Experiment Study On [BMP][Tf₂n] Ionic Liquid Basic Physical Properties And CO₂ Solubility Charicteristic

Energy and environment are the hot issues that the world has been paying close attention to.In recent years,absorption refrigeration technology using low-grade heat source has been widely concerned by refrigeration scholars at home and abroad for its ability to relieve energy shortage due to the gradual increase of energy consumption in refrigeration.One of the factors affecting absorption refrigeration technology is refrigeration working pairs.In order to widely apply absorption refrigeration technology,scholars began to study refrigeration working pairs.Natural working medium CO₂ is concerned and studied by scholars because of its advantages of large refrigerating capacity per unit volume and environmental friendliness.With the introduction of ionic liquids,working medium pair CO₂-ionic liquids are used in absorption refrigeration systems.The study of basic physical properties of ionic liquids and the dissolution characteristics of CO2 in ionic liquids lay the foundation for the application of working medium pair CO₂-ionic liquids in absorption refrigeration systems.After investigation,ionic liquid[BMP][Tf₂N]（1-butyl-1-methyl-pyrrolidine bis（trifluoromethylsulfonyl）imine）has good CO₂ absorption capacity,so this paper takes ionic liquid[BMP][Tf₂N]and CO₂ as research objects.Firstly,the basic physical properties of ionic liquid[BMP][Tf₂N]were experimentally studied.When the pressure was 101.325KPa and the temperature changes in the range of298.15³38.15 K,the viscosity of ionic liquid[BMP][Tf₂N]was measured by using a rotary viscometer.The variation law of the viscosity of ionic liquid[BMP][Tf₂N]showing a decreasing trend with the increase of temperature was obtained,and the viscosity value range is 0.0216⁰.0818Pa.s;The density of ionic liquid[BMP][Tf₂N]was measured by an electronic analytical balance,and the change rule of the density of ionic liquid[BMP][Tf₂N]showing a decreasing trend with the increase of temperature was obtained,and the density value range was 1356¹389 kg/m³.The electrical conductivity of ionic liquid[BMP][Tf₂N]electrical was measured by digital display conductivity meter,and the change rule of ionic liquid[BMP][Tf₂N]electrical conductivity decreasing with the increase of temperature was obtained,and the electrical conductivity value was 0.273⁰.893S/m;The surface tension of ionic liquid[BMP][Tf₂N]was measured by a full-automatic surface tension meter.The change rule of the surface tension value of ionic liquid[BMP][Tf₂N]showing an increasing trend with the increase of temperature was obtained,and the surface tension value range was 0.0318⁰.0329N/m,which made up for the lack of basic physical property data of ionic liquid[BMP][Tf₂N].Secondly,the viscosity,density,electrical conductivity and surface tension of basic physical properties of ionic liquid[BMP][Tf₂N]were predicted.Arrhenius equation was used to correlate the viscosity experimental data of ionic liquid[BMP][Tf₂N]to predict the viscosity of ionic liquid[BMP][Tf₂N],and the correlation coefficient was 0.995 5.The maximum relative error and average relative error between predicted value and experimental value were 2.25%and 0.94%.The density of ionic liquid[BMP][Tf₂N]was predicted by using the density experimental data of ionic liquid[BMP][Tf₂N]with the natural logarithmic equation,and the correlation coefficient was 0.995 97.The maximum relative error and average relative error between the predicted value and the experimental value were 5.74%and 5.39%.The electrical conductivity of ionic liquid[BMP][Tf₂N]was predicted by using VFT equation to correlate the conductivity experimental data of ionic liquid[BMP][Tf₂N].The predicted result shows that the correlation coefficient was 0.99499,and the maximum relative error and average relative error between the predicted value and the experimental value were 4.41%and 4.24%respectively.The surface tension of ionic liquid[BMP][Tf₂N]was predicted by using linear equation to correlate the experimental data of the surface tension of ionic liquid[BMP][Tf₂N].The prediction results show that the correlation coefficient was 0.985,and the maximum relative error and average relative error between the predicted value and the experimental value was 4.53%and 4.63%,respectively.The predicted value was highly consistent with the experimental value.Therefore Arrhenius equation,natural logarithm equation,VFT equation and linear equation are respectively applicable to predict the viscosity,density,electrical conductivity and surface tension of[BMP][Tf₂N],laying a foundation for obtaining more basic physical properties.Finally,the solubility characteristics of CO₂ in ionic liquid[BMP][Tf₂N]was experimentally studied,the vapor-liquid equilibrium characteristics of CO₂-[BMP][Tf₂N]refrigerant pair.The CO₂ dissolution characteristics are experimentally studied by static method when the temperature was 283.15³63.15 K and the pressure was 0.2⁵ MPa by using a self-modified CO₂ solubility characteristics experimental table.The experimental results show that when the temperature was constant,the solubility of CO₂ in[BMP][Tf₂N]increases with the increase of pressure,and when the pressure was constant,the solubility of CO₂ in[BMP][Tf₂N]decreases with the increase of temperature.The molar fraction of CO₂ liquid phase ranges from 0.1235 to 0.5324.When the temperature was 283.15MPa and the pressure was 3.48MPa,the molar fraction of CO₂ liquid phase can be as high as0.5324.Therefore,it is believed that CO₂-[BMP][Tf₂N]can be used as refrigeration working pair,which lays a foundation for its application in absorption refrigeration system.