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The reduction of NOx using NH₃ has been successfully practiced for stationary sources and more recently, for passenger cars and heavy-duty applications in the US and Europe. Due to the up-coming Euro 6 regulations (2014) for passenger cars and light-duty trucks, NH₃-SCR catalyst technologies are extensively studied by OEMs, catalysts manufacturers and raw materials suppliers, all looking for technologies very efficient at low temperatures, thermally stable up to 800°C and with a limited impact of the NO₂/NOx ratio on activity. Among the new emerging SCR catalytic systems, non-zeolitic zirconia-based mixed oxides were introduced recently in SAE 2008 as promising new SCR catalysts. This paper reports the progress made on these materials. "Synthetic Gas Bench Tests" performed on powder catalysts show a significant increase of the NOx conversion, in comparison with that previously reported.

Acidic zirconia materials have been tested as catalysts for the Selective Catalytic Reduction of nitrogen oxides (NOx) by ammonia (NH3-SCR). This paper focuses on the promotion of acidic zirconia by ceria. The introduction of ceria increases the NOx conversion, the selectivity to N2 and the durability and makes acidic zirconia materials attractive for Diesel after treatment systems.

The reduction of NOx from Diesel Engines or Lean-burn Gasoline Engines is a major issue in automotive catalysis. Over the last several years, many solutions to remove NOx under lean operating conditions have been considered. Attention is now focused on two main technologies: (i) Selective Catalytic Reduction using ammonia as reductant (urea SCR) and (ii) NOx-Storage Catalyst (NSC). This paper deals with materials for NOx storage catalysts. NSC catalysts show high efficiency as fresh, but their durability is low due to a fast deactivation of the active sites [1,3]. This issue relates to a drastic sintering of the materials after ageing, especially during the regeneration and the desulfation [3, 4 and 5]. Moreover, the current materials are sensitive to SOx poisoning [1,3,4]. In this paper, ceria based oxides have been examined as NOx-storage materials and Pt carriers as well. These oxides contain high ceria loading and are thermally stable up to 900°C.

Acidic doped zirconia catalyst supports with high thermal stability and high SOx resistance have been tested in Diesel exhaust. This paper focuses on the optimization of these materials to get the best trade-off between acidity and thermal stability. These materials were tested as a Platinum support for Diesel Oxidation Catalysts (DOC). Preliminary data are also discussed concerning their ammonia adsorption properties for the Selective Catalytic Reduction of NOx by ammonia (SCR).

The reduction of NOx from Diesel Engines or Lean-burn Gasoline Engines is a major issue in automotive catalysis. Over the last several years, many solutions to remove NOx under lean operating conditions have been considered. Attention is now focused on two main technologies: (i) Selective Catalytic Reduction using ammonia as reductant (urea SCR) and (ii) NOx-Storage Catalyst (NSC). This paper deals with materials for NOx storage catalysts. Even if the fresh NSC shows high efficiency, its durability is low due to a fast deactivation of the active sites [1,3]. This problem relates to a drastic sintering of the materials after ageing, especially during the regeneration and the desulfation [3, 4 and 5]. Moreover, the current materials are sensitive to SOx poisoning [1,3, 4]. In this paper, modified Ba-alumina oxides used as NOx-Storage materials have been investigated. These oxides contain high Ba loading (such as 20 wt% Ba) and are thermally stable.

Thermally stable CeO2/ZrO2 oxygen storage materials [1, 2, 3, 4, 5, 6 and 7] are necessary to get advanced TWC catalysts complying with the more severe regulations. In addition to the thermal stability, the increase of the bulk oxygen mobility of the CeO2/ZrO2 mixed oxides is of great interest to boost the conversion of the pollutants under transient modes and during the cold start operations as well. This paper deals with the recent progress achieved in the preparation of thermo-stable highly reducible mixed oxides. Thanks to a new process, with mild conditions, Rhodia developed new CeO2/ZrO2 mixed oxides with outstanding oxygen availability as well as high surface area over the whole composition range [5]. These materials show a pure solid solution and a BET surface area higher than 20 m2/g after air ageing at 1100°C.

New doped zirconia with high thermal stability and high sulfur resistance have been developed for Diesel Oxidation Catalysts (DOC). The present work is focused on rare earths-doped zirconia and base metal-doped zirconia which are preferred carriers of precious metals to improve catalytic performance and durability.

To meet severe legislation limits and reduce cold start emissions, car manufacturers use improved engine control technologies, supports with higher cell densities, lower thermal mass, turbulent like flows, and bring the three-way catalysts (TWC) closer and closer to the engine. These catalysts show long term durability and thermal stability at temperatures higher than 1000 °C. Thus PGM carriers are extensively investigated to assure high activity and long term durability with low PGM loading. Hence Rhodia has developed a new generation of hybrid Zirconia oxides. These materials show phase stability and thermal stability at temperatures higher than 1100°C, and keep PGM available after harsh aging, as even at very low PGM loadings. In this paper we focus first, on stability and catalytic performance of laboratory aged PGM powder model catalysts. We show that there is a strong relationship between catalytic activity and the nature of the PGM/support interaction.

A new generation of hybrid zirconia oxides with high thermal stabilities has been developed. These new materials, covering a wide range of compositions, are investigated as carriers of precious metals for Diesel Oxidation Catalysts (DOC). In this paper, we show that they can be advantageously used for both Pt and Pd-based technologies to improve catalytic performance and possibly durability. Indeed, rare earths doped zirconia containing 60 wt% ceria used as Pd carrier show early light-off activity which is promising for reduced cold start emissions.

To meet severe legislation limits, car manufacturers use close-coupled three-way catalysts (TWC) to reduce cold start emissions. These catalysts show long term durability and thermal stability at temperatures higher than 1000 °C. Mixed ceria-zirconia oxides are an important component of these TWCs. Ceria-rich, mixed oxides have a high crystalline structure defects density, and thus show high oxygen storage capacity (OSC). They are appropriate precious metal supports up to 1000°C. For applications which require higher thermal durability, zirconia-rich mixed oxides are used to make active catalysts because of their good thermal stability. Rhodia has developed a new generation of mixed oxides with high OSC and high thermal stability, covering a wide range of compositions. These materials show phase stability and thermal stability at temperatures greater than 1100°C for Zr-rich as well as Ce-rich compositions.