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AFI |
AlPO4-5 |
Al(50), P(50) |
Contributed by Juergen Caro and Irma Girnus
Verified by S. Cresswell, by B. Weckhuysen, and by G. Schulz-Ekloff
Type Material Al12P12O48
Method I. Girnus, K. Jancke, R. Vetter, J. Richter-Mendau, J. Caro [1] a
Batch Composition Al2O3 : 1.3 P2O5 : 1.6 TEA : 1.3 HF : 425 H2O : 6 C3H7OH b
Source Materials
deionized water
orthophosphoric acid (Merck, 85 wt% H3PO4)
triethylamine (TriEA), (Riedel de Haen, (C2H5)3N) c
aluminum triisopropylate (Merck, Al(C3H7O)3) d
hydrofluoric acid (Merck, 40 wt% HF in water)
Batch Preparation (for 3 g product)
(1) [7 g water + 3.84 g of phosphoric acid], mix
(2) [(1) + 2.07 g TriEA], add TriEA dropwise and mix
(3) [(2) + 5.23 g aluminum isopropylate], add in small amounts at 00C with intense stirring then stir the mixture at room temperature for 2 hours
(4) [(0.83 g hydrofluoric acid + 89.2 g water], mix
(5) [(3) + (4)], stir for 2 hours
Crystallization
Vessel: 150 mL Teflon-lined steel autoclavese
Temperature: 1800C (preheated oven)
Time: 6 hours f
Agitation: none
Product Recovery
(1) Decant the supernatant liquid and discard
(2) Wash the precipitate four times with 100 mL deionized water
(3) Calcine in air at 6000C until product is colorless (white) g
(4) Yield: near 100% on Al2O3
Product Characterization
XRD: Characteristic strong reflections at d = 11.90, 5.93, 4.48, 4.24, 3.96, and 3.42 Å; competing phases (if present): tridymite
Elemental Analysis: 42.9 wt% P2O5, 30.5 wt% Al2O3 (P/Al = 1.00)
Crystal size and Habit: Hexagonal columns up to 50 um h
Click here to view XRD pattern
References
[1] I. Girnus, K. Jancke, R. Vetter, J. Richter-Mendau, J. Caro, Zeolites 15 (1995) 33
[2] S. T. Wilson, B. M. Lok, C. A. Messina, T. R Cannan, E M. Flanigen, J. Am. Chem. Soc. 104 (1982) 1146
[3] J. M. Bennett, J. P. Cohen, E M. Flanigen, J. J. Pluth, J. V. Smith, ACS Symp. Series 218, Am. Chem. Soc., Washington, D. C., 1983, p. 109
[4] S. Oju, W. Pang, H. Kessler, J.-L Guth, Zeolites 9 (1989) 440
[5] A. S. T. Chiang, C.-K. Lee, Z. H. Chang, Zeolites 11 (1991) 380
[6] G. Finger, J. Richter-Mendau, M. Bulow, J. Kornatowski, Zeolites 11(1991) 443
[7] D. Demuth, G. D. Stucky, K. K. Unger, F. Schüth, Micropor. Mater. 3 (1994) 473
[8] I. Girnus, K. Hoffmann, F. Marlow, G. Döring, J. Caro, Micropor. Mater. 2 (1994) 537
Notes
a. The decisive difference of this synthesis from that of Wilson and Flanigen [2,3]is the use of HF as proposed by Kessler and Guth [4]. However, crystallization proceeds also in the absence of HF, but less favorably.
b. Because Al triisopropylate is used as Al source, a fixed amount of 3 isopropyl alcohol molecules per Al is always present in the gel.
c. The AIPO4-5 phase can be prepared with numerous templates. Good results are also reported using tripropylamine [3-5].
d. Other Al sources as pseudoboehmite [2, 3] and Al hydroxide [6] also give good and large crystals.
e. For microwave heating, full Teflon autoclaves.
f. For microwave oven (heating rate 4 grd/sec), 15 minutes at 1800C.
g If the product remains brown or gray after 4 hours at 6000C, this can be taken as a hint that free diffusion in the one-dimensional pores is blocked (by stacking faults or by non-framework material) thus preventing oxygen from entering and oxidation products from leaving the pores. By going to 900"C, the material can be make "white," but the uptake capacity remains low.
h. Crystals up to 50 um in length in the direction of the hexagonal columns are easily obtained; in optimized synthesis, Crystals up to 500 um are observed. Incorporation of Si [7] or Co [8] gives larger and better crystals. Numerous compositional variants are known.