ITQ-3分子筛中甲烷和正丁烷混合物扩散性质的模拟

采用分子动力学方法先分别模拟了单组分的CH_4和C_4H_(10)在二维分子筛ITQ-3中的自扩散系数随负载N的变化。研究表明,在z轴方向的窄孔道中,自扩散系数随负载N的增加两者均表现出先增大后减小的扩散模式,而在y轴方向的宽孔道中,则随负载N的增加单调递减。之后,又模拟了二元组分CH_4和C_4H_(10)混合物在ITQ-3分子筛中随总原子数变化的扩散行为。结果发现,在z轴方向上,当负载N较小时,CH_4的扩散系数随总原子数的增多而增大;当负载N较大时,CH_4的扩散系数随总原子数的增多而减小。在y轴方向上,当负载N较小时,CH_4的扩散同z轴方向一样表现出随总原子数的增多而增大的现象,明显不同于单组分CH_4在y轴方向上的扩散;但随着负载N的增多,在z轴方向的孔道中发生堵塞效应的总原子数在y轴方向的孔道中仍处于过渡状态。

Molecular Dynamics Simulation on Diffusion Properties of methane and n-butane mixture in Zeolite ITQ-3

The molecular dynamics simulation was conducted to study the diffusion changes of single component CH4 and C4H10 in the two-dimensional zeolite ITQ-3 with the loading N. Studies showed that, in the narrow channel z direction, the self-diffusion coefficient is an increasing function as the loading N increases and then it decreases at a higher loading level. But in the wide channel y direction, the self-diffusion coefficient decreases monotonically with the loading N increases. Then the diffusion coefficients of binary components CH4 and C4H10 mixture in zeolete ITQ-3 had been studied using molecular dynamic simulation methods. It was found that, in the z direction, the diffusion coefficient of CH4 increases with the increase of the total number of atoms when the loading N is small but decreases when the loading N is large. In the y direction, when the loading N is small, it exhibits the same phenomenon as z direction that the diffusion coefficient of CH4 increases with the increases of the total number of atoms, it was obviously different from the study of the diffusion in the y direction of single component CH4.However, with the increases of loading N, the total number of atoms that lead to the blocking effect in the tunnel of z direction is still in a transition state in the tunnel of y direction.