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Comparative study of impact of thermal aging on both surface morphology and catalyst performances was performed over fully formulated commercial lean NOx Trap using hydrothermal (oven) and engine aging for 5 hours at 750°C and 5 hr at 800°C. Investigations show that engine aging lead to more important degradation than hydrothermal aging because of the greater structural degradations that happened after engine aging: sintering of Pt particles, reaction of support (γAl₂O₃) with the storage material and a higher drop of surface area. It follows a decrease of oxidation and storage efficiency particularly after engine aging. During lean rich cycle environment, the rich step was not efficient to remove all the stored NOx due to storage on Ba-Bulk sites leading to accumulation of NOx after each cycle. The observed trend after engine aging was attributed to the presence of sulfur and mainly to soot as engine aging was performed with low concentration of sulfur in fuel.

One of the challenges in the automotive industry is to develop new vehicles and new technologies with minimal costs. In this context, modeling becomes an important tool for the design of future technologies by reducing the number of tests needed to develop a new exhaust system. With the emergence of future European standards, which are more restrictive on NOx and takes account of the differentiation between NO and NO₂ emissions, European manufacturers have to describe precisely the formation and the behavior of NO₂ in the aftertreatment systems. The aim of this study is to improve the one-dimensional aftertreatment models developed by Renault by introducing the NO₂ contribution from the engine to the tailpipe. The first part of this study focuses on the adaptation of aftertreatment systems models in order to differentiate NO and NO₂. Thus different global kinetics models for the Lean NOx-Trap System were studied.

With growing concern about air quality and increase of city population is renewed interest in transportation sector. The challenge for governments is to find and develop cost-effective ways to improve urban air quality without scarifying economy. Natural gas as vehicle fuel can reduce compared to conventional Diesel technology, particulate matter by as much as 99%, nitrous oxides (NOx) by as much as 85%, and carbon monoxide (CO) by more than 90%. Relative to gasoline, the global warming impact (GWI) for dedicated natural gas vehicles (NGVs) is generally more than 20 % lower. When non-regulated emissions are included on a well-to-wheel basis, NGVs still show advantages over gasoline and Diesel vehicles. Nowadays, there are more than 4.7 million NGVs in operation all around the world. It seems that the catalysts used in NGVs are close to Three-Way Catalysts (TWC) typically used for gasoline engines. However, there are very few studies about the impact of catalysis for NGVs.