Patent ID: 7619113

Claim:
A carbonylation process for producing acetic acid comprising: (a) carbonylating methanol or its reactive derivatives in the presence of water, a catalyst selected from rhodium catalysts, iridium catalysts and mixtures thereof, and a methyl iodide promoter to form an acetic acid reaction mixture in a reactor; (b) separating the stream of the acetic acid reaction mixture into a liquid recycle stream and a crude product stream including acetic acid, methyl iodide, methyl acetate and water; (c) feeding the crude product stream to a light ends column having a distillation zone; (d) purifying the crude product stream in the distillation zone of the light ends column to remove methyl iodide and methyl acetate and generate a purified product stream, the purified product stream having a lower concentration of methyl iodide and methyl acetate than the crude product stream, and wherein the step of purifying the crude product stream includes (i) condensing overhead vapor from the distillation zone of the light ends column, (ii) decanting the condensed vapor into a heavy phase comprising predominantly methyl iodide and a light phase comprising predominantly acetic acid and water, and (iii) refluxing at least a portion of the condensed heavy phase to the distillation zone of the light ends column; and (e) drawing a purified product stream from the light ends column.