High silica zeolite

Figure C2.12.2. Fonnation of Br0nsted acid sites in zeolites. Aqueous exchange of cation M witli an ammonium salt yields tlie ammonium fonn of tlie zeolite. Upon tliennal decomposition ammonia is released and tire proton remains as charge-balancing species. Direct ion-exchange of M witli acidic solutions is feasible for high-silica zeolites.

Freyhardt C C, Tsapatsis M, Lobe R F, Balkus Jr K J and Davis M E 1996 A high-silica zeolite with a 14-tetrahedral-atom pore opening Nature 381 295-8... 

Wagner P, Yoshikawa M, Lovallo M, Tsu]i K, Tsapatsis and Davis M E 1997 CIT-5 a high-silica zeolite with 14-ring pores Chem. Commun. 2179-80... 

A comprehensive summary of the preparation of high-silica zeolites. 

Volume 33 Synthesisof High-silica Aluminosilicate Zeolites edited by P.A. Jacobs and J.A. Martens... 

J. A. Martens, Synthesis of High-Silica Aluminosilicate Zeolites, Elsevier, Amsterdam, 1987, 390 pp. M. L. Occelli and H. E. Robson (eds.). Zeolite Synthesis, ACS Symposium Series No. 398, 1989, 664 pp. J. Klinowski and P. J. Barrie (eds.) Recent Advances in Zeolite Science, Elsevier, Amsterdam, 1990, 310 pp. G. V. Tsitsishvili, T. G. Andronikashvili, G. M. Kirov and L. D. Filizova, Natural Zeolites, Ellis Horwood, Chichester, 1990, 274 pp. 

A fourth option is to apply high silica zeolites (de-aluminated mordenite, US-Y or beta) to cope with the HBr formed. 

Le Eebre, R.A. (1989) High-silica zeolites and their use as catalysts in organic chemistry , Ph.D. Thesis, Delft University of Technology. 

Sticking with nylon production, high-silica pentasil zeolites are used by Sumitomo to overcome environmental issues associated with the conversion of cyclohexanone oxime to caprolactam (Chapter 1, Scheme 1.4). 

Regeneration of high silica zeolite used for Beckmann rearrangement... 

Many inorganic oxides can be manufactured to provide granular, porous materials with high surface areas, which can readily adsorb organic liquids. Preliminary screening of a range of oxides, namely aluminium oxides, titanium dioxides, zinc oxide, hydrotalcites, zeolites and silicas, indicated that the latter two materials were able to retain the largest quantities of biocide. 

Wichterlova, B., Sobalik, Z. and Dedecek, J. (1997) Cu ion siting in high silica zeolites. Spectroscopy and redox properties, Catal. Today, 38, 199. 

Water adsorption on high silica zeolites. Formation of hydroxonium ions and hydrogen-bonded adducts... 

The effect from the top is behind the differences in IR spectra of CO adsorbed on various Na-zeolites (Fig. 1). The IR spectrum of CO adsorbed on the high-silica Na-FER shows only one band (centred at 2175 cm 1) that is due to the carbonyl complexes formed on isolated Na+ sites. When the content of Na+ in the sample increases (Na-FER with Si/Al=8), in addition to the band at 2175 cm 1 a new band at 2158 cm"1 appears due to the formation of linearly bridged carbonyl complexes on dual cation sites. The IR spectrum of CO adsorbed on Na-A,which has a large concentration of Na+ cations, shows bands centred at 2163, 2145, and 2129 cm 1 the band at 2163 cm"1 is due to the carbonyl species formed on dual cation sites, while bands at 2145 and 2129 cm"1 are due to carbonyls formed on multiple cation sites (Table 1), i.e., on adsorption sites involving more than two cations. 

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