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Several diesel powered passenger car manufacturers in the European Union announced recently the future use of catalysed diesel particulate filter systems on their vehicles. The filtration of the exhaust gas is being worked on since several years. Different filter materials and filter designs proved their ability to achieve high filtration efficiencies over the lifetime of the vehicle. The major technological challenge is the periodic regeneration of the filters loaded with the retained diesel particulates. In order to promote filter regeneration, catalytic activation of the accumulated soot is advantageous. Therefore, the first serial application of diesel particulate filter system (diesel oxidation catalyst combined with an uncoated filter substrate) uses catalytically active fuel additives. These systems have been introduced about four years ago and proved to be a viable technology to clean the exhaust gas of passenger car diesel engines.

To meet future emission levels the industry is trying to reduce tailpipe emissions by both, engine measures and the development of novel aftertreatment concepts. The present study focuses on a joint development of aftertreatment concepts for gasoline engines that are optimized in terms of the exhaust system design, the catalyst technology and the system costs. The best performing system contains a close-coupled catalyst double brick arrangement using a new high thermal stable catalyst technology with low precious metal loading. This system also shows an increased tolerance against catalyst poisoning by engine oil.

India, as a major two and three wheeler production center in the world, is also leading with the stringent emission regulations for this segment of the vehicles. Emission legislations were introduced in 1991 and have been progressively tightened since 1996. The present legislations of 2.0 g/km CO, 2.0 g/km HC+ NOx for two wheelers and 4.0 g/km CO, 2.0 g/km HC+NOx for three wheelers, are being considered as the most stringent in the world. In addition, a voluntary emission warranty of 30,000 km by the manufacturers of two and three wheelers and a deterioration factor of 1.2 on the emission norms of the catalyst equipped vehicles, put an additional strain on the catalyst technologies, as well as on the overall vehicle systems. In order to meet these challenges, and with focus on the cost effective solutions required for developing countries like India, new advanced catalyst technologies have been developed with improved performance and even lower precious metal content.

Future three way catalyst systems are expected to consist of a relatively small start catalyst and a larger volume underfloor catalyst. The main role of the start catalyst is to provide rapid light off. For this purpose, the start catalyst requires relatively small volume with high precious metal loading. Computer simulation is employed to optimize the start catalyst volume with respect to light off performance and precious metal cost. The main role of the underfloor catalyst is NOx removal at elevated temperatures and high space velocities. Due to its large volume, substantial precious metal savings can be realized by the design of a low precious metal underfloor catalyst. The present study focuses on a systematic understanding of NOx breakthrough in three-way catalysts. Special emphasis is on the interaction of the catalyst and the engine management system, especially the lambda control.

Successful system integration of NOx storage catalyst properties into engine management functions implies a profound understanding of the catalyst's performance under transient exhaust gas conditions. During lean operating conditions, this technology achieves a high level of NOx conversion by storing nitrogen oxides reversibly as nitrates. Periodically, the engine control induces a switch to rich, i.e. to reducing conditions, leading to a regeneration of the NOx storage component. The present paper focuses on the investigations of the NOx storage as well as the regeneration process under the described transient reaction conditions for gasoline lean burn applications. In order to study the influence of NOx mass, of the amount of reduction agent offered and of specific regeneration components, experiments were conducted by means of heated exhaust gas oxygen (HEGO) sensors on a model gas as well as an engine test bench.

The LEV II and SULEV/PZEV emission standards legislated by the US EPA and the Californian ARB will require continuous reduction in the vehicles' emission over the next several years. Similar requirements are under discussion in the European Union (EU) in the EU Stage V program. These future emission standards will require a more efficient after treatment device that exhibits high activity and excellent durabilty over an extended lifetime. The present study summarizes the findings of a joint development program targeting such demanding future emission challenges, which can only be met by a close and intensive co-operation of the individual expert teams. The use of active systems, e.g. HC-adsorber or electrically heated light-off catalysts, was not considered in this study. The following parameters were investigated in detail: The development of a high-tech three-way catalyst technology is described being tailored for applications on ultra thin wall ceramic substrates (UTWS).

