Synthesis And Characterization Of Transition Metal Composite Oxide Catalysts

Chlorinated volatile organic compounds (Cl-VOCs) have an adverse effect on human health and the environment due to their acute toxicity, stability and strong bioaccumulation potential. Among the technologies for elimination of Cl-VOCs emissions, catalytic combustion is the most viable and economic approach for its low destruction temperature and its excellent selectivity toward the formation of harmless products. In this thesis, several series transition metal composite oxide catalysts were prepared for Cl-VOCs catalytic combustion, the effects of preparation methods and processes, ion doping, promoter modification on those properties and catalytic performances were investigated in detail.(1) Co3O4-CeO2/cordierite catalyst prepared by the sol-gel method presented high catalytic activity for catalytic combustion of o-dichlorobenzene (o-DCB), on which the degradation rate of o-DCB could almost reach to100%at350℃. However, its degradation rate was down to54%in the lifetime test at300℃after lasting for25h. The reason why the degradation rate diminished so much was probably due to the strong adsorption of C1and coking. By means of adding Mg, Li compound, it was found that the catalytic stability of Co3O4-CeO2/cordierite catalysts decreased due to the enhancement of interaction between the active substance and the support when the support modified by the Mg salt, while the active substance doped by Li was benefited for enhancing its catalytic stability.(2) A series of MnOx-MyOz (M=Ce, Fe) catalysts were prepared and characterized. The MnOx catalyst prepared by the sol-gel method presented high catalytic activity was contributed to manganese oxides as an active substance with a good dispersion. In addition, the good catalytic activity of MnOx-CeO2catalyst resulted from an enhancement of the specific surface area of manganese oxide species with an amorphous character nature after the introduction of Ce. What is more, the catalytic activity of MnOx remarkably improved by adding Ce and Fe together, which indicated that Ce and Fe together played a synergistic role. The degradation rate of o-DCB over Mn-Ce-Fe and Mn-Ce was up to98% and96%respectively, and their activity remained stable within6hours, which indicated that MnOx-MyOz(M=Ce, Fe) catalysts would have a promising application in the near future.(3) MOx-TiO2(M=Mn, Fe) catalysts were prepared by several methods, and the effects of the interaction between active composition and support on the catalysts were researched. The results indicated that MnOx/TiO2catalyst prepared by the sol-gel method dispersed well and had the largest specific surface area, which were in favor of the catalytic reaction.FeOx/TiO2catalysts were prepared by the sol-gel method, and the effects of calcination temperature and Fe/Ti mole ratio on their properties and catalytic performances were studied. The results showed the FeOx/TiO2catalyst with the Fe/Ti mole ratio of1:1and calcinated at400℃presented larger specific surface area, better dispersion and oxidation reactivity contributed to the best catalytic performance, the degradation rate of o-DCB could reached to92%at350℃. At the same time, both the Fe2TiO5produced at high temperature and the low content of Fe in FeOx/TiO2resulted in the poorer catalytic activity of catalysts. The researches could provide references for catalyst screening.