Patent ID: 8742168

Claim:
A process for producing acetic acid which comprises: (a) carbonylating methanol in the presence of a catalyst in a reaction zone to obtain a reaction zone to obtain a reaction mixture (A) comprising the acetic acid, hydrogen iodide, methyl iodide, water and the catalyst; (b) withdrawing at least a part of the reaction mixture (A) from the reaction zone; (c) introducing the withdrawn part of the reaction mixture (A) into a flash zone; (d) contacting the withdrawn part of the reaction mixture (A) in the flash zone with an alkylimidazolium iodide to form a secondary mixture (B); (e) separating the secondary mixture (B) in the flash zone to obtain a vapor stream (B V ) comprising acetic acid, water and methyl iodide, and a liquid stream (B L ) comprising the catalyst, the alkylimidazolium iodide and hydrogen iodide; and (f) recycling the liquid stream (B L ) to the reaction zone; wherein the reaction mixture (A) is brought into contact with the alkylimidazolium iodide in the flash zone 1) by introducing to the flash zone separately from the withdrawn reaction mixture (A) an extraneous alkylimidazolium iodide; or 2) by introducing to the flash zone separately from the withdrawn reaction mixture (A) an alkylimidazole and forming the alkylimidazolium iodide in situ by reacting the alkylimidazole with the hydrogen iodide and/or the methyl iodide.