Ionic Liquids Chelated Iron Solution Capture Hydrogen Sulfide And Its Electrolytic Regeneration Process

Hydrogen sulfide（H₂S）is a toxic gas that corrodes equipment and deactivates catalysts,posing a threat to the environment and human health.Ionic liquids are used to capture H₂S due to their good properties.Conventional ionic liquids or mono-functional ionic liquids currently used have fewer binding sites with acidic gases and lower sulfur capacity.The ionic liquids after saturated absorption of H₂S need to be regenerated to recover the absorption capacity.The electrochemical oxidation method realizes the regeneration of desulfurizer directly through external power supply and can effectively utilize H₂S.The desulfurizer is an ionic liquids aqueous solution,which is slow in electrochemical regeneration,and the products are mostly polysulfide.Therefore,a dual-functional ionic liquids was designed for chelating desulfurization and electrochemical regeneration process.Expand the following studies:Tetramethylenediamine acetic acid（[TEMEDH][Ac]）and tetramethylenediamine acetic acid（[TMPDAH][Ac]）were synthesized by a one-step method.The desulfurization properties of 30 wt%ionic liquids aqueous solution and 30wt%ionic liquids chelated iron mixed solution were tested at 20℃.The results show that the addition of iron chelate does not destroy the structure of proton-type ionic liquids,but enhances the absorption capacity of H₂S.The maximum sulfur capacity of[TEMEDH][Ac]chelated ferric solution and[TMPDAH][Ac]chelated ferric solution to H₂S is 0.552 and 0.426 mol/mol,respectively,which is better than that of organic alcohol amine and conventional ionic liquids desulfurization.The influence of different cations on the saturation absorption of H₂S was analyzed,and the applicable concentration of iron chelate was less than 0.04 mol/L.The sulfur capacity of the two ionic liquids ferric chelate mixed solutions decreased with the increase of temperature,and the saturated absorption decreased to 0.4097 and 0.3227mol/mol,respectively,when the absorption temperature was 50℃.When the concentration of ionic liquids is less than 30wt%,the maximum absorption of H₂S is independent of the concentration of proton-type ionic liquids,and when the concentration exceeds 30 wt%,the maximum absorption of H₂S is negatively correlated with the concentration of proton-type ionic liquids mixed solution.The potential constant anodic oxidation method was used as the regeneration method to compare the regeneration efficiency of ionic liquids chelated iron desulfurization rich solution and ionic liquids aqueous solution.The results showed that the regeneration effect of ionic liquids chelated iron mixed solution was superior to ionic liquids aqueous solution.The regeneration rate of desulfurized rich solution increases with the increase of anode potential.The results show that the regeneration potential of 1.0 V can prevent the excessive oxidation of HS^-.With the increase of temperature,the regeneration rate of desulfurization rich liquids will also increase.The regeneration temperature of 40℃can prevent the volatilization of H₂S from the system and avoid the destruction of cationic film structure.Regeneration The increase of p H value is conducive to solution regeneration.When the regeneration p H value was 7,the regeneration rates of[TEMEDH][Ac]Fe（III）mixed solution and[TMPDAH][Ac]Fe（III）mixed solution were 98.01%and 98.51%,respectively.When the p H value of the solution is too high,it will cause the sulfur or polysulfide to change into sulfur oxide ions S₂O₃^2-.The regeneration p H value was selected as 7.When the electrode is graphite,the regeneration rate of desulfurization rich liquids is the highest.The regeneration efficiency of the desulfurized rich liquids is more than 90%after three cycles,and the regeneration performance is good.The current peak increases with the increase of scanning speed,and the potential change speed is faster than the oxidation reaction rate,so that the potential shift of the current peak becomes larger,and the oxidation reaction of H₂S at low potential is more irreversible.Cyclic voltammetry test was conducted on three different solutions,and determine that the mechanism of regeneration of the hybrid solution is:2H₂S+2e→2HS^-+H₂,2HS^--2e→H₂+2S,Fe²⁺-e→Fe³⁺,2Fe³⁺+HS^-→2Fe²⁺+S+H⁺.The structure of the regenerated mixed solution remained stable and there was no sulfate,indicating that the ionic liquids chelated iron mixed solution could be recycled.Rhombic sulfur appears in the mixed solution,and H₂S is effectively utilized.The diffusion coefficient increases with the increase of temperature.The diffusion activation energy decreased with the increase of the concentration of iron chelate.When the concentration of iron chelate was 0.01 mol/L,the diffusion activation energy of ion-liquids iron chelate mixed solution was 25.11 and 23.24 k J/mol,respectively,which was lower than that of ion-liquids aqueous solution.The addition of iron chelate solution was helpful to accelerate the regeneration process.