Selective Catalytic Reduction of NOx with NH3 over Mn, Ce Substitution Ti0.9V0.1O2-δ Nanocomposites Catalysts Prepared by Self-Propagating High-Temperature Synthesis Method
Selective Catalytic Reduction of NOx with NH3 over Mn, Ce Substitution Ti0.9V0.1O2-δ Nanocomposites Catalysts Prepared by Self-Propagating High-Temperature Synthesis Method
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DOI：
10.1021/jp112283g
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发表时间：
2011-07-07
影响因子：
3.7
通讯作者：
Huang, Zhen
中科院分区：
文献类型：
--
作者：
Guan, Bin;Lin, He;Huang, Zhen
本研究以提高钒系催化剂的低温性能为目标，采用自蔓延高温合成方法合成了一系列Ti0.9VxM0.1-XO2-Delta催化剂。程序升温反应考察了Ti0.9V0.1O2-Delta、Ti0.9Mn0.05V0.05O2-Delta和Ti0.9Ce0.05V0.05O2-Delta催化剂的性能，结果表明，这些纳米SHS催化剂在150-400℃的宽温区内具有较高的活性。与Ti0.9V0.1O2-Delta催化剂相比，Ti0.9Mn0.05V0.05O2-Delta和Ti0.9Ce0.05V0.05O2-Delta催化剂在高温下表现出更高的N-2选择性。Ce取代催化剂在低温下表现出良好的抗H2O和SO2中毒性能。采用BET、X射线衍射、傅立叶变换红外光谱、透射电子显微镜、EDX、XPS和TPD等手段对催化剂的结构和物化性能进行了综合表征。X射线衍射结果表明，V、Mn、Ce的活性组分在催化剂上高度分散。在低温下，Mn的取代可以提高催化剂表面的Bronsted酸中心，加速SCR反应。XPS分析表明，Ce取代导致了较高的化学吸附氧浓度，从而减少了NH3被O-2非选择性氧化为N2O、NO或NO2，从而获得了较好的N-2选择性。催化剂的活性组份V、Mn、Ce主要以混价形式存在，有利于将NO氧化为NO2。此外，还用原位漂移法研究了Ti0.9Ce0.05V0.05O2-Delta催化剂上的SCR反应机理。结果表明，高活性的单齿硝酸盐和桥联硝酸盐物种以及丰富的离子NH4+(Bronsted酸位)是SCR反应的关键中间体，因为在NH3存在下，非单齿硝酸盐和桥联硝酸盐物种很快消失。
This study focuses on promoting the low temperature performance of vanadium-based catalysts; for this, the SHS method was applied to synthesize a series of Ti0.9VxM0.1-xO2-delta catalysts. The performances of the catalysts (Ti0.9V0.1O2-delta, Ti0.9Mn0.05V0.05O2-delta, and Ti0.9Ce0.05V0.05O2-delta), were fully investigated with the temperature-programmed-reaction, which proved that these SHS catalysts with nanometer size had high activity over a broad temperature window of 150-400 degrees C. Compared with Ti0.9V0.1O2-delta, the substituted Catalysts, Ti0.9Mn0.05V0.05O2-delta and Ti0.9Ce0.05V0.05O2-delta, showed higher N-2 selectivity at high temperatures. The Ce substituted catalyst exhibited good resistance to H2O and SO2 poisoning at low temperatures. The structural and physical-chemical properties of catalysts were characterized comprehensively by BET, XRD, FTIR, TEM, EDX, XPS, and TPD. The XRD results indicated that the active components of V, Mn, and Ce were highly dispersed over the catalysts. The Mn substitution could enhance the Bronsted acid sites on the catalyst surface and accelerate the SCR reaction at low temperatures. The XPS shows that the Ce substitution led to high concentration of chemisorbed oxygen, which diminished the unselective oxidation of NH3 by O-2 to N2O, NO, or NO2 and resulted in superior N-2 selectivity. The active components of the catalysts, such as V, Mn, and Ce, mostly existed in the form of mixed-valence which was beneficial for the oxidation of NO to NO2. Furthermore, the SCR reaction mechanism over Ti0.9Ce0.05V0.05O2-delta catalyst was also examined using in situ DRIFTS. The results revealed that high active monodentate,e nitrate and bridging nitrate species as well as abundant ionic NH4+ (Bronsted acid sites) were the key intermediates in the SCR reaction since the ad-monodentate nitrate and bridging nitrate species disappeared quickly in the presence of NH3.