Combined study of IRMS-TPD measurement and DFT calculation on Bronsted acidity and catalytic cracking activity of cation-exchanged Y zeolites
Combined study of IRMS-TPD measurement and DFT calculation on Bronsted acidity and catalytic cracking activity of cation-exchanged Y zeolites
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DOI：
10.1016/j.jcat.2008.08.004
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发表时间：
2008-10-25
影响因子：
7.3
通讯作者：
Niwa, Miki
中科院分区：
文献类型：
--
作者：
Noda, Takayuki;Suzuki, Katsuki;Niwa, Miki
将氨红外光谱/质谱-程序升温解吸应用于 Ba、Ca 和 La 交换 Y 沸石，详细测量布朗斯台德酸度，并深入了解其与催化裂化活性的关系。结果发现，引入的阳离子优先位于位点I'和/或II，取代了方钠石笼和六方棱柱中的OH，从而激活了超级笼中的布朗斯台德OH。通过密度泛函计算从理论上证实了由于极化效应而引入的金属阳离子增强了布朗斯台德·OH的酸强度。辛烷裂解速率随着阳离子交换的增加而增加，并且基于超级笼中活性布朗斯台德OH数量的转换频率与布朗斯台德酸位点的强度相关。因此，清楚地揭示了金属阳离子在Y沸石的布朗斯台德酸性中的作用。 (C) 2008 Elsevier Inc. 保留所有权利。
Ammonia infrared spectroscopy/mass spectroscopy-temperature programmed desorption was applied to Ba-, Ca-, and La-exchanged Y zeolites to measure the Bronsted acidity in detail and to gain insight into its relationship to catalytic cracking activity. It was found that the introduced cation located preferentially on sites I' and/or II replaced the OH in the sodalite cage and hexagonal prism, thereby activating the Bronsted OH in the super cage. The acid strength of Bronsted OH enhanced by the introduced metal cation due to the polarizing effect was confirmed theoretically by density functional calculations. The rate of octane cracking increased with increasing cation exchange, and the turnover frequency on the basis of the number of the active Bronsted OH in the supercage was correlated with the strength of the Bronsted acid site. Thus, the roles of metal cations in Bronsted acidity of Y zeolite was clearly revealed. (C) 2008 Elsevier Inc. All rights reserved.