Fe_3O_4-SiO_2负载型磷钼杂多酸催化制备生物柴油

Synthesis of biodiesel over Fe_3O_4-SiO_2 supported phosphomolybdic heteropoly acid catalyst

利用共沉淀法制备分散性好、比表面积大和磁性强的Fe2O4磁粒颗粒。以正硅酸乙酯为前驱体，对Fe3O4磁粒子表面进行改性，制备了Fe3O4-SiO2磁性粒子。以Fe3O4-SiO2为磁性载体，利用溶胶-凝胶法将强酸性的磷钼杂多酸负载于磁性颗粒中，制得微米级磁载杂多酸催化剂。利用X射线粉末衍射、红外光谱、扫描电子显微镜和电子能谱等分析测试手段，对催化剂进行了结构表征。结果表明，磷钼酸包覆在SiO2微孔孔壁中，保持了Keggin结构，确保其在催化反应中有较高活性。以酯转化率作为评价磁载杂多酸催化活性的指标，以餐饮业废油为原料，利用L9（3^4）正交表进行正交实验，得出生物柴油的最佳制备条件：反应温度55℃，催化剂用量为废油质量的2％，反应5h，在此条件下，酯化率达85．11％。

Fe3O4 particles with good dispersion, large surface area and strong magnetism were prepared by coprecititation method and modified using TEOS as the precursor to form Fe3O4-SiO2 particles. Micron-sized magnetic heteropolyacid catalyst was prepared by loading phosphomolybdic heteropoly acid on the magnetic particles by sol-gel method and characterized by means of IR, XRD, SEM and EDS. The results showed that the phosphomolybdic heteropoty acid dispersed on the wall of micropores of SiO2 and kept Keggin structure, which ensured its high catalytic activity. L9 （3^4） orthogonal experiment was carried out for esterification of waste oil from catering industry using the magnetic heteropolyacid as the catalyst, with esterification rate of 85.11% under optimal condition as follows ： reaction temperature 55 ℃, catalyst dosage = 2% of mass of the waste oil, reaction for 5 h.