Flue gas treatment via CO₂ adsorption

Adsorption separation has gained considerable attention as a viable alternative to the currently used, high energy-demanding aqueous amine scrubbing technologies. This review is a summary of the main contributions regarding the development of new adsorbents for post-combustion CO₂ capture. Emphasis has been placed on materials evaluated at representative flue gas conditions of CO₂ partial pressure (i.e., 0.05-0.2 bar) and temperature (25-75°C). Whenever possible, the effect of moisture on the adsorbent stability and CO₂ uptake is included, although relatively few studies in the literature have focused on this issue. This review includes adsorbents produced by modification of existing commercial materials as well as newly developed materials. These adsorbents were separated in two major classes, namely (i) physical adsorbents including carbons, zeolites and metal-organic frameworks and (ii) chemical adsorbents, i.e., amine-functionalized materials. A critical analysis of the literature is provided with the aim of tracing the main paths currently pursued toward the development of suitable CO₂ adsorbents and to provide a general overview of the advantages and limitations of each family of adsorbents.