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Formation of and silicon incorporation in SAPO-5 synthesized via dry-gel conversion
- Source :
- Microporous and Mesoporous Materials. 182:40-49
- Publication Year :
- 2013
- Publisher :
- Elsevier BV, 2013.
-
Abstract
- Molecular sieves have been scientifically and industrially important materials since their discovery. These porous, crystalline networks of tetrahedrally coordinated atoms bridged by oxygen are known as excellent catalysts. The framework of the aluminophosphate family of molecular sieves is itself non-catalytic, but through heteroatomic substitution these materials can diversify into, for example, the silicoaluminophosphate (SAPO) family of heterogeneous acid catalysts. Research into the methods by which these substitutions occur, as discoveries can lead to refined control over material property and function. SAPO-5 was chosen as model system of study. 27 Al, 29 Si and 31 P solid state NMR and PXRD were used as the primary methods of investigation. The SAPO-5 study determined that the dry gel conversion (DGC) methods of steam assisted conversion (SAC) and vapor phase transport (VPT) follow similar reaction pathways. After an initial difference caused by the lack of organic structure directing agent in the gel for the VPT method, crystallization is similar between methods, and silicon incorporation results in two populations of silicon sites. One represents isolated Si(OAl) 4 species well incorporated into the framework, while the other represents silica islands within the framework. The initial core of the nuclei is AlPO 4 in nature and the Si is gradually incorporated into the lattice as the crystals grow. The vapor phase silicon uptake (VPSU) method provides a contrast to this data, inducing nucleation that occurs concurrently with Si incorporation and producing only isolated Si(OAl) 4 species.
- Subjects :
- Silicon
Nucleation
chemistry.chemical_element
General Chemistry
Condensed Matter Physics
Molecular sieve
law.invention
Catalysis
Solid-state nuclear magnetic resonance
chemistry
Chemical engineering
Mechanics of Materials
law
Organic chemistry
General Materials Science
Crystallization
Porosity
Powder diffraction
Subjects
Details
- ISSN :
- 13871811
- Volume :
- 182
- Database :
- OpenAIRE
- Journal :
- Microporous and Mesoporous Materials
- Accession number :
- edsair.doi...........426e5d13d98c1574c6013d38315228a1