Influence of CO2 and H2 on the low-temperature water–gas shift reaction on Au/CeO2 catalysts in idealized and realistic reformate

Denkwitz, Y.; Karpenko, A.; Plzak, V.; Leppelt, R.; Schumacher, B.; Behm, R. J.

doi:10.1016/j.jcat.2006.11.012

Cited by 113 publications

(94 citation statements)

References 36 publications

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“…Gold catalysts can be deactivated on-line by particle size agglomeration [3], carbonate formation and build up [4], as well as removal of hydroxyl groups from active sites [5]. Based on the previous infrared study from our group, we have agreed with some of the literature data that suggest the negative effect of carbonate species on the surface of the working catalyst [6].…”

Section: Introductionsupporting

confidence: 86%

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

et al. 2009

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In a study of the phenomenon of catalyst deactivation during storage, Au/TiO 2 catalyst was stored under various conditions, viz. vacuum, nitrogen, air, refrigeration, dark, and light, and tested for CO oxidation activity at regular intervals. The data shows that the catalyst deactivates under all the storage conditions over 12 months and that storage in vacuum significantly enhances the rate and extent of deactivation. Storage in light accelerates the deactivation. The catalyst appears to deactivate through a combination of Au(III) reduction, Au nanoparticle agglomeration, loss of surface hydroxyl groups, loss of surface moisture, and accumulation of surface carbonates and formates. The rate and extent of catalyst deactivation can be limited by storing the catalyst in the dark at sub ambient temperature (refrigerator) and under inert atmosphere.

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Section: Introductionsupporting

confidence: 86%

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

et al. 2009

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“…Some researchers propose that bicarbonates [76][77][78], hydroxycarbonyls [71,79], and formates [11,79] are important CO oxidation intermediates. Others believe that carbonates are inert spectators to the catalysis [29,30,77,80].…”

Section: Loss Of Active Sites and Carbonates Buildupmentioning

confidence: 99%

CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

Lopez

Powell

Panthi

et al. 2013

Journal of Catalysis

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a b s t r a c tA commercially available Au/TiO 2 catalyst was subjected to a variety of thermal treatments in order to understand how variations in catalyst pretreatment procedures might affect CO oxidation catalysis. Catalytic activity was found to be inversely correlated to the temperature of the pretreatment. Infrared spectroscopy of adsorbed CO experiments, followed by a Temkin analysis of the data, indicated that the thermal treatments caused essentially no changes to the electronics of the Au particles; this, and a series of catalysis control experiments, and previous transmission electron microscopy (TEM) studies ruled out particle growth as a contributing factor to the activity loss. Fourier transform infrared (FTIR) spectroscopy showed that pretreating the catalyst results in water desorption from the surface, but the observable water loss was similar for all the treatments and could not be correlated with catalytic activity. A Michaelis-Menten kinetic treatment indicated that the main reason for deactivation is a loss in the number of active sites with little changes in their intrinsic activity. In situ FTIR experiments during CO oxidation showed extensive buildup of carbonate-like surface species when the pretreated catalysts were contacted with the feed gas. A semi-quantitative infrared spectroscopy method was developed for comparing the amount of carbonates present on each catalyst; results from these experiments showed a strong correlation between the steady-state catalytic activity and amount of surface carbonates generated during the initial moments of catalysis. Further, this experimental protocol was used to show that the carbonates reside on the titania support rather than on the Au, as there was no evidence that they poison Au-CO binding sites. The role of the carbonates in the reaction scheme, their potential role in catalyst deactivation, and the role of surface hydroxyls and water are discussed.

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“…However, not all of these surface species are considered poisons to the CO oxidation reaction. Bicarbonates [14,15], hydroxycarbonyl [3] and formates [16] for example have been reported to be the reaction intermediates, hence their formation are important for high activity of the catalyst, while the presence of carbonates [15,16] deactivates the catalysts by blocking the active sites for CO adsorption. Catalysts deactivated by these species, especially carbonates can be regenerated by the presence of water which transforms the species into less stable bicarbonates which are easily decomposed into CO 2 [14].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the active site and the mode of Au/TiO2 catalyst deactivation using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)

et al. 2010

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CO is a useful probe in the characterization of surface properties of both metal and metal oxide via adsorption. Adsorption of CO was used to monitor the possible active site of an Au/TiO 2 catalyst for the CO oxidation reaction. CO adsorption on the reduced catalyst results in the band at 2104 cm -1 indicative of Au 0 . During the reaction (in the presence of both CO and O 2 present) the band is shifted to higher wave numbers indicating non-competitive adsorption on the surface of Au species. This study also reveals the relationship between the presence of CO (in the absence of oxygen) and the build-up of surface species such as bicarbonates, formates and carbonate species which decreases the activity of the catalyst. The presence of both the reduced and the cationic species of Au seem to be requirement for the activity of the catalyst.

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Influence of CO2 and H2 on the low-temperature water–gas shift reaction on Au/CeO2 catalysts in idealized and realistic reformate

Cited by 113 publications

References 36 publications

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

Investigation of the active site and the mode of Au/TiO2 catalyst deactivation using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)

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