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Synthesis of large single crystals of templated Y faujasite
Journal of Crystal Growth 222 (2001) 801–805
Synthesis of large single crystals of templated Y faujasite Samia Ferchichea, Maria Valcheva-Traykovaa, David E.W. Vaughanb, Juliusz Warzywodaa, Albert Sacco Jra,* a
Center for Advanced Microgravity Materials Processing, Department of Chemical Engineering, 147 Snell Engineering Center, Northeastern University, Boston, MA 02115-5000, USA b Materials Research Laboratory, Pennsylvania State University, University Park, PA 16802, USA Received 3 August 2000; accepted 1 November 2000 Communicated by R.W. Rousseau
Abstract Large single crystals of zeolite Y with diameters up to 210–245 mm and Si/Al=1.71 have been synthesized from a reaction mixture (4.76Na2O : 1.0Al2O3 : 3.5SiO2 : 454H2O : 0.6T2O : 5TEA) comprising fumed silica (Cab-O-Sil M5), sodium aluminate, and the template bis(2-hydroxyethyl)dimethylammonium chloride (TCl) in an aqueous triethanolamine (TEA) cosolvent. # 2001 Elsevier Science B.V. All rights reserved. PACS: 81.05.Rm; 81.10.ÿh; 81.10.Dn Keywords: Crystal growth; Large zeolite crystals; Hydrothermal synthesis; Zeolite Y
1. Introduction Faujasites (FAU) of different Si/Al ratios are widely used as catalysts and sorbents, the former mainly utilizing the higher ratios (Y-type) and the latter the lower ratio X-types. Single crystals of synthetic aluminosilicate zeolites with the FAU structure, large enough for conventional singlecrystal X-ray analysis have been grown only with framework Si/Al51.5, characteristic of the FAU-X type [1–5]. This is the first report of the growth of such large crystals of the FAU-Y type with Si/Al>1.5; earlier work reported single FAUY crystal sizes only up to about 40 mm [6,7]. Using *Corresponding author. Tel.: +1-617-373-7910; fax: +1617-373-2209. E-mail address: [email protected] (A. Sacco Jr).
the general procedure developed for the growth of large crystals of FAU-X [5] together with the template used to make ECR-4 [8] (FAU with Si/Al>3), 210–245 mm single crystals of FAU-Y with a Si/Al=1.71 have been synthesized.
2. Experimental Syntheses were from gels of composition: 4.76 Na2O : 1.0Al2O3 : 3.5SiO2 : 454H2O : 0.6T2O : 5TEA formed by mixing aqueous silica slurries and TEA- [1] and TCl- [8] containing sodium aluminate solutions. The silica slurries were prepared in 30-ml polyethylene (HDPE) bottles by suspending 0.58 g of Cab-O-Sil M-5 fumed silica (Cabot) in 10 g of deionized water (resistivity>
0022-0248/01/$ - see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 0 0 ) 0 0 9 7 9 - 9
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S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
Table 1 The results of synthesis of large FAU-Y crystals Double filtration of TEA/TCl-sodium aluminate stock solution
No No No Yes Yes Yes Yes
Time of mixing of gel (h)a
5 24 24 24 24 5 5
Synthesis time (d)
14 14 15 16 18 18 18
Particulate product
Diameter of largest FAU (mm)b
Diameter of largest GIS (mm)b
Amount of GIS in the product (number %)c
140–175 140–175 210–245 210–245 210–245 210–245 210–245
100–125 100–125 125–160 125–160 125–160 125–160 125–160
50–60 50–60 20–30 20–30 20–30 20–30 20–30
a
Elapsed from preparing TEA/TCl-sodium aluminate stock solution. SEM analysis. c Optical microscope analysis. b
