导　　师： 张登松

学科专业： 070301

授予学位： 硕士

作　　者： ;

机构地区： 上海大学

摘　　要： 化石燃料燃烧所排放的氮氧化物引发了酸雨、光化学烟雾、臭氧层空洞等一系列环境与健康问题，对人类生活和健康的影响日益严重。氨选择性催化还原（NH3-SCR）技术是目前最有效的脱硝手段之一。开发具有高活性、抗硫性和稳定性的低温脱硝催化剂是目前研究的热点和难点。锰氧化物因其良好的低温活性、自身的环境友好性和优异的物理化学性质逐渐成为国内外低温脱硝催化剂的研究热点，但其在H2O和SO2存在的条件下会中毒失活。针对锰基催化剂存在的问题，本论文通过原位负载、构筑核壳结构和设计具有分级孔结构的双金属复合氧化物等方法，制备了三种新型锰基脱硝催化剂，提高了锰基催化剂的抗毒性和低温催化活性。主要内容如下： （1）通过聚苯乙烯磺酸钠（PSS）辅助回流法，在纳米碳管表面原位负载MnOx-CeOx复合金属氧化物，制备了活性组分均匀分散的纳米复合结构脱硝催化剂。研究了不同负载方法对催化剂形貌结构和物理化学性质以及催化性能的影响。研究结果表明，相比于浸渍法和机械混合法，原位负载制备的催化剂表现出更好的催化活性，更宽的操作温度区间以及显著提高的抗中毒性能。分析结果表明，该催化剂优异的催化性能和抗中毒性能归结为催化剂表面活性物种的高分散性以及活性组分与载体之间较强的相互作用。高度分散的活性物种不仅提供了更多的活性位点，而且促进了反应气体的吸附与活化，从而提高了催化剂的低温活性。活性组分与载体之间存在的相互作用加强了催化剂的稳定性以及抗毒性。 （2）设计了以负载MnOx-CeOx复合金属氧化物的纳米碳管为核、介孔氧化钛为壳的核壳结构催化剂。研究了介孔氧化钛壳层的包覆对催化剂的催化活性、稳定性和抗硫性的影响。研究发现介孔氧化钛壳层提高了催化剂的比表面积和孔容，促进了反应气体的吸附与存储，从而使催化剂具有更好的催化活性。并且，介孔氧化钛壳层能够提供一个有效壁垒阻止纳米碳管表面MnOx-CeOx纳米粒子的迁移团聚，加强了催化剂的稳定性。更重要的是，介孔氧化钛壳层不仅阻止了硫酸铵的生成对活性位的堵塞，同时抑制了活性物种的硫酸化，提高了催化剂的抗硫性。核壳结构的设计显著提高了催化剂的性能。 （3）以具有规则形貌的金属有机骨架（Mn3/[Co/(CN/)6/]2·nH2O）为前驱体，利用其特殊的结构和热学性质，设计合成了组分高度分散的MnxCo3-xO4纳米笼状分级结构脱硝催化剂。基于其独特的空心多孔分级结构和高度均匀分布的活性物种，MnxCo3-xO4纳米笼状分级结构催化剂较纳米粒子催化剂表现出更加优异的催化性能。MnxCo3-xO4纳米笼状催化剂的空心多孔分级结构有利于反应气分子的吸附、存储和扩散；同时提高了催化剂的比表面积，增加了活性位点与反应气体的接触。Mn3/[Co/(CN/)6/]2·nH2O前驱体中Mn和Co原子的规则排列使得MnxCo3-xO4纳米笼状分级结构催化剂中活性物种高度均匀的分布，加强了活性物种之间的相互作用，从而提高了催化剂的稳定性和抗中毒性能。这种利用金属有机骨架作为前驱体制备活性组分均匀分布的空心多孔催化剂的思路与概念，对设计开发高性能的催化剂具有很好的借鉴意义。 Nitrogen oxides /(NOx/) emitting from the combustion of fossil fuels are currentlyconsidered as one of the dominant sources of atmospheric pollution, which has givenrise to a variety of health and environmental-related issues, such as acid rain,photochemical smog, ozone depletion. The selective catalytic reduction /(SCR/) ofNOxwith NH3is nowadays well established as the most effective technology toeliminate NOx. The development of low-temperature deNOxcatalysts with highcatalytic activity, SO2-tolerance and stability is highly desirable but remainschallenging. Recently, Mn-based catalysts have been the rising star as thelow-temperature deNOxcatalysts due to the desirable low-temperature activities,inherently environmentally benign characteristics and outstanding physical andchemical properties. Unfortunately, Mn-based catalysts are very sensitive to thepresence of H2O and SO2in the feed gas and are severely deactivated by traceamounts of SO2. To address these problems, in this dissertation, three novel kinds ofMn-based deNOxcatalysts have been prepared via in-situ supported method,construction of core-shell structure, design of binary metal oxides with thehierarchical structures, respectively. The main study contents are listed as follows. /(1/) The catalysts with highly dispersed MnOx-CeOxmixed oxides are synthesizedby in-situ supported MnOx-CeOxmixed oxides on carbon nanotubes /(CNTs/) via aPSS assisted reflux method. The morphological structure, surface properties andcatalytic performance of catalysts prepared by different