关键词: 甲苯, C₈芳烃, 固液相平衡, 相图, 二元体系, 三元体系

Abstract: 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.    

Key words: toluene, C₈ aromatics, solid-liquid phase equilibria, phase diagram, binary system, ternary system