Core-shell magnetic nanomaterial grafted spongy-structured poly (ionic liquid): A recyclable brönsted acid catalyst for biodiesel production

Construction of an efficient and separable Bronsted acid catalyst to realize one-pot conversion from low-value oils to biodiesel has been a hot and difficult spot in recent years. Herein, a novel magnetically recyclable catalyst was fabricated by grafting the sponge-like structure of poly (ionic liquid) on the surface of support Fe₃O₄/SiO₂. The grafting copolymerization of dual-acidic ionic liquid (sulfonated vinylimidazolium ionic liquid) on the Fe₃O₄/SiO₂ was beneficial to enhance the strong acidity of the magnetic carrier and also made dual-acidic ionic liquid own excellent separation characteristics. The characterization results of the prepared composite showed that a sponge-like structure of poly(ionic liquid) was wrapped on the outer surface of Fe₃O₄@SiO₂, thereby providing more active sites to reactants. Meanwhile, the catalyst possessed high magnetization value (14.3 emu/g) that resulted in the simple and rapid separation from the reaction system through an external magnetic field. Benefiting from the synergy effect between dual-acidic poly(ionic liquids) and magnetic carrier, Fe₃O₄@SiO₂@PIL exhibited good catalytic performance with the oleic acid conversion of 92.1 % and the methyl oleate yield of 92.1 %. Besides, the recycled catalyst showed no significant loss in the catalytic activity after repeated use for six times.