Citation: She Li-Qin, Wang Duo-Cai, Li Xuan-Wen, Liu Xing-Yun, Han Ming. The States of Zinc in ZnZSM-5 Zeolites and their Catalysis[J]. Acta Physico-Chimica Sinica, 1994, 10(03): 247-253. doi: 10.3866/PKU.WHXB19940311
锌在ZnZSM-5沸石中的形态及其催化作用
采用NH_3－TPD和吡啶吸附红外光谱法，研究了不同含Zn量ZnHZSM-5沸石中Zn的存在状态．结果表明，用浸渍方式将Zn引入到HZSM-5沸石后，在NH_3－TPD谱上产生两个新的NH_3脱附峰．峰位分别在原HZSM－5沸石的低温峰与高温峰之间和比高温峰较高温区处，其相应的吸附中心分别以L_1、L_2表示．L_1可能与ZnHZSM－5沸石上ZnO物种相对应; L_2与吡啶吸附红外光谱的L_(1616)吸收带有关，可能与ZnHZSM-5上的ZnOH~＋物种相对应．丙烷芳构化反应结果表明，芳烃收率随L_2的脱附NH_3量的增加有一最宜值，而活性的稳定性则随之降低。
English
The States of Zinc in ZnZSM-5 Zeolites and their Catalysis
NH_3-TPD and pyridine adsorption IR spectroscopy techniques have been used to study the zinc states in ZnHZSM-5 zeolite containing various zine content. The results indicate that, in addition to two desorption peaks for HZSM-5 zeolite located at about 533 and 733 K, two new peaks located at about 573 and 873 K were observed. These new peaks are believed to be associated with two kinds of zinc sites designated by L_1, L_2. The adsorbed ammonia amount of L_2 corresponds to the amount of L_(1616) acid characterized by pyridine adsorption IR spectra for ZnHZSM-5 zeolite with various zinc contents. It is possible that there are two kinds of zinc states in ZnHZSM-5 zeolite. One kind of them is ZnO species with weak acidity, the other is ZnOH~+ species with strong acidity which can promote the activity and has an effect on stability of activity for aromatization of propane.
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Key words:
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ZnZSM-5
- / Propane
- / Aromatization
- / NH3-TPD
- / Pyridine adsorption IR spectra
- / Zeolite
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