Journal ArticleDOI
Mechanisms of Structure Direction in the Synthesis of Pure-Silica Zeolites. 1. Synthesis of TPA/Si-ZSM-5
Sandra L. Burkett,Mark E. Davis +1 more
TLDR
The role of tetrapropylammonium (TPA) as a structure-directing agent in the sodium-free synthesis of pure-silica ZSM-5 was investigated by solid-state Si CP MAS NMR as discussed by the authors.Abstract:
The role of tetrapropylammonium (TPA) as a structure-directing agent in the sodium-free synthesis of pure-silica ZSM-5 (Si-ZSM-5) is investigated by solid-state ^1H-^(29)Si CP MAS NMR. It has previously been proposed that the mechanism of structure direction in a sodium-containing system involves preorganization of silicate species around the TPA ions with subsequent assembly of these inorganic-organic composite structures to yield crystalline Si-ZSM-5 with occluded TPA molecules.l ^1H-^(29)Si CP MAS NMR results indicate that short-range intermolecular interactions, i.e., on the order of van der Waals contact distances, are established during heating of the zeolite synthesis gel prior to the development of long-range order indicative of the ZSM-5 structure. These interactions are independent of the presence of sodium in the gel or the silica source used. An attempt to isolate the composite species by trimethylsilylation of the synthesis mixture was partially successful. These results provide additional evidence for the existence of preorganized, inorganic-organic composite structures during the synthesis of Si-ZSM-5. A modified mechanism of structure direction and crystal growth of Si-ZSM-5 is proposed.read more
Citations
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Journal ArticleDOI
The Hydrothermal Synthesis of Zeolites: History and Development from the Earliest Days to the Present Time
Colin S. Cundy,Paul A. Cox +1 more
Journal ArticleDOI
The hydrothermal synthesis of zeolites: precursors, intermediates and reaction mechanism
Colin S. Cundy,Paul A. Cox +1 more
TL;DR: An account of the mechanistic aspects of hydrothermal zeolite synthesis can be found in this paper, where a review of the most probable mechanistic pathways in Zeolite formation is given.
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Semiconducting superlattices templated by molecular assemblies
TL;DR: In this article, the growth of stable semiconductor-organic superlattices based on cadmium sulphide and Cadmium selenide is described, which can be tailored, through the electronic properties of the organic amphiphiles, for photosynthetic and photocatalytic applications.
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Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis
TL;DR: The siting and distribution of framework Al atoms dramatically affect catalytic activity/selectivity both of protonic and transition metal ion-containing zeolite catalysts.
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In Situ Imaging of Silicalite-1 Surface Growth Reveals the Mechanism of Crystallization
TL;DR: It is confirmed that silicalite-1 growth occurs via the addition of both silica molecules and precursors, bridging classical and nonclassical mechanisms.
Related Papers (5)
Mechanism of Structure Direction in the Synthesis of Si-ZSM-5: An Investigation by Intermolecular 1H-29Si CP MAS NMR
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