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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.

The two most common NOx reducing technologies, in an oxygen abundant exhaust stream, are urea selective catalytic reduction urea-SCR and lean NOx trap (LNT) catalysts. Each technology has advantages and disadvantages. Another selective catalytic reduction (SCR) catalyst that uses hydrocarbons (HC-SCR), specifically diesel fuel, as the reductant to reduce NOx emissions was investigated. This catalyst is a result of a high throughput discovery project and conducted in cooperation with BASF, Accelrys and funded by the Department of Energy (DOE.) Several full size 5.0L monolith catalysts were made and evaluated using a V6 turbo charged diesel engine connected to a dynamometer running light-duty transient test cycles. The NOx efficiency on the HWYFET and US06 tests were measured to be 92% and 76% respectively. The FTP was 60% on a weighted basis.