Kinetic model describing the effect of amine loading and temperature on CO2 capture by solid amine adsorbent

The increasing CO₂ concentration in atmosphere leads to significant ecological changes, and the control of CO₂ emissions has been a major concern worldwide. Amine-functionalized adsorbents are promising because they have high CO₂ adsorption capacity, moderate adsorption heat and strong water resistance. Adsorption kinetics is a key performance parameter and facilitates the cognizance of microscopic CO₂ adsorption process. A novel kinetic model was proposed, which categorized the amines of solid amine adsorbents into two regions: the open amine region and the closed amine region. Different from the open amine region, CO₂ adsorption by amines in the closed amine region was significantly influenced by diffusion. The model could elucidate the effect of amine loading and temperature on CO₂ adsorption. When amine loading was below the theoretical maximum loading, the CO₂ adsorption capacity and the N efficiency gradually increased with the rise of amine loading. Nevertheless, as the amine loading further increased, the adsorption capacity decreased instead. CO₂ adsorption by solid amines was not affected by external diffusion, but was significantly affected by internal diffusion. The percentage of closed amine region of adsorbents with high amine loading was large, CO₂ needed to diffuse slowly into this region, leading to a small CO₂ adsorption capacity at low temperature. When the amine loading was less than 0.5, the CO₂ adsorption rate stayed almost the same. The model is instructive for the targeted preparation of solid amine adsorbents with fast adsorption rates.