Process for producing acetic acid

A process for separating or removing permanganate reducing compounds (PRC's) from a first mixture containing at least one PRC, methyl iodide, and water, the process comprising the steps of:

• feeding the first mixture to a feed port of a distillation column, and
• distilling and separating the first mixture into an upper stream and a lower stream, the upper stream being at least one stream selected from the group consisting of an overhead stream and a side-cut stream,
• wherein the distillation of the first mixture allows at least a portion of water in the first mixture to rise to an upper position than the feed port to form a second mixture containing the portion of water, and
• the process further comprises the steps of:
• withdrawing the second mixture as the upper stream,
• withdrawing the lower stream from a lower position than the feed port, the lower stream having a water content, the water content of the lower stream being lower than that of the first mixture, and
• wherein the first mixture is separated into the upper stream and the lower stream without supply of additional water to the distillation column,
• the withdrawn upper stream is biphasically separated into an aqueous phase containing at least acetaldehyde and an organic phase containing at least methyl iodide, and
• the distillation of the first mixture comprises at least one of the following (A) and (B):
• (A) the lower stream has a ratio of water relative to methyl iodide lower than the first mixture, and
• (B) not less than 1% by weight of water in the first mixture is transferred or distributed to the upper stream, and not more than 99% by weight of water in the first mixture is transferred or distributed to the lower stream.