PURPOSE: To obtain high-purity diphenic acid in high efficiency, by oxidizing phenanthrene with a peroxide to produce diphenic acid, extracting unreacted phenanthrene with a solvent, recovering diphenic acid with a strong acid and purifying and recrystallizing the product.
CONSTITUTION: Phenanthrene is oxidized with a peroxide (especially preferably peracetic acid, etc.) for 30W40min keeping at 60°C to produce diphenic acid. The unreacted phenanthrene existing in the reaction liquid is extracted with a solvent such as toluene. Diphenic acid is recovered from the reaction liquid with a strong acid such as hydrochloric acid and recrystallized with an organic solvent to obtain diphenic acid having high purity.
EFFECT: Diphenic acid can be recovered in high efficiency without necessitating the neutralization of acid in mother liquor. The process is practicable taking the reutilization of the mother liquor into consideration. A high-purity diphenic acid can be produced from phenanthrene which is an unused component of coal tar and the produced diphenic acid can be used as a raw material of high- quality polyesters.
NARUSE YOSHIHIRO
ENOMOTO NORIHIDE
