Synthesis Of Functionalized Ionic Liquid And Absorption For SO₂

Sulfur dioxide as one of the major air pollution gases has attracted people's attention. Ionic liquids are a new type of green solvents, efficient reaction media and catalyst with a negligible vapor pressure, good conductivity, high thermal stability, chemical stability, wide electrochemical window, such as the unique nature of the soluble or absorb a variety of gases including sulfur dioxide. Ionic liquids show a good prospect in the reduction and elimination of pollution generated in the chemical process. At present, the study for the function of SO₂ absorption by ionic liquids is one of hot points about Green Chemistry and Chemical Engineering.TSILs'synthesis, characterization and absorption of SO₂ gas is the focus. First, TSILs-[NH₂e-mim]Br and [NH₂-G]Br are syntheticed by microwave reaction, another TSILs-[NH₂e-mim]PF₆ and [NH₂-G]BF₄ are syntheticed by heating reflux. The optimum synthetic conditions are determined by the experiments. The optimum conditions of [NH₂e-mim]Br are anhydrous ethanol as reaction solvent, the reaction time 75⁸0s, reaction temperature 45℃.The optimum conditions of [NH₂-G]Br are anhydrous ethanol as reaction solvent, reaction temperature 50℃, reaction time 120s. The four kinds of ionic liquids'yield are all more than 85%. These ionic liquids are characterized by infrared spectroscopy and nuclear magnetic resonance spectra.Secondly, the basic physical properties of the four ionic liquids, including solubilities, densities, viscosities and conductivities are measured. Test results show that the four kinds of ionic liquids can be immiscible with most organic solvents. All the densities of ionic liquids are between 1.1 g/cm3 and 1.6g/cm3, because they have no vapor pressure, temperature changes has little effect on the density. Test result shows that the viscosities decrease with increasing temperature. The viscosities of ionic liquids which have the same kind of cation increase with the increasing anion size. The result shows electrical conductivities increase with increasing temperature. Electrical conductivities of ionic liquids which have the same kind of cation decrease with the larger anion size.Finally, [NH₂e-mim]BF₄, [NH₂e-mim]Br, [NH₂e-mim]PF₆, [NH₂-G]Br, [NH₂-G]BF₄ mixed with water in different proportions are used in the absorption for pure SO₂ gas at 30℃, 40℃, 50℃and 60℃. The results show when [NH₂e-mim]Br mixs with water at the ratio of 4:1, has the maximum rate of SO₂ absorption under temperature 60℃in three kinds of imidazolium-based ionic liquids.When [NH₂-G]BF₄ with water at ratio of 4:1, has the highest rate of SO₂ absorption under temperature 30℃in two kinds of guanidine salts-based ionic liquids.