摘要
采用高温固相反应法、Pechini合成方法和柠檬酸配位法，制备了系列锂锰复合氧化物LiMn2 O4催化剂，应用于NH3-SCR反应，并与固相反应法合成的MnO2进行了比较。采用N2吸附-脱附、扫描电镜、X射线衍射、H2程序升温还原、NH3程序升温脱附、NO程序升温脱附和X射线光电子能谱对LiMn2 O4催化剂进行表征。结果表明，引入Li有利于提高锰基催化剂的SCR活性和抗硫性。 Pechini法制备LiMn2 O4的NO转化率可在130～260℃达到90％以上；固相反应法制备LiMn2 O4的NO转化率大于90％的温度为90～310℃；MnO2的温度窗口则仅为140～280℃。与MnO2相比，引入Li可形成LiMn2 O4结构，因此，催化剂中更多的锰离子保持在相对较低的价态Mn3＋，并调整表面活性氧含量；同时，Li的存在调变了LiMn2 O4表面的酸位，从而减少高温下MnO2表面容易发生的NH3非选择性氧化，改善其催化NH3-SCR反应的温度窗口，也增强了抗硫性。
LiMn2 O4 prepared by high temperature solid state reaction, pechini, and cirt ic acid coordination methods was applied in selecit ve catalytic reduction （S CR ） of NO with NH3 . MnO2 prepared by high tem perta ure solid state reaction method and the activity was tested as a comparsion.T he catalysts were characterized by N2 asd orption-desorptoi n, scanning electron microscopy, X-ray dfi fraction, H2 temperature-program med rde uction, NH3 temperature-pr ogrammed desorption, NO temperature-programmed desorption,a nd X-ray photoelectron spectroscopy. The results sho wed that high-temperature activiyt of SCR were im rp oved after teh introduction of Li into MnO2 .NO conv ersion on the LiMn2 O4 per ap red by pechinim ethod was above 90%in the range of 130~260℃;NO convre soi n on the LiMn2 O4b y high temperature solid state reatc ion mte hod could be kept ba ove 90%in the ar nge of 90~310℃;while the temep rature window of MnO2 was only 140~280℃. Comparedw ith MnO2 , LiMn2 O4 crystal structure not only keeps more manganese cait ons at a relatively low valence of Mn3＋, but also adjusts us raf ec a cit veo xgy ne. Mae nwhile, the existence of Li adjusts surface-acid sites of LiMn2 O4 , thus alleviates the unes lce itv e ox dia toi nof NH3 in the high temperature, broadens the operating temperature window of NH3-SCR reaction, and improves the catalyst tolerance of SO2 .
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2014年第12期1447-1454,共8页
Journal of Fuel Chemistry and Technology
