钙钛矿型复合氧化物催化消除NO的研究

【作者】 姜涛；

【导师】 袁福龙；

【作者基本信息】 黑龙江大学 ， 无机化学， 2008， 硕士

【摘要】 氮氧化物（NO_x）是严重的大气污染物,对环境和人类都会造成极大的伤害。钙钛矿型复合氧化物由于其结构稳定,可容纳大量的金属元素,表现出独特的催化消除NO_x的性能,已引起了国内外许多科研人员的极大关注。本文以LaFeO₃、LaMnO₃为基础,采用柠檬酸溶胶-凝胶法合成了A位和B位掺杂改性的系列钙钛矿型复合氧化物催化剂。测试了其催化消除NO_x的性能,并分别探讨了A位和B位掺杂元素、掺杂比例对催化活性中心离子的影响。发现碱土金属对A位La的取代可以提高钙钛矿型复合氧化物的催化性能,其中以Ba的取代效果最好。X-射线衍射（XRD）结果显示当Ba的掺杂量小于等于20%时没有其它杂相,氢气程序升温还原（H₂-TPR）研究结果表明少量Ba的掺入会提高B位金属的氧化性,从而提高了催化剂的催化性能。La_0.75Ba_0.25FeO₃催化剂在850℃时N₂的生成率可达72%。本文同时考察了B位掺杂不同过渡金属对其催化活性的影响,发现分别掺杂Ni、Cu后的Fe、Mn系列催化剂的催化性能较好。氧气程序升温脱附（O₂-TPD）、氢气程序升温还原（H₂-TPR）等结果表明,B位掺入不同过渡金属会使B位金属的氧化性增强,同时会增加氧空位的浓度、提高晶格氧的活动性从而促进催化活性。La_0.85Ba_0.15Fe_0.7Ni_0.3O₃,La_0.8Ba_0.2Mn_0.6Cu_0.4O₃催化剂850℃时N₂的生成率分别可达88和90%。更多还原

【Abstract】 Nitrogen oxides （NO_x） are serious pollutants in earth’s atmosphere, they are harmful gases both to environment and human body. As one catalyst for NO_x removal, special attention has been paid to the use of perovskite mixed oxides due to their remarkable stability, and perovskite-type oxides can accommodate a large number of metal, which result in the obtained samples possessing special character.In this dissertation, a series of perovskite-type oxides via substituting the A or B site of LaFeO₃ and LaMnO₃ were successfully synthesized through citric acid complexing sol-gel method. The influence of doping elements in A site and B site and the doping ratio on the catalytic activity of perovskite-type oxides was also discussed in this thesis. It was found that the activity in NO direct decomposition could be improved by substituting alkaline-earth metals for La, in which the samples of substituting Ba for La performed best activity. XRD results demonstrated that perovskite phase is retained at low 20% Ba doping content, H₂ temperature programmed reduction （H₂-TPR） indicate that low substituting Ba for La performed their activity for NO removal through enhancing the oxidability of B site metal. The conversion of 1.0% NO to nitrogen over La_0.75Ba_0.25FeO₃ can attain 72% at 850℃. The influence of doping elements in B site was also discussed in this thesis. It was found that doping Fe and Mn series catalysts performed special catalytic activity. H₂-TPR and O₂ temperature programmed desorption （O₂-TPD） indicate that B site doping different transition metal can enhance the oxidability of B site metal, increase the amount of oxygen vacancy and promote the mobility of crystal lattice oxygen. The conversion of 1.0% NO to nitrogen is 88% and 90% at 850℃over La_0.85Ba_0.15Fe_0.7Ni_0.3O₃, La_0.8Ba_0.2Mn_0.6Cu_0.4O₃ catalysts, respectively.更多还原