摘要
本文用ＥＳＲ谱和ＸＰＳ谱对这类催化剂作了表征研究。结果表明，在经Ａｌ￣（３＋）掺杂的ＺｎＯ－Ａｌ_２Ｏ_３体系上，观测到ｇ＝１．９６０６±０．０００２，△Ｈ_（ｐｐ）＝（２．８±０．１）×１０￣（－４）Ｔ的顺磁信号，该信号强度（以自旋数／克表示）随ＺｎＯ中Ａｌ_２Ｏ_３掺杂量增加而增长；当Ａｌ／Ｚｎ达２／１００（原子比）时，逐渐趋于平稳。相关体系的ＥＳＲ和ＸＡＥＳ比较研究结果排除了该顺磁信号系产生于顺磁氧物种（诸如，Ｏ_２－、Ｏ－或Ｏ_３－）或Ｚｎ＋的可能性，而有利于关于三价金属离子（ＡＬ￣（３＋））掺杂在ＺｎＯ晶格中诱导生成正一价缺位的推断。这类Ｓｈｏｔｔｋｙ缺位在催化剂表面富集，有利于表面Ｃｕ￣＋物种的稳定，从而促进了ＣＯ加氢活性的提高。
Characterization studies of ZnO and Al_2O_3-doped ZnO, which are well-known to be the important components of Cu-based catalyst for methanol synthesis, have been carried out by means of ESR,XPS and XAES spectroscopies. The results indicated that an ESR signal was observed on the Al_2O_3-doped ZnO with g=1.9606±0.0002 and AHpp=(2.8±0.1)×10-4 T,It was found that the signal intensity(shown in spin-number per gram sample) increased at first and then gradually approached a plateau when the atomic ratio of Al to Zn increased from zero to 2/100. By the comparative studies of these ESR and XEAS results, the possibility that the me mentioned ESR signal was due to some oxygencontaining radical(e,f.O_2￣-,O￣- or O_3￣-)and Zn￣+ may be ruled out. But this signal may be ascribed to the monovalent cationic vacancies formed by doping trivalent cation(Al￣(3+)) into the ZnO lattice.The results are in favor of the following inference : the solution of Al￣(3+)in a proper amount into the ZnO lattice will result in the formation of Shottky defects in the form of cationic vacancies. The Cu￣+ species in surface may be accommodated and stabilized better in these defects because they areeasily concentrated at the surface of ZnO. Thus, an enhancement in the activity of CO hydrogenation may be obtained over the Al￣(3+)-doped Cu-based catalyst.
出处
《分子催化》
EI
CAS
CSCD
1994年第1期58-62,共5页
Journal of Molecular Catalysis(China)
基金
厦门大学固体表面物理化学国家重点实验室资助
关键词
铜基
催化剂
甲醇
氧化锌
氧化铝
ESR, XPS, Copper-based caalysts, Lattice vacancy, ZnO,Al_2O_3.
