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J . Phys. Chem. 1989, 93, 6516-6520
lyotropic electrolyte sodium chloride increases ps, while pa remains more or less constant, and at constant temperature shifts the three-phase region to higher pressures.
VI. Conclusions It follows from our measurements that pressure can have a considerable influence on the phase behavior of water oil nonionic surfactant systems. If a system shows a three-phase region at atmospheric pressure, this region widens with increasing pressure. If a system does not show such a region it can be induced by increasing the pressure or by adding a lyotropic electrolyte like sodium chloride. At constant temperature 2-3-2 phase transitions were observed
+
+
with increasing pressure, which means that the surfactant becomes more hydrophilic. At a molecular level this is probably due to the building of hydrogen bonds between water and the hydrophilic part of the surfactant molecule, which energetically becomes more favorable at higher pressures. Acknowledgment. We are indebted to Prof. Dr. M. Kahlweit and Dr. R. Strey of the Max-Planck-Institut fur biophysikalische Chemie, Gottingen, West Germany, for suggesting this study and for introducing one of us (C.L.S.) into this field of research. We also thank the Koninklijke/Shell Exploratie en Produktie Laboratorium, Rijswijk, The Netherlands, for financial support. Registry No. NaC1, 7647-14-5; C4E2,112-34-5; phenylheptane, 1078-71-3;phenyloctane, 2189-60-8; phenylhexane, 1077-16-3.
Silicoaluminophosphate with Encapsulated Methylbutylamine Species: Chabazite Structure, Charge Coupltng between Framework and Inferred Ammonium Species, and Severe Molecular Disorder Joseph J. Pluth* and Joseph V. Smith Department of Geophysical Sciences and Materials Research Laboratory, The University of Chicago, Chicago, Illinois 60637 (Received: February 16, 1989)
The crystal structure of the as-synthesized precursor to molecular sieve SAPO-47 was determined by single-crystal X-ray diffraction: ~A16,0(Sil,4P4,6)024~1.4CSH12NH2~(2.5HZO)r M , = 895.6, rhombohedral, R3, a = b = c = 9.3834 (8) A, a = p = y = 94.085 (8)", V = 819.58 (12) A3, D, = 1.82 g ~ m - X(Mo) ~, = 0.71069 A, fi = 5.57 cm-', F(000) = 455, T = =295 K, R = 0.070 for 2000 diffraction intensities. A 4-connected framework of chabazite type has A102 tetrahedra alternating with (P, Si)04tetrahedra. The ellipsoidal cages share 8-rings to generate a three-dimensionalchannel system. The encapsulated molecules residing in the channels are strongly disordered, and only one sharp peak was observed in the electron density map. Four possible models were investigated by constrained least-squares refinement, but a unique position was not obtained for the encapsulated methylbutylamine species. It seems likely that each change deficiency of the framework is balanced by a methylbutylammonium ion, and that only the N and C atoms close to framework oxygens are well-defined in response to bifurcated hydrogen bonding and weaker van der Waals bonding. The other C atoms occupy a range of positions in response to the large variation of crystal fields resulting from significant Si substitution in P sites. Minor substitution of Si in AI sites is allowed but not required by the chemical and crystallographic data. The water content is not known accurately, and the listed value of 2.5H20 per cell for a bulk sample may be too high.
