Study On The Absorption Of Sulfur Dioxide By Functionalized Ionic Liquids

The combustion and energy conversion processof fossil fuel will produce a lot of greenhouse gases and harmful gases.Sulfur dioxide(SO2)mainly comes from coal and oil refining exhausts.The discharge of SO2 gas can cause serious pollution.The traditional desulfurization methodsfor flue and refinery gases mainly include limestone/gypsum and ammonia absorption.However,there are many disadvantages such as the difficulty of reusing the absorbent and the volatile nature of the absorbent.People have been trying to study and use new absorbent to solve the above problems.Because of good physical and chemical properties,ionic liquids are receiving increasing attention in the field of SO2 absorption.Therefore,we systematically studies the absorption of SO2 in the flue gas by functionalized ionic liquids in this paper.The simulated refinery gas containing SO2 was first studied by using a series of ethanolamine-based ionic liquids.The effect of N,N-dimethylethanolamine formate ionic liquid on the SO2 absorption shows the best results:at 25 ℃ and 0.1 MPa,for the simulated flue gas(SO2 concentration～1200 ppm),1 g ionic liquid can absorb the SO2 of the flue gas to less than 100 ppm,and this situation can maintain to more than 300 min.Particularly,the SO2 absorption capacity of the ionic liquid is 0.82 mol SO2/mol IL.In addition,the SO2 absorption process of imidazole-based ionic liquids was also studied.Results show that 1-butyl-3-methylimidazole acetate ionic liquid([BMIM]OAc)has a better SO2 absorption capacity.[BMIM]OAc can continuously reduce the 1200 ppm SO2 of flue gas to 100 ppm SO2 within 455 min,and 0.72 mol of SO2 can be absorbed per mole of ionic liquid.In order to further improve the S02 absorption capacity of the ionic liquids,the paper focuses on the SO2 absorption by mixing different ionic liquids.The results show that the mixed ionic liquid has a significant effect on the SO2 absorption.N,N-dimethylethanolamine formate and 1-butyl-3-methylimidazole([BMIM]OH)can continuously absorbed the SO2 content in the exhaust gas less than 100 ppm within 344 min.In addition,the orthogonal experiment for SO2 absorption was carried out to obtain the better absorption conditions of the mixed ionic liquid.When N,N-dimethylethanolamine formate was used and the mass ratio of N,N-dimethylethanolamine formate to[BMIM]OAc was 1:1,the mixed ionic liquid can continuously absorb the flue gas from with 1200 ppm SO2 to with 100 ppm SO2 555 min.Orthogonal experiments show that the type of imidazole ionic liquid has a greater effect on the absorption of SO2 by mixed ionic liquids.In order to study the changes of SO2-ionic liquid absorption process,the quantum chemical calculation was also carried out.Furthermore,we investigated the mechanism of ionic liquid absorption of SO2,ionic liquid and SO2 bonding reactions.In this paper,the absorption of SO2 by ionic liquids was studied.Results show that the mixing of ionic liquids is more conducive to the absorption of SO2 in flue gas and refinery tail gas than that of single ionic liquids.This method is simple and easy to synthesize ionic liquid,which provides a new idea for the absorption of SO2,and has a wide application prospect.