18 MO cm). The sodium aluminate ‘‘stock’’ solutions were prepared in 250-ml HDPE bottles by dissolving 6.47 g of sodium aluminate powder (NaAlO2 0.14H2O, technical, EM Science) in hot solutions of 11.51 g of sodium hydroxide (pellets, 97+%, Acros Organics) dissolved in 170 g of deionized water. Immediately after cooling, the aluminate solutions were filtered through 0.2-mm membrane filters (Supor-200, Gelman). This is necessary because unreacted nano-crystals of alumina in the sodium aluminate are known to act as seeds in zeolite syntheses. TEA (99+%, Acros Organics) and TCl (99%, Acros Organics) were added to the filtered sodium aluminate solutions in the amount of 15.19 and 4.19 g/100 g of the filtered aluminate solution, respectively. TEA/TCl-sodium aluminate solutions were filtered again through 0.2-mm membrane filters. Products grown from stock solutions, which were not filtered after addition of TEA and TCl usually resulted in larger amounts of polycrystalline impurity phases and smaller FAU crystals (see Table 1). TEA/TCl-sodium aluminate stock solutions were typically held at room temperature (208C) for several hours before combining 16.03 g of the stock solution with the silica slurries in 30-ml HDPE bottles. The bottles were then sealed, hand-shaken for 15–20 s then heated
statically in a convection oven at 958C for 2–3 weeks. The products were filtered, washed with deionized water, and dried for 24 h at 808C before analysis. Scanning electron microscope (SEM) images of the uncoated crystals were obtained on a Hitachi S-4700 cold field emission SEM using the upper secondary electron detector, 1–3 kV accelerating voltage, and 10 mA emission current. The X-ray powder diffraction (XRD) data were obtained on a Bruker D5005 y :2y Bragg–Brentano diffractometer equipped with a curved graphite crystal diffracted beam monochromator and NaI scintillation detector using Cu Ka radiation. The XRD data were collected with a step increment of 0.028 2y and a count time of 5 s/step. To minimize preferred orientation effects, specimens for XRD analysis were ground to a fine powder. Samples for single-crystal X-ray analysis were prepared by adhering the crystals onto the ends of glass fibers. The data were acquired on a Bruker General Area Detector Diffraction System Type 4 equipped with a one-position w stage at 54.748 using Cu Ka radiation. The crystals were examined in the transmission regime using a 0.2-mm collimator and a detector-to-sample distance of 6 cm. Fourier transform infrared (FTIR) spectra were obtained on a Nicolet Magna-IR 560 spectrometer equipped with a Spectra-Tech Collector diffuse
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
803
reflectance apparatus. The spectra (128 scans with a resolution of 2 cmÿ1) were collected at room temperature in air using 10 wt% of sample mixed with KBr. The solid-state 29Si NMR experiment was performed at 9.4 T on a homebuilt 400 MHz spectrometer at 79.46 MHz utilizing a Tecmag Libra system for pulse programming and signal digitization. The spectrum was collected at room temperature using a 5 mm Chemagnetics tripleresonance probe with rotor frequency of 5 kHz which was stabilized to 2 Hz using an active feedback spin-rate controller. A total of 2524 scans were collected using a 9 ms p/2 pulse and 60 s pulse delay as determined for a zeolite Na-A sample. 50 Hz of line broadening was applied to the spectrum. The spectrum is referenced relative to a TMS sample. Fig. 1. The SEM image of a large FAU-Y crystal.
