In order to solve the problem of thermodynamic data limitation of carbon dioxide ionic liquid(CO2-ILs)systems,phase equilibria of four new refrigeration working pairs(CO2-[C2-mim][Tf2N],CO2-[C4-mim][Tf2N],CO2-[C6-mim][Tf2N]and CO2-[C8-mim][Tf2N])were calculated by the selected equation of state + activity efficient method(EOS + γ method).The excess Gibbs free energy(GE),excess enthalpy(HE)and excess entropy(SE)of the binary systems were correlated according to the selected SRK(Soave-Redlich-Kwong)equation of state + WS(Wong-Sandler)mixing rule + UNIFAC activity coefficient model based on phase equilibria.The results show that excess properties of this system are affected by factors including temperature,pressure,CO2 molar fraction and cationic carbon chain length of the ionic liquids.The calculation results show that GE decreases with the increase of temperature,pressure and length of ILs cationic carbon chain.The maximum of GE is-1066.88 J·mol-1.HE decreases with the increase of temperature,molar fraction of CO2 and length of ILs cationic carbon chain.The maximum of HE is 407.24 J·mol-1.SE decreases with the increase of temperature and pressure,and increases with the increase of length of ILs cationic carbon chain.The maximum of SE is 7.88 J·mol-1·K-1.The accuracy of the model for excess property calculation can be proved by calculating ARD pressure values at vapor-liquid equilibrium.
关键词
汽液相平衡/SRK状态方程/WS混合规则/UNIFAC活度系数模型/超额性质预测
Key words
vapor-liquid equilibrium/SRK equation of state/WS mixing rule/UNIFAC model/excess properties
万方数据