Influence of temperatures and loadings on olefin diffusion in MFI-type zeolites in one- to three-dimensions

Abstract

A detailed understanding of the molecular diffusion in zeolite frameworks is crucial for analysing the factors controlling their catalytic performance in alkenes. In this work, we present a molecular dynamics study of propylene diffusion in acidic zeolite MFI in the temperature range of 453–653 K. Moreover, the effects of different temperatures and propylene loadings on olefin diffusion in the acidic zeolite MFI were considered. A detailed analysis of olefin deformation in one to three dimensions was performed to illustrate the anisotropy and influence of the olefin structure on its diffusion in zeolites. The propylene diffusion direction was elucidated by correlating the temperature with the diffusion coefficients of the straight and zigzag channels of the H-MFI zeolite. Furthermore, the analysis of the radial distribution function and Brønsted acid sites showed that the olefins interacted mainly with acidic protons and that the degree of clustering of olefin was higher at higher loadings. These results help understand the differences in the catalytic performance of zeolites in olefin reactions at different temperatures and loadings; are beneficial for understanding the catalytic activity, stability, and product distribution; and guide the design of catalysts with specific morphologies.