3. Results and discussion The products contained the particulate material and variously sized ‘‘crusts’’ consisting of the aggregated octahedral crystals and/or polycrystalline spherical impurities. Examples of the specific processing conditions and the corresponding particulate products are shown in Table 1. SEM, optical microscopy, and XRD showed that the particulate products were mixtures of large transparent FAU octahedra with diameters up to 175–245 mm (Fig. 1) and of translucent polycrystalline spheres of the zeolite gismondine (GIS, Pc, Pt). The spherical impurities, with particle diameters generally larger than 100 –125 mm, were estimated (visually) not to exceed 20 –60% (by number) of the particulate product (Table 1). The maximum size of the FAU crystals and the amount of the GIS impurity depended on the method of the TEA/TCl-sodium aluminate solution preparation. Products grown from solutions which were not filtered after addition of TEA and TCl usually resulted in excessive amounts (up to 60%) of GIS spheres and smaller (up to 140– 175 mm) FAU crystals. Double filtration consistently resulted in products containing larger (up to 210–245 mm) FAU crystals contaminated by smaller (up to 30%) amounts of GIS. One higher purity sample was further purified by
Fig. 2. The
29
Si MAS NMR spectrum of FAU-Y.
removing the readily recognized GIS spheres with the aid of an optical microscope ( 300) then analyzed by solid-state 29Si NMR (Fig. 2), giving Si/Al=1.71, and confirming that the FAU crystals were type-Y. The typical stereographic projections of the large octahedral zeolite Y crystals (Fig. 3) showed that they are single crystals. The practically identical intensities of the spots (Fig. 3a) indicate a nearly uniform distribution of Si and Al in the
804
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
(Fig. 1). The micro-tension illustrated in Fig. 3 can be due to localization of bis(2-hydroxyethyl) dimethylammonium cations in large supercages parallel to the [1 1 1] direction [8]. The presence of bis(2-hydroxyethyl)dimethylammonium cations in the zeolite Y structure is illustrated in Fig. 4. As expected [10], the characteristic asymmetric (1140, 1065 cmÿ1) and symmetric (782, 710 cmÿ1) stretching T–O–T bond vibrations of FAU-Y synthesized in the presence of TCl (Fig. 4b) are shifted to the higher frequencies in comparison to its lower ratio counterpart (FAU-X, Si/Al 1.4) synthesized in the absence of TCl [5] (1124, 992 cmÿ1 and 759, 681 cmÿ1, respectively) (Fig. 4a). In the FTIR spectrum of FAU-Y collected using FAU-X grown without TCl as a background (Fig. 4c), the band at 992 cmÿ1 disappeared whereas the new bands appeared at approximately 1485 (with a shoulder at approximately 1440), 1155, and 790 cmÿ1. The band at approximately 1485 cmÿ1 is a characteristic deformation C–N bond vibration in N–CH3, while the shoulder at approximately 1440 cmÿ1 is O–H deformation in the C–OH in the amine [11]. The band at 1155 cmÿ1 is assigned to C–O
Fig. 3. Intensities (a) and shapes (b) of the spots in the stereographic projection of a large FAU-Y crystal along [1 1 1] direction.
zeolite framework, whereas their shapes (Fig. 3b) show some stress and micro-tension in the crystals along the [1 1 1] direction. The stress can be related to imperfections of the crystal habit [9]. SEM observations showed that apices of the octahedral crystals do not end in a sharp point and that crystal edges do not form totally straight lines
Fig. 4. FTIR spectra of (a) FAU-X synthesized in the absence of TCl with KBr background, (b) FAU-Y synthesized in the presence of TCl with KBr background, (c) FAU-Y using FAUX as a background, (d) mechanical mixture of TCl and FAU-X.
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
stretching vibration of HO–C–NR3 [11]. The band at 790 cmÿ1 is typical for the primary amine [11]. The comparison of the positions of the characteristic bands of TCl in a mechanical mixture with FAU-X grown without TCl (Fig. 4d) and in FAU-Y grown with TCl (Fig. 4b) suggests that the bis(2-hydroxyethyl)dimethylammonium cation is present in the zeolite Y structure.
4. Conclusions Using an easy, reproducible method, large single crystals of zeolite Y have been synthesized which are suitable for single-crystal diffraction experiments. Modifications to the approach should provide a range of Si/Al ratio crystals. The ready availability of such materials will stimulate the improved characterization of numerous catalytic and sorbent faujasites, leading to a greater understanding of their functions and to improved commercial products.