Introduction A new class of microporous materials was synthesized from aluminophosphate (APO) gels with a wide range of organic amines and quaternary ammonium cations as structure-directing agents,'J and their physical and chemical properties are being studied intensively. The structural features of these microporous materials, and of other aluminophosphates with AI/P = 1, have been re~ i e w e d . Additional ~ structure types are classified in an addendum.4 Further generations of aluminophosphate-based molecular sieves, containing 1 or more of 13 additional elements, have been ~ynthesized.~Detailed refinements of the crystal structures of MnAPO- 1 l 6 and Mg-bearing aluminophosphate-43 (MAPO-43)' have demonstrated charge coupling between the framework and
an ionized organic species. In CoAPO-44 and CoAPSO-44, the encapsulated cyclohexylamine has an N atom pointing at an 8-ring of the chabazite-type framework.8 The crystallization conditions and chemical properties of a novel group of silicoaluminoand those for phosphates (SAPO) were disclosed by Lok et SAPO-47 are similar. Determination of the crystal structure of SAPO-47 is important for three reasons: first, to confirm that the framework topology is of chabazite type; second, to determine the location of the Si; and third, to find out the structural relation between the encapsulated organic species and the enclosing tetrahedral framework. The results are compared with those for SAPO-34 (chabazite type),1° SAPO-37 (faujasite type)," and SAPO- 1 1 l 2 and discussed in the context of the latest review of
(1) Wilson, S. T.; Lok, B. M.; Messina, C. A.; Cannan, T. R.; Flanigen, E. M. J . Am. Chem. SOC.1982, 104, 1146. (2) Wilson, S. T.; Lok, B. M.; Messina, C. A,; Cannan, T. R.; Flanigen, E. M. ACSSymp. Ser. 1983, No. 218, 79. (3) Bennett, J. M.; Dytrych, W. J.; Pluth, J. J.; Richardson, J. W., Jr.; Smith, J. V. Zeolites 1986, 6, 349. (4) Bennett, J. M.; Pluth, J. J.; Smith, J. V. Zeolites, submitted for pub-
(8) Bennett, J. M.; Marcus, B. K. Innovations in Zeolite Materials Science, Proceedings of an International Symposium, Nieuwpoort, Belgium, 1987. Stud. Surf. Sei. Catal. 1988, 37, 269. (9) (a) Lok, B. M.; Messina, C. A.; Patton, R. L.; Gajek, R. T.; Cannan, T. R.; Flanigen, E. M. U S . Patent 4,440,871, April 3, 1984. (b) Lok, B. M.; Messina, C. A.; Patton, R. L.; Gajek, R. T.; Cannan, T. R.; Flanigen, E. M. J . Am. Chem. SOC.1984, 106, 6092. (IO) Ito, M.; Shimoyama, Y.; Saito, Y.; Tsurita, Y.; Otake, M . Acta Crystallogr., Sect. C 1985, 41, 1698. ( 1 1 ) Saldarriaga, L. S. de; Saldarriaga, C.; Davis, M. E. J . Am. Chem. Sot. 1987, 109, 2686. (12) (a) Mentzen, B. F.; Vedrine, J. C.; Khouzami, R. C.R. Acad. Sci., Ser. 2 1987, 304, 11. (b) Mentzen, B. F.; Vtdrine, J. C.; Khouzami, R.; Coudurier, G . C. R . Acad. Sei., Ser. 2 1987, 305, 263.
lication.
( 5 ) Flanigen, E. M.; Lok, B. M.; Patton, R. L.; Wilson, S. T. Pure Appl. Cfiem. 1986. 58. 1351. (6) Pluth, J. J.; Smith, J. V.; Richardson, J. W., Jr. J . Phys. Chem. 1988, 92, 2734. (7) Pluth, J. J.; Smith, J. V.; Bennett, J. M. J . Am. Cfiem.SOC.1989, 111. 1692.
0022-3654/89/2093-65 16$01.50/0 0 1989 American Chemical Society
Silicoaluminophosphate with Methylbutylamine structural, synthetic, and physicochemical concepts of aluminophosphate-based molecular sieves.13 Particularly important for discussion of the location of the Si atoms are the N M R data11*'"17 for various SAPO materials. Experimental Section The sample was synthesized according to the procedures in ref 9, with use of methylbutylamine as the structure-directing agent. After being sieved, the sample consisted of a single population of 0.1-0.2-mm crystals, almost all fastened into aggregates. All faces appear to be rhombohedral, except for those affected by adjacent crystals. In