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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Resonant Diffusion of Normal Alkanes in Zeolites: Effect of the Zeolite Structure and Alkane Molecule Vibrations
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Resonant Diffusion of Normal Alkanes in Zeolites: Effect of the Zeolite Structure and Alkane Molecule Vibrations

机译：正常烷烃在沸石中的共振扩散：沸石结构和烷烃分子振动的影响

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摘要

Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient varies periodically with the number of carbon atoms of the alkane molecule, a phenomenon called resonant diffusion. A criterion for observable resonance is obtained from the balance between the interaction potentials of the molecule due to the atomic and pore structures of the zeolite. It shows that the diffusion is not resonant in zeolites with no periodic variance of the pore cross-sectional area along the length of the channel such as ZSM-12. Moreover, even in zeolites with periodic sequence of channels and cavities no resonant dependence of the diffusion constant can be detected if the pore structure energy barriers are not at least three times higher than the atomic structure energy barriers. The role of the alkane molecule vibrations is examined as well, and a surprising effect of suppressing the diffusion in comparison with the case of a rigid molecule is observed. This effect is explained with the balance between the static and dynamic interaction of the molecule and zeolite.
机译：理论上，在随机方程形式主义的基础上研究了正构烷烃在一维沸石中的扩散。计算出的扩散系数考虑了扩散分子和沸石骨架的振动，分子与沸石的相互作用以及沸石的特定结构。结果表明，当相互作用势主要由沸石孔结构决定时，扩散系数随烷烃分子碳原子数的变化而周期性变化，这种现象称为共振扩散。由分子的相互作用势之间的平衡获得了可观察到的共振的标准，所述分子是由于沸石的原子和孔结构而引起的。这表明在诸如ZSM-12之类的通道长度上，孔横截面积没有周期性变化的沸石中的扩散不是共振的。而且，即使在具有周期性的通道和腔序列的沸石中，如果孔结构能垒不比原子结构能垒高至少三倍，也不能检测到扩散常数的共振依赖性。还检查了烷烃分子振动的作用，并且与刚性分子相比，观察到令人惊讶的抑制扩散的效果。通过分子与沸石之间的静态和动态相互作用之间的平衡来解释这种效果。

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