Development of Organosilica Membranes with Ionic Liquid-like Properties and Application to Organic Vapor Separation

Abstract

This review discusses the permeation and separation characteristics, the microstructure and the permeation mechanisms of organosilica membranes with ionic liquid (IL)-like properties, prepared from silylated ILs. The permeation and separation characteristics for binary toluene/H₂ mixture, methanol synthesis gas/vapor mixtures, binary toluene/CH₄ mixture and binary methanol/CH₄ mixture were studied. The membranes showed selective permeation of toluene and methanol against H₂, CO₂ and CH₄ at temperatures over 100 °C. The permselectivities were strongly controlled by the affinity of the permeated molecules for the ILs. The results showed that silylated IL-derived organosilica membranes show potential for selective recovery of organic vapors from inorganic/organic gases. Attenuated total reflectance infrared spectroscopy, N₂ adsorption, gas/vapor permeation tests and nanopermporometry were also performed to evaluate the microstructure and permeation mechanisms of the new concept of organosilica membranes. The membrane depended on two permeation pathways, “only the dense IL regions” and “organosilica network-derived micropores + dense IL regions.” Furthermore, the contributions of two permeation pathways to gas permeation were successfully evaluated based on the nanopermporometry characteristics.