Acknowledgements The authors acknowledge the financial support of NASA, and thank Teri Lalain and Prof. Karl
805
Mueller (Department of Chemistry, Pennsylvania State University) for the 29Si NMR spectrum.
References [1] J.F. Charnell, J. Crystal Growth 8 (1971) 291. [2] For review of methods of synthesis of large zeolite X crystals see: E.N. Coker, J.C. Jansen, in: H.G. Karge, J. Weitkamp (Eds.), Molecular Sieves } Science and Technology, Vol. 1, Synthesis, Springer, Berlin, 1998, p. 121. [3] Yu.I. Smolin, Yu.F. Shelepev, I.K. Butikova, S.P. Zhdanov, N.N. Samulevich, Kristallografiya 24 (1979) 461. [4] S. Qiu, J. Yu, G. Zhu, O. Terasaki, Y. Nozue, W. Pang, R. Xu, Microporous Mesoporous Mater. 21 (1998) 245. [5] J. Warzywoda, N. Bac, A. Sacco Jr., J. Crystal Growth 204 (1999) 539. [6] H. Khatami, E.M. Flanigen, N.R. Mumbach, in: J.B. Uytterhoeven (Ed.), Recent Progress Reports, Third International Conference Molecular Sieves, Leuven University Press, 1973, p. 183. [7] S. Vasenkov, H. Frei, J. Phys. Chem. 101 (1997) 4539. [8] D.E.W. Vaughan, US Patent 4 965 059, 1990. [9] B.D. Cullity, Elements of X-ray Diffraction, 2nd Edition, Addison-Wesley, Reading, MA, 1978 (Chapter 8,9). [10] D.W. Breck, Zeolite Molecular Sieves, Krieger Publishing Company, Malabar, FL, 1984, p. 421. [11] W.W. Simons (Ed.), The Sadtler Handbook of Infrared Spectra, Sadtler Research Laboratories, Pennsylvania, 1978.
Synthesis of large single crystals of templated Y faujasite Samia Ferchichea, Maria Valcheva-Traykovaa, David E.W. Vaughanb, Juliusz Warzywodaa, Albert Sacco Jra,* a
Center for Advanced Microgravity Materials Processing, Department of Chemical Engineering, 147 Snell Engineering Center, Northeastern University, Boston, MA 02115-5000, USA b Materials Research Laboratory, Pennsylvania State University, University Park, PA 16802, USA Received 3 August 2000; accepted 1 November 2000 Communicated by R.W. Rousseau
Abstract Large single crystals of zeolite Y with diameters up to 210–245 mm and Si/Al=1.71 have been synthesized from a reaction mixture (4.76Na2O : 1.0Al2O3 : 3.5SiO2 : 454H2O : 0.6T2O : 5TEA) comprising fumed silica (Cab-O-Sil M5), sodium aluminate, and the template bis(2-hydroxyethyl)dimethylammonium chloride (TCl) in an aqueous triethanolamine (TEA) cosolvent. # 2001 Elsevier Science B.V. All rights reserved. PACS: 81.05.Rm; 81.10.ÿh; 81.10.Dn Keywords: Crystal growth; Large zeolite crystals; Hydrothermal synthesis; Zeolite Y
1. Introduction Faujasites (FAU) of different Si/Al ratios are widely used as catalysts and sorbents, the former mainly utilizing the higher ratios (Y-type) and the latter the lower ratio X-types. Single crystals of synthetic aluminosilicate zeolites with the FAU structure, large enough for conventional singlecrystal X-ray analysis have been grown only with framework Si/Al51.5, characteristic of the FAU-X type [1–5]. This is the first report of the growth of such large crystals of the FAU-Y type with Si/Al>1.5; earlier work reported single FAUY crystal sizes only up to about 40 mm [6,7]. Using *Corresponding author. Tel.: +1-617-373-7910; fax: +1617-373-2209. E-mail address: [email protected] (A. Sacco Jr).
the general procedure developed for the growth of large crystals of FAU-X [5] together with the template used to make ECR-4 [8] (FAU with Si/Al>3), 210–245 mm single crystals of FAU-Y with a Si/Al=1.71 have been synthesized.
