A low energy process for producing acetic acid by the carbonylation of
methanol is disclosed. The process involves a rhodium-catalyzed system
operated at less than about 14% water utilizing up to 2 distillation
columns. The process is preferably controlled such that the product stream
has a low level of propionic acid impurity and the level of aldehyde
impurities is minimized by way of aldehyde removal or minimizing aldehyde
generation. The level of iodides is controlled by contacting the product,
at elevated temperatures, with ion exchange resins. In preferred
embodiments, at least one silver or mercury exchanged macroreticular
strong acid ion exchange resin is used to purify the product. The high
temperature treatment provides the added benefit of controlling the Color
Value (Pt--Co units) of the product stream.