Random and block copolymer membranes based on flexible etheric-aliphatic soft segments designed for CO2/CH4 separation

Air pollution gradually aggravated, which accelerates the demand of clean energy (in particular clean natural gas) because of its abundant storage worldwide. However, raw natural gas commonly contains impurity gases, such as CO 2 and N 2 , which reduce the heat of its combustion. Here, we reported new polyamide-poly(propylefne glycol) (PA-PPG) random and block copolymer materials with excellent CO 2 /CH 4 separation performance. These copolymers were characterised by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy ( 1 H NMR), UV–vis absorption spectrum and X-ray diffraction (XRD). The gas permeation properties of these copolymers were investigated by using five single gases (CO 2 , H 2 , O 2 , CH 4 and N 2 ) at different temperatures (298–328 K) and a feed pressure of 76 cmHg. The effects of chemical structure, PPG content and operating temperature on the gas permeation properties of these copolymers were also further discussed. Results showed that PA-PPG random copolymer membranes exhibited better gas permeation properties than those of PA-PPG block copolymer membranes. PA-PPG random copolymer membrane with 20 wt% PPG exhibited the highest selectivity (CO 2 /CH 4  = 37.31 and H 2 /CH 4  = 33.44) at 298 K and 76 cmHg. The CO 2 and H 2 permeability values were 5.97 Barrer and 5.19 Barrer, respectively.