Promotion effect of tungsten oxide on SCR of NO with NH3 for the V2O5–WO3/Ti0.5Sn0.5O2 catalyst: Experiments combined with DFT calculations
Promotion effect of tungsten oxide on SCR of NO with NH3 for the V2O5–WO3/Ti0.5Sn0.5O2 catalyst: Experiments combined with DFT calculations
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DOI：
10.1016/j.molcata.2011.06.004
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发表时间：
2011-07
影响因子：
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通讯作者：
Chuanzhi Sun;Lihui Dong;Wu Yu;Lichen Liu;Hao Li;F. Gao;Lin Dong;Yi Chen
中科院分区：
文献类型：
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作者：
Chuanzhi Sun;Lihui Dong;Wu Yu;Lichen Liu;Hao Li;F. Gao;Lin Dong;Yi Chen
采用XRD、LRS、TPR、NH3- tpd、原位FT-IR以及NH3脱除NO的微反应器试验等手段，对Ti0.5Sn0.5O2（以下简称TS）催化剂上负载的v2o5 - wo3二元金属氧化物进行了表征。结果表明：(1)负载量≤0.5mmol/100m2TS的氧化钒和氧化钨在TS载体上高度分散；(2)钒种的还原温度由于V-O-W键的形成而升高。(3)随着wo3负载量的增加，Brønsted酸位点数量增加，Lewis酸位点数量减少。密度泛函理论（DFT）的计算结果进一步证明了Brønsted酸位的强度受钨种类的影响较小。添加wo3后，对NO的吸附变化不大。进一步增加WO3（负载≥1.0mmol/100m2TS）会形成结晶WO3，并覆盖催化剂表面的氧化钒。(4)“NO+NH3+O2”反应活性与Brønsted酸位的数量密切相关，当wo3高度分散时，Brønsted酸位的数量越多，SCR活性越高。当wo3结晶形成时，它们覆盖在催化剂表面，导致活性降低。
Binary metal oxides V2O5–WO3supported on Ti0.5Sn0.5O2(hereafter denoted as TS) catalysts have been characterized by XRD, LRS, TPR, NH3-TPD, in situ FT-IR and the micro-reactor test for the removal of NO by NH3. The results suggest that: (1) both vanadium oxide and tungsten oxide (loadings ≤0.5mmol/100m2TS) are highly dispersed on TS support. (2) The reduction temperature of vanadium species becomes higher due to the formation of the V–O–W bonds. (3) With the loading amounts of WO3increasing, the amounts of the Brønsted acid sites increase, while the amounts of Lewis acid sites decrease. The strength of Brønsted acid sites is little influenced by the tungsten species which is further proved by the density functional theory (DFT) calculation results. The adsorption of NO is little changed after WO3addition. Further increase of WO3(loadings≥1.0mmol/100m2TS) results in the formation of crystalline WO3and they will cover the vanadium oxide species on the surface of the catalysts. (4) The activity of “NO+NH3+O2” reaction is tightly related to the amounts of the Brønsted acid sites: the higher SCR activities should be attributed to the larger amounts of Brønsted acid sites when WO3are highly dispersed. When the crystalline WO3form, they cover the surface of the catalysts, and lead to the decrease of the activities.