method are investigated. Thein-situ prepared catalysts display better NH3-SCR activity, more extensive operating-temperature window, higher SO2tolerance and improved water resistance than thatof the catalysts prepared by impregnation or mechanically mixed method. Theexcellent catalytic performance of the in-situ supported catalysts can be attributed tothe good dispersion of the active component on the surface of CNTs, the strong interaction among the manganese oxide, cerium oxide and CNTs. The gooddispersion of the active component not only provides more active sites, but alsopromotes the chemisorption and activation of the reactants, resulting in a bettercatalytic activity. The strong interaction among the manganese oxide, cerium oxideand CNTs enhances the stability and SO2tolerance of the catalysts. /(2/) By coating the mesoporous TiO2layers on CNTs-supported MnOxand CeOxnanoparticles, we obtained a core–shell structural deNOxcatalyst with high catalyticactivity, good SO2-tolerance and enhanced stability. The porous feature of TiO2sheaths provides a larger surface area to adsorb reagents, resulting in a highercatalytic activity. Moreover, the meso-TiO2sheaths serve as an effective barrier toprevent the aggregation of metal oxide NPs and thus enhance the thermal stability.More importantly, the meso-TiO2sheaths can not only prevent the generation ofammonium sulfate species from blocking the active sites but also inhibit theformation of manganese sulfate, resulting in a higher SO2-tolerance. The studyindicates that the design of a core–shell structure is efective to promote theperformance of deNOxcatalysts. /(3/) Starting with shape-controlled synthesis of metal-organic frameworks/(Mn3/[Co/(CN/)6/]2·nH2O/) nanocubes as precursors, we rationally designed andoriginally developed a high-performance deNOxcatalyst based on MnxCo3-xO4nanocages with hollow and porous structures derived from Mn3/[Co/(CN/)6/]2·nH2Onanocubes via an annealing treatment in air. As compared with conventionalnanoparticles, MnxCo3-xO4nanocages possess a much better catalytic activity atlow-temperature regions, higher N2selectivity, more extensive operating-temperature window, higher stability and SO2-tolerance, due to their hollow andporous structures and the uniformly distributed active sites. The feature of hollowand porous structures provides a larger surface area and more active sites to adsorband activate reagents, resulting in the higher catalytic activity. Moreover, the uniformdistribution and the strong interaction between manganese and cobalt oxide species not only enhance the catalytic cycle but also inhibit the formation of manganesesulfate, resulting in high catalytic cycle stability and improved SO2-tolerance. Thesynthesis approach in the present study is conducive to the development ofhigh-performance catalysts.

关 键 词： 脱硝 催化剂 选择性催化还原 氧化锰

分 类 号： [O643.36]

领　　域： [理学] [理学]