Neutron powder diffraction study of a Na,Cs-Rho zeolite

Abstract

Zeoüte Rho / Aluminosilicate framework distortion / Variation of pore size / Neutron powder diffraction / (Si, Al)-0 bond lengthsAbstract. The crystal structure of a Na, Cs-Rho zeolite was studied at 373 Κ (Na8.4Cs3.2Si36.4Aln.6O96 · 5D 2 0) by neutron powder diffraction and Rietveld profile analysis. It crystallizes in the noncentrosymmetric space group /43m and has a unit cell constant a = 14.6566(4) Â. The final residuals are R¡ = 9.65% and R wp = 8.01%. The distortion of the (Al,Si)0 2 -framework of this zeolite fits into the pattern established for other noncentrosymmetric Rho zeolites. Particularly, the ellipticity of the eight-ring and the pore size are strictly a function of the cell constant of the zeolite. The mean distance (Al,Si)-0 is observed to be 1.636 Â, in excellent agreement with the mean (Al,Si)-0 distance of 1.638 Â calculated for the Si and Al content of our sample.

Flexible Template-Free RHO Nanosized Zeolite for Selective CO2 Adsorption

“…This value is slightly larger than the one reported by Baur Δ = 1.57 Å. 26 According to Corbin et al 19 , the degree of distortion is related to the charge density of the cations located within the D8R windows. In this work, for NaCs-RHO(H2O) the occupancy factor of the Cs + cations sitting in the center of the D8R window site is larger than the one reported by Baur in agreement with a lower Si/Al ratio.…”

“…In this work, for NaCs-RHO(H2O) the occupancy factor of the Cs + cations sitting in the center of the D8R window site is larger than the one reported by Baur in agreement with a lower Si/Al ratio. 26 These extra-framework charge-compensating cations influence the distortion of the D8Rs, which is similar to the effect of temperature, ion-exchange or adsorption of different molecules in RHO-type zeolites. On the other hand, it has been shown that the high water content of the NaCs-RHO(H2O) sample is due to the higher Si/Al ratio which can also influence the RHO framework, i.e.…”

A Study of Heat-Treatment Induced Framework Contraction in Strontium-ETS-4 by Powder Neutron Diffraction and Vibrational Spectroscopy

“…The third effect is known in previously studied cases of framework deformation in dehydrated zeolitic frameworks. [18][19][20][21] We describe here an investigation of structural changes in dehydrated Sr-ETS-4. Powder neutron diffraction data from heat-treated Sr-ETS-4 samples have been analyzed by the Rietveld method to determine the structures of Sr-ETS-4 heattreated at different temperatures.…”

Flexibility and Cation Distribution upon Lithium Exchange of Aluminosilicate and Aluminogermanate Materials with the RHO Topology

“…In contrast, zeolite RHO (Figure 1) undergoes framework distortions upon alteration in the type of extraframework cation and degree of hydration. 5,6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] This unusual flexibility has been extensively investigated for aluminosilicate compositions. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] We recently reported the synthesis and characterization of an aluminogermanate with the zeolite RHO topology 27,28 that possesses a framework Ge/ Al ratio of unity.…”

“…5,6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] This unusual flexibility has been extensively investigated for aluminosilicate compositions. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] We recently reported the synthesis and characterization of an aluminogermanate with the zeolite RHO topology 27,28 that possesses a framework Ge/ Al ratio of unity. This contrasts with aluminosilicate rho which tends to have Si/Al ∼ 3, 8,29,30 but is more similar to the gallosilicate which has Si/Ga ∼ 1.3.…”