| Selective catalytic reduction (SCR) is one of the most widely used methods of abatement of NOx.SCR at low-temperature can solve the issue of industrial catalyst getting erosion and impurity pollution by fly ash caused by SCR reactor usually placed before the electrostatic precipitator. It can also avoid catalyst poisoning and simplify the SCR system easily. Large study indicates that manganese has a good SCR activity at low-temperature. In this investigation, the preparation, characterization and pertinency of TiO2 nanotubes and MnOx/TiNT catalysts were studied. The SCR activity at low-temperature and influenced by H2O, SO2 were discussed. At the same time, the denitrification kinetics of MnOx/TiNT was researched. This will provide valuable reference gist to the application of SCR catalyst at low-temperature.Firstly, TiCO2 nanotubes were synthesized by hydrothermal method. TEM, BET, XRD, TG, Raman, FT-IR were used to characterize the morphology and structure of TiO2 nanotubes. The results showed that hydrothermal synthesized titanium nanotubes were amorphous titanate with disordered, layered hollow tubular structure and specific surface area of 369.89 m2·g-1. After 400℃calcination(denoted as TiNT), nanotube hollow tubular structure was still layered and typical structure changed to anatase TiO2 with lower BET of 280.61 m2·g-1. After 500℃calcination, the structure of nanotubes was gradually destroyed and BET decreased to 205.34 m2·g-1. After 700℃calcination, the tubular structure disappeared to nanorods and the crystal lattice changed to rutile phase, BET droped to 128.09 m2·g-1.Secondly, a series different MnOx loading of MnOx/TiNT were prepared by impregnated method. TEM, XRD, BET, PL, EPR, XPS showed that catalysts were anatase and all keeping tubular structure. Specific surface area was lower than TiNT because of loading MnOx. Manganese particles were highly dispersed on the wall of TiO2 nanotubes and without diffractive apex of MnOx.When MnOx loading exceeded 15%, a weak diffraction peak of MnO2 was found. The presence of oxygen vacancies on MnOx/TiNT catalysts could increase the amount of chemistry adsorption oxygen, which had a role of promoting the catalytic activity.Furthermore, under the reaction conditions of 150℃, [NH3]/[NO]=1.2, O2=3%, NO=0.06%, GHSV=23613.8 h-1, MnOx loading of 5%,10%,15%, the NO conversion rate of MnOx/TiNT was 95.3%,98.7%,98.2% respectively, which was higher than MnOx/TiO2 catalyst. The SCR activity of MnO×(5%)/TiNT catalyst decreased to 47.7% in the presence of H2O at 180℃, which caused by competion adsorption between H2O and reagent, but its activity could be recovered almost when cutting off H2O. The presence of SO2 could also deactivate the catalyst gradually, because of sulphate creating on the surface of TiNT. However, the catalyst exhibited better resistance by H2O+SO2 than H2O, activity of catalyst rised gradually after cutting off H2O+SO2, but couldnot recover to its initial level.Finally, the denitrification kinetics of MnOx/TiNT was studied. When O2 concentration was less than 1%, the reaction series of NH3 and NO were 0 and 1.2579 respectively. Reaction series of O2 was 1.0134. The impact on NO conversion rate could be ignored when O2 concentration was more than 1%. The reaction series of O2 was O. |
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