Contributed by Karl Strohmaier

Verified by P. Piccione and by Huann-Jih Lo

Type Material K₁₁Al₁₁Si₂₁O₆₄ ^. 20H₂O

Method R M. Milton [1]

Batch Composition 3 K₂O : 0.05 Na₂O : Al₂O₃ : 5 SiO₂ : 100 H₂O

Source Materials

deionized water
potassium hydroxide (J. T. Baker, 87.6% KOH)
alumina (Alcoa C-31, 65% Al₂O₃)
colloidal silica (duPont Ludox HS-40, 40% SiO₂) ^a

Batch Preparation (for 15 g dry product)

(1) [20 g water + 12.4 g potassium hydroxide + 5.0 g alumina], heat to a gentle boil with stirring until clear. Cool to room temperature and add water to attain the original weight
(2) [24.2 g colloidal silica + 18.5 g water + (1)]. Add components sequentially with mixing in a beaker ^b

Crystallization

Vessel: 125 Teflon-lined autoclave (Parr #4748 acid digestion bomb)
Time: 48 hours
Temperature: 150⁰C ^c
Agitation: None

Product Recovery

(1) Vacuum filter on a Buechner funnel
(2) Wash to pH < 10
(3) Dry at 110⁰C
(4) Yield 15 g, near quantitative on Al₂O₃

Characterization

XRD excellent MER, unit cell dimensions (space group I4/mmm - No. 139) a = 14.15 Å, c = 10.03 Å
Elemental Analyses: K₂O : Al₂O₃ : 3.66 SiO₂
Crystal size and Habit: barbell-shaped aggregates (40-50 um long and 20-30 um dia.) of needle-like crystals.
Click here to view XRD pattern

Reference

[1] R M. Milton, US Patent 3 012 853 (1961)

Notes

a. Available from Aldrich or Alpha.

b. Solution gels in about 5 minutes.

c. If mixture is crystallized at 100⁰C, a mixture of chabazite and Linde W is made.