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  Modular Pd/Zeolite Composites Demonstrating the Key Role of Support Hydrophobic/Hydrophilic Character in Methane Catalytic Combustion

Losch, P., Huang, W., Vozniuk, O., Goodman, E. D., Schmidt, W., & Cargnello, M. (2019). Modular Pd/Zeolite Composites Demonstrating the Key Role of Support Hydrophobic/Hydrophilic Character in Methane Catalytic Combustion. ACS Catalysis, 9(6), 4742-4753. doi:10.1021/acscatal.9b00596.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0004-768C-A Version Permalink: http://hdl.handle.net/21.11116/0000-0004-768D-9
Genre: Journal Article

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 Creators:
Losch, Pit1, 2, Author              
Huang, Weixin1, Author
Vozniuk, Olena3, Author              
Goodman, Emmett D.1, Author
Schmidt, Wolfgang2, Author              
Cargnello, Matteo1, Author
Affiliations:
1Department of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis, Stanford University, Stanford, California 94304, United States, ou_persistent22              
2Research Group Schmidt, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445618              
3Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              

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Free keywords: C−H activation; emissions control; colloidal nanoparticles; hierarchical porosity; mesoporous zeolite
 Abstract: Complete catalytic oxidation of methane in the presence of steam at low temperatures (T < 400 °C) is a crucial reaction for emission control, yet it presents profound challenges. The activation of the strong C–H bond of methane at low temperature is difficult, and the water present in any realistic application poisons the active surface and promotes sintering of Pd particles during the reaction. Finding materials that can deliver high reaction rates while being more resistant to the presence of water is imperative for advancing several technological applications of natural gas-based systems. However, methods to fairly compare the activity of Pd catalysts (the most active metal for methane combustion) are needed in order to perform useful structure–property relationship studies. Here, we report a method to study how zeolite hydrophobicity affects the activity of Pd nanoparticles in the reaction, which led to a significant improvement in the water resistance. Mesoporous zeolites were synthesized starting from commercially available microporous zeolites. In this way, a variety of hierarchically porous zeolites, with different hydrophobic/hydrophilic character, were prepared. Preformed colloidal Pd nanoparticles could be deposited within mesostructured zeolites. This approach enabled the systematic study of key parameters such as zeolite framework, Al content, and the Pd loading while maintaining the same Pd particle size and structure for all the samples. Detailed catalytic studies revealed an optimum hydrophobic/hydrophilic character, and a promising steam-resistant catalyst, namely, 3.2 nm Pd particles supported on mesoporous zeolite beta or USY with a Si/Al ratio of 40, emerged from this multiparametric study with a T50 of 355 °C and T90 of 375 °C (where T50 and T90 are temperature values at which the samples reach 50% and 90% methane conversion, respectively) in steam-containing reaction conditions. Finally, we verified that the designed catalysts were stable by in-depth postcatalysis characterization and operando diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) analyses confirming that water adsorbs less strongly on the active PdO surface due to interaction with the zeolite acid sites. This method can be of general use to study how zeolite supports affect the reactivity of supported metals in several catalytic applications.

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Language(s): eng - English
 Dates: 2019-02-082019-04-112019-06-07
 Publication Status: Published online
 Pages: 12
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1021/acscatal.9b00596
 Degree: -

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Title: ACS Catalysis
  Abbreviation : ACS Catal.
Source Genre: Journal
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Publ. Info: Washington, DC : ACS
Pages: - Volume / Issue: 9 (6) Sequence Number: - Start / End Page: 4742 - 4753 Identifier: ISSN: 2155-5435
CoNE: https://pure.mpg.de/cone/journals/resource/2155-5435