Low-temperature NOx removal for flue gas cleanup

NOx reduction with hydrocarbons is studied at temperatures around 150 degrees C to develop an easy retrofit NOx removal process to be located downstream of the particulate control device for flue gas cleanup. Acetone is the most active hydrocarbon reductant for NO reduction in the presence of O-2 and H2O. At 150 degrees C, 35% NO reduction was obtained over 5% Cu-2% Ag/PCB. The activity, however, is greatly decreased by the presence of SO2. NO oxidation to NO2 is studied for further improving the NO reduction activity because NO2 is known to be more reactive than NO. Active carbon fibers and PCB active carbon are both active for NO oxidation at low temperature, but the activity decreased with temperature. Ten percent Co3O4/Al2O3 and 5% Au/Co3O4 are not active for NO oxidation in the absence of SO2 and at 150 degrees C, but are very active in the presence of SO2 and H2O. Five percent Au/Co3O4 is especially stable for NO oxidation to NO2 at temperatures from 120 to 150 degrees C for more than 15 h.