Insight into the Contribution of Isolated Mesopore on Diffusion in Hierarchical Zeolites: The Effect of Temperature

In recent years, hierarchical zeolites are becoming more and more attractive as a solution to the diffusion restraint of classical zeolites. There have been many theoretical as well as experimental developments that deepened our understanding of mass transfer phenomena in hierarchical materials. However, there appears to be no consensus on the role that disconnected mesopores played in molecular transport. In this paper, molecular simulation is conducted to study the diffusion of benzene in purely microporous FAU zeolite and hierarchical FAU models which consist of both microporosities of FAU and a cylindrical mesopore with various radiuses (0.74-17.5 nm) at 300-800 K. The usage of the disconnected mesopores at moderate adsorbate loading is testified on the molecular level. In fact, under the reaction temperature of catalytic reactions, the disconnected mesoporous are likely to be fully utilized and beneficial to the reaction process. The temperature dependence illustrated shows a remarkably good agreement between the theoretical predictions and the experimental results. It therefore confirms that the disconnected mesopore may weaken and subdue the resistance of diffusion at high temperatures at moderate loading. Based on a thorough quantitative analysis of the adsorption interactions, the mechanisms leading to these phenomena are further explained.