Evaluation of MnO phase effects in MnO@CeO2 on the low temperature NO catalytic reduction performance with NH3

To accurately evaluate the phase effects of MnOx in Mn-Ce catalysts towards to low temperature NOx removal performance with NH3, MnCO3@CeCO3OH was synthesized firstly and decomposed to MnO2@CeO2, Mn2O3@CeO2 and Mn3O4@CeO2 with similar size and morphology, this will avoid the influence of size and morphology on the experimental results. Experimental results show that the MnO2@CeO2 exhibiting the best NO conversion ratio, which achieved nearly 96.5 % at a low temperature of 150 oC, and the catalytic performance order of MnOx@CeO2 is determined as: MnO2@CeO2>Mn2O3@CeO2>Mn3O4@CeO2 below 200 oC, and MnO2@CeO2>Mn2O3@CeO2≈Mn3O4@CeO2 at range of 200∼400 oC. But the N2 selectivity of Mn2O3@CeO2 reaches 96 % at 100 oC which was higher than that of MnO2@CeO2 and Mn3O4@CeO2. Characterizations including BET, XRD, SEM, H2-TPR, NH3-TPD and FTIR show that MnO2@CeO2 has maximum specific surface area, a stronger redox ability, and more surface acid sites.