Patent ID: 7485749

Claim:
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 an acetic acid stream comprising acetic acid, water, methyl acetate, methyl iodide, the catalyst, the catalyst stabilizer, and an aldehyde impurity; (b) flashing at least a portion of the acetic acid stream to produce a vapor stream comprising acetic acid, water, methyl acetate, methyl iodide and the aldehyde impurity, and a liquid stream comprising the catalyst and the catalyst stabilizer; (c) separating the vapor stream using a distillation column into an acetic acid product stream comprising acetic acid, the aldehyde impurity, and a minor amount of water, and an overhead stream comprising methyl iodide, water, acetic acid, and methyl acetate; (d) feeding the acetic acid product stream and a hydroxyl compound selected from the group consisting of glycols, glycerin, and C 4-10 alcohols into a distillation column, wherein the aldehyde impurity reacts with the hydroxyl compound to form an acetal, and wherein the water is removed from a top portion of the distillation column and an essentially anhydrous acetic acid product stream comprising acetic acid and the acetal is taken from the distillation column; and (e) separating the acetal from acetic acid by distillation.