Unconventional, Highly Selective CO2 Adsorption in Zeolite SSZ-13

• Published in: Journal of the American Chemical Society Vol. 134; no. 4; pp. 1970 - 1973
• Main Authors: Hudson, Matthew R, Queen, Wendy L, Mason, Jarad A, Fickel, Dustin W, Lobo, Raul F, Brown, Craig M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.02.2012
• Subjects: Adsorption; Carbon Dioxide - chemistry; Models, Molecular; Surface Properties; Zeolites - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja210580b

Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO2 from N2, the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO2 was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO2 over N2 selectivity to differences in binding sites for the two gases, where the primary CO2 binding site is located in the center of the 8-membered-ring pore window. This CO2 binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO2 over N2 in SSZ-13 and other zeolites containing 8-ring windows.