Improved gas separation performance of Pebax®1657 membrane modified by poly-alcoholic compounds

Abstract

Poly (ether-block-amide) or Pebax is one of the most promising copolymers employed for CO2 separation. The existence of polyamide and polyether segments within the total matrix gives superior properties to Pebax, providing it significant CO2 permeation compared to the other light gases such as CH4 and N2. However, improving the separation performance of Pebax is one of the major concerns in developing new membranes. Compounds with hydroxyl and carboxyl groups are listed as appropriate candidates to be embedded within the Pebax matrix, finally enhancing the CO2 separation. Such compounds with oxygen atoms (negatively charged) can interact with the central carbon (positively charged) of CO2 via Lewis acid-base interactions, which contributes to further CO2 permeation. In this study, Pebax®1657, which has a good performance in CO2 separation, was blended with maltitol and mannitol as multi-hydroxyl compounds. Pebax/mannitol and Pebax/maltitol blend membranes were prepared by solution casting/solvent evaporation method, and their CO2 separation performance from N2 and CH4 was studied. Changes in chemical bonds, thermal properties, and cross-sectional morphology of the membranes were investigated using FTIR, DSC, TGA, FESEM and XRD analysis. The gas permeability results showed that the highest permeability of CO2 was 341.27 barrer and 228.64 barrer, which are related to Pebax/maltitol (20 wt%), and Pebax/mannitol (20 wt%) at a temperature of 30 °C and feed pressure of 10 bar, respectively. In addition, the highest selectivity of 66.65 (CO2/N2) and 23.95 (CO2/CH4) was obtained for Pebax/maltitol (20 wt%). Likewise, selectivity values of 67.84 for CO2/N2 and 25.49 for CO2/CH4 were obtained with Pebax/mannitol (20 wt%), at a pressure of 10 bar.