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The Nature of Chemisorption and Physisorption of CO2 on Zeolite A


Title: The Nature of Chemisorption and Physisorption of CO2 on Zeolite A

Speaker: Niklas Hedin, Stockholm University

Venue: Lecture Room, 3rd floor, College of Chemistry and Chemical Engineering

Time: 16.00, Sept. 16, 2019

 

Abstract:

Zeolites are candidate materials for CO2 capture from gas mixtures, and the traditional zeolite A seems to be a good model system to study the interactions occurring on adsorption and desorption of CO2. Recently We have studied |Na12-x Kx|-A compositions that displayed a maximally enhanced CO2 – over – N2, and CO2 - over CH4 selectivity when x≈3. With in-situ X-ray diffraction studies, we determined that the cations were displayed into the a-cavities of the zeolite during adsorption of CO2. Additional in-situ neutron diffraction studies during the adsorption of CO2 allowed us to determine three site-specific adsorption isotherms of the physisorbed CO2, and an approximate position of the CO2 that had chemisorbed. More details of the chemical nature of the chemisorbed CO2 in zeolite |Na12K|-A were revealed by in-situ solid state NMR methods and in-situ IR spectroscopy. In contrast to what has sometimes been argued for, we showed that CO2 chemisorbed as mainly HCO3 - species without the involvement of the framework oxygen atoms. Under some conditions CO32- formed as well. About 6% of the adsorbed CO2 was chemisorbed at 1 bar and 273K.

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