Study On CO Oxidation And NO Reduction Of Mn-Based Complex Oxides

Mn-Ce-O,Mn-Cu-O,Mn-Cu-Ce-O,Mn-Cu-Ce-La-O complex oxides were prepared by an improved amorphous citric precursor method.The complex oxides were characterized by XRD,H₂-TPR measurements.The catalytic activities of the catalysts were investigated by CO+O₂ and NO+CO model reaction in the continuous fixed bed microreactor.The XRD results indicate that Mn-Ce-O complex oxide is mainly composed of cubic fluorite CeO₂ and cubic Mn₂O₃.Some of the Ce⁴⁺ions is incorporated into Mn₂O₃ lattice which induces the expansion and distortion of the lattice of Mn₂O₃,and some Mnⁿ⁺ions incorporates into the CeO₂ lattice which leads to the shrinkage of CeO₂ lattice.Mn-Cu-O complex oxide is mainly consisted of CuMn₂O₄ spinel and monoclinic CuO.There are crystalline peaks of CeO₂ and CuMn₂O₄ in Mn-Cu-Ce-O complex oxide.Mnⁿ⁺and Cuⁿ⁺replacing part of Ce⁴⁺incorporate into the lattice of CeO₂ and lead to distortion CeO₂ lattice,so that more lattice defects and oxygen vacancies are produced.Mn-Cu-Ce-La-O complex oxide are mainly composed of the crystalline peaks of CeO₂ and CuMn₂O₄ spinel.H₂-TPR analysis shows that the incorporation of Ce⁴⁺ions into the Mn₂O₃ lattice is beneficial to improve the reduction performance of Mn-Ce-O complex oxide,so that the H₂-TPR temperature of Mn-Ce-O is shifted to the low temperature region.Because of the strong interaction between CuO and CeO₂,the H₂-TPR temperature of Mn-Cu-Ce-O is shifted to the low temperature region.H₂-TPR temperature of Mn-Cu-Ce-La-O is obviously lower than that of Mn-Cu-Ce-O,which indicates that there is strong synergistic effect between Mn-Cu-Ce-La.Experiments of CO oxidation show that the CO conversion of Mn-Cu-O and Mn_3xCu_3?1-x?Ce₇ complex oxides reach 80%and 96%at400?,respectively.The intergrowth and coexistence effect between Ce-Cu promotes the CO oxidation activity of Mn-Cu-Ce-O.The strong interaction between CeO₂ and La₂O₃ improves the CO catalytic activity of Mn-Cu-Ce-La-O significantly,the CO conversion of Mn_1.5Cu_1.5Ce_7yy La_7?1-y?complex oxide nearly reach 100%at 250?.Experimental results of catalytic reduction of NO display that the NO conversion of Mn-Cu-O and Mn_3xCu_3?1-x?Ce₇ complex oxides reach 80%and 95%at 400?,and the NO conversion of Mn_1.5Ce_1.5Ce_7yLa_7?1-y?nearly reaches 100%at250?,respectively.The regulation of reaction is consistent with the catalytic oxidation of CO.