Three-Way Catalyst Response to Transients

Schlatter, James C.; Mitchell, P. J.

doi:10.1021/i360075a002

Cited by 138 publications

(35 citation statements)

References 7 publications

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“…According to "ndings from other research works, this reaction can be catalyzed by Rh or Pd, providing that the catalyst surface has undergone some extent of oxidation (Schlatter and Mitchell, 1980;Herz and Sell, 1985;Dictor, 1987;Barbier and Duprez, 1992). The reversible oxidation}reduction process of the active catalyst is taken into account in the mathematical model by a submodel for the computation of active metal oxidation state.…”

Section: Rh Redox Submodelmentioning

confidence: 99%

Modeling dynamic phenomena in 3-way catalytic converters

Koltsakis

Stamatelos

1999

Chemical Engineering Science

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Mathematical modeling of 3-way catalytic converter (3WCC) operation is increasingly employed in automotive catalyst and converter systems optimization. The majority of the models employed in this direction employ a &quasi-steady' approach in the reaction kinetics computations. This approach is useful in predicting real-world performance of the catalyst. However, certain improvements, that are produced by the application of specially tuned redox oscillations, can not be predicted. This paper presents an approach embodying certain types of dynamic phenomena into an existing 3-WCC quasi-steady model. The dynamic model developed according to this approach is validated against literature data and results from experimental investigations. It is con"rmed, that the catalyst behavior under dynamic exhaust composition conditions signi"cantly di!ers from what is predicted under the quasi-steady-state assumption. More speci"cally, oxygen storage and the transient character of water gas shift reaction are shown to a!ect dynamic behavior. The results of this investigation encourage further application of mathematical modeling in areas like lambda control strategy optimization, which lied beyond the scope of traditional 3WCC models.

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Section: Rh Redox Submodelmentioning

confidence: 99%

Modeling dynamic phenomena in 3-way catalytic converters

Koltsakis

Stamatelos

1999

Chemical Engineering Science

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“…In fact, WGS activity is one of the main functions of ceria in the automobile three-way catalyst [15][16][17][18]. Cerium oxide-based WGS catalysts have attracted increasing attention primarily because of the high oxygen-storage capacity of ceria and modified ceria [19].…”

Section: Introductionmentioning

confidence: 99%

Low-temperature water-gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts

Flytzani‐Stephanopoulos

2000

Applied Catalysis B: Environmental

768

405

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In this paper we report on the activity of Cu-and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS). Bulk catalysts were prepared in nanocrystalline form by the urea co-precipitation-gelation method. Lanthanum dopant (10 at.%) was used as a structural stabilizer of ceria, while the content of Cu or Ni was in the range of 5-15 at.% (2-8 wt.%). At low metal loadings, Cu or Ni were present in the form of highly dispersed oxide clusters, while at high loadings, clusters as well as particles of CuO or NiO (>10 nm in size) were present on ceria. Both Cu and Ni increased the reducibility of ceria, as evidenced by H 2 -TPR experiments. The WGS reaction activity of Ce(La)O x was increased significantly by addition of a small amount (2 wt.%) of Cu or Ni. The catalysts were not activated prior to testing. Steady-state WGS kinetics were measured over the temperature range of 175-300 and 250-300 • C, respectively, for Cu-and Ni-Ce(La)O x . The activation energy of the reaction over Ce(La)O x was 58.5 kJ/mol, while it was 38.2 and 30.4 kJ/mol, respectively, over the 5 at.% Ni-Ce(La)O x and 5 at.% Cu-Ce(La)O x catalysts in CO-rich conditions. A co-operative redox reaction mechanism, involving oxidation of CO adsorbed on the metal cluster by oxygen supplied to the metal interface by ceria, followed by H 2 O capping the oxygen vacancy on ceria, was used to fit the kinetics. Parametric studies were mainly performed with the 5 at.% Cu-(La)O x catalyst. Notably, this material requires no activation and retains high WGS activity and stability at temperatures up to 600 • C.

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“…Cerium has been added to the catalyst to try to retain oxygen and keep the rate up during the part of the cycle during which there is insufficient gaseous oxygen for complete conversion. As shown, Schlatter and Mitchell (39) found the Cecontaining catalyst superior, but the explanation for its behavior is more complicated than simple oxygen storage.…”

Section: Tioned There Is a Convenient Directory Of Common Responses mentioning

confidence: 97%

“…The net result is as if the surface were more equally covered with oxygen and carbon monoxide with a Langmuir-Hinschelwood rate equation: r = k (CO a d s )(°ads)" Figure 11 shows the effect on CO conversion (oxidation) over two Rh/Al 2 Û3 catalysts of cycling at 550°C as studied by Schlatter and Mitchell (39). Steady state operation (high frequency) gives complete conversion of a stoichiometric reactant mixture, and cycling around this steady state ratio must give a lower average conversion.…”

Section: Tioned There Is a Convenient Directory Of Common Responses mentioning

confidence: 99%

Understanding Heterogeneous Catalysis Through the Transient Method

Bennett

1982

ACS Symposium Series

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Although catalysis can be understood through steady-state ex periments, it seems clear that transient experiments will usually furnish much additional information. Often steady-state data can be explained by a number of different models, but the results of transient experiments are usually so rich that only a detailed, complex model will come close to explaining the results. These ideas have long been applied in other fields, but in heterogeneous catalysis they have come into acceptance only during the last 15 years or so. Pioneering experiments were done by Wagner (1) in 1938, and Tamaru (2)

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Three-Way Catalyst Response to Transients

Cited by 138 publications

References 7 publications

Modeling dynamic phenomena in 3-way catalytic converters

Modeling dynamic phenomena in 3-way catalytic converters

Low-temperature water-gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts

Understanding Heterogeneous Catalysis Through the Transient Method

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