Biodiesel production from soybean oils by a novel nano-magnetic solid base catalyst (K/ZrO2/γ-Fe2O3)

Abstract

Biodiesel is emerging as a green alternative source to fossil fuels due to its clean and renewable advantages. In this study, a nano-solid base catalyst (K/ZrO₂/γ-Fe₂O₃) with weak magnetism was successfully synthesized and investigated for transesterification of soybean oil to produce biodiesel. The obtained catalyst was fully characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermogravimetry/differential scanning calorimetry device (TG/DSC), and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis. Results showed that the nano-magnetic catalyst had granular nano-structures with particle sizes of 15–25 nm. The optimum conditions for transesterification were shown to be as follows: catalyst added amount of 5 wt%; methanol/oil molar ratio of 10 : 1; reaction time of 3.0 h, and reaction temperature of 65 °C, and the yield of biodiesel could reach above 93.6 wt%. The reusability of the magnetic catalyst demonstrated that the magnetic catalyst was ferromagnetic and still maintained high catalytic activity after six times' reuse. The formed core–shell was hard to separate even after stirring in liquid phase reactions, which was favorable for use in biodiesel production. The developed nano-magnetic catalyst shows a potential application for biodiesel production in a green manner.