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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Development of a new analysis method evaluating adsorption energies for the respective ion-exchanged sites on alkali-metal ion-exchanged ZSM-5 utilizing CO as a probe molecule: IR-spectroscopic and calorimetric studies combined with a DFT method
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Development of a new analysis method evaluating adsorption energies for the respective ion-exchanged sites on alkali-metal ion-exchanged ZSM-5 utilizing CO as a probe molecule: IR-spectroscopic and calorimetric studies combined with a DFT method

机译：以CO为探针分子的碱金属离子交换ZSM-5离子交换位点吸附能的新分析方法的开发：结合DFT方法的红外光谱和量热研究

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摘要

For alkali-metal ion-exchanged ZSM-5 zeolites (MZSM-5; M: Li, Na, K, Rb, Cs) the analysis of ion-exchangeable sites was performed by means of a combined method based on IR spectroscopic and calorimetric measurements using CO as the probe molecule. The heat of adsorption of CO was found to be correlated with an IR frequency of stretching vibration of C-O in the adsorbed species. It was revealed that there exists at least two types of sites capable of ion-exchanging; for the lithium ion-exchanged ZSM-5 (LiZSM-5) CO adsorption on each type of site is evaluated to give a set of IR bands and heats of adsorption, 2195 cm~(-1) and 49 kJ mol~(-1), 2185 cm~(-1) and 39 kJ mol"1 with the aid of the newly developed method utilizing the data obtained from a combined microcalorimetric and IR-spectroscopic study. Such types of data were also obtained for Na- and K-ion-exchanged ZSM-5 samples. Furthermore, a linear relationship between the differential heat of adsorption (q_(diff)) evaluated and the shift of wavenumber of the C-O stretching vibration from that of a gaseous CO molecule (Δv) was established for the systems of MZSM-5-CO, and the bonding nature of the CO molecule with each site can be explained in terms of the electrostatic force. The model of each adsorption site was also examined by the quantum calculation method (density functional theory: DFT). The trends obtained from the experimental data may be substantially supported by the calculation method even adopting a model as simple as the ZSM-5-type zeolite: the composition of MAlSi4O4H12.
机译：对于碱金属离子交换的ZSM-5沸石（MZSM-5; M：Li，Na，K，Rb，Cs），通过基于红外光谱和量热法的组合方法对离子交换位进行分析使用CO作为探针分子。发现CO的吸附热与被吸附物质中C-O的拉伸振动的IR频率相关。揭示了至少存在两种​​类型的能离子交换的位点;评估锂离子交换的ZSM-5（LiZSM-5）在每种类型的位点上的CO吸附，以给出一组IR带和吸附热，分别为2195 cm〜（-1）和49 kJ mol〜（-1 ），2185 cm〜（-1）和39 kJ mol“ 1借助于新开发的方法，利用微量热法和IR光谱研究相结合的数据。还获得了Na-和K-离子交换的ZSM-5样品，此外，建立了评估的吸附差热（q_（diff））与CO拉伸振动波数从气态CO分子的波数（Δv）之间的线性关系。 MZSM-5-CO的体系，可以用静电力来解释CO分子与每个位点的键合性质，还可以通过量子计算方法（密度泛函理论：DFT）研究每个吸附位点的模型。从实验数据获得的趋势可能会得到计算方法的充分支持d甚至采用与ZSM-5型沸石一样简单的模型：MAlSi4O4H12的组成。

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