Rh oxide reducibility and catalytic activity of model Pt–Rh catalysts

Suopanki, Aslak; Polvinen, R.; Valden, M.; Härkönen, Matti

doi:10.1016/j.cattod.2004.10.020

Cited by 13 publications

(5 citation statements)

References 17 publications

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“…The XPS Rh 3d spectra for Rh/CeO2 system studied by Force et al [84] was deconvoluted into three peaks, respectively assigned to Rh 0 (306.8 eV), Rh + (307.8 eV), Rh 3+ (309.2 eV) states. While other systems have different interpretations [85]. In our Rh/CZO system, assigning XPS peaks to Rh 0 and Rh δ+ species is easier for comparison.…”

Section: Catalyst Metal Dispersion (%) Freshmentioning

confidence: 92%

Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

et al. 2015

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The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration is accomplished by reduction with H2 generated through steam reforming catalyzed by Rh 0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al2O3 and 0.5% Rh/CexOy-ZrO2 (CZO) as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al2O3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al2O3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO2)y) complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh2O3 and were relatively easy to be reduced to active Rh 0 during regeneration.

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Section: Catalyst Metal Dispersion (%) Freshmentioning

confidence: 92%

Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

et al. 2015

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“…As proposed in our study,c eria in this sample is in intimatec ontact with the rhodium particles, isolating them from facile oxidation.A nX PS study reported by Suopanki et al indicated that the fraction of reducible rhodium had the best catalytic activity;t hey explained the existence of metallic rhodium in the system by buryingo ft he active material into the bulk of the washcoat. [43] The absence of the geminal dicarbonyl and the adsorption of mostly linear and bridged CO species on metallicR ha lso indicate the proximity of Rh and Ce species. These CO sites are in relatively good agreement with those reported for CO adsorbed on Rh/reduced CeO 2 (111)m onitored by high-resolution electron energy loss (HREEL) spectroscopy.…”

Section: Rh/al 2 Omentioning

confidence: 99%

Time‐Resolved, In Situ DRIFTS/EDE/MS Studies on Alumina‐Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions

Kroner¹,

Newton²,

Tromp³

et al. 2014

ChemPhysChem

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The effects of ceria and zirconia on the structure–function properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ-Al2O3) during CO exposure are described. Ceria and zirconia are introduced through two preparation methods: 1) ceria is deposited on γ-Al2O3 from [Ce(acac)3] and rhodium metal is subsequently added, and 2) through the controlled surface modification (CSM) technique, which involves the decomposition of [M(acac)x] (M=Ce, x=3; M=Zr, x=4) on Rh/γ-Al2O3. The structure–function correlations of ceria and/or zirconia-doped rhodium catalysts are investigated by diffuse reflectance infrared Fourier-transform spectroscopy/energy-dispersive extended X-ray absorption spectroscopy/mass spectrometry (DRIFTS/EDE/MS) under time-resolved, in situ conditions. CeOx and ZrO2 facilitate the protection of Rh particles against extensive oxidation in air and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts prepared by CSM are observed and compared with Rh/γ-Al2O3 samples, whereas supported Rh particles are easily disrupted by CO forming mononuclear Rh geminal dicarbonyl species. DRIFTS results indicate that, through the interaction of CO with ceriated Rh particles, a significantly larger amount of linear CO species form; this suggests the predominance of a metallic Rh phase.

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“…In this work, the Pd-only catalysts supported on nanophase (Ce, Zr, Pr)O 2 -doped alumina coatings show high activity of NO conversion. The light-off temperatures of fresh Pd/CZPA-S and Pd/CZPA-P are as low as 210 and 234°C, respectively, which are similar to the Pt/Rh TWC (Suopankia et al, 2005).…”

Section: Catalytic Activitymentioning

confidence: 57%

Preparation and properties of nanophase (Ce, Zr, Pr)O2-doped alumina coating on cordierite ceramic honeycomb for three-way catalysts

Tian

2012

Braz. J. Chem. Eng.

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-Nanophase (Ce, Zr, Pr)O 2 -doped alumina coatings were prepared by impregnating the cordierite ceramic honeycomb in the sol or in the slurry of already calcined powder, respectively. The effects of preparation methods on the crystal phase, texture, oxygen storage capacity (OSC), reducibility, surface morphology and thermal stability of coatings were investigated by X-ray diffraction (XRD), the Brunauer Emmet Teller (BET) method, the oxygen pulsing technique, H 2 -temperature-programmed reduction (H 2 -TPR) and scanning electron microscopy (SEM). These nanophase (Ce, Zr, Pr)O 2 -doped alumina coatings were used as supports to prepare Pd-only three-way catalysts, and evaluated with respect to catalytic activities. The results indicate that the nanophase (Ce, Zr, Pr)O 2 -doped alumina coatings prepared by the two methods have high thermal stability. However, the coating derived from the sol shows better crystalline structure, texture, reducibility and oxygen storage capacity than the coating derived from the slurry. SEM observation shows that the morphology of the coating derived from the sol is uniform and smooth. The Pd-only catalyst derived from the sol exhibits high three-way catalytic activity at low temperature and thermal stability, suggesting a great potential for applications.

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Rh oxide reducibility and catalytic activity of model Pt–Rh catalysts

Cited by 13 publications

References 17 publications

Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

Time‐Resolved, In Situ DRIFTS/EDE/MS Studies on Alumina‐Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions

Preparation and properties of nanophase (Ce, Zr, Pr)O2-doped alumina coating on cordierite ceramic honeycomb for three-way catalysts

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