Synthesis of biodiesel by transition metal doped Fe/Zn double metal cyanide complex catalysts

Effects of transition metals (La, Ce, Zr, Mn) on catalytic performance of double metal cyanide (DMC) catalysts for biodiesel synthesis were studied. The structure and performance of the catalysts were studied using XRD, FT-IR, ICP, BET et al. The experimental results showed that the DMC catalyst prepared by adding 1% of transition metal salts had higher activity. The catalyst with highest catalytic activity was prepared by adding 1% of La(NO₃)₃·nH₂O. Under the conditions of methanol/oil mol ratio of 16∶1, catalyst amount of 2% and temperature of 160 ℃, a high yield (99.3%) of fatty acid methyl esters (FAME) was obtained within 7 h. The analytical results showed that adding 1% of transition metals did not change the molecular formula of Fe(II)-Zn double metal cyanide complex catalysts, while it improved particle dispersion, decreased particle size and increased surface area. This was the reason that transition metals promoted catalysts had higher activity.