Zeolite crystallization on mullite fibers

Valtchev, Valentin; Mintova, Svetlana; Schoeman, Brian J.; Spasov, L.; Konstantinov, L.

doi:10.1016/s0167-2991(06)81934-8

Cited by 10 publications

(5 citation statements)

References 4 publications

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“…Many studies have therefore been conducted during the past two decades to overcome these drawbacks. − It led to different approaches, like the use of inorganic binders for shaping the final zeolite material, decreasing the size of the zeolite crystals to shorten the diffusion paths, or increasing the zeolite pore size. Unfortunately, those binders cause a loss of activity as they partially block the channels, thus reducing the accessibility to the active sites.…”

Section: Introductionmentioning

confidence: 99%

Design of MFI Zeolite-Based Composites with Hierarchical Pore Structure: A New Generation of Structured Catalysts

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Yun

Pereira

et al. 2009

Crystal Growth & Design

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Zeolite/glass composite materials with hierarchical trimodal pore size distributions have been successfully prepared and subsequently characterized. Starting from glass monoliths having meso-and macropores, additional microporosity was introduced while allowing the growth of zeolite crystals via partial recrystallization of the glass support into ZSM-5 zeolite phase. Structured zeolitic catalytic materials were produced using a combination of supramolecular templating methods to produce the glass support, followed by conventional self-assembly of template cations and silica species. Zeolite crystals are therefore in intimate contact with the glass support, featuring micropores in addition to the mesopores. Hence, these zeolite/glass composites exhibit enhanced diffusional properties in comparison with purely microporous zeolite materials. These enhanced mass transport properties allowed improvement of the selectivity toward light olefins in the important n-hexane cracking reaction.

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Section: Introductionmentioning

confidence: 99%

Design of MFI Zeolite-Based Composites with Hierarchical Pore Structure: A New Generation of Structured Catalysts

Ocampo

Yun

Pereira

et al. 2009

Crystal Growth & Design

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“…The use of structured reactors in catalysis has become a major field in catalysis during the past decade . In combination with studies devoted to find new active phase formulations, numerous research has also been focused on the development of structured composites (catalyst + support) to improve the reactor hydrodynamics and, hence, the catalytic performance for several reactions. − Thus, structured zeolitic catalysts were prepared via a binderless hydrothermal synthesis on metals 11,20-22 or ceramics. − In spite of a reduced pressure drop, and improved heat and mass tranfers when compared to extrudated pellets or powdered microgranules, the industrial applications of these structured materials remain limited. This is either due to the lack of support inertness or to a nonsufficient mechanical and chemical stability.…”

Section: Introductionmentioning

confidence: 99%

“…[17][18][19] Thus, structured zeolitic catalysts were prepared via a binderless hydrothermal synthesis on metals 11, [20][21][22] or ceramics. [23][24][25][26][27][28] In spite of a reduced pressure drop, and improved (1) Corma A. Chem. ReV.…”

Section: Introductionmentioning

confidence: 99%

Autoassembly of Nanofibrous Zeolite Crystals via Silicon Carbide Substrate Self-Transformation

et al. 2007

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ZSM-5 zeolite nanofibers with a size of 90 nm and lengths up to several micrometers were prepared via in-situ silicon carbide support self-transformation. The morphology and aggregation degree of these zeolite nanofibers could be modified by adjusting the pH conditions, the nature of the mineralizer (OH- or F-), or the synthesis duration. The novelty consists of the preparation of zeolite nanowires without the use of any organogelating agent, along with controlled macroscopic shapes (extrudates, foam monolith) for direct use as a structured reactor. Finally, these materials are catalytically active in the conversion of methanol to gasoline range hydrocarbons (MTG process) and hence exhibit the typical solid acidity of zeolitic materials.

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“…Structured zeolitic packings can be prepared via a binderless hydrothermal synthesis on metal grids − or ceramics. − Even well-covered, metallic substrates are known to catalyze many reactions, and thus contribute to deep oxidation pathways. Another drawback of metallic supports for zeolite deposition is connected to the big difference in the dilatation coefficients of metals compared to silicates, which may cause a zeolite attrition due to its detachment under temperature changes during reactor operation .…”

Section: Introductionmentioning

confidence: 99%

ZSM-5 Coatings on β-SiC Monoliths: Possible New Structured Catalyst for the Methanol-to-Olefins Process

et al. 2007

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Structured zeolite/silicon carbide composites were succesfully synthesized by ZSM-5 coatings deposited on macroscopic β-SiC foams with medium surface area. A homogeneous coverage of the support (30 wt % zeolite) by ZSM-5 crystals, having 1 µm average size, was reached after a double-coating procedure. The ZSM-5/β-SiC composite materials were characterized by BET, XRD, SEM, and H/D exchange methods. 27 Al MAS NMR analysis revealed that all aluminum was present in a tetrahedral coordination, thus sitting in the zeolite framework. The existence of a nanoscopic layer of silica and silicon oxycarbide on the surface of the support ensures the strong anchoring of the zeolite crystals on the β-SiC substrate. The lack of secondary chemical reaction between the synthesis solution and the support allows a precise control of the Si/Al ratio in the final zeolite. The use of ZSM-5 coated β-SiC foam packings in the methanol-to-olefins reaction presents substantial activity/selectivity improvements compared to conventional zeolite packings. Moreover, the structured composites exhibit a higher stability toward deactivation by coking, compared to the powdered form of the zeolite.

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Zeolite crystallization on mullite fibers

Cited by 10 publications

References 4 publications

Design of MFI Zeolite-Based Composites with Hierarchical Pore Structure: A New Generation of Structured Catalysts

Design of MFI Zeolite-Based Composites with Hierarchical Pore Structure: A New Generation of Structured Catalysts

Autoassembly of Nanofibrous Zeolite Crystals via Silicon Carbide Substrate Self-Transformation

ZSM-5 Coatings on β-SiC Monoliths: Possible New Structured Catalyst for the Methanol-to-Olefins Process

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