关键词: 沸石ZSM-5, 动力学, 纳米粒子, 扩散, 活化能, 零长柱法（ZLC）

Abstract: In this study，the effect of pore structure on diffusion of two C7 hydrocarbons，n-heptane and toluene，which have the same number of carbon atoms and different diameters of molecular dynamics and structures，in nano-ZSM-5 materials were investigated using the zero-length column （ZLC） method. Furthermore，the corresponding MFI zeolite sample was also investigated using the same technique. The effective diffusion time constants of these two sorbates on ZSM-5 materials were evaluated by the Crank model，and the diffusion activation energies were estimated. The values of activation energy of diffusion of toluene were about 1.5 times higher than those of n-heptane，whereas the effective diffusion time constants of toluene were much smaller than those of heptane，which could be attributed to more complex structure and larger kinetic diameter of toluene. Diffusion rates of heptane and toluene depended on particle size of the nano-ZSM-5 crystal. Diffusion time constants of heptane and toluene in nano-ZSM-5 zeolite were found about 2 times higher in comparison to the corresponding MFI zeolite sample. However，diffusion activation energies for both C7 hydrocarbons in the MFI zeolite were about 2 times higher than those in the corresponding nano-ZSM-5 zeolite sample，which suggested that decrease of the diffusion path length within the microporous crystals by reducing the particle size could promote the process of diffusion.

Key words: zeolite ZSM-5, kinetics, nanoparticles, diffusion, activation energy, zero-length column