| In recent years, room temperature ionic liquid (RTIL) has been paid more and more attention by gas separation membrane researchers for its diversity structure and strong controllability of physical and chemical properties. RTIL is an organic salt which is composed of organic cation and organic or inorganic anion. It was known as room temperature ionic liquid since its melting point is usually lower than 25?. The research results showed that RTIL could have strong capacity of CO2 sorption and high CO2/N2 selective sorption by designing the proper structure of cation and anion. Membranes prepared by the designed RTIL showed excellent performances in CO2/N2 separation.Ionic liquids in SILM could easily be extruded from supporting layer by high pressure gas. As a result, the stability of SILM decreased and eventually lost the separation ability. To increase its mechanical property, researchers transferred liquid RTIL into poly(RTIL). However, gas permeability of poly(RTIL) was much less than that of liquid RTIL because of the increase in material density and the significant decrease in free volume after polymerization. To address this problem, researchers blended liquid RTIL into poly(RTIL). The blended membrane had excellent mechanical stability because the blended liquid RTIL maintained physical properties. Therefore, the CO2/N2 selectivity and CO2 permeability of poly(RTIL) have been strongly enhanced.For measuring the gas separation performance, we have designed and constructed an equipment by using a dual-volume pressure decay method which could accurately measure the gas (He?H2?N2?O2?CH4? CO2?C2H4?C2H6?C3H6?C3H8 etc.) solubility in various materials such as organic, inorganic and nonvolatile liquid.The application temperature of the device was from ambient temperature to 50?, and applicable pressure range from 0 to 1000 psi (0-66atm). Computer data acquisition system was used in the device with high accuracy (±5%). At the process of volume calibration, Virial mode was used to accumulate the gas activity. Accurate volume of each chamber was accumulated by measuring ratios of two volumes and changing volume of the sample chamber. Gas sorption in polymers was measured via the dual-volume pressure decay method. The sorption isotherm of gases was obtained by measuring the equilibrium pressure of each chamber.Besides, we have designed and constructed an equipment which could accurately measure the pure and mixed gas permeability of polymeric membranes. The operation temperature of the device was from ambient temperature to 50?, and the applicable pressure ranged from 0 to 20 atm. Computer data acquisition system was applied in the device to improve the detecting accuracy. During the process of volume calibration, we first calibrated the volume of down-stream gasholder by the gravimetric method. Then, the volume of down-stream tubing system was precisely determined by measuring volume ratio of the down-stream gasholder and the whole downstream system including tubing system plus gasholder before and after the gas expansion. To evaluate the accuracy of the equipment, we measured the permeability and selectivity of PDMS to pure N2, O2, CO2 and mixed gas comprising 15/85mol% CO2/N2 in different pressures at 35?. The experiment result agreed well with the literature reported data; hence the equipment had high accuracy and reliability.In order to prepare the poly(RTIL) membrane which has excellent CO2 sorption capacity and CO2/N2 separation performance, we have synthesized PVI through free radical reaction, and introduced amino functional groups to imidazole ring by grafting reaction with 3-bromopropylamine hydrobromide subsequently. Finally, the poly(RTIL) was obtained by ion exchange reaction. The product structure was characterized by FT-IR and 1H-NMR. TGA and GPC were used to measure the polymer thermal property and molecular weight. Symmetric dense poly(RTIL) membrane was prepared by solution casting method. Using gas separation measurement equipment constructed in the study, we have measured the CO2/N2 separation performance of poly(RTIL) membrane. According to experimental results, poly(RTIL) membrane with amino functional groups has been successfully prepared in this study. The final product was rubbery polymer at ambient temperature and showed good thermodynamic stability, had higher molecular weight which was conductive to membrane formation. For improving the reaction efficiency of-NH2 and CO2, poly(RTIL) membrane was coated with 50%-50% PEG-H2O mixed solution. Compared with dry membrane, the N2 and CO2 permeability of poly(RTIL) membrane was increased 2.4 and 6 times to 7.8barrers and 62 barrers, meanwhile, the CO2/N2 slectivity was increased to 8. |
PDF Full Text Request