The Synthesis Of New Functionalized Ionic Liquids And Their Application In The Capture Of Sulfur Dioxide

Sulfur dioxide (SO2) which comes from the burning of fossil fuels, has drawn much more attention because it is the main atmospheric pollution that threatens environment and human health. Several processes (limestone scrubbing, ammonia scrubbing and organic solvents absorption) have been developed to remove SO2, which have several inherent drawbacks:for example, lots of byproducts CaSO4and waste water. Recently, ionic liquids (ILs) have attracted considerable attention because of their unique properties, including negligible vapor pressures, wide liquid temperature ranges, high thermal stabilities and tunable properties. They have been widely used in the field of SO2capture. Generally, SO2absorption by these ILs is mainly based on the single-site interaction between ILs and SO2. Therefore, it is very important to increase the number of interaction sites between ILs and SO2in order to achieve highly efficient SO2absorption. Herein, several novel strategys for the capture of SO2by several new functionalized ILs were reported, which exhibited high capacity and excellent reversibility.Furthermore, the absorption mechanism was investigated byspectroscopic investigation and quantum mechanical calculation.The following is the main results obtained in this work:In this thesis, we have reported a new strategy for SO2absorption by tunable azole-based ILs with multiple sites of action. Extremely high capacity of SO2and excellent reversibility were achieved by tuning the interaction between the electronegative nitrogen atoms in the anion and acidic SO2. Spectroscopic investigation and quantum mechanical calculation results show that such high SO2capacity is originated from the multiple interaction sites between the anion and SO2.Continuing to our previous work, a new method for SO2capture by dual functionalized ILs to enhance the absorption capacity through introducing a combination of ether-functionalized cation and tetrazolate anion was presented. The results exhibit an extremely high capacity of SO2(-5.0mol/mol) and excellent reversibility through a combination of chemical and physical absorption.In further research on the SO2capture by azole-based ILs, a series of novel benzo-functionalized azole-based ILs to reach higher SO2capacity were developed. The results show these ILs can absorb about1.5mole SO2per mole IL under40℃and500ppm of SO2in gas mixture. The results also reveal the process of SO2absorption by these benzo-functionalized azole-based ILs is highly reversible. Here, the π···S interaction enhanced by the anion is the main reason for higher absorption capacity for benzene-containing IL than azole-based IL.Finally, another strategy was developed in this thesis for SO2capture by anion-functionalized ILs to increase the available capacity and decrease the high absorption enthalpy through introducing a withdrawing interaction site:X (F, Cl, Br) and C=N. Spectroscopic investigations and quantum-mechanical calculations show that such a different behavior originates from the dual role of these withdrawing interaction sites.Above all, several kinds of new functionalized ionic liquids were designed, prepared, and used for SO2capture, which exhibit an extremely high capacity of SO2and excellent reversibility. Absorption mechanism was investigated through spectroscopic investigation and quantum mechanical calculation. These novel strategys open a door to achieve high capacity as well as excellent reversibility to capture SO2, H2S, and CO2by ILs.