Ce改性对活化稀土尾矿催化剂NH3-SCR脱硝性能的影响

Effects of Ce Modification on NH3-SCR Denitration Performance of Activated Rare Earth Tailings Catalyst

白云鄂博稀土尾矿主要成分为赤铁矿、氟碳铈矿、萤石、石英和磁铁矿,其中稀土元素Ce和过渡金属Fe、Mn等是催化剂所需活性元素。本文利用浸渍法对活化稀土尾矿进行Ce改性,借助SEM-EDS、XRD、BET、NH_(3)-TPD、H_(2)-TPR、XPS等表征手段探究Ce改性对活化稀土尾矿催化剂性能的影响。结果表明,Ce改性活化稀土尾矿催化剂以介孔结构为主,Ce元素在催化剂表面高度分散;Ce元素与Fe元素之间存在协同作用,两者之间存在氧化还原电子对,促进了不同价态Ce、Fe离子之间的转化,增强了催化剂的氧化还原能力,提高了催化剂的酸性位点数量和酸性能,有利于NH_(3)的吸附与活化,从而使催化剂的脱硝效率提高。活化稀土尾矿经15%Ce改性后,脱硝效率由70%提升至82%,N_(2)选择性在90%以上,反应温度窗口拓宽至275~450℃。

Bayan Obo rare earth tailings are composed of hematite,bastnasite,fluorite,quartz and magnetite,in which rare earth element Ce and transition metals Fe,Mn are the active elements required for catalyst.In this paper,activated rare earth tailings were modified by Ce using impregnation method,and the effects of Ce modification on the performance of activated rare earth tailings catalyst were investigated by SEM-EDS,XRD,BET,NH_(3)-TPD,H_(2)-TPR and XPS.The results show that the Ce-modified activated rare earth tailings catalyst is dominated by mesoporous structure and Ce element is highly dispersed on the catalyst surface.There is a synergistic effect between Ce and Fe,and the existence of a redox couple between them promotes the transformation between different valence states of Ce and Fe ions,enhances the redox ability of the catalyst and increases the number of acid sites,which provides favorable environment for the adsorption and activation of NH_(3),improving the denitration efficiency of the catalyst.After being modified by 15%Ce,the denitration efficiency of the activated rare earth tailings increases from 70%to 82%,the N_(2)selectivity is above 90%,and the reaction temperature window is widened to 275~450℃.