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The introduction of gasoline direct injection technology into the European market will depend mainly on the availability of an effective and durable aftertreatment system, in order to reach future stringent European emission standards. NOx storage technology provides a reasonable chance of fulfilling future emission goals, but durability problems such as thermal degradation and sulfur poisoning have yet to be overcome. The present paper is dedicated to these problems, and demonstrates the progress achieved so far. The influence of different aging modes and aging severity on the NOx conversion efficiency of an advanced generation of NOx storage catalysts, is described in detail. It was found that the severity of aging at comparable catalyst bed temperatures, increases in the following order: hydrothermal aging in N2/H2O < engine aging w/o fuel cut at λ-1 < furnace aging in air < engine aging with fuel cut at λ-1.

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.