Characterization of model automotive exhaust catalysts: Pd on ceria and ceria–zirconia supports

Jen, Hung-Wen; Graham, George W.; Wang, Chun; McCabe, Robert W.; Cuif, Jean‐Pierre; Deutsch, Steven; Touret, Olivier

doi:10.1016/s0920-5861(98)00512-4

Cited by 219 publications

(117 citation statements)

References 16 publications

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“…Such results are also consistent with the general considerations that the reduction temperature of PdO in Pd/CeO 2 shifts to a higher value compared with the individual PdO, while the reduction temperature of CeO 2 in Pd/CeO 2 is lower than that of individual CeO 2 , due to the interaction between PdO and CeO 2 [12,47].…”

Section: H 2 -Tprsupporting

confidence: 91%

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Zhu

2004

Journal of Catalysis

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The catalysts Pd/TiO 2 , Pd/CeO 2 , and Pd/CeO 2 -TiO 2 for CO oxidation at low temperature together with their corresponding supports TiO 2 , CeO 2 , and CeO 2 -TiO 2 prepared by sol-gel precipitation followed by supercritical fluid drying were characterized by means of N 2 adsorption, XRD, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO adsorption and temperature-programmed reduction (TPR) with H 2 and CO as reducing agents. The results showed that PdO is finely dispersed on the supports with high surface area. DRIFTS of CO adsorption further indicated that both Pd 2+ and Pd 0 species coexist in Pd/CeO 2 , while only Pd 0 is detected in Pd/TiO 2 and Pd/CeO 2 -TiO 2 . H 2 -TPR showed that no bulk CeO 2 exists in CeO 2 -TiO 2 and the reduction of CeO 2 -TiO 2 is more difficult than that of the surface oxygen in the individual CeO 2 probably due to the formation of CeO 2 -TiO 2 solid solution. PdO in Pd/TiO 2 can be fully reduced by H 2 at ambient temperature, whereas PdO in Pd/CeO 2 and Pd/CeO 2 -TiO 2 is reduced respectively at 162 and 80 • C, accompanied by the reduction of surface CeO 2 . CO-TPR showed that the reduction of PdO in PdO/TiO 2 is limited within the outermost layer at ambient temperature and the core PdO can only be reduced with a further increase of temperature. PdO/CeO 2 is also reduced both at ambient temperature and with the increase of temperature during the CO-TPR process, and the reduction temperature of CeO 2 decreased significantly in the presence of PdO, which may be due to the different degrees of interaction between PdO and CeO 2 . In contrast, a complete reduction of PdO in Pd/CeO 2 -TiO 2 by CO is observed at ambient temperature, accompanied by the partial reduction of CeO 2 , which may indicate that the special Pd-Ce-Ti interaction in Pd/CeO 2 -TiO 2 is favorable for the reduction of PdO and interfacial CeO 2 species. The water-gas shift (WGS) between CO and the hydroxyl groups in the catalysts is detected at a temperature higher than 210 • C on all of the Pd-supported catalysts as well as the individual CeO 2 and TiO 2 supports.  2004 Elsevier Inc. All rights reserved.

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Section: H 2 -Tprsupporting

confidence: 91%

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Zhu

2004

Journal of Catalysis

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“…24, 25 While the presence of two distinct peaks could be due to different chemical processes, the complexities of the transient processes that occur during TPR prevent definitive interpretation of these peaks. 26 Interestingly, the only well-defined feature observed during the temperature ramp on this sample is a small negative peak at~80…”

Section: Resultsmentioning

confidence: 99%

Novel embedded Pd@CeO₂catalysts: a way to active and stable catalysts

Cargnello

Montini

Polizzi³

et al. 2010

Dalton Trans.

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1-wt% Pd-CeO 2 catalysts were prepared by co-precipitation of Pd nanoparticles with ceria (Pd@CeO 2 -CP), by a microemulsion procedure (Pd@CeO 2 -ME), and by normal impregnation of Pd salts (Pd/CeO 2 -IMP) in order to test the concept that Pd-CeO 2 catalysts could be more stable for the water-gas-shift (WGS) reaction when the Pd is embedded in CeO 2 . Initial WGS rates measured at 250• C were similar for the Pd@CeO 2 -CP and Pd/CeO 2 -IMP, indicating that Pd was accessible for gas-phase reactions on both catalysts. Pd@CeO 2 -CP exhibited better stability for WGS than did Pd/CeO 2 -IMP but exposure to the WGS environment at 400• C still caused a decrease in activity.Physical characterization of the Pd@CeO 2 -ME implied that the core-shell nanoparticles underwent condensation that resulted in a low surface area and poor Pd accessibility. However, the Pd@CeO 2 -ME sample exhibited good stability for WGS, suggesting that more effective encapsulation of Pd can limit the sintering of the metal phase, thus resulting in stable catalysts under high temperature reaction conditions.

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“…13 With regard to catalytic ozonation of organic compounds in water with supported PdO, there is still no report. PdO had been found effective in decomposing aqueous ozone, 14 but intermediates in this process are unknown.…”

Section: Articlementioning

confidence: 99%

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

Zhang

Croué

2011

Environ. Sci. Technol.

160

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The cerium supported palladium oxide (PdO/CeO2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO2 of the catalyst forming surface complexes, and 2) O3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O2), and O2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter.

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Characterization of model automotive exhaust catalysts: Pd on ceria and ceria–zirconia supports

Cited by 219 publications

References 16 publications

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Novel embedded Pd@CeO₂catalysts: a way to active and stable catalysts

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

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Characterization of model automotive exhaust catalysts: Pd on ceria and ceria–zirconia supports

Cited by 219 publications

References 16 publications

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Pd/CeO2?TiO2 catalyst for CO oxidation at low temperature: a TPR study with H2 and CO as reducing agents

Novel embedded Pd@CeO2catalysts: a way to active and stable catalysts

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

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Product

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Novel embedded Pd@CeO₂catalysts: a way to active and stable catalysts