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

Abstract 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 CO 2 /N 2 and CO 2 /CH 4 gas pairs in these SILMs under humidified condition were investigated. The effects of transmembrane pressure and temperature on the permeablity of CO 2 and the permselectivity of CO 2 /N 2 and CO 2 /CH 4 gas pairs were also studied. It is found that the supported PILs with 15 wt% water exhibit much higher CO 2 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 CO 2 increases with the increasing temperature whereas the permselectivity of CO 2 /N 2 and CO 2 /CH 4 decreases at the same time. The highest CO 2 /N 2 selectivities obtained is 151, and the highest CO 2 /CH 4 selectivities is 72. These PILs is found to be tunable and selective carriers of CO 2 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.