Ambient temperature NOx emission control for lean-burn engines by electro-catalytic tubes

Lean-burn gasoline and diesel automobiles can have superior fuel efficiency but require advanced DeNOx technology. For a catalytic converter to be put underneath the passenger cars, it must be compact enough. Effective automotive DeNOx treatment should start at ambient temperature to avoid a heating period when the pollutant cannot be effectively treated. An electro-catalytic honeycomb, composed of electro-catalytic tubes, would fulfill this size requirement. This work demonstrates that effective lean DeNOx can be performed at ambient temperature by an electro-catalytic tube. The DeNOx activity is relatively insensitive to the variation of temperature from 200 to 600 °C and increases slightly when temperature decreases from 200 °C to ambient, but is quite sensitive to that of either the oxygen concentration or the NOx concentration. When the oxygen concentration and the NOx concentration increase from 0.5 to 14% and from 250 to 3800 ppm, respectively, the DeNOx activities increase considerably. The NO conversion also increases with decreasing NOx concentration below 250 ppm, when there is zero NO2 yield; these can result in zero NOx emission.

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► Electro-catalytic tube is effective for lean DeNOx by direct NOx decomposition.
► Facile oxygen desorption is driven by self-generated electromotive force.
► Effective lean DeNOx can be performed at ambient temperature.
► Increasing oxygen concentration enhances the DeNOx activity considerably.
► Increasing NOx concentration can increase the DeNOx activity considerably.