Study On Preparation And Denitration Performance Of Catalysts Of CoO_x-TiO₂ And CeO₂-TiO₂

At present, the selective catalytic reduction of NOx by NH3(NH3-SCR) is the most effective way to remove NOx in the flue gas of coal-fired power plant. V2O5-WO3/TiO2, applied widely in coal-fired power plant, is the commercial catalyst of denitration. The V-based catalysts could only applied in medium-high temperature working condition and be harmful to environment. Because of which, it’s necessary for us to develop the catalyst without vanadium species, and which could show higher low-temperature catalytic activity. In order to study the promote effects of oxygen vacancies for NH3-SCR reaction and further improve low-temperature catalytic activity, CoOx-TiO2 and CeO2-TiO2 catalysts were prepared by Sol-Gel and impregnation methods. The catalytic activities and catalytic mechanism were studied in the experiment.Catalysts Co-Ti-5 and Co/Ti-5 were prepared by Sol-Gel and impregnation methods, respectively. Catalyst Co-Ti-5 showed better DeNOx performance than that of catalyst Co/Ti-5. Combined with a series of methods of analysis and testing, some important conclusions were summed up. Results of XRD, XPS and PL indicated that Ti4+ were replaced by Co2+ in TiO2 lattice, and because of which more oxygen vacancies came into being on amount of charge compensation theory. And that oxygen vacancies would adsorb and activate oxygen to form more chemisorbed oxygen. Based on results of EPR spectra, more superoxide radicals(O2-) were produced on the surface of catalyst because of the doping of foreign species, and they could promote generating SCR intermediates, nitrate species, by reacting adsorbed NO. And that nitrate species could decompose to NO2 molecules with each other, therefore, further promote SCR reaction.Based on theoretical foundation of catalysts CoOx-TiO2, and in order to improving low-temperature activity of CeO2-TiO2 catalysts and further study the promotion mechanism of oxygen vacancies, catalysts Ce-Ti and Ce/Ti were prepared by Sol-Gel and impregnation methods in this study. The studies found that Ce-Ti showed better catalytic activity than that of Ce/Ti, and it showed more than 95% denitration efficiency at 240℃. Combined with some characterization methods, we found that the Ce-O-Ti structure was exited in catalyst Ce-Ti. XPS showed that Ce-Ti has more Ce3+ species and chemisorbed oxygen than that of Ce/Ti. Besides, PL and EPR results indicate that Ce-Ti catalyst contains much more Ce-□-Ti type oxygen vacancies. Ce-□-Ce and Ti-□-Ti type oxygen vacancies can’t effectively promote generating superoxide radicals, and only Ce-□-Ti type oxygen vacancies could effectively promote generating superoxide radicals, thus, which would further promote SCR reaction.