2. Experimental Syntheses were from gels of composition: 4.76 Na2O : 1.0Al2O3 : 3.5SiO2 : 454H2O : 0.6T2O : 5TEA formed by mixing aqueous silica slurries and TEA- [1] and TCl- [8] containing sodium aluminate solutions. The silica slurries were prepared in 30-ml polyethylene (HDPE) bottles by suspending 0.58 g of Cab-O-Sil M-5 fumed silica (Cabot) in 10 g of deionized water (resistivity>
0022-0248/01/$ - see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 0 0 ) 0 0 9 7 9 - 9
802
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
Table 1 The results of synthesis of large FAU-Y crystals Double filtration of TEA/TCl-sodium aluminate stock solution
No No No Yes Yes Yes Yes
Time of mixing of gel (h)a
5 24 24 24 24 5 5
Synthesis time (d)
14 14 15 16 18 18 18
Particulate product
Diameter of largest FAU (mm)b
Diameter of largest GIS (mm)b
Amount of GIS in the product (number %)c
140–175 140–175 210–245 210–245 210–245 210–245 210–245
100–125 100–125 125–160 125–160 125–160 125–160 125–160
50–60 50–60 20–30 20–30 20–30 20–30 20–30
a
Elapsed from preparing TEA/TCl-sodium aluminate stock solution. SEM analysis. c Optical microscope analysis. b
18 MO cm). The sodium aluminate ‘‘stock’’ solutions were prepared in 250-ml HDPE bottles by dissolving 6.47 g of sodium aluminate powder (NaAlO2 0.14H2O, technical, EM Science) in hot solutions of 11.51 g of sodium hydroxide (pellets, 97+%, Acros Organics) dissolved in 170 g of deionized water. Immediately after cooling, the aluminate solutions were filtered through 0.2-mm membrane filters (Supor-200, Gelman). This is necessary because unreacted nano-crystals of alumina in the sodium aluminate are known to act as seeds in zeolite syntheses. TEA (99+%, Acros Organics) and TCl (99%, Acros Organics) were added to the filtered sodium aluminate solutions in the amount of 15.19 and 4.19 g/100 g of the filtered aluminate solution, respectively. TEA/TCl-sodium aluminate solutions were filtered again through 0.2-mm membrane filters. Products grown from stock solutions, which were not filtered after addition of TEA and TCl usually resulted in larger amounts of polycrystalline impurity phases and smaller FAU crystals (see Table 1). TEA/TCl-sodium aluminate stock solutions were typically held at room temperature (208C) for several hours before combining 16.03 g of the stock solution with the silica slurries in 30-ml HDPE bottles. The bottles were then sealed, hand-shaken for 15–20 s then heated
statically in a convection oven at 958C for 2–3 weeks. The products were filtered, washed with deionized water, and dried for 24 h at 808C before analysis. Scanning electron microscope (SEM) images of the uncoated crystals were obtained on a Hitachi S-4700 cold field emission SEM using the upper secondary electron detector, 1–3 kV accelerating voltage, and 10 mA emission current. The X-ray powder diffraction (XRD) data were obtained on a Bruker D5005 y :2y Bragg–Brentano diffractometer equipped with a curved graphite crystal diffracted beam monochromator and NaI scintillation detector using Cu Ka radiation. The XRD data were collected with a step increment of 0.028 2y and a count time of 5 s/step. To minimize preferred orientation effects, specimens for XRD analysis were ground to a fine powder. Samples for single-crystal X-ray analysis were prepared by adhering the crystals onto the ends of glass fibers. The data were acquired on a Bruker General Area Detector Diffraction System Type 4 equipped with a one-position w stage at 54.748 using Cu Ka radiation. The crystals were examined in the transmission regime using a 0.2-mm collimator and a detector-to-sample distance of 6 cm. Fourier transform infrared (FTIR) spectra were obtained on a Nicolet Magna-IR 560 spectrometer equipped with a Spectra-Tech Collector diffuse
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
803
