Cr-MnO_x/TiO_2-ZrO_2低温选择催化还原NO的活性及抗毒性能  

Activity and antitoxic properties of Cr-MnO_x/TiO_2-ZrO_2 for low-temperature selective catalytic reduction of NO

作　　者：李哲[1] 汪莉[1,2] 贠丽 王振南[1] 李梦霞[1] 李鑫[1] 

机构地区：[1]北京科技大学土木与环境工程学院,北京100083 [2]北京科技大学金属矿山高效开采与安全教育部重点实验室,北京100083

出　　处：《工程科学学报》2015年第8期1049-1056,共8页Chinese Journal of Engineering

基　　金：科技部纳米重大科学研究计划资助项目(2013CB932600)

摘　　要：采用溶胶凝胶法制备TiO2-ZrO2载体,然后采用柠檬酸溶液浸渍法制备Cr-MnOx/TiO2-ZrO2复合催化剂.通过X射线衍射、比表面积测试(BET)、扫描电镜、X射线光电子能谱等测试方法对催化剂的物化性能进行表征分析,并进行NH3选择性催化还原NO实验,考察催化剂在低温下的活性及抗硫抗水性能.Cr元素介入到MnOx中,形成了新型的CrMn1.5O4活性物相,其中的Mn元素多以Mn3+和Mn4+存在.高价态的Cr5+使Mn元素由Mn3+向高氧化态的Mn4+转化,有利于低温选择性催化还原反应的进行.鉴于Cr元素第一电离能和电负性均低于Mn元素,能优先于Mn与SO2-4和SO2-3结合,保护MnOx不被硫酸化,从而提高Cr-MnOx/TiO2-ZrO2催化剂的抗毒性能.制备的五种不同Cr/(Cr+Mn)摩尔比的催化剂中,Cr(0.4)-MnOx/TiO2-ZrO2的性能最优,其颗粒分散均匀,具有较大比表面积,在180℃时脱硝效率能够达到95.8%,同时通入5%H2O和10-4SO2,脱硝效率缓慢下降,反应8h后,下降到73%,并保持稳定.Using a sol-gel prepared TiO2-ZrO2 carrier,Cr-MnOx/ TiO2-ZrO2composite catalysts were synthesized by a critic acid solution impregnation method. The physical and chemical properties of the catalysts were characterized by X-ray diffraction,specific surface area determination（ BET）,scanning electron microscopy and X-ray photoelectron spectroscopy. Meanwhile,the lowtemperature catalytic activity and the sulfur and water resistance were evaluated with selective catalytic reduction（ SCR） of NOby NH＋3. The introduction of Cr element to MnOxyields a new CrMn1.5O4 active phase,in which Mn primarily exists as Mn3 and Mn^4＋.The Cr^5＋ valence state facilitates the transformation of Mn^3＋ to high oxidation state Mn^4＋,which is beneficial to the low temperature SCR reaction. Because of lower first ionization energy and electronegativity,Cr preferentially reacts with SO2-4and SO2-3than Mn,thus protecting MnOx not to be sulphatized and resulting in the enhanced antitoxic performance of Cr-MnOx/ TiO2-ZrO2. Among the prepared five catalysts with different molar ratios of Cr /（ Cr ＋ Mn）,Cr（ 0. 4）-MnOx/ TiO2-ZrO2 demonstrates the best performance owing to the largest surface area and the best particle dispersion,and a 95. 8% denitrification efficiency can be achieved at 180 ℃.When 5% H2O and 10-4SO2 are simultaneously added,the denitrification efficiency decreases slowly and stabilizes at 73% after 8h reaction.

关 键 词：氧化物 催化剂 选择性催化还原 一氧化氮 活性 

分 类 号：X511[环境科学与工程—环境工程]