Molecular Simulations of Adsorption and Diffusion Behaviors of Benzene Molecules in NaY Zeolite

Abstract

In the article the Grand Canonical Monte Carlo (GCMC), molecular dynamics (MD), and kinetic Monte Carlo (KMC) simulations with particular focus on ascertaining the loading dependence of benzene diffusion in the zeolite were performed. First, a realistic representation of the structure of the sorbate-sorbent system was obtained based on GCMC simulation. The simulation clearly shows the characteristics of the adsorption sites of the benzene-NaY system, from which two kinds of preferably adsorbing sites for benzene molecules, called S II and W sites, are identified. The structure thus obtained was then used as a basis for KMC and MD simulations. A comparative study by introducing and comparing two different mechanisms underlying jump diffusion in the zeolite of interest shows that the MS diffusivity values predicted by the KMC and MD methods are fairly close to each other, leading to the conclusion that for benzene diffusion in NaY, the S II→W→S II jumps of benzene molecules are dominated, while the W→W jumps do not exist in the process. These findings provide further support to our previous conclusion about the absence of the W→W jumps in the process of benzene diffusion in NaY. Finally, two relations for predicting the self- and MS diffusivities were derived and found to be in fair agreement with the KMC and MD simulations.