Task-specific Deep Eutectic Solvents For The Absorption Of Sulfer Dioxide

Sulfur dioxide（SO₂）,from the combustion of fossil fuels is one of the air pollutants.The large amount of SO₂ emissions will result in environmental problems such as acid rain,which threatens people’s health,and affects economic and social development.The conventional flue gas desulfurization（FGD）methods are the limestone-gypsum method and the ammonia absorption method.However,these desulfurization processes cause a large amount of wastewater and a large number of low-grade by-products to be treated,and the absorbents usually can not regeneration.With SO₂ emission standards become more and more stricter,the alternative absorbents with efficient and reversible absorbents of SO₂ should be developed.In the past few decades,ionic liquids have received wide spread attention in SO₂ absorption due to their unique properties.However,because of their complicated preparation and purification processes,they are restricted in industrial applications.The deep eutectic solvents（DESs）,as a kind of liquid mixture that is bonded together by hydrogen bonding,have similar properties to ionic liquids.Therefore,as a new type of green solvent,it has received extensive attention in recent years.There are several kinds of DESs were development for SO₂ absorption.It is concluded that most conventional DESs absorption SO₂ through physical interaction.However,the absorptionsare not efficient due to the low concentration of SO₂.Therefore,it is important to design task-specfic DESs to achieve efficient and reversible absorption of SO₂.In this work,several kinds of task-specfic choline DESs were designed,synthesized and used for absorption of SO₂.The contents are as follows:（1）A series of task-specfic choline DESs were designed and synthesized.Their density（ρ）,viscosity（η）,etc.were measured,and correlated with the formula lnη=ln A+E_η/（RT）and lnρ=a+b T.（2）The synthesized task-specfic choline DESs were used for the absorption of SO₂,and the effects of partial pressure and temperature on the absorption of SO₂ by DESs were studied.FT-IR and NMR analysis proved that the absorption of SO₂ by such task-specfic choline DESs is mainly due to the chemical interaction between tertiary amine group and SO₂.（3）The SO₂ absorption by conventional DES Ch Br+Gly（1:3）and the task-specific DES PPZBr+Gly（1:3）were compared.The mechanism and thermodynamic process were analyzed.The Henry constant,quasi-chemical equilibrium constant,and chemical equilibrium constant are used to describe the absorption of SO₂,and the change ofΔG、ΔH andΔS of the corresponding processes are calculated.