乙硫醇在MFI和MOR沸石中扩散行为的分子动力学模拟

采用分子动力学方法模拟计算了乙硫醇分子在MFI和MOR两种拓扑结构沸石中的动力学性质，比较了乙硫醇不同负载量和沸石晶格原子刚性和柔性两种状态下乙硫醇分子在沸石孔道中扩散系数的大小。模拟结果表明，对于这两种沸石，负载量增加，扩散系数减小。对于MFI沸石，在刚性和柔性沸石结构的情况下，扩散系数分别为3×10－10m2/s和4×10－9m2/s；对于MOR沸石，在刚性和柔性结构的情况下，扩散系数分别为2×10－7m2/s和3×10－8m2/s。对于MFI沸石，柔性结构下的扩散系数比刚性结构下的扩散系数要大，而对于MOR却呈现出相反的行为。对比这两种沸石，MOR中的扩散系数要比MFI沸石中大，这是因为乙硫醇分子在MOR12元环中扩散更易进行所致。相互作用能的计算结果表明，MFI中交叉型和直型孔道活性位相近，MOR孔道中12元环与4元环孔道相差较大。

Molecular simulation of ethanethiol diffusion in MFI and MOR zeolites

The diffusion of ethanethiol in MFI and MOR was investigated by Molecular Dynamics (MD). The results show that the diffusion coefficient decreases with an increase in the quantity of ethanethiol adsorbed. The zeolites of flexible and inflexible structures are different in diffusion coefficient. For MFI, the diffusion coefficients in flexible and inflexible structures are 3×10－10m2/s and 4×10－9m2/s, respectively; this order is reversed for MOR, the diffusion coefficients in flexible and inflexible structures are 2×10－7m2/s and 3×10－8m2/s, respectively. The diffusivity of ethanethiol in flexible MOR is higher than that in flexible MFI, because the 12 member ring in MOR is larger than the 10 member ring in MFI. For MFI, the adsorptive sites in both intersection channel and straight channels are similar in the energy of interaction; for MOR, however, some differences occur between 12 member ring and 4 member ring.