PALLADIUM - PREPARATION AND CATALYTIC PROPERTIES OF PARTICLES OF UNIFORM SIZE
PALLADIUM - PREPARATION AND CATALYTIC PROPERTIES OF PARTICLES OF UNIFORM SIZE
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DOI：
10.1126/science.169.3948.873
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发表时间：
1970-01-01
期刊：
影响因子：
56.9
通讯作者：
KIM, G
中科院分区：
文献类型：
--
作者：
TURKEVICH, J;KIM, G
本文介绍了一种制备直径为55 ~ 450埃的均匀钯颗粒的方法。还合成了在钯上分层的金的均匀颗粒。氢氧化铝溶胶的水热处理用于制备具有100至500埃的均匀横截面和不同长度的氧化铝棒。钯作为单独的颗粒吸附在氧化铝棒上，两者都存在于水悬浮液中。然后将悬浮液干燥，得到含有均匀尺寸的金属颗粒的催化剂，所述金属颗粒分散在由氧化铝棒的相互啮合产生的开孔中。这一程序保证了实验观察到的反应速率中不存在扩散控制。用电子显微镜监测制备的所有阶段。用脉冲技术研究了乙烯-氢反应的动力学。通过表面的一氧化碳滴定确定的活性位点的数目等于通过计算合成中涉及的化合物的量和电子显微镜检查确定的表面原子的数目。此外，每个位点的活性取决于制备方法，当甲酸钠代替柠檬酸钠用作还原剂时，活性小四倍。这可能是由于粒子的形状使某些晶面更有利。颗粒尺寸减小到56埃后，由于表面原子数的增加，对催化活性没有影响。用氧化铝稀释100倍的市售5%钯/氧化铝的活性得到丙烯的80.4%转化率和乙烯的82.7%转化率。因此，两种烯烃的行为几乎没有差异。
A method has been developed for the preparation of uniform palladium particles of diameter from 55 to 450 angstroms. Uniform particles of gold layered on palladium were also synthesized. Hydrothermal treatment of aluminum hydroxide sol was used to prepare rods of alumina with uniform cross section from 100 to 500 angstroms and of varying lengths. The palladium was adsorbed as individual particles on alumina rods, both present in aqueous suspension. Then the suspension was dried to give a catalyst containing metal particles of uniform size dispersed in open pores produced by the intermeshing of the alumina rods. This procedure guaranteed the absence of diffusion control in the rate of reactions observed experimentally. All stages of the preparation were monitored with the electron microscope. The kinetics of the ethylene-hydrogen reaction were examined by means of a pulse technique. The number of active sites determined by carbon monoxide titration of the surface was equal to the number of surface atoms as determined by the calculation of the quantities of compounds involved in the synthesis and electron microscope examination. Furthermore, the activity per site depended on the method of preparation, being four times smaller when sodium formate was used as a reducing agent instead of sodium citrate. This may be due to the fact that the shape of particles makes certain crystallographic planes more favorable. Decrease in the size of particles to 56 angstroms produced no effect on catalytic activity beyond that due to the increase in the number of surface atoms. The activity of commercial 5 percent palladium on alumina diluted 100-fold with alumina gave 80.4 percent conversion with propylene and 82.7 percent conversion with ethylene. Thus there was little difference in the behavior of the two olefins.