CO2 Separation over N2 and CH4 Light Gases in Sorbitol-Modified Poly(ether-block-amide) (Pebax 2533) Membrane

CO2 emissions have become one of the biggest industry challenges in recent years. Polymeric membranes have been studied as a promising alternative for CO2 separation in various gas streams. Poly(ether-block-amide) is a widely used polymer in CO2 separation, due to its CO2-philic nature. In this study, sorbitol as a poly alcoholic modifier was applied to improve the performance of the Pebax 2533 membrane for CO2 separation over N2 and CH4. The modified membranes were synthesized with 5 to 20 wt % of sorbitol. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and polarizing optical microscopy (POM) were applied to analyze the properties of the synthesized membranes. FTIR spectra confirmed the presence of all specific bands of Pebax 2533 and sorbitol in the modified membrane. Thermal analysis revealed an increase in the glass transition temperature as the sorbitol content within the membrane matrix was raised. The crystallinity of the membranes improved as the sorbitol content was increased up to 15 wt %. FESEM images of the pure membrane showed a uniform structure; however, an increased sorbitol load resulted in a more uneven structure appearing in the final product. Based on gas permeation tests, the CO2 permeability, CO2/N2 selectivity, and CO2/CH4 selectivity enhanced from 392.5 Barrer, 37.74, and 9.5 in pure membranes to 394.5 Barrer, 48.7, and 13.11, in the modified membrane containing 15 wt % of sorbitol, respectively, at a pressure of 10 bar.