Preparation of acetic acid

A method for producing acetic acid, said method comprising:

• (a) reacting methanol and carbon monoxide in the presence of a carbonylation catalyst, a catalyst stabilizer, methyl iodide, water, and methyl acetate to produce a reaction mixture comprising acetic acid, water, methyl acetate, methyl iodide, the catalyst, the catalyst stabilizer, and aldehydes;
• (b) flashing at least a portion of the reaction mixture to produce a vapor stream comprising acetic acid, water, methyl acetate, methyl iodide, and aldehydes and a liquid stream comprising the catalyst and the catalyst stabilizer;
• (c) distilling the vapor stream to form an overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and aldehydes, and an acetic acid stream comprising acetic acid, aldehydes, and water;
• (d) separating the overhead stream into a light aqueous phase comprising water and a heavy phase comprising methyl iodide and aldehydes;
• (e) recycling the liquid stream and the heavy phase to step (a);
• wherein at least a portion of the aldehydes from the heavy phase is removed by the following steps:
• (i) reacting at least a portion of the heavy phase with an alcohol to form an acetal-containing stream;
• (ii) distilling the acetal-containing stream into a recovered methyl iodide stream and an acetal-enriched stream;
• (iii) recycling the recovered methyl iodide stream to step (a);
• (iv) hydrolyzing the acetal-enriched stream to form a hydrolysis mixture comprising the alcohol and the aldehydes;
• and
• (v) isolating the alcohol from the hydrolysis mixture and recycling the alcohol to step (i).