Reduction of cerias with different textures by hydrogen and their reoxidation by oxygen

Perrichon, V.; Laachir, A.; Bergeret, G.; Fréty, R.; Tournayan, L.; Touret, Olivier

doi:10.1039/ft9949000773

Cited by 273 publications

(164 citation statements)

References 28 publications

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“…The higher hydrogen uptake of CeO 2 (rod) (571 lmol/g) than that of CeO 2 (cube) (121 lmol/g) is due to the difference in surface area. The reduction of the support materials (not shown) takes place in the region 723-823 K in agreement with results for conventional CeO 2 [47]. The reduction of Au/CeO 2 (rod) and Au/CeO 2 (rod)-CN occurs around 430 K. The hydrogen uptake takes place in a much broader temperature range for the former catalyst than for the latter.…”

Section: Resultssupporting

confidence: 75%

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

et al. 2011

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The interaction of gold atoms with CeO 2 nanocrystals having rod and cube shapes has been examined by cyanide leaching, TEM, TPR, CO IR and X-ray absorption spectroscopy. After deposition-precipitation and calcination of gold, these surfaces contain gold nanoparticles in the range 2-6 nm. For the ceria nanorods, a substantial amount of gold is present as cations that replace Ce ions in the surface as follows from their first and second coordination shells of oxygen and cerium by EXAFS analysis. These cations are stable against cyanide leaching in contrast to gold nanoparticles. Upon reduction the isolated Au atoms form finely dispersed metal clusters with a high activity in CO oxidation, the WGS reaction and 1,3-butadiene hydrogenation. By analogy with the very low activity of reduced gold nanoparticles on ceria nanocubes exposing the {100} surface plane, it is inferred that the gold nanoparticles on the ceria nanorod surface also have a low activity in such reactions. Although the finely dispersed Au clusters are thermally stable up to quite high temperature in line with earlier findings (Y. Guan and E. J. M. Hensen, Phys Chem Chem Phys 11:9578, 2009), the presence of gold nanoparticles results in their more facile agglomeration, especially in the presence of water (e.g., WGS conditions). For liquid phase alcohol oxidation, metallic gold nanoparticles are the active sites. In the absence of a base, the O-H bond cleavage appears to be rate limiting, while this shifts to C-H bond activation after addition of NaOH. In the latter case, the gold nanoparticles on the surface of ceria nanocubes are much more active than those on the surface of nanorod ceria.

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Section: Resultssupporting

confidence: 75%

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

et al. 2011

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“…A good review is given by Trovarelli [1]. Temperature-programmed reduction (TPR) has been used to characterize the surface and bulk oxygen reducibility of these modi®ed cerium oxide systems [3,4,13,24,25].…”

Section: Introductionmentioning

confidence: 99%

Reduction characteristics of copper oxide in cerium and zirconium oxide systems

Kundakovic

Flytzani‐Stephanopoulos

1998

Applied Catalysis A: General

386

173

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The reduction of CuO dispersed on¯uorite-type oxide catalysts, namely La-doped CeO 2 and Y-doped ZrO 2 was studied in this work. On both supports distinct copper species were identi®ed as a function of copper content by temperatureprogrammed reduction (TPR) by H 2 and CH 4 , X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy/energy dispersive X-ray (STEM/EDX) analyses. At low copper loading (<15 at%), the copper phase is present as small clusters, which are reduced at lower temperature than bulk CuO. At higher Cu loading (>15 at%), in addition to clusters, larger CuO particles are present which are reduced at higher temperature close to the reduction temperature of bulk CuO. At copper loading lower than ca. 5 at%, copper is present as highly dispersed clusters or isolated Cu ions, which interact strongly with the¯uorite-type oxide, thus requiring higher reduction temperature. However, the latter is still below the bulk CuO reduction temperature. Copper is more stabilized when dispersed in Ce(La)O 2 than in Zr(Y)O 2 matrix, so that reduction of copper oxide species requires lower temperatures on the Zr(Y)O 2 -based catalysts. The reducibility of the doped ceria is enhanced by the presence of copper in both H 2 -and CH 4 -TPR. On the other hand no such interaction is present in CuZr(Y)O 2 system. The activity of various copper species for methane oxidation is discussed. # 1998 Elsevier Science B.V. All rights reserved.

