蜂窝状钒钼钛脱硝催化剂的涂覆技术及性能研究

发布时间：2018-05-19 20:21

本文选题：堇青石蜂窝陶瓷 + 整体式催化剂　；参考：《重庆大学》2015年硕士论文

【摘要】：随着近年来燃煤烟气和机动车辆尾气中NOx的大量排放导致大气污染问题的日益突出,以及人们对环境保护意识的逐渐提高,使得以NH3作为还原剂选择催化还原(NH3-SCR)大气中的氮氧化物技术成为目前一个研究热点并得到广泛应用。蜂窝状整体挤出式V2O5-WO3/Ti O2催化剂已成功应用于工业烟气脱硝领域,但催化剂用量大成本高。鉴于我国含砷的燃煤较多,需添加具有一定抗砷中毒效应的钼助剂,然而钼添加到V2O5/Ti O2催化剂后会对催化剂整体机械强度造成一定程度的下降。堇青石蜂窝陶瓷机械强度高、热膨胀系数小,已经被广泛作为蜂窝状涂覆型催化剂的基体材料,此类催化剂目前多应用于机动车尾气处理,由于此类催化剂具有较大的孔密度,涂层负载量有限易脱落,因此尚未见工业大流量烟气处理应用的成功实例。本课题创新的采用大孔径的堇青石作为基体材料,通过溶胶凝胶法制备高固低粘的纳米Ti O2溶胶,采用浸Q梅ㄍ扛苍靥逋坎愫透涸胤邦饣钚宰榉帧Ｍ苯柚怼RD、UV-vis DRS、Raman及XPS等多种表征手段将催化剂制备工艺(包括涂覆次数和时间、干燥温度和时间、活性组分浸渍液浓度、活性组分浸渍方式和钒钼比)对载体涂层和活性组分负载量、涂层粘结强度、催化剂及组分结构形貌、氧化还原性能及催化活性等的影响进行了详细深入的分析。①在涂覆及浸渍过程中,载体涂层及活性组分的吸附速率快,均约为0.5h就达到了吸附饱和,增加涂覆及浸渍次数,均可显著增大载体涂层及活性组分的整体负载量,但增量逐次递减。载体涂层及活性组分固化过程中,80℃的固载温度最宜,约1h负载量保持稳定;②催化剂涂层均匀平整,呈多层覆盖,表层具有轻微开裂无掉皮,具有极强的粘结强度强。涂覆过程不影响催化剂涂层内部孔结构,其等温吸附脱附曲线呈IV类,具有介孔和少量大孔;③钼的引入能够明显抑制钒氧物种晶体的晶粒生长,促使部分孤立态的钒进入了Ti O2的晶格中,造成剩余电子结合能向高场移位,V2p结合能向低场位移。钼对钒也存在诱导效应,使V2p剩余电子的结合能向高场移位,Mo3d结合能向低场位移;④分浸工艺中优先浸渍钼可以更大程度提高活性物种在催化剂表面分散,提高其氧化还原性能,使还原温度向低温偏移,增大钒氧物种的带隙宽度并提高催化剂高温段的催化活性。共浸方式浸渍钼较之于分浸,更能有效的抑制钒的结晶化,促使其与载体发生键合作用,钼以促进钒和载体键合为主,对晶态钒氧物种的掺杂作用要弱。所有样品均具有较强的抗硫性;⑤浸渍液浓度增大提高了活性物种的结晶度,使其氧化性增大,降低了高温段催化剂的催化活性,但低温段催化活性相对增大。V2p、Mo3d和Ti2p的结合能均向低场移位,载体与活性物种之间的相互作用减弱;⑥钼相对钒的比例增大,使晶态钒氧物种和锐钛型Ti O2的晶粒生长受到抑制并出现展宽和蓝移,孤立态钒氧物种分散度增大以及钼氧化物结晶度提高但不明显,促进了钼对钒氧物种的分散作用,提高了催化活性,温度越高促进作用越明显。
[Abstract]:With the increasing emission of NOx in coal-fired flue gas and motor vehicle exhaust in recent years, the problem of air pollution is becoming more and more prominent, and people's awareness of environmental protection is gradually improved. The choice of NH3 as a reducing agent in the catalytic reduction (NH3-SCR) atmosphere has become a research hotspot and widely used. The V2O5-WO3/Ti O2 catalyst has been successfully applied to the field of industrial flue gas denitrification, but the amount of catalyst is high cost. In view of the high amount of arsenic in the coal burning in China, it is necessary to add molybdenum additives with a certain arsenic poisoning effect. However, the addition of molybdenum to the V2O5/Ti O2 catalyst will cause a certain degree of overall mechanical strength of the catalyst. Down. Cordierite honeycomb ceramics have high mechanical strength and low thermal expansion coefficient, and have been widely used as matrix materials for honeycomb coated catalysts. This kind of catalyst should be used in the treatment of motor vehicle exhaust at present. Because such catalysts have large pore density, and the load of the coating is limited easily to fall off, so there is no industrial large flow flue gas. A successful example of rational application. The project uses a large aperture cordierite as a matrix material to prepare a high solid and low viscosity nano Ti O2 sol by sol-gel method, and the preparation process of the catalyst by dipping Q plum, dimple, beech and plutonium beech frame M???? RD, UV-vis DRS, Raman and XPS. The effects of the coating times and time, the drying temperature and time, the concentration of the active component impregnation solution, the active component impregnation method and the ratio of vanadium and molybdenum) on the load of the carrier coating and the active component, the bond strength of the coating, the structure and morphology of the catalyst and the