蜂窝状Ti0.14Mn0.86Ox/CH催化剂的制备及其低温NH3-SCR脱硝性能
Preparation and investigation of Ti0.14Mn0.86Ox/CH monolithic catalysts for low-temperature NH3-SCR
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摘要: 采用自蔓延高温合成法（SHS）以堇青石蜂窝陶瓷（CH）为基体制备了一系列Ti1-yMnyOx/CH整体式催化剂，应用于柴油车尾气氮氧化物净化.考察了制备参数（钛锰比、涂覆次数、点燃温度）和工况条件（空速，水蒸气）对催化剂低温SCR（选择性催化还原）脱硝活性的影响，采用X射线荧光光谱仪（XRF）、场发射扫描电镜（FE-SEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）、比表面积（BET）等表征手段对催化剂的结构和形貌进行表征.结果表明，在Ti：Mn=1：6（物质的量之比），一次涂覆，点燃温度为350℃条件下所制备的催化剂具有最佳的NH3-SCR脱硝活性，Ti0.14Mn0.86Ox/CH催化剂在空速为30000 h-1，氧气含量为3 vol%反应温度为150-250℃时反应条件为最优，催化剂在150℃以上具有良好的耐水性.Ti元素的添加提高了催化剂表面Mn4+/Mn3+比例，并使MnOx呈无定形态均匀分散在Ti0.14Mn0.86Ox/CH催化剂表面，提高催化剂的低温SCR活性.Abstract: Cordierite honeycomb ceramics (CH) as catalysts' carrier were prepared by self-propagating high-temperature syntheses method (SHS) to obtain a series of Ti1-yMnyOx/CH catalysts for diesel exhaust purification. The effects of the preparation parameters (Ti/Mn ratio in the combustion solution, times of coating, ignition temperature) and operation conditions (space velocity and H2O) on performance of the monolith catalysts for the NH3-SCR were also investigated. The catalysts were characterized by BET, XRF, XRD, FESEM and XPS. It was observed that the catalysts ignited at 350℃ once with Ti/Mn=1:6 in the combustion solution showed the optimal NH3-SCR activity when tested at 150-250℃ with NH3/NO ratio at 1, gaseous hourly space velocity(GHSV)=30000 h-1and 3vol% O2. The catalyst showed excellent H2O tolerance when temperature was above 150℃. Addlition of Ti in the combustion solution increased Mn4+/Mn3+ ratio and improved uniform distribution of amorphous MnOx on the surface of the catalysts, which are benefit for the NH3-SCR activity of the catalysts.
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