Kinetics of the Selective CO Oxidation in H2-Rich Gas on Pt/Al2O3

Kahlich, M.J.; Gasteiger, Hubert A.; Behm, R. Jürgen

doi:10.1006/jcat.1997.1781

Cited by 463 publications

(323 citation statements)

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“…473 K) was observed in absence of hydrogen. A similar trend has been observed by Kahlich et al [60] on a 0.5% Pt/␥-Al 2 O 3 catalyst. The decrease in CO conversion (in presence of hydrogen) with increasing temperature was attributed to a greater contribution from the competitive H 2 oxidation at higher reaction temperatures.…”

Section: Preferential Oxidation Of Co (Prox)supporting

confidence: 88%

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CO-free fuel processing for fuel cell applications

2003

Fuel and Energy Abstracts

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In view of the stringent CO intolerance of the state-of-the-art proton exchange membrane (PEM) fuel cells, it is desirable to explore CO-free fuel processing alternatives. In recent years, step-wise reforming of hydrocarbons has been proposed for production of CO-free hydrogen for fuel cell applications. The decomposition of hydrocarbons (first step of the step-wise reforming process) has been extensively investigated. Both steam and air have been employed for catalyst regeneration in the second step of the process. Since, PEM is poisoned by very low (ppm) levels of CO, it is essential to eliminate even trace amounts of CO from the reformate stream. Preferential oxidation of CO (PROX) is considered to be a promising method for trace CO clean up. Related studies along with a discussion of catalytic ammonia decomposition (for applications in alkaline fuel cells) will be included in this review.

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Section: Preferential Oxidation Of Co (Prox)supporting

confidence: 88%

“…The PROX reaction has been extensively investigated on Pt/Al 2 O 3 catalysts [56][57][58][59][60][61]. Oh and Sinketvitch [59] observed a maximum in CO conversion with temperature on 0.5% Pt/Al 2 O 3 at ca.…”

Section: Preferential Oxidation Of Co (Prox)mentioning

confidence: 99%

CO-free fuel processing for fuel cell applications

2003

Fuel and Energy Abstracts

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“…At higher temperatures (T>150°C) adsorption rates in the absence of hydrogen are higher than those in excess of hydrogen, which may be related to the observed CO decomposition, which activity becomes more intense at temperatures higher than 150°C. Moreover, the satisfactory selectivity of Au/␥-Al 2 O 3 for SCO at low temperatures can be further explained from the fact that the rate of adsorption is obviously higher in excess of hydrogen, due to the well known blocking or poisoning action of CO, which prevents the dissociative adsorption of other gases, such as O 2 and H 2 (6,7).…”

Section: Figurementioning

confidence: 99%

“…Carbon monoxide's desorption is considered as the determining step for the catalytic oxidation of CO on group VIII (Pt, Rh, Pd etc.) noble metal catalysts (6,7,25). However, the beneficial influence of hydrogen on CO desorption is not determining for the low-temperature CO oxidation activity of gold, since it is generally assumed that the mild bonding character of gold is the basis of Au-based catalysts in oxidation processes at low temperatures (19,20).…”

Section: Figurementioning

confidence: 99%

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On the mechanism of selective CO oxidation on nanosized Auγ-Al2O3 catalysts

