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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Combined theoretical and FTIR spectroscopic studies on hydrogen adsorption on the zeolites Na-FER and K-FER
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Combined theoretical and FTIR spectroscopic studies on hydrogen adsorption on the zeolites Na-FER and K-FER

机译：理论和FTIR结合光谱研究Na-FER和K-FER沸石上的氢吸附

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摘要

The interaction between molecular hydrogen and the alkali-metal-exchanged zeolites Na-FER and K-FER at a low temperature was investigated by combining variable-temperature infrared spectroscopy and theoretical calculations by using a periodic DFT model. The experimentally determined values of standard adsorption enthalpy, Delta H degrees, were -6.0 (+/- 0.8) and -3.5 (+/- 0.8) kJ mol(-1) for Na-FER and K-FER, respectively. These results were found to be in agreement with corresponding Delta H degrees values obtained from calculations on the periodic model. Two types of alkali-metal cation sites in FER were found: channel intersection sites and channel wall sites. Calculations showed a similar interaction energy for both site types, and similar structures of adsorption complexes. Up to two dihydrogen molecules can be physisorbed on the alkali-metal cation located on the intersection of two channels, while only one H-2 molecule is physisorbed on the cation at the channel wall site. The adsorption enthalpies of H-2 on alkali-metal-exchanged FER are significantly smaller than those found previously for the MFI-type zeolites Na-ZSM-5 and K-ZSM-5, which is likely due to a difference in the alkali-metal cation coordination in the two zeolite frameworks.
机译：通过结合可变温度红外光谱和周期性DFT模型的理论计算，研究了分子氢与碱金属交换沸石Na-FER和K-FER在低温下的相互作用。 Na-FER和K-FER的标准吸附焓的实验确定值Delta H度分别为-6.0（+/- 0.8）和-3.5（+/- 0.8）kJ mol（-1）。发现这些结果与从周期性模型的计算获得的相应的ΔH度值一致。在FER中发现了两种类型的碱金属阳离子位点：通道相交位点和通道壁位点。计算表明两种位点类型的相互作用能相似，吸附络合物的结构相似。最多两个二氢分子可被物理吸附在位于两个通道交叉处的碱金属阳离子上，而只有一个H-2分子可被物理吸附在通道壁部位的阳离子上。 H-2在碱金属交换的FER上的吸附焓明显小于以前发现的MFI型沸石Na-ZSM-5和K-ZSM-5的吸附焓，这很可能是由于碱金属的差异所致。两个沸石骨架中的金属阳离子配位。

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