The preparation of 3,3',4,4'-Biphenyltetracarboxylic dianhydride is as follows:In a nitrogen atmosphere, add N-(3-N,N-dimethylamino-propyl)-4-chlorophthalimide (26.65g, 0.1moL),Zinc powder (3.25g, 0.05moL), anhydrous NiCl2 (127.5mg, 1mmoL),Triphenylphosphine (250mg, 1mmoL) and 70 mL of anhydrous DMAc were stirred at 50°C for 24 hours, and 55mL of solvent DMAc was recovered under reduced pressure. Add 80g of xylene to the system and reflux (recrystallize), filter out the inorganic matter, the clarified filtrate will be cooled and precipitated, filtered, and vacuum dried for 10 hours. 21.8g of 3,3',4,4'-biphenylbisimine was obtained with a yield of 94%. In a 100mL reaction flask, add 4.62g (0.01mol) of the above 3,3',4,4'-biphenylbisimine and 9g of 20% sodium hydroxide aqueous solution, and heat to reflux for 24 hours. Filter and adjust pH=1 with concentrated hydrochloric acid to obtain 3,3’,4,4’-biphenyltetracarboxylic acid. After filtering, wash with water three times and reflux with water with 20mL trimethylbenzene.2.85g of white 3,3′,4,4′-biphenyltetracarboxylic dianhydride was obtained, the yield was 97%.
