Simultaneous removal of soot and NOx over K- and Ba-doped ruthenium supported catalysts

Abstract

Ruthenium-based materials are investigated for the simultaneous removal of soot and NOx and their behavior is compared with that of model Pt-Ba/Al2O3 and Pt-K/Al2O3 catalysts.The materials, 1%wt Ru–10%wt AM/MO (AM=Ba or K; MO=Ce0.8Zr0.2O2, ZrO2, Al2O3), have been prepared by incipient wetness impregnation and characterized by BET, XRD, HRTEM and TPR experiments. The catalytic activity for diesel soot combustion is studied under loose contact conditions by means of TPO (Temperature Programmed Oxidation) while the reactivity in the NOx removal is investigated by Isothermal Concentration Step Change experiments.All the ruthenium-based formulations are active in the combustion of diesel soot, particularly potassium-doped materials that show low onset temperatures, near 230°C. The catalytic activity in the simultaneous removal of soot and NOx shows that Ru-based catalysts are very efficient in the oxidation of soot also under isothermal conditions and that their NOx removal capacity (i.e. storage capacity) is almost comparable to that of traditional Pt-based LNT systems. However, the NOx reduction efficiency of the Ru-containing catalysts is lower than that of traditional LNT Pt-based catalysts.