This paper describes the results of a joint development program focussing on the introduction of the new generation of Pt/Rh-technology for current and future emission standards as a cost effective alternative to the in serial Pd/Rh based exhaust gas concepts. In the initial phase of the program combinations of Pd- and Pt-based three-way catalyst technologies were evaluated on vehicles equipped with a 8 cylinder engine. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and the new Pt/Rh technology in the underfloor position at lower precious metal loading. A combination of a close-coupled Pd/Rh technology and the new Pt/Rh in the underfloor position was able to meet the emission targets at significant lower costs of the system after a catalyst aging that resembles more than 100.000 km of vehicle German highway driving.

The future emission limits for gasoline fuelled passenger cars require more and more efficient exhaust gas aftertreatment devices - the catalytic converter being one essential part of the complex system design. The present paper summarizes the results of several basic research programs putting major emphasis on the application of highly sophisticated three-way catalyst technologies being taylored for the utilization on ultra thin-wall ceramic substrates. In the first part of the investigation the following effects were examined in detail: Different washcoat loadings at constant PGM-loadings Different volumes of catalysts for constant amounts of PGM and washcoat Similar washcoat technologies at different ratios of WC-loading to precious metal concentration in the washcoat.

World over, emission legislations are becoming stringent day by day. India too, is on the road map for more tough emission legislations. 2/3 Wheeler legislations in India are being considered as the most stringent in the world, where as, Passenger Car and light/heavy duty legislations are reaching Euro III and Euro IV limits in the near future. The present paper describes the system concepts to be followed to reach the emission targets, specially for Euro III and Euro IV for passenger cars. That includes necessity for using more advanced engine technologies such as Turbo Charging with Intercooling, EGR (cooled), Electronically Controlled Direct Injection, Common Rail / Pump - Nozzle systems. The new catalyst technologies required and developed for these applications are described. These technologies not only require to offer efficient emission reduction under fresh conditions, but need to meet the targeted results after long aging of over 80,000 km. The paper is divided in two parts.

World over, emission legislations are becoming stringent day by day. India too, is on the road map for more tough emission legislations. 2/3 Wheeler legislations in India are being considered as the most stringent in the world, where as, Passenger Car and light/heavy duty legislations are reaching Euro III and Euro IV limits in the near future. The present paper describes the system concepts to be followed to reach the emission targets, specially for Euro III and Euro IV for passenger cars. That includes necessity for using more advanced engine technologies such as Turbo Charging with Intercooling, EGR (cooled), Electronically Controlled Direct Injection, Common Rail / Pump - Nozzle systems. The new catalyst technologies required and developed for these applications are described. These technologies not only require to offer efficient emission reduction under fresh conditions, but need to meet the targeted results after long aging of over 80,000 km. The paper is divided in two parts.

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.

The present paper highlights the results of a development program focussing on Pt-based three-way catalysts. It is demonstrated that as compared to state-of-the-art Pt/Rh technologies the utilization of advanced washcoat raw materials, new processing methods as well as advanced washcoat systems dedicated to the individual precious metals (PGM) lead to novel catalyst technologies taking better advantage of the lead to novel catalyst technologies taking better advantage of the PGM properties. This yields substantial improvements regarding both aging stability and activity of the catalytic converters. Furthermore, based on the results of a PGM loading study, preferred PGM loadings and ratios were investigated in more detail. In summary, for different application examples it is documented that the newly developed Pt/Rh double layer catalyst is a technical and commercial alternative to the current Pd-based technologies also for high-demanding applications.

The present paper describes the results of a joint development program focussing on a system approach to meet the EURO IV emission standards for an upper class passenger car equipped with a newly developed high displacement gasoline engine. Based on the well known catalyst systems of recent V6- and V8-engines for the EURO III emission standards with a combination of close coupled catalysts and underfloor catalysts, the specific boundary conditions of an engine with an even larger engine displacement had to be considered. These boundary conditions consist of the space requirements in the engine compartment, the power/torque requirements and the cost requirements for the complete aftertreatment system. Theoretical studies and computer modeling showed essential improvements in catalyst performance by introducing thin wall substrates with low thermal inertia as well as high cell densities with increased geometric surface area.

