Abstract
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.Graphical
Highlights
One common way to produce energy is the burning of carbon fuels
Apart from numerous advantages, these engines have a large defect in the form of high emissions of nitrogen oxides (NOx) and particulate matter (PM)
It was observed that the calcination in the flow of air after immobilization of Pd nanoparticles to OL induced a partial solid-state phase transition from OL to OMS-2 as evidenced by the appearance of characteristic peaks for OMS-2 in the XRD pattern for Pd supported on OL
Summary
One common way to produce energy is the burning of carbon fuels. In ideal conditions the only products are water and CO2. Promotion by alkali metals is reported to increase the catalysts ability to activate oxygen (by lowering the work function of the catalysts surface) as well as to form compounds with low melting point temperatures. This is meant to increase the number of contact points between the catalyst surface and soot particles, which is essential for soot oxidation [17,18,19,20]. The effect of NO, which is present in the diesel gas stream, is evaluated as an effective way to transfer oxygen (in the form of NO2) from the catalyst to soot particles, bridging tight and loose contact conditions
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