采用悬浮浆液法将凹凸棒石（ PG）涂覆于堇青石蜂窝陶瓷（ CC）基体上，制取PG?CC涂层载体，利用过饱和浸渍法负载MnOx制备MnOx／PG?CC催化剂应用于柴油车尾气SCR脱硝。考察了制备条件对催化剂低温SCR活性的影响，采用BET、SEM?EDS、XRD手段对催化剂的理化性质进行了分析表征，探讨了催化剂结构特性与活性间的构效关系。研究发现，堇青石基体经PG涂层后，对活性组分的一次负载量显著增加，由3％增至13％，对应的催化剂低温脱硝活性显著提高，在100℃脱硝活性由10％提高到78％。结果分析表明，堇青石基体经PG涂层后比表面积大幅度增加，可以承载更高的活性组分，且活性组分具有更好的分散性，从而使得催化剂的活性点增加；另一方面，PG涂层催化剂具有更高的表面Mn4＋／Mn3＋价态比，更有利于催化剂的低温选择性催化还原法（ SCR）活性。活性组分MnOx与PG涂层之间的协同作用是导致催化剂低温SCR脱硝活性得以提升的关键因素。研究结果表明，通过对堇青石蜂窝基体进行凹凸棒石涂层后采用浸渍法负载锰氧化物，可制备出具有较高低温SCR活性的蜂窝式模块催化剂。
Cordierite honeycomb ceramics ( CC) coated with Palygorskite ( PG) as catalysts′carrier were prepared by the method of immersing CC into a PG?water mixed slurry followed by calcination. The samples were loaded with manganese oxides by wet impregnation to obtain MnOx/PG?CC catalysts used for low temperature NO removal from exhaust gas of diesel engines. The dependences of catalyst′s performance on preparation conditions were investigated. The structure of catalysts were characterized by BET, SEM?EDS and XRD, thus the connections between catalyst′s structural and its SCR activity were discussed. Results showed that the loading amount of the active ingredient significantly increased from 3% to 13% after the PG coating, and the catalytic activity for NO conversion increased from 10% to 78% at 100 ℃. Significant rise in the catalysts′ surface area was observed after PG coating onto cordierite honeycomb ceramics, which led to the high loading and uniform dispersion of active manganese species on the coating carrier. Additionally, a distinct improvement in surface Mn4+/Mn3+ ratio was also detected. It was suggested that the synergistic interactions between PG and manganese oxides is the key reason for the excellent SCR performance of the catalyst at low temperatures. The method of PG coating followed by MnOx loading is effective for promoting the SCR performance of the Cordierite honeycomb ceramics.
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