Remarkable enhancement of the deNOx efficiency at low temperature: collaborative effect of ethanol and NH3 for the NO Selective Catalytic Reduction

Abstract

International audienceThe NOx selective catalytic reduction (SCR) is extensively studied as an effective process for air pollutants abatement from lean burn and Diesel vehicles. In the implemented Urea-SCR technology, the NO2/NOx ratio is a key parameter that limits the deNOx efficiency at low temperature (175-250°C). We demonstrate that co-feeding of ammonia and ethanol on a Ag/Al2O3 catalyst enables a drastic enhancement of the NOx conversion using only NO as NOx (standard SCR condition). The ammonia activation is not attributed to a direct reaction with NO but both to the presence of NO2 provided by the NO oxidation with EtOH, and the availability of hydrogen H* species resulting from EtOH oxidation. In order to improve the use of the injected ammonia, this EtOH-assisted process was experimented with a dual-bed configuration (Ag/Al2O3+NH3-SCR catalyst). It allowed a remarkable supplementary enhancement of the NOx conversion in the 175-250°C temperature range in the unfavorable standard SCR condition