transmitted polarized light, the extinction is symmetrical and uniform. The angular relations between interpenetrating crystals appear to be random and not indicative of twinning. Extensive search yielded a crystal with only a small appendage. Weissenberg X-ray photographs showed single sharp spots with excellent a I ,a2resolution at high angles. These data indicate strict rhombohedral symmetry. A chemical analysis (SO2, 9.1; A1203,33.1; P2OS,39.0; C, 9.3; N, 2.2; loss on ignition, 18.7 wt %) of the bulk sample on a hydrated basis yielded the following normalized fractions for the framework T-atoms: Si, 0.1 12; Al, 0.48 1; P, 0.407. This yields the following number of atoms for the 12 tetrahedral sites of the chabazite unit cell: AI, 5.77; Si, 1.35; P 4.88. The contents of C and N correspond closely to the expected atomic ratio of 5 for methylbutylamine, and addition of the 14 hydrogen atoms raises the contribution of the encapsulated species to 13.7 wt %. The remaining 5.0 wt % in the loss on ignition could be attributed to water, but no direct analysis was made. Electron microprobe analysis was performed with a Cameca Model SX-50 instrument (wavelength-dispersive system; 15 kV; standards, AI and Si referred to synthetic anorthite, P to synthetic c a 2 P 2 0 7 ;PAP correction program). Test analyses of A1PO4-5 crystals yielded oxide totals near 87%, and AI/P = 1 within experimental uncertainty. Repeat analyses on the same spot with a 20-" beam were constant within counting statistics. For SAPO-47, oxide totals were 83-85%, no chemical zoning was found within counting statistics, and the mean number of atoms per 12 tetrahedral sites was 5.90 for Al, 1.37 for Si, and 4.73 for P for 23 analyses of four crystals. Although this analysis is similar to the bulk chemical analysis, the Al/P ratio is higher. Because the SAPO-47 crystals contain opaque inclusions that may be trapped gel and because bulk samples may be impure, the bulk analyses of AI, P, and Si may be biased. Consequently, the electron microprobe analysis is preferred and used here for the interpretation of the crystal structure. With the standard valences of 3, 4, and 5 for Al, Si, and P, respectively, the above numbers of atoms correspond to 46.8 framework charges per unit cell. There are also 24 oxygens present, so the net framework charge is -1.2. The charge can be balanced by converting 1.2 methylbutylamine molecules to ammonium species during syntheis and subsequent encapsulation by the framework. This value is similar to, but smaller than, the number of 1.4 methylbutylamine species indicated by the bulk chemical analysis. The estimated number of ionized molecules is very sensitive to any experimental error in the Al/P ratio. Thus, the composition A16,$i1,4P4,6yields 46.6 framework charges and would require 1.4 methylbutylammonium ions. In the other direction, the bulk chemical analysis yields 47.1 framework charges and would require only 0.9 methylbutylammonium ion. It is impossible to reach an objective conclusion, but a convenient simple composition is [A16,$il,4P4,6024]-1 .4(CH,NH2C4H9).nH20. For the 5 wt % H 2 0 inferred from the bulk chemical analysis, n = 2.5. For the oxide total of the electron (13) Flanigen, E. M.; Patton, R. L.; Wilson, S. T. Innovations in Zeolite Materials Science, Proceedings of an International Symposium, N i e u w p r t , Belgium, 1987. Stud. Surf. Sci. Catal. 1988, 37, 13. (14) Blackwell, C. S.; Patton, R. L. J . Phys. Chem. 1988, 92, 3965. (15) Hasha, D.; Saldarriaga, L. S. de; Saldarriaga, C.; Hathaway, P. E.; Cox. D. F.; Davis, M . E. J . Am. Chem. SOC.1988, 110, 2127. (16) Aoolevard. 1. P.: Harris. R. K.: Fitch. F. R. Chem. Lett. 1985. 1747. (17j Fiiudk, D.; Ernst, H.; Hunger,'M.;Pfeifer, H.; Jahn, E. Chem: Phys. Lett. 1988, 143, 477.
