A novel blend membrane modified Pebax-1657 with high-loading styrene-acrylonitrile copolymer for CO₂ separation

One of the critical industrial processes is the removal of CO₂ from flue gas to control greenhouse gas emissions, enrich natural gas, and recover landfill gas. In this study, dense polymer blend membranes composed of Pebax (polyether-block-amide) and SAN (styrene–acrylonitrile) were prepared across a wide concentration range (0–100 wt%), and the effect of SAN loading on the structural properties and gas separation performance of the membranes was investigated. The fabricated blend membranes were characterized using various techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The highest selectivity for CO 2 /N 2 (126.3) and CO 2 /CH 4 (33.2) was obtained for the blend membranes containing 20 wt% and 40 wt% SAN, respectively at a temperature of 25 °C and feed pressure of 8 bar. Moreover, the highest CH₄/N₂ selectivity (6.1) was observed for the 85/15 Pebax/SAN blend membrane under the same conditions. The results from the gas separation tests indicate that increasing the operating pressure and compactness within the polymer matrix in the presence of high molecular weight SAN significantly improves gas selectivity. In this regard, the 80/20 Pebax/SAN membrane, with a CO₂ permeability of 37.9 Barrer and CO 2 /N 2 selectivity of 126.3 at 8 bar, surpassed Robeson’s 2008 upper bound and approached the previous Robeson upper bound with a CO 2 /CH 4 selectivity of 26.9. • Modified Pebax 1657 was blended with high molecular weight SAN to improve CO 2 separation performance. • A CO₂ permeability of 37.9 Barrer and a CO₂/N₂ selectivity of 126.3 were obtained for the 80/20 Pebax/SAN membrane. • The selectivity of CO₂/N₂ and CO₂/CH₄ in Pebax-1657/SAN membranes increased with rising pressure. • The optimized Pebax/SAN membranes have surpassed the Robeson upper bound of 2008.