INFLUENCE OF THE SIO2 AL2O3 RATIO ON THE SYNTHESIS AND PHYSICOCHEMICAL CHARACTERISTICS OF LEVYNE-TYPE ZEOLITE/

Levyne-type zeolites were synthesized from gels of initial composition s 4.5Na(2)O-6MeQI-xAl(2)O(3) 30SiO(2)-500H(2)O, with MeQ = methylquinu clidinium and 0.6 less than or equal to x greater than or equal to 3 a t 150 less than or equal to t greater than or equal to 190 degrees C. The Si-29 NMR spectra show the presence of two crystallographically di fferent sites in the structure. The Al-27 NMR spectra also suggest the presence of two different tetrahedral Al atoms incorporated in the st ructure. A rather high amount of defect groups SiOM and Si(OM), with M = MeQ, Na and/or H are present in the precursor samples. The Si(OM)(2 ) groups are eliminated during calcination, and a certain amount of Si OM still persists after calcination. The combined C-13 NMR and thermal analysis data allowed one to interpret the nature of the two differen t types of MeQ(+) ions occluded in the levyne channels. (C) 1998 Elsev ier Science B.V.