Stability of amine-functionalized CO₂ adsorbents: a multifaceted puzzle

This review focuses on important stability issues facing amine-functionalized CO2 adsorbents, including amine-grafted and amine-impregnated silicas, zeolites, metal-organic frameworks and carbons. During the past couple of decades, major advances were achieved in understanding and improving the performance of such materials, particularly in terms of CO2 adsorptive properties such as adsorption capacity, selectivity and kinetics. Nonetheless, to pave the way toward commercialization of adsorption-based CO2 capture technologies, in addition to other attributes, adsorbent materials should be stable over many thousands of adsorption-desorption cycles. Adsorbent stability, which is of utmost importance as it determines adsorbent lifetime and operational costs of CO2 capture, is a multifaceted issue involving thermal, hydrothermal, and chemical stability. Here we discuss the impact of the adsorbent physical and chemical properties, the feed gas composition and characteristics, and the adsorption-desorption operational parameters on the long-term stability of amine-functionalized CO2 adsorbents. We also review important insights associated with the underlying deactivation pathways of the adsorbents upon exposure to high temperature, oxygen, dry CO2, sulfur-containing compounds, nitrogen oxides, oxygen and steam. Finally, specific recommendations are provided to address outstanding stability issues.