OFF

[Ga] Offretite

Si(65), Ga(35)

Contributed by Mario Occelli

Verified by F. Machado and by S. Iwamoto

Type Material K2.2Na0.1(TMA)4.lGa6.4Si11.6O36 : wH2O (TMA = tetramethylaminoiiium)

Method M. L Occelli [1]

Batch Composition 2.25 K2O : 1.61 Na2O : 0.5 (TMA)2O : Ga2O3 : 11.7 SiO2 : 250 H2O : 1.0 HCl

Source Materials

deionized water
sodium hydroxide, reagent grade (~97% NaOH)
potassium hydroxide, reagent grade (~87% KOH)
gallium oxide (99.99%)
silica sol (Dupont HS-40, 39% SiO2, 0.5% Na2O)
tetramethylammonium chloride [99+% (TMA)Cl]

Batch Preparation

(1) [50 g water + 12.0 g sodium hydroxide + 29.0 g potassium hydroxide], mix until dissolved; heat to boiling
(2) [(1) + 18.7 g gallium oxide], stir at boiling point until a clear solution is obtained
(3) [(2) + 30 g water], mix and cool to ambient temperature a
(4) [20 g water + 11.0 g (TMA)Cl], mix until dissolved
(5) [(3) + (4)], mix thoroughly
(6) [180.3 g silica sol + 234.8 g water], mix for 4 hours
(7) [(6) + (5)], add gallate mixture dropwise to the vigorously-stirred diluted silica sol. Continue stirring in a round-bottomed flask for 10 hours

Crystallization

Vessel: 1000 mL round bottomed flask with agitator and reflux condenser
Incubation: 10 h at ambient temperature with stirring
Temperature: 980C b
Time: 3 days c
Agitation: Continue stirring until temperature reaches 98¡C, then discontinue stirring for
balance of crystallization period

Product Recovery

(1) Filter and wash with deionized water until pH < 10
(2) Dry at 1100C
(3) Yield: near 100% on Ga2O3

Product Characterization

XRD: OFF, no other crystalline products or amorphous material detected Elemental Analyses: 49.5% SiO2, 42.2% Ga2O3, 7.2% K2O, 1.1% Na2O d
Click here to view XRD pattern

References

[1] M. L Occelli, US Patent 5 133 951 (1992)
[2] M. L Occelli, H. Eckert, C. Hudalla, A. Auroux, P. Ritz, P. S. Iyer, Micropor. Mater. 10 (1997) 123-135
[3] M. L Occelli H. Eckert, C. Hudalla, A. Auroux, P. Ritz, P. S. Iyer, in Proceedings of the 11th International Zeolite Conference, Seoul, Korea, Hakze Chon, Son-Ki Ihm (eds.), Elsevier, Amsterdam, 1997, p 1981
[4] M. L Occelli, H. Eckert, P. S. Iyer, P. Ritz, in Synthesis of Porous Materials, M. L Occelli, H. Kessler (eds.), Marcel-Dekker (1997), p. 283

Notes

a. Diluted Na,K gallate solution must be clear.
b. Stirring is continued as temperature is increased to 980C, then discontinued for the remainder of the crystallization treatment.
c. Methods to reduce crystallization time are given in ref. [1].
d. After calcination in nitrogen for 2 hours at 5000C followed by calcination in air for 10 hours at 5500C; the BET surface area was 404 m2/g. Characterizations of similar gallium offretites are given in references [2-4].