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The LEV II and EURO V legislation in 2007/2008 require a high conversion level for nitrogen oxides to meet the emission levels for diesel SUVs and trucks. Therefore, U.S. and European truck manufacturers are considering the introduction of urea SCR systems no later than model year 2005. The current SCR catalysts are based mainly on systems derived from stationary power plant applications. Therefore, improved washcoat based monolith catalysts were developed using standard types of formulations. These catalysts achieved high conversion levels similar to extruded systems in passenger car and truck test cycles. However, to meet further tightening of standards, a new class of catalysts was developed. These advanced type of catalytic coatings proved to be equivalent or even better than standard washcoat formulations. Results will be shown from ESC, MVEG and US-FTP 75 tests to illustrate the progress in catalyst design for urea SCR.

1 In this paper results obtained with different particulate matter (PM) reduction technologies are presented. Diesel oxidation catalysts (DOC) are well known as a reliable PM reduction technology which can efficiently remove the soluble organic fraction (SOF) but which has no effect on the solid particles in PM. A drawback is that in combination with high sulfur fuel, oxidation of SO2 to SO3 by the DOC can occur, resulting in an increase of PM emissions. An alternative technology that is proven to significantly reduce soot emissions comprises diesel particulate wall-flow filters. High filtration efficiencies of up to 90% and beyond are feasible. The main obstacle is the combustion of the trapped soot. As shown in this paper, the application of a catalyst coating to the filter aids the filter regeneration by lowering the balance-point temperature. The main disadvantages of wall-flow filters are an increase in back-pressure and possible plugging caused by oil-ash accumulations.

The trend towards lower exhaust gas temperatures related to the introduction of modern, highly efficient diesel engines for passenger cars in conjunction with new legislative emission regulations will require the development of amended catalyst formulations. Not only excellent performance for carbon monoxide(CO), gaseous hydrocarbons (HC) and diesel particulates is desired but also the capability to additionally reduce nitrogen oxide (NOx) under lean conditions. Generally, as for the latter a passive system, i.e. without addition of secondary fuel, is most wanted but also an active system, i.e. with hydrocarbon enrichment before catalyst, could be successful provided the penalties in fuel consumption can be kept low. The present paper illustrates further progress in the area of diesel catalysts for passenger cars and introduces a novel washcoat formulation comprising zeolites as hydrocarbon adsorption components.

Zirconium dioxide (zirconia) is a well-known material often being a major component in the washcoat systems of three-way catalysts (TWC) and diesel oxidation catalysts. One important characteristic of zirconia containing washcoats is an improved aging stability which is required to meet the more and more stringent emission standards. In the last few years the utilization of zirconia became even more important - especially for high sophisticated three-way washcoat systems. This was due to the development of high temperature stable oxygen storage components, containing cerium dioxide (ceria) in combination with different other oxides - one very promising candidate being zirconia. In the present work the results of a research program are discussed, focusing on the influence of zirconia in combination with ceria and additional rare earth promoters on the stability of the oxygen storage characteristics.

This paper describes the function and application of the preoxidation, hydrolysis and SCR catalysts individually and as a combined system for urea SCR both in model gas and engine bench tests. Using the basic system and a non-optimized urea injection strategy 45% NOx conversion was achieved in the ESC engine test. Adding a preoxidation catalyst significantly improved the NOx conversion in the low temperature region of the engine mapping. NOx conversions over 75% can be achieved in the ESC test using this improved system. With a 50% reduced SCR catalyst volume still a NOx conversion of over 65% could be achieved. Tests after 200 hours engine aging show that the activity of the system is stable.

The following paper highlights the results of a vehicle emission improvement program with emphasis on two main points: In the initial phase, various combinations of Pd and Pt-based three-way catalyst technologies were evaluated on a TLEV and a LEV calibrated vehicle in order to generate ULEV exhaust gas levels. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and a newly developed Pt-based technology. A combination of the Pd- and Pt-based technologies was able to meet the ULEV and part of the ULEV II regulations in the test vehicle after a catalyst aging cycle that resembles 50,000 miles of vehicle driving. In the later phase, a mathematical algorithm based on the original TLEV and LEV vehicle data was developed in order to conduct computer modeling of the exhaust gas aftertreatment system. This algorithm described the kinetic behavior of the individual catalysts over a broad range of reaction conditions.