The effect of structure change from polymeric membrane to gel membrane on CO2 separation performance

Abstract Poly(ether-block-amide) (Pebax)/tricaproin (TCP) gel membranes were prepared for the first time with TCP content varying from 0 to 80 wt%. And the effect of structure change from Pebax polymeric membrane to Pebax/TCP gel membrane on CO2 separation was studied. Membrane morphology and crystallinity was characterized by scanning electron microscope (SEM) and wide-angle X-ray diffractometer (WAXRD). Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC) were used to characterize the interaction and compatibility between Pebax and TCP. Thermal stability of the prepared membranes was conducted by thermal gravimetric analysis (TGA). With the increase of TCP content, the physical properties of Pebax/TCP gel membrane were approaching to liquid TCP. However, in comparison with liquid TCP, the weight loss temperature of TCP in Pebax/TCP gel membranes improved by almost 100 °C. Gas permeation test confirmed the monotonically increasing CO2 permeability with slight increase of CO2/H2 selectivity, and slight loss of CO2/N2 and CO2/CH4 selectivity from Pebax membrane to gel membrane with 80 wt% TCP. In addition, ascribing to the weakened diffusion control effect and higher solubility control effect, Pebax/TCP membranes showed a higher CH4 permeability than H2 permeability when the TCP content exceeded 40 wt%. Moreover, compared with Pebax membrane, Pebax/TCP gel membrane showed higher sensitivity to operating pressure. Under the testing condition of 35 °C and 6 KPa, Pebax/TCP 80 gel membrane showed CO2 permeability of 1673.2 Barrer with CO2/N2, CO2/CH4 and CO2/H2 selectivity of 15.3, 4.8 and 6.4, respectively.