The Liquid-liquid Phase Equilibrium And The Related Physical Properties Of CO₂ Switching Solvent Based On N,N-dimethylcyclohexylamine And N,N-Dimethylethanolamine

In recent years,studies on CO2 responsive switch solvents have inevitably attracted strong interest from researchers in chemical separation processes because of reversible conversion,environmental protection,low cost,and high safety factor.It is also a direction of green chemistry development.The physical data and the liquid-liquid phase equilibrium data about CO2 responsive switch solvents play an important role in the process.However,these data are rarely reported in the literatures.Therefore,in this paper,N,N-Dimethylcyclohexylamine(DMCA)and N,N-Dimethylethanolamine(DMEA)were selected to construct the CO2 Swithable-Hydrophilicity Solvents(SHS)and Swithable Water(SW).(1)The physical properties(density,viscosity,refractive index and electrical conductivity)data of([DMCAH][HCO3]+water+1,4-dioxane)were measured at the temperature from 278.15 K to 303.15 K.The influence of solvent compositions and temperature on these properties were analyzed.The parameters of volume properties such as apparent molar volume,standard partial molar volume,and the expansion rate of standard partial molar volume were calculated and discussed in accordance with the measured experimental density data,In addition to this,according to the measured viscosity data,the viscosity coefficient and relative viscosity parameters were studied in the same way.The model parameters were determined by the system studied,compared the caculated data by model with the experimental data,the results showed that the calculation results had good agreement with the experiment values.The largest root-mean-square deviations and the mean relative deviation were quite little.(2)The liquid-liquid equilibrium(LLE)data for the ternary Switchable-Hydrophilicity Solvents(SHS)system of N,N-dimethylcyclohexylamine bicarbonate([DMCAH][HCO3]+1,3-dioxolane+water,[DMCAH][HCO3]+1,4-dioxane+water and[DMCAH][HCO3]+tetrahydrofuran+water)was determined at 283.15 K,293.15 K and 303.15 K.Moreover,the selectivity coefficient and partition coefficient were also calculated from the experimental data.Finally,the electrolyte-Non-Random Two Liquids(e-NRTL)model was used to correlate the LLE experimental data.The error of the experimental value and the calculated value of e-NRTL model were quite little.The largest root-mean-square deviations were 1.030×10-3?9.099×10-4?6.703×10-4 respectively.The results indicated that the calculation results had good agreement with the experiment values.(3)The liquid-liquid equilibrium(LLE)data for the ternary Switchable Water(SW)system of N,N-dimethylethanolamine bicarbonate([DMEAH][HCO3])+1,3-dioxolane+water,[DMEAH][HCO3]+1,4-dioxane+water and[DMEAH][HCO3]+tetrahydrofuran+water was determined at 283.15 K,293.15 K and 303.15 K.Moreover,the selectivity coefficient and partition coefficient were calculated as well as based on the experimental data.Finally,in the ternary liquid-liquid system studied,the LLE data of the organic phase and the water phase are predicted by using the e-NRTL model.Furthermore,the veracity of the prediction results is also discussed.The error of the experimental value and the calculated value of e-NRTL model were quite little.The largest root-mean-square deviations were 2.29×10-3?2.41×10-3?3.57×10-3 respectively.The results indicated that the calculation results had good agreement with the experiment values.The experimental results not only provide theoretical foundation for the study of chemical separation thermodynamics,but also have directed importance for the research and development of green chemical CO2 switch solvents.