Research On The Absorption Of CO₂ In Fe-based Composite Ionic Liquid Mixed Physical Solvent

Day by day the consumption of energy resources?hydrocarbons?including natural gas will be increased.To minimize pollution,the production of clean gas is main concern therefore the effective trap of H2S and CO₂ from natural gas is the focus of academic research in recent years.However,traditional chemical absorption methods and physical absorption methods have many flaws.Fe-based ionic liquid?[Bmim][FeCl₄]?not only have the characteristics of high thermal stability,low vapor pressure,and good solubility,but also have the ability of catalytic oxidation,which can absorb and oxide H2S into sulfur.However,its absorption properties for CO₂ are still unknown,and its high viscosity and strong acidity influence the mass transfer effect of acid gases.This research primarily explored the physicochemical parameters of pure Fe-based ionic liquid and the absorption properties of CO₂.The pure Fe-based ionic liquid was found to be one order of magnitude higher in viscosity than conventional physical solvents and had poor absorption of CO₂.The composite system based on the mixture of ionic liquid and physical solvent was an effective way to improve the physical properties of Fe-based ionic liquid.Two kinds of Fe-based composite ionic liquids,[Bmim][FeCl₄]/DMAC and[Bmim][FeCl₄]/NHD,were prepared by dimethylacetamide?DMAC?and 1,2-Dimethoxyethane?NHD?which had good acid gas solubility and lower viscosity.By investigating physical and the excess thermodynamic properties of the two complex ionic liquids,it was found that DMAC molecules intervened the anionic-cation gap of Fe-based ionic liquid weakened the hydrogen bonding between their anions and cations,and increasing their mobility which reduced the viscosity.When NHD molecules and Fe-based ionic liquid mixed together,the stronger hydrogen bonds were formed.[Bmim][FeCl₄]/NHD had a higher viscosity than its ideal mixed solution's viscosity.At a temperature of 298.15 K and a mass ratio of 7:3,the viscosity of[Bmim][FeCl₄]/DMAC is 8.67 mPa s,and the viscosity of[Bmim][FeCl₄]/NHD is 27.19 mPa·s.The investigation of CO₂ absorption performance showed that the two composite liquids systems were physically absorption processes for CO₂ absorption,and the CO₂ absorption is favorable under high pressure conditions.At the same temperature and mass ratio,[Bmim][FeCl₄]/DMAC has higher absorption capacity for CO₂ than[Bmim][FeCl₄]/NHD.After[Bmim][FeCl₄]/DMAC absorbs CO₂,it can be regenerated after decompressing it to normal pressure and heated up to 363.15K.After five cycles of absorption-regeneration,its solubility for CO₂ during first cycle was99.4%.Using the same conditions,the regeneration performance of[BmimjfFeCl₄]/NHD was poor.After five cycles of absorption-regeneration,the solubility of CO₂ was reduced to 92.53%during first cycle of the CO₂ absorption,and by increasing the number of cycles,its solubility for CO₂ continuously decline.