为研究具有良好活性的低温选择性催化还原催化剂,针对目前Mn基材料低温选择性催化还原脱硝催化剂研究的局限性,以超氧自由基促进光催化为理论基础,N掺杂改性非金属为研究思路,采用溶胶凝胶法及过量浸渍法制备了N掺杂MnOx/TiO2催化剂,用于锅炉烟气脱硝。提出了氧浓度、[NH3]/[NO]以及空速对脱硝效率的影响,结合X射线衍射表征,获得了N掺杂催化剂的反应工艺参数和相应的晶型变化特性。研究结果表明,N掺杂后,催化剂脱硝活性明显,并对催化剂N掺杂量、Mn负载量及催化剂煅烧温度进行了优化,并对优化结果进行分析。在此基础上,考察了含氧量,得出在O2浓度5%、[NH3]/[NO]为1.2时,空速28 000 h 1,反应温度180℃的条件下,掺N量为1%以及Mn负载量为5%的N掺杂MnOx/TiO2催化剂的脱硝活性稳定在90%左右。
TiO2 supports doped with different amounts of Si were prepared by a sol-gel method, and 1 wt% vanadia （V2O5） loaded on Si-doped TiO2 was obtained by an impregnation method. The mole ratio of Si/Ti was 0.2, NOx conversion exceeds 94% at 300℃ and GHSV of 41,324 hr-1 , which is about 20% higher than pure V2O5/TiO2 . The catalysts were characterized by XRD, BET, TEM, FT-IR, NH3-TPD, XPS, H2-TPR, Raman and in situ DRIFTS. The results of FT-IR and XPS indicated that Si was doped into the TiO2 lattice successfully and a solid solution was obtained. V2O5 active component could be dispersed well on the support with the increasing of surface area of the catalyst, which was confirmed by Raman and XRD results. Above all, the numbers of acid sites （especially the Br nsted-acid） and oxidation properties were enhanced for Si-doped V2O5/TiO2 catalysts, which improved the deNOx catalytic activity.
This study introduced TiO2-pillared clays （TiO2-PILC） as a support for the catalytic oxidation of NO and analyzed the performance of chromium oxides as the active site of the oxidation process. Cr-based catalysts were prepared by a wet impregnation method. It was found that the 10 wt.% chromium doping on the support achieved the best catalytic activity. At 350℃, the NO conversion was 61% under conditions of GHSV = 23600 hr^-l. The BET data showed that the support particles had a mesoporous structure. Hz-TPR showed that Cr（10）TiP （10 wt.% Cr doping on TiO2-PILC） clearly exhibited a smooth single peak. EPR and XPS were used to elucidate the oxidation process. During the NO ＋ O2 adsorption, the intensity of evolution of superoxide ions （O2^-） increased. The content of Cr^3＋ on the surface of the used catalyst was 40.37%, but when the used catalyst continued adsorbing NO, the Cr^3＋ increased to 50.28%. Additionally, Oα/Oβ increased markedly through the oxidation process. The NO conversion decreased when SO2 was added into the system, but when the SO2 was removed, the catalytic activity recovered almost up to the initial level. FT-IR spectra did not show a distinct characteristic peak of SO4^2-.
