Verified by S. Khvoshchev and M. Shubaeva, by J. Warzywoda, by J. Parise, M. Kleinsorge and S. Park, and by Conghua Liu

Type Material Na₂.₉K₅.₄[Al_8.3Si_27.7O₇₂] . wH₂O (w ~7)

Method A. Cichocki, P. Koscielniak [1, 2]

Batch Composition 4.18 Na₂O : 1.25 K₂O : Al₂O₃ : 16.5 SiO₂ : 175 H₂O

distilled water
sodium hydroxide (97% NaOH)
potassium hydroxide (86% KOH)
silica sol (Rudniki Chemical Works, 29.5% SiO₂, 0.2% Na₂O)
sodium aluminate solution (26.6% Al₂O₃ 19.6% Na₂O) = NaAlO₂

Batch Preparation (for 14 g dry product)

(1) [9.57 g water + 4.67 g sodium hydroxide + 3.24 g potassium hydroxide], dissolve and cool to room temperature
(2) [67.0 g silica sol + (1)], mix in a porcelain mortar and stir for 2 minutes ^a
(3) [(2) + 7.64 g sodium aluminate solution], add NaAlO₂ drop by drop to the stirred silicate over a 10 min. interval and continue stirring for 20 minutes

Vessel: stainless steel autoclave, 120 cm³ capacity
Aging: 24 h at room temperature
Temperature: 140¡C
Time: 7 days
Agitation: none

(1) Cool; transfer the reaction mixture to a mortar and grind
(2) Filter and wash in a Buechner funnel until pH of the filtrate is 10
(3) Dry at 110¡C
(4) Equilibrate in laboratory air for a few days
(5) Yield: near 95% on Al₂O₃ and 41.5% on SiO₂ ^b

[1] A. Cichocki, P. Koscielniak, M. Michalik, M. Bus, Zeolites 18 (1997) 25
[2] A. Cichocki, P. Koscielniak, Micropor. Mesopor. Mater. 29 (1999) 369
[3] A. Cichocki, Zeolites 11(1991) 758
[4] R. Aiello, R. M. Barrer, J. Chem. Soc. 1970 (A), 1470

a. The use of a porcelain mortar gives a good mix of the reagents, particularly aluminate and silica sol.

b. 39.9% of the sum of Na₂O, K₂O, Al₂O₃ and SiO₂ masses introduced into the reaction mixture. Synthetic Erionite with SiO₂/Al₂O₃= 6.55 forms from a reaction mixture of composition 8.09 Na₂O : 2.38 K₂O : Al₂O₃ : 27.0 SiO₂ : 448 H₂O when crystallization is carried out in a stainless steel autoclave at the temperature 373 K and time 7 days, but the yield is reduced to 22.5%. This composition differs slightly from that given in ref. [3] where NaOH and KOH were assumed 100%.

c. The Na/K-system synthetic product shows domains of erionite and offretite in a single crystal. The XRD pattern agrees with natural offretite (PDF), but the product shows adsorption properties erionite. Unfaulted erionite crystallized in the Na/Me₄N-system. [41

d. Formation of PHI is favored by decreasing relative alkalinity (OH^-/SiO₂). Decreasing the temperature of crystallization favors CHA. Increasing relative alkalinity leads to formation of LTL