文摘
We have synthesized sulfamic acid and sulfonic acid functionalized silica-coated crystalline Fe/Fe3O4 core/shell magnetic nanoparticles (MNPs), which exhibited excellent stability. We have studied their catalytic activities with respect to the esterification of oleic acid and the transesterification of glyceryl trioleate as model reactions for biodiesel production. Both acid-functionalized MNPs demonstrated excellent catalytic activities in the reaction of esterification of oleic acid. However, the sulfamic acid functionalized MNPs showed better reactivity in the reaction of transesterification of glyceryl trioleate. Both acid-functionalized MNPs can be recovered by magneto-precipitation. The sulfamic acid functionalized MNPs retained high reactivity (>95% conversion) throughout 5 continuous runs of reactions, indicating their potential for biodiesel production from low grade feedstock, such as waste cooking oil, containing a high level of free fatty acids.