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The challenge for decreasing the emissions of compression ignition engines now remains mainly on NOx control. If the Lean NOx Trap (LNT) and Selective Catalytic Reduction by Urea (Urea-SCR) are very efficient, their extra-cost and management are a major issue for the OEMs. In that context, the selective catalytic reduction by hydrocarbons (HC-SCR) appears to be an interesting alternative solution, with a more limited NOx conversion efficiency but an easier packaging (diesel fuel as a reductant) and a limited price (reasonable coating cost / no PGM). In the framework of the RedNOx project, a prototype catalyst made of 2% silver on Alumina coated on cordierite was manufactured and tested on a synthetic gas bench. In parallel, an exhaust implementation study has been led to ensure the most suited conditions for injection. Thanks to SGB and simulation results, adapted engine tests have been designed and performed.

In urban areas, particulate emission from Diesel engines is one of the pollutants of most concern. As a result, particulate emission control from urban bus Diesel engines using particulate filter technology is being introducing in La Rochelle. The Diesel Particulate Filter (DPF) introduction on the existing urban bus fleet has been initiated by the CDA La Rochelle through a voluntary retrofit program. The class of urban bus to be retrofitted is based on EURO 1 and EURO 2 Diesel engines, using a standard European Diesel fuel with 300ppm of Sulphur content. In that case, the appropriated technology for DPF regeneration requires a very flexible strategy for DPF regeneration, such as the use of the Ceria-based Fuel-Borne Catalysts. The paper describes the practical approach developed to install and optimize the DPF System on the urban buses.

Since the market introduction of the Diesel Particle Filter (DPF) system in serial applications in May 2000, more than 500,000 vehicles have been DPF-equipped. Tracking the serial production current situation, several themes for improvement have been identified, including system simplification to limit its total cost as well as proposition to optimize maintenance. The paper presents those upgrades that will be proposed in serial applications. Based on a DPF regeneration assisted by engine management systems in combination with the use of a Ceria-based fuel-borne catalyst, the first improvement is to limit the ash build up phenomenon of fuel-borne catalyst and then to limit the DPF clogging effect. In the first stage, catalytic activity of Ceria-based fuel-borne catalyst has been improved, by introducing Iron as a catalytic promoter.

It has been recently shown that (Ce, Zr)O2 mixed oxides provide improved catalytic performances compared to pure CeO2. Cerium oxide is the active Oxygen Storage Capacity (OSC) component in three way catalysts. However, higher performances, including OSC enhancement, can be achieved with thermally stable solid solutions of Ce and Zr oxides. In the present paper, we describe the structure and the advantages of Ce rich (Ce, Zr)O2 solid solutions and the improved catalytic properties of these materials when used in association with platinum. Various analytical techniques were used including thermo-reduction methods, OSC measurements, surface area measurements, XRD, HRTEM, XPS, and XANES/EXAFS.

Rare earths compounds, especially CeO2, are widely used in automotive catalysis. Cerium dioxide contributes to the stabilization of precious metals but is particularly well known to be the active component for oxygen storage capacity (OSC). Standard cerium dioxide has poor thermal stability at temperatures higher than 800°C. A new generation of metal based oxides has been studied possessing high thermal and OSC stability. We have demonstrated that commercially available Ce rich solid solutions of (Ce, Zr)O2 showed the highest surface areas with remarkably improved OSC and phase stability versus temperature.