Magnetic Fe3O4/MCM-41 composite-supported sodium silicate as heterogeneous catalysts for biodiesel production

This study aims at the development of magnetically recyclable solid catalysts for the production of biodiesel. To achieve this, the magnetically susceptible Fe3O4/MCM-41 composites with core-shell structure were prepared, and sodium silicate was then supported on the magnetic materials by using epichlorohydrin as a cross-linking reagent. The core-shell structured magnetic support and so-prepared solid catalyst were characterized by various techniques. Characterization results showed that the sodium silicate was chemically bridged onto the Fe3O4/MCM-41 composites without obvious damage to the structure of the magnetic support. The solid catalyst exhibited a strong magnetic response and displayed extraordinary catalytic activities in the transesterification of soybean oil for the production of biodiesel, with the oil conversion reaching 99.2% by using the methanol-to-oil molar ratio of 25:1 and catalyst loading of 3 wt% at reflux of methanol after 8 h of reaction. Moreover, the separation of the solid catalyst from reaction mixture was readily achieved by simple magnetic decantation without obvious mass loss, and the solid catalyst could be reused for five times for the heterogeneous transesterification.