|
ABW |
Li-A (BW) |
Si(50), Al(50) |
Contributed by Poul Norby
Verified by J. MacDougall and by D. Vaughan
Type Material Li4[Al4Si4O16] : 4 H2O a
Method P. Norby, A. Norlund Christensen, I. G. Krogh Andersen [1]
Batch Composition NaAlSiO4: 4.3 LiCl: 154 H2O b
Source Materials
distilled water
lithium chloride (LiCl) (Merck, analytical grade)
sodium Zeolite A (Na-LTA) (Union Carbide, NaAlSiO4.25H2O)
Batch Preparation (for 6.9 g product)
(1) [150 mLwater + l0g LiCl], stir until dissolved
(2) [(1) + 10 g Na-LTA], mix until uniform slurry
Crystallization
Vessel: Teflon-lined autoclave c
Time: 72 hours
Temperature: 2500C d
Agitation: none
Product Recovery
(1) Cool to ambient temperature
(2) Filter
(3) Wash until chloride-free
(4) Dry at 1100C
(5) Yield: close to 100%
Product Characterization
XRD: ABW, no other crystalline phases or amorphous material detected e,f
Elemental Analysis: Li1.02Na0.004 AlSiO4:1.1 H2O g,h
Crystal Size and Habit: small elongated flat needles
Click here to view XRD patterns non-calcined and calcined
References
[1] P. Norby, A. Nørlund Christensen, I. G. Krogh Andersen, Acta Chem. Scand. A40 (1986) 500
[2] P. Norby, H. Fjellvåg, Zeolites 12 (1992) 898
[3] R M. Barrer, E. A. D. White, J. Chem. Soc., London (1951) 1267
[4] P. Norby, Zeolites 10 (1990) 193
[5] E. Krogh Andersen, G. Plough Sørensen, Z. Kristallogr. 176 (1986) 67
Notes
a. Of the aluminosilicate ABW type analogues, only the hydrated Li-form and the anhydrous Rb-, Cs-, and Tl-forms may be directly synthesized. [2]
b. Addition of small amounts of potassium fluoride are reported to have a marked mineralizing effect. [3]
c. In a gold-lined steel autoclave, the reaction was performed at 2850C in 72 hours.
d. Good results have been obtained by crystallization at 2000C for 93 hours.
e. At temperatures above 3500C a -eucriptite is formed. Li2SiO3 may occur. [1]
f. Upon dehydration of zeolite Li-A(BW) the framework topology is retained, but the 8-ring channel is considerably narrowed. The lithium cation coordinates across the channel, preventing rehydration of the material even when submerged in water. However, by hydrothermal treatment at temperatures above 1100C, rehydration to the original zeolite is possible.
g. The Si/Al ratios of ABW type are close to 1. Though Li-A(BW) may be synthesized from oxide compositions with Si/Al ratios from 0.5 to 7, there is no evidence of variation in the Si/Al ratio of the product. [3]
h. Reversible dehydration of Li-A(BW) is possible to a limited extent. [4] The anhydrous ABW-types do not show any sorption of water at ambient conditions.
i. In one experiment (sodium bromosodalite and LiBr, hydrothermal 2600C, 72 h), single crystals large enough for single crystal diffraction were obtained (0.1 x 0.05 x 0.01 um) [1,5]