Cu-TiO_(2)@CeO_(2)催化剂催化氧化NH_(3)/Hg^(0)

Catalytic oxidation of NH_(3)/Hg^(0)by Cu-TiO_(2)@CeO_(2)catalyst

为了减少SCR系统逃逸氨和气态单质汞的排放,采用模板法制备一系列具有氨氧化和汞氧化活性的Cu-TiO_(2)@CeO_(2)催化剂,在150—400℃下测试其氨氧化和汞氧化性能,并对其进行了XRD(X射线衍射)、BET(比表面积测试)和XPS(X射线光电子能谱)表征。结果表明:高温可以促进NH_(3)的氧化,但不利于保持高N 2选择性和Hg^(0)氧化效果。随着铜、铈质量分数的增加,催化剂的氨氧化和汞氧化活性均逐渐增加,而N 2选择性有所下降。其中Cu、Ce质量分数为5%的Cu-TiO_(2)@CeO_(2)-5催化剂可以达到较为理想的NH_(3)和Hg^(0)去除效果,350℃下对NH_(3)和Hg^(0)的氧化效率均高于90%,N 2选择性在95%以上,副产物N 2 O生成量低于5×10^(-6)。表征结果显示Cu-TiO_(2)@CeO_(2)催化剂中形成了Cu++Ce^(4+)Cu 2++Ce^(3+)氧化还原双电对,Cu与Ce的氧化物在NH_(3)和Hg^(0)氧化反应中起协同作用,大量的Oβ作为活性氧参与到反应中,有效促进了NH_(3)和Hg^(0)的催化脱除。

In order to mitigate the release of escaping ammonia and gaseous elemental mercury in the SCR system,a series of Cu-TiO_(2)@CeO_(2)catalysts with mercury and ammoxidation activities were synthesized using the template method.The ammoxidation and mercury oxidation properties were evaluated at 150-400℃,and the catalysts were characterized by XRD,BET and XPS.The results indicate that high temperature can enhance the oxidation of NH_(3)but is not favorable for maintaining high N 2 selectivity and Hg^(0)oxidation performance.With the increase of the mass fractions of Cu and Ce,the activities of ammonia oxidation and mercury oxidation of the catalyst gradually increase,but the selectivity of N 2 decreases.Among them,Cu-TiO_(2)@CeO_(2)-5 catalyst with 5%mass fractions of Cu and Ce can achieve ideal removal of NH_(3)and Hg^(0).At 350℃,the oxidation efficiencies of NH_(3)and Hg^(0)are both above 90%,the N 2 selectivity is above 95%,and the by-product N 2O formation is below 5×10^(-6).The characterization results show that Cu++Ce^(4+)Cu 2++Ce^(3+)redox double electric pair forms in the catalyst.The oxides of Cu and Ce act synergically in the oxidation reaction of NH_(3)and Hg^(0).A large amount of Oβparticipate in the reaction as active oxygen species,effectively promoting the catalytic removal of NH_(3)and Hg^(0)concentrations.