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M. Dvoyashkin E. E. Romanova W.-D. Einicke R. Gläser J. Kärger R. Valiullin 《Adsorption》2011,17(1):93-99
Diffusion of cyclohexane in mesoporous silica materials with different degrees of surface silanization has been probed by
means of pulsed field gradient nuclear magnetic resonance. The self-diffusion coefficients have been measured at various pore
fillings from about 10% of one monolayer coverage to complete pore saturation by the capillary-condensed phase. It is found
that the surface modification, namely grafting of dimethyloctadecylmethoxysilane molecules to the silica surface, reduces
diffusivities of guest molecules as compared to the native sample. The contribution of the Knudsen molecular diffusion to
the measured diffusivity has been assessed using the model of fast molecular exchange between the adsorbed phase on the pore
walls and the molecules in the gaseous phase in the pore interior. The diffusivity data were correlated with the degree of
the surface modification, with the latter being probed by measuring 1H and 13C spectra using magic angle spinning (MAS) solid state NMR, nitrogen adsorption and thermogravimetry. 相似文献
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Dr. Wolfgang Lutz Dirk Enke Wolf‐Dieter Einicke Dirk Täschner Rolf Kurzhals 《无机化学与普通化学杂志》2010,636(15):2532-2534
Zeolites of type NaY synthesised by use of seed‐solution and zeolite X‐seeds to initialise the crystallisation were compared. A different homogeneity of the internal framework structure related to the Si/Al ratio was expected. Thus, the formation of closed bulk mesopores should be influenced during treatment of NH4NaY modification for 7 hours at 450 °C and 600 °C, respectively, in the water steam of 1 bar. Occurrence of different mesopores was actually observed in obtained ultra‐stable USY zeolites using nitrogen adsorption. Whereas USY prepared by use of seed‐solution contains only open mesopores at the crystal surface, the X‐seed synthesised material contains open and closed mesopores at the surface and in the nuclei of samples, respectively. 相似文献
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Dr. Wolfgang Lutz Dirk Enke Wolf‐Dietrich Einicke Dirk Täschner Rolf Kurzhals 《无机化学与普通化学杂志》2012,638(14):2189-2192
Microporous zeolites Na‐Y and K‐Y were converted into the NaNH4‐Y and KNH4‐Y modifications by ion exchange being active in dealumination. Removal of framework aluminium and silicon is accompanied by formation of secondary mesopores. Internal mesopores are formed in the centre of zeolite crystals and external pores at their surface. Formation of mesopores changes the sorption behaviour.Residual alkali metal cations as Na+ or K+ stabilise, however, the framework ≡Si‐O‐Al≡ bonds. Because of inhomogeneous distribution of sodium ions, in NaNH4‐Y less internal but more external mesopores are formed. Potassium ions of KNH4‐Y are more homogeneous distributed over the framework why a more balanced formation of secondary pores takes place. 相似文献
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Hunger B. Matysik S. Heuchel M. Einicke W.-D. 《Journal of Thermal Analysis and Calorimetry》2001,64(3):1183-1190
Using temperature-programmed desorption (TPD), we have investigated the desorption behavior after subsequent co-adsorption
of methanol and water and after adsorption of their mixtures on a NaZSM-5 zeolite. The course of desorption indicates that
a strong mutual displacement of both components occurs. However, on the strongest adsorption sites methanol is preferentially
adsorbed, and already the addition of small amounts of methanol leads to a displacement of water. Our results support the
idea of a subdivision of the pore space for adsorption of water/methanol mixtures. Above all, the experiments show that in
the part of the pore space where both components are adsorbed, different sites are of importance which vary significantly
in their interaction strength.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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M. Jaroniec A. W. Marczewski W. D. Einicke H. Herden R. Schöllner 《Monatshefte für Chemie / Chemical Monthly》1983,114(8-9):857-873
The influence of heterogeneity parameters on the shape of excess adsorption isotherms has been discussed. These isotherms have been calculated according to the equations corresponding to different energy distributions. Next, the isotherm equations have been applied to examine the experimental excess isotherms for 1-tetradecene/dodecane mixture adsorption on different types ofX-zeolites at 293 K, 313 K and 333 K. The zeolite samples have been prepared from NaX-zeolite by exchanging the sodium ions for ions of alkalines and calcium group. Analysis of the above adsorption data by means of different isotherm equations showed that the parameters of aDubinin-Radushkevich-type equation change correctly with temperature and the contents of alkalines in the zeolite samples. 相似文献
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Sattler Rita Rosmarie Einicke W.-D. Hunger B. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):921-931
Temperature-programmed desorption (TPD) of water was applied to characterize short-time dealuminated HZSM-5 zeolites. Using
a regularization method, distribution functions of the effective desorption energy of water were calculated. The results clearly
show that during dealumination a new adsorption site is formed which can be attributed to non-framework or transient aluminium
species. The highest concentration of these sites was observed for a dealumination time of 25-30 min. NO adsorption studies
support this result. Furthermore, it could be concluded that the heterogeneity and the average acid strength of the remaining
Si-OH-Al groups of the dealuminated samples do not change compared to the Si-OH-Al groups of the parent HZSM-5 zeolite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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M. Jaroniec A. Dabrowski G. Nowakowski H. Herden W. D. Einicke R. Schöllner 《Journal of inclusion phenomena and macrocyclic chemistry》1985,3(1):85-93
The isotherm equation for adsorption of binary liquid mixtures of nonelectrolytes, involving differences in molecular sizes of components and quasi-Gaussian energy distribution of adsorption sites, is used to describe the excess adsorption data for 1-olefin/n-paraffin liquid mixtures on NaX and NaY zeolites at 293 K. This equation gives a good representation of the above adsorption data. Analysis of these data showed that the heterogeneity parameter is slightly dependent on the difference in molecular sizes of both components. 相似文献
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