Kinetics and mechanism of the low-temperature water–gas shift reaction on Au/CeO2 catalysts in an idealized reaction atmosphere

Leppelt, R.; Schumacher, B.; Plzak, V.; Kinne, M.; Behm, R. Jürgen

doi:10.1016/j.jcat.2006.08.020

Cited by 196 publications

(173 citation statements)

References 73 publications

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“…Among the reducible oxide supports, ceria was particularly investigated because of its capability to act as an oxygen reservoir by storing/releasing oxygen through a redox process which involves the Ce 4+ /Ce 3+ couple. Nanocrystalline ceria-supported gold catalysts were then studied in various catalytic reactions including the water-gas shift reaction [4,5], the VOC combustion [6][7][8][9][10], the selective oxidation of alcohol [11], the selective oxidation of CO in excess of H 2 (CO-PROX) [12], and the most investigated reaction remaining the low-temperature CO oxidation [13,14]. The morphology of Electronic supplementary material The online version of this article (doi:10.1007/s13404-013-0103-z) contains supplementary material, which is available to authorized users.…”

Section: Introductionmentioning

confidence: 99%

Understanding of the oxygen activation on ceria- and ceria/alumina-supported gold catalysts: a study combining 18O/16O isotopic exchange and EPR spectroscopy

et al. 2013

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Gold supported on ceria or ceria-alumina mixed oxides are very active catalysts for total oxidation of a variety of molecules. The key step of the oxygen activation on such catalysts is still a matter of debate. Gold-ceria (Au/CeO 2 ) and gold-ceria-alumina (Au/CeO 2 /Al 2 O 3 ) catalysts were prepared by deposition-precipitation of gold precursor with urea as in former works where their efficiency to catalyze the oxidation of propene and propan-2-ol was demonstrated. To understand the phenomenon of oxygen activation over this class of catalysts, efficient techniques generally used to characterize the interaction between oxygen and cerium-based oxides were applied; the oxygen storage capacity (OSC) measurement, the O (g) ), indicating that gold did not promote the dissociation of dioxygen. Peroxo adspecies were observed by Raman spectroscopy only in the presence of gold. On the contrary, EPR spectroscopy indicated that the concentration of superoxo adspecies was lower for oxide-supported gold samples than for bare oxides. The combination of techniques allowed reinforcing the hypothesis that the gold nanoparticules promote the activation of dioxygen by generating extremely mobile diatomicoxygenated species at the gold/ceria interfacial perimeter. This specific gold-ceria interaction, which leads to the increase in oxygen mobility, is probably also responsible for the higher catalytic performance of Au/CeO 2 and Au/CeO 2 /Al 2 O 3 in oxidation reaction compared to bare supports.

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Section: Introductionmentioning

confidence: 99%

Understanding of the oxygen activation on ceria- and ceria/alumina-supported gold catalysts: a study combining 18O/16O isotopic exchange and EPR spectroscopy

et al. 2013

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“…Kinetic isotope effect and isotopic tracer studies suggested that the rate-limiting step of the forward formate decomposition was the C-H bond rupture, aided by the noble metal [25]. Behm et al [28] carried out a quantitative analysis of the rate of formate surface decomposition over a Au/CeO 2 catalyst and proposed that formates could account for about half of the CO 2 produced. This calculation was based on the nonsteady-state measurement of the rate constant of formate decomposition (i.e., during desorption under 2% H 2 O in N 2 ) and an estimate of the formate surface coverage determined via TPD under N 2 of a catalyst pretreated under WGS conditions.…”

Section: Introductionmentioning

confidence: 99%

Quantitative analysis of the reactivity of formate species seen by DRIFTS over a Au/Ce(La)O2 water–gas shift catalyst: First unambiguous evidence of the minority role of formates as reaction intermediates

