Ni改性对稀土尾矿NH_(3) -SCR脱硝性能的影响

Effect of Ni modification on NH3-SCR denitrification performance of rare earth tailings

采用水热法制备不同比例Ni改性稀土尾矿催化剂,通过XRD、BET、H_(2)-TPR、NH_(3)-TPD和XPS等表征手段分析Ni改性对催化剂性能的影响.结果表明,Ni改性可明显提升稀土尾矿催化剂NO_(x)转化率,6%Ni/稀土尾矿催化剂的NO_(x)转化率在300℃时达到85%,N_(2)选择性在250~300℃的温度范围内可达到76%以上.改性后催化剂中生成了分散性较好的NiFe_(2)O_(4)物质,比表面积增至75.12m^(2)/g,催化剂的酸性位点增加,有利于催化剂表面吸附更多的氨气,Ni离子起到传递电子的作用,使得Fe^(2+)转化为Fe^(3+),Fe元素化学价态升高,铁离子最外层电子的不稳定性增加,氧化能力增强,有助于催化剂表面氨吸附物种的活化,有利于脱硝反应的进行.

Ni modified rare earth tailings catalysts with different proportions were prepared by hydrothermal method.The effects of Ni modification on the catalyst performance were analyzed by XRD,BET,H_(2)-TPR,NH_(3)-TPD and XPS characterization methods.The results show that Ni modification could significantly increase the NO_(x) conversion rate of rare earth tailings catalyst.The NO_(x) conversion rate of 6%Ni/rare earth tailings catalyst reached 85%at 300℃,the selectivity of N_(2) was over 76%in the temperature range from 250℃to 300℃.After modification,NiFe_(2)O_(4) with good dispersibility was generated in the catalyst,The specific surface area increased to 75.12m^(2)/g,the acidic sites of the catalyst increase,which is conducive to the adsorption of more ammonia on the catalyst surface,the Ni ions act as electron transporters,converting Fe^(2+)into Fe^(3+),the chemical valence of Fe increases,the instability of the outermost electrons of iron increases,the oxidation capacity increases,the enhanced oxidation capacity is conducive to the activation of ammonia adsorbed species on the catalyst surface and the denitrification reaction.