Direct Capture of Low-Concentration CO2 on Mesoporous Carbon-Supported Solid Amine Adsorbents at Ambient Temperature

The CO2 dynamic adsorption behaviors of the mesoporous carbon-supported solid amine adsorbents and their viability for low-concentration CO2 capture were investigated in a fixed bed. The CO2 diffusion, playing a dominate role on the CO2 reaction-adsorption process, was addressed from the following two strategies: improving the support and facilitating the kinetic diffusion. The well-developed mesoporous carbon framework could accommodate high content of polymer amine polyethylenimine (PEI) while maintaining considerable residual channels for CO2 inner pore diffusion. Moreover, the kinetic limitation to CO2 diffusion within the amine films could be mitigated by the employment of a diffusion additive, which could facilitate the diffusion of CO2 into the internal PEI films. The as-prepared MC-based solid amine adsorbents exhibit remarkable adsorption capacities of 3.34 mmol·g–1 for 5000 ppm of CO2 and 2.25 mmol·g–1 for 400 ppm of CO2. The CO2 adsorption capacity of the adsorbent increases significantly in the presence of moisture. The adsorbent also shows excellent stability for low-concentration CO2 capture during the temperature swing adsorption/desorption cycling operation. The experimental breakthrough curves under various conditions were analyzed successfully using the deactivation model. The first-order kinetic deactivation model can be applied extensively to analyze the effect of CO2 diffusion on the adsorption kinetics and has very good prediction ability for low-concentration CO2 adsorption on solid amine adsorbents.