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Hierarchically porous binder-free silicalite-1 discs: a novel support for all-zeolite membranes
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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2011 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 24, 8822-8828 p.Article in journal (Refereed) Published
Abstract [en]

Thermal expansion mismatch between the zeolite film and the support is an important cause for the formation of defects and cracks during the fabrication and use of zeolite membranes. We have studied how silicalite-1 discs with a permeability comparable to commercially available alumina supports can be produced by pulsed current processing (PCP) as a novel substrate for all-zeolite membranes. Hierarchically porous and mechanically strong membrane supports where the surface area and crystallography of the silicalite-1 particles were maintained could be obtained by carefully controlling the thermal treatment during PCP consolidation. In situ X-ray diffraction and dilatometry showed that the coefficient of thermal expansion (CTE) of the silicalite-1 substrate was negative in the temperature range 200-800 degrees C while the commonly used alumina substrate displayed a positive CTE. The critical temperature variation, Delta T, and thicknesses for crack-free supported zeolite films with a negative CTE were estimated using a fracture energy model. Zeolite films with a thickness of 1 mu m can only sustain a relatively modest Delta T of 100 degrees when supported onto alumina substrates while the all-zeolite membranes can support temperature variations above 500 degrees.

Place, publisher, year, edition, pages
2011. Vol. 21, no 24, 8822-8828 p.
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-66641DOI: 10.1039/c1jm10584aISI: 000291352900049OAI: oai:DiVA.org:su-66641DiVA: diva2:468374
Note

authorCount :5

Available from: 2011-12-20 Created: 2011-12-20 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Processing and performance of zeolites for efficient carbon dioxide separation
Open this publication in new window or tab >>Processing and performance of zeolites for efficient carbon dioxide separation
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We have structured zeolites from powders of zeolite 13X and 4A into hierarchically porous monoliths for efficient carbon dioxide capture by tailoring the pore dimensions to facilitate rapid gas uptake and release. Freeze-casting was used for the first time to shape adsorbents into a lamellar structure. Lamellar walls with thicknesses and spacing in the range of 10 µm were found to be the best combination between rapid gas transport and a short diffusion distance in the zeolite-containing walls for rapid carbon dioxide uptake and release.

Compressive strength measurements of the freeze-cast zeolite-based monoliths showed that monoliths with small pores, thin walls and a lot of interconnectivity between the walls were stronger than monoliths with large pores and thick walls. Image analysis of the structures together with modelling of the deformation behavior suggests that the failure mechanism of freeze-cast monoliths is dominated by buckling.

Binder-free zeolite Y and ZSM-5 -based monoliths were produced by pulsed current processing (PCP) into strong, hierarchically porous monoliths with minimal loss of crystallinity. Ranges for the maximum PCP processing temperatures for the zeolites with different aluminium contents were identified by powder x-ray diffraction (PXRD) with full-profile fitting analysis.

Matching the thermal expansion behavior of the supports with the zeolite film is important to minimize the risk of thermally induced cracking of zeolite membranes. Zeolite supports with a macroporous structure was prepared by PCP and the thermal expansion coefficient was determined by PXRD and compared to traditional alumina substrates. It was found that the slightly negative thermal expansion coefficient of the zeolite supports matched the thermal expansion of the zeolite films very well, whereas the alumina support would induce large stresses upon fluctuating temperatures.

Methylcellulose-directed synthesis of zeolite 4A produced nano-sized crystals with a narrow size distribution, which could be tuned by adjusting the methylcellulose content. The crystallinity of the synthesized 4A was controlled by PXRD and found to be very high, and the gas uptake capability performed well in comparison with available micron-sized zeolites.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2015. 69 p.
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-114160 (URN)978-91-7649-107-2 (ISBN)
Public defence
2015-03-27, Magnéli Hall, Arrhenius Laboratory, Svante Arrhenius Väg 16 B, Stockholm, 13:00 (English)
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Supervisors
Funder
Berzelii Centre EXSELENT
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Submitted.

Available from: 2015-03-05 Created: 2015-02-23 Last updated: 2015-12-02Bibliographically approved

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