Role of NO in inhibiting CO oxidation over alumina-supported rhodium

Oh, Se H.; Carpenter, Joyce

doi:10.1016/0021-9517(86)90234-4

Cited by 54 publications

(5 citation statements)

References 14 publications

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“…The reduction of NO by CO on rhodium surfaces in particular displays some chemical changes at the onset of the reaction that become evident by differences in rates of production of N 2 and CO 2 during the first few seconds of the process. Although there have already been a few reports on both the transient and the steady-state behavior of NO + CO and NO + H 2 mixtures on rhodium catalysts, − there have not been, to the best of our knowledge, any careful studies on the correlation between the two. The present report addresses this very issue, and relates the transient behavior to the knowledge previously acquired in our ongoing study on the details of the kinetics and mechanism of NO reduction on Rh(111) single crystals. − …”

Section: Introductionmentioning

confidence: 99%

Transient Kinetics during the Isothermal Reduction of NO by CO on Rh(111) As Studied with Effusive Collimated Molecular Beams

Gopinath

Zaera

2000

J. Phys. Chem. B

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The transient kinetics of the reaction between NO and CO on clean Rh(111) surfaces have been studied using molecular beams in conjunction with mass spectrometry detection. The changes in the partial pressures of the reactants (CO and NO) and products (N 2 and CO 2 ) as a function of time have been used as a measure of the evolution of the uptake and desorption rates, respectively, for temperatures between 350 and 1000 K and for NO:CO mixture ratios between 4:1 and 1:99. Post-mortem temperature programmed desorption (TPD) and CO titration experiments were also performed in order to estimate the surface coverages of atomic nitrogen and oxygen left on the Rh(111) surface by the gas mixture. Systematic variations were observed during the transition from the clean surface to the steady-state catalytic regime that correlate well with the overall reaction rates in the latter. Specifically, there is a time delay in the production of molecular nitrogen because of the need to build up a threshold atomic nitrogen coverage on the surface before the start of the desorption of N 2 . This atomic nitrogen coverage, as calculated by the time delay in the transient, corresponds to that estimated by TPD after the reaction, and displays a dependence on the NO:CO ratio in the reaction mixture, increasing at a given temperature as the beam becomes richer in CO. Initial sticking coefficients were also determined for both NO and CO in NO + CO mixtures as a function of surface temperature and beam composition. † Part of the special issue "Gabor Somorjai Festschrift".

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Section: Introductionmentioning

confidence: 99%

Transient Kinetics during the Isothermal Reduction of NO by CO on Rh(111) As Studied with Effusive Collimated Molecular Beams

Gopinath

Zaera

2000

J. Phys. Chem. B

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“…For reaction 2 (CO oxidation reaction), two species inhibition coefficients are included in the reaction rate formulation, CO self-inhibition and NO inhibition. CO self-inhibition effect is a known phenomenon [22] and is usually modeled by a second order inhibition factor [14,21]. NO competes for active Pd/Rh sites with O 2 and the competition has been modeled with a 0.7 order inhibition factor [14].…”

Section: Model Descriptionmentioning

confidence: 99%

Modeling of Three Way Catalyst Behavior Under Steady and Transient Operations in a Stoichiometric Natural Gas Fueled Engine

Wang¹,

Eggenschwiler²

2021

SAE Technical Paper Series

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Methane abatement in the exhaust gas of natural gas engines is much more challenging in respect to the oxidation of other higher order hydrocarbons. Under steady state λ sweep, the methane conversion efficiency is high at exact stoichiometric, and decreases steeply under both slightly rich and slightly lean conditions. Transient lean to rich transitions can improve methane conversion at the rich side. Previous experimental work has attributed the enhanced methane conversion to activation of methane steam reforming. The steam reforming rate, however, attenuates over time and the methane conversion rate gradually converges to the low steady state values. In this work, a reactor model is established to predict steady state and transient transition characteristics of a three-way catalyst (TWC) mounted in the exhaust of a natural gas heavy-duty engine. In total 17 global reactions are selected and implemented in the reactor model, including oxidation reactions, NO x related reactions, water gas shift and steam reforming, and ceria oxygen storage related reactions. Inhibition factors are introduced to model the competition of different species for active sites. To model the transient enhancement of methane conversion, an activation and deactivation mechanism of methane steam reforming based on active ceria sites is proposed and developed. Both lean to rich and rich to lean λ transitions are simulated and compared with engine experiment results. The proposed model captures key characteristic behaviors of the TWC in both steady state λ sweep and transient λ transitions. The results provide insights in TWC reaction mechanisms at near stoichiometric operation and can be used as a starting point to predict the effect of dedicated control strategies.

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“…Shelef et al found that the second reaction is predominant over a number of transition metal oxides and supported Pt [7]. Other authors proved that the NO addition to CO+O2 reduces drastically the rate of CO2 formation on Rh catalyst [8] and Pt supported catalyst [9].…”

Section: Introductionmentioning

confidence: 99%

Effect of Precious Metals on NO Reduction by CO in Oxidative Conditions

Akil¹,

Siffert²,

Piraúlt-Roy³

et al. 2020

Preprint

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Carbon dioxide has become a global challenge, where the emissions have become more than what could be handled. In this regard, conversion of CO2 to value added chemicals and thus recycling CO2 became a viable option. One of these options is the use of a process in strong development: oxycombustion. However, the gases resulting from this process contain some traces of impurities that can hinder the recovery of CO2 such as NO and CO. This work has therefore focused on the study of the reaction of NO reduction by CO in an oxidizing medium, using catalytic materials based on various supported noble metals. These materials were extensively characterized by a variety of methods including BET surface area measurements, hydrogen chemisorption, Transmission Electron Microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). The obtained results show that the catalytic behaviour of M/Al2O3 catalysts in CO oxidation and NO reduction with CO in oxidative conditions depends mainly on the nature of the metal. The best result for these both reactions is obtained with Pt/Al2O3 catalyst. The Pt nanoparticles existing in the metallic form (Pt°) showed by TPR could explain the activity.

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Role of NO in inhibiting CO oxidation over alumina-supported rhodium

Cited by 54 publications

References 14 publications

Transient Kinetics during the Isothermal Reduction of NO by CO on Rh(111) As Studied with Effusive Collimated Molecular Beams

Transient Kinetics during the Isothermal Reduction of NO by CO on Rh(111) As Studied with Effusive Collimated Molecular Beams

Modeling of Three Way Catalyst Behavior Under Steady and Transient Operations in a Stoichiometric Natural Gas Fueled Engine

Effect of Precious Metals on NO Reduction by CO in Oxidative Conditions

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