Silylated ionic liquid (IL)-derived organosilica membrane was formed on porous Al2O3 substrate by the sol-gel method. The permeation and separation characteristics for a binary toluene/CH4 mixture were studied at various temperatures. The membrane showed selective permeation of toluene against CH4 at high temperature up to 170 °C, and stably separated toluene from CH4 at 150 °C for 3 h. The permselectivity was strongly controlled by the affinity of the permeate molecules toward the IL. The results showed that the silylated IL-derived organosilica membrane is promising for selective recovery of aromatic hydrocarbons from CH4. ATR-IR, N2 adsorption and nanopermporometry were performed to evaluate the microstructure and permeation mechanism of the organosilica membrane. These characterizations revealed that the membrane depended on two permeation pathways, "only the dense IL regions" and "organosilica network-derived micropores dense IL regions." The organosilica membrane contained about 1 nm-sized pores, and the contributions of two permeation pathways to gas permeation were successfully evaluated.

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.