【作者】 马岚；

【导师】 胡瑞生；

【作者基本信息】 内蒙古大学 ， 物理化学， 2009， 硕士

【摘要】 采用以柠檬酸为络合剂的溶胶-凝胶法制备钙钛矿型复合氧化物La₂NiBO₆（B=Mn、Fe、V）催化剂,运用XRD、TPR、FT-IR、BET、SEM、TEM等对其性能进行了表征,并考察了催化剂的导电性、磁性及其在甲烷燃烧反应中的催化活性。实验结果表明,在空气气氛中1100℃焙烧3h后,催化剂La₂NiMnO₆和La₂NiFeO₆均生成单相物相。其中,La₂NiMnO₆对甲烷催化燃烧的起燃温度为440℃,完全转化温度为666℃,催化剂La₂NiMnO₆对甲烷催化燃烧活性最好,催化剂La₂NiVO₆对甲烷燃烧催化活性最差。在室温下电导测试发现La₂NiMnO₆的导电性要优于La₂NiVO₆的导电性。我们还进一步研究了La₂NiMnO₆在不同焙烧温度下的物相变化,可知单相双层钙钛矿型氧化物La₂NiMnO₆的形成温度在900℃到1100℃之间。采用柠檬酸溶胶-凝胶法在空气气氛下适当的温度焙烧3h,制备出稀土双钙钛矿型化合物La₂NiFeO₆,研究焙烧温度分别在800℃,900℃,1000℃和1100℃下对催化剂的一些物理化学性质和催化活性的影响。随着焙烧温度的提高催化剂物相从单钙钛矿型转变为双钙钛矿型,在900℃形成了双钙钛矿La₂NiFeO₆。在800℃-1000℃范围内La₂NiFeO₆的甲烷燃烧催化活性随着焙烧温度的提高而有所改善。在此基础上我们对样品La₂NiMnO₆的A位用Sr进行修饰,结果发现活性没有改善,所以又对样品La₂NiFeO₆的A位进行修饰,制备出系列催化剂La_2-xSr_xNiFeO₆（x=0.02,0.08,0.1,0.5）,锶的不同修饰量对稀土双钙钛矿型氧化物La₂NiFeO₆的甲烷催化燃烧活性有一定的影响,其中La_1.9Sr_0.1NiFeO₆的催化活性最好,起燃温度为378℃,完全转化温度为528℃。当锶的掺杂量增至0.5时,活性反而下降,说明适量的掺杂有利于催化剂活性的提高。更多还原

【Abstract】 The perovskite-type composite oxides La₂NiBO₆（B=Mn、Fe、V） were synthesized by the sol-gel method and characterized by means of XRD,TPR,BET, FT-IR,TEM,SEM,Electrical conductivity Test and magnetic properties.Meanwhile, we investigated catalytic activity of catalysts in methane catalytic combustion.The double perovskite catalysts La₂NiBO₆（B=Mn,Fe,V） were prepared by using sol-gel method,followed by annealing under air atmosphere（air flow,at 1100℃for 3 hours）.For La₂NiMnO₆ and La₂NiFeO₆,single-phase double perovskite catalysts can be formed.La₂NiMnO₆ showed a better catalytic activity for methane combustion than La₂NiFeO₆ and La₂NiVO₆,its T₁₀（methane conversion of 10%）and T₉₀（methane conversion of 90%） were 440℃and 666℃respectively.Under room temperature conductivity testing indicated electrical conductivity of La₂NiMnO₆ was better than La₂NiVO₆.Then phase’s variation of La₂NiMnO₆ was investigated in different calcination temperature,we can deduce that the formation temperature of single-phase double perovskite La₂NiMnO₆ oxides is between 900℃and 1100℃.The rare earth double perovskite catalyst La₂NiFeO₆ was prepared by the sol-gel method using citric acid as complexing agent,followed by annealing under air atmosphere at 800℃,900℃,1000℃and 1100℃for 3 hours,then we can study effect of calcination temperature on the physicochemical properties and catalytic activity.With increasing the calcination temperature,single perovskite oxide changed into double perovskite oxide gradually,it formed double perovskite La₂NiFeO₆ at 900℃.Because of perfect structure of double perovskite,catalytic activity in methane combustion of La₂NiFeO₆ improves with the calcination temperature increasing in the range of 800℃-1000℃.On the basis of the samples La₂NiMnO₆ modified with Sr,then finding there is no improvement on catalytic activity,so Sr doped double perovskite oxides La_2-xSr_xNiFeO₆（x=0.02,0.08,0.1,0.5） were prepared by the sol-gel method,the different modification of strontium could affect catalytic activity of double perovskite La₂NiFeO₆.The result showed that catalytic activity of La_1.9Sr_0.1NiFeO₆ was the best, T₁₀and T₉₀were 378℃and 528℃respectively.When doping content increased to 0.5, catalytic activity of double perovskite oxides decreased.Therefore appropriate doping content is beneficial to enhance catalytic activity.更多还原