Research On Denitration And Synergitic Mechanism Of Mn-Ce Nano-Catalyst

Serious environmental problems attracted more attention in the past few decades. Nowadays, increasingly stringent pollutant emission standard is putting forward a higher requirement for Air Pollution Control. The V2O5-based catalyst, which is most widely used in denitration unit, can`t meet the new requirement of new catalyst performance and the optimal active temperature, and it`s necessary to develop new denitration technology and new catalyst. In this paper, the new catalyst was prepared from two aspects. Firstly, nanostructure was introduced to improve the microstructure of catalyst. Secondly, MnOx and CeO₂, which are the greatest potential active agents, were introduced to improve catalytic activities.Firstly, nano-CeO₂ was prepared by hydrothermal method. CeO₂ nanoparticles and nanorods were successfully prepared after multiple correction experiments. Influence of the nano-CeO₂ texure on catalytic performance was studied in this paper, where commercial CeO₂ as the reference. The results showed that, the smaller the particle was, the higher catalytic activities it showed, but the easier to deactivate at high temperature. The BET results showed that nanostructure could enlarge specific surface area, but most of pores are micropore?1-2nm?, which have no obvious effects on improving catalytic activity. The test results of XPS?NH₃-TPD and SEM showed that there are more acid sites and adsorbed oxygen on the surface of CeO₂ nanorods. CeO₂ nanorods showed the highest catalytic activity at the temperature below 350 oC due to its more activated molecule. However, smaller particles could lead to deactivation easier at high temperature.Secondly, the effect of Mn-loading on catalytic activity was studied. Mn was loaded on nano-CeO₂ by hydrothermal method, which KMnO4 was added as the precursor. The test results of SEM and TEM showed that CeO₂ was besieged by Mn, resulting in the increasing of particle size, pore diameter, and the specific surface area, which improved the catalytic activity in some extent. As the support, CeO₂ maintain the same during the load experiment. MnOx which loaded on the surface of catalyst, have a well-ordered lamellar and the valence contained +2?+3 and +4. It showed high catalytic activity at low temperature, but easier deactivation at high temperature. Mn-Ce nanorods performed higher activity with the increase of MnOx loading amount on surface.Finally, comparing the experimental results of the catalytic activity of Mn-Ce catalyst, CeO₂ catalyst and MnOx, synergistic reaction mechanism of MnOx and CeO₂ was proposed. According to the results, Mn-Ce catalyst performed the best catalytic activity, in the order as follows: Mn-Ce > Mn Ox > CeO₂, due to their synergetic promotion. The results of TG profiles also provide the synergy evidence between MnOx and CeO₂. The synergistic mechanism of MnOx and CeO₂ over Mn-Ce catalyst could be described as follows. As the active substance, MnOx could promote denitration process by circulation redox itself. As the promotor, CeO₂ could speed up the catalytic reaction by oxidizing MnOx due to its high oxygen storage and adsorbed oxygen conversion capacity.