Abstract: The nano K₂CO₃/γ-Al₂O₃ catalyst was prepared by isochoric impregnation,and the effects of preparation conditions of catalyst on transesterification were studied. The thermal properties and the size of catalyst were characterized by TEM and TG-DSC. Results of TEM showed that the size of catalyst was 30-50nm.The optimal conditions to prepare catalyst were as follows: mass ratio of K₂CO₃ to γ-Al₂O₃ was 50%, calcination temperature was 600℃, calcination time was 4h. The best conditions to prepare biodiesel as follows: the m(methanol) to m(oil )was 12:1, m(catalyst) in oil was 3%, the reaction time was 3h, the reaction temperature was 70℃, and the final yield could reach 97.90%. Quality specifications of biodiesel are accord with the national standard.

Key words: nano-solid alkali catalyst, transesterification, biodiesel