Valorization of waste chicken egg shells towards synthesis of heterogeneous catalyst for biodiesel production: Optimization and statistical analysis

Abstract The present research elucidates the synthesis of Zn/CaO catalyst from waste chicken egg shells and its application towards synthesis of biodiesel using waste frying oil (WFO) as a feedstock. The study also emphasizes on significant factor analysis and parametric optimization using Taguchi approach. The waste egg shells were calcined at 900 °C to obtain CaO and further loaded with Zn via wet incipient impregnation method. The engineered solid catalyst was characterized by thermogravimetric analysis (TGA), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), BET analyzer and X-ray diffraction (XRD). The Taguchi approach was employed to recognize factors affecting yield of biodiesel significantly. The variables considered for optimizing the transesterification process were reaction time, catalyst loading, methanol to oil ratio and reaction temperature. The produced biodiesel was examined experimentally for estimation of physicochemical properties. The observed optimum conditions were: reaction temperature 65 °C, catalyst loading 4 wt%, reaction time 150 min, and methanol to oil ratio 15:1 giving a maximum biodiesel yield of 93.27%. Taguchi method also revealed that contribution of catalyst concentration and reaction temperature has pronounced effect on biodiesel yield. Hence, the developed Zn/CaO catalyst from waste chicken egg shells could be considered as efficient and active catalyst for transesterification of waste frying oil towards biodiesel production.