(600g) A Comprehensive Overview of the Stability of Amine-Functionalized Carbon Dioxide Adsorbents | AIChE

(600g) A Comprehensive Overview of the Stability of Amine-Functionalized Carbon Dioxide Adsorbents


Jahandar Lashaki, M. - Presenter, Florida Atlantic University
Sayari, A., University of Ottawa
This overview focuses on important stability issues facing amine-functionalized CO2 adsorbents, including amine-grafted and amine-impregnated silicas, zeolites, metal-organic frameworks, and carbons. Adsorptive CO2 capture, particularly by amine-functionalized materials, from typical gas streams such as flue gas, biogas, flare gas, syngas and ambient air has attracted tremendous attention from the scientific community and industry alike. Owing to the exceedingly large volumes of CO2 emissions, large-scale adsorption processes involving large amounts of materials are required. To achieve economic viability, adsorbent materials should have (i) high CO2 capacity within a desired range of temperature, (ii) high selectivity for CO2, and (iii) fast adsorption kinetics while being readily regenerable. In addition, they should be cost-effective and stable over many thousands of adsorption-desorption cycles. Adsorbent stability is a multifaceted issue that includes long-term thermal, hydrothermal, chemical, and mechanical stability. Clearly, the stability of CO2 adsorbents is of utmost importance since it controls the lifespan of the material. This is particularly crucial for CO2 capture since the recovered CO2 has often low commercial value, requiring low-cost separation technologies. Despite the importance of adsorbent stability, the great majority of CO2 adsorption studies focused on adsorption equilibrium or near-equilibrium properties, kinetics, and selectivity, often using highly pure CO2 and CO2/N2 or CO2/CH4 gas mixtures to simulate flue gas or biogas and natural gas.

Adsorbent stability issues may be associated with the feed gas composition and/or the adsorption process operational conditions. Ubiquitous impurities such as water vapor, sulfur-containing compounds such as sulfur oxides (SOx), hydrogen sulfide (H2S) and carbonyl sulfide (COS), nitrogen oxides (NOx), and oxygen (O2) are often present in actual feed gases. Therefore, the impact of such feed gas components on the adsorbent performance should be assessed. On a separate front, adsorbent materials may be exposed to harsh operational conditions during cyclic adsorption-desorption processes. This may include elevated desorption temperatures in temperature swing adsorption (TSA) processes, steam regeneration of CO2-loaded adsorbents, and air exposure during adsorbent cooling after regeneration. This will require high thermal stability and high resistance to steam treatment and oxidative degradation. Herein, 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 will be discussed. Moreover, 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 will be provided. Specific measures to address outstanding stability issues will be discussed.