Study On The Preparation, Performance And Its Mechanism Of Low-temperature SCR Catalysts Loaded N-doped TiO₂

Low-temperature SCR catalysts have been one of hot researches in the chemical industry and environmental protection fields, because the catalysts are placed downstream coal burning boiler desulfuration and dust removal to effectively avoid the dangers of high concentrations of soot. Scholars in the photocatalytic field generally believe that the N-doped TiO2sample produces more oxygen vacancies (Vo). Oxygen vacancies are very important for the low-temperature SCR reaction. Therefore, this paper focuses on the performance and the mechanism of the N-doped TiO2sample as the support of low-temperature SCR catalysts.We synthesized the N-doped TiO2support by the sol-gel method, and employed it as a novel support to prepare V2O5and MnOx single component catalyst by the excess impregnation in this paper. We measured the low-temperature SCR activity of the catalysts and found that N doping both helped the two single-component catalysts improve their catalytic activity, particularly when N doping was1%, the catalyst had the highest activity. We also investigated process conditions of the catalyst to get the optimization conditions in the paper, and found that the two single-component catalysts both have the better catalytic activity under the reaction conditions of GHSV28000h-1,[NH3]/[NO]1.2,3vol%O2and the carrier calcination temperature500℃. In addition, the effects of H2O and SO2on the catalytic activity were investigated, found that the N-doped supported MnOx catalyst has low resistant to SO2and H2O, but the N-doped supported V2O5catalyst had better resistance to SO2and H2O.On the basis of the above research, we deeply studied the N-doped supported V2O5catalyst with better resistance to SO2and H2O by some characterizations. We had adopted XRD, SEM, TEM, BET, PL, XPS and EPR characterization methods to study the modified mechanism of N-doped improving the catalytic activity. N successfully doped into TiO2lattice by the sol-gel method, and N doping caused no significant change in the physical structure of the catalyst, but it caused significant chemical changes-increasing more oxygen vacancies on the surface of the catalyst. More oxygen vacancies captured electrons of NH3, then adsorbed oxygen to generate superoxide radical (O2-).Superoxide radical with strong oxidization could react with NO to form nitros (NO3-) and nitrates (NO2) species that were important intermediates in the low-temperature SCR process. N doping promoted the catalyst activity at low temperature by increasing the oxygen vacancies. However, N doping was not the more the better. When N doping was1.5%, the activity of the catalyst didn’t higher than that with the N-doped amount of1.5%., which may be that excessive N doping caused some N atoms acted as recombination centers and reduced electrons in the surface of catalyst, resulting in part of the electron cannot be captured by oxygen vacancies and eventually leaded to reduced superoxide radicals and decreased the catalytic activity of the catalyst.