In depth investigation of bi-functional, Cu/Zn/γ-Al2O3 catalyst in biodiesel production from low-grade cooking oil: Optimization using response surface methodology

Environmental concerns in fossil fuel depletion intensified the search for alternate fuel from renewable resources. The focus of this study is to produce biodiesel from low-grade cooking oil by using Cu/Zn/γ-Al2O3 as bi-functional heterogeneous base catalyzed transesterification reaction. The investigation of Cu/Zn/γ-Al2O3 catalyst on the calcination temperatures, dopant ratios to zinc oxide based and number of alumina coatings had significantly affected the catalytic performance. The physicochemical properties examined by XRD, XPS and TEM analyses over Cu/Zn/γ-Al2O3 catalyst indicates polycrystalline structure dominated by cubic Al2O3, hexagonal ZnO and monoclinic CuO species that presumably acted as active species which contributed to the catalytic transesterification of biodiesel. The design of experiments was performed using Box-Behnken design coupled with response surface methodology in order to optimize Cu/Zn (10:90)/γ-Al2O3 catalyst preparation conditions. The experimental value achieved 88.82% production of biodiesel that closely agreed with the predicted value from RSM.