Zeolites nanostructured materials

Self-assembly processes in nature are sometimes catalyzed by enzymes. Zeolites are, in many ways, the inorganic counterparts of enzymes, with their ability to selectively bind other substances and perform catalysis. Can templates or catalysts be effective in increasing rates and reducing defects in a wide range of nanostructured materials ... 

Dr. Rolison is a member of the American Chemical Society, AAAS, the International Zeolite Association, the Materials Research Society, and the Society for Electroanalytical Chemistry (SEAC). She wrote Ultramicroelectrodes, the first textbook in this very active research area of electrochemistry, with Martin Fleischmann, Stanley Pons, and Peter Schmidt. She and Henry White guest-edited an issue of Langmuir devoted to the electrochemistry of nanostructured materials (February 1999). Dr. Rolison was a member of the Advisory Board for Analytical Chemistry and is a current member of the editorial boards of the Journal of Electroanalytical Chemistry and Langmuir. She is a member of the Board of Directors for the SEAC and has served since 1997 as editor of the society s newsletter, SEAC Communications. 

In this paper, we first discuss the role of SDAs in the hydrothermal syntheses of zeotypes (part 2) and then present some examples of the preparation of advanced materials based on zeolites (part 3). In part 4, recent work from our group that uses fianctional organometallic complexes to directly synthesize nanostructured materials will be presented. 

Reviews covering this diverse area are available.[110,111] The former review covers the photochemistry of nanostructured materials (including zeolites) for energy applications, the latter the preparation and properties of chromophores in porous silica and minerals such as zeolites. 

They were named zeolite ( boiling stone ) in 1756 by Cronstedt, a Swedish mineralogist, who observed their emission of water vapor when heated. At the other size limit, opals constitute another example of a naturally occurring nanostructured material. These gems are made up mainly of spheres of amorphous silica with sizes ranging from 150 nm to 300 nm. In precious opals, these spheres are of approximately equal size and can thus be arranged in a three-dimensional periodic lattice. The optical interferences produced by this periodic index modulation are the origin of the characteristic iridescent colors (opalescence). 

In parallel to developments in the field of electronics, nanostructured materials have been developed by materials scientists and chemists also. The concept of nanocrystaUine structures emerged in the field of materials science, and polycrystals with ultrafine grain sizes in the nanometer range have been produced. These nanophase materials have been shown to have significant modifications of their mechanical properties compared with the coarse-grain equivalent materials. The huge surface area of nanoporous materials has attracted much attention for applications in chemistry such as molecular sieves, catalysis, and gas sensing. This has motivated intense research aimed at the fabrication of materials with a weU-controUed composition and nanoscale structure, such as synthetic zeolites. 

Krishna (2000), starting from the fundamental concepts of Maxwell J. C. and Stefan X, describes the conhguration diffusion, also called surface diffusion, within zeolite crystals by means of the following set of equations, namely the generalized MS approach (Kapteijn et al, 2000 Krishna, 2000). Nevertheless, this set of equations can also be used to describe diffusion in other nanostructured materials such as carbon nanotubes ... 

Synthesis of Porous Materials Zeolites, Clays, and Nanostructures, edited by Mario L. Occelli and Henri Kessler Methane and Its Derivatives, Sunggyu Lee... 

Sudhakar Reddy, J., Dicko, A., and Sayari, A., in Synthesis of Porous Materials Zeolites, Clays and Nanostructures (M. Occelli and H. Kessler, Eds.), p. 405-415. Marcel Dekker, New York, 1997. 

In the following decades, researchers in catalysis turned their efforts to controlhng molecular structure as well as size. The catalyst zeolite paved the way. In the late 1960s, researchers at Mobil Oil Co. were able to s)uithesize zeolite by deliberately designing and preparing the structure of catalysts at the atomic and molecular levels. The resulting nanostructured crystalline material (ZSM-5)—with a 10-atom ring and pore size of 0.45-0.6 nm—enabled the control of selectivity in petrochemical processes at the... 

The low-temperature physisorption (type I isotherm) of hydrogen in zeolites is in good agreement with the adsorption model mentioned above for nanostructured carbon. The desorption isotherm followed the same path as the adsorption, which indicates that no pore condensation occurred. The hydrogen adsorption in zeolites depends linearly on the specific surface areas of the materials and is in very good agreement with the results on carbon nanostructures [24]. 

Synthesis of Porous Materials Zeolites, Clays, and Nanostructures,... 

For the detailed study of reaction-transport interactions in the porous catalytic layer, the spatially 3D model computer-reconstructed washcoat section can be employed (Koci et al., 2006, 2007a). The structure of porous catalyst support is controlled in the course of washcoat preparation on two levels (i) the level of macropores, influenced by mixing of wet supporting material particles with different sizes followed by specific thermal treatment and (ii) the level of meso-/ micropores, determined by the internal nanostructure of the used materials (e.g. alumina, zeolites) and sizes of noble metal crystallites. Information about the porous structure (pore size distribution, typical sizes of particles, etc.) on the micro- and nanoscale levels can be obtained from scanning electron microscopy (SEM), transmission electron microscopy ( ), or other high-resolution imaging techniques in combination with mercury porosimetry and BET adsorption isotherm data. This information can be used in computer reconstruction of porous catalytic medium. In the reconstructed catalyst, transport (diffusion, permeation, heat conduction) and combined reaction-transport processes can be simulated on detailed level (Kosek et al., 2005). 

Shu, S., Husain, S. and Koros, W.J. (2007) Formation of nanostructured zeolite particle surfaces via a halide/Grignard route. Chemistry of Materials, 19 (16), 4000-4006. 

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