Nanometer magnetic solid base catalysts were prepared by loading CaO on Fe 3 O 4 with Na 2 CO 3 and NaOH as precipitator, respectively. The optimum conditions for preparation of this catalyst were investigated. The influence of the proportion of Ca 2þ to Fe 3 O 4 on the catalytic performance has been studied. The catalyst with highest catalytic activity has been obtained when the proportion of Ca 2þ to Fe 3 O 4 is 7:1; the catalytic activity of the catalyst calcined from Ca(OH) 2 to Fe 3 O 4 is better than that calcined from CaCO 3 to Fe 3 O 4 ; under the conditions of methanol/oil molar ratio of 15:1, catalyst dosage of 2 wt% and temperature of 70 C, the biodiesel yield reaches to 95% in 80 min, even to 99% finally. The catalytic activity and recovery rate of the nanometer magnetic solid base catalysts are much better than those of CaO. Calcination temperature was determined by differential thermogravimetric analysis. Ca 2 Fe 2 O 5 , a kind of new metal multiple oxide, was found in the catalyst through X-ray diffraction. At the end, these catalysts were characterized by scanning electronic microscope (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM).
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