Ethanol and Water Adsorption in Conventional and Hierarchical All-Silica MFI Zeolites
[2];
[4];
[5];
[3]
- Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455-0132, United States
- Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States, Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455-0132, United States
- Facility for Adsorbent Characterization and Testing, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Department of Chemical Biomolecular Engineering and Institute for NanoBiotechnology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States, Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, Maryland 20723-6099, United States
Hierarchical zeolites containing both micro- (<2 nm) and mesopores (2–50 nm) have gained increasing attention in recent years because they combine the intrinsic properties of conventional zeolites with enhanced mass transport rates due to the presence of mesopores. The structure of the hierarchical self-pillared pentasil (SPP) zeolite is of interest because all-silica SPP consists of orthogonally intergrown single-unit-cell MFI nanosheets and contains hydrophilic surface silanol groups on the mesopore surface while its micropores are nominally hydrophobic. Therefore, the distribution of adsorbed polar molecules, like water and ethanol, in the meso- and micropores is of fundamental interest. Here, molecular simulation and experiment are used to investigate the adsorption of water and ethanol on SPP. Vapor-phase single-component adsorption shows that water occupies preferentially the mesopore corner and surface regions of the SPP material at lower pressures (P/Po < 0.5) while loading in the mesopore interior dominates adsorption at higher pressures. In contrast, ethanol does not exhibit a marked preference for micro- or mesopores at low pressures. Liquid-phase adsorption from binary water–ethanol mixtures demonstrates a 2 orders of magnitude lower ethanol/water selectivity for the SPP material compared to bulk MFI. For very dilute aqueous solutions of ethanol, the ethanol molecules are mostly adsorbed inside the SPP micropore region due to stronger dispersion interactions and the competition from water for the surface silanols. At high ethanol concentrations (CEtOH > 700 g L–1), the SPP material becomes selective for water over ethanol.
- Research Organization:
- Univ. of Minnesota, Twin Cities, MN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Advanced Research Projects Agency - Energy (ARPA-E)
- Grant/Contract Number:
- FG02-17ER16362; SC0001004; 1208-0000
- OSTI ID:
- 1971539
- Alternate ID(s):
- OSTI ID: 1856483
- Journal Information:
- ACS Physical Chemistry Au, Journal Name: ACS Physical Chemistry Au Vol. 2 Journal Issue: 2; ISSN 2694-2445
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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