Abstract
A novel polyimide of intrinsic microporosity (PIM-PI) was synthesized from a 9,1'-diisopropyl-triptycene-based dianhydride (TPDA) and dihydroxyl-functionalized 4,6-diaminoresorcinol (DAR). The unfunctionalized TPDA-m-phenylenediamine (mPDA) polyimide derivative was made as a reference material to evaluate the effect of the OH group in TPDA-DAR on its gas transport properties. Pure-gas permeability coefficients of He, H-2, N-2, O-2, CH4, and CO2 were measured at 35 degrees C and 2 atm. The BET surface area based on nitrogen adsorption of dihydroxyl-functionalized TPDA-DAR (308 m(2) g(-1)) was 45% lower than that of TPDA-mPDA (565 m(2) g(-1)). TPDA-mPDA had a pure-gas CO2 permeability of 349 Barrer and CO2/CH4 selectivity of 32. The dihydroxyl-functionalized TPDA-DAR polyimide exhibited enhanced pure-gas CO2/CH4 selectivity of 46 with a moderate decrease in CO2 permeability to 215 Barrer. The CO2 permeability of TPDA-DAR was similar to 30-fold higher than that of a commercial cellulose triacetate membrane coupled with 39% higher pure-gas CO2/CH4 selectivity. The TPDA-based dihydroxyl-containing polyimide showed good plasticization resistance and maintained high mixed-gas selectivity of 38 when tested at a typical CO2 natural gas wellhead CO2 partial pressure of 10 atm. (C) 2016 Elsevier Ltd. All rights reserved.