Gas Diffusion in Polycrystalline MFI-type Zeolite Membranes

1. Introduction 1. Introduction Information on mass transport in polycrystalline zeolite membranes is necessary for a theoretical estimation of the membrane performances. Zeolite membranes are usually prepared as thin layer of an assembly of small zeolite crystals including many intercrystalline regions. Thus, the intercrystal region would influence their individual diffusion properties, which would differ from that in a single crystal. Characterization of the intercrystalline region by direct experimental methods is sometimes difficult because of their too small size to observe that is in the range of a few nanometers. Therefore, the investigation on the relationship between the structure of the intercrystalline region in the zeolite membranes and the diffusion properties are still limited [1], and it is not fully understood. In this study, we carried out 1 H pulse gradient-field spin-echo (PFG) NMR to obtain a diffusion coefficient of methane in MFI-type silicalite zeolite membranes, whose properties have been characterized to understand the feature of gas diffusion in polycrystalline zeolite.