Contributed by David Vaughan and Karl Strohmaier

Verified by S. Yang and A. Navrotsky, by C. Williams and C. Round, by Hyun-ku Rhee, and by J. Kornatowski

Type Material Na_7.3(TMA⁺)_0.7A1₈Si₂₈O₇₂ : wH₂O (TMA = tetramethylammonium)

Method D. E. W. Vaughan [1]

Batch Composition 3.35 Na₂O : 1.24 (TMA)Br : Al₂O₃ : 9.17 SiO₂ : 125 H₂O : 0.66 Na₂SO₄

Source Materials

deionized water
sodium hydroxide (J. T. Baker, ~ 99% NaOH)
alumina (Alcoa C-31, assumed 100% Al₂O₃. 3 H₂O)
sodium silicate (PQ Corp. N brand, 8.9% Na₂O, 28.7% SiO₂)
tetramethylammonium bromide (RSA)
aluminum sulfate (J. T. Baker, Al₂(SO₄)₃ : 17 H₂O)

Batch Preparation (for 112 g dry product)

Preparation of Seed Solution (2)

(1) [30 g water + 16 g NaOH + 3.25 g alumina] reflux until a clear solution forms, then cool to room temperature and add water back to the original weight if necessary
(2) [54.4 g sodium silicate + 31.3 g water + (1)], add sodium aluminate solution slowly with mixing in a 200 mL Waring blender
(3) Age for 24 hours at room temperature ^a

Preparation of Crystallization Batch

(4) [50 g water + 19.6 g NaOH + 25.1 g alumina], reflux until clear. Cool to room temperature and add water to attain the original weight
(5) [50 g water + 40 g tetramethylammonium bromide], mix until dissolved.
(6) [396.4 g sodium silicate + 35 g water + 13.9 g (3) + (5)]. Add components sequentially with mixing in a Pyrex one-L reaction kettle with mixing. Heat mixture to 80¡C
(7) [50 g water + 30 g aluminum sulfate], mix until dissolved
(8) [(6) + (4) + (7)], add sodium alumina to solution followed by alum solution with stirring at 80¡C ^b
(9) Increase temperature to 100¡C and stir until homogeneous

Crystallization

Vessel: one-L Pyrex reaction kettle with reflux condenser and stirrer^c
Time: 40+ hours ^d
Temperature: 100¡C
Agitation: None, except just prior to sampling

Product Recovery

(1) Vacuum filter on a Buchner funnel
(2) Wash to pH < 10
(3) Dry at 110¡C
(4) Yield near quantitative on Al₂O₃

Product Characterization

XRD excellent MAZ
Elemental analysis: 0.92 Na₂O : 0.1 (TMA)₂O : Al₂O₃ : 7.14 SiO₂
Crystal size and habit: barrel-shaped aggregates of needle-like crystals (2 to 3 um long and 0.1 um dia.) ^e
Click here to view XRD pattern

References

[1] D. E. W. Vaughan, Mater. Res. Soc. Symp. Proc. 111 (1988) 89
[2] D. E. W. vaughan, US Patent 4 178 352 (1979)

Notes

a. Stored at room temperature, this seed solution will be stable and usable for several months.

b. This formulation produces a hard gel when the alum is added making it difficult to fully homogenize. A Hobart or Kitchenaid mixer is better than a blender if available. The gel breaks up at about 80¼C.

c. Alternatively, a one-L Teflon jar (Nalgene) or subdividing the gel between smaller vessels is appropriate.

d. After about 18 hours, faujasite is fully crystallized (Si/Al = 2.4). Continuing the crystallization for more than 40 hours produces fully crystalline MAZ. It was still pure MAZ after 7 days.

e. ¹³C NMR shows one site in the GME cage.