钙钛矿型化合物催化氧化性能与d电子构型关系的研究

Study on the Correlation of d-electron Configuration and Catalytic Oxidation Activity of LaMO_3 Compounds

我们用活性评价、磁性测定、原子吸收光谱、TPR(程序升温还原)、TPSR(程序升温表面反应)、XRD等手段研究了以共沉淀和混合法制备的LaMO_3(M为从钛到铜的八个过渡金属离子)钙钛矿型化合物对GH_4和CO的催化氧化性能.结果表明,随M离子的d电子数增多,催化剂的催化氧化活性呈现三峰变化模式并与表面氧结合能及TPSR活性氧物种分布规律一致.根据磁性分析了M离子d电子组态,对活性的三峰现象作了说明.比较了不同方法对催化剂上氧物种的表征效果.考察了在氧化还原气氛下M离子价态变化规律.根据实验结果讨论了催化剂上活性氧物种分布.

The catalytic activity for CH_4 and CO oxidation of LaMO_3 (M is transition metal ion) perovskite-type oxide prepared by coprecipitation and mixing methods has been studied by activity evaluation, magnetic measurement, element analysis, TPE, TPSE and XED. According to the 3d-electron configuration of M ion determined by magnetic measurement, an explaination has been put up to the results which show a tri-peak pattern for 3d-electron number vs catalytic activity. Proportional relations have been found between catalytic activity and either surface oxygen bonding energy or TPSE active oxygen content in LaMO_3 compounds. The valence of M ions in catalysts varies under redox atmosphere in the following circle, M^(3+)→M^(n+)→M^(3+), and, for Ti and V, n>3; for Or, n=3; for the others, n<3. The active oxygen distribution in the series oxides has been discussed.