Cs. Gittleman et al., THE ROLE OF ALKALI CATIONS IN ZEOLITE SYNTHESIS FROM SILICATE SOLUTIONS CONTAINING N,N,N-TRIMETHYL-1-ADAMANTAMMONIUM CATIONS, Catalysis letters, 38(1-2), 1996, pp. 1-9
Zeolite synthesis from aqueous N,N,N-trimethyl-1-adamantammonium (TMAA
(+))-alkali (Na+, K+, Rb+, and Cs+) silicate mixtures is studied using
X-ray diffraction, elemental analysis, scanning electron microscopy,
and Si-29 magic angle spinning (MAS), H-1-C-13 cross-polarization (CP)
MAS and H-1-Si-29 CP MAS NMR spectroscopies. SSZ-24 forms in the pres
ence of potassium cations, and SSZ-31 crystallizes in the presence of
sodium cations. This is the first report of SSZ-31 synthesis from Na-T
MAA silicate mixtures. Unknown silicates form in the presence of rubid
ium and cesium cations, whereas no crystalline material is observed in
synthesis mixtures devoid of alkali cations. The alkali cations do no
t appear to serve as templates or void fillers during zeolite crystall
ization, nor do they stabilize soluble silicate anions which serve as
building blocks during zeolite crystallization. Rather, the alkali cat
ions appear to regulate the transformation of the amorphous synthesis
gel into either crystalline zeolite or other silicate phases.