Preparation of biodiesel from waste frying oil using a green and renewable solid catalyst derived from egg shell

Biodiesel was produced from waste frying oil using calcium oxide derived from the calcination of egg shell as a heterogeneous base catalyst. The catalyst was characterized by X‐ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller analysis, scanning electron microscopy, and energy‐dispersive atomic X‐ray spectrometry. The effects of reaction variables such as methanol/oil molar ratio, amount of catalyst, reaction temperature, and reaction time on biodiesel yield were investigated. The activity of the egg shell‐derived CaO was compared with the commercial CaO. A high biodiesel yield of 95.05% and conversion of 96.11% were obtained at 3 wt % catalyst (based on oil weight), methanol/oil molar ratio of 9:1, reaction temperature of 65°C, and reaction time of 3 h. The structure of biodiesel was characterized by FTIR, and the biodiesel conversion was determined by 1H nuclear magnetic resonance spectroscopy.