Magnetically recyclable basic polymeric ionic liquids for efficient transesterification of Firmiana platanifolia L.f. oil into biodiesel

Biodiesel, typically derived from non-edible vegetable oils via heterogeneous catalysts, is being deemed as a promising alternative to fossil fuels. Herein, basic polymeric ionic liquids (PILs) immobilized on magnetic mesoporous carrier (Fe₃O₄@SiO₂@SBA-15), FnmS-PILs, were synthesized through the facile radical polymerization and anion exchange methods, and were further utilized to catalyze transesterification of non-food feedstock-crude Firmiana platanifolia L.f. oil (CFPO, acid value of 1.20 mg KOH/g) into biodiesel directly. The characterization results demonstrated that FnmS-PILs with uniform core–shell structure, moderate surface area (153.2 m²/g), pore size (4.1 nm), strong magnetism (13.6 emu/g) and relative higher basicity (2.3 mmol/g) exhibited high catalytic performance, giving a high biodiesel yield of 92.8 wt% under mild reaction conditions (9/1 methanol/oil molar ratio, 4 wt% catalyst dosage at 85 °C for 5 h). Furthermore, kinetic study was also investigated accordingly, wherein the activation energy was found to be 51.6 kJ/mol along with a determined pseudo first order model. More importantly, the catalyst could be recovered easily by means of magnetic force and remained sufficiently active in five consecutive cycles. © 2017 Elsevier Ltd