Study on simplifying the synthesis method of CaO/ZrO2 catalyst and optimizing its performance in catalytic transesterification to prepare biodiesel

This study focused on the optimized preparation of biodiesel over a ZrO 2 -modified CaO catalyst. CaO/ZrO 2 catalysts were synthesized by impregnation, co-precipitation, and sol-gel methods, and analyzed by various characterization methods, including N 2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermally programmed desorption of CO 2 (CO 2 -TPD), and scanning electron microscopy (SEM). The CaO/ZrO 2 catalyst synthesized by the impregnation method had a uniform microstructure, good crystallinity, a uniform spherical particle structure with large pores and slits, and a density of surface alkali sites of 1.898 mmol g - 1 . Using the impregnation method, the best synthesis conditions were determined as a calcination temperature of 700 °C and a Ca/Zr molar ratio of 3:2. Furthermore, the optimal reaction conditions were determined by single-factor experiments as a catalyst dosage of 8 wt%, a molar ratio of methanol to oil of 12, a reaction temperature of 64 °C, and a reaction time of 2 h. Under these reaction conditions, the yield of fatty acid methyl esters (FAME) reached 95.9 %, decreasing only marginally to 77.6 % after four reuses of the catalyst. It is hoped that this study may provide important research guidance for developing solid basic catalysts for preparing FAME by transesterification under mild conditions.