LTA

ZK-4

Si(59), Al(41)

Contributed by Don Hopkins

Verified by V. Valtchev, by M. Castagnola, and by G. Kuhl

Type Material Na9.2(TMA)0.8[Al10Si14O48] (TMA = tetramethylammonium)

Method G. T. Kerr [1]

Batch Composition 1.55 Na2O :Al2O3 : 3.91 SiO2 : 4.13(TMA)2O : 320 H2O

Source Materials

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)

Batch Preparation (for 34 g product)

(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

Crystallization

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)

Product Characterization

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

References

[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

Notes

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]