Nanostructured Potassium-Manganese Oxides Decorated with Pd Nanoparticles as Efficient Catalysts for Low-Temperature Soot Oxidation

Two nanostructured potassium–manganese oxides, with a layered (OL) and tunneled structure (OMS-2), were synthesized and their surface decorated with 1% Pd. All prepared samples were characterized by means of X-ray diffraction, Raman spectroscopy, N2-BET specific surface area analysis, TPR, SEM/TEM. Catalytic activity in soot combustion in different reaction conditions was investigated (tight contact, loose contact, loose contact with NO addition). The obtained results revealed, that manganese oxides are highly catalytically active in soot combustion, shifting the reaction temperature window by 280 °C for OMS-2 and 300 °C for OL in comparison to the non-catalytic process. Furthermore, Pd promotion is beneficial in all cases, lowering the window of soot combustion compared to the unpromoted oxides, with the most significant effect for loose contact conditions. The difference in activity between tight and loose contacts can be successfully bridged in the presence of NO due to its transformation into NO2. The particular activity of 1% Pd/OMS-2 and 1% Pd/OL pave the road for their further development towards catalytic system for efficient soot removal in the conditions present in diesel exhaust gases.