| | 2 | Author
| A. Seidel, B. Boddenberg | Requires cookie* | | | Title
| A  | | | | Abstract
| S tu d y o f th e D is tr ib u tio n o f S o d iu m C a tio n s in th e Z e o lite s N a X , N a Y a n d Z n N a Y U s in g C a r b o n M o n o x id e A d s o rp tio n a n d 23N a N M R T e c h n iq u e s Herrn Professor Dr. Werner Müller-Warmuth zum 65. Geburtstag gewidmet The zeolites NaX, NaY, Zn(55)NaY, and Zn(74)NaY were investigated by means of carbon monoxide adsorption and with static and magic angle spinning (MAS) 23Na NMR spectroscopy. The Na+ distribution between the sodalite (/?)-and supercages of the fully hydrated zeolites NaX and NaY were found to agree with XRD results. In the hydrated zinc-exchanged zeolites the Na + ions almost exclusively populate the /?-cages. The adsorption isotherms of CO in the dehydrated zeolites were analyzed quantitatively to yield the concentrations of Na+ residing in the supercages. The measured static and MAS 23Na NMR spectra were analyzed by comparing their widths and shapes with simulated central transition patterns and yield, inter alia, the concentrations of Na+ associated with the spectrum components. Arguments are put forward that 23Na NMR of dehydrated zeolites is well suited to distinguish Na + cations in highly symmetric environments and mobile Na+ species from others located on general positions, but further resolution is hardly feasible. | | | |
Reference
| Z. Naturforsch. 50a, 199—210 (1995); received October 17 1994 | | | |
Published
| 1995 | | | |
Keywords
| 23Na NMR, Adsorption, Carbon monoxide, Zeolites, Zinc-exchange | | | |
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| default:Reihe_A/50/ZNA-1995-50a-0199.pdf | | | | Identifier
| ZNA-1995-50a-0199 | | | | Volume
| 50 | |
| 3 | Author
| F. Ucun, A. Sağlam, F. Köksal, S. Bahçeli | Requires cookie* | | | Title
| An EPR Study of Mo 5+ Introduced into NaY Zeolites by Solid-State Reactions | | | | Abstract
| By means of an EPR investigation of Mo 5+ ions introduced into NaY zeolites by solid-state reactions, the location and coordination of Mo 5+ in zeolites were investigated. Two different locations, free and distorted tetrahedral, were found. The molecular orbital coefficient, ß 2 , and the effective charge, Q, for the MO 5+ ions in a distorted tetrahedral structure were calculated and interpreted. | | | |
Reference
| Z. Naturforsch. 54a, 159—161 (1999); received December 2 1998 | | | |
Published
| 1999 | | | |
Keywords
| EPR, Zeolite, Mo 5+, NaY | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0159.pdf | | | | Identifier
| ZNA-1999-54a-0159 | | | | Volume
| 54 | |
| 4 | Author
| F. Ucun, F. Köksal | Requires cookie* | | | Title
| An EPR Study on V0 2+ and Mn 2+ Ions in Some Zeolites | | | | Abstract
| The electron paramagnetic resonance (EPR) of hydrated V0S0 4 -3H 2 0 and MnCl 2 -2H 2 0, adsorbed on the synthetic zeolites 3A, 4A, 5A and 13X of pore diameters 0.3, 0.4, 0.5, and 1.0 nm, respectively, and the natural zeolites heulandite and clinoptilolite was investigated. The spectra indicated that the coordination structures are V0(H 2 0)5 + and Mn(H 2 0)g + , and that their EPR line widths vary with the pore diameters and the surface areas of the zeolites. The spectra of V0(H 2 0)5 + in natural zeolites at room temperature display an isotropic behavior and therefore indicate that the water ligands are mobile. The EPR spin Hamiltonian parameters, the molecule orbital constant ß* 2 , and the Fermi contact term K e[[ were determined and are discussed. The spectra of Mn(H 2 0)^ for narrow-pore zeolites indicate the existence of mobile and immobile water, whereas for wide-pore and natural zeolites they indicated the existence of only mobile water. The obtained Mn(H 2 Ö)g + spectra are discussed. | | | |
Reference
| Z. Naturforsch. 51a, 23—26 (1996); received October 17 1995 | | | |
Published
| 1996 | | | |
Keywords
| EPR, V0 2 +, Mn 2 +, Zeolites, Coordination | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0023.pdf | | | | Identifier
| ZNA-1996-51a-0023 | | | | Volume