reflectance apparatus. The spectra (128 scans with a resolution of 2 cmÿ1) were collected at room temperature in air using 10 wt% of sample mixed with KBr. The solid-state 29Si NMR experiment was performed at 9.4 T on a homebuilt 400 MHz spectrometer at 79.46 MHz utilizing a Tecmag Libra system for pulse programming and signal digitization. The spectrum was collected at room temperature using a 5 mm Chemagnetics tripleresonance probe with rotor frequency of 5 kHz which was stabilized to 2 Hz using an active feedback spin-rate controller. A total of 2524 scans were collected using a 9 ms p/2 pulse and 60 s pulse delay as determined for a zeolite Na-A sample. 50 Hz of line broadening was applied to the spectrum. The spectrum is referenced relative to a TMS sample. Fig. 1. The SEM image of a large FAU-Y crystal.
3. Results and discussion The products contained the particulate material and variously sized ‘‘crusts’’ consisting of the aggregated octahedral crystals and/or polycrystalline spherical impurities. Examples of the specific processing conditions and the corresponding particulate products are shown in Table 1. SEM, optical microscopy, and XRD showed that the particulate products were mixtures of large transparent FAU octahedra with diameters up to 175–245 mm (Fig. 1) and of translucent polycrystalline spheres of the zeolite gismondine (GIS, Pc, Pt). The spherical impurities, with particle diameters generally larger than 100 –125 mm, were estimated (visually) not to exceed 20 –60% (by number) of the particulate product (Table 1). The maximum size of the FAU crystals and the amount of the GIS impurity depended on the method of the TEA/TCl-sodium aluminate solution preparation. Products grown from solutions which were not filtered after addition of TEA and TCl usually resulted in excessive amounts (up to 60%) of GIS spheres and smaller (up to 140– 175 mm) FAU crystals. Double filtration consistently resulted in products containing larger (up to 210–245 mm) FAU crystals contaminated by smaller (up to 30%) amounts of GIS. One higher purity sample was further purified by
Fig. 2. The
29
Si MAS NMR spectrum of FAU-Y.
removing the readily recognized GIS spheres with the aid of an optical microscope ( 300) then analyzed by solid-state 29Si NMR (Fig. 2), giving Si/Al=1.71, and confirming that the FAU crystals were type-Y. The typical stereographic projections of the large octahedral zeolite Y crystals (Fig. 3) showed that they are single crystals. The practically identical intensities of the spots (Fig. 3a) indicate a nearly uniform distribution of Si and Al in the
804
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
(Fig. 1). The micro-tension illustrated in Fig. 3 can be due to localization of bis(2-hydroxyethyl) dimethylammonium cations in large supercages parallel to the [1 1 1] direction [8]. The presence of bis(2-hydroxyethyl)dimethylammonium cations in the zeolite Y structure is illustrated in Fig. 4. As expected [10], the characteristic asymmetric (1140, 1065 cmÿ1) and symmetric (782, 710 cmÿ1) stretching T–O–T bond vibrations of FAU-Y synthesized in the presence of TCl (Fig. 4b) are shifted to the higher frequencies in comparison to its lower ratio counterpart (FAU-X, Si/Al 1.4) synthesized in the absence of TCl [5] (1124, 992 cmÿ1 and 759, 681 cmÿ1, respectively) (Fig. 4a). In the FTIR spectrum of FAU-Y collected using FAU-X grown without TCl as a background (Fig. 4c), the band at 992 cmÿ1 disappeared whereas the new bands appeared at approximately 1485 (with a shoulder at approximately 1440), 1155, and 790 cmÿ1. The band at approximately 1485 cmÿ1 is a characteristic deformation C–N bond vibration in N–CH3, while the shoulder at approximately 1440 cmÿ1 is O–H deformation in the C–OH in the amine [11]. The band at 1155 cmÿ1 is assigned to C–O
Fig. 3. Intensities (a) and shapes (b) of the spots in the stereographic projection of a large FAU-Y crystal along [1 1 1] direction.
