Influence of the SiO2/Al2O3 ratio on the synthesis and physicochemical characteristics of levyne-type zeolite

✍ Scribed by C.V. Tuoto; A. Regina; J.B. Nagy; A. Nastro

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 839 KB
• Volume: 20
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/s1387-1811(97)00025-5

✦ Synopsis

Levyne-type zeolites were synthesized from gels of initial compositions 4.5Na,O--6MeQIPsA120, 3OSiO,-SOOH,O. with MeQ =methylquinuclidinium and 0.6 5 I 2 3 at 150 5 t 2 190' C. The '"Si NMR spectra show the presence of two crystallographically different sites in the structure. The 27A1 NMR spectra also suggest the presence of two different tetrahedral Al atoms incorporated in the structure. A rather high amount of defect groups SiOM and Si(OM )2 with M = MeQ, Na and/or H are present in the precursor samples. The Si(OM )z groups are eliminated during calcination. and a certain amount of SiOM still persists after calcination. The combined "C NMR and thermal analysis data allowed one to interpret the nature of the two different types of MeQi ions occluded in the ievyne channels. G 1998 Elsevier Science B.V. !&j'l~YW~k: Levynite; Synthesis; ""Si NMR; "Al NMR; 1.3~ NMR * Corresponding author 4-azabicyclo[2,2,2]octane (DABCO) [4]. Using methylquinuclidine ( 1 -methylazabicyclo [2,2,2]octane) similar st ructures were obtained called Nu-3 [S], LZ-132 [6] and LZ-133 [7]. ZSM-45, also of levynite structure, was obtained with the help of 2-hydroxyalkyltrialkylammonium chloride [RI.

Generally, the synthetic samples all have rather high Si,lAl ratios, because of the presence of organic molecules in the zeolitic channels. DiKerent heteroatoms were also introduced in the structure [9, lo]. Levyne was also successfully synthesized in fluoride-containing media [ 1 I]. Several short publications were previously reported on the crystallization field [ 121. on the influence of the SiOJA120, ratios, on the levynite synthesis