Method for preparing diphenic acid

The invention claims the biphenyl fei preparing formic acid a method of it comprises heating film and adding glacial acetic acid with a predetermined quantity of hydrogen peroxide with hydrogen peroxide after finishing dripping heating obtained mixture is reduced pressure distillation the mixture to make the volume of the semiconductor cooling the mixture into coupling benzoic acid of crystallizing to separate the filter said cooling the mixture and add in 10% sodium carbonate solution and active carbon after the residual liquid boiling filter and remove the residue; By using hydrochloric acid to acidulate the filter liquid cooling the mixture to be multiple benzoic acid precipitate crystalline; Repeated filtration operation to obtain pure benzoic acid linking.