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Recently Volvo Car Corporation introduced the new PremAir® catalyst system from Engelhard Corporation on their S80 luxury sedan and the new V70 estate wagon. In this paper, performance results of this catalyst system after long-term mileage accumulation will be presented. Urban taxi vehicles were used to test the catalyst over 110,000 miles. The rate of deactivation in long-term catalyst performance was found to be dependent on the radiator design, and was least for the radiator design with the highest total geometric surface area. Subsequently, a new catalyst version was developed in order to minimize the deactivation rate. This new catalyst has been evaluated under similar taxi driving conditions over 80,000 miles, and has shown improved durability performance.

The new SULEV legislation for passenger cars with gasoline powered engines, which will be introduced with the California LEV II program in the year 2003, requires a further development of the exhaust aftertreatment system. Three fundamentally different system approaches, each with very high efficiency in reducing cold start hydrocarbons, will be discussed in this paper. Vehicle test results will be presented to illustrate the potential of the respective systems towards the SULEV requirements. Durability aspects are also considered since an increased durability of 120 000 and even 150 000 miles is imposed by the legislation.

Traditional approaches to pollution control have been to develop benign non-polluting processes or to abate emissions at the tailpipe or stack before emitting to the atmosphere. A new technology called PremAir®* Catalyst Systems takes a different approach and directly reduces ambient ground level ozone. This technology can be applied to both mobile and stationary applications. For automotive applications, the new system involves placing a catalytic coating on the car's radiator or air conditioner condenser. As air passes over the radiator or condenser, the catalyst converts the ozone into oxygen. Three Volvo vehicles with a catalyst coating on the radiator were tested on the road during the 1997 summer ozone season in southern California to assess performance. Studies were also conducted in Volvo's laboratory to determine the effect of the catalyst coating on the radiator's performance with regard to corrosion, heat transfer and pressure drop.

This paper describes the development of an improved catalytic converter for the Volvo 850, equipped with a turbo-charged engine which could meet future legislations such as LEV and ULEV. The target has been to develop an underfloor catalytic converter with an improved light-off, OBD2 robustness and less back pressure. The new converter technology, which incorporates substrates with increased cell density and decreased wall thickness shows improved characteristics with enhanced heat and mass transfer. An investigation of metallic substrates with different cell densities shows shortened light-off times with higher cell density. An oxygen storage investigation shows also that increased cell density is a very effective way to reduce the lambda perturbations after the catalyst, giving a stable rear oxygen sensor signal. In the present case this was desirable for the dual sensor system used together with a small catalyst volume in the first position of a cascade of several substrates.

The reactions over a commercially available double layer tri-metal type (Pt, Pd, Rh) passenger car catalyst were analysed. A parameter study was performed in synthetic exhaust gases at: steady state conversion, periodic oscillations, and controlled transients. The influences of gas phase composition, temperature, adiabatic heat of reaction and lambda oscillations were investigated. The reactions of nitrogen oxides, propene and carbon monoxide were simultaneously analysed. Fast response emission analysers were used to record the dynamic properties of the catalysts. The catalyst was found to have high conversion rates and high oxygen storage capacity at relatively low temperatures. The presence of sulphur dioxide was found to reduce the conversion of CO and NOx substantially. An emission increase of 40-70 % was observed for steady state conditions and at oscillating conditions the increase was more than 100%.

The formation of Nitrous Oxide (N2O) over an aged three way catalyst was analysed in a laboratory reactor for a variety of simulated Otto engine exhaust gas conditions. Nitrous Oxide formation was further analysed during FTP75 dynamometer test with a car. The car was equipped with either an aged catalyst or a fresh one. A fast response diode laser system was modified to enable detection of Nitrous Oxide and Carbon Monoxide simultaneously. From laboratory data the kinetics of Nitrous Oxide formation were evaluated with mathematical simulations and a mechanism was suggested. The results were compared to data from vehicle tests and the results were discussed in the light of the laboratory study. Two general trends were confirmed, i) N2O formation increases at slightly lean conditions: ii) catalysts with a low degree of deterioration gave lower N2O emissions, iii) the extent of N2O formation goes though a maximum with respect to dissociation rate of NO.