Process for producing acetic acid

A process for producing acetic acid, comprising

• contacting carbon monoxide and one or more of methanol and reactive derivatives thereof with a carbonylation catalyst in a first reaction zone to produce a product stream and an off-gas stream, the product stream comprising water, acetic acid, carbon monoxide, the carbonylation catalyst, and one or more of methanol and reactive derivatives thereof;
• through a reaction zone inlet of a second reaction zone, transferring at least a portion of the product stream into the second reaction zone;
• at a first position between the reaction zone inlet and an outlet of the second reaction zone, introducing a first vapour stream to the second reaction zone, the first vapour stream comprising carbon monoxide and having a carbon monoxide concentration;
• at a second position between the reaction zone inlet and the outlet of the second reaction zone, introducing a second vapour stream to the second reaction zone, the second vapour stream comprising carbon monoxide and having a lower carbon monoxide concentration than the carbon monoxide concentration of the first vapour stream;
• and
• through the outlet, withdrawing an effluent of the second reaction zone;
• wherein the first position is between the reaction zone inlet and the second position.