If acetic anhydride is to be used for research, then sodium wire is placed inside it for few days followed by removing the sodium & applying distillation under vacuum to obtain the anhydride in the receiving flask.

Alternatively, shake acetic anhydride with P2O5 & separate. Then shake the anhydride with potassium carbonate & apply fractional distillation while the carbonate is still inside the anhydride.

If there is no research, acetic anhydride could be dried using the famous sulfates such as anhydrous MgSO4 which is a good drying agent. Decant the anhydride carefully. Of course, decant means to pour liquid & leave solid behind.

Thanks

Can we use benzophenone with sodium for acetic anhydride distillation.