A novel bimetallic CaFe-MOF derivative for transesterification: Catalytic performance, characterization, and stability

Metal organic frameworks (MOFs) are ideal precursors for the synthesis of catalysts with high surface areas and homogenously distributed active sites. Compared to monometallic MOFs, MOF-on-MOF strategy shows enhanced properties originating from the synergistic interactions between two metals at atomic level. In this study, a bimetallic CaFe-MOF was synthesized and exploited to obtain magnetic CaO catalyst, which was subsequently applied to catalyze transesterification for biodiesel production. The catalysts were characterized with thermogravimetric/derivative thermogravimetric analysis (TG/DTG), X-ray diffraction (XRD), Fourier Transform Infrared spectrometer (FTIR), N2 adsorption-desorption, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and Hammett indicator method. The as-synthesized catalysts exhibit excellent catalytic activity of 98.53 % with 6 wt% catalyst amount and 12 methanol/oil molar ratio at 65 °C in 1 h. The synthesized catalyst showed good stability even after 6 recycles with favorable transesterification conversions. Moreover, the as-synthesized catalyst type is highly tolerant to free fatty acid (FFA) and free water (FW), with transesterification conversions of 85.35 % and 86.27 % achieved with the FFA of 9 wt% and FW of 11 wt%, respectively. The physicochemical properties of the obtained biodiesel meet requirements of ASTM D6751 and EN 14214, indicating it can be directly used for transport fuel.