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“…4. There are two reduction peaks related to CeO2, which have been described in the literature (Yao et al 1984;Perrichon et al 1994). The one located at 570 °C (peak ) was attributed to the reduction of the CeO2 surface oxygen; the other peak at 890 °C (peak ) was associated with the reduction of bulk part of CeO2, which emerged through removing the reactive oxygen species (O 2-) from the reticulum and forming the Ce2O3 (2CeO2 + H2 → Ce2O3 + H2O).…”

Section: Temperature Programmed Reduction (H2-tpr)mentioning

confidence: 99%

“…8d. Thus, the formation of carbon deposition and the caking of catalysts were inhibited by adding CeO2 (Chiou et al 2014;Vicente et al 2014) because it was well known that CeO2 has unique redox properties and high oxygen vacancy and mobility, which can promote the gasification of carbonaceous species deposited on a catalyst (Perrichon et al 1994;Zhang et al 2014;Li et al 2015). Figures 8c and 8d also showed that some spherical particles were attached on the surface of catalysts after reaction, wherein the particles attached on the surface of NF/C0.4PG0.6 catalyst were in a more uniform distribution than those attached on NF/PG.…”

Section: Characterizations Of Spent Catalystsmentioning

confidence: 99%

“…Iron species, as one of the ingredient of active phase, not only can change the redox properties of Ni-based catalysts by forming Fe2O3 or Fe3O4, but also produce the NiFe alloy upon the interaction between Ni and Fe Bolshak et al 2013). Additionally, CeO2 also has promising redox properties and high oxygen vacancy and mobility, which can promote the gasification of carbonaceous species deposited on the catalyst (Perrichon et al 1994;Zhang et al 2014;Li et al 2015). Therefore, the specialties of iron and ceria could restrain the sintering of active metallic nickel and the forming of coke precursor, and then enhance the activity and stability of Ni-based catalyst.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Production from Steam Reforming of Acetic Acid over Ni-Fe/Palygorskite Modified with Cerium

Wang¹,

Chen²,

Yang³

et al. 2017

BioResources

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The steam reforming of acetic acid (SRA) was carried out in a fixed-bed tubular reactor with Ni-Fe/ceria-palygorskite (CPG) catalysts. The asprepared catalysts were analyzed by N2 adsorption-desorption, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), H2 temperature programmed reduction (H2-TPR), and X-ray diffraction (XRD). The results of H2-TPR and XRD showed that the addition of CeO2 increased the hydrogen consumption of catalysts and the interaction force between active component (Ni-Fe alloy) and carrier. Moreover, the Ni-Fe alloys were successfully synthesized in the Ni-Fe/CPG catalysts and their crystallite sizes were decreased by adding CeO2. In addition, these catalysts were employed to SRA at 600 °C, GHSV = 14427 h -1 and different molar ratio of S/C. The experimental results revealed that the Ni-Fe/C0.4PG0.6 catalyst can achieve the highest yield of H2 (87%) and HOAc conversion (95%), as well as the highest stability during the process of steam SRA. Additionally, the spent catalysts were characterized by XRD, SEM, and thermogravimetric analysis (TGA). The results showed that the addition of CeO2 enhanced the stability and activity of Ni-Fe/palygorskite catalyst and reduced the coke deposition rate on the catalyst surface.

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Reduction of cerias with different textures by hydrogen and their reoxidation by oxygen

Cited by 273 publications

References 28 publications

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

Reduction characteristics of copper oxide in cerium and zirconium oxide systems

Hydrogen Production from Steam Reforming of Acetic Acid over Ni-Fe/Palygorskite Modified with Cerium

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