Study On Desulfurization Performance Of Acid Iron Based Ionic Liquids

Traditional organic solvent desulfurization has high energy consumption and many side reactions.Ionic liquid,as a green solvent with low vapor pressure,can be used as a desulfurizer with good performance.In this paper,the conventional ionic liquids,functional ionic liquids and iron based ionic liquids used to absorb hydrogen sulfide(H₂S)are summarized.And the structure of ionic liquid which can improve the desulfurization performance is discussed from two aspects of improving the ability of dissolving H2S and reducing the viscosity.Finally,FeCl₃ and[bmim]Cl(x=0.6,0.8,1.0,1.2 and 1.4)with different molar ratios were selected as desulfurizer in this paper.xFeCl₃/[bmim]Cl has been synthesized and characterized by anhydrate FeCl₃ and[bmim]Cl.The characterization results show that the ionic liquid has both Lewis acid and Bronsted acid,and has good thermal stability.The solubility data of H₂S in x FeCl₃/[bmim]Cl at different temperatures have been determined.Henry's coefficient and the reaction equilibrium constant were calculated by nonlinear fitting of the solubility data using the reaction thermodynamic equilibrium equation,taking pressure as the independent variable and solubility as the dependent variable.The change of these two thermodynamic variables with temperature and pressure is analyzed.It is found that both Henry coefficient and chemical equilibrium constant decrease with the decrease of temperature and the increase of pressure.The chemical solubility is influenced by both Henry's coefficient and the chemical equilibrium constant.When the temperature is333.15 K and x=0.6,the chemical solubility has a maximum.The interaction energies between the solvent molecules and H₂S molecules were calculated by using Gaussian software.DMI,DMAC and DMF were selected as solvents to be mixed with ionic liquid.The desulfurization performance of the mixed desulfurization liquid was enhanced.The desulfurization process of x FeCl₃/[Bmim]Cl was optimized by single factor experiment,and the desulfurization performance of0.6FeCl₃/[Bmim]Cl was the best.The desulfurization performance of the three solvents mixed with 0.6FeCl₃/[Bmim]Cl was better than that of DMI.The desulfurization performance is enhanced with the increase of temperature,but the increase of gas velocity is not conducive to the absorption of H₂S.