氧化还原沉淀法制备MnO_2/MWCNTs催化剂及其低温SCR活性

Preparation of MnO_2/MWCNTs Catalysts by a Redox Method and Their Activity in Low-temperature SCR

先用十二烷基硫酸钠（SDS）对多壁碳纳米管（MWCNTs）进行表面改性，然后采用氧化还原沉淀法制得一系列的Mn02／MWCNTs催化剂。考察了催化剂在80—180℃的选择性催化还原（scR）反应活性，并通过BET、XRD、FESEM、TEM、XPS和H2-TPR等表征手段对催化剂的结构及性能进行分析。结果显示，Mn02／MWCNTs催化剂在空速210L／（gcat·h）和温度140-180℃条件下，脱硝效率达到85％～100％，这明显优于等体积浸渍法制备的催化剂的低温SCR催化活性，且10％MnO2／MWCNTs催化剂的活性最优。分析结果表明，MnO2／MWCNTs催化剂中MnO2以纳米片状均匀分散在多壁碳纳米管载体表面；弱结晶性的结构和高价锰，较高的表面吸附含氧量及较强的低温区氧化还原能力是10％Mn02／MWCNTs催化剂具有优异低温SCR活性的原因。另外，和MnOx／MWCNTs催化剂相比，10％MnO2／MWCNTs催化剂表现出良好的抗水和抗硫性能。

Pristine multiwalled carbon nanotubes （MWCNTs） were modified by sodium dodecyl sulfate （SDS）. Afterwards, a series of MnO2/MWCNTs were prepared via a redox method and used in selective catalytic reduction （SCR） of NOx at 80-180℃. Structural properties and catalytic performance were investigated by specific surface area measurements （BET）, X-ray diffraction （XRD）, filed emission scanning electron microscope （FESEM）, transmission electron microscope （TEM）, X-ray photoelectron spectroscope （XPS）, and H2 temperature-programmed reduction （H2-TPR）. The characterization results indicate that the nanoflaky MnO2 highly disperse on MWCNTs. The results show that the low-temperature SCR activities of MnO2/MWCNTs catalysts are 85%-100% at 140-180℃ at a weight hourly space velocity of 210 L/（gcat·h）, higher than that of catalyst fabricated via the wet impregnation method. The 10% MnO2/MWCNTs catalyst displays first-rate SCR activity, which is attributed to its low crystallinity, high concentrations of Mn4＋ and oxygen absorbtion onto the catalyst surface, as well as excellent reducibility. Additionally, compared to the MnOx/MWCNTs catalyst, the 10% MnO2/MWCNTs catalyst exhibits higher resistance to H20 and S02.