Preparation And Application Of MnCo₂ O₄ Spinel-type Complex Oxides

With increasing environmental awareness, the serious atmospheric pollution problem resulted from diesel-fueled vehicle emission is paid more and more attention, especially the effect of soot and NOx on human health is even not ignored. Conventional noble metal catalysts, although with high catalytic activity for the simultaneous removal of soot and NOx, are underutilized because of high price and scarce resource. So the new type of catalyst for diesel engine exhaust purification is urgently needed to be developed. Spinel oxide have unique structure and exhibite high catalytic activity for removal of soot and NOx.In the paper, a series of MnCo₂O₄ samples were prepared by solid state reaction method and sol-gel method. The effects of various synthetic conditions, the addition of different metal and the doping amount of metal were systematically studied on crystal structure and activity of catalyst by means of XRD, O₂-TPO, H₂-TPR, FI-IR and O2-TPD techniques. The catalytic activity of catalysts was evaluated using temperature programmed reaction on self-making reaction apparatus.MnCo₂O₄ oxides were prepared by solid state reaction method. The influence of the factors (molar ratio of glucose to total metal ions, grinding time, calcination time and calcination temperature) on structure and catalytic performance of the samples has been investigated. The results indicated that the catalyst had the best catalytic activity for soot combustion under the conditions of the molar ratio of glucose to total metal ions 0.6, grinding time 25min, calcination temperature 700oC and calcination time 4h.A number of MnCo₂O₄ samples were prepared via sol-gel method. The effect of molar ratio of glucose to total metal ions, aging temperature, calcination temperature and calcination time on structure and catalytic activity was also investigated, respectively. When the molar ratio of glucose to metal ions was 0.8, aging temperature 70oC, calcination temperature 700oC and calcination time 6h, the catalyst had the best catalytic activity for soot combustion. Compared with non-catalytical reaction, T₁₀, T₅₀, T₉₀ of soot fell by 199oC, 212 oC, 203oC, respectively.The catalysts were modified by doping different metal at A or B site. The effect of different metals and different doping amount on catalytic activity was also studied. The result showed Mn_0.6Ag_0.4Co₂O₄ catalyst prepared by sol-gel method has the highest activity for removal of soot and T₁₀, T₅₀, T₉₀ of soot is 250oC, 325oC, 373oC, respectively.