Patent ID: 7589230

Claim:
A process for the preparation of diphenic acid from phenanthrene which comprises the steps of (i) heating phenanthrene and glacial acetic acid at a temperature in a range of 75 to 85° C. to form a mixture consisting essentially of the phenanthrene and the glacial acetic acid, (ii) adding drop-wise a pre-determined amount of a 30% solution hydrogen peroxide over a period of from 30 to 60 minutes to form a resulting mixture consisting essentially of the phenanthrene, the glacial acetic acid, the hydrogen peroxide and water, (iii) heating the resulting mixture for 3 to 7 hours after completion of drop-wise addition of hydrogen peroxide solution, (iv) distilling the resulting mixture under reduced pressure to make the volume half, (v) cooling the mixture until diphenic acid crystalises out, (vi) filtering the cooled mixture to form a residue and a filtrate, and boiling the residue after adding 10% solution of sodium carbonate and activated charcoal, (vii) filtering and discarding the residue; (viii) acidifying the filtrate with hydrogen chloride to form a resultant mixture; (ix) cooling the resultant mixture until more diphenic acid crystallises out; and (x) repeating filtration till pure diphenic acid is obtained.