HC-SCR Catalyst Performance in Reducing NOx Emissions from a Diesel Engine Running Heavy Duty Transient Test Cycles with Diesel Fuel and Ethanol as the Reductants

A unique silver/alumina selective catalytic reduction (SCR) catalyst which used hydrocarbons (HC-SCR) to reduce NOx emissions was investigated. Diesel fuel or ethanol were used as the reductants to evaluate catalyst performance. Several full size 5.0L monolith 2.0 and 3.0 wt.% Ag₂O-Al₂O₃ catalysts were created. Testing was conducted using a 6.6L Duramax turbocharged heavy duty diesel engine. Dynamometer testing on the heavy duty FTP and SET 13 transient test cycles was conducted.

The NOx conversion efficiency was evaluated as a function of catalyst volume, inlet cone angle, hydrocarbon to NOx ratio (HC:NOx), and space velocity. Oxygen effects on the NOx reaction and the HC slip past the HC-SCR catalyst were also determined. An FTIR was used to evaluate unregulated emissions. Testing on the heavy duty FTP and SET 13 test cycles, with diesel fuel as the reductant, resulted in a 60% and 65% NOx conversion reduction respectively. With ethanol as the reductant the corresponding NOx conversions were both 91%.