Patent ID: 10781155

Abstract:
Provided are a method and an acetic acid production method, each of which can effectively restrain or prevent local corrosion of an inner wall of a process unit and/or line and can lower a formic acid concentration in an acetic acid product. The method produces acetic acid by a process including (1) a reaction step and (A) a separation step. In the reaction step (1), methanol is carbonylated with carbon monoxide in the presence of a catalytic system, acetic acid, methyl acetate, and water, where the catalytic system includes a metal catalyst and methyl iodide. In the separation step (A), the reaction mixture resulting from the reaction step is separated, using at least one selected from evaporators and distillation columns, into a stream containing the catalyst, an acetic acid stream rich in acetic acid, and a stream rich in lower-boiling components as compared with the acetic acid stream. In this method, an oxygen concentration is controlled by at least one of (a) controlling the oxygen concentration in a gaseous phase in the process to less than 7 percent by volume, and (b) controlling the oxygen concentration in a liquid phase in the process to less than 7×10−5 g/g. In addition, a formic acid concentration in the liquid phase in the process is controlled to 500 ppm by mass or less. Thus, the formation of at least one of iodine and formic acid is restrained.