Synthesis Of Functional Ionic Liquids And Application In CO₂Absorption

Coal-dominated energy structure determines the rapid growth of CO2emission of China inevitability. Excess CO2emission, can cause greenhouse effect, which in turn lead to catastrophic global climate change,and these can seriously affect human living environment and ecological environment. The CO2itself is a safe, and non-toxic carbon-rich resources, can be used in soda ash, urea production,and it is an important industrial raw material.Therefore, CO2emission reduction and resource utilization has gradually become an important research direction.Currently, the chemical absorption method, as a relatively mature CO2capture method from flue gases of coal-fired, has been widely recognized in the industry. But there are some drawbacks of traditional chemical absorption, such as the corrosion of equipments, the produce of volatile contaminants etc. Therefore, in the field of CO2capture and seperation it is very nesessary to develop new materials for the selective absorption of CO2from flue gases.Ionic liquids (ILs) are new types of green solvents, having broad application prospects in carbon dioxide capture and separation technology. In this work, we synthesized and characterized two kinds of ether functionalized imidazolium cation based ionic liquids(ILs). Solubilities of CO2in1-methoxyethy1-3-methylimidazolium hexafluoroborate ([EOMmim][PFe]) and1-methoxyethyl-3-methylimidazolium bis(trifluoro-methylsulfony)imide ([EOMmim][Tf2N]) were determined at298.15K to343.15K and pressure ranged from1.052MPa to5.185MPa with a isovolumetric and gravimetric method. Solubilities of N2, O2and H2in these two ionic liquids were measured at303.15K. Compared with the solubility of CO2,we concluded that both of the ionic liquids have good selectivities for CO2absorption. The solubility of CO2in [EOMmim][PF6] is higher than that in [Emim][BF4] and [Emim][MDEGSO4] reported in literatures, but is lower than [Emim][Tf2N], while in [EOMmim][Tf2N], is slightly higher than [Emim][Tf2N]. The solubility data were well correlated by Pitzer model, moreover, Henry’s constant of CO2/IL system and the function relationship between Henry’s constant and temperature were abtained. The standard state solution Gibbs energy, standard state solution enthalpy and standard state solution entropy of CO2in [EOMmim][PF6] and [EOMmim][Tf2N] were derived and analyzed from molecular interactions. Thsee physical and chemical parameters provide a theoretical basis and foundation data support for the selection of ionic liquids with excellent properties for CO2absorption. The CO2absorption of both of the ionic liquids keep stable after repeated regenerations and recyles, reflecting the recyclability and stability of ionic liquids.In order to explore the absorption properties of ionic liquids which can absorb CO2effectively with lower partial pressure, we synthesized five kinds of amino-functionalized ionic liquids, and characterized them by1H NMR spectrum. We improved the apparatus for CO2absorption measurement by using a double-vessels absoption apparatus. The CO2absorption properties of amino-functionalized ionic liquid in different concentrations of aqueous solution were investigated at298.15K. This kind of ionic liquids for CO2absorption presented to be chemical processes and the reaction products were characterized by XH NMR,13C NMR and FTIR spectrum. We confirmed the structures and properties of some products preliminarily and speculated a simple mechanism of its absorption.