Synthesis of biodiesel by Fe(II)-Zn double-metal cyanide complexes

A kind of Fe(II)-Zn double-metal cyanide (DMC) complexes solid catalyst was prepared through coreaction of potassium ferrocyanide, zinc chloride, and complexing agent of tert-BuOH. The catalyst has highly catalytic activity on the simultaneous transesterification of triglycerides and esterification of free fatty acids (FFA) reactions. The effect of various factors on the reaction was studied, including different cocomplexing agents, DMC catalyst amount, reaction temperature, methanol/oil molar ratio, reaction time, and water and fatty acid content in raw materials. High catalytic activity was observed for DMC under relatively higher content of water or FFA. Under the optimum condition the methyl ester yield can reach 98%. 93.45% of the catalyst can be recovered after 6 cycles.