To support the application and design of exhaust gas aftertreatment systems for gasoline fueled passenger cars based on hydrocarbon adsorber catalysts, a computer model was developed. This model is based on simplified, lumped kinetics for the adsorption and desorption of hydrocarbons and for the oxidation of CO and hydrocarbons. Also included in the model are convective transport of heat and mass in the gas phase, mass and heat transfer to the washcoat layer, and diffusion with reaction in the washcoat layer. The continuity equations for this model with the appropriate boundary conditions were solved for a single channel assuming adiabatic behavior. After validation of the prediction on experimental results, this model was used to perform a simple parametric study on the influence of inlet temperature,CO concentration, washcoat loading, adsorber content, and cell density on the HC emission.

The exhaust emissions of two and three wheelers contribute to a major extent to the pollution in urban areas of South East Asia and especially India. Most of this class of vehicles are equipped with 2 stroke engines, which operate constantly rich, - leading to high carbon monoxide and hydrocarbon emissions. On the other hand the NOx concentration in the exhaust gas is neglegible. In near future more stringent exhaust gas legislation get effective in a number of countries. Therefore catalytic aftertreatment devices are necessary to meet the emissions limits. Hot Tubes™ and/or monolith type catalysts can be applied. The high exhaust gas hydrocarbon concentrations lead to high exotherms on oxidation which drives the exhaust gas temperatures up to a range between 750 and 850°C. Therefore thermal ageing of the Hot Tubes™ and monolith type catalysts is severe. The design of advanced catalyst systems has to take this into account.

The exhaust emissions of two stroke vehicles like motorbikes and scooters contribute to the pollution in urban areas of developing countries in South East Asia and India to a major extent. But also in Japan and selected European countries exhaust gas limitations become effective from 10/1998 and 06/1999 for these vehicles. To control this emissions catalytic aftertreatment by Hot Tubes® and/or monolith type catalysts are applied. Due to the constant rich operation of the two-stroke engines, common design criteria for three-way catalysts fail. Extremely high exhaust gas hydrocarbon concentrations lead to high exotherms during oxidation which increases the exhaust gas temperature to a range between 800 and 900 °C. Furthermore the lack of oxygen limits the CO and HC oxidation under certain engine operation conditions. Therefore, water-gas shift and steam reforming reactions play an important part in catalytic aftertreatment of two-stroke exhausts.

In order to meet recent and future stringent hydrocarbon emission regulations of passenger cars, the use of Pd-containing catalysts is of growing interest. This is especially true for Pd/Rh and Pt/Pd/Rh catalysts. To optimize the function of the individual precious metals, most high-performance catalysts have a double layer configuration. This double layer avoids undesired interactions between Pd and Rh after reacting with exhaust gas at a high temperature level. Of course, these double layer technologies lead to a more complex capacity utilization coating process during the manufacture of the catalyst. The present work summarizes the results of a research program targeting the development of a high-performance single layer Pd/Rh catalyst technology. The starting point was the functional improvement of Pd and Rh only catalysts then subsequently combining the best of these technologies.

The present paper describes the results of a joint development program focussing on a system approach to meet the proposed EURO III and IV emission standards for a passenger car equipped with a 3.2 liter, 18 valve gasoline engine. Starting with the in-production configuration of a EURO II certified vehicle (model year 1997) the following improvement points were investigated in detail. By the introduction of a close-coupled catalyst in combination with engine measures to improve the catalyst light-off the proposed EURO III limits were met. The proposed EURO IV hurdle could be overcome by further using secondary air injection during cold-start in combination with an increased precious metal loading for the close-coupled catalyst.

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.

Catalyst applications for gasoline and diesel engine powered passenger cars and 2-stroke Two- and Three-wheelers are the main focus of this paper. Catalyst durability and deactivating effects are discussed in detail. Experiences on Indian conditions are also included.