composition, the redox property and the catalytic activity of the catalyst were analyzed in detail. In the process of soaking, the adsorption rate of the carrier coating and the active component is fast. The adsorption saturation is reached about 0.5h, and the increase of the coating and the number of impregnation can increase the overall load of the carrier coating and the active component, but the increment gradually decreases. During the curing process of the carrier coating and the active component, the solid loading temperature at 80 C is the best, about 1H load is guaranteed. The coating is uniform and smooth, the coating is uniform and smooth, the coating is covered with multilayer, the surface has a slight crack and no skin, and the coating has strong bond strength. The coating process does not affect the inner pore structure of the catalyst coating. The isothermal adsorption desorption curve is IV, with mesoporous and a small number of large pores; 3. Molybdenum can obviously inhibit the crystal grain of vanadium and oxygen species. The growth of a partially isolated state of vanadium enters the lattice of Ti O2, causing the residual electron binding energy to shift towards the high field and the V2p binding energy to the low field. Molybdenum also has an induction effect on vanadium, which makes the binding energy of the residual electrons of V2p shift to the high field and the Mo3d binding energy to the low field. (4) the preferential impregnation of molybdenum in the leaching process can increase the survival to a greater degree. The dispersing of the sex species on the surface of the catalyst improves the oxidation and reduction performance, makes the reduction temperature shift to the low temperature, increases the band gap width of the vanadium and oxygen species and improves the catalytic activity of the high temperature section of the catalyst. The co impregnation method impregnated molybdenum is more effective in inhibiting the crystallization of vanadium, and promoting the bonding with the carrier, and the molybdenum is used to promote vanadium and the vanadium. The carrier bonding is the main factor, and the doping effect on the crystalline vanadium oxygen species is weak. All the samples have strong sulfur resistance. 5. The increase of the concentration of the impregnation liquid increases the crystallinity of the active species, increases the oxidation and reduces the catalytic activity of the catalyst at the high temperature section, but the catalytic activity of the low temperature section increases.V2p, and the binding energy of the Mo3d and Ti2p is all low. The interaction between the carrier and the active species is weakened; 6. The ratio of molybdenum to vanadium increases, making the grain growth of the crystalline vanadium oxygen species and the anatase Ti O2 restrained and broadening and blue shift, the dispersion of the isolated vanadium oxygen species and the high crystallinity of molybdenum oxide are not obvious, which promotes the dispersion of molybdenum to vanadium and oxygen species. The catalytic activity increased, and the higher the temperature, the more obvious the promoting effect.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701;O643.36

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