Bronsted Acidic Ionic Liquid Modified Magnetic Nanoparticle: An Efficient and Green Catalyst for Biodiesel Production

Surface-functionalized magnetic nanoparticle supported dual Bronsted acidic ionic liquid was synthesized by immobilizing 1-(propyl-3-sulfonate) imidazolium hydrogen sulfate [SO3H-(CH2)(3)-HIM][HSO4] onto the surface of Fe3O4@SiO2 using 3-chloropropyltrimethoxysilane as the "linker". The structure of the catalyst was characterized by XRD, FT-IR, SEM, TEM, and VSM. The results demonstrated that the Fe3O4 particle was well retained in the silica matrix, presenting a core-shell structure with strong magnetic responsiveness. Meanwhile, the ionic liquid was successfully immobilized on the support. The as-prepared catalyst could disperse well in the reactants and showed good performance in esterification of oleic acid with short-chain alcohols and transesterification of soybean oil. Moreover, the catalyst could be easily separated from products by additional magnetic force without obvious mass loss and maintain satisfactory catalytic activity after being recycled eight times.