Correlation between the surface properties and deNOx activity of ceria-zirconia catalysts

Adamowska, Malgorzata; Muller, S.; Costa, Patrick Da; Krztoń, Andrzej; Burg, Philippe

doi:10.1016/j.apcatb.2007.02.018

Cited by 59 publications

(28 citation statements)

References 33 publications

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“…The obtained results show, as expected, that surface area BET (S BET ) for the Ce 0.95 Zr 0.05 O 2 inverse opal (90.6 m 2 g À1 with a pore volume calculated of 0.12 cm 3 g À1 ) is greater than the one obtained by Pechini method (56 m 2 g À1 ), which is in good agreement with the results obtained by other authors, in samples of the same zirconium and cerium composition obtained by other methods [18,19]. The sensitivity to an ionizing radiation of Ce 0.95 Zr 0.05 O 2 powder samples has been studied by means of TL, in order to determine (i) the effect on the TL emission of the microstructure and (ii) its potential use in the field of dosimetry of radiations.…”

Section: Characterization Of Ce 095 Zr 005 O 2 Materialssupporting

confidence: 91%

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Isasi

Pérez

Castillo

et al. 2012

Materials Chemistry and Physics

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Section: Characterization Of Ce 095 Zr 005 O 2 Materialssupporting

confidence: 91%

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Isasi

Pérez

Castillo

et al. 2012

Materials Chemistry and Physics

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“…The arguments provided [19] to explain these results were: i) ceriumrich samples present higher availability of surface Ce 4+ sites and, ii) the better ability of these materials (solid solutions) to donate its oxygen for soot oxidation. The highest catalytic activity of Ce x Zr 1-x O 2 mixed oxides with x ~ 0.75, in comparison with higher zirconium loading, has been also reported for the selective catalytic reduction of NOx by hydrocarbons [28].…”

Section: Characterization Techniquesmentioning

confidence: 95%

Combined removal of diesel soot particulates and NO over CeO2–ZrO2 mixed oxides

Atribak

Bueno‐López

Garcı́a-Garcı́a

2008

Journal of Catalysis

261

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CeO 2 and Ce-Zr mixed oxides with different Ce:Zr ratio have been prepared, characterised by Raman spectroscopy, XRD, TEM, N 2 adsorption at -196ºC and H 2 -TPR, and tested for soot oxidation under NO x /O 2 . Among the different mixed oxides, Ce 0.76 Zr 0.24 O 2 provided the best results. Ce 0.76 Zr 0.24 O 2 presents a higher activity than pure CeO 2 for soot oxidation by NO x /O 2 when both catalysts are calcined at 500ºC (soot oxidation rates at 500ºC are 14.9 and 11.4 g soot /s, respectively), and the catalytic activity of CeO 2 decays significantly with calcination temperature (from 500 to 1000ºC) while Ceria is an important material in the framework of the three-way catalysts (TWCs) which are used in gasoline automobile catalytic converters for the treatment of exhaust gases [1,2]. One of the key functions of this material is the ability of cerium to switch between the Ce 4+ and Ce 3+ oxidation states and to incorporate more or less oxygen into their crystal structure depending on various parameters such as the gaseous atmosphere with which they are in contact, temperature and pressure [3]. Therefore, early on, ceria was given a main role as oxygen storage component in order to extend the three-way window on the lean side of stoichiometry by acting as a sink for gas-phase oxygen during rich-to- It has been established that addition of zirconium to ceria to form a mixed oxide solution greatly enhances the reducibility of Ce 4+ in the catalyst material, which has generated considerable interest in the Ce-Zr system [5][6][7][8]. The energetics of the Ce 4+ /Ce 3+ reduction step and the corresponding formation of oxygen vacancies are likely to be involved [9]. Indeed, it is clear that fundamental solid state properties such as the precise role of structural defects and dopants, the nature of redox reactions to create electronic species (both within the bulk and at the surfaces), as well as the mechanism of oxygen migration, are crucial to the greater understanding of these important materials. supplies the oxygen necessary for the redox mechanism that takes place during the reaction.The scope of this paper is to study the catalytic performance of Ce-Zr mixed oxides for the removal of soot under simulated Diesel exhaust conditions in a gas flow containing O 2 and NOx. Special attention is paid to the simultaneous removal of NOx. The catalytic activity of the Ce-Zr mixed oxides is compared with that of pure CeO 2 and the thermal stability of the pure and mixed oxides is studied in detail since the thermal stability is a key requirement for the application of these materials in a real soot trap. 2.-Experimental Catalyst preparationCe-Zr mixed oxides with different metal ratio were prepared by using a coprecipitation route. The required amounts of ZrO(NO 3 ) 2 ·6H 2 O and/or Ce(NO 3 ) 3 ·6H 2 O (supplied by Aldrich) were dissolved in water and the hydroxides were precipitated by dropping an ammonia solution to keep the pH about 9. The precipitates were dried at 90ºCin air overnight and calcined in air ...

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“…[9,16] On the other hand, the CeO 2 -ZrO 2 composite oxide, an excellent catalyst support that was industrialized in threewayc atalysis to eliminate exhaust gases, shows redox and catalytic properties that are increased relative to those of pure CeO 2 . [7,9,[17][18][19] On the basis of the abovementioned literature, however, we found that:1 )few studies are performed with the use of other ceria-containing composite oxidest oe xplore the influenceb etween the physicochemical properties and the catalytic activities on NO reduction by CO, and ad irect comparison between different doped metal cations is also lacking; 2) most studies are focusedo nC e/M (M:f oreignm etal)m olar ratios less than 20, but little attention has been paid to higher molar ratios of Ce/M, for example, Ce/M molarr atios of 20 or higher.F urthermore, it shouldb en oted that ac lear change in the characteristics of the materials may be observed if as mall amount of foreign metal cations is doped into the ceria. In addition, variable valencem etal cations, such as Ti 4 + /Ti 3 + ,d oped into the ceria can promote the catalytic activity owing to easier electron exchange between Ce 4 + /Ce 3 + and Ti 4 + /Ti 3 + relative to that in the CeO 2 -ZrO 2 composite oxide.…”

Section: Introductionmentioning

confidence: 99%

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce₂₀M₁O_x (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

Deng

Qian

et al. 2016

Chemistry An Asian Journal

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This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N2 physisorption, X-ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by hydrogen and by oxygen (H2 -TPR and O2 -TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M(x+) into the lattice of CeO2 increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O2 (-) (and/or O(-) ) species of these Ce20 M1 Ox composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce20 Cr1 Ox exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near-surface Ce(3+) and Cr(3+) . Finally, a possible reaction mechanism was tentatively proposed to understand the reactions.

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Correlation between the surface properties and deNOx activity of ceria-zirconia catalysts

Cited by 59 publications

References 33 publications

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Combined removal of diesel soot particulates and NO over CeO2–ZrO2 mixed oxides

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce₂₀M₁O_x (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

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Correlation between the surface properties and deNOx activity of ceria-zirconia catalysts

Cited by 59 publications

References 33 publications

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by sol–gel and template methods

Combined removal of diesel soot particulates and NO over CeO2–ZrO2 mixed oxides

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20M1Ox (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

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A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce₂₀M₁O_x (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide