【作者】 姚文生；

【导师】 王日杰；

【作者基本信息】 天津大学 ， 工业催化， 2009， 博士

【摘要】 本文采用溶液燃烧法和柠檬酸络合法制备了系列镧钴钙钛矿催化剂,使用XRD、FT-IR、H2-TPR、XPS、BET、SEM-EDS及TEM等多种分析手段对催化剂进行了表征,并利用程序升温反应技术,在模拟柴油机尾气的情况下对同时催化去除氮氧化物(NOx)和碳烟的反应进行了实验研究。首先,采用溶液燃烧法合成了La1-xKxCoO3(x = 0～0.5)镧钴钙钛矿催化剂,所合成的催化剂均属于菱方晶系钙钛矿晶型,样品表面具有十分丰富的类似蜂窝状的孔道结构。K+部分取代La3+,催化剂表面氧空位数目增加,同时形成Co3+-Co4+共存体系,从而使得催化剂的性能得到显著改善。La0.7K0.3CoO3催化剂的碳烟起燃温度为262°C,NO向N2的最大转化率为27.5%。其次,采用改进的溶液燃烧法成功地制备了系列LaCo1-xPdxO3(x = 0～0.03)钙钛矿催化剂。研究发现,Pd以Pd3+或Pd4+价态存在于钙钛矿晶格中。添加贵金属Pd能够显著提高LaCo1-xPdxO3催化剂同时去除NOx和碳烟的活性。其中LaCo0.97Pd0.03O3催化剂碳烟起燃温度为265°C,NO向N2的最大转化率为32.8%。再次,对La1-xMexCo1-yPdyO3(Me=K、Sr、Ce x = 0,0.2, y=0,0.05)系列新型复合金属氧化物催化剂研究结果表明,用Sr或K取代LaCoO3中的La,催化剂的性能得到改善,而Ce取代不能提高催化剂的活性;进一步用贵金属Pd取代La1-xMexCoO3中的Co ,催化剂的性能得到进一步的提高。La0.8Sr0.2Co0.95Pd0.05O3呈现最佳的催化活性,其碳烟的起燃温度为258°C,而NO向N2的最大转化率达到31.6%。最后,对三种活性较好催化剂La0.8Sr0.2Co0.95Pd0.05O3、La0.8K0.2Co0.95Pd0.05O3及La0.8K0.2CoO3,进一步考察了不同反应条件的影响,并结合前人研究结果分析了反应机理。结果表明碳颗粒的存在促进了NO的催化还原,同时NO也对碳颗粒燃烧有一定影响。O2浓度的增加促进了碳烟的燃烧,三种催化剂碳烟起燃温度都随着O2浓度增加而下降,La0.8Sr0.2Co0.95Pd0.05O3催化剂的N2选择性明显增加。三种催化剂的碳烟起燃温度受气体总流量影响较小,在流速较宽范围内25mL/min～50mL/min,La0.8Sr0.2Co0.95Pd0.05O3都表现出对NO催化分解较高活性。更多还原

【Abstract】 A number of catalysts based on the lanthanum cobaltite perovskite type oxides were prepared by solution combustion synthesis or citric acid complexation. The catalysts were characterized using XRD, FT-IR, H2-TPR, XPS, BET, SEM-EDS and TEM. The catalytic activities simultaneously removed soot and NOx were evaluated using a technique of temperature programmed reaction (TPR) under the modeled diesel engine exhaust circumstance.Firstly, the La1-xKxCoO3 (x=0～0.5) perovskite-type oxides were prepared by solution combustion synthesis. The results showed that all prepared catalysts possessed ABO3 perovskite-type structures with porous sponge-like structure, corresponding to a rhombohedral system. For the La1-xKxCoO3 catalysts, since the partial substitution of K for La at A-site resulted in the increase of oxygen vacancy and Co3+-Co4+ system, it enhanced the catalytic performance. La0.7K0.3CoO3 catalyst with the highest catalytic activity was observed, and the maximum NO conversion into N2 and the ignition temperature of soot were 27.5%and 262°C, respectively.Secondly, a number of nan-perovskite catalysts LaCo1-xPdxO3(x=0～0.03) were prepared via solution combustion synthesis. The noble metal Pd in the form of Pd3+ or Pd4+ was successfully deposited onto the LaCoO3 perovskite lattices, leading to improve the catalytic performance significantly . The maximum NO conversion into N2 and the temperature of were 32.8% and 265°C, respectively.Thirdly, the novel La1-xMexCo1-yPdyO3(Me=K, Sr, Ce x = 0,0.2 y=0,0.05) catalysts with ABO3-type structure were prepared using the citric acid complexation. For the LaCoO3 catalyst, the partial substitution of K or Sr at A-site enhancing the catalytic performance was found, while no improve the catalytic activity from the Ce-substituted catalysts was observed. Moreover, the catalytic activities of all the Pd-substituted catalyst further increased and La0.8Sr0.2Co0.95Pd0.05O3 showed the highest activity. The maximum conversion of nitrogen oxide to N2 and the ignition temperature were 31.6% and 258°C, respectively.Finally, Effects of reaction conditions on catalytic performance, including concentrations of O2 and total flow rate, were investigated over three catalysts. the mechanisms were proposed based on both our results and other work. The carbon particulate plays an important role in the reduction of NO, and NO, it also affected the oxidation of carbon particulate. The ignition temperature decreased with increasing O2 concentration. The maximum NO conversion into N2 catalyst increased in range from 1% to 5% using a La0.8Sr0.2Co0.95Pd0.05O3 catalyst. The total gas flow rate did less influence on the ignition temperature of soot. The La0.8Sr0.2Co0.95Pd0.05O3 catalyst showed better performance over the total gas flow rate range of 25 mL/min～50 mL/min.更多还原