MnOx-CeO2 binary oxides for catalytic NOx-sorption at low temperatures.: Selective reduction of sorbed NOx

The reactivity of NOx sorbed onto MnOx-CeO2 toward H-2 was studied in the presence of impregnated Pd catalyst by use of TPR, H-2 pulse reactions, in situ FT-IR, and steady-state NO-H-2-O-2 reactions. The Pd-loaded catalyst after saturated NOx-sorption at 150 degreesC could be regenerated by micropulse injections of H-2, which ensure the reduction of monodentate, bidentate, and ionic nitrates sorbed on MnOx-CeO2 into N-2. In the steady-state NO-H-2-O-2 reaction, gaseous NOx was first sorbed onto MnOx-CeO2 and subsequently reduced at the PdO/MnOx-CeO2 boundary. Despite the nonselective character of Pd catalysts toward NOx-H-2 reaction, Pd/MnOx-CeO2 attained 65% NO-conversion of a stream of 0.08 vol % NO, 2 vol % H-2, and 6 vol % O-2 in He at a low temperature of 150 degreesC, compared to similar to 30% for Pd/gamma -Al2O3, the reaction on which was more suppressed by the competitive H-2-O-2 reaction. The combination of NOx sorbability of MnOx-CeO2 and H-2 activation of Pd catalysts was found to give rise to a synergistic effect, thus paving the way to development of NOx-sorbing catalysts for selective deNO(x) processes at low temperatures (<150 <degrees>C).