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H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
53543 46974 2016 10 PDF Available
Title
H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts
Abstract

•The H2/D2 isotopic exchange is very fast at 0 °C over clean Ru surfaces.•If chemisorbed H species are still present, the rate of exchange is slowed down and H2/D2 mixtures cannot reach equilibrium.•Reverse H spillover from the active carbon to the metal can be observed during exchange.•The presence of Na inhibits this spillover phenomenon. H2/D2 exchange is a pure homolytic process on Ru-Na/AC catalysts.

Hydrogen interaction with ruthenium surfaces is a complex phenomenon that can play an important role in catalytic reactions such as ammonia synthesis. In this study, H2/D2 isotopic homomolecular exchange has been used to characterize four different catalytic surfaces, namely Ru/AC0, Ru/AC1, Ru-Na/AC0 and Ru-Na/AC1. They are composed of 2%Ru or 2%Ru-4.5%Na supported on an active carbon with (AC0) and without surface groups (AC1). The AC1 carbon (1162 m2 g−1) is obtained by treatment of AC0 (960 m2 g−1) in N2 at 900 °C. Ru/AC0 and Ru/AC1 catalysts are prepared by impregnation of the supports with aqueous solutions of Ru(NO)(NO3)3. Na-promoted catalysts are then prepared by impregnation of Ru catalysts with NaOH solutions. An overall picture of the surface mobility phenomena on the four different catalytic surfaces has been described. It has been demonstrated that the presence of Na promoter in Ru-Na/AC0 and Ru-Na/AC1 catalysts inhibits the spillover of H atoms from the Ru particles to the AC surface. However, for non Na promoted catalysts, the extension of the H spillover phenomenon depends on the amount of oxygen groups present on the AC surface. Likewise, the formation of a ruthenium hydride during the reduction treatment is suggested for catalysts promoted or not by Na. Finally, this work shows how the kinetics of the H2/D2 isotopic exchange reaction may be related to the surface electron density of the catalyst, which allows us to better understand the effect that both promoter and support have on the metal particles.

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Keywords
H/D exchange; Hydrogen-deuterium exchange; Hydrogen equilibration; Ruthenium catalysts; Hydrogen chemisorption over ruthenium; Carbon supports; Promotion by sodium; Ammonia synthesis
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H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 259, Part 1, 1 January 2016, Pages 9–18
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us