et al. 2006

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Nanometer-sized gold particles on oxide supports are efficient catalysts for the selective catalytic oxidation (SCO) of carbon monoxide under conditions compatible with the operation of PEM fuel cells. Nanosized Au/␥-Al 2 O 3 catalysts are able to oxidize CO between 20 and 70°C in an atmosphere of hydrogen combining high CO conversion and satisfactory selectivity to CO 2 (1). It is generally agreed that the catalytic activity of gold depends on the size of the gold particles, but the nature of support material, the preparation method, the activation procedure have also been suggested to play a key role (2). Sites at the gold support interface have also been claimed to be responsible for the activity in CO oxidation (3). Strain in the Au particles due to the mismatch of the lattices at the interface with the support (4) and the effect of low-coordinated sites and roughness (4) have also been suggested as important factors for high activity. The most important effect, concerning the catalytic activity of gold nanoparticles for low temperature oxidation of CO is related to the availability of many low-coordinated gold atoms on the small particles (5). Effects related to the interaction with the support may also contribute, but to a considerably smaller extent (5).CO oxidation over group VIII noble metals is the most studied catalytic reaction. However, selective oxidation of CO in hydrogen-rich conditions is not as well studied (6,7). CO (reactant) and CO 2 (product) sorption processes are fundamental elementary steps for SCO and moreover, the effect of hydrogen on their sorption over supported Au catalysts remains a subject of significant interest.Among the various supported Au catalysts, Au/Al 2 O 3 is perhaps one that has shown the widest variation for CO oxidation, ranging from being very inactive to practically as active as Au/TiO 2 (8). Compared to Au/␥-Al 2 O 3 , multicomponent gold-based catalysts also supported on ␥-Al 2 O 3 and combined with common metal oxides, such as: MnO x , MgO, FeO x (9,10) as well as gold catalysts supported on other materials such as Au/TiO 2 (11) and Au/FeO x (11,12) have been found to exhibit even more promising commercial performance for the SCO reaction. However, based on its simplicity, a well-studied Au/␥-Al 2 O 3 catalyst (1,9) has been utilized in the present work as model system, in order to gain fundamental information on the catalytic behaviour of gold nanoparticles and identify the active sites on Au/␥-Al 2 O 3 .In this paper, new findings which offer further information concerning the mechanism of CO preferential oxidation over nanosized Au are presented. The first finding concerns CO 2 formation in the absence of oxygen and hydrogen both in bare ␥-Al 2 O 3 as well as in Au/␥-Al 2 O 3 (called as CO decomposition). At high temperatures (>200 °C) in excess of H 2 , over the Au/␥-Al 2 O 3 catalyst, reversed water gas shift (RWGS) reaction results in CO 2 consumption towards CO and H 2 O formation. Finally, the kinetic measurements of the present work indicate that hydrog...

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PROXcatalysts

Shore¹,

Farrauto²

2010

Handbook of Fuel Cells

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The proton exchange membrane fuel cell uses a Pt‐based catalytic anode and operates at about 80 °C. The hydrogen that is oxidized at the fuel cell anode can be obtained from reforming a hydrocarbon fuel. Depending on the reforming model, the hydrogen stream may initially contain almost 10% CO (dry basis). Since carbon monoxide adsorbs strongly on precious metals, one of the most important requirements for successful operation of this fuel cell is that the CO concentration be reduced to <10 ppm (99.99% conversion) to protect the Pt anode from CO poisoning and deactivation. The task of CO removal is a multi‐stage process within the fuel reformer. The primary CO converter is a water gas shift (WGS) reactor, where the CO is reacted with water to yield equimolar concentrations of CO 2 and H 2 . Because of both thermodynamic and kinetic limitations, WGS normally yields a stream with 0.2–0.5% CO. The most effective mechanism for further CO removal is oxidation with air injection. Because of the very high ratio of hydrogen to carbon monoxide (>100 : 1), the catalyst needs to be highly selective. Therefore, the process is called selective oxidation or preferential oxidation (PROX). The objective of the PROX reaction is high CO conversion to CO 2 without excessive hydrogen oxidation (to water). This article discusses the details of the PROX reaction, catalytic materials currently being investigated and alternative approaches to CO removal.

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Kinetics of the Selective CO Oxidation in H2-Rich Gas on Pt/Al2O3

Cited by 463 publications

References 45 publications

CO-free fuel processing for fuel cell applications

CO-free fuel processing for fuel cell applications

On the mechanism of selective CO oxidation on nanosized Auγ-Al2O3 catalysts

PROXcatalysts

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