(448b) Discovery and Optimization of Nsr Catalysts Via High-Throughput Experimentation

High-throughput experimentation (HTE) allows for simultaneous synthesis and screening of large arrays of different materials accelerating the discovery and optimization process. In addition, design of experiments in combination with HTE can provide a powerful toolbox for the systematic study of vast parameter spaces encountered in the design and optimization of heterogeneous catalysts. We have applied this general approach for the study of NOx storage and reduction (NSR) catalysts.

In the current work, we have explored the effect of adding transition metals (Fe, Mn and Co) to improve the performance of 1% w/w platinum and 15% w/w barium (1Pt/15Ba) containing NSR catalysts using the high throughput experimental set-up. Under fuel lean conditions, the addition of Mn or Fe slightly improved the NOx storage, while the addition of Co more than doubled the NOx storage. In addition, a noble metal free 5Co/15Ba catalyst was found to store NOx as efficiently as a 1Pt/15Ba NSR catalyst. This increase in efficiency is associated with the strong oxidizing effect of Co, providing nitric oxide oxidation sites and contact area for NO2 spillover to the Ba NOx storage sites.

In order to further verify the promotional effect of Co, we have also studied the effect of adding Co to Pt/Ba or Rh/Ba based NSR catalysts as a function of cyclic operating conditions using standard statistical design of experiments. It was found that addition of Co dramatically increases the performance of both the Pt/Ba and Rh/Ba based NSR catalysts at higher lean fractions, allowing a substantial improvement in overall fuel efficiency. Preliminary conclusions from these studies also suggest that the cost of NSR catalysts can be dramatically reduced by replacing Pt with Co as the active oxidizing metal in NSR catalysts formulation. In addition, we have also optimized the catalyst composition and identified the optimum catalyst composition for Pt/Rh/Co/Ba based NSR system. These studies will clearly establish the utility of HTE when combined with design of experiments for the efficient analysis of such vast multidimensional systems and for the discovery of new materials.