Processes for purifying acetic anhydride

A process for producing acetic anhydride comprising the steps of:

• contacting ketene gas with acetic acid in an absorber column to produce a liquid crude acetic anhydride stream and a residual ketene stream;
• feeding the liquid crude acetic anhydride stream directly to a distillation column;
• and
• purifying the liquid crude acetic anhydride stream to produce a light ends stream, a substantially pure acetic anhydride product stream, and a residue stream,
• wherein the substantially pure acetic anhydride product stream is withdrawn from the distillation column as a sidedraw,
• wherein the distillation column is operated at a pressure ranging from 20 kPa to 101 kPa,
• wherein the substantially pure acetic anhydride product stream comprises greater than 98 wt. % acetic anhydride, has a permanganate time greater than 10 minutes, and has an APHA color number of less than 10.

A process for purifying acetic anhydride comprising the steps of:

• feeding a liquid crude acetic anhydride stream directly to a distillation column;
• and
• separating the liquid crude acetic anhydride stream to produce a light ends stream, a sidedraw comprising substantially pure acetic anhydride product, and a residue stream,
• wherein the distillation column operates at a pressure less than 101 kPa and at a temperature less than 150° C.,
• wherein the substantially pure acetic anhydride product comprises greater than 98 wt. % acetic anhydride and has an APHA color of less than 10.