catalyst synthesized by impregnation method.
