Materials issues related to catalysts for treatment of diesel exhaust

The driver for lean NO, treatment is the need to meet regulatory standards for diesel engines and gasoline direct injection spark-ignited engines that offer better fuel economy. Efforts over the last decade have been focused toward finding an active lean NO, catalyst that can reduce NO, under oxidizing conditions or strategies such as selective catalytic reduction (SCR), plasma-catalysis, plasma catalyst SCR, and lean NO, traps with varying degrees of success. At present, it appears that SCR with urea and lean NO, traps are the leading contender technologies for commercial deployment. Key issues that remain to be resolved for these two technologies include byproduct formation, dosing control, and durability. In this review, we summarize material-related issues that are unique to each of these technologies, and point out the improvements necessary to facilitate their deployment.