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载体形貌对钒钛SCR催化剂脱硝活性影响

发布时间:2018-04-18 18:23

  本文选题:选择性催化还原(SCR) + 钒钛基催化剂 ; 参考:《北京工业大学》2016年硕士论文


【摘要】:氮氧化物(NO_x)是大气主要污染物之一,对环境和人类健康都造成了严重的危害。选择性催化还原(SCR)技术具有脱除NO_x效率高(90%)和运行稳定等优点而成为世界脱硝市场的主流技术,其常用的SCR催化剂是V_2O_5-WO_3(MoO_3)/TiO_2体系。在这一催化剂体系中,TiO_2载体起着的重要的作用,因为它不仅具有优异的抗硫性能,而且具有良好的分散钒的能力。研究表明不同形貌或高暴露特殊晶面的TiO_2可能会导致其物理化学性质发生显著变化,如表面能、表面酸性,以及其与活性组分的相互作用等。具有特定形貌和表面结构的TiO_2在光催化和染料敏化太阳能电池等领域的应用已多有报道,并显示出独特的性质。然而,人们对TiO_2载体形貌对钛基SCR催化剂活性影响方面的认识还很有限。本论文在对比了工业TiO_2粉体性能的基础上,着重研究了TiO_2载体形貌对V_2O_5/TiO_2催化剂活性的影响。得到主要研究结果如下:1)比较了四种工业TiO_2粉体的性能的差异。以四种工业TiO_2作为载体,采用浸渍法制备相应的V_2O_5-MoO_3/TiO_2催化剂。通过SCR活性评价,发现具有圆形小球规整形貌的TiO_2-J载体所制备的催化剂具有更好的NO转化率。BET结果显示,TiO_2-J载体负载钒活性组分后,比表面积明显提高,而其他载体负载钒后,比表面积均呈下降趋势。从TPR和TPD结果发现,以TiO_2-J为载体的催化剂比其他催化剂具有更高的还原性和更多的酸性位。因此证明,TiO_2-J有良好的物理化学性质是可以提高催化剂SCR活性并拓宽反应温度窗口的良好载体。2)讨论了不同形貌载体TiO_2的可控制备方法。采用水热法,通过调节水合肼的浓度,得到具有规整八面体形貌的TiO_2,记作TiO_2-O,其主要暴露{101}晶面。通过添加HF封端剂,制备出扁平片状形貌的TiO_2,记作TiO_2-S,其主要暴露高能{001}晶面。3)考察了载体形貌对V_2O_5/TiO_2催化剂脱硝活性的影响。以TiO_2-O、TiO_2-S和商业TiO_2 P25为载体,由浸渍法制备了三个3 wt%V_2O_5/TiO_2催化剂。活性评价结果显示,负载在TiO_2-S上的V_2O_5/TiO_2-S催化剂,其NH_3-SCR催化活性最高。通过SEM、TEM、BET、H_2-TPR、Raman、NH_3-TPD、DRIFT、XPS等手段对所制备的催化剂进行物化性质表征。发现具有特殊结构的高能{001}晶面为主导晶面的TiO_2-S载体与活性组分之间存在较强相互作用,使钒物种在TiO_2表面良好地分散。进而造成V_2O_5/TiO_2-S催化剂具有较高的还原性和更多化学吸附氧,这可能是其具有良好NH_3-SCR反应活性的主要原因。
[Abstract]:Nitrogen oxide (NOX) is one of the main atmospheric pollutants, which has caused serious harm to the environment and human health.Selective catalytic reduction (NO_x) technology has the advantages of high NO_x removal efficiency and stable operation, and has become the mainstream technology in the world denitrification market. The commonly used SCR catalyst is the V_2O_5-WO_3(MoO_3)/TiO_2 system.TiO-2 support plays an important role in this catalyst system, because it not only has excellent sulfur resistance, but also has a good ability to disperse vanadium.It is shown that the physical and chemical properties of TiO_2 with different morphology or high exposure to special crystal surfaces may cause significant changes, such as surface energy, surface acidity, and interaction with active components.The applications of TiO_2 with specific morphology and surface structure in photocatalysis and dye sensitized solar cells have been widely reported and have shown unique properties.However, the effect of TiO_2 support morphology on the activity of titanium based SCR catalyst is still limited.On the basis of comparing the properties of industrial TiO_2 powders, the effect of the morphology of TiO_2 support on the activity of V_2O_5/TiO_2 catalysts was studied in this paper.The main results are as follows: 1: 1) the properties of four kinds of industrial TiO_2 powders are compared.Four kinds of industrial TiO_2 were used as carriers to prepare corresponding V_2O_5-MoO_3/TiO_2 catalysts by impregnation method.Through the SCR activity evaluation, it was found that the catalyst prepared by the TiO_2-J support with circular spheroid shape had better no conversion. The results showed that the specific surface area of the catalyst prepared by loading vanadium active component on TiO2-J support was obviously increased, while that of other supports supported on vanadium was obviously increased.The specific surface area showed a decreasing trend.The results of TPR and TPD show that the catalysts supported on TiO_2-J have higher reductivity and more acidic sites than other catalysts.Therefore, it is proved that TiO2-J has good physical and chemical properties, which can improve the SCR activity of catalyst and widen the reaction temperature window. 2) the controllable preparation methods of TiO_2 with different morphologies are discussed.By adjusting the concentration of hydrazine hydrate, the TIO _ 2 with regular octahedron morphology was obtained by hydrothermal method. The TIO _ 2-O was recorded as TIO _ 2-O, and the {101} crystal plane was mainly exposed.The effect of support morphology on the denitrification activity of V_2O_5/TiO_2 catalyst was investigated by adding HF capping agent to prepare TIO _ 2 with flat flake morphology, which was recorded as TIO _ 2-S, which was mainly exposed to high energy {001} crystal face. 3) the effect of support morphology on the denitrification activity of V_2O_5/TiO_2 catalyst was investigated.Three 3 wt%V_2O_5/TiO_2 catalysts were prepared by impregnation with TiO2-OO2-S and commercial TiO_2 P25 as supports.The results of activity evaluation showed that the V_2O_5/TiO_2-S catalyst supported on TiO_2-S had the highest NH_3-SCR catalytic activity.The physicochemical properties of the prepared catalysts were characterized by SEMMOTEMBETH H2-TPRN Ramanji NH3-TPDD DRIFTXPS and so on.It is found that there is a strong interaction between the active component and the TiO_2-S carrier with special structure on the {001} crystal plane, which makes the vanadium species dispersed well on the surface of TiO_2.Therefore, the V_2O_5/TiO_2-S catalyst has higher reductivity and more chemisorbed oxygen, which may be the main reason for its good NH_3-SCR reaction activity.
【学位授予单位】:北京工业大学
【学位级别】:硕士
【学位授予年份】:2016
【分类号】:O643.36

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