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Self-activation and self-regenerative activity of trace Rh-doped Ni/Mg(Al)O catalysts in steam reforming of methane

Paper ID Volume ID Publish Year Pages File Format Full-Text
43429 45969 2007 12 PDF Available
Title
Self-activation and self-regenerative activity of trace Rh-doped Ni/Mg(Al)O catalysts in steam reforming of methane
Abstract

Ni/Mg(Al)O catalyst doped with trace amounts of Rh was tested in steam reforming of methane and the catalytic behavior was compared with the Ru-doped catalyst. Rh-doped Ni/Mg(Al)O catalyst showed a self-activation without any reduction treatment due to the ability for hydrogen production by CH bond cleavage. Such production led to the reduction of lattice Ni2+ in Mg(Al,Ni)O periclase to metallic Ni by hydrogen-spillover. The Rh-doped Ni/Mg(Al)O catalyst showed also a self-regenerative activity during a daily start-up and shut-down (DSS) operation of steam reforming of methane. NiRh alloy was formed in the surface layer of metallic Ni particles and Rh was located more profoundly in the particles than Ru in NiRu alloy on the Ru-doped catalyst. The Rh-doping exhibited a prominent performance, whilst the Ru-doping resulted in neither self-activation nor stable activity in the DSS operation. Although the catalyst deactivation took place by the Ni0 oxidation into the lattice Ni2+ in Mg(Al,Ni)O periclase, trace Rh assisted the regeneration of the active metallic Ni from the lattice Ni2+ by hydrogen-spillover. Even metallic Ni particles that had been strongly sintered on the Rh-Ni/Mg(Al)O catalyst by steaming at 900 °C were re-dispersed during the DSS operation, resulting in high and stable activity. The self-regeneration of the Rh-doped Ni/Mg(Al)O catalyst has been achieved by continuous rebirth of active Ni metal particles due to reversible reduction–oxidation between the metallic Ni on the surface and the lattice Ni2+ in Mg(Ni,Al)O periclase, i.e., oxidative incorporation of surface Ni0 into the lattice Ni2+ of Mg(Al,Ni)O and reductive migration of the lattice Ni2+ to the surface Ni0 by hydrogen-spillover.

Graphical abstractTrace Rh-doped Ni0.5/Mg2.5(Al)O catalyst prepared by adopting “memory effect” of hydrotalcite showed self-activation as well as regenerative activity in the steam reforming of methane not only in stationary but also in daily star-up and shut-down operation. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
CH4 reforming; Self-activation; Daily start-up and shut-down operation; Self-regeneration; Ni/Mg(Al)O catalyst; Rh-doping; Memory effect
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Self-activation and self-regenerative activity of trace Rh-doped Ni/Mg(Al)O catalysts in steam reforming of methane
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 332, Issue 1, 1 November 2007, Pages 98–109
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