Study on CO₂ Capture Characteristics and Kinetics of Modified Potassium-Based Adsorbents

In this paper, a silica aerogel support was prepared by two-step sol-gel method, and the active component K₂CO₃ was supported on the support by wet loading to obtain a modified potassium-based CO₂ adsorbent. As the influences of reaction conditions on the CO₂ capture characteristics of modified potassium-based adsorbents, the reaction temperature (50 °C, 60 °C, 70 °C, 80 °C), water vapor concentration (10%, 15%, 20%), CO₂ concentration (5%, 10%, 12.5%, 15%), and total gas flow rate (400 mL/min, 500 mL/min, 600 mL/min) were studied in a self-designed fixed-bed reactor. At the same time, the low-temperature nitrogen adsorption experiment, scanning electron microscope, and X-ray diffractometer were used to study the microscopic characteristics of modified potassium-based adsorbents before and after the reaction. The results show that the silica aerogel prepared by the two-step sol-gel method has an excellent microstructure, and its specific surface area and specific pore volume are as high as 838.9 m²/g and 0.85 cm³/g, respectively. The microstructure of K₂CO₃ loaded on the support is improved, which promotes the CO₂ adsorption performance of potassium-based adsorbents. The adsorption of CO₂ by potassium-based adsorbents can be better described by the Avrami fractional kinetic model and the modified Avrami fractional kinetic model, and it is a complex multi-path adsorption process, which is related to the adsorption site and activity. The optimal adsorption temperature, water vapor concentration, CO₂ concentration, and total gas volume were 60 °C, 15%, 12.5%, and 500 mL/min, respectively.