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

The CO 2 dynamic adsorption behaviors of the mesoporous carbon-supported solid amine adsorbents and their viability for low-concentration CO 2 capture were investigated in a fixed bed. The CO 2 diffusion, playing a dominate role on the CO 2 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 CO 2 inner pore diffusion. Moreover, the kinetic limitation to CO 2 diffusion within the amine films could be mitigated by the employment of a diffusion additive, which could facilitate the diffusion of CO 2 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 CO 2 and 2.25 mmol·g –1 for 400 ppm of CO 2 . The CO 2 adsorption capacity of the adsorbent increases significantly in the presence of moisture. The adsorbent also shows excellent stability for low-concentration CO 2 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 CO 2 diffusion on the adsorption kinetics and has very good prediction ability for low-concentration CO 2 adsorption on solid amine adsorbents.