Study On The Phase Equilibria Of The Systems In Acromatic Extraction Process With N-Formylmorpholine As Solvent

NFM is widely used as solvent in the extractive distillation process for its highselectivity, solvency, non-toxic, non-corrosion, low viscosity, moderate boiling pointand freezing points, the chemical stability and high thermal stability. NFM is one ofthe most commonly used solvent in the aromatic extraction process of the ethylenecracking and oil refining. The accurate and reliable phase equilibrium data arerequired for the process design and improvement in the extractive distillationprocess.. Thus, It is of great significance to study on the phase equilibria of thesystems in acromatic extraction process with NFM as solvent.In this study, the （vapour-liquid） equilibrium data of the four binary systemsethylbenzene-NFM, butylbenzene-NFM, isopropylbenzene-NFM,1,2,4-trimethylbenzene-NFM were measured by the modified Rose still atatmospheric pressure. All the experimental data were passedthe thermodynamicconsistency tests. The experimental data were correlated by the NRTL andUNIQUAC models and the interactional parameters for the binary systems wereobtained.A set of apparatus was designed and constructed in this work. The equilibrium T,x, x data for the NFM with alkane （1,3-dimethyl-cyclohexane, n-propylcyclohexane,3-methylpentane, heptane, nonane and2,2,4-trimethylpentane） systems were obtainedin the operating temperature range （from around300K to close to420K） of the NFMextractive distillation process. The experimental data were correlated by the NRTLand UNIQUAC models with the function of temperature-independent parameters. Thebinary interaction parameters obtained from the data of ethylbenzene-NFM and2,2,4-trimethylpentane-NFM were used to calculated the ternary liquid-liquid phaseequilibrium data of2,2,4-trimethylpentane-ethylbenzene-NFM by NRTL model.In this study, the modified UNIFAC-Dortmund model was used to estimate thevapor-liquid phase equilibrium data and the liquid-liquid phase equilibrium data inaromatics extraction using Aspen Plus software. Two group division methods wereused to NFM. NFM is treated as a group: NFM group （methodⅠ） or divided into twobasic groups: CHO and C₄H₈NO （methodⅡ）, respectively. The group interactionparameters for CH₂-NFM, CH₂-CHO, CH₂-C₄H₈NO, c-CH₂-NFM, c-CH₂-CHO andc-CH₂-C₄H₈NO were regressed from the experimental LLE data. Then UNIFAC （Do）model with these group interaction parameters were used to estimate phaseequilibrium data of binary system iso-pentane （1）+NFM （2）. The estimated results were correlated by the NRTL and UNIQUAC models and the interactional parameters forthe systems were obtained. The methodⅠwas used to the systems of VLE data, Thegroup interaction parameters for ACH-NFM, and ACCH₂-NFM were regressed fromthe experimental VLE data. Then the group interaction parameters were used toestimate phase equilibrium data of binary systems of1-methyl-3-ethylbenzene（1）-NFM （2） and1,2-dimethyl-3-ethylbenzene （1）-NFM （2）.