Stoichiometric LaMnO3 and LaCoO3 nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La（NO3）3＋6H20/[Mn（NO3）2-4H20 or Co（NO3）2-6H20]=1 and citric acid as disperser at te...Stoichiometric LaMnO3 and LaCoO3 nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La（NO3）3＋6H20/[Mn（NO3）2-4H20 or Co（NO3）2-6H20]=1 and citric acid as disperser at temperature range of 600-900 ℃for 5 h. The role of organic additive concentration, which was 0.0, 1.0, 2.5 and 5 times of the total number of moles of the nitrate ions, was investigated on phase formation, morphology, extent of crystallization and particle size of the products. Products were characterized by X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM） and Wansmission elec- tron microscopy （TEM） analysis. The tendency of lanthanum ion toward manganese cation was observed to be more than to cobalt cation for the formation of LaBO3 （B： Mn or Co） perovskite phase. A spongy product was formed on perovskite phase formation or in the pres- ence of citric acid. A constructive or destructive effect was observed for the organic disperser on perovskite phase formation, which de- pended on mole of the citric acid.展开更多
文摘采用共沉淀的方法制备了系列镁铝水滑石衍生复合氧化物,分别考察了煅烧温度、反应温度、水蒸气体积分数以及碱金属添加对材料COS水解反应活性的影响.通过X射线衍射仪(XRD)、气体吸附仪(BET)、程序升温脱附(TPD)和X射线光电子能谱(XPS)等对复合氧化物的晶体结构、比表面积、孔结构和碱性位分布等进行表征.结果表明,水解反应活性随煅烧温度的增加先升高后减小,650℃煅烧制备的复合氧化物材料具有最佳的水解反应活性(COS完全转化的维持时间为180min).反应温度的升高有利于水解活性的提高,从70℃起水解反应就具有很高的活性和稳定性.此外,Cs的添加有利于水解反应活性的提高,掺杂后材料COS完全转化的维持时间达到了480 min.
文摘Stoichiometric LaMnO3 and LaCoO3 nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La（NO3）3＋6H20/[Mn（NO3）2-4H20 or Co（NO3）2-6H20]=1 and citric acid as disperser at temperature range of 600-900 ℃for 5 h. The role of organic additive concentration, which was 0.0, 1.0, 2.5 and 5 times of the total number of moles of the nitrate ions, was investigated on phase formation, morphology, extent of crystallization and particle size of the products. Products were characterized by X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM） and Wansmission elec- tron microscopy （TEM） analysis. The tendency of lanthanum ion toward manganese cation was observed to be more than to cobalt cation for the formation of LaBO3 （B： Mn or Co） perovskite phase. A spongy product was formed on perovskite phase formation or in the pres- ence of citric acid. A constructive or destructive effect was observed for the organic disperser on perovskite phase formation, which de- pended on mole of the citric acid.
