Gas permeation and separation properties of sulfonated polyimide membranes

• Published in: Polymer (Guilford) 2006-05, Vol.47 (12), p.4370-4377
• Main Authors: Tanaka, Kazuhiro, Islam, Md. Nurul, Kido, Masayoshi, Kita, Hidetoshi, Okamoto, Ken-ichi
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; Humidity; Polymer industry, paints, wood; Separation of carbon dioxide; Sulfonated polyimides; Technology of polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2006.04.001

Permeability and selectivity of pure gas H 2, CO 2, O 2, N 2 and CH 4 as well as a mixture of CO 2/N 2 for sulfonated homopolyimides prepared from 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoro propane disulfonic acid (BAPHFDS) were measured and compared to those of the non-sulfonated homopolyimide having the same polymer backbone. The polyimide in a proton form (NTDA–BAPHFDS(H)) displayed higher selectivity of H 2 over CH 4 without loss of H 2 permeability. Strong intermolecular interaction induced by sulfonic acid groups decreased diffusivity of the larger molecules. The CO 2/N 2 (19/81) mixed gas permeation was investigated as a function of humidity. With increasing relative humidity from 0% RH to 90% RH, the CO 2 permeability for NTDA–BAPHFDS(H) polyimide increased by more than one order of magnitude, and the selectivity of CO 2/N 2 also increased twice or more. On the other hand, the gas permeability for the non-sulfonated polyimide slightly decreased with increasing humidity. NTDA–BAPHFDS(H) polyimide displayed a CO 2 permeability of 290×10 −10 cm 3 (STP) cm/(cm 2 s cmHg) and a separation factor of CO 2/N 2 of 51 at 96% RH, 50 °C and total pressure of 1 atm.