| Volatile Organic Compounds is the most common pollutants in the human activities, which cause serious damage to the ecological environment and great harm to human health. Catalytic combustion is one of the best methods to control VOCs. The key of treatment for VOCs is preparation of high efficient catalyst. In this dissertation, a series of II-manganese oxide octahedral molecular sieve(OMS-2) modified by Cu and/or Ag have been prepared for o-xylene catalytic combustion. The main results are as follows:(1) 0.025Cu-OMS-2-400 was prepared through simultaneous reduction method: namely, Cu2 O is prepared by propanal and Fehling reagent, at the same time OMS-2 was synthesized using KMn O4 and propanal as reactants. For comparison, 0.025Cu/OMS-2-400 was also prepared by immersion method. The results of catalytic activity show that T100(the temperature at which the yield of CO2 was 100%) of both OMS-2 and 0.025Cu-OMS-2-400 was 200℃, while T20(the temperature at which the yield of CO2 was 20%) of 0.025Cu-OMS-2-400 was 147℃, which was down 36℃ than OMS-2. T100 and T20 of 0.025Cu/OMS-2-400 were 210℃ and 180℃ respectively. The results indicated that using simultaneous reduction method is benefit to improve the low-temperature catalytic activities. XPS results showed that 0.025Cu-OMS-2-400 contains Cu+ and Cu2+ mixture. However XRD analysis demonstrated that 0.025Cu-OMS-2-400 displayed the same crystal structure as that of OMS-2. This results illustrated Cu species may be highly dispersed in the lattice space of OMS-2 by simultaneous reduction method. SEM results showed tetragonal nanoparticles of 0.025Cu-OMS-2-400. BET results showed that surface area of 0.025Cu-OMS-2-400 was 164m2/g. The tests of H2-TPR and O2-TPO confirmed that lattice oxygen mobility and reoxidation ability of 0.025Cu-OMS-2-400 had a better performance. The above results demonstrated that the active sites of Cu2 O is slightly more favorable for O2 adsorption. Cu+ in 0.025Cu-OMS-2-400 could increase the exchange of Mn4+/Mn3+, which facilitated the conversion of o-xylene into CO2 and H2 O. A series of Cu-doped catalysts ACu-OMS-2-B-C was prepared through simultaneous reduction method, where A, B, C stand for molar ratio of Cu/Mn, concentration of Cu(NO3)2 solution, and calcination temperature respectively. In the activity of catalytic oxidation of o-xylene tests, 0.025Cu-OMS-2-0.05-400 reach the best catalytic activity.(2) From the(1) results we can see that 0.025Cu-OMS-2-400 could only inprove the low-temperature catalytic activities. Therefore, further research of 0.025Cu-0.02Ag-OMS-2-400 is crucial and necessary. The results of catalytic activity show that T100 and T20 of 0.025Cu-0.02Ag-OMS-2-400 was 180℃ and 119℃ respectively, which decreased 20℃ and 28℃ compared with 0.025Cu-OMS-2-400. It can be seen that Ag species could inprove the catalytic activity at both high and low-temperature. XPS datas confirmed that Cu+, Cu2+, Ag0 and Ag+ contained in 0.025Cu-0.02Ag-OMS-2-400 simultaneously. However, XRD results showed that there was no diffraction peaks of Ag and Cu. It was speculated that Ag species may be highly dispersed in the lattice structure of OMS-2 to form Ag-O-Mn bonds. SEM results showed rhombus nanoparticles of 0.025Cu-0.02Ag-OMS-2-400. BET results showed that surface area of 0.025Cu-0.02Ag-OMS-2-400 was 178m2/g. The results of H2-TPR and O2-TPO showed that lattice oxygen mobility and reoxidation ability of 0.025Cu-0.02Ag-OMS-2-400 had a better performance. These results indicated that the synergistic effect of Ag and Cu increased both the high and low temperature catalytic activity of OMS-2. XCu-YAg-OMS-2-Z was prepared from two aspects to chang the preparation conditions by simultaneous reduction method. X, Y, Z stood for molar ratio of Cu/Mn, molar ratio of Ag/Mn, and amount of propanal in reaction respectively. In the activity of catalytic oxidation of o-xylene tests, T100 and T20 of 0.025Cu-0.02Ag-OMS-2-400 was 180℃ and 119℃ respectively which achieve the best catalytic activity. |
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