The Journal of Physical Chemistry, Vol. 93, No. 17, 1989 6517 microprobe analysis (83-85%), and 13.7 wt % organic, the difference from 100% is only 2 f 1%. This corresponds to n = 1. Because the bulk sample contains trapped gel, the LO1 may give too high a value for crystalline water. Totals from electron microprobe analysis may be subject to a systematic error. Consequently, it is concluded that the water content has not been determined reliably from the present data. Whatever the uncertainty in the exact chemical composition, there is no doubt that there is Si, P disorder in the framework and complex disorder of the encapsulated species. Data Collection. The selected crystal (near-rhombohedron; 0.13 X 0.13 X 0.10 mm) was coated with oil to control humidity and mounted on an automated Picker-Krisel four-circle diffractometer with a offset by 6.5O from the 4 axis. Refinement with angles from 20 centered diffractions (38 < 28 < 43O), each the average of the automatic centering of 8 equivalent settings, gave the cell parameters in the abstract. A total of 63 1 1 diffraction intensities was collected with the 8-28 technique: scan speed 2O/min, scan width 1.8-2.3O for the range 3-65O in 28. Merging yielded 2000 unique intensities (Rint= 0.03), all of which were used in refinements: data collection range h (+14), k ( f 1 4 ) , 1 (f14); maximum intensity variation of three standard reflections 0.2%. No absorption correction was applied because of the small crystal size and absorption coefficient. Rotation around the diffraction vector indicated no significant absorption. Atomic coordinates for chabazite were used as the starting parameters for refinement of the framework atoms. The parameter set was expanded to allow for the alternation of A1 and (P, Si), and the consequent reduction of symmetry from R3m to R3. A difference Fourier map showed only one clear electron density peak (-2.1 e/A3) for the extra-framework species. This peak is offset from the center of an 8-ring and its image (related by a center of symmetry) on the other side is about 1.6 A away. Refinement of the framework parameters alone resulted in R = 0.086, R, = 0.139 and inclusion of the largest peak gave R = 0.077, R, = 0.110. Numerous attempts to locate a methylbutylamine species and the water in single, well-defined positions failed. It seems plausible that the single peak represents two adjacent atoms of the backbone of the methylbutylamine species that are bonded to framework oxygen atoms of the enclosing 8-ring and that the remaining four atoms occupy a range of positions that differ from one pore to the next. The water molecules were ignored for the time being. The sequence of atoms in the molecule is defined as follows: C( I)-N-C(2)-C(3)-C(4)-C(5).Refinements of four models were completed. Starting parameters for model A had C( 1) and N; model B, C(2) and C(3); and model C, N and C(2) in positions near the center of the 8-ring and the remaining atoms at appropriate sites projecting into the elliptical cages. Model D had the terminal carbons, C ( l ) and C(5), occupying two sites in the same cage and connected together by N-C(2)-C(3)-C(4). Refinement of the models to convergence gave the following residuals for models A-D, respectively: RA = 0.070, R,, = 0.068, SA = 3.8; RB = 0.070, RwB= 0.065, S B = 3.6; R c = 0.070, Rwc = 0.065, Sc = 3.6; RD = 0.065, R,D = 0.055, SD= 3.0. In all models, there are two atoms fairly close to framework oxygens of the 8-ring. Because it seemed to be the most crystal chemically reasonable, the parameters of model A are presented in this paper even though statistical tests (Hamilton's R-test'*) would favor model D. Final parameters for the remaining models are available as supplementary material. In the final model, 78 variables were refined: scale factor, atomic positions, anisotropic displacement factors for framework atoms, individual occupancy factors for A1 and P, and an overall occupancy factor and two isotropic thermal parameters (one for the two atoms near the center of the 8-ring and one for the remaining atoms) for the encapsulated molecule. Neutral scattering factorsIg were used. The lower population factor for the (18) Hamilton, W. C. Statistics in Physical Science; Ronald Press: New York, 1964. (1 9) International Tables for X-ray Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol IV, pp 72-98.
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TABLE I: Atomic Positions and DisDlacements of SAPO-47. Model A atom population' X AI 6 X 0.912 (3) 0.098 88 (9) 0.33245 (sj 6 X 0.895 (3) 0.2580 (3) 6 X 1.0 0.151 9 (2) 6 X 1.0 0.2542 (2) 6 X 1.0 0.0291 (3) 6 X 1.0 -0.132 (2) 6 X 0.344 (3) 0.009 (2) 6 X 0.344 (3) 0.112 (2) 6 X 0.344 (3) 0.189 (2) 6 X 0.344 (3) 0.334 (2) 6 X 0.344 (3) 0.449 (2) 6 X 0.344 (3) Population defined as site multiplicity X fractional occupancy.
