Preparation Of Functionalized Ionic Liquids And Its Applications On Absorption Of Acid Gases

Air pollution from burning of fossil fuel has been the focus of the environmental problems.Especially, carbon dioxide (CO2) and sulfur dioxide(SO2) pollution are the most serious one, among which, CO2could results in green house effect, and SO2could result in acid rain, corrosion of equipments and architectures, diseases and so on. The traditional CO2-capture process and the SO2-absorption/desorption ways suffered from the problems of energy-intensive and the by-products difficult to deal with.So it is necessary to seek a new kind of absorbent with higher SO2-absorption capacity and better stability, and to be environmental benign.In this paper, five kinds of functionalized ionic liquids are synthesized, including three guanidinium ionic liquids,[1,1,3,3-tetramethylguanidinium][phenol]([TMG][PHE]),[1.1.3,3-tetramethylguanidinium][imidazole]([TMG][IM])and [1,1,3,3-tetramethylguanidinium][2,2,2-trifluoroethanol]([TMG][TE]),and two choline ionic liquids.The three guanidinium ionic liquids are synthesized by one-step synthesis whereas the two choline ionic liquids are by two-steps synthesis separately. The structures of the products are further characterized by Fourier Transfom infrared spectroscopy (FTIR) and nuclear magnetic resonance spectra(1H NMR,13C NMR).The properties of the five kinds of ionic liquids are measured. It is found that viscosity and density have similar temperature dependence, they all decrease with increasing temperature.Somehow, the temperature dependence of density is small owing to the negligible vapor pressure of ionic liquids. For ionic liquids with the same cation, the viscosity increases with the increasing anion volume.However, conductivity is found to increase with the temperature increasing.Guanidinium ionic liquids are applied to the capture of acid gases,and the SO2sorption and desorption behavior as well as the absorption mechanism at different temperatures was investigated. It was found that SO2has an optimistic solubility in guanidinium ionic liquids.Meanwhile, temperature is found to have a strong influence on the SO2absorption and desorption behaviors of the ionic liquids.Low temperature is found to favor high absorption capacity. The saturated molar ratio of SO2(MSO2/MIL) to GBILs varied from2.58to4.13at20℃with higher absorption rate compared to other reported ILs.The absorption mechanism might be that SO2reacts with the-NH2group on the [TMG]+cation and then a new-SO2-H group is formed. The new guanidinium ionic liquids could absorb SO2by both physical and chemical interactions while physical absorption does play an important role at the experimental conditions under investigation.