【作者】 黄宝娟；

【导师】 张敏华；

【作者基本信息】 天津大学 ， 化学工艺， 2017， 硕士

【摘要】 氮氧化物（NO_x）作为一种主要的大气污染物,对人类健康和环境危害极大。随着能源消耗的快速增长,NO_x排放逐年增加,烟气脱硝变得极为重要。选择性催化还原（SCR）法是目前主流的脱硝技术,近年来低温高效、抗硫中毒SCR催化剂的开发备受关注。金属有机骨架材料（MOFs）具有比表面积大、金属位高度分散、孔隙率高、孔道结构规整等优点,可作为潜在的SCR催化剂。但MOFs的稳定性是限制其应用的瓶颈,为此本文选择稳定性好且含缺陷位的UiO-66用于SCR脱硝反应。本文使用乙酸作为调节剂制备UiO-66,考察其对UiO-66的结构和性能的影响。结果表明,可以通过改变乙酸用量来调控UiO-66晶体的尺寸和形貌。乙酸改性后的UiO-66的缺陷位增多,比表面积和孔体积增大。活性测试结果表明,UiO-66在较高温度（>300℃）时才表现出催化脱硝活性,乙酸改性后样品的活性增强,NO转化率最高可达95%。分别采用浸渍法和原位沉积法在Ui O-66上负载MnO_x制备了MnO_x/UiO-66材料作为SCR催化剂,对其结构和性能进行了系统研究,并对MnO_x的负载量进行了优化。研究发现,在上述两种方法制备的MnO_x/UiO-66中,UiO-66都能保持其原晶体结构和形貌;MnO_x和UiO-66载体之间存在相互作用,有利于提高催化剂的低温SCR活性。与浸渍法相比,原位沉积法制备的催化剂的比表面积和孔体积较大,热稳定性较好。浸渍法制备的催化剂的低温活性明显改善,25%硝酸锰制备的催化剂在250²90℃之间可保持99%的NO转化率;原位沉积法制备的催化剂具有较高的低温催化活性,MnO_x负载量为8.5wt%的催化剂,在125²50℃之间均能保持99%的NO转化率。因此,原位沉积法制备的MnO_x/UiO-66催化剂具有良好低温活性和较宽的活性温度窗口。上述两种方法所制备的MnO_x/UiO-66具有较好的抗水和抗SO₂中毒性能。原料气中引入H₂O后,其活性虽有较明显下降,但NO转化率仍能保持在83%以上;SO₂对催化剂的活性影响较小,尤其对原位沉积法制备的催化剂的活性几乎没有影响。更多还原

【Abstract】 As one of the major atmospheric pollutants,nitrogen oxides（NO_x）are hazardous to environment and human health.Energy demand and its consumption are growing annually,resulting in larger volumes of NO_x released into the atmosphere.Therefore,it is urgent to remove NO_x from flue gas.The most widely used and efficeint technology for NO_x removal is selective catalytic reduction（SCR）,and the development of efficient low-temperature SCR catalyst with good SO₂ resistance has attracted extensive attentions.Metal-organic frameworks（MOFs）have exhibited outstanding properties including large surface areas,high porosity,highly dispersed metal sites and regular pore structures,which make them as the potential catalysts for the SCR reaction.However,the stability of MOFs has been the main drawback which limits their extensive applications.Therefore,the UiO-66 which exhibits excellent stabilities and possess a significant amount of missing linker defects is investigated for DeNO_x.Firstly,the UiO-66 is prepared with a coordination modulation process in which acetic acid as a modulator.The effects of acetic acid on the structure and properties of UiO-66 are studied.The characterization results indicate that the size and the morphology of the products can be controlled by varying the amount of acetic acid.The amounts of defects as well as the specific surface area and pore volumes of UiO-66 samples prepared by the coordination modulation process are increased,which are beneficial for SCR reaction.The activity test results indicate that UiO-66 exhibits high activity only at higher temperatures while the catalytic performance was poor at low temperatures.The UiO-66 samples prepared by the coordination modulation process show a better catalytic performance with the highest NO conversion of 95%.Secondly,MnO_x is supported on UiO-66 to prepare the MnO_x/UiO-66 catalysts by the impregnation method and the in-situ deposition method.The structures and properties of the prepared MnO_x/UiO-66 catalyst samples are investigated and their catalytic performance for NH₃-SCR are also studied.Moreover,the loading of MnO_x are optimized for above two preparation methods.The characterization results indicate that the UiO-66 still retains its inherent lattice phase and octahedral structure during manganese oxide loading process.X-ray photoelectron spectroscopy（XPS）analysis indicated that there exists a strong interaction between MnO_x and UiO-66,which has a positive effect on the catalytic activity for NH₃-SCR at low temperatures.Compared with the MnO_x/UiO-66 samples prepared by the impregnation method,the catalytic materials prepared with the in-situ deposition method show larger specific surface areas and pore volumes as well as better thermal stability.Compared with UiO-66,the catalytic activity of the MnO_x/UiO-66 prepared by the impregnation method is greatly improved at low temperatures.The MnO_x/UiO-66 material prepared with 25%manganese nitrate shows the highest SCR catalytic activity which reaches99%NO conversion in the temperature range between 250℃and 290℃.The MnO_x/UiO-66 catalysts prepared by the in-situ deposition method show both high catalytic activity and a wide active temperature window.The catalyst with 8.5 wt%MnO_x loading shows nearly 100%NO conversion in the temperature between 125℃and 250℃.On the whole,the catalysts prepared with the deposition method show better low-temperature SCR catalytic activity and wider active temperature windows.Both of the MnO_x/UiO-66 catalyst samples synthesized by the above two preparation methods exhibit good resistance to SO₂ and H₂O.The influence of H₂O on the catalytic activity was more obvious.However,the NO_x conversion still maintained above 83%.SO₂ just has a slightly influence on the performance of the MnO_x/UiO-66 catalysts,especially for the catalysts prepared by the in-situ deposition method.更多还原