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In recent years, automobile emission limits have been tightened world wide. PZEV (Partial Zero Emission Vehicle) which is the most stringent regulation has been imposed in California. To meet the strict PZEV regulation, automotive manufacturers are requesting the catalyst system to have quick light-off characteristics and excellent steady state performance with limited precious group metals (PGM) usage due to the strong price pressure. Moreover, the catalyst can not use high cell density substrate for increasing geometric surface area and reducing heat mass, since the backpressure of exhaust system must be decreased to improve the vehicle power for the PZEV application. This paper will present an efficient catalyst formulation that has been designed to maximize the performance with considerably reduce PGM loading. The catalyst washcoat has been optimized by improving the catalyst geometric surface area, gas diffusivity and thermal mass.

For global environmental protection and resource conservation, Honda has developed a low precious-metal perovskite catalyst system in response to LEV-II, which achieves both low emissions and a reduction in the amount of precious metal used. The amount of precious metals used in the catalyst, per vehicle, is expected to be 50% less than in conventional systems. This system is comprised of an air-fuel ratio control system based on Honda's unique high-accuracy air-fuel control system, combined with a perovskite catalyst jointly developed with the US Company CSI. This system's performance is expected to reach the levels required by LEV-II regulations. Perovskite is a mix-metal oxide material that is widely used in general applications other than catalysts. However, it has not been widely used in automobile catalysts, because, in comparison with precious-metal catalysts, both the heat resistance and conversion efficiency during the warm-up process is reduced.

A two-brick gasoline engine aftertreatment system with advanced washcoat technology was developed for LEV2 PZEV2 legislation, and its application to the upcoming LEV3 SULEV30 emission standard was demonstrated. The system was comprised of 1) a palladium only catalyst in the close coupled position with improved catalytic performance and high phosphorus poisoning resistance compared with 09MY technology, and 2) an underfloor palladium rhodium catalyst technology in which the nitric oxides (NOx) reduction activity was enhanced by preventing the deactivation of rhodium under rich conditions. As a result, the palladium only + palladium rhodium catalysts system met the LEV2 PZEV standard with three quarters of the PGM and half the rhodium of the system used on the Honda 09MY Accord vehicle. The system was also demonstrated to meet the LEV3 SULEV30 standard with some margin.

With a view to application of model base development to exhaust catalyst design, a numerical model for catalytic reaction was formulated so as to be able to predict tailpipe emission during test mode running. In order to grasp the catalytic reaction characteristics, catalyst characteristics test using catalyst test pieces and synthetic gas was conducted and the basic reaction that takes place inside the exhaust catalyst was modeled by employing the 3 overall reaction models: Arrhenius model, competitive adsorption model, and adsorption model. By using the formulated numerical catalyst model, tailpipe emission estimation for a gasoline engine vehicle was carried out, and an estimated accuracy of within ±10% error range from the actual measurement was realized for all of CO, HC, and NO.

The reduction of NOx in exhaust gas has been a major challenge in diesel engine development. For the NOx reduction issues, a new Lean NOx Catalyst (LNC) aftertreatment system has been developed by Honda. A feature of the LNC system is the method that is used to reduce NOx through an NH₃-Selective Catalytic Reduction (NH₃-SCR). In an LNC system NOx is adsorbed at lean conditions, then converted to NH₃ at rich conditions and subsequently reduced in the next lean phase. In recent years, as the efficiency of the diesel engine has improved, the exhaust gas temperatures have been reduced gradually. Therefore, the aftertreatment system needs to be able to purify NOx at lower temperatures. The development of a new LNC which has a high activity at low temperature has been carried out. For the improvement of the LNC three material improvements were developed. The first of these was the development of a NOx adsorbent which is matching the targeted exhaust gas temperatures.

Recently, automotive emission regulations are being further tightened, such as the Tier III/LEV III in the U.S. As a result, reducing cost of after-treatment systems to meet these strict regulations has become an urgent issue, and then the demand for high-precision air-fuel ratio (A/F) control which can achieve this cost reduction is high [1]. On the other hand, in order to meet rapidly changing market needs, it is becoming difficult to keep enough development periods that enable sufficient calibration by trial-and-error, such as feedback-gain calibration. This leads to an increase in three-way catalytic converter costs in some cases. For these reasons, it is necessary to construct control system that can make full use of hardware capabilities, can shorten development periods regardless of the skill level of engineers.

Regulations that limit emissions of pollutants from gasoline-powered cars and trucks continue to tighten. More than 75% of emissions through an FTP-75 regulatory test are released in the first few seconds after cold-start. A factor that controls the time to catalytic light-off is the heat capacity of the catalytic converter substrate. Historically, substrates with thinner walls and lower heat capacity have been developed to improve cold-start performance. Another approach is to increase porosity of the substrate. A new material and process technology has been developed to significantly raise the porosity of thin wall substrates (2-3 mil) from 27-35% to 55% while maintaining strength. The heat capacity of the material is 30-38% lower than existing substrates. The reduction in substrate heat capacity enables faster thermal response and lower tailpipe emissions. The reliance on costly precious metals in the washcoat is demonstrated to be lessened.

With the increasing number of automobiles, the worldwide problem of air pollution is becoming more serious. The necessity of reducing tail-pipe emissions is as high as ever, and in countries all over the world the regulations are becoming stricter. The emissions at times such as after engine cold start, when the three-way catalyst (TWC) has not warmed up, accounts for the majority of the emissions of these pollutants from vehicles. This is caused by the characteristic of the TWC that if a specific temperature is not exceeded, TWC cannot purify the emissions. In other words, if the catalyst could be warmed up at an early stage after engine start, this would provide a major contribution to reducing the emissions. Therefore, this research is focused on the substrate weight and investigated carrying out major weight reduction by making the porosity of the substrate larger than that of conventional products.

This research is aimed at development of the catalyst for gasoline automobiles which uses only palladium (Pd) among platinum group metals (PGMs). And the conformity emission category aimed at LEV III-SULEV30. For evaluation, the improvement effect was verified for 2013 model year (MY) ACCORD (LEV II-SULEV) as the reference. As compared with Pd-rhodium (Rh) catalyst, a Pd-only catalyst had the low purification performance of nitrogen oxides (NOx), and there was a problem in the drop in dispersion of Pd by sintering, and phosphorus (P) poisoning.