Coppens Marc-Olivier, Iyengar Vijay
Nanotechnology. 2005 Jul;16(7):S442-8. doi: 10.1088/0957-4484/16/7/020. Epub 2005 May 18.
The Maxwell-Stefan (MS) formulation, as applied to zeolites that contain both weak and strong adsorption sites, such as ZSM-5, is compared to dynamic Monte Carlo simulations, for the limiting case of single-component self-diffusion. This study is intended as a consistency check, and as a step towards an analytical or semi-analytical theory for self-diffusion in zeolites with multiple types of sites. In its original form, when it is assumed that ζ, the ratio of the self-exchange coefficient to the corrected diffusivity, is equal to 1, the MS formulation performs well for silicalite, the all-Si version of ZSM-5. However, when there are lattice heterogeneities or the topology of the pore network differs from that of silicalite, it is necessary to assume [Formula: see text]. Because ζ is generally occupancy dependent, the theory is unsuited as a fully predictive theory for self-diffusion in heterogeneous microporous solids, unless a theory for ζ is derived. However, since several studies have demonstrated that the MS formulation is able to predict multi-component diffusivities from single-component diffusivities for zeolites with one type of site, an extension to zeolites with multiple types of sites would be very valuable.
将麦克斯韦 - 斯蒂芬（MS）公式应用于含有弱吸附位点和强吸附位点的沸石（如ZSM - 5），针对单组分自扩散的极限情况，与动态蒙特卡罗模拟进行了比较。本研究旨在进行一致性检验，并朝着建立具有多种类型位点的沸石中自扩散的解析或半解析理论迈出一步。在其原始形式中，当假设自交换系数与校正扩散率的比值ζ等于1时，MS公式对ZSM - 5的全硅版本硅沸石表现良好。然而，当存在晶格不均匀性或孔网络拓扑结构与硅沸石不同时，有必要假设[公式：见原文]。由于ζ通常取决于占有率，该理论不适用于作为非均质微孔固体中自扩散的完全预测理论，除非推导出ζ的理论。然而，由于多项研究表明，MS公式能够从具有一种类型位点的沸石的单组分扩散率预测多组分扩散率，因此将其扩展到具有多种类型位点的沸石将非常有价值。
