RHO

High Silica Rho

Si(80), Al(20)

Contributed by Alain Matijasic and Joël Patarin

Verified by S. Schwarz, by T. Cholley, and by G. Gbery and K. Balkus

Type Material Na6.8Cs3.0[Al98Si38.2O96] : (18-C-6) . wH2O (w ≈29)

Method T. Chatelain, J. Patarin, E. Fousson, M. Soulard, J. L Guth, P. Schulz [1]

Batch Composition 1.8Na2O : 0.3Cs2O : Al2O3 : l0SiO2 : 0.5(18-C-6) : 100H2O

Source Materials

distilled water
18-C-6 (Lancaster,> 98% cycl. (C2H40)6)
cesium hydroxide (Aldrich, 50% CsOH in water)
sodium hydroxide (SDS,> 98% NaOH)
sodium aluminate (Carlo Erba, 56% Al2O3, 37% Na2O, 7% H2O)
silica sol (Dupont Ludox AS-40, 40% SiO2)

Batch Preparation (for ~6 g product)a

(1) [7.84 g water + 1.35 g 18-C-6 + 1.80 g cesium hydroxide solution + 0.59 g sodium hydroxide], stir until dissolved b
(2) [(1) + 1.82 g sodium aluminate], stir until homogenized
(3) [(2) + 15.00 g silica sol], stir until homogenized (formation of a gel) Continue stirring with magnetic stirrer for 24 h., then transfer to a PTFE-lined stainless-steel autoclave. Gel pH = 14

Crystallization

Vessel: 120 mL PTFE-lined stainless steel autoclave
Time: 192 hours
Temperature: 110¼C in a preheated oven
Agitation: none. Final pH approximately 12

Product Recovery

(1) Dilute the reaction mixture with distilled water
(2) Filter and wash until pH 10
(3) Dry at 600C overnight
(4) Yield: 6 g as-synthesized RHO-type sample (product containing about one molecule 1 8-C-6 as organic template per unit cell)b

Product Characterization

XRD: Strong RHO pattern showing cubic symmetry. (ao=15.031( 1)Å);c no visible impurities
Elemental Analyses: Si/Al is close to 3.9 b
Crystal size and habit: The crystals display a sphere-like shape with an average size of 1 um
Click here to view XRD pattern

Reference

[1] T. Chatelain, J. Patarin, E. Fousson, M. Soulard, J. L Guth, P. Schulz, Micropor. Mat. 4 (1995) 231

Notes

a. This recipe has been successfully scaled up by a factor of six.

b. The starting mixture is prepared in a polyethylene vessel.

c. According to Ref. [1].