Removal of Small Amounts of Carbazole in Anthracene Using the Reaction with 9-Xanthenol

Abstract

Commercially available anthracene contains carbazole as an impurity and its removal is relatively difficult. It is known that many kinds of impurities except carbazole can be effectively eliminated from anthracene by zone melting. Therefore, the purification of anthracene can be carried out by the combination of the removal of carbazole and the zone melting. Authors have proposed a chemical method for the elimination of ppm order amounts of carbazole, using the reaction of carbazole with 9-xanthenol. After 15.0 g of anthracene containing 0.52% of carbazole and 300 mg of 9-xanthenol were dissolved in 500mL mixed solvent consisting of acetic acid, o-dichlorobenzene and concentrated hydrochloric acid (67: 30: 3), the solution has been heated at 85-87 °C for 1 h. Then, the solution has been cooled to approximately 0 °C, and the crystal of anthracene has been separated. The content of carbazole was about 120ppm and the recovery of anthracene was about 85%. This product was purified once more under the same conditions as mentioned above. The resulting product remained carbazole less than 1 ppm.