甲苯和C_(8)芳烃体系固液相平衡数据预测与相图

Prediction of solid-liquid equilibrium data and phase diagram fortoluene and C_(8) aromatics system

在对二甲苯结晶相关体系中,针对正常熔点非常接近的甲苯和乙苯两种组分同时存在的甲苯-乙苯二元体系及甲苯-乙苯-二甲苯三元体系,利用Van’t Hoff方程简式探索并计算了甲苯-乙苯二元体系低共熔点温度及组成,计算了甲苯-乙苯-二甲苯三元体系的液相摩尔分数和低共熔点温度及组成,并利用这些数据绘制了甲苯和乙苯两种组分同时存在的甲苯-乙苯-对二甲苯等3个三元体系的固液相平衡相图。预测了甲苯-乙苯、甲苯-间二甲苯和甲苯-邻二甲苯等3个二元体系的固液相平衡数据。这些相图和数据未见文献报道。利用甲苯-乙苯二元体系固液相平衡相图,分析了甲苯和乙苯混合物通过结晶工艺得到纯甲苯或纯乙苯的可能性,指出对于甲苯-乙苯二元体系,虽然甲苯和乙苯两种组分正常熔点非常接近,但由于该体系存在最低共熔点,可通过结晶工艺得到纯甲苯或纯乙苯,但不能同时得到纯甲苯和纯乙苯。

The normal melting points of toluene(TOL)and ethylbenzene(EB)are very close.For the TOL-EB binary system and the TOL-EB-xylene ternary system in which both exist at the same time,in the related system of p-xylene(PX)crystallization,the low eutectic temperature and composition of TOL-EB binary system are explored and calculated by the simplified Van't Hoff equation.The liquid phase molar fraction and eutectic point temperature and composition of TOL-EB-xylene ternary system are calculated by the simplified Van't Hoff equation.The solid-liquid phase equilibrium diagrams of three ternary systems,PX-EB-TOL,MX(m-xylene)-EB-TOL,OX(o-xylene)-EB-TOL,in which both TOL and EB are present have been drawn.The liquid phase molar fractions of three binary system,TOL-EB,TOL-MX,TOL-OX,are predicted.These phase diagrams and the predicted values have not been previously reported in the literature.The possibility of obtaining pure TOL or pure EB from the mixture of TOL and EB by crystallization process is analyzed by using the solid-liquid phase diagram of TOL-EB binary system.It is pointed out that for TOL-EB binary system,although the normal melting points of TOL and EB are very close,due to the lowest eutectic point of the system,pure TOL or pure EB can be obtained by crystallization process,but not at the same time.