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Within the framework of the French research program PREDIT, a study was undertaken by ADEME, IFP, LGRE, PSA Peugeot Citroën and Umicore, whose main objective was a better understanding of the NOx storage and reduction phenomena on an aged, sulfated and desulfated NOx-trap. The target of this work was to use the information on catalyst working conditions to optimize catalyst management for a gasoline direct injection engine. The catalysts were characterized on both engine and synthetic gas benches. Aging and poisoning phenomena were studied and a variety of different chemical analytical tools were used. The behavior of two different thermally aged cores was investigated under rich conditions on a synthetic gas test bench. The dependence of the NOx regeneration efficiency of the traps is reported for several operating parameters, including reductant concentrations, durations of the rich pulse and trap loadings.

Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have been exploring development avenues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by FSH (Fonds de Soutien aux Hydrocarbures), IFP, PSA-Peugeot-Citroën, Renault and Renault VI (Véhicules Industriels), has been built to study this point. It is a four years programme with different steps which will focus on new engine technologies: some of them are going to be marketed very soon (gasoline direct injection car engine, and diesel common rail injection car and truck engines) to anticipate the Euro 3 (2000) and the Euro 4 (2005) emissions specifications. The original work reported here is part of this research.