Highly Oriented Growth of Catalytically Active Zeolite ZSM‐5 Films with a Broad Range of Si/Al Ratios

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Abstract

Highly b‐oriented zeolite ZSM‐5 films are critical for applications in catalysis and separations and may serve as models to study diffusion and catalytic properties in single zeolite channels. However, the introduction of catalytically active Al ³⁺ usually disrupts the orientation of zeolite films. Herein, using structure‐directing agents with hydroxy groups, we demonstrate a new method to prepare highly b‐oriented zeolite ZSM‐5 films with a broad range of Si/Al ratios (Si/Al=45 to ∞). Fluorescence micro‐(spectro)scopy was used to monitor misoriented microstructures, which are invisible to X‐ray diffraction, and show Al ³⁺ framework incorporation and illustrate the differences between misoriented and b‐oriented films. The methanol‐to‐hydrocarbons process was studied by operando UV/Vis diffuse reflectance micro‐spectroscopy with on‐line mass spectrometry, showing that the b‐oriented zeolite ZSM‐5 films are active and stable under realistic process conditions.

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Dispersible exfoliated zeolite nanosheets and their application as a selective membrane.

Kumar Varoon, Xueyi Zhang, Bahman Elyassi … (2011)

Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.

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Coke formation during the methanol-to-olefin conversion: in situ microspectroscopy on individual H-ZSM-5 crystals with different Brønsted acidity.

Jan Kornatowski, Davide Mores, Unni Olsbye … (2011)

Coke formation during the methanol-to-olefin (MTO) conversion has been studied at the single-particle level with in situ UV/Vis and confocal fluorescence microscopy. For this purpose, large H-ZSM-5 crystals differing in their Si/Al molar ratio have been investigated. During MTO, performed at 623 and 773 K, three major UV/Vis bands assigned to different carbonaceous deposits and their precursors are observed. The absorption at 420 nm, assigned to methyl-substituted aromatic compounds, initiates the buildup of the optically active coke species. With time-on-stream, these carbonaceous compounds expand in size, resulting in the gradual development of a second absorption band at around 500 nm. An additional broad absorption band in the 600 nm region indicates the enhanced formation of extended carbonaceous compounds that form as the reaction temperature is raised. Overall, the rate of coke formation decreases with decreasing aluminum content. Analysis of the reaction kinetics indicates that an increased Brønsted acid site density facilitates the formation of larger coke species and enhances their formation rate. The use of multiple excitation wavelengths in confocal fluorescence microscopy enables the localization of coke compounds with different molecular dimensions in an individual H-ZSM-5 crystal. It demonstrates that small coke species evenly spread throughout the entire H-ZSM-5 crystal, whereas extended coke deposits primarily form near the crystal edges and surfaces. Polarization-dependent UV/Vis spectroscopy measurements illustrate that extended coke species are predominantly formed in the straight channels of H-ZSM-5. In addition, at higher temperatures, fast deactivation leads to the formation of large aromatic compounds within channel intersections and at the external zeolite surface, where the lack of spatial restrictions allows the formation of graphite-like coke.

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Zeolite thin films: from computer chips to space stations.

Christopher Lew, Rui Cai, Yushan Yan (2010)

Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (3-12 A in diameter). Although natural zeolites were first discovered in 1756, significant commercial development did not begin until the 1950s when synthetic zeolites with high purity and controlled chemical composition became available. Since then, major commercial applications of zeolites have been limited to catalysis, adsorption, and ion exchange, all using zeolites in powder form. Although researchers have widely investigated zeolite thin films within the last 15 years, most of these studies were motivated by the potential application of these materials as separation membranes and membrane reactors. In the last decade, we have recognized and demonstrated that zeolite thin films can have new, diverse, and economically significant applications that others had not previously considered. In this Account, we highlight our work on the development of zeolite thin films as low-dielectric constant (low-k) insulators for future generation computer chips, environmentally benign corrosion-resistant coatings for aerospace alloys, and hydrophilic and microbiocidal coatings for gravity-independent water separation in space stations. Although these three applications might not seem directly related, they all rely on the ability to fine-tune important macroscopic properties of zeolites by changing their ratio of silicon to aluminum. For example, pure-silica zeolites (PSZs, Si/Al = infinity) are hydrophobic, acid stable, and have no ion exchange capacity, while low-silica zeolites (LSZs, Si/Al < 2) are hydrophilic, acid soluble, and have a high ion exchange capacity. These new thin films also take advantage of some unique properties of zeolites that have not been exploited before, such as a higher elastic modulus, hardness, and heat conductivity than those of amorphous porous silicas, and microbiocidal capabilities derived from their ion exchange capacities. Finally, we briefly discuss our more recent work on polycrystalline zeolite thin films as promising biocompatible coatings and environmentally benign wear-resistant and antifouling coatings. When zeolites are incorporated into polymer thin films in the form of nanocrystals, we also show that the resultant composite membranes can significantly improve the performance of reverse osmosis membranes for sea water desalination and proton exchange membrane fuel cells. These diverse applications of zeolites have the potential to initiate new industries while revolutionizing existing ones with a potential economic impact that could extend into the hundreds of billions of dollars. We have licensed several of these inventions to companies with millions of dollars invested in their commercial development. We expect that other related technologies will be licensed in the near future.

