Studies On The Synthesis And The Properties Of Diethylenetriamine-derived Ionic Liquids

As novel solvents and functional materials, ionic liquids are expected to replace the conventional aqueous solution of amines for the industrial capture of carbon dioxide. Recent studies demonstrated that ionic liquids as good "absorption solvents" have a potential application in carbon dioxide capture and conversion. Aiming at functionalized ionic liquids for capturing carbon dioxide, diethylenetriamine (DETA)-based ionic liquids,[DETA][X](X=Cl, Ac, BF4), were synthesized. IR and NMR were used to characterize the ionic liquids, determined the relevant physical properties and the capacity of carbon dioxide absorption under ambient pressure.With diethylenetriamine (DETA) as cationic donor,[DETA][C1] ionic liquid with symmetrical structure was synthesized by equal mole of DETA and HCl, then [DETA][CH3COO] and [DETA][BF4] ionic liquid were synthesized through ion exchange. NMR and IR were used to confirm their structure. The experiment showed that,[DETA][C1] and [DETA][CH3COO] have good solubility in water, ethanol and ethylene glycol, but the solubility in diethyl ether, acetonitrile, methylene chloride, chloroform and acetone is poor;[DETA][BF4] has good solubility in water, ethanol, ethylene glycol, acetonitrile, acetone, but solubility in diethyl ether, methylene chloride and chloroform is poor.Density, viscosity and conductivity of the three kind of amino-containing functional ionic liquids and EG mixture were determined under the20-50℃temperature range. Compared the influence of different anions on density, viscosity and conductivity of the mixture. Experimental results show that, when the temperature decreases and concentration of ionic liquid increases, the density of the mixture increases, and the influence of different anions on the density are:BF4-> CH3COO> Cl; when the temperature decreases and concentration of ionic liquid increases, the viscosity of the mixture increases, and the influence of different anions on the viscosity are:CH3COO->BF4->Cr; when the temperature increases and concentration of ionic liquid decreases, the conductivity of the mixture increases, and the influence of different anions on the conductivity are:Cl>BF4->CH3COO-. The absorption capability CO2in ionic liquids were measured at ambient pressure, found that the DETA-derived ionic liquids have high absorption capability of CO2; the mechanism was chemical absorption; the mixture of DETA-derived ILs and EG mixture could be recycled, and there is no obvious change after three absorption and desorption cycles.