Design And Synthesis Of Ether Functionalized Ionic Liquids Immobilised On Siliga Gel And Their Desulfurization Performance

As the development of economy, air pollution becomes more and more seriously, and it is necessary to remove SO₂ from flue gas in coal combustion. Having no vapor pressure, good thermostability and chemical stability, ionic liquids may overcome the shortcoming of secondary pollution resulted in dealing with solid product in hydrated lime method for SO₂ removal from flue gas, and may realize resource of SO₂. Ionic liquids method will become a new potential desulfurization method.To solve the problems of little absorption quantity and strict regeneration conditions for the present ionic liquids for desulfurization, Ether-functionalized imidazolium-based ionic liquids（EFIILs） are proposed by researchers based on the structure designablity of ionic liquids. Oxygen in ether group may form adsorption forces with S in SO₂. The quantity of absorption can be increased by increasing the number of ether group in the ionic liquids. And the regeneration conditions are mild. Our research group has made some works on the synthesis of the ionic liquids and found that the dynamic viscosity is too high to apply it in commercial adsorption process. In this thesis, based on the optimal of synthetic route, EFIILs were suppoted on porous silica gell with impregnation method and chemical bonding method, respectively.EFIILs with 1-3 ether group on 1-N substituent group in imidazolium cation were synthesized with two step method. The physical properties of EFIILs, including density, viscosity and specific surface tension, were firstly investigated before and after desulfurization operatins. The changes of thermodynamic properties with the number of ether groups were analyzed. The action between the functional group in EFIILs and SO₂ were also discussed with quantum chemistry calculation.EFIILs were supported onto porous silica gel particles by impregnation method. EFIILs-SiO₂ were characterized by FT-IR, SEM, TGA and BET. Results show that EFIILs-SiO₂ have good thermal stability, and keep the high porosity and large specific surface area, which are suitable for SO₂ removal. EFIILs-SiO₂ have better adsorption properties than that of the pure EFIILs, due to the dual function of supporting materials-porous silica gel and EFIILs supported on it. EFIILs-SiO₂ system may be reused for five adsorption/desorption cycles without loss of its initial capacity.EFIILs were supported by chemical bonding method onto a silica gel, which is in situ prepared with tetraethoxysilane（TEOS） as silica source, with four steps, and supported materials [C3O1Mim-SG][H3CSO3], [C5O₂Mim-SG][H3CSO3] and [C7O3Mim-SG][H3CSO3] were prepared and characterized by FT-IR, MS, 1H NMR, 12 C MAS NMR, 29 Si MAS NMR, XPS, TEM, TGA and BET. The curves of nitrogen adsorption-desorption isotherms of [C3O1Mim-SG][H3CSO3] shows that its porous structure is mainly micropores, while [C5O₂Mim-SG][H3CSO3] and [C7O3Mim-SG][H3CSO3] exhibit type IV isotherms with H1 type hysteresis loops, which indicate that their pores are mainly mesoporous. The relation between cationic structure, temperature, SO₂ partial pressure and their absorbility of SO₂ were discussed.