Temperature-induced evolution of reaction sites and mechanisms during preferential oxidation of CO

Kydd, Richard; Ferri, Davide; Hug, P.; Scott, Jason; Teoh, Wey Yang; Amal, Rose

doi:10.1016/j.jcat.2010.10.009

Cited by 86 publications

(60 citation statements)

References 29 publications

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“…A third zone (III) is detected at higher temperatures whereby the H 2 oxidation reaction rate changes in coincidence with a sharp increase of the Cu + contribution. This can be related to the formation of less active Cu 2 O and/or to sintering of the copper prior to generation of metallic copper [40,73]. This is detected at the highest reaction temperature and its formation fairly coincides with the formation of Ce 3+ states (not shown; see [41] for details).…”

Section: Nature Of Active Sites/entities and Further Hints On Catalytmentioning

confidence: 86%

“…This has, however, been refuted recently by Kydd et al [73], who suggest that some degree of competency between H 2 and CO for the active sites may arise at relatively high reaction temperatures, in the non-selective region, when CO desorption from active reduced copper sites become favored, even though, to the best of our knowledge, no direct evidence for this is available yet [73]. Another recent finding is related to a very recent study in which three samples of copper oxide supported by ceria with different surface morphological characteristics (nanocubes exposing (100) faces at their surface, nanorods exposing (110) and (100) faces and nanospheres with polyhedral shape) have been examined with respect to their CO-PROX performance [42].…”

Section: Nature Of Active Sites/entities and Further Hints On Catalytmentioning

confidence: 94%

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Characterization of Active Sites/Entities and Redox/Catalytic Correlations in Copper-Ceria-Based Catalysts for Preferential Oxidation of CO in H2-Rich Streams

et al. 2013

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This article reviews work done at authors' laboratories about catalysts based on combinations between copper and ceria for preferential oxidation of CO in H 2 -rich streams (CO-PROX). The main focus of this review is the characterization of active sites for the process on the basis of spectroscopic analysis of the systems under reaction conditions (operando techniques). On such a basis, it is exposed the state of the art in this field in connection with results obtained in other laboratories. OPEN ACCESSCatalysts 2013, 3 379 Keywords: copper-ceria catalysts; CO preferential oxidation (CO-PROX); diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS); X-ray absorption near edge spectroscopy (XANES); Raman; X-ray diffraction (XRD); X-ray photoelectron spectroscopy (XPS)

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Section: Nature Of Active Sites/entities and Further Hints On Catalytmentioning

confidence: 86%

Section: Nature Of Active Sites/entities and Further Hints On Catalytmentioning

confidence: 94%

Characterization of Active Sites/Entities and Redox/Catalytic Correlations in Copper-Ceria-Based Catalysts for Preferential Oxidation of CO in H2-Rich Streams

et al. 2013

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“…As to the sample 3CUCE, no copper-containing phases are discerned in the pattern, most probably due to high dispersion of CuO nanoparticles with too small particle sizes to be identified by the conventional XRD method. The average crystallite size of ceria has been estimated by Rietveld methodology [55,56] and summarized in Table 1. After the addition of copper oxide, the crystallite size of cerianite slightly increases and its value changes from 9.5 to 9.9 nm for all the catalysts.…”

Section: Co-prox Catalytic Activitymentioning

confidence: 99%

Preferential CO oxidation (CO-PROX) catalyzed by CuO supported on nanocrystalline CeO2 prepared by a freeze-drying method

Arango-Díaz

Moretti

Talon

et al. 2014

Applied Catalysis A: General

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a b s t r a c tNanocrystalline CeO 2 with a regular size of 9.5 nm was prepared by a freeze-drying method, and subsequent impregnated with a Cu(II) acetate solution, varying the loading of Cu (3, 6, 12 wt.%). The resulting CuO/CeO 2 materials were characterized by N 2 physisorption at −196 • C, HRTEM, H 2 -TPR, X-ray diffraction, Raman spectroscopy and XPS and tested as catalysts in the preferential CO oxidation in a H 2 -rich stream (CO-PROX) in the temperature range • C. In spite of their low specific surface areas the catalysts exhibited a good catalytic performance, resulting active and selective in the CO-PROX reaction at low temperatures. The inhibiting effect of the simultaneous presence of CO 2 (15 vol.%) and H 2 O (10 vol.%) in the reaction mixture on the performance of CuO-CeO 2 catalysts was also investigated. The addition of CO 2 and water in the gas stream depressed CO oxidation up to 160• C, its effect being negligible at higher temperatures. Nevertheless, despite these expected deactivation phenomena, a CO conversion value higher than 90% and a CO 2 selectivity of about 90% was achieved for all the samples at 160• C. The excellent performance, especially shown by the catalyst with 6 wt%. of copper, has been related to the wide dispersion of the copper active sites associated with the high amount of Ce 4+ species before reaction.

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“…CuO/CeO 2 catalysts represent a cheaper and more selective alternative to noble metals and have been widely investigated in the last decades [3,5,[32][33][34], focusing on methods to further improve performance based on doping [6,8,10,18,22,[35][36][37][38][39][40][41][42] or unconventional preparation methods [4,11,12,18,[43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

Improved CO-PROX Performance of CuO/CeO2 Catalysts by Using Nanometric Ceria as Support

2018

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Abstract:Despite of the huge number of papers about the catalytic preferential oxidation of CO (CO-PROX) for the purification of H 2 streams, there is still a need for more effective catalysts in order to reduce the large required catalyst volume of CO-PROX unity. In this work, large surface area nanometric ceria was used as support for CuO/CeO 2 catalysts with CuO load up to 10 wt % easily dispersed by wet impregnation. Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N 2 physisorption, H 2 temperature programmed reduction (TPR), and CO 2 temperature programmed desorption (TPD) and tested under different reaction conditions (including under feed containing inhibiting species such as CO 2 and H 2 O). Catalytic tests revealed that our samples show high activity and selectivity even under stringent reaction conditions; moreover, they result among the most active catalysts when compared to those reported in the scientific literature. The high activity can be related to the enhanced amount of highly dispersed copper sites in strong interaction with ceria related to the nature of the nanometric support, as evidenced by the characterization techniques. Despite the high concentration of active copper sites, catalytic performance is limited by CO 2 desorption from ceria in the neighborhood of copper sites, which prevents a further improvement. This suggests that new catalyst formulations should also provide a lower affinity towards CO 2 .

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Temperature-induced evolution of reaction sites and mechanisms during preferential oxidation of CO

Cited by 86 publications

References 29 publications

Characterization of Active Sites/Entities and Redox/Catalytic Correlations in Copper-Ceria-Based Catalysts for Preferential Oxidation of CO in H2-Rich Streams

Characterization of Active Sites/Entities and Redox/Catalytic Correlations in Copper-Ceria-Based Catalysts for Preferential Oxidation of CO in H2-Rich Streams

Preferential CO oxidation (CO-PROX) catalyzed by CuO supported on nanocrystalline CeO2 prepared by a freeze-drying method

Improved CO-PROX Performance of CuO/CeO2 Catalysts by Using Nanometric Ceria as Support

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