Search Results

Global demand for alternative fuels to combat rising energy costs has sparked a renewed interest in catalysts that can effectively remediate NOx emissions resulting from combustion of a range of HC based fuels. Because many of these new engine technologies rely on lean operating environments to produce efficient power, the resulting emissions are also present in a lean atmosphere. While HCs are easily controlled in such environments, achieving high NOx conversion to N2 has continued to elude fully satisfactory solution. Until recently, most approaches have relied on catalysts with precious metals to either store NOx and subsequently release it as N2 under rich conditions, or use NH3 SCR catalysts with urea injection to reduce NOx under lean conditions. However, new improvements in Ag based technologies also look very promising for NOx reduction in lean environments.

With the world-wide growth of the automotive emissions controls market, concerns about the future cost and availability of catalytic metals, particularly rhodium, have also grown. These factors have led to an increased interest in catalyst formulations which might allow reduced Rh usage or the complete removal of Rh from the catalyst without compromising the performance of emissions control systems. We have tested a set of catalysts to examine Ru, Ir, and Pd as alternatives to Rh, either alone or in combination with Pt. For the nine catalysts of Pt, Rh, Pd, Ru, Ir, Pt/Rh, Pt/Pd, Pt/Ru, and Pt/Ir studied, the loading of all constituent metals on 85 cu. in. monoliths in single or 1:1 dual component catalysts was 0.038 oz t, except for Rh which had a 0.0038 oz t loading. Most of the monoliths were evaluated after 0, 6, and 75 hours on a rapid aging test schedule using sweep, light-off, dynamometer and/or vehicle tests using the Federal Test Procedure (FTP).