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

区域熔融法是制备超纯有机化合物最有效的方法之一。然而，由于分离速度较慢，目前还没有工业规模的分离提纯过程。在本工作中，通过实验研究了电场对正常冻结的影响，以检验电场是否可以提高分离效率。本工作尝试用常规冷冻法对3，5-二甲酚+萘体系进行提纯。这是一种简单的形成共晶的混合物。在6000V/cm和10000 V/cm的凝固过程中，通过施加与固液界面平行的电场，实验考察了电场对分离效率的影响。初始杂质浓度为5wt%。固化后，用气相色谱分析固体样品中的杂质浓度。此外，还利用带摄像机的显微镜观察了凝固前沿和液体中的流态。当3，5-二甲酚为主要组分时，电场降低了杂质(萘)的浓度。这可能是由于电场在液相中诱导的对流，这在显微镜下可以清楚地观察到。当以萘为主要组分时，电场使杂质(3，5-二甲酚)的浓度增加。它随电场强度的增大而增大。在这种情况下，当施加电场时，显微镜下观察到许多细小的晶体，因此3，5-二甲酚(杂质)可能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.