Facile synthesis of spray pyrolysis-derived CuCl/γ-Al2O3 microspheres and their properties for CO adsorption and CO/CO2 separation

Abstract In this study, we developed a facile and scalable preparation method of CuCl@γ-Al2O3 composite microspheres for CO storage and separation by combining sol-gel and spray pyrolysis methods, followed by metal salt impregnation. γ-Al2O3 microspheres were first prepared by spray pyrolysis of a mixture containing various ratios of boehmite sol and citric acid (CA). Pore-size distribution analyses indicated that the mesopores that are generated inside of the γ-Al2O3 microspheres and their pore volumes could be fine-tuned by adjusting the CA/boehmite ratio. Importantly, the newly formed pore structures have been identified to accelerate the thermal dispersion of CuCl species into the γ-Al2O3 matrix, resulting in improved CO sorption. Gas-adsorption experiments showed that CO-adsorption capacity and CO/CO2 selectivity were strongly affected by the CA/boehmite ratio, CuCl-dispersion temperature, and CuCl-loading amount. The optimized adsorbent exhibited a maximum CO-adsorption capacity of 1.69 mmol g−1 and CO/CO2 selectivity of 84 (at 25 °C and 100 kPa), exceeding the benchmarks for CO-selective adsorbents. Moreover, the spherical CuCl@γ-Al2O3 adsorbent showed good regenerative ability after a number of adsorption–desorption cycles. This study provided facile and scalable synthesis method for low-cost CO-selective material with high CO performance.