FUNDAMENTAL STUDY ON PURIFICATION OF ORGANIC COMPOUNDS BY CRYSTALLIZATION WITH APPLYING ELECTRIC FIELD

区熔法是制备超纯有机化合物的有效方法之一。然而，由于分离速度慢，其尚未应用于工业规模的分离和纯化过程。为了验证电场是否能提高分离效率，本文对电场对正常冻结的影响进行了实验研究。本文尝试了用常规冷冻法提纯3，5-二甲酚+萘体系。这是一种简单的形成共晶的混合物。通过在固化期间以6，000V/cm或10，000V/cm施加平行于固-液界面的电场，实验性地研究了电场对分离效率的影响。初始杂质浓度为5wt%。固化后，通过气相色谱法分析固体样品的杂质浓度。此外，还通过使用带摄像机的显微镜观察了凝固前沿和液相中的流动图案。当3，5-二甲酚是主要成分时，杂质（萘）的浓度通过电场降低。这可能是由于电场诱导液相中的对流，这在显微镜下可以清楚地观察到。另一方面，当萘是主要成分时，杂质（3，5-二甲苯酚）的浓度通过电场而增加。随着电场强度的增加，其电导率也随之增加。在这种情况下，当施加电场时，通过显微镜观察到许多小晶体，使得3，5-二甲酚（杂质）可以更多地吸附在晶界上。

Zone melting is one of the most efficient methods to get ultrapure organic compounds. However, it has not yet been applied to separation and purification processes in industrial scale, because the rate of separation is slow. In this work, the effect of an electric field on normal freezing was investigated experimentally, in order to examine whether an electric field can improve the separation efficiency or not. In this work, purification of 3,5-xylenol+naphthalene system was attempted by normal freezing. This is a simple eutectic-forming mixture. The effect of an electric field on the separation efficiency was experimentally examined by applying an electric field in parallel with the solid-liquid interface during solidification at 6,000 V/cm or 10,000 V/cm. The initial impurity concentration was 5wt%. After the solidification, The concentration of the impurity for the solid sample was analyzed by a gas chromatography. Furthermore, the solidification front and the flow pattern in the liquid phase were also observed by using a microscope with a video camera. When 3,5-xylenol was the main component, the concentration of the impurity (naphthalene) was decreased by an electric field. This may due to the convection in the liquid phase induced by the electric field, which was clearly observed through the microscope. On the other hand, when naphthalene was the main component, the concentration of the impurity (3,5-xylenol) was increased by an electric field. It was increased with increasing the strength of electric field. In this case, a lot of small crystals were observed through the microscope when the electric field was applied, so that 3,5-xylenol (impurity) may be adsorbed much more on grain boundaries.