Activity, stability, and deactivation behavior of supported Au/TiO2 catalysts in the CO oxidation and preferential CO oxidation reaction at elevated temperatures

Denkwitz, Y.; Schumacher, B.; Kučerová, Gabriela; Behm, R. Jürgen

doi:10.1016/j.jcat.2009.07.018

Cited by 112 publications

(116 citation statements)

References 45 publications

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“…These peaks appear essentially immediately upon introducing the reactant feed to the catalyst and are assigned to carbonate species on the catalyst surface [31,36,63]. The buildup of carbonates on Au/TiO 2 catalysts during CO oxidation has been previously reported in the literature [29,31], and bands at 1537 Scheme 1.…”

mentioning

confidence: 61%

“…Previous studies have correlated carbonates formation with catalytic activity, pretreatment conditions [23,73], presence of moisture in the gas [10,16], and reaction temperature [74]. Carbonates have also been shown to be decomposed in the presence of water [20], in the presence of H 2 [75], and during CO oxidation reaction at high temperatures [25,63].…”

Section: Loss Of Active Sites and Carbonates Buildupmentioning

confidence: 99%

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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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mentioning

confidence: 61%

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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“…The results of additional measurements with different CO/H 2 ratios during the CO/H 2 /Ar pulses, where the amount of CO molecules per pulse was kept constant at 3ˆ10 15 by H2 during these pulses, and also the quantitative evaluation of all CO/H2/Ar pulses could not resolve significant H2 consumption. From previous TAP reactor studies on Au/TiO2 as well as on Au/CeO2 it is already known that the efficiency of H2 for active oxygen removal is considerably lower compared to CO [35,42].…”

Section: Active Oxygen Removal By Co and Hmentioning

confidence: 99%

Competition of CO and H2 for Active Oxygen Species during the Preferential CO Oxidation (PROX) on Au/TiO2 Catalysts

2016

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Aiming at an improved mechanistic understanding of the preferential oxidation of CO on supported Au catalysts, we have investigated the competition between CO and H 2 for stable, active oxygen (O act ) species on a Au/TiO 2 catalyst during the simultaneous exposure to CO and H 2 with various CO/H 2 ratios at 80˝C and 400˝C by quantitative temporal analysis of products (TAP) reactor measurements. It is demonstrated that, at both higher and lower temperature, the maximum amount of active oxygen removal is (i) independent of the CO/H 2 ratio and (ii) identical to the amount of active oxygen removal by CO or H 2 alone. Hence, under preferential CO oxidation (PROX) reaction conditions, in the simultaneous presence of CO and H 2 , CO and H 2 compete for the same active oxygen species. In addition, also the dependency of the selectivity towards CO oxidation on the CO/H 2 ratio was evaluated from these measurements. Consequences of these findings on the mechanistic understanding of the PROX reaction on Au/TiO 2 will be discussed.

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“…Due to its superior activity on CO oxidation at low temperature [6][7][8], Au catalyst is expected as an excellent candidate for environmental protection [9][10][11][12], such as indoor air purification and canister respirators. Unfortunately, the practical applications of Au catalyst still remain a big problem because it shows a gradual deactivation with time on stream (TOS) [13][14][15]. Currently, agglomeration of Au particles and accumulation of carbonate species on catalyst surface are generally considered as the two major reasons for the deactivation phenomenon [16,17].…”

Section: Introductionmentioning

confidence: 99%

In-situ regeneration of Au nanocatalysts by atmospheric-pressure air plasma: Significant contribution of water vapor

Zhu

Liu

et al. 2015

Applied Catalysis B: Environmental

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Activity, stability, and deactivation behavior of supported Au/TiO2 catalysts in the CO oxidation and preferential CO oxidation reaction at elevated temperatures

Cited by 112 publications

References 45 publications

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

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

Competition of CO and H2 for Active Oxygen Species during the Preferential CO Oxidation (PROX) on Au/TiO2 Catalysts

In-situ regeneration of Au nanocatalysts by atmospheric-pressure air plasma: Significant contribution of water vapor

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