Sustainable hollow spherical CaO derived from waste eggshells for transesterification of lard: Catalytic characterization, performance and thermodynamics

This study presents a novel method for synthesizing a highly efficient hollow spherical CaO catalyst derived from waste eggshells. The catalyst was prepared through soft template method and thermal treatment under controlled nitrogen atmosphere, yielding a unique hollow spherical structure that significantly enhances catalytic activity. The catalyst characterization was performed with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and N2 adsorption-desorption. The results showed that the hollow spherical textural catalysts with specific surface area of 4.3 m2 g−1 were obtained at Ca2+ concentration of 0.05 mol L−1, and possessed excellent catalytic performance in the preparation of biodiesel by transesterification of lard with anhydrous methanol. An exceptional biodiesel yield of 96.41 % was achieved under optimized conditions of catalyst concentration of 2 wt%, reaction temperature of 65 °C, methanol/oil molar ratio of 12:1, and reaction time of 120 min. This catalyst exhibited longer lifespan and significant catalytic activity (Biodiesel yield >89.65 %) after being used for four cycles. The transesterification obeyed the pseudo-first-order kinetics with an activation energy of 53.23 kJ mol−1 for the hollow CaO catalyst. This approach sets itself apart from previous methods by employing sustainable, low-cost materials and achieving high reusability, advancing the field of renewable energy with minimal environmental impact.