| ABSTRACT:The greenhouse effect is one of the main environmental problems that humanity faces at present. As emphasis on the shortage of resources and global warming advanced, reduction of CO2emission and resource-regeneration have become to be one of the most important environmental and energy issues. Based on the results, we draw the following conclusions:Traditional absorption and collection methods for CO2show some defects, such as the high volatility of the chemical absorbent and high energy consumption of regeneration. As a new type of green solvents, ionic liquids get increasing attention. In this research, room temperature ionic liquids (RTILs) and membranes were used for preparation of supported ionic liquid membranes, to explore new methods for CO2absorption. We investigated the absorbability and desorbability performances of different supported ionic liquid membranes (SILMs) for pure CO2and CO2mixtures under different operation conditions.1. Four ionic liquids,[C4MIM][PF6],[C4MIM][BF4],[C8MIM][PF6],[C6MIM][Tf2N] were used. After immobilising [C8MIM][PF6] inside the pores of the the hydrophobic PVDF membrane, the membrane had poor mechanical strength and got easily broken. This shows that the increase in the carbon chain length of the RTIL cation has an impact on the structure of SILM.2. With the comparation of four RTILs aborbability for pure CO2, we found that except for the SILM with [C4MIM][BF4], their absobability performance were better than organic ammonium, which the biggest molar ratio of chemical adsorption is1:1. Anion had a more obvious affect on absoption performance than cation. The absorption strength order is [Tf2N]">[PF6]->[BF4]". The SILM with [C6MIM][Tf2N] exhibited best in absorption. According to the results of quantum chemical calculations, the higher gas solubility is due to a Lewis acid/base complexation that occurs between CO2and the SO group of [Tf2N]-. Among the ironic liquids with same anion, the solubility of CO2increased slightly along with the substituent carbon chain of cation increased, what’s more, the rate of increase was greater under a higher pressure.3. Compared with the pure CO2, the membranes immobilised with the ionic liquid [C4MIM][PF6] seem to be more stable in mixtures. With the increase in carbon chain, SILM with [C8MIM][PF6] can not absolutely absorb CO2from mixtures. SILM with [C6MIM][Tf2N] also performed worse, which means the presence of N2has a effect on absorption process.4. With the increase of the operation pressure (0.02-0.05MPa), the absobability for CO2significantly enhanced. Flow has a certain impact on the adsorption effect. CO2uptake increased slightly with the increased flow. However, the impact of flow to absobability is not obvious under low pressure.5. In this research, desorption could happen when the temperature and pressure were controlled at50℃-70℃,0.07MPa-0.09MPa respectively, and this process lasted only30minutes. Desorption rate could achieve100%in10minutes under the joint action of temperature and pressure. Compared with CO2desorption from organic amine, the method in this research can reduce the cost of CO2desorption for simpler operation and low energy consumption. |
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