The preparation of 6FCDA is as follows:Add 154g of 9,9-bis(trifluoromethyl)-2,3,6,7-xanthene tetracarboxylic acid (0.31mol) obtained in step into a 1L three-necked flask, and then add 539g of acetic anhydride ( 5.28mol), the temperature was raised to 105±2°C and the reaction was stirred for 5-6h. After the reaction was completed, the temperature was lowered to 25±2°C, filtered, the filter cake was rinsed with 300 g of toluene, and vacuum dried at 80°C for 15 hours to obtain a white powdery solid 131 g of 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthene tetracarboxyl dianhydride, purity (HPLC) was 99.6%, and yield was 91.8%.
