Citation: Li Guang-Jin, Yang Ya-Shu, Guo Xie-Xian, Ichikawa Masaru. Dispersion of Catalysts Derived from Intrazeolite Pt Carbonyl Clusters[J]. Acta Physico-Chimica Sinica, 1994, 10(06): 549-554. doi: 10.3866/PKU.WHXB19940613
由分子筛笼内铂羰基簇合物得到的催化剂的分散度研究
由分子筛笼内包容的铂羰基簇合物[Pt_(12)(CO)_(24)]~(2-)/NaY和[Pt_9(CO)_(18)]~(2-)/NaY经还原得到的样品Pt_(12)/NaY和Pi_9/NaY的分散度用EXAFS和化学吸附进行了表征．对Pt_(12)/NaY和Pi_9/NaY，EXAFS分析分别给出R_(Pt－Pt)＝0.274 nm，配位数C.N.＝0.42和R_(Pt－Pt)＝0.274 nm配位数C.N.＝3.8，而化学吸附结果分别为H/Pt＝1.26，CO/Pt＝0.69和H/Pt＝1.24，CO/Pt＝0.64．与浸渍法制备的Pt/Al_2O_3相比小得多的Pt－Pt配位数及大的化学吸附值说明，由分子筛笼内铂羰基簇合物出发，我们得到了高分散的Pt/NaY催化剂．由于还原后原子堆积形式的变化，Pt_(12)/NaY和Pt_9/NaY的再还原羰基化不能可逆地得到与前驱体相同的铂羰基簇合物．
English
Dispersion of Catalysts Derived from Intrazeolite Pt Carbonyl Clusters
The catalysts derived from the reduction of intrazeolite Pt carbonyl clusters [Pt_(12)(CO)_(24)]~(2-)/NaY and [Pt_9(CO)_(18)]~(2-)/NaY were characterized by EXAFS and chemisorption techniques. EXAFS analysis gave R_(Pt-Pt)=0.274 nm, C.N.=4.2 for Pt_(12)/NaY and R_(Pt-Pt)=0.274 nm, C.N.=3.8 for Pt_9/NaY, whil the chemisorption of H_2 and CO gave H/Pt=1.26, CO/Pt=0.69 and H/Pt=1.24, CO/Pt=0.64 for Pt_(12)/NaY and Pt_9/NaY respectively. Compared with the results of Pt/Al_2O_3, it is concluded that highly dispersed Pt/NaY catalysts were derived from the intrazeolite Pt carbonyl clusters. Because of the structureal changes of reduced Pt carbonyl clusters, the recarbonylation of Pt_(12)/NaY and Pt_9/NaY can not regenerate the same Pt carbonyl clusters as their precursors.
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Key words:
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Zeolites
- / Pt
- / Carbonyl clusters
- / Dispersion
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