We have investigated the effect of molecular shape and charge asymmetry on the translation dynamics of confined hydrocarbon molecules having different shapes but similar kinetic diameters, inside ZSM-5 pores using molecular dynamics simulations. The mean square displacement of propane, acetonitrile, acetaldehyde, and acetone in ZSM-5 exhibit two different regimes - ballistic and diffusive/sub-diffusive. All the molecules except propane exhibit sub-diffusive motion at time scales greater than 1 ps. The intermediate scattering functions reveal that there is a considerable rotational-translational coupling in the motion of all the molecules, due to the strong geometrical restriction imposed by ZSM-5. Overall the difference in shape and asymmetry in charge imposes severe restriction inside the ZSM-5 channels for all the molecules to different extents. Further, the behavior of molecules confined in ZSM-5 in the present study, quantified wherever possible, is compared to their behavior in bulk or in other porous media reported in literature.

我们已经使用分子动力学模拟研究了分子形状和电荷不对称性对ZSM-5孔内形状不同但动力学直径相似的受限烃分子的平移动力学的影响。ZSM-5中丙烷，乙腈，乙醛和丙酮的均方排量表现出两种不同的模式-弹道和扩散/亚扩散。除丙烷外，所有分子在大于1 ps的时间尺度上均表现出亚扩散运动。中间的散射函数表明，由于ZSM-5施加的强烈的几何限制，所有分子的运动中都存在相当大的旋转-平移耦合。总体而言，电荷的形状和不对称性的差异对所有分子以不同程度在ZSM-5通道内施加了严格的限制。