类水滑石衍生复合氧化物催化氧化烟气中零价汞的研究

发布时间：2018-05-04 23:09

本文选题：Hg0氧化 + 类水滑石　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：由于汞的毒性、生物累积性和在食物链中的传递性,使其成为一种主要的全球性污染物。人类活动向大气中排放的大部分汞是在工业革命之后燃烧煤炭造成的。燃煤烟气中排放出来的汞主要有三种形态:二价汞(Hg2+),颗粒吸附汞(Hgp)和单质汞(Hg0),前两个由于可溶性较强、易于捕集从而能够被现有的湿法脱硫装置或者布袋除尘器从烟气中脱除掉,但是Hg0却由于游离性强难以脱除,并且从排放点能够进行长距离的传输扩散造成大面积的大气汞污染。因此,将Hg0氧化成Hg2+是将其从烟气中脱除的关键。用传统的浸渍法合成的催化剂,活性组分很难在催化剂上面均匀分布,导致催化剂活性的降低并且活性组分容易从载体上面脱落。因为类水滑石(LDHs)材料具有独特的有序层状结构并且构成元素互相高度分散,在后续的焙烧过程中由于晶格定位效应,这种高度分散的状态不会被破坏。所以首先合成LDHs前驱体再经过焙烧处理后就能得到活性组分高度分散的金属氧化物催化剂。在本论文中,首先用共沉淀法合成了LDHs前驱体,在空气中高温焙烧后得到了复合金属氧化物催化剂。在实验室规模下通过模拟烟气对催化剂进行了筛选和性能评价。利用XRD、XPS、BET、Hg-TPD、H2-TPR、SEM等表征手段对催化剂进行分析,详细探讨了催化剂的汞氧化机理和烟气组分对其汞氧化性能的影响。结果表明,以LDHs为前驱体合成的1%Mn/Co Al Ox催化剂具有优异的汞催化氧化活性,在高空速条件下能够在宽温度窗口中有效氧化脱除高达95%以上的Hg0,同时具有良好的抗水和抗硫性能。该催化剂有望于不远的将来投入工业应用。
[Abstract]:Mercury is a major global pollutant due to its toxicity, bioaccumulation and transitivity in the food chain. Much of the mercury emitted into the atmosphere by human activity was caused by the burning of coal after the industrial revolution. There are three main forms of mercury emitted from coal-fired flue gas: Hg2 +, Hg ~ (2 +), Hg ~ (2 +) and Hg _ (0), and Hg ~ (2 +) ~ (2 +). It is easy to trap and can be removed from the flue gas by the existing wet desulfurization device or bag dust collector, but the Hg0 is difficult to remove because of its strong dissociation. And long-distance transport and diffusion from the emission point resulted in a large area of atmospheric mercury pollution. Therefore, oxidation of Hg0 to Hg2 is the key to its removal from flue gas. The active component of the catalyst synthesized by the traditional impregnation method is difficult to be uniformly distributed on the catalyst, which leads to the decrease of the activity of the catalyst and the easy exfoliation of the active component from the support. Because of its unique ordered layered structure and highly dispersed elements, the highly dispersed state will not be destroyed in the subsequent calcination process due to lattice localization effect. Therefore, the highly dispersed metal oxide catalysts with highly dispersed active components can be obtained after calcination of the LDHs precursor. In this thesis, LDHs precursors were synthesized by coprecipitation method, and the composite metal oxide catalysts were prepared after calcination in air. The catalyst was screened and evaluated by simulated flue gas in laboratory. The catalysts were characterized by means of XRDX, XRDP, BETX, Hg-TPDN, H2-TPR-SEM, and the mechanism of mercuric oxidation of catalysts and the effect of flue gas composition on their mercury-oxidizing properties were discussed in detail. The results show that the 1%Mn/Co Al Ox catalyst synthesized with LDHs as precursor has excellent mercuric oxidation activity and can effectively remove Hg0, which is more than 95% in wide temperature window, under the condition of high altitude velocity, and has good water and sulfur resistance. The catalyst is expected to be used in industry in the near future.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701;O643.3

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