Potassium–copper and potassium–cobalt catalysts supported on alumina for simultaneous NOx and soot removal from simulated diesel engine exhaust

This paper deals with the activity of bimetallic potassium–copper and potassium–cobalt catalysts supported on alumina for the reduction of NOx with soot from simulated diesel engine exhaust. The effect of the reaction temperature, the soot/catalyst mass ratio and the presence of C3H6 has been studied. In addition, the behavior of two monometallic catalysts supported on zeolite beta (Co/beta and Cu/beta), previously used for NOx reduction with C3H6, as well as a highly active HC-SCR catalyst (Pt/beta) has been tested for comparison. The preliminary results obtained in the absence of C3H6 indicate that, at temperatures between 250 and 400 °C, the use of bimetallic potassium catalysts notably increases the rate of NOx reduction with soot evolving N2 and CO2 as main reaction products. At higher temperatures, the catalysts mainly favor the direct soot combustion with oxygen. In the presence of C3H6, an increase in the activity for NOx reduction has been observed for the catalyst with the highest metal content. At 450 °C, the copper-based catalysts (Cu/beta and KCu2/Al2O3) show the highest activity for both NOx reduction (to N2 and CO2) and soot consumption. The Pt/beta catalyst does not combine, at any temperature, a high NOx reduction with a high soot consumption rate.