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Traditional approaches to pollution control have been to develop benign, non-polluting processes or to abate emissions at the tailpipe or stack before release to the atmosphere. A new technology called PremAir® Catalyst Systems1 takes a different approach and directly reduces ambient, ground level ozone. For mobile applications, the new system involves coating a heat exchange device in a vehicle, such as the radiator or air conditioning condenser. The catalyst converts ozone to oxygen as ozone-containing ambient air passes over the coated surface of the radiator. The technology is relatively simple and provides a positive benefit to the environment while being totally passive to the end user application. Volvo Car Corporation was the first automobile manufacturer to voluntarily introduce the technology on their S80 luxury sedan. Nissan Motor Corporation is also using the technology on their new Sentra CA (Clean Air) certified PZEV vehicle for California.

The challenge to substitute less expensive Pd for Pt in TWC catalysts is complicated by the fact that Pd is susceptible to fuel poisons. Laboratory studies indicate that while the precious metal support plays an important role in the CO-NOx reaction, sulfur poisoning dominates. In a reaction to probe selectively the Rh metal function within a washcoat, it was found that small levels of Pd can have a deleterious impact on the performance of the Rh metal. Engine aging studies corroborate the work of recent publications showing that conventional Pd/Rh TWC catalysts exhibit poorer performance than standard Pt/Rh catalysts. The more stringent TLEV and LEV emission standards require more robust catalysts than are currently available. To obtain faster light-off in close coupled positions, the catalyst will experience higher exhaust temperatures. A Pd/Rh catalyst, with an engineered washcoat to minimize alloying, can exceed the performance of a current Pt/Rh commercial catalyst.

The Federal Test Procedure (FTP) test contains an initial period, prior to the catalyst becoming fully activated, during which hydrocarbons escape the vehicle. These hydrocarbons constitute 60-80% of the total emitted over the entire FTP test. To meet future emission levels mandated by the California Air Resources Board, alternate technologies must be created that deal effectively with these cold start hydrocarbons. This paper describes an adsorbent bed/catalyst system that can trap approximately 70% of the available nonmethane hydrocarbons over the first two minutes of the FTP test. Importantly, the trap does not require bypass valves because of a unique heat exchange approach to catalytically consuming the trapped hydrocarbons, and because the trapping materials are unaffected by engine exhaust temperatures below 800°C. Experiments with a prototype system demonstrate that LEV emissions are possible.

Close-coupled catalysts are being actively pursued by automotive engineers in order to meet stringent LEV/ULEV emission standards. However, future applications of close coupled catalyst will be exposed to 50 to 100°C higher operating temperatures with elimination of fuel enrichment to cool the catalyst. A successful close coupled catalyst technology must then be resistant to even higher temperature deactivation and yet continue to function at low temperature during the vehicle cold start. A close coupled catalyst technology is formulated through advanced catalyst design to meet LEV and ULEV emission standards after high temperature aging at 1050°C. This paper will show the inherent stability of the close coupled catalyst for both light-off temperature and steady state performance for aging temperatures up to 1100°C.

Close coupled catalysts represent a solution being pursued by automotive engineers to meet stringent LEV and ULEV emission standards. Close coupled systems provide fast light-off by utilizing the energy in the exhaust gas rather than energy supplied by an auxiliary source such as an electrically heated catalyst or a burner in the exhaust. Previous close coupled catalyst designs were limited by the temperature capability of the catalyst coatings. A successful close coupled catalyst technology has been developed 'that is resistant to higher temperature deactivation. This technology is able to function well at low temperature during the vehicle cold start when light-off is critical. The close coupled catalyst technology has approached ULEV emission levels after aging at 1050°C for 24 hours. This study will present experimental results for a close coupled catalyst including the selection of catalyst volume, cross sectional area and combination of catalyst technologies.

Meeting the California Medium-Duty truck emissions standards presents a significant challenge to automotive engineers due to the combination of sustained high temperature exhaust conditions, high flow rates and relatively high engine out emissions. A successful catalyst for an exhaust treatment system must be resistant to high temperature deactivation, maintain cold start performance and display high three-way conversion efficiencies under most operating conditions. This paper describes a catalyst technology and precious metal loading study targeting a California Medium-Duty truck LEV (MDV2) application. At the same time a direction is presented for optimizing toward the Federal Tier 1 standard through reduction of precious metal use. The paper identifies catalytic formulations for a twin substrate, 1.23 L medium-coupled converter. Two are used per vehicle, mounted 45 cm downstream of each manifold on a 5.7 L V8 engine.

Because of their relatively low particulate make, lean burn natural gas vehicles (NGV's) are a viable approach to meeting the ULEV particulate standards in urban environments where NGV's are substituted for diesel powered buses and other fleet vehicles. Our experience with oxidation catalyst technology for natural gas vehicle emissions abatement has been consistent: that palladium based catalysts maintain excellent NMHC activity and particulate reduction, but methane activity, while initially very high, decreases within the first 50 hours of operation. This paper will show that sulfur oxides at sub-ppm concentrations diminish catalyst methane activity, and that inorganic ash components from the lubricating oil (P, Zn, Ca) do not significantly contribute to the initial catalyst deactivation. Using laboratory simulations, we explore systems approaches to increasing catalyst life.

On-Board Diagnostics for emissions-related components require the monitoring of the catalytic converter performance. Currently, the dual Exhaust Gas Oxygen (EGO) sensor method is the only proven method for monitoring the catalyst performance for hydrocarbons (HC). The premise for using the dual oxygen sensor method is that a catalyst with good oxygen storage capacity (OSC) will perform better than a catalyst with lower OSC. A statistical relationship has been developed to correlate HC performance with changes in OSC. The current algorithms are susceptible to false illumination of the Malfunction Indication Light (MIL) due to: 1. The accuracy with which the diagnostic algorithm can predict a catalyst malfunction condition, and 2. The precision with which the algorithm can consistently predict a malfunction. A new algorithm has been developed that provides a significant improvement in correlation between the EGO sensor signals and hydrocarbon emissions.

As the automobiles move closer to the ULEV, ULEV-2 and SULEV requirements, OBD (on board diagnostic) will become a design challenge. The present OBD II designs involve the use of dual oxygen sensors to monitor the hydrocarbon performance of the catalytic converter. The aim of this study was twofold: to determine the interaction of fuel sulfur and ceria in the catalyst formulation on the performance of a Pd/Rh TWC (three-way catalyst) to elucidate the sulfur and ceria interaction on the ability of the Pd/Rh catalyst to monitor the state of the catalyst relative to hydrocarbon activity and therefore it's utility in the OBD system. Catalyst samples were aged on a spark ignited engine using a “fuel cut” engine aging cycle operated for 50 hours. Maximum catalyst temperatures during this aging cycle were 850-870°C. The effect of sulfur was determined by measuring aged catalyst performance using both indolene (∼100 ppm sulfur) and premium unleaded gasoline (∼350 ppm sulfur).