Removal of permanganate reducing compounds from methanol carbonylation process stream

摘要

Disclosed is an improved method for reduction and/or removal of permanganate- reducing compounds (PRC's), C3-8 carboxylic acids and C2-12 alkyl iodide compounds formed in the carbonylation of a carbonylatable reactant selected from the group consisting of methanol, methyl acetate, methyl formate and dimethyl ether and mixtures thereof to an acetic acid product, the products of said carbonylation including a volatile phase that is distilled to yield a purified acetic acid product and a first overhead comprising methyl iodide, water and at least one PRC, wherein the improvement comprises the steps of : (a) distilling at least a portion of the first overhead to produce a second overhead stream comprising methyl iodide, dimethyl ether, and said at least one PRC; (b) extracting the second overhead stream with water to form a first raffinate and a first aqueous extract stream containing said at least one PRC; and (c) extracting the first raffinate with water to form a second raffinate and a second aqueous extract stream containing said at least one PRC.