zeolite framework, whereas their shapes (Fig. 3b) show some stress and micro-tension in the crystals along the [1 1 1] direction. The stress can be related to imperfections of the crystal habit [9]. SEM observations showed that apices of the octahedral crystals do not end in a sharp point and that crystal edges do not form totally straight lines
Fig. 4. FTIR spectra of (a) FAU-X synthesized in the absence of TCl with KBr background, (b) FAU-Y synthesized in the presence of TCl with KBr background, (c) FAU-Y using FAUX as a background, (d) mechanical mixture of TCl and FAU-X.
S. Ferchiche et al. / Journal of Crystal Growth 222 (2001) 801–805
stretching vibration of HO–C–NR3 [11]. The band at 790 cmÿ1 is typical for the primary amine [11]. The comparison of the positions of the characteristic bands of TCl in a mechanical mixture with FAU-X grown without TCl (Fig. 4d) and in FAU-Y grown with TCl (Fig. 4b) suggests that the bis(2-hydroxyethyl)dimethylammonium cation is present in the zeolite Y structure.
4. Conclusions Using an easy, reproducible method, large single crystals of zeolite Y have been synthesized which are suitable for single-crystal diffraction experiments. Modifications to the approach should provide a range of Si/Al ratio crystals. The ready availability of such materials will stimulate the improved characterization of numerous catalytic and sorbent faujasites, leading to a greater understanding of their functions and to improved commercial products.
Acknowledgements The authors acknowledge the financial support of NASA, and thank Teri Lalain and Prof. Karl
805
Mueller (Department of Chemistry, Pennsylvania State University) for the 29Si NMR spectrum.
References [1] J.F. Charnell, J. Crystal Growth 8 (1971) 291. [2] For review of methods of synthesis of large zeolite X crystals see: E.N. Coker, J.C. Jansen, in: H.G. Karge, J. Weitkamp (Eds.), Molecular Sieves } Science and Technology, Vol. 1, Synthesis, Springer, Berlin, 1998, p. 121. [3] Yu.I. Smolin, Yu.F. Shelepev, I.K. Butikova, S.P. Zhdanov, N.N. Samulevich, Kristallografiya 24 (1979) 461. [4] S. Qiu, J. Yu, G. Zhu, O. Terasaki, Y. Nozue, W. Pang, R. Xu, Microporous Mesoporous Mater. 21 (1998) 245. [5] J. Warzywoda, N. Bac, A. Sacco Jr., J. Crystal Growth 204 (1999) 539. [6] H. Khatami, E.M. Flanigen, N.R. Mumbach, in: J.B. Uytterhoeven (Ed.), Recent Progress Reports, Third International Conference Molecular Sieves, Leuven University Press, 1973, p. 183. [7] S. Vasenkov, H. Frei, J. Phys. Chem. 101 (1997) 4539. [8] D.E.W. Vaughan, US Patent 4 965 059, 1990. [9] B.D. Cullity, Elements of X-ray Diffraction, 2nd Edition, Addison-Wesley, Reading, MA, 1978 (Chapter 8,9). [10] D.W. Breck, Zeolite Molecular Sieves, Krieger Publishing Company, Malabar, FL, 1984, p. 421. [11] W.W. Simons (Ed.), The Sadtler Handbook of Infrared Spectra, Sadtler Research Laboratories, Pennsylvania, 1978.