Silver-zeolite

Beer, R., G. Calzaferri, J. Li, and B. Waldeck (1991), "Towards Artificial Photosynthesis Experiments with Silver Zeolites", Part 2, Coord. Chem. Rev., in press. 

Silver Zeolite Iodide Adsorption Studies. The U.S. Atomic Energy Commission, Idaho Operations Office, Under Contract AT(10-1)-1230, Nov. 

Members of the retinoid natural product class, containing a quaternary benzylic stereocenter, were prepared by the ring closure of allyl-arylethers. The palladium catalysed process in the presence of sodium formate led to the formation of a partially reduced benzofurane derivative through an insertion-hydride capture reaction sequence (3.24.), The coupling, which was run in the presence of a silver-zeolite, showed acceptable enantioselectivity when... 

Silver zeolites, 296 Zinc-Silver-Graphite, 348 Thallium Compounds... 

Iodophenol on alumina Hypoiodous acid Charcoal or silver zeolite Organic. 

The second example is the analysis of silver zeolite [7], in which it was shown that there is a substantial silver atom flux accompanying the relatively weak silver cation flux. There were no molecules or clusters containing silver in the gas phase. Pure silver metal heated to the sublimation point gives primarily neutral atoms and metallic clusters with no ions. Thus, sublimation of atomic silver ions from zeolite may be a pseudo-S-L type of process, although additional evidence concerning the species of silver in the solid state would be required prior to making this assertion. 

Additional evidence, useful in supporting the concept that silver zeolite and silver molten glass ion emitters are S-L processes, would be that both ions and neutrals arise from the same species in the solid state this issue is addressed in the following section, on high-temperature SIMS. 

Jacobs et al. (261) have shown that photolysis of water can be achieved using AgY zeolite. Irradiation using sunlight on water vapor-saturated AgY yields oxygen, and thermal treatment (600 C) of the reduced silver zeolite restores the Ag+ cations with the evolution of hydrogen, i.e.,... 

Thallium and Silver Zeolite-A The zeolite-A structure is constructed from simple aluminosilicate cubeoctahedra, connected to form a three-dimensional, cubic network by so-called double-4 rings (Figure 1). This arrangement leads to the formation of large a-cages whose internal diameter is approximately 11 A. 

A corresponding Fm3c refinement of the silver zeolite-A structure, using a sample with a Si/Al ratio of 1.02, has also been achieved. The final profile R-factor is 12.3 percent and a bimodal distribution of Si-0 and Al-0 bond lengths is again obtained, confirming once more the alternation of Si and Al. Our analysis of the cation positions is not yet complete and we are examining the results for evidence of silver clusters, as reported by Uytterhoeven and co-workers (17). 

In the past five years, the field of metal-zeolite chemistry has developed to the point where a number of metal atomic and small cluster guests have been synthesized and unequivocally characterized by spectroscopic and crystallographic techniques. The silver-zeolite A, X and Y systems in particular have yielded a wealth of valuable structural and site information pertaining to silver guests in the size range of one to six atoms (3). The spectroscopy of these silver-zeolites can therefore be probed in detail and compared with the corresponding data for silver atoms and silver clusters immobilized in weakly interacting rare gas solid supports (4). 

Hydrocarbon sorbate vibrations. IINS spectra have been recorded for a number of simple sorbate molecules within aluminosilicate zeolites, including hydrogen in A (40, 41). acetylene in X (4, ethylene in A (42) and X (44-46). and p-xylene (42) in X type materials. In addition to intramolecular modes, where interaction between the sorbate and the non-framework cations is strong (for example in the ethylene - silver zeolite A system (42)), vibrational transitions associated with sorbate motion with respect to the zeolite s internal surface can be observed. The latter modes, and the dependence of their frequencies on loading, structure and composition are of particular interest as they convey detailed information about the character of the zeolite - sorbate... 

Research into controlled-release antimicrobials continues with organo-silver compounds and silver zeolites, which are promising candidates for textile finishes. Silver ions, for example, incorporated in glass ceramic, have a very low toxicity profile and excellent heat stability. These principles are also used for fibre modification, an alternative to the antimicrobial finishes with high permanence. In recent years a variety of antimicrobial modified fibres have been developed, including polyester, nylon, polypropylene and acrylic types. An example of these fibre modifications is the incorporation of 0.5-2 % of organic nitro compounds... 

Chen, N. Yang, R. T. Ab Initio Molecular Orbital Study of Adsorption of Oxygen, Nitrogen, and Ethylene on Silver-Zeolite and Silver Halides. Ind. Eng. Chem. Res. 1996,35, 4020. 

The argon selectivity showed 1 the silver zeolite A can be explained in terms of the difference in polarizability values. Argon having polarizability higher than that of oxygen shows relatively high adsorption capacity and selectivity. 

Garegg, P J, Ossowski, P, Silver zeolite as promoter in glycoside synthesis. The synthesis of 3-d-mannopyranosides, Acta Chem. Scand. B, 37, 249-250, 1983. 

More widely used promoters for this purpose are silver zeolite and silver silicate, which were developed by Paulsen [18] and Garegg [19], respectively. Although not being commercially available, these reagents can be conveniently prepared from silver nitrate and proved to be quite powerful. More recently, van Boeckel developed the use of silver silica-alumina, which was reported to be more reactive than other insoluble salts and to have an enhanced cation capacity [20]. Representative examples of successful y0-mannosylation by using insoluble salts are depicted inO Scheme 8 [19,21,22]. 

Thallium zeolites, 4A and 13X. The catalyst is prepared from a mixture of TI2CO3 and the crushed molecular sieves in water at 45°, and then washed with acetone and dried at 190°. Co or Cd zeolites are prepared similarly with C0CO3 or CdC03. O-Glycosylation. Traditional glycosylation catalysts are silver or mercury salts. Recently silver zeolite has been recommended as the catalyst for preparation of 1,2-cis-glycosides. The thallium zeolite is useful when the glycosyl bromide is unstable in the presence of silver catalysts. ... 

More recent applications of synthetic zeolites are e.g. in the sector of microbiocidal agents (silver zeolites), as... 

In synthetic polymers, as well as edible films, various classes of antimicrobial compounds have been evaluated. These include organic acids, enzymes, bacteriocins, and other compounds which may consist of tri-closans, silver zeolites, and fungicides. Several approaches are followed when incorporating an antimicrobial substance into packaging material (Quintavalla and Vicini, 2002) ... 

Various studies have looked at biocide products like Triclosan and silver zeolites (114) but with limited success. Additionally these aetives have some issues related to regulatory approval. This may be beeause release of biocide from the plastie is limited and although inherently valuable to reduee eontamination of the food itself, more is needed in some instanees. Intimate eontact between the plastic film or a carton with the food would also be required. 

Membrane filter test results of PVC samples containing among others Silver Zeolite (4 phr) at extrusion times of... 

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