Nb改性对MnCe0.2Ox低温SCR抗硫和水热稳定性能的影响

Promotional effects of niobium on sulfur resistance and hydrothermal stability of MnCe0.2Ox catalysts for SCR at low temperatures

采用均相沉淀法制备系列Nb掺入MnCe0.2Ox低温烟气脱硝催化剂,对比研究MnCe0.2Ox和MnNbβCe0.2Ox催化剂NH3选择性催化还原(NH3SCR)性能、水热稳定性能和抗硫中毒性能,同时考察NH3SCR反应中NOx、NH3和SO2的分子迁移过程。结果表明:MnNb0.4Ce0.2Ox催化剂在180℃时NOx脱除效率达到98.5%。通入SO2和H2O 20 h后,NOx脱除效率仍然达到80%。此外,400℃水热老化24 h后,MnNb0.4Ce0.2Ox在180℃时NOx脱除效率仍然达到97%。Nb掺入增加了MnCe0.2Ox催化剂的比表面积,促进了Lewis酸的增加,并增强了氧化还原性能。在SO2和H2O存在时,Nb的掺入可以有效抑制MnNb0.4Ce0.2Ox表面SO2的吸附和硫氨盐的形成。同时,Nb与Mn和Ce之间的相互作用,也使得MnNb0.4Ce0.2Ox的结构稳定性得到增强。

A series of Nb doped MnCe0.2Ox low-temperature flue-gas denitrification catalysts were prepared by the homogeneous precipitation method for NOx removal.The selective catalytic reduction of NH3(NH3-SCR)performance,hydrothermal stability and sulfur resistance performance of MnCe0.2Ox and MnNbβCe0.2Ox catalysts were studied.Moreover,the molecular migration process of NOx,NH3 and SO2 in the NH3-SCR reaction were also investigated.Results showed that the NOx removal efficiency of MnNb0.4Ce0.2Ox catalyst reached 98.5%at 180℃.After the introduction of SO2 and H2O for 20 h,the NOx removal efficiency still reached 80%.In addition,after hydrothermal aging at 400℃for 24 h,the NOx removal efficiency of MnNb0.4Ce0.2Ox still reached 97%at 180℃.The doping of Nb increased the specific surface area of the MnCe0.2Ox catalyst,promoted the increase of Lewis acid and enhanced the redox performance.In the presence of SO2 and H2O,the doping of Nb could effectively inhibit the adsorption of SO2 on the surface of MnNb0.4Ce0.2Ox and the formation of sulfate.At the same time,the interaction between Nb,Mn and Ce also enhanced the structural stability of MnNb0.4Ce0.2Ox.