Factors governing the synthesis of zeolites from silicoaluminate hydrogels : a comparative study of the crystallization mechanisms of zeolites Y, mordenite and ZSM-5

Bodart, P.; Nagy, J.B.; Gabélica, Z.; Derouane, Éric G.

doi:10.1051/jcp/1986830777

Cited by 59 publications

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spectra of the initial gel and the gel samples heated for \3.3 h exhibit a broad signal centered at around 59 ppm. This indicates the absence of Al(OSi) 2 (OH) 2 species in the samples, which gives a signal at around 70 ppm [52]. This peak can be attributed to Al(OSi) 3 4 species with the high local Al ordering beyond the second coordination sphere in the crystalline zeolite framework.…”

Section: Resultsmentioning

confidence: 94%

An investigation into the crystallization of low-silica X zeolite

Zhang

Huang

2015

J Porous Mater

View full text Add to dashboard Cite

The crystallization of low-silica X (LSX) zeolite with FAU topology was examined under hydrothermal synthesis conditions. PXRD was employed to follow the evolution of the long-range ordering of the gel. Raman spectra provided information on various ring and cage species existing in the gel. 27 Al and 29 Si solid-state NMR spectroscopy was utilized to monitor the change in local environment of tetrahedral sites. The results indicate that an amorphous aluminosilicate phase was formed immediately upon mixing different reactive species. Hydrothermal treatment led to the formation of sodalite-cage like species and the species with larger cavities, joint four-member rings (4Rs) and branched 4Rs, which are the structural building units of the FAU framework. These units were assembled into the crystalline structure of LSX zeolite. 23 Na and 39 K solid-state NMR results show that the transformation process was accompanied by the changes of the local structure of hydrated Na ? and K ? ions. The two types of cations may work synergistically to template the crystallization of LSX zeolite.

show abstract

Section: Resultsmentioning

confidence: 94%

An investigation into the crystallization of low-silica X zeolite

Zhang

Huang

2015

J Porous Mater

View full text Add to dashboard Cite

show abstract

“…Under these conditions, a direct recrystallization process is postulated involving mainly a solid hydrogel transformation, as suggested by the absence of low molecular weight species in the analysis of the solution by liquid 29 Si NMR. Studies of the syntheses of zeolites Y and mordenite 9 further confirmed such a mechanism. Indeed, a rapid crystal growth yields a large number of small crystallites with a homogeneous Al radial distribution.…”

Section: Zeolite Crystallization From Solid-containing Gelsmentioning

confidence: 80%

Heterogenous events in the crystallization of zeolites

2001

View full text Add to dashboard Cite

This work summarizes and reviews the latest advances in the understanding of the mechanism of zeolite crystallization, with special emphasis on those systems involving heterogeneous transformations. Crystallization starting from both clear solutions and solid containing gels is considered, while systems with different compositions are also discussed. The use of in situ techniques in recent years for studying the progress of zeolite crystallization has provided new and essential information showing that in many cases the mechanism follows a nonconventional pathway based on heterogeneous phenomena.The cover picture illustrates a possible mechanism for zeolite crystallization involving different heterogeneous events: formation of pseudocrystalline nanounits, followed by aggregation, densification and zeolitization of those nanoparticles.

show abstract

“…Understanding the crystallization mechanisms of zeolites can conduct to exploit efficient routes to synthesize them. Although numerous works have attempted to understand the mechanisms of zeolites and solution transport and solid phase transformation mechanisms are proposed [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], relatively few studies have been performed on the elucidation of the mediumrange structures and their changes during zeolite crystallization. As it is reported in the previous study, the short-range order is represented by the local coordination polyhedra, while the medium-range structure can be regarded as the next highest level of structural organization beyond the short-range order [19].…”

Section: Introductionmentioning

confidence: 99%