Selective catalytic reduction of nitric oxide with ethanol/gasoline blends over a silver/alumina catalyst

•We evaluate the NO SCR activity of ethanol/gasoline blends over silver/alumina.•Blends containing 50% or more ethanol exhibited NOx conversions above 90%.•NO2 and acetaldehyde behave like intermediates in the ethanol SCR of NO.•Gasoline HCs do not deactivate the low temperature ethanol SCR activity.•Ethanol does not appear to promote the activity of gasoline hydrocarbons.

Lean gasoline engines running on ethanol/gasoline blends and equipped with a silver/alumina catalyst for selective catalytic reduction (SCR) of NO by ethanol provide a pathway to reduced petroleum consumption through both increased biofuel utilization and improved engine efficiency relative to the current stoichiometric gasoline engines that dominate the U.S. light duty vehicle fleet. A pre-commercial silver/alumina catalyst demonstrated high NOx conversions over a moderate temperature window with both neat ethanol and ethanol/gasoline blends containing at least 50% ethanol. Selectivity to NH3 increases with HC dosing and ethanol content in gasoline blends, but appears to “saturate” at around 45%. NO2 and acetaldehyde behave like intermediates in the ethanol SCR of NO. NH3 SCR of NOx does not appear to play a major role in the ethanol SCR reaction mechanism. Ethanol is responsible for the low temperature SCR activity observed with the ethanol/gasoline blends. The gasoline HCs do not deactivate the ethanol SCR activity, but they also do not appear to be significantly activated by the presence of ethanol.

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