The Synthesis Of New Piperazinium-Based Ionic Liquids And Their Application In Sulfur Dioxide Capture

The emission of sulfur dioxide ?SO₂? in flue gases from the burning of fossil fuels is a significant source of atmospheric pollution that threatens the environment and human health, where the capture of SO₂ has drawn worldwide attention. The conventional technologies to remove SO₂, such as limestone scrubbing, ammonia scrubbing and organic solvents absorption, have several inherent drawbacks, including byproducts and the volatilization of solvents. Recently, ionic liquids ?ILs? have developed as potential SO₂ absorbent for their unique properties, such as negligible vapor pressures, wide liquid temperature ranges, high thermal and chemical stabilities, non-flammability and tunable properties.In this thesis, we have designed, synthesized and characterized a new kind of piperazinium-based dual-functionalized ILs, including single anion-based ILs and double anions-based ILs. Experiments show that double anions-based ILs are solid at room temperature, due to the good symmetry of cations. So single anion-based ILs are selected for further investigations of their properties and applications in SO₂ capture. In addition, in order to study the effect of different anions and cations on the basicity of ILs, we also synthesized phosphonium-based ILs, and characterized the structures of ILs by using NMR and FT-IR methods.To illuminate the relationship among the structures of ILs, the basicity and the abilities to capture acid gases, we have measured and compared the basicity of piperazinium-based ILs and phosphonium-based ILs by ¹H NMR method with pyrrole probe. And we have explored the ability of these ILs to capture CO₂. Experiments show that the basicity of ILs and the ability to capture CO₂ are positively related. Compared with anions, the cations of ILs have smaller influence on the basicity of ILs.The performances of the piperazinium-based dual-functionalized ILs to SO₂ capture were studied. The [C2C1C14pi][Triz] designed this work could capture 2.28 mole SO₂/mole IL at 70?. The main reason for the large capacity was that both the cation and anion could capture SO₂ chemically, which has been verified by NMR and FT-IR. As a result, the piperazinium-based dual-functionalized ILs exhibit great potential in SO₂ capture.In summary, we measured the basicity of phosphonium-based ILs and piperazinium-based dual-functionalized ILs by'H NMR method with pyrrole probe, and illuminated the effect of different anions and cations on the basicity of ionic liquids. When using of piperazinium-based dual-functionalized ILs on SO₂ capture, we deeply discussed the SO₂ absorption performances by these ILs. It was demonstrated that the ILs were very efficient for SO₂ absorption in high temperature, due to both the cations and anions could capture SO₂ chemically. These works offer new methods and new strategies to capture SO₂ and CO₂ by ILs in high temperature.