期刊
MICROPOROUS AND MESOPOROUS MATERIALS
卷 125, 期 1-2, 页码 3-10出版社
ELSEVIER
DOI: 10.1016/j.micromeso.2009.01.025
关键词
Frequency response; Particle size distribution; MFI-type zeolites; Aromatics; Intra-crystalline diffusion
类别
资金
- Deutsche Forschungsgemeinschaft DFG [JE260-7/1, JE260-8/1]
The diffusion of alkyl-substituted aromatic molecules in H-ZSM-5 was investigated by means of the frequency response method decoupling particle size effects and intracrystalline diffusion. For zeolite crystals above 5 mu m average diameter, the transport in the zeolite pores exerts a significant effect on the overall transport causing anisotropic diffusion as the aspect ratio of the aromatic molecules increases. Diffusion of benzene is nearly isotropic, while p-xylene shows marked differences between the diffusive processes in the straight and sinusoidal channel system of ZSM-5. The isotropic diffusion of benzene is rationalized on the basis of its ability to reorient between the two channel systems without major hindrances. For p-xylene, switching between the channels is only possible by energetically unfavorable rotational motions leading to a low probability for changing between both channel systems. (C) 2009 Elsevier Inc. All rights reserved.
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