Thermally stable polymers for advanced high-performance gas separation membranes

Polymeric membranes can be used for the energy-efficient and low-cost gas separation. However, their inability to resist high temperatures limits their use in certain industries. Some polymer membranes can be operated at some levels of the unpleasant environments, but the energy- and cost-efficiencies are offset by the necessity to severely cool hot streams. In many cases, such implementation is impossible or altogether impractical. Therefore, numerous studies have been focused on modifying polymers to create synthetic polymeric membranes which survive at high temperatures. Polymer scientists introduced many thermally stable polymers mostly based on carbocyclic and heterocyclic aromatic polymers, which exhibit enhanced thermal stability. However, the major problem with these polymers is their low processability, which is mainly due to their insolubility or high phase transition temperatures. So far, there has been little success in processing the high-temperature-resistant polymers to make membranes with acceptable separation and performance characteristics. The aim of this study is to review efforts which have been made to produce high-performance polymeric membranes with a focus on the preparation procedure; whereby, the main limitations and challenges to be faced were explored. The key factors discussed include the type of polymer, membrane preparation method, thermal analysis results and application of the prepared membranes. The primary purpose of this review is to lay out the basics for selecting polymer, solvent, additives and the appropriate preparation method to produce thermally stable polymeric membranes for gas separation. The future direction of research and development to fully exploit the potential usage of thermally stable polymeric membranes to achieve commercially viable processes was also shown. (C) 2017 Elsevier Ltd. All rights reserved.