(691b) Influence of Preparation Conditions on Washcoat-Free Platinum and Palladium Catalysts Supported on Anodically Oxidized Stainless Steel Wire Meshes for CO Oxidation

Due to negative health and environmental impacts related to the emissions of CO, strict regulations are imposed to limit CO concentrations in combustion exhaust. To comply with these regulations, precious metal catalysts, namely platinum and palladium are commonly utilized. These catalysts are often washcoated on a monolith. However, alumina washcoated on cordierite, one of the most used material systems, suffers from washcoat delamination due to thermal expansivity mismatch of the two materials ^[1].

To increase the catalyst dispersion and activity without a washcoat, this study utilized anodic oxidation as a pre-treatment step to modify the surface of the stainless-steel mesh before impregnation with platinum and palladium. A similar approach has been utilized previously in literature for low temperature volatile organic compound oxidation ^[2], however the utility of these catalysts has not been previously examined under high temperature combustion exhaust gas where the elimination of the washcoat provides a distinct benefit.

Three synthesis parameters; namely electrolyte identity, applied voltage, and electrolyte weight percent, were examined using an L9 Taguchi Design of Experiments. The results of this design determined that the most important parameter influencing the efficacy of the final impregnated catalyst system was the identity of the electrolyte as shown in shown in Figure 1. Additionally, this treatment methodology is shown to be effective as the pre-treatment increases the performance of the catalyst by ~5.5 times relative to stainless-steel mesh which received no pre-treatment. A combination of previous metal uptake, oxide layer growth and surface structuring were determined to be responsible for the differences in activity. Finally, the most active catalyst was examined for a 100-hour time-on-stream study in which the catalyst was shown to be stable.

1. Wu, D., et. al. Ind. Eng. Chem. Res 2013, 52, 12713-14721.
2. Song, C., et. al. Chinese J.. Chem. 2009, 27, 1903-1906.