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Author and article information

Contributors

Donglong Fu:

ORCID: http://orcid.org/0000-0002-5680-6279

http://www.inorganic‐chemistry‐and‐catalysis.eu

Prof. Dr. Bert M. Weckhuysen:

ORCID: http://orcid.org/0000-0001-5245-1426

b.m.weckhuysen@uu.nl

Journal

Journal ID (nlm-ta): Angew Chem Int Ed Engl

Journal ID (iso-abbrev): Angew. Chem. Int. Ed. Engl

Journal ID (doi): 10.1002/(ISSN)1521-3773

Journal ID (publisher-id): ANIE

Title: Angewandte Chemie (International Ed. in English)

Publisher: John Wiley and Sons Inc. (Hoboken )

ISSN (Print): 1433-7851

ISSN (Electronic): 1521-3773

Publication date (Electronic): 04 July 2017

Publication date (Print): 04 September 2017

Volume: 56

Issue: 37 , Jubilee Issue 150 Years of the GDCh ( doiID: 10.1002/anie.v56.37 )

Pages: 11217-11221

Affiliations

[ ¹ ] Inorganic Chemistry and Catalysis group Debye Institute for Nanomaterials Science Faculty of Science Utrecht University Universiteitsweg 99 3584 CG Utrecht The Netherlands

Author information

Donglong Fu http://orcid.org/0000-0002-5680-6279

Dr. Joel E. Schmidt http://orcid.org/0000-0002-0039-2863

Dr. Zoran Ristanović http://orcid.org/0000-0001-9038-7066

Dr. Abhishek Dutta Chowdhury http://orcid.org/0000-0002-4121-7375

Dr. Florian Meirer http://orcid.org/0000-0001-5581-5790

Prof. Dr. Bert M. Weckhuysen http://orcid.org/0000-0001-5245-1426

Article

Publisher ID: ANIE201704846

DOI: 10.1002/anie.201704846

PMC ID: 5599938

PubMed ID: 28675590

SO-VID: a3cfd7c5-e20c-4b96-8e9f-2ea86eb64e74

License:

This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

History

Date received : 11 May 2017

Page count

Figures: 5, Tables: 0, References: 38, Pages: 5, Words: 0

Funding

Funded by: H2020 European Research Council (BE)

Award ID: Advanced Research Grant (No. 321140)

Funded by: H2020 Excellent Science

Award ID: Marie Sklodowska-Curie grant (No. 702149)

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source-schema-version-number 2.0

component-id anie201704846

cover-date September 4, 2017

details-of-publishers-convertor Converter:WILEY_ML3GV2_TO_NLMPMC version:5.1.9 mode:remove_FC converted:15.09.2017

ScienceOpen disciplines: Chemistry

Keywords: fluorescence micro-(spectro)scopy,heterogeneous catalysis,thin films,zeolites,zsm-5

Data availability:

ScienceOpen disciplines: Chemistry

Keywords: fluorescence micro-(spectro)scopy, heterogeneous catalysis, thin films, zeolites, zsm-5

Highly Oriented Growth of Catalytically Active Zeolite ZSM‐5 Films with a Broad Range of Si/Al Ratios

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Photoluminescent Nanomaterials

Most cited references 37

Dispersible exfoliated zeolite nanosheets and their application as a selective membrane.

Coke formation during the methanol-to-olefin conversion: in situ microspectroscopy on individual H-ZSM-5 crystals with different Brønsted acidity.

Zeolite thin films: from computer chips to space stations.

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