过硫酸铵氧化耦合过渡金属氧化物改性炭基催化剂低温SCR性能增强机制研究

Study on the enhancement mechanism of low-temperature SCR performance of ammonium persulfate coupled transition metal oxides modified carbon-based catalysts

本工作中利用过硫酸铵氧化耦合过渡金属氧化物改性制备V/OAC、Fe/OAC、Mn/OAC、Cu/OAC炭基催化剂,并通过催化活性测试和物理吸附-脱附、FT-IR、XPS、NH3-TPD、H2-TPR、EPR等表征手段探究改性炭基催化剂的低温SCR性能增强机制。结果表明,过硫酸铵氧化可向活性炭载体表面引入大量酸性含氧官能团,促进过渡金属氧化物中的氧空位形成,从而提升炭基催化剂的表面酸度和氧化还原性能,进而提升了炭基催化剂低温NH3-SCR性能。本工作发现,过硫酸铵氧化可诱导过渡金属元素(V、Fe、Mn、Cu)的低价态形成。因此,过硫酸铵氧化改性后,活性组分中低价态金属利于NH3-SCR反应的V/OAC、Fe/OAC催化剂性能提升显著,VOx/OAC和FeOx/OAC催化剂在100℃下的NO转化率分别从18.2%提升到34.8%和从34.2%提升到55.6%;而活性组分中高价态金属有利NH3-SCR反应的Mn/OAC和Cu/OAC催化剂性能提升有限,100℃下的NO转化率仅从61.4%提升到70.4%和61.3%提升到69.7%。本工作总结了过硫酸铵氧化改性对炭基催化剂表面金属价态的调控作用,有助于深入认识过硫酸铵氧化改性对炭基催化剂物化性质的调控规律,为高效炭基脱硝催化剂的开发提供指导和参考。

In recent years,carbon-based catalysts have received extensive attention in the field of NH3-SCR due to their unique advantages.In order to improve the performance of low-temperature NH3-SCR of carbon-based catalysts,V/OAC,Fe/OAC,Mn/OAC and Cu/OAC carbon-based catalysts were prepared by oxidizing and coupling transition metal oxides with ammonium persulfate.The mechanism of SCR performance enhancement of modified carbon-based catalysts was investigated by means of catalytic activity test,physical adsorption,FT-IR,XPS,NH3-TPD,H2-TPR,EPR and other characterization methods.The results show that ammonium persulfate oxidation can introduce a large number of acidic oxygen-containing functional groups to the surface of activated carbon support,promote the formation of oxygen vacancy in transition metal oxides,and improve the surface acidity and redox performance of carbon-based catalysts,therefore the low temperature NH3-SCR performance of the carbon-based catalyst was improved.In particular,we found that oxidation of ammonium persulfate can induce the formation of lower valence states of transition metal elements(V,Fe,Mn,Cu).Therefore,after oxidative modification of ammonium persulfate,the performance of V/OAC and Fe/OAC catalysts with low-priced metals in active components conducive to NH3-SCR reaction is significantly improved,the NO conversion of VOx/OAC and FeOx/OAC catalysts at 100℃increased from 18.2%to 34.8%and from 34.2%to 55.6%,respectively;while the performance of Mn/OAC and Cu/OAC catalysts with high-priced metals in active components conducive to NH3-SCR reaction is limited,the conversion of NO at 100℃only increased from 61.4%to 70.4%and from 61.3%to 69.7%.This work summarized the regulatory effect of ammonium persulfate oxidation modification on the surface metal states of carbon-based catalysts,which is helpful to deeply understand the regulation law of physical and chemical properties of carbon-based catalysts by oxidative modification of ammonium persulfate,and provide guidance and reference for the development of high-efficiency carbon-based denitrification catalysts.