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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Is Kinetic Molecular Sieving of Hydrogen Isotopes Feasible?
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Is Kinetic Molecular Sieving of Hydrogen Isotopes Feasible?

机译：氢同位素动力学分子筛可行吗？

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摘要

We investigate the possibility of kinetic molecular sieving of hydrogen isotopes by studying their dynamical properties in the one-dimensional channels of microporous aluminophosphate AlPO4-25 at low temperatures. We use transition state theory as well as molecular dynamics simulations, using an effective quantum potential obtained via the Feynman—Hibbs path integral formalism. With the help of the free energy profile and barrier determined using the Widom particle insertion method, we demonstrate that transition state theory offers an effective and convenient method to determine self-diffusion coefficients, showing excellent agreement with those obtained from molecular dynamics simulations. Quantum-effect-induced kinetic molecular sieving, in which the heavier isotope (deuterium) diffuses faster than the lighter hydrogen, is observed at low temperature, consistent with our simulation results for narrow window zeolite-p, and experimental evidence with 3 A carbon molecular sieve in the recent literature. The free energy profile provides insight into this remarkable counterintuitive behavior, showing that at sufficiently low temperature the free energy barrier for diffusion is smaller for deuterium than hydrogen and exhibits inverse temperature dependence. These findings suggest low-temperature kinetic molecular sieving of hydrogen isotopes as an attractive route for their separation.
机译：我们通过研究氢同位素在低温下在微孔磷酸铝AlPO4-25的一维通道中的动力学特性来研究氢同位素动力学分子筛的可能性。我们使用过渡态理论以及分子动力学模拟，使用通过费曼-希布斯路径积分形式主义获得的有效量子势。借助使用Widom粒子插入方法确定的自由能分布和势垒，我们证明了过渡态理论提供了一种确定自扩散系数的有效且便捷的方法，与分子动力学模拟获得的结果非常吻合。在低温下观察到量子效应诱导的动力学分子筛，其中较重的同位素（氘）比较轻的氢扩散快，这与我们对窄窗沸石-p的模拟结果和3 A碳分子的实验证据一致筛查最近的文献。自由能曲线提供了对这种非直觉行为的洞察力，表明在足够低的温度下，氘的扩散自由能垒比氢小，并且表现出反温度依赖性。这些发现表明，氢同位素的低温动力学分子筛是分离它们的诱人途径。

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