A Study On Absorption Of SO₂ In Simulated Flue Gas By Carboxylate-Based Task-Specific Ionic Liquids

Sulfur dioxide ?SO₂? is a kind of atmospheric pollutants. It can not only threaten the health of people, but also have a strong damage on soil and buildings. Recently, nationwide acid rain and haze weather are also closely related to the emission of SO₂. Meanwhile, SO₂ is a kind of important chemical materials. Therefore, there is a great significance for our survival and development to capture and reuse of SO₂ from these industrial process. It has been found that ionic liquid ?ILs? especially task-specific ionic liquids ?TSILs? can effectively absorb SO₂ in flue gas due to their unique qualities. TSILs can absorb SO₂ mainly based on chemical interaction, but the absorption mechanism is still unclear. The addition of solvent can decrease the high viscosity of ILs and improve transmission, but whether the added solvents have an effect on absorption capacity is unknown. Our aim is to realize the industrial application of the mixed absorber in the field of flue gas desulfurization. How about the stability of the absorbent after a long time of absorption and desorption in the continuous device? As the high pKa of carboxylic acids, almost all of ILs with the anion of carboxylate can be called TSILs for SO₂ capture. The synthesis of the carboxylate-based TSILs is simple and they have a high ability of absorption and desorption. So in this work, we synthesized several carboxylate-based TSILs to absorb SO₂ with low concentrations in simulated flue gas. A lot of work had been done to solve the above problems. The main results of this work are shown as follows.1. Several kinds of TSILs based on carboxylate anion were synthesized in this work and used to capture SO₂ from simulated flue gas. Furthermore, the absorption mechanism of SO₂ by the TSILs was proposed based on FT-IR,1H NMR and 13C NMR analyses. The results show that all of the carboxylate anion-based TSILs can absorb low-concentration SO₂ with high efficiency. It has been found that there are chemical interactions between the -COO- of carboxylate anion of TSILs and SO₂. Besides, when the carboxylate anion has a hydroxyl group, the -OH will not only improve the capture of SO₂ but also improve the desorption efficiency of SO₂.2. The effect of various solvents on the absorption of SO₂ by TSILs has been studied. The presence of ethyl glycol ?EG? has a great influence on absorption by guanidinium- and alkanolaminium-based TSILs, but not for quaternary ammonium-based TSILs. Then, the interaction between EG and TSILs was studied by FT-IR and the effect of EG on absorption mechanism was investigated. It was demonstrated that the addition of EG can improve the basicity of guanidinium-based ILs due to the solvation effect of EG and then improve SO₂ absorption capacity.3. The absorption and desorption of SO₂ by TSILs in the continuous device had been simulated to investigate their stability under the long time of recycling.1H NMR spectra results show the [MEA]L aqueous solution and [TMG]L aqueous solution are stable after many cycles of absorption and desorption of SO₂. But when iron inlet tube was used to charge the simulated flue gas, [TMG]L aqueous solution is unstable, and a small amount of sulfur was found.