Preparation of novel nanoporous layered silicates by swelling of AMH-3 and their use in nanocomposite membranes for gas separation

2008 2008

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Abstract (summary)

Nanoporous layered materials can be described as a class of lamellar solids that have an intermediate structure between layered materials (e.g., clays) and nanoporous frameworks (e.g., zeolites). Among these, nanoporous layered silicates have been studied for various industrial applications since the rich intercalation chemistry of clays can be applied to yield their swollen and exfoliated derivatives. Their pore connectivity in the direction perpendicular to the layers has been expected to provide an ability of molecular recognition based on the size of permeating species. These unique structural characteristics are important in the membrane industry because the molecular sieving of permeable nanolayers, if exfoliated and incorporated in polymers, is able to enhance the separation properties of polymeric membranes. AMH-3, a layered silicate built of nanoporous layers and interlayer space occupied by cations and water molecules, has been known to have a unique three-dimensional eight membered-ring (8 MR) pore system. Due to its unique porosity, it has been proposed to use exfoliated layers of AMH-3 as a selectivity-enhancing additive in polymers for small molecule separation. However, experimental procedures for the AMH-3 swelling, required for the nanocomposite demonstrated.

This research reveals a novel process for AMH-3 swelling, involving the sequential intercalation of surfactant molecules following proton exchange of interlayer cations in the presence of amino acids. Structural information of swollen AMH-3 is investigated using various characterization techniques and the emergence of structural changes indicates that it should be considered as a new nanoporous layered silicate rather than a simple intercalated derivative. Consequently, polymeric nanocomposites incorporating the nanoparticles of swollen AMH-3 are fabricated by solution blending. These nanocomposite membranes present substantial improvements of the hydrogen/carbon dioxide ideal selectivity more than by a factor of three compared to that of polymer. This becomes the first experimental demonstration on the concept of the polymer/nanoporous layered material nanocomposite membranes. It also suggests that, by incorporating these nanoscale sieves in the skin layers of hollow fiber membranes, this approach can be a commercially-attractive strategy to improve the performance of the polymeric membranes dominating the current gas separation market.

Indexing (details)

Materials science
0794: Materials science
Identifier / keyword
Applied sciences; Gas separation; Layered materials; Membranes; Nanocomposites; Nanoporous materials; Silicates; Swelling
Preparation of novel nanoporous layered silicates by swelling of AMH-3 and their use in nanocomposite membranes for gas separation
Choi, Sunho
Number of pages
Publication year
Degree date
School code
DAI-B 69/07, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Tsapatsis, Michael
University of Minnesota
University location
United States -- Minnesota
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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