Evaluation of Permeation Mechanisms of Silylated Ionic Liquid-derived Organosilica Membranes for Toluene/Methane Separation

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.