NOx storage and reduction characteristics of Pd/MnOx–CeO2 at low temperature

The reaction between hydrogen and NO was studied over 1 wt.% Pd supported on NOx-sorbing material, MnOx–CeO2, at low temperatures. The result of pulse mode reactions suggest that NOx adsorbed as nitrate and/or nitrite on MnOx–CeO2 was reduced by hydrogen, which was spilt-over from Pd catalyst. The NOx storage and reduction (NSR) cycles were carried out over Pd/MnOx–CeO2 in a conventional flow reactor at 150 °C. In a storage step, NO was removed by the oxidative adsorption from a stream of 0.04–0.08% NO, 5–10% O2, and He balance. This was followed by a reducing step, where a stream of 1% H2/He was supplied to ensure the conversion of nitrate/nitrite to N2 and thus restore the adsorbability. It was revealed that the NSR cycle is much more suitable for the H2–deNOx process in excess O2, compared to a conventional steady state reaction mode.