Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies Pascal Granger* and Vasile I. Parvulescu* Unit e de Catalyse et de Chimie du Solide, UMR CNRS 8181, University of Lille 1, 59655 Villeneuve d’Ascq, France Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, Romania, 412 Regina Elisabeta Boulevard, Bucharest 030016, Romania

Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies

The use of structured catalysts in the chemical industry has been considered for years. Conventional fixed-bed reactors have some obvious disadvantages such as maldistributions of various kinds (including a nonuniform access of reactants to the catalytic surface), high pressure drop in the bed, etc. Structured catalysts are promising as far as elimination of these setbacks is concerned. Two basic kinds of structured catalysts can be distinguished: Structural packings covered with catalytically active material, similar in design to those used in distillation and absorption columns and/or static mixers. Good examples of catalysts of this kind are those offered by Sulzer, clearly developed by Sulzer column packings and static mixers. As in packed beds, there is an intensive radial convective mass transport over the entire cross-section of these packings. Structural packing catalysts and the reactors containing them are, however, not within the scope of this review. Monolithic catalysts are continuou...

Monoliths in Heterogeneous Catalysis

Catalytic combustion (review)

The diesel oxidation catalyst (DOC) has been part of diesel exhaust systems since regulations were introduced to limit the amount of harmful emissions released to the environment from diesel engines. The DOC primary functions are oxidation of CO, unburned hydrocarbons, and NO, while active hydrocarbon oxidation can also be used to generate exotherms required for downstream components. This review will describe work that has attempted to understand the reactions, both desired and undesired, that occur over the catalyst. First, the history, configuration, and components of the DOC will be discussed, followed by in-depth coverage of the fundamental reactions that occur over a DOC, including reaction mechanisms, reaction inhibition, and other reactivity effects. Finally, DOC deactivation mechanisms and their effects on the DOC are described. While there is a lot of research literature regarding Pt- and Pd-based catalysts for many different reaction schemes, this review tries to highlight work most relevant to...

Diesel Oxidation Catalysts

The need for reliable 3-way catalytic converter modeling in the design of demanding exhaust systems for low-emitting vehicles has been widely recognised. Although a number of related models have been presented in the literature, the efficient performance in actual 3-way applications requires further development and validation. The major difficulties posed in such modeling efforts arise from the complexities in the reaction schemes and the respective rate expressions for the multitude of currently used catalytic formulations. This paper presents a two-dimensional catalytic converter model, featuring a number of innovations regarding the catalyst transient behaviour, the reaction kinetics and the solution procedure. The oxygen storage submodel presented is capable of accounting for the redox and temperature dependence of the oxygen availability under transient operation. The redox sensitivity of the reaction scheme gives a clearer insight in the ‘lambda-window’ behavior of 3-way catalysts. The application range of the model and the expected accuracy levels in the most common engineering problems are discussed. It is concluded, that although the task of predicting emissions over random driving scenarios is quite demanding in both chemical kinetics and inlet conditions data, most optimization applications may be sufficiently handled with existing kinetic expression information.

Development and application range of mathematical models for 3-way catalytic converters

Transients of monolithic catalytic converters. Response to step changes in feedstream temperature as related to controlling automobile emissions

Developpement d'un modele decrivant le profil de penetration du poison et le taux de conversion d'un monolithe en fonction du temps d'exposition au poison

James C. Cavendish

Papers

Transients of monolithic catalytic converters. Response to step changes in feedstream temperature as related to controlling automobile emissions

Design aspects of poison-resistant automobile monolithic catalysts