Meunier¹,

Reid

Goguet

et al. 2007

Journal of Catalysis

179

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(2007). Quantitative analysis of the reactivity of formate species seen by DRIFTS over a Au/Ce(La)O2 water-gas shift catalyst: First unambiguous evidence of the minority role of formates as reaction intermediates. Journal of Catalysis, 247(2)(2), 277-287. DOI: 10.1016DOI: 10. /j.jcat.2007 Published in: Journal of Catalysis Queen's University Belfast -Research Portal: Link to publication record in Queen's University Belfast Research Portal General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. AbstractThe reactivity of the species formed at the surface of a Au/Ce(La)O 2 catalyst during the water-gas shift (WGS) reaction were investigated by operando diffuse reflectance Fourier transform spectroscopy (DRIFTS) at the chemical steady state during isotopic transient kinetic analyses (SSITKA). The exchanges of the reaction product CO 2 and of formate and carbonate surface species were followed during an isotopic exchange of the reactant CO using a DRIFTS cell as a single reactor. The DRIFTS cell was a modified commercial cell that yielded identical reaction rates to that measured over a quartz plug-flow reactor. The DRIFTS signal was used to quantify the relative concentrations of the surface species and CO 2 . The analysis of the formate exchange curves between 428 and 493 K showed that at least two levels of reactivity were present. "Slow formates" displayed an exchange rate constant 10-to 20-fold slower than that of the reaction product CO 2 . "Fast formates" were exchanged on a time scale similar to that of CO 2 . Multiple nonreactive readsorption of CO 2 took place, accounting for the kinetics of the exchange of CO 2 (g) and making it impossible to determine the number of active sites through the SSITKA technique. The concentration (in mol g −1 ) of formates on the catalyst was determined through a calibration curve and allowed calculation of the specific rate of formate decomposition. The rate of CO 2 formation was more than an order of magnitude higher than the rate of decomposition of formates (slow + fast species), indicating that all of the formates detected by DRIFTS could not be the main reaction intermediates in the production of CO 2 . This work stresses the importance of full quantitative analyses (measuring both rate constants and adsorbate concentrations) when investigating the role of adsorbates as potential reaction intermediates, and illustrates how even reactive species seen by DRIFTS may be unimportant in the overall reaction scheme.

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“…oxygen vacancy formation, are were expected. It is well known that, in the case of the chlorinated catalyst, an increase in the reduction temperature favors the formation of CeOCl entities, thus stabilizing Ce (III) species [17,31] and, consequently, producing a decrease of the OSC [22,29,[32][33][34] . This effect could affect the catalytic activity and in fact, as will be discussed below, a poorer CO conversion in the case of the Cl-containing catalyst reduced at 773 K than reduced at 523 K was observed, probably due to decrease of the OSC.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Influence of the metal precursor on the catalytic behavior of Pt/Ceria catalysts in the preferential oxidation of CO in the presence of H2 (PROX)

Jardim

Rico-Francés

Coloma

et al. 2015

Journal of Colloid and Interface Science

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The effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H2 over Pt/CeO2 catalysts has been studied. The catalysts were prepared using (Pt(NH3)4)(NO3)2 and H2PtCl6, as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst. This is a previous version of the article published in Journal of Colloid and Interface Science. 2015, 443: 45-55. doi:10.1016/j.jcis.2014 3: Graphical Abstract (for review)• The presence or absence of Cl in the Pt precursor strongly affects the catalytic behavior.• The Pt precursor affects the PROX mechanism at low reaction temperatures.• At 333 K, the mechanism in the Cl-free catalyst seems to involve the -OH groups on the support.• At higher temperatures, the reaction occurs via the same mechanism on both catalysts.. Highlights (for review) AbstractThe effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H 2 over Pt/CeO 2 catalysts has been studied. The catalysts are prepared using (Pt(NH 3 ) 4 )(NO 3 ) 2 and H 2 PtCl 6 , as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO 2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst.

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Kinetics and mechanism of the low-temperature water–gas shift reaction on Au/CeO2 catalysts in an idealized reaction atmosphere

Cited by 196 publications

References 73 publications

Understanding of the oxygen activation on ceria- and ceria/alumina-supported gold catalysts: a study combining 18O/16O isotopic exchange and EPR spectroscopy

Understanding of the oxygen activation on ceria- and ceria/alumina-supported gold catalysts: a study combining 18O/16O isotopic exchange and EPR spectroscopy

Quantitative analysis of the reactivity of formate species seen by DRIFTS over a Au/Ce(La)O2 water–gas shift catalyst: First unambiguous evidence of the minority role of formates as reaction intermediates

Influence of the metal precursor on the catalytic behavior of Pt/Ceria catalysts in the preferential oxidation of CO in the presence of H2 (PROX)

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