Supported protic-ionic-liquid membranes with facilitated transport mechanism for the selective separation of CO2

In this work, four diamine-monocarboxylate-based protic ionic liquids (PILs) were firstly introduced to prepare supported ionic liquid membranes (SILMs) and the selective separation of CO2/N2 and CO2/CH4 gas pairs in these SILMs under humidified condition were investigated. The effects of transmembrane pressure and temperature on the permeablity of CO2 and the permselectivity of CO2/N2 and CO2/CH4 gas pairs were also studied. It is found that the supported PILs with 15 wt% water exhibit much higher CO2 permeabilities under humidified conditon than those pure PILs under dry condition. The permeability increases with the decreasing transmembrane pressure, indicating a typical feature of facilitated transport membrane. The permeability of CO2 increases with the increasing temperature whereas the permselectivity of CO2/N2 and CO2/CH4 decreases at the same time. The highest CO2/N2 selectivities obtained is 151, and the highest CO2/CH4 selectivities is 72. These PILs is found to be tunable and selective carriers of CO2 in the presence of water, and the supported protic-ionic liquid membranes exhibit competitive permeability and higher permselectivity in comparison with the supported aprotic- ionic- liquid membranes.