Ce基复合氧化物同时催化去除碳烟-NOx的性能研究

发布时间：2018-06-14 16:51

本文选题：催化去除 + 铈基氧化物　；参考：《上海交通大学》2015年硕士论文

【摘要】：近年来,随着汽车保有量的快速增长,机动车排放污染已成为城市雾霾的主要来源之一,如何控制排放污染已成为全社会严重关切的问题。但是,柴油机燃烧过程中的主要有害排放物颗粒物(PM)和氮氧化物(NOx)存在着此消彼长的trade-off效应,单纯通过内燃机机内净化控制难以将两者同时降到排放限值以下,柴油机尾气后处理技术则是一种有效降低柴油机的污染排放的途径。本文对Ce基复合氧化物同时催化去除柴油机排放污染物PM和NOx展开了实验研究,采用色素碳黑与催化剂紧接触混合,分别在空气气氛和NOx气氛下测试其催化性能;采用BET、XRD、TEM、H2-TPR、Soot-TPR、XPS等手段研究了氧化物催化剂的结构、催化活性及其机理。本研究采用柠檬酸络合法制备了不同比例的Ce-La复合稀土氧化物催化剂,讨论了La的掺入对CeO2氧化催化碳烟和去除NOx性能的影响。发现Ce-La复合氧化物的催化活性高于其单一氧化物,一部分La3+可能进入了CeO2晶格,形成了Ce1-xLaxO2固溶体。Ce1-xLaxO2氧化物的比表面积与催化活性成正相关,La3+的掺杂抑制了CeO2晶粒长大,有利于提升催化活性;随着煅烧温度升高,催化剂比表面积下降,晶粒变大,催化活性下降;与O2气氛相比,NO+O2气氛下催化剂氧化碳烟的起燃温度更低。其中,CeLa0.05催化剂的最低起燃温度达到308 oC。采用柠檬酸络合法制备了不同过渡金属(Co、Fe、Mn、Cu)和稀土金属铈(Ce)的复合氧化物催化剂,不同过渡金属对CeO2的掺杂都有助于提高催化去除碳烟和NOx的活性。初步研究表明Co主要以Co3O4的形式分散在CeO2表面,Co和Ce的相互作用,以及催化剂表面金属离子变价,有利于电子转移,从而提高催化碳烟的活性。本文还探讨了在Ce-Co复合氧化物中La掺杂对催化剂活性的促进作用。Co主要以氧化物形式均匀分散在Ce-La固溶体表面,Co和La的掺杂有助于增大催化剂比表面积、抑制CeO2晶粒长大和提高氧化还原性能。在Ce-Co中引入La后形成的微量LaCoO3有助于形成更多氧空位,从而提高了催化剂对碳烟的催化氧化性能。Co0.1/CeLa0.05氧化物为本文性能最佳催化剂,空气气氛下催化燃烧碳烟T10及T50分别为289 oC及357 oC;在模拟尾气气氛下,T10及T50分别为269 oC及301 oC,N2的产率为41.4%,N2选择性达到95.1%。
[Abstract]:In recent years, with the rapid growth of vehicle ownership, vehicle emission pollution has become one of the main sources of urban smog. How to control the emission pollution has become a serious concern of the whole society. However, the main harmful emission particles (PMPM) and nitric oxide (NOX) in the combustion process of diesel engine have the opposite trade-off effect, so it is difficult to reduce both of them to the emission limit value at the same time through the internal purification control of the internal combustion engine. The aftertreatment technology of diesel engine exhaust gas is an effective way to reduce the pollution emission of diesel engine. In this paper, the catalytic removal of PM and no _ x from diesel engine emissions by ce based composite oxides was studied. Pigment carbon black and catalyst were mixed tightly and their catalytic performance was tested in air atmosphere and no _ x atmosphere, respectively. The structure, catalytic activity and mechanism of the oxide catalysts were studied by means of BETX XRDX TEMN H2-TPRN Soot-TPRXPS. In this paper, Ce-La complex rare earth oxide catalysts were prepared by citric acid complexation method. The effect of La addition on the catalytic soot and no _ x removal performance of CEO _ 2 oxidation was discussed. It is found that the catalytic activity of Ce-La composite oxide is higher than that of its single oxide. Some La3 may enter the CeO2 lattice and form Ce1-xLaxO2 solid solution. The doping of Ce1-xLaxO2 oxides has a positive correlation between the specific surface area and catalytic activity, and the doping of La 3 inhibits the grain growth of CeO2. With the increase of calcination temperature, the specific surface area of the catalyst decreases, the grain size becomes larger, and the catalytic activity decreases. Compared with the O2 atmosphere, the ignition temperature of the catalyst soot is lower. The lowest ignition temperature of CeLa0.05 catalyst is 308 OC. The complex oxide catalysts of different transition metals (CoCoC FeMn-Cu) and rare earth cerium (ce) were prepared by citric acid complexation method. The doping of different transition metals to CeO2 can improve the catalytic removal activity of soot and no _ x. The preliminary study shows that Co is mainly dispersed in the form of Co _ 3O _ 4 on the surface of CEO _ 2, and the metal ions on the surface of the catalyst are in favor of electron transfer, so as to improve the activity of catalytic soot. The effect of La doping on the catalytic activity of Ce-Co composite oxides is also discussed. The doping of Co and La on the surface of Ce-La solid solution in the form of oxides is helpful to increase the specific surface area of the catalysts. The grain growth of CeO2 was inhibited and the redox property was improved. The addition of La to Ce-Co helps to form more oxygen vacancies, thus improving the catalytic performance of the catalyst for soot oxidation. Co0.1% CeLa0.05 oxide is the best catalyst. The catalytic combustion of soot T10 and T50 were 289 OC and 357 OC respectively in air atmosphere, and the yields of T10 and T50 were 269 OC and 301 OC N 2 in simulated tail gas atmosphere, respectively.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK421.5

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