| Environment and energy are two most important issues concerned in the world today. CO2 is not only the greenhouse gase causing greenhouse effect, but also is the important source of carbon, which can be transformed into energy. Separation and capture of CO2 from flue gas and other sources have been considered as an ideal way for greenhouse gas emission control and reutilization of CO2 as carbon resources. Membrane technology is simple and effective for CO2 separation. Among various membranes, facilitated transport membranes show fairly high selectivity as well as high permeability owing to the carrier reversible react with CO2 in the membrane. In facilitated transport membranes, the mobile carriers and fixed carriers possess their own advantage, as well as deficiencies. In this paper, a method has been proposed to combine their advantages and overcome their deficiencies by regulating the microenviroment in the membranes.Firstly, two polyether amine material, wich possess the mian chain with ether oxygen and the branches with amino, has been prepared to manufacture membranes. A microenviroment has been established in the membranes, in which the CO2 was entered in the area by dissolution diffusion effect of ether oxygen, and then, transported by the swing of amino in its location. The results showed that both polyether amine/PSf composite membrane showed good performance for CO2/N2 separation. The CO2 permeance of PEAM-pam/PSf composite membrane can reach 593 GPU and the CO2/N2 selectivity can reach 74 at 0.11 MPa, while the CO2 permeance of PEAM-tam/PSf composite membrane are 714 GPU and the CO2/N2 selectivity is 90 at 0.11 MPa.Secondly, because hydrotalcite is a channel with mobile carbonate ions, which is similar to a microenvironment and it can transport CO2 high efficiently. Thus, the hydrotalcite has been established in fixed carrier membrane and be used as a high-speed channel to transport CO2. At first, hydrotalcite channels has been established in a copolymer PEIE to fabricate PEIE-HT/PSf composite membrane. The CO2 permeance of PEIE-HT/PSf composite membrane can reach 5693 GPU and the CO2/N2 selectivity can reach 268 at 0.11 MPa, which are 6.7 times and 3.8 times of the CO2 permeance and the CO2/N2 selectivity of PEIE/PSf composite membrane, respectively. In addition, HT has been used to establish similar high-speed CO2 facilitated transport channels in polyvinylamine(PVAm)-- another fixed carrier membrane material, the CO2 permeance and CO2/N2 selectivity of PVAm-HT/PSf composite membrane can reach 3187 GPU and 296 at 0.11 MPa, which are 7.7 times and 4.3 times of those of PVAm/PSf composite membrane, respectively.Blending method is a simple and effective means that can combine the advantages of different polymer materials. Blending the fixed carrier membrane material with carbonate-ion exchange membrane material, it make a certain amount of mobile carrier cruise around the fixed carrier. On the one hand, the passivity of fixed carrier can be improved, then the fixed carrier do not need to passively wait for CO2 into its swing area, and the CO2 can be transported in the swing area of fixed carrier through mobile carrier. On the other hand, the fixed carrier material provides a flexible membrane matrix for mobile carrier material. Simultaneously, beceause of the interpenetrating of two kinds of polymer, the neat arrangement of two polymer can be disrupted and their chains spacing can be increased. Thus, some carbonate ions fettered by crystallization can be liberated. Meanwhile, the loose and flexible polymer chains provide a relaxed environment for the free movement of carbonate ions. The CO2 permeance of PVAm-PDDACA/PSf composite membrane, which containing fixed amine carriers and movable carbonate ions, can reach 909 GPU and the CO2/N2 selectivity can reach 102 at 0.11 MPa. The performance of PVAm-PDDACA/PSf composite membrane is higher than PVAm/PSf composite membrane and PDDACA/PSf composite membrane. |
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