Preparation, Characterization And Catalytic Performance Of Different Metallic Oxides Supported On Mno_x/γ-Al₂O₃

Part ⅠA series CuO/Mn2O3/γ-Al2O3catalysts were prepared by impregnation and characterized by XRF, XRD, H2-TPR, in-situ FT-IR and activity test for oxidation of carbon monoxide.XRD results proved that the amount of well-dispersed Cu2+species was increased after the modification by Mn2O3. TPR revealed that the interaction between Cu2+and Mn3+enhanced the reducibility of Mn species, thus the two reduction peaks were attributed to well-dispersed copper and manganese oxides species and crystal copper oxide, respectively. After calculation of the reduction peak area, we found that all the CuO species were reduced to Cu atoms, and Mn2O3species were reduced to MnO in the temperature range of100～400℃. Through in-situ FT-IR tests, catalysts showed various CO absorbtion/desorbtion abilities, which might be related to the reducibility of catalysts.Furthermore, the model reaction of CO+O2tests showed that, modification of γ-Al2O3by Mn2O3promoted activities of CuO/γ-Al2O3catalysts. Considered about the TPR、FTIR conclusions, we found that the activities of catalysts were in good line with the reducibility of well-dispersed copper and manganese oxides species.Part Ⅱ Catalysts were prepared by impregnation of vanadium oxide or nickel oxide onto the modified support Mn2O3/γ-Al2O3. Then the catalysts were characterized by XRD, H2-TPR, in-situ FT-IR and activity test for NO+CO model reaction. Vanadium oxide or nickel oxide supported on pure γ-Al2O3were also prepared and characterized for reference.In the test of NO+CO model reaction, all the single loaded catalysts (03VAl,03NiAl,03MnAl), as well as03V03MnAl, showed low activities, whether or not it was pretreated in CO atmosphere. However,03Ni03MnAl sample showed very good activity in the model reaction, and became even better after CO pretreatment.XRD results showed that03V,03Mn, and03Ni could disperse well on the surface of γ-Al2O3, but when both03V and03Mn loaded onto the support together, mixed oxide Mn2V2O7formed, which is hard to reduce according to the TPR results. On the other hand, the interaction between Ni species and Mn species improved the reducibilities of each other significantly, which could probably be one of the important reasons for the high activity of03Ni03MnAl catalyst.FTIR tests of NiMnAl catalysts revealed that NO species, but CO species, could absorbe onto both vanadium and nickel species. And the absorbed states of NO species on03NiAl and03MnAl did not change after CO pretreatment. However, the absorbing peak of NO species on03Ni03MnAl decreased a little after CO pretreatment, which might be attributed to the reduction of metal species to a lower valence.