U,
TABLE 11: SAPO-47, Model A Framework, Showing Interatomic Distances (A) and Angles (deg)
P-O( 1 ~ - 0 i j2 P-0(3) P-0(4)
Distances centroid 1.536 (3) 1.541 (3j 1.531 (3) 1.530 (3)
riding" 1.554 (3) 1.555 (3j 1.549 (3) 1.552 (3)
mean
1.535
1.552
A1-0(1) A1-0(2) A1-0(3) A1-0(4)
1.732 (3) 1.726 (3) 1.716 (3) 1.725 (3)
1.749 (3) 1.739 (3) 1.733 (3) 1.744 (3)
mean
1.725
1.741
~~
Angles O(l)-P-O(2) O(I)-P-0(3) O(l)-P-O(4) 0(2)-P-0(3) 0(2)-P-0(4) 0(3)-P-0(4) 0(1)-AI-0(2) 0(1)-A1-0(3)
08.4 ( I ) 10.3 ( I ) 10.4 ( I ) 107.6 (1) 110.8 ( I ) 109.3 ( I ) 108.3 (1) 110.4 (1)
0(1)-A1-0(4) 0(2)-A1-0(3) 0(2)-A1-0(4) 0(3)-AI-0(4) P-O(1)-AI P-O(2)-A1 P-O(3)-A1 P-O(4)-AI
109.1 (1) 107.6 ( I ) 111.1 (1) 110.3 (1) 145.1 (2) 147.0 (2) 150.3 (2) 149.7 (2)
"Oxygen riding on tetrahedral atom.
P position than for the A1 position is consistent with the expectation from the chemical analysis that 23% of the P sites are occupied by Si. The final least-squares refinement minimized F and included all measured Fs with aF computed from U I , the square root of [total counts + (2% of total count^)^]: R A = 0.070, R,A = 0.068, SA = 3.8: maximum shift/esd < 0.1; maximum and minimum heights on final difference Fourier map are 0.9 and -0.5 e A-3. Computer programs: local data reduction, SHELX76," ORFFE,~'and O R T E P . ~ ~Final atomic coordinates and displacement factors are given in Table I and interatomic distances (with and without riding motion) and angles in Tables I1 and 111. Tables of anisotropic thermal parameters for models A-D, tables of atomic positions and displacements for models B-D, and a listing of observed and calculated structure factors are available as supplementary material. Discussion Framework Topology. The structure refinement definitely demonstrates that the framework atoms have the connectivity of the chabazite net (Figure 1). SAPO-47 and chabazite are composed of double 6-rings stacked in the sequence AABBCC. The stacking produces elliptical cages bounded by six 8-rings and (20) Sheldrick, G. M., computer program, Cambridge University, Cambridge, England. (21) Busing, W. R.; Martin, K.; Levy, H. A. Oak Ridge National Loboraiory, [Report] ORNL-TM (US.); ORNL-TM-306; U S . National Laboratory: Oak Ridge, TN, 1964. (22) Johnson, C. K. Oak Ridge National Laboratory, [Report] ORNL ( U X ) ; ORNL-3794; U S . National Laboratory: Oak Ridge, TN, 1965.
Pluth and Smith
Y 0.331 96 (9) 0.108 47 (8) -0.2704 (2) -0.1445 (3) 0.246 0 (2) 0.0104 (3) 0.524 (3) 0.480 (2) 0.492 (2) 0.353 (2) 0.382 (2) 0.303 (3)
z
u,"
0.875 I O (10) 0.87466 (8) -0.0127 (3) 0.491 1 (2) 0.8876 (3) 0.3178 (3) 0.500 (3) 0.551 (2) 0.440 (3) 0.424 (3) 0.359 (2) 0.439 (3)
0.0152 (3) 0.0149 (2j 0.0350 (7) 0.0307 (7) 0.0352 (7) 0.0381 (8) 0.227 (4) 0.227 (4) 0.404 (4) 0.404 (4) 0.404 (4) 0.404 (4)
(A2)defined as I/jCi-13Cj,,3Uipi*a,* (araj). twelve 4-rings. The cages can easily accommodate the encapsulated molecule methylbutylamine. Framework Topochemistry. The bulk chemical and electron microprobe analyses indicate that about one-fourth of the P sites and possibly a small fraction of the A1 sites are occupied by Si. Although it is necessary to be cautious in any deduction of chemical occupancy from T-0 distances, the mean tetrahedral distances in Table I1 are consistent with this assumption; thus, the distances adjusted for riding motion tend to be larger than those for P-0 and less than those for A 1 4 in aluminophosphate structures. Magic angle spinning nuclear magnetic resonance spectra for 29Si,27A1,and 31Pwould provide further information about the distribution of atoms on the tetrahedral sites. Location and Bonding of the Methylbutylamine Species. The calculation of charge balance for the chemical and electron microprobe analyses indicates that up to about l .4 methylbutylammonium ions are needed per cage. It will be assumed that the methylbutylamine species does not fragment or polymerize during synthesis. Furthermore, the four population refinements for the different positions of the CNC4 backbone of the encapsulated species indicate that about one and one-third species occupy the average cage when account is taken of the omitted hydrogen atoms. [At low diffraction angles, about 30% of the