|
CHA |
Chabazite |
Si(68), Al(32) |
Contributed by Thomas R Gaffney
Verified by J. Warzywoda, by J. Cejka, and by Liu Xinjin
Type Material K11[Al11Si25O72]:40 H2O
Method M. Bourgogne, J.-L Guth, R Wey [1]
Batch Composition 0.17 Na2O : 2.0 K2O : Al2O3 : 5.18 SiO2 : 224 H2O
Source Materials
demineralized water
potassium hydroxide (J. T. Baker reagent grade, 45% KOH solution)
(Na,H) Zeolite Y (UOP LZY-64)a
Batch Preparation (for 25 g dry product)
(1) [198.2 mL water + 26.8 mL KOH (45% solution), mix
(2) [(1) + 25.0 g Zeolite Y], seal in a polypropylene bottle and shake for 30 s
Crystallization
Vessel: polypropylene bottle with a screw-top lid
Temperature: 95¡C (steam chamber)
Tune: 96 hours
Agitation: none
Product Recovery
(1) Remove bottle from the steam chamber and filter to recover solids while still hot b
(2) Wash two times with 500 mL water per wash
(3) Dry at ambient temperature c
(4) Yield: 99% based on alumina, 83% based on silica
Product Characterization
XRD: CHA with no reflections from FAU. Competing phases; FAU when insufficient crystallization times are used d
Elemental Analysis: 0.02 Na2O : 0.98 K2O : Al2O3 : 4.32 SiO2 (dry basis)e,f
Crystal Size and Habit: Sub-micron crystallites, 0.1 um on average, multifaceted (some can be seen to be hexagonal platelets)
Click here to view XRD pattern
Reference
[1] M. Bourgogne, J.-L Guth, R. Wey, US Patent 4 503 024 (1985)
Notes
a. The Na/Al ratio of the NaHY starting materials should be less than 0.17. LZY-64 was prepared by heating NH4+ exchanged type Y to 550¡C (at 2¡C/minute) and calcining at 550¡C for 2 hours. Caution: ammonia is liberated during the calcination. Use adequate ventilation and safety precautions.
b. pH = 13.5 after crystallization treatment.
c. The product is stable to drying in an oven at 110¡C.
d. Converting samples of Zeolite Y which contain large crystals or are formed (pelleted, beaded) to chabazite requires longer reaction times.
e. The framework SiO2/Al2O3 is 4.32 by 29Si NMR.
f. For preparing more siliceous product, Nalco 2326 silica (14.5% SiO2) was used as the silica source. Synthetic chabazite with SiO2/Al2O3 = 5.3 forms from a reaction mixture of composition: 0.17 Na2O : 4.31 K2O : Al2O3 : 8 SiO2 : 500 H2O. Addition of more silica to the reaction mixture (batch SiO2 : Al2O3> 8) leads to incomplete conversion of Zeolite Y, and the product is a mixture of CHA and FAU.