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Pd/Al_2O_3催化剂的制备通常包括浸渍、烘干、焙烧和还原等步骤。当改变pH值时,H_2PdCl_4溶液以及H_2PdCl_4-Al_2O_3样品的紫外吸收光谱发生变化。可能是H_2PdCl_4在Al_2O_3表面发生配位吸附。用光学显微镜、俄歇光谱、H_2-O_2滴定技术考察了H_2PdCl_4浸渍液的pH值变化时所制得的Pd/Al_2O_3催化剂表面性质发生的变化。TPSR的结果表明,钯的晶粒大小在34—75埃之间时,对CO的表面氧化反应影响不大。从俄歇线扫描发现壳型Pd/Al_2O_3催化剂在焙烧过程中金属钯向表层迁移。
The Pd / Al 2 O 3 catalyst is usually prepared by the steps of impregnation, drying, calcination and reduction. When the pH value is changed, the UV absorption spectra of H 2 PdCl 4 solution and H 2 PdCl 4 -Al 2 O 3 sample change. It is likely that H 2 PdCl 4 has a coordinated adsorption on the surface of Al 2 O 3. The changes of the surface properties of Pd / Al_2O_3 catalyst prepared by pH change of H_2PdCl_4 were investigated by optical microscope, Auger spectroscopy and H_2-O_2 titration. TPSR results show that when the grain size of palladium is between 34-75 angstroms, the surface oxidation of CO has little effect. From the Auger line scan, it was found that the shell Pd / Al 2 O 3 catalyst migrated to the surface during the calcination.