Patent ID: 8168822

Claim:
A method of making acetic acid comprising: (a) catalytically reacting methanol or a reactive derivative thereof with carbon monoxide in the presence of a homogeneous Group VIII metal catalyst and a methyl iodide promoter in a reactor vessel which contains a liquid reaction mixture including acetic acid, water, methyl acetate, methyl iodide and the homogeneous catalyst, the reactor vessel being operated at a reactor pressure; (b) withdrawing reaction mixture from the reaction vessel and feeding the withdrawn reaction mixture along with additional carbon monoxide to a pre-flasher/post reactor vessel operated at a reduced pressure below the reactor vessel pressure; (c) venting light ends in the pre-flasher vessel and concurrently consuming methyl acetate in the pre-flasher/post reactor vessel to produce a pre-flash mixture which is enriched in acetic acid and diminished in methyl iodide and methyl acetate as compared with the reaction mixture; (d) withdrawing the pre-flash reaction mixture from the pre-flasher/post reactor vessel and feeding the pre-flash mixture to a flash vessel; (e) flashing a crude acetic acid stream from the mixture in a flash vessel operated at a pressure substantially below the pressure of the pre-flasher/post reactor vessel; (f) recycling a post-flash residue from the flash vessel to the reactor vessel; and (g) purifying the crude product stream.