Single-Crystal Structure of Fully Dehydrated Sodium Zeolite Y (FAU)

ANALYTICAL SCIENCES 2006, VOL. 22 x209 2006 © The Japan Society for Analytical Chemistry X-ray Structure Analysis Online Single-crystal Structure of Fully Dehydrated Sodium Zeolite Y (FAU), Na71[Si121Al71O384]-FAU Sung Man SEO,*1 Ghyung Hwa KIM,*2 Heung Soo LEE,*2 Seong-Oon KO,*1 Oh Seuk LEE,*1 Young Hun KIM,*3 Seok Han KIM,*4 Nam Ho HEO,*4 and Woo Taik LIM*1† *1 Department of Applied Chemistry, Andong National University, Andong 760–749, Korea *2 Pohang Accelerator Laboratory, Pohang University of Science and Technology, PO Box 125, Pohang 790–600, Korea *3 Department of Environmental Engineering, Andong National University, Andong 760–749, Korea *4 Department of Applied Chemistry, Kyungpook National University, Daegu 702–701, Korea –6 The crystal structure of Na71[Si121Al71O384]-FAU, a = 24.946(3)Å, dehydrated at 673 K and 1 × 10 Torr, was determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3m at 294 K. About 71 Na+ ions per unit cell are found at an unusually large number of crystallographically distinct positions, seven. Five Na+ ions are at the centers of double 6-rings (D6Rs, site I). Two site-I′ positions (in the sodalite cavities opposite D6Rs) are occupied by eight and fourteen Na+ ions, respectively, per unit cell. Thirteen and fifteen Na+ ions per unit cell are found at two site-II positions, in the supercages opposite S6Rs. The remaining twelve and four Na+ ions occupy two sites III′ near triple 4- rings in the supercage. (Received April 3, 2006; Accepted June 19, 2006; Published on web August 25, 2006) This work was made to investigate the sites of Na+ in zeolite Y collected at 294(1)K on an ADSC Quantum210 detector at (synthetic faujasite (FAU) with Si/Al = 1.69) by single-crystal Beamline 4A MXW of Pohang Light Source. A summary of X-ray diffraction. Large colorless single crystals of zeolite Y, the experimental and crystallographic data is presented in stoichiometry NaxM71–x[Si121Al71O384]-FAU, where M = Tables 1 and 2. A full-matrix least-squares refinement + H3O , with diameters up to 200 µm, were synthesized from gels with the composition Table 1 Crystal and experimental data 3.58SiO :2.08NaAlO :7.59NaOH:455H O:5.06TEA:1.23TCl.1 2 2 2 CSD No. 416357 A starting gel was prepared from fumed silica (99.8%, Sigma), Formula Na71Si121Al71O384 sodium aluminate (technical, Wako), sodium hydroxide (96%, Formula weight 13090.1 Wako), triethanolamine (99+%, Acros), bis(2-hydroxy- Crystal cross section (mm) 0.20 ethyl)dimethylammonium chloride (99%, Acros), and distilled Crystal color pale yellow water. Ten transparent single crystals from the batch were Data collection T(K) 294(1) intentionally broken in order to use the fresh surface of the Crystal system cubic crystals, and were attached on to the surface of carbon-attach Space group, Z Fd3m, 1 tape for SEM-EDS analysis (JSM6300). Each single crystal was X-ray source PLS (4A MXW BL) measured 3 times, which resulted a Si/Al = 1.69 mean value. Wavelength (Å) 0.750 We prepared 0.1 g of hydrated Na [Si Al O ]-FAU Unit cell constant, a (Å) 24.946(3) 71 121 71 384 V (Å3) 15524.0(3) single crystals by a static ion-exchanging method of products 3 Dx(g/cm ) 1.41 with aqueous 0.1 M NaCl (Aldrich, 99.99%) (pH adjusted from 2θ range in data collection (deg) 4.8 < 2θ < 56.0 6 to 11 by a dropwise addition of NaOH (Aldrich, 99.998%)) to No. of unique reflections, m 809 + + generate a crystal without H3O ions, only Na ions to balance No. of reflections with 748 the charge of the zeolite framework. The ion-exchange Fo > 4σ (Fo) procedure was repeated 5 times with fresh solutions. The No. of variables, s 63 product was then washed each time with 300 mL of distilled Data/parameter ratio, m/s 12.8 water followed by filtration, and oven-dried at 323 K for 1 day. Weighting parameters, a/b 0.077/253.7 One of these, a clear and colorless octahedron of about 200 µm Final error indices σ in cross-section, hydrated Na+-exchanged zeolite Y crystal was R1/R2 (Fo > 4 (Fo)) 0.047/0.154 R1/R2 (all intensities) 0.049/0.155 lodged in a fine Pyrex capillary and dehydrated at 673 K and 1 –6 Goodness-of-fit 1.12 × 10 Torr for 2 days. Still under vacuum in its capillary, the –3 (∆ρ)max 0.537 eÅ crystal was then allowed to cool, and was sealed in its capillary –3 (∆ρ)min –0.582 eÅ and removed from the vacuum line by a torch. A microscopic Measurements ADSC Quatum210(Beamline examination showed that the crystal had a pale-yellow color. 