Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy
Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy
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DOI：
10.1006/jcat.1996.0389
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发表时间：
1996-12
影响因子：
7.3
通讯作者：
L. Liotta;G. Deganello;P. Delichère;Christiane Leclercq;G. Martin
中科院分区：
文献类型：
--
作者：
L. Liotta;G. Deganello;P. Delichère;Christiane Leclercq;G. Martin
用低能离子散射（LEIS）和透射电镜（TEM）研究了三个系列的钯基催化剂。第一系列由Na-Pd/SiO2催化剂组成，通过将钯加入到二氧化硅载体上并进一步加入Na/Pd原子比（R）等于0、6.4和25.6的钠离子而获得。第二系列由负载在天然浮石上的钯催化剂组成，其中，由于负载的钯的不同负载量，R（Na+K）/Pd原子比等于17.0和39.4。第三系列由两种负载在{open_quotes}模型浮石上的钯基催化剂代表，{close_quotes}合成硅铝酸盐，通过溶胶-凝胶技术获得，具有不同量的钠，并且R分别等于2.1和6.1。LEIS实验和电子显微镜表明碱金属离子在前两个系列中的不同位置：在Na-Pd/SiO{sub 2}催化剂中，钠以不均匀的方式分布在载体上和钯金属上，钯金属部分用Na离子装饰，而在Pd/天然浮石系列中，钯表面不含钠。基于LEIS和TEM分析，第三系列催化剂Pd/模型浮石的结果不是确定的，但通过CO和CO{sub 2}吸附的FTIR研究，可以排除钠离子对钯的修饰。结果证实了碱金属离子的位置在碱促进的钯催化剂的重要性，并通过更好地控制促进剂的位置，在钯负载型催化剂的设计中打开了新的可能性。参考文献18篇，图5，2个标签。«少
Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminates, obtained by sol-gel techniques, with a different amount of sodium, and R equal to 2.1 and 6.1 respectively. LEIS experiments and electron microscopy demonstrate a different location of alkali metal ions in the first two series: in the Na-Pd/SiO{sub 2} catalysts sodium is distributed in a way which is not uniform on the support and on the palladium metal, which is partly decorated with Na ions, whereas in the Pd/natural-pumice series the palladium surface is sodium-free. The results on the third series of catalysts, Pd/model pumice, are not definitive on the basis of the LEIS and TEM analyses,more » but by FTIR study of CO and CO{sub 2} adsorption, the decoration of palladium by sodium ions could be excluded. The results confirm the importance of the alkali metal ion location in alkali-promoted palladium catalysts and open new possibilities in the design of palladium-supported catalysts by a better control of promoter location. 18 refs., 5 figs., 2 tabs.« less