Gieshoff, J., Pfeifer, M., Schäfer-Sindlinger, A., Spurk, P. et al., "Advanced Urea SCR Catalysts for Automotive Applications," SAE Technical Paper 2001-01-0514, 2001, doi:10.4271/2001-01-0514.
The LEV II and EURO V legislation in 2007/2008 require a high conversion level for nitrogen oxides to meet the emission levels for diesel SUVs and trucks. Therefore, U.S. and European truck manufacturers are considering the introduction of urea SCR systems no later than model year 2005. The current SCR catalysts are based mainly on systems derived from stationary power plant applications. Therefore, improved washcoat based monolith catalysts were developed using standard types of formulations. These catalysts achieved high conversion levels similar to extruded systems in passenger car and truck test cycles. However, to meet further tightening of standards, a new class of catalysts was developed. These advanced type of catalytic coatings proved to be equivalent or even better than standard washcoat formulations. Results will be shown from ESC, MVEG and US-FTP 75 tests to illustrate the progress in catalyst design for urea SCR. The new catalyst systems show a very good aging performance and will be the next generation of urea SCR catalysts for mobile applications.