| Efficient capture of carbon dioxide（CO2）and hydrogen sulfide（H2S）is an effective way to reduce greenhouse gas emissions and syngas purification.Amine scrubbing and Rectisol technology are commonly used in industrial acid gas removal.However,the amine is easy to evaporate and degrade,resulting in loss and equipment corrosion.And solvent regeneration energy consumption is high.Rectisol needs to operate at low temperature and high pressure,and the refrigeration system needs to consume a lot of energy.As a green solvent,ionic liquids have shown excellent performance in the field of gas purification,but high cost and high viscosity still hinder the industrial application of ionic liquids.To solve the above problems,three protic ionic liquids with low production cost and low viscosity,namely N-Ethylmorpholine acetate（[NEMH][Ac]）,N-Ethylmorpholine propionate（[NEMH][Pro]）,and Triethylamine propionate（[TEAH][Pro]）,were synthesized in this paper,and the solubility of CO2 in them was measured.The solubility data were correlated by Pitzer’s model and Soave-Redlich-Kwong（SRK）cubic equation of state.Both models had satisfactory fitting accuracy,and the average relative deviation between the predicted and experimental values was less than 1.5%.Henry’s law constants of CO2 in these three protic ionic liquids at zero pressure were estimated from the solubility data,and the partial molar Gibbs free energy,partial molar enthalpy,and partial molar entropy at infinite dilution were calculated.These three protic ionic liquids have good CO2capture ability,and their molality solubility is significantly higher than that of ordinary imidazole ionic liquids.CO2 has a higher molality solubility in[NEMH][Ac]relative to[NEMH][Pro]and[TEAH][Pro].These three protic ionic liquids have good application prospects in the syngas purification process.At present,the research on ionic liquids for capturing acid gases is still in the laboratory stage.In order to promote the industrial application of ionic liquids in the field of syngas purification,the ionic liquids used in the design of desulfurization and decarburization process were sorted out in this paper.By comparing the viscosity of ionic liquids and the solubility of CO2 in ionic liquids,[NEMH][Ac]with low viscosity and high capacity was selected as absorbent for syngas purification process.The critical properties of[NEMH][Ac]were estimated by group contribution method,and the[NEMH][Ac]was customized in Aspen Plus software according to the basic physical properties data of[NEMH][Ac].Materials Studio software was used to perform quantum chemical calculations on[NEMH][Ac]and each component in syngas,and the parameters of COSMO-SAC model were obtained.The solubility of each component in syngas in[NEMH][Ac]was predicted.The binary interaction parameters of the SRK cubic equation of state were regressed from the experimental data for CO2 and the predicted data for the remaining gases.The purification process of syngas based on ionic liquid[NEMH][Ac]was simulated and optimized.The results showed that the capture rate of both CO2 and H2S by this process was over 95%.The recovery rate of effective gas can reach 99.6%,which is in line with the requirements of the operation specification for syngas purification process.This process can be operated at room temperature,avoiding a large amount of refrigeration energy consumption caused by low temperature operation,and the solvent recovery rate is higher than Rectisol.Compared with the syngas purification process based on ionic liquid 1-butyl-3-methylimidazolium bis（trifluoromethylsulfonyl）imide（[BMIM][Tf2N]）,this process has higher CO2 and H2S capture rate,lower sulfur content in CO2 product gas and less absorbent dosage.Therefore,this process has good industrial application potential and development prospect in the field of syngas purification. |
