Effects of the Si–O–Si Network Structure on the Permeation Properties of Silylated Ionic Liquid-Derived Membranes

Abstract

We previously reported the permselectivities, microstructure, and permeation mechanisms of ionic silsesquioxanebased membranes, which are a class of chemically stabilized ionic liquid (IL) membranes, prepared from ionic trialkoxysilanes (i.e., silylated ILs (T-type)) via the sol-gel method. These membranes comprise dense IL regions and Si-O-Si network-derived micropores, and their permeation characteristics depended on the two permeation pathways. Establishing a method for control the permeation characteristics of silylated IL-derived membranes is important for application expansion. Therefore, in this study, an ionic dialkoxysilane (i.e., silylated IL (D-type))-derived membrane was developed, and the e ects of the Si-O-Si network structure on its permeation characteristics are discussed. Attenuated total re ectance infrared spectroscopy, N 2 adsorption, and nanopermporometry characterizations revealed that the structure of the newly developed membrane was consistent with the Si-O-Si linear structures and Si-O-Si rings, but not the Si-O-Si network-derived micropores. Both membranes showed selective methanol permeation against H 2 at temperatures up to 473 K, but the calculation of the activation energy for methanol permeation clearly suggested that the IL-like properties of ionic dialkoxysilane-based membranes were better than those of the ionic silsesquioxane-based membranes with respect to methanol permeation.

An Experimental Study of a Zeolite Membrane Reactor for Reverse Water Gas Shift

“…Consequently, the permeations of the other gases were blocked by adsorbed H 2 O. Sawamura et al reported that the ZSM-5 membrane showed both H 2 O selectivity for a H 2 O/H 2 mixture and methanol selectivity for a methanol/H 2 mixture, similarly [10]. In addition, it is known that such affinity-based separation occurred in propylene/propane separation through Ag + -zeolite membrane and toluene/CH 4 separation through an ionic liquid-containing silica membrane [13][14][15][16]. In principle, the adsorption amount of H 2 O in micropore decreased at higher temperatures, resulting in less blocking for gas permeation and lower separation performance.…”