Fundamental Research On Functional Ionic Liquids To Fix CO₂

The dramatical increasing content of CO2 in the atmosphere is because of serious energy consumption by the industrialization especially the steel industry. About 20%CO2 is contented in blast furnace gas which is largely produced in the blast furnace production process, and has the disadvantages of less combustible ingredients and low calorific value. So CO2 capture from blast furnace gas is important both to the economy and to the environment as well.As a kind of new ionic solvents, ionic liquids(ILs)have different internal configuration compared with that of traditional molecular solvents. A systematic study of the interaction in the ILs might lead to a better understanding of their structure-activity relationship for collecting of CO2.6 kinds of ionic liquids(DETA-HCOOH, TETA-HCOOH, TEPA-HCOOH,DETA-HL, TETA-HL and TEPA-HL) were synthesized thought the acid-base neutralization reactions. The structures of the ionic liquids were characterized by IR Spectroscopies and H nuclear magnetic resonance(1HNMR), and their properties in dissolvability and thermal decomposition were investigated. The experiments to measure the ionic liquids fixing CO2 were conducted from which the preliminary conclusion can be drawn that all the ionic liquids synthesized in this work have the capability to fix CO2. Moreover, the structures of ionic liquids while fixing CO2 were characterized by 1HNMR. The results show that the-NH2 of the ionic liquids react with CO2 and the structural styles of the products are weak bonds approximating that of carboxyl.Calculation of Quantum chemistry can get rid of the blindness for screening of ionic liquids by experiment. In order to obtain the optimal configurations, frequencies and thermodynamics data, and hence to analyze stable configurations of synthesized ionic liquids from microscopic view, the density functional theory(DFT) at the B3LYP/6-31G(d) level were involved to optimize the structures combining with dispersion method at B2 PLYPD to eliminate the interference, in which the Gaussian calculation program was adopted in the calculations. The results showed that the multiple hydrogen bonds together with the electrostatic interaction play an important role in stabilizing the cation-anion system. The calculations also demonstrate that the reactions to fix CO2 are exothermic which is consistent with the experimental phenomena found in this work.The interactions between above 6 ionic liquids and CO2 molecular were calculated. By calculation to configurations of DETA-HCOOH and DETA-HL fixing CO2 at different positions of amide, the stable configurations and relative thermodynamic data were obtained. However, comparing the combination ways of the ionic liquids and CO2 and the thermodynamic calculations, it is found that the terminal amidogens can fix CO2 preferentially, and the structural styles of the products belong to weak bonds approximating to that of carboxyl which is consistentwith that characterized and analyzed by1 HNMR. Furthermore, taking the series of HCOOH and the HL as the objects, the thermodynamics functions were calculated and compared in the condition of ionic liquids with same positions but different number of amidogen. The results show that the smaller number of amidogen is in the ionic liquid, the better results of CO2 fixation can be reached, so that the CO2 fixations of DETA-HCOOH and DETA-HL that both contain with smaller amidogens can conduct easier than others.