| 51 | |
| 5 | Author
| Fevzi Köksal, Fatih Ucun, İbrahim Kartal | Requires cookie* | | | Title
| EPR Study of Cr 5 + and Cu 2 + in Some Zeolites Introduced by Solid-and Liquid-State Reactions | | | | Abstract
| This study reports on the EPR of Cr 5+ and Cu 2+ ions, introduced by solid-and liquid-state reactions with the synthetic zeolites 3A, 4A and 5A, and the natural zeolite clinoptilolite. Cr 3+ was oxidized to Cr 5 + in the samples, the coordination around Cr 5 + being square pyramidal. Super-hyperfine (shf) interaction of Cr with 27 A1 nucleus was observed in both solid-and liquid-state-introduced 5A zeolite, whereas this shf could not be observed for the solid-state introduced 4A zeolite. The liquid-state Cr-introduced 4A zeolite needed a heat treatment at 473 K for Vi h for the appearance of shfs. Furthermore, it has been found that the coordination structure around the Cu 2 + is square pyramidal in solid-state introduced samples, whereas it is octahedral in the liquid-state introduced ones. | | | |
Reference
| Z. Naturforsch. 51a, 242—244 (1996); received January 8 1996 | | | |
Published
| 1996 | | | |
Keywords
| EPR, Cu 2 +, Cr 5 +, Zeolites, Ion introduction | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0242.pdf | | | | Identifier
| ZNA-1996-51a-0242 | | | | Volume
| 51 | |
| 6 | Author
| F. Köksal, F. Ucun | Requires cookie* | | | Title
| EPR of 0 2 " Radicals in the Zeolites NH 4 NaY and NH 4 CaA | | | | Abstract
| Activated and non-activated states of the zeolites NH 4 NaY and NH 4 CaA, and their NH 4 forms were prepared with an (NH 4) 2 S0 4 solution and were investigated by EPR after 7-irradiation. The formed radicals were attributed to O-T supposed to be trapped near a trigonally coordinated framework of 27 A1 (I = 5/2). Anisotropic O^" spectra were observed, consisting of hyperfine structure due to the 27 Al framework, even at room temperature. This was attributed to the scarceness of NH 4 sites or trap sites because of the preparation of the NH 4 forms of the zeolites with an (NH 4) 2 S0 4 solution. The crystal field splittings were found and interpreted. | | | |
Reference
| Z. Naturforsch. 53a, 951—954 (1998); received October 28 1998 | | | |
Published
| 1998 | | | |
Keywords
| EPR, Zeolites, 0~, NH 4 NaY, NH 4 CaA | | | |
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| default:Reihe_A/53/ZNA-1998-53a-0951.pdf | | | | Identifier
| ZNA-1998-53a-0951 | | | | Volume
| 53 | |
| 7 | Author
| Masahiko Matsumiya, Ryuzo Takagi3 | Requires cookie* | | | Title
| Molecular Dynamics Study on the Adsorption Selectivity for Negative Elements in Aluminosilicates | | | | Abstract
| For the pyrochemical reprocessing o f spent metallic nuclear fuels in molten salt baths it is important to investigate the adsorption selectivity o f cations in aluminosilicates. A molecular dynamics simulation has been performed on sodalite and zeolite with exchangeable monovalent and multivalent cationic fission products at 673 K in order to calculate their self-diffusion coefficients in the aluminosilicate framework and estimate the selectivity o f the exchangeable cations. The results enables us to conclude that the self-diffusion coefficients of monovalent cations decrease with increasing ionic radius. The order of the adsorption selectivity is Li < K < Na < Cs in sodalite and Li < Na < K < Cs in zeolite. The self-diffusion coefficients of multivalent cations are almost independent o f the ionic radius, and these cations are in aluminosilicates more stable than monovalent cations. The results are consistent with the experimental results. | | | |
Reference
| Z. Naturforsch. 56a, 459—165 (2001); received February 9 2001 | | | |
Published
| 2001 | | | |
Keywords
| Adsorption Selectivity, Aluminosilicates Framework, Molecular Dynamics Simulation, Negative Elements, Self-diffusion Coefficient, Sodalite, Zeolite | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0459.pdf | | | | Identifier
| ZNA-2001-56a-0459 | | | | Volume
| 56 | |
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