Differentiating Diffusivity in Different Channels of ZSM‐5 Zeolite by Pulsed Field Gradient (PFG) NMR.

Differentiating the diffusivity in straight channel and sinusoidal channel of ZSM‐5 zeolite is a prerequisite for catalyst optimization for the required product distribution with specific orientation. Herein, the intracrystalline diffusivities of n‐butane and iso‐butane in power ZSM‐5 zeolite were investigated by pulse field gradient (PFG) NMR, respectively. Different diffusion behaviors of the selected isomers were revealed. The effective self‐diffusion coefficient of n‐butane is about three orders of magnitude higher than that of iso‐butane. For the selected isomers, the opposite loading‐dependence were presented in self‐diffusion coefficients. Moreover, an equation containing diffusion tensors in different directions in orthogonal coordinate was successfully applied to fit the diffusion coefficients of n‐butane in straight and sinusoidal channel of ZSM‐5, respectively. The diffusivity of n‐butane in straight channel is nearly one order of magnitude faster than that in sinusoidal channel, predicting its dominant diffusion path. [ABSTRACT FROM AUTHOR]