Credit: © 2009 ACS

The drive for more efficient automotive engines has resulted in the development of 'lean-burn' technologies. Unfortunately, one consequence of this is that the catalysts that remove harmful NOx from the exhaust no longer work as efficiently, as they rely on unburnt hydrocarbons to reduce these species. The search is on, therefore, for catalysts that can do the job with lower hydrocarbon content.

Now, Richard Laine and colleagues at the University of Michigan, working with a team from the University of Saarland led by Klaus Stöwe, have used an integrated high-throughput strategy to make and screen a variety of metal oxide catalysts. They used flame spray pyrolysis, which is a quick synthesis technique where the product composition exactly matches that of the precursor solutions. Over 40 samples with varying ceria, alumina and zirconia contents were created.

During a reaction, high-throughput emissivity-corrected infrared thermography screening was used to measure the temperature change of each catalyst, which is proportional to its activity. The most effective catalyst, Ce0.7Zr0.3O2, reduced 50% of the NOx and oxidized up to 100% of the propene. Although peak performance was better for some reference catalysts (platinum or silver on alumina, and a copper-zeolite), Ce0.7Zr0.3O2 performed consistently over a wide temperature range and was more robust to deactivation by water and sulfur dioxide.