Preparation And Characterization Of Pebax Blend Membrane For CO₂ Separation

CO2 is regarded as the major greenhouse gas, and also an important carbon resource, so how to separate CO2 high efficiently has become a primary issue in the field of environmental protection and energy. Compared with traditional separation methods, e.g. absorption, adsorption and cryogenic distillation, membrane separation has its unique advantages, e.g. environmental friendly, low capital and operational cost, small footprint and easy to be coupled with other processes. Among kinds of membranes, blend membrane can combine the advantages of different materials, and result in better overall performance. Aprotic heterocyclic anions (AHAs) can react with CO2 reversibly, and recent research about ionic liquid and salt solution based on these anions demonstrated that AHAs can improve their CO2 absorption performance.In this research, solvent-evaporation method was used to prepare blend membranes with different composition. Poly(ether-b-amide) (Pebax 2533) was chosen as polymer matrix, the polyethylene glycol 200 (PEG 200) solution of sodium 1,2,4-triazole (TrizNa) and TrizNa were chosen as blend additives. SEM, FTIR, TGA, DSC were used to characterize the blend membranes. The results showed that the additives were successfully incorporated into the polymer matrix, and the addition of all additives had certain effects on the structure and thermal properties of the blend membranes.Compared with the pristine Pebax 2533 membrane, after the incorporation of additives, the mechanical properties of the blend membranes were affected, both tensile strength and elongation at break decreased. This is because during the formation of the blend membranes, the liquid additives and solid polymer matrix might generate phase separation, and the solid additives might aggregate in the polymer matrix due to the poor incompatibility. But when the additive loadings were not very high, the mechanical properties of the blend membranes were still on a relatively high level.In order to make sure the appropriate loading of PEG 200/TrizNa in Pebax 2533, the CO2 separation performance of Pebax 2533/PEG 200 blend membranes were studied first. When PEG 200 loading is 20 wt.%, the blend membrane exhibits best performance with CO2 permeability of 191.83 Barrer, and the CO2/N2, CO2/CH4 and CO2/H2 selectivities of 26.47, 7.92 and 4.65, respectively.The CO2 separation performance of Pebax 2533/PEG 200/TrizNa blend membranes were further studied. When TrizNa concentration of the PEG 200/TrizNa soluiton is 15 wt.%, the blend membrane exhibits best performance with CO2 permeability of 219.55 Barrer, and the CO2/N2, CO2/CH4 and CO2/H2 selectivities of 32.33,10.12 and 6.52, respectively. Improving operating pressure can increase CO2 permeability and selectivities. Improving operating temperature can increase gas permeabilities, and CO2 selectivities decrease a lot.The CO2 separation performance of Pebax 2533/TrizNa mixed matrix membranes were further studied. When TrizNa loading is 15 wt.%, the mixed matrix membrane exhibits best performance with CO2 permeability of 219.01 Barrer, and the CO2/N2, CO2/CH4 and CO2/H2 selectivities of 27.40,8.10 and 4.80, respectively. Improving operating pressure can increase CO2 permeability and selectivities. Improving operating temperature can increase gas permeabilities, and CO2 selectivities decrease a lot.