scattering is from hydrogen atoms, and the refined population factor in Table I must be reduced correspondingly.] Hence, it is assumed that all or mast of the encapsulated species are ionized into ammonium ions. Each ellipsoidal cage shares an 8-ring with six adjacent cages. Hence, 1.4 methylbutylammonium ions per cage corresponds to occupancy of 2.8/6 = 47% of the 8-ring. This number is close to 50%. Examination of the four positions of the molecular backbone in the stereoplots of Figure 1 shows that each encapsulated species tends to block occupancy of one of the adjacent 8-rings and that it is difficult to assign molecules to more than 50% of the 8-rings. In all four models, the distances from C and N atoms to framework oxygen atoms range from about 2.7 to 3.5 A. Model A (see Table IV), in particular, has distances ranging from 2.8 to 3.0 A from the N atom to framework oxygens in the correct position to form hydrogen bonds having normal geometry. This is the preferred model from the crystal-chemical viewpoint. Water Content. The diffraction data do not require the presence of water molecules nor do they rule them out. From the viewpoint of bonding to framework oxygens, a water molecule might reside next to a 6-ring (as proposed for ZYT-61°) or an 8-ring. There is no significant electron density on the triad axis next to a 6-ring. The pair of peaks already assigned to C and N atoms lie at -3 A from framework oxygens of the 8-ring. These distances are plausible for occupancy of this site by H 2 0 . Because only half of the 8-rings are occupied by an organic species, the other half must be considered as a possible site for a water molecule. Only one peak out of each pair might be occupied because of the small separation (- 1.5 A). Full occupancy of half of the 8-rings would correspond to n = 1.5. Considering the diffraction data, all the electron density can be accounted for by just the organic species. However, population factors are notoriously imprecise for disordered species, and it is prudent to leave open the option that up to 1.5 H,O might reside next to an %ring. If water molecules
Silicoaluminophosphate with Methylbutylamine
The Journal of Physical Chemistry, Vol. 93, No. 17, 1989 6519
Figure 1. Stereoviews of the tetrahedral framework of four models for SAPO-47. (a) Model A, starting model had C(1)-N straddling the center of an 8-ring. (b) Model B, starting model had C(2)-C(3) straddling the center of an k i n g . (c) Model C, starting model had N-C(2) straddling the center of the 8-ring. (d) Model D, the terminal carbons C(l) and C(5) occupy sites near the centers of two 8-rings and the remaining atoms bridge across an elliptical channel. Only one organic species is shown per cage whereas about half the 8-rings are occupied in the actual structure.
occur elsewhere in the large cage, they do not reveal themselves at the noise level of the difference maps. Comparison with Structural Data on Other SAPO Materials. The conclusion that SAPO-47 has alternation of (P1-&) and (All-ySiy) where x is substantial and y is small or even zero is consistent with the overall MAS-NMR data for the SAPO species
listed in the Introduction. Furthermore, the value of x = 0.23 is similar to the value of x = 0.25 assumedt0 for ZYT-6, which also has the chabazite type of net but which contains encapsulated water rather than an organic species. Even the idealized value of 0.25 does not give an integral number of Si atoms per unit cell, and it is certain that the crystal field must vary from one cage
6520
Pluth and Smith
The Journal of Physical Chemistry, Vol. 93, No. 17, 1989
TABLE 111: SAPO-47 Interatomic Distances (A)and Angles (deg) Involving C and N Atoms of Template Molecule
distances intermolecular Values" 1.479 all C-C-C 1.541 all C-N-C all C-C-N
04
01
angles 109.5 109.5 109.5
/
03
Y
\
Framework Close Contactsb Model A 3.25 (2) 3.36 (2) 3.37 (2) 2.77 (2) 2.97 (2) 3.09 (2) 3.37 (2) 3.50 (2) 3.09 (2) 3.30 (2) 3.41 (2) 3.49 (2) 3.22 (2) 3.48 (2)
O(l)-C(l)-O(3) 0(1)-N-0(3)
86.9 (6) 104.3 (6) 01
O(I)-C(2)-0(3)
92.7 (6) 01 04
Figure 2. Proposed hydrogen bonding from NH2 (dashed lines) of the ionized organic species to framework oxygens of the %rings of SAPO-47.
