Sustainable biodiesel production from low-quantity oils utilizing H6PV3MoW8O40 supported on magnetic Fe3O4/ZIF-8 composites

Abstract The development of efficient and reusable catalysts is desired to improve biodiesel production process. For this purpose, the magnetic Fe3O4/ZIF-8 composites were first prepared by incorporating ZIF-8 MOF into Fe3O4 nanoparticles through in-situ approach, and then a vanadium-substituted heteropolyacid (HPA), H6PV3MoW8O40, was encapsulated in the support to afford the solid catalyst. The so-prepared catalysts were characterized by using XRD, FT-IR, TEM, SEM, TG, VSM, and nitrogen porosimetry measurement. Results revealed that the Fe3O4/ZIF-8 support was really formed, and the HPAs had been loaded on the magnetic composite. The catalytic performances of the developed catalysts were evaluated for the heterogeneous biodiesel production from the low-quantity oils. This catalyst had good magnetic responsiveness, and could catalyze the transesterification of soybean oil and esterification of free fatty acids (FFAs) simultaneously, thus achieving one-step transformation of triglycerides and FFAs to biodiesel in a heterogeneous manner. The transesterification conversion obtained was 92.6% with 30:1 methanol/oil molar ratio at a catalyst loading of 6 wt% and reaction temperature of 160 °C for 10 h. Moreover, the solid catalyst could be recycled by an external magnet, and displayed a good reusability with a minimal mass loss and a slight decrease in the activity after reuse for five runs. This protocol showed great potential for sustainable biodiesel production from the low-quantity oils due to the pronounced activity and good reusability of the solid catalyst.