4A of PLS) X-ray diffraction data of the resulting single-crystal was Program system ADSC-ADX Structure determination direct methods (SHELXS-97) † To whom corresponding should be addressed. Refinement full matrix least-squares E-mail: [email protected] (SHELX-97) x210 ANALYTICAL SCIENCES 2006, VOL. 22 Table 2 Final atomic coordinates and equivalent isotropic thermal parameters Fig. 1 Stylized drawing of the framework structure of zeolite Y. Near of the center of each line segment is an oxygen atom. The different oxygen atoms are indicated by numbers 1 to 4. Extraframework cation positions are labeled with Roman numerals. 2 2 (SHELXL97) was made on Fo using all data. The atomic scattering factors for Na+, O–, and (Si,Al)1.82+ were used. The function describing (Si,Al)1.82+ is the weighted mean of the Si4+, Si0, Al3+, and Al0 functions (Si/Al = 1.69). All scattering factors were modified to account for anomalous dispersion. The framework structure of faujasite was characterized by a double 6-ring (D6R, hexagonal prism), a sodalite cavity (a cubooctahedron), and a supercage (Fig. 1). Each unit cell had 8 supercages, 8 sodalite cavities, 16 D6Rs (double 6-rings), 16 12-rings, and 32 S6Rs (single 6-rings).3 The exchangeable cations, which balance the negative charge of the faujasite framework, usually occupy some or all of the sites indicated by Fig. 2 Stereoviews of a representantive double 6-rings (D6Rs) (a), Roman numerals in Fig. 1. sodalite (b), and supercage unit (c) in dehydrated Na71 The X-ray diffraction intensities clearly show mirror [Si121Al71O384]-FAU. The zeolite Y framework is drawn with heavy symmetry at (110), indicating that the Si and Al positions are bonds. The coordination of Na+ ions to oxygens of the zeolite not distinguishable. Accordingly, the crystal in this work was framework are indicated by light bonds. Ellipsoids of 25% refined using the space group Fd3m. It is well established that probability are shown. there is no long-range Si/Al order in zeolite Y. The total number of Na+ ions found per unit cell, 71.4(15), and O2– radii, 2.29 Å. The O(2)–Na(2a)–O(2) and does not differ significantly from 71, but conforms with the O(2)–Na(2b)–O(2) angles are 114.8(14)˚ and 109.13(15)˚, SEM-EDS results (Si/Al = 1.69, the number required to balance respectively (Table 3). The remaining twelve and four Na+ ions the negative charge of the zeolite framework.). These 71 Na+ at Na(3′a) and Na(3′b), respectively, occupy two site-III′ ions have been found at seven equipoints (Table 2). Five at positions near triple 4-rings in the supercage (Na(3′a)–O(1) = Na(1) lie at site I, at the center of a D6R (Fig. 2(a)). Each Na+ 2.55(4)Å and Na(3′b)–O(4) = 2.64(12)Å) (Fig. 2(c)). The ion at Na(1) coordinates to the six O(3) oxygen atoms of the distances between Na+ ions and the framework oxygens are D6R at a distance of 2.739(4)Å, which is slightly longer than longer than the sum of the conventional ionic radii of Na+ and the sum of the conventional ionic radii of Na+ and O2–, 0.97 + O2–, 0.97 + 1.32 (respectively) = 2.29 Å. The reduced 1.32 (respectively) = 2.29 Å. The 22 Na+ ions are located at two aluminum content of zeolite Y, as compared to zeolite X,3 site-I′ positions opposite D6Rs in the sodalite cavities (Fig. should lead to a smaller negative charge density for the zeolite 2(b)). These Na+ ions at Na(1′a) and Na(1′b) lie inside of the framework, and therefore at each oxygen position. This in turn sodalite cavity, 0.46 Å and 0.91 Å, respectively, from the (111) should lead to longer Na–O distances. plane of three O(3) framework oxygens of the D6R to which each is bound. The eight Na+ ions at Na(1′a) and 14 Na+ ions at Acknowledgements Na(1′b) bond to three O(3)s at 2.230(10)Å and 2.365(9)Å, respectively (Fig. 2(b)). The Na(1′a)–O(3) and Na(1′b)–O(3) This work was supported by a grant (contract number: 2005- distances are about the same as the sum of the ionic radii of Na+ 0099) from the Research Fund at Andong National University. and O2–, 2.29 Å. The 28 Na+ ions are located at two site-II positions opposite S6Rs in the supercage (Fig. 2(b)). Perhaps it References does not fill because some S6Rs are severly deficient in Al atoms. Each of these ions lies relativly inside the supercage, 1.

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