Model B 3.20 (5) 3.36 (4) 3.43 (5) 2.64 (4) 3.05 (3) 3.16 (4) 3.28 (3) 3.35 (3) 3.22 (4) 3.29 (4) 3.43 (4)
0(1)-N-0(3)
89.8 ( I O )
O(l)-C(l)-0(3) O(l)-C(1)-0(3) 0(2)-C(1)-0(2)
102.3 ( I O ) 98.4 ( 1 1) 108.3 (1 1)
O(l)-C(3)-0(3)
87.0 (9)
Model C 3.24 (3) 3.34 (3) 3.39 (3) 2.66 (3) 3.02 (3) 3.21 (3) 3.22 (3) 3.40 (3) 3.20 (6) 3.21 (5) 3.49 (4)
0(1)-N-0(3)
86.8 (6)
O(l)-C(I)-0(3) O(l)-C(1)-0(3) 0(2)-C(1)-0(2)
103.4 (9) 96.8 ( I O ) 107.9 (10)
O(I)-C(3)-0(3)
92.4 (1 2)
Model D 3.17 (3) 3.26 (3) 3.34 (3) 3.38 (3) 3.39 (3) 3.43 (3) 3.18 (5) 3.28 (4) 3.45 (3) 3.46 (3)
_7 .d 9 1 ,
O(l)-C(1)-0(3) O(I)-C(1)-0(3)
90.3 (7) 90.6 (6)
O(l)-C(5)-0(3) 0(2)-C(5)-0(3)
82.7 (5) 127.6 (7)
(-41 \-I
a Refined as a group, allowing only torsional adjustments. less than 3.5 A and selected angles.
Values
to another in both materials. In SAPO-47, the chemical analyses indicates that there is almost enough C and N to give one organic unit for every two 8-rings, and it is tempting to suggest that the synthesis of SAPO-47 is controlled by charge linkage during conversion of the organic structure-directing agent into an am-
Observed displacement ellipsoids for the framework atoms are shown at the 50% probability level. Spheres for the atoms of the template molecule are arbitrary. monium ion. However, this suggestion could not explain the Si/P ratio of ZYT-6 that was reported to contain no organic material and an unknown amount of water. Since morpholine was used in its synthesis, it would be interesting to explore further the chemical composition and crystallographic properties of ZYT-6; incidentally, the space group R3 may be correct rather than the proposed R3 simply because the lower R factor could be a mathematical artifact of the assumed lower symmetry.
Conclusion SAPO-47 has a chabazite-type framework with alternation of (P, Si) and A1 tetrahedra, perhaps with minor substitution of Si for Al. The encapsulated organic species is strongly disordered, and a complete answer is not forthcoming from the present chemical and crystallographic data. However, they are consistent with ionization of the methylbutylamine to methylbutylammonium ion with an approximate one-to-one charge balance with occupancy of a P site by Si. Furthermore, nearly half of the 8-rings are occupied by an organic species in one or more positions consistent with hydrogen bonding between framework oxygens and the ammonium ion. How much water is present and where it might reside is uncertain. The present study had a limited goal, and further detailed measurements involving MAS-NMR and IR spectroscopy and thermogravimetry are needed to fully define the chemical and structural properties of SAPO-47. Acknowledgment. We thank S . T. Wilson and E. M. Flanigen for synthesis of the SAPO-47 and discussion of the results and I. M. Steele for electron microDrobe analvsis. Financial SUDDOrt was provided by N S F Grants kHE8618641 and DMR85i6460 (Materials Research Laboratory) and by Union Carbide Corp. Supplementary Material Available: Tables of anisotropic displacement parameters for models A-D and atomic positions and displacements for models B-D (7 pages); listings of observed and calculated structure factors (12 pages). Ordering information is given on any current masthead page.
