Dissertation
Selective Adsorption of Alcohol Molecules from Aqueous Solutions by Nanoporous Materials
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/108369
Abstract
Essential topological indices of the hydrogen-bond networks of water, methanol, ethanol, 1,2-propanediol and their binary mixtures adsorbed in silicalite-1 are analyzed and compared with their bulk liquid counterparts. These include the H-bond distribution, geodesic distribution (the shortest H-bond pathways between molecular vertices), the geodesic index between adsorbates, and the orientation and distance of the adsorbate to the interior of the zeolite. In combination, they describe how the H-bond networks are altered from the bulk to the confined silicalite-1 environment. The H-bond network analysis reveals that pure water forms long, contiguous chains at high loading while alcohol form small dimer/trimer. The binary water-alcohol mixture reveals the readiness of water co-adsorption with alcohol in silicalite-1. Selectivity decreases significantly with increasing alcohol concentration as the alcohol clusters serve as a adsorption sites for water.
Zeolitic imidazolate frameworks (ZIFs) have topologies that are characterized by the silicate zeolite architecture. Every accessible pore channel in ZIF is composed of cages (largest cavity diameter, LCD) connected with windows (pore limiting diameter, PLD). Grand-canonical Monte Carlo (GCMC) simulations have been used to examine the effect of systematic variation of the cage and window dimensions upon the selectivity (S) and performance (P) of a series of ZIFs: ZIF-10, ZIF-6, ZIF-64, ZIF-4, and EQOCOC. Within this series the cage and window sizes become sequentially smaller such that in the largest system (ZIF-10) water and alcohol are able to form small H-bonded clusters within the material, where each cluster is H-bonded to each other through the cage window; whereas in the smallest system (EQOCOC) only a single alcohol or water molecule can be accommodated within the cage, and H-bonding between the cages is minimized. Within EQOCOC and ZIF-4 the inability of the adsorbed alcohol to form H-bonds across cages dramatically reduced co-adsorption of water from binary water/alcohol mixtures. The performance metric PEtOH accounts for the loading Q inside the material (P = QS), and for EQOCOC and ZIF-4 range between 270 ~ 7,100 and 270 ~ 40,200. This is in comparison with the previous silicalite-1 results obtained with Gibbs ensemble Monte Carlo (GEMC) simulations wherein PEtOH spanned 50 ~ 330.
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Details
- Title
- Selective Adsorption of Alcohol Molecules from Aqueous Solutions by Nanoporous Materials
- Creators
- Chun-Hung Wang
- Contributors
- Aurora E. Clark (Advisor)Kerry W. Hipps (Committee Member)James A. Brozik (Committee Member)Soumik Banerjee (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 192
- Identifiers
- 99900581725101842
- Language
- English
- Resource Type
- Dissertation