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Understanding Carbon Dioxide Adsorption on Univalent Cation Forms of the Flexible Zeolite Rho at Conditions Relevant to Carbon Capture from Flue Gases

DOI: 10.1021/ja3070864 DOI Help

Authors: Magdalena M. Lozinska (EaStCHEM School of Chemistry, University of St. Andrews) , Enzo Mangano (Institute for Materials and Processes, University of Edinburgh) , John P. S. Mowat (EaStCHEM School of Chemistry, University of St. Andrews) , Ashley M. Shepherd (University of Aberdeen) , Russell F. Howe (University of Aberdeen) , Stephen P. Thompson (Diamond Light Source) , Julia E. Parker (Diamond Light Source) , Stefano Brandani (Institute for Materials and Processes, University of Edinburgh) , Paul A. Wright (EaStCHEM School of Chemistry, University of St. Andrews)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Chemical Society , VOL 134 (42) , PAGES 17628 - 17642

State: Published (Approved)
Published: October 2012

Abstract: A series of univalent cation forms of zeolite Rho (M9.8Al9.8Si38.2O96, M = H, Li, Na, K, NH4, Cs) and ultrastabilized zeolite Rho (US-Rho) have been prepared. Their CO2 adsorption behavior has been measured at 298 K and up to 1 bar and related to the structures of the dehydrated forms determined by Rietveld refinement and, for H-Rho and US-Rho, by solid state NMR. Additionally, CO2 adsorption properties of the H-form of the silicoalumino-phosphate with the RHO topology and univalent cation forms of the zeolite ZK-5 were measured for comparison. The highest uptakes at 0.1 bar, 298 K for both Rho and ZK-5 were obtained on the Li-forms (Li-Rho, 3.4 mmol g–1; Li-ZK-5, 4.7 mmol g–1). H- and US-Rho had relatively low uptakes under these conditions: extra-framework Al species do not interact strongly with CO2. Forms of zeolite Rho in which cations occupy window sites between ?-cages show hysteresis in their CO2 isotherms, the magnitude of which (Na+,NH4+ < K+ < Cs+) correlates with the tendency for cations to occupy double eight-membered ring sites rather than single eight-membered ring sites. Hysteresis is not observed for zeolites where cations do not occupy the intercage windows. In situ synchrotron X-ray diffraction of the CO2 adsorption on Na-Rho at 298 K identifies the adsorption sites. The framework structure of Na-Rho “breathes” as CO2 is adsorbed and desorbed and its desorption kinetics from Na-Rho at 308 K have been quantified by the Zero Length Column chromatographic technique. Na-Rho shows much higher CO2/C2H6 selectivity than Na-ZK-5, as determined by single component adsorption, indicating that whereas CO2 can diffuse readily through windows containing Na+ cations, ethane cannot.

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction

Added On: 10/01/2013 13:50

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