Zeolite coatings and composites (DOC)

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					 Structured zeolite containing composite materials – preparation
                          and properties

                                    Prof. W. SCHWIEGER
                                     Chemical Reaction Engineering
                          Friedrich-Alexander-University Erlangen-Nuremberg


       Since the late eighties, there has been a rising interest in the development of zeolite
coatings. Zeolite coatings are defined as composite materials, comprising a carrier on which
zeolite crystals are physically or chemically bonded. Supporting zeolite onto carriers or
substrates of different nature, composition and structure/architecture represents a great
improvement concerning the technical applicability of zeolitic materials in traditional and
emerging fields like catalysis, adsorption, separation and sensors. The zeolite-supported
composite leads to performances that are beyond the limitations of unsupported zeolites, by
adding mechanical strength, a structuring function and novel functionalities. Indeed, the
combination of different materials (zeolite and carrier) with different properties can lead to
important synergies, allowing for the manufacturing of multifunctional composites, and
broadening the range of applications of zeolitic materials.
       The aim of the contribution is to offer an overview on special coating techniques,
highlighting their synthesis, properties, and potential applications.
       Hierarchical porous structures1,2, combining the benefits of different pore-size
regimes. Materials with combinations of micro-/mesopores4, micro-/macropores5, meso-
/macropores6 or porosity spreading up to the three orders7 have been synthesized, generally
employing two different approaches. Template-directed synthesis utilizes the inherent
porosity of temporary/sacrificial templates (artificial or biological) to structure hierarchical
porous inorganic frameworks by an imprinting process8. Differently, the coating approach
yields hierarchical porous composites by deposition or in-situ synthesis of micro- or meso-
porous frameworks onto porous carriers9,10.
       In the development of hierarchical porous structure, zeolites1 are playing a major role.
Many efforts have been concentrated in realizing supported zeolite films for membrane
technology11 and zeolite composites or coatings for catalytic and adsorption application12. The
great number of different porous carriers which can be used and the huge number of zeolite
types make it possible to finely tailor materials for specific technical applications10,13. More
recently interests have been also given to self-supporting porous zeolitic frameworks14,
leading also to the development of hierarchical bioinspired architectures, utilizing zeolites as
building blocks to mimic natural or biological architectures3,15.
References

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     Hierarchical Porous Materials: Towards Tunable Size- and Shape-Selective Microcavities in
     Nanoporous Channels, Angewandte Chemie International Edition 39, 2702-2707 (2000).
 3. Valtchev, V., Smaihi, M., Faust, A. C. & Vidal, L. Biomineral-silica-induced zeolitization of
     Equisetum Arverse, Angew. Chem. Int. Ed. 42, 2782-2785 (2003).
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     variable macropore architectures, Adv. Mater. 13, 1259-1263 (2001).
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     Preparation and catalytic testing of zeolite coatings on preshaped alumina supports, Microporous
     Mesoporous Mater. 27, 95-106 (1999).
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     gestützen Zeolithschichten, Pat. Appl. DE10304322.5 (2002); Lai, Z. et al. Microstructural
     optimization of a zeolite membrane for organic vapor separation, Science 300, 456-460 (2003).
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     porous glass beads into MFI-type containing beads, Microporous Mesoporous Mater. 55, 181-191
     (2002); Katsuki, H. & Furuta, S. Formation of novel ZSM-5/porous mullite composite from
     sintered kaolin honeycomb by hydrothermal reaction, J. Am. Ceram. Soc. 83, 1093-1097 (2000).
13. Seijger, G. B. F., Oudshoorn, O. L., Boekhorst, A., van Bekkum, H., van den Bleek, C. M. &
     Calis, H. P. A., Selective catalytic reduction of NOx over zeolite-coated structured catalyst
     packings, Chem. Eng. Sci. 56, 849-857 (2001); Cybulski, A. & Moulijn, J. A. Structured Catalysts
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     (2002).
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     wood cell templating, Adv. Mater. 14, 926-929 (2002); Daw, R. Zeolite branch out, Nature 418,
     491 (2002); Anderson, M. W., Holmes, S. M., Hanif, N. & Cundy, C. Hierarchical pore structures
     through diatom zeolitization, Angew. Chem. Int. Ed. 39, 2707-2710 (2000).

				
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