distilled water
sodium hydroxide (50% solution)
sodium aluminate (~ 46% Al₂O₃, 31% Na₂O; Fisher, MC&B, Nalco)
tetramethylammonium hydroxide (TMA-OH, Southwestern Analytical Chemical, 25% aqueous solution)
silica sol (Dupont HS-40 or AS-40, 40% SiO₂)

(1) [290 g water + 6.0 g sodium hydroxide solution + 21.5 g sodium aluminate], stir until dissolved
(2) [292 g TMA-OH (25% solution) + 57.0 g silica sol], stir for approximately 30 minutes
(3) [(1) + (2)], stirvigorously; gel pH = 14.0 to 14.5

Vessel: Teflon bottle, 1000 mL
Incubation: 24 hours at 25⁰C (optional)
Temperature: 100⁰C (oven with efficient air circulation)
Time: 16-48 hours
Agitation: none

Product Recovery ^a

(1) Filter and wash with 0.5 to 1 L water
(2) Dry at 100° C
(3) Yield: approximately 34 g (100% on Al₂O₃)

XRD LTA, a₀ = 24.38 Å; competing phases: GIS (long reaction time) and EAB ^b
Elemental Analysis (dried at 100⁰C): 15.7% Al (29.7% Al₂O₃), 23.1% Si (49.4% SiO₂), 12.4% Na (16.7% Na₂O), 2.24% C (3.83% (TMA)₂O) ^c
Crystal Size and Habit: cubes (some with penetration twinning) approximately 1.0-1.5 um on an edge
Click here to view XRD pattern

[1] G. T. Kerr, lnorg. Chem. 5 (1966) 1537
[2] R. H. Jarman, M. T. Melchior, D. E. W. Vaughan, ACS Symposium Series 218, American Chemical Soc., Washington, D. C., 1983, p 267

a. Although no decomposition of TMA-OH is expected, it is advisable to carry out the crystallization and product work-up in a fume hood. Temperature excursions can produce noxious and toxic by-products, e.g., trimethylamine and methanol.

b. EAB can co-precipitate with ZK-4 if the TMA-OH is added to solution (1) before the silica sol.

c. The Si/Al of products by this recipe ranged from 1.39 to 1.43 (average 1.41). Higher and lower Si/Al products have been made using other recipes. [2]