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本文主要研究LaCoO_3及其掺杂化合物对CO的催化氧化性能。全部试样均采用柠檬酸络合法合成。考察了氧化(或还原)预处理及掺杂非三价A离子对催化活性的效应,尤其是在不同反应温度区域所表现的效应。试验发现,LaCoO_3经氧化预处理后,在反应温度>220℃时才能提高催化活性,而经还原预处理的则在<220℃的温度下就能提高活性。随着反应温度的上升,以210～230℃为分界线,Sr~(2+)的掺杂效应从负变为正,而Ce~(4+)的掺杂效应则是由正变为负。认为预处理和掺杂效应均可从钴离子的价态变化,按高温时为内相反应、低温时为表面反应的机理来解释。研究了La_(1-x)Sr_xCoO_3中,x值变化对活性的影响。发现在不同温度时活性有极大值。将值化活性的变化与电磁性质的改变加以关联,认为d电子集体化程度亦可能是影响活性的原因之一。此外,本文还报导了采用混合稀土为A离子,用Fe、Mn或Ni为B离子时的研究结果。
In this paper, the catalytic oxidation of LaCoO_3 and its doped compounds for CO was studied. All samples were synthesized by citric acid complexation method. The effect of oxidation (or reduction) pretreatment and doping of non-trivalent A ions on the catalytic activity was investigated, especially in different reaction temperature regions. It was found that the catalytic activity of LaCoO_3 can be increased only when the reaction temperature is higher than 220 ℃ after the pretreatment of LaCoO_3, while the activity of LaCoO_3 can be increased under the temperature of <220 ℃. With the increase of reaction temperature, the doping effect of Sr ~ (2+) changes from negative to positive and the doping effect of Ce ~ (4 +) changes from positive to negative . It is considered that both the pretreatment and the doping effect can be explained from the valence state of cobalt ions, the internal phase reaction at high temperature and the surface reaction mechanism at low temperature. The effect of the change of x value on the activity of La_ (1-x) Sr_xCoO_3 was studied. It is found that the activity has a maximum at different temperatures. Associating the change of the value activity with the change of the electromagnetic property, we think that the degree of d-electron collectivization may also be one of the reasons that affect the activity. In addition, this paper also reports the results of a study using mixed rare earth A ions and Fe, Mn or Ni as B ions.