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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