FIELD: chemistry.
SUBSTANCE: invention relates to an improved method of reducing and/or removing reducing permanganate compounds (RPC), carboxylic acids C3-8 and C2-12 of alkyl iodide compounds, formed during carbonylation of a carbonylation-capable reagent, chosen from a group consisting of methanol, methylacetate, methyl formate, dimethyl ether and their mixture, into commercial-grade acetic acid, in which products of the said carbonylation include a volatile phase, which is distilled thereby obtaining purified commercial-grade acetic acid and the first distillate, containing methyl iodide, water and at least one reducing permanganate compound, where improvement includes stages: (a) separation of the obtained first distillate into a light and a heavy phase, with subsequent distillation of at least part of the light phase for obtaining a second distillate, containing methyl iodide, dimethyl ether and at least said one reducing permanganate compound, which is taken to the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound; (b) addition of dimethyl ether into supply of said stream containing reducing permanganate compound, and extraction of this stream with water to form the first raffinate and first aqueous extraction stream, containing at least said one reducing permanganate compound; and (c) extraction of the first raffinate with water to form the second raffinate and second aqueous extraction stream, containing at least said one reducing permanganate compound. Invention also relates to a method of separating a mixture, containing water, acetic acid, methyl iodide, methyl acetate, methanol and at least one reducing permanganate compound (RPC), obtained by separating the liquid-vapour phase of the output stream of the methaol carbonylation reactor to form a vapour phase and a liquid phase, distillation of the vapour phase to form a liquid product which contains acetic acid, and first distillate, condensation of at least part of the first distillate thereby obtaining a liquid composition which contains methyl acetate, methyl iodide, water, methanol and at least one reducing permanganate compound (RPC), separation of the obtained liquid composition into a light and a heavy phase, which includes methyl iodide, where the light phase is the said mixture, where the said method involves stages: (a) distillation of the mixture to obtain a second distillate which contains at least one reducing permanganate compound (RPC), which is taken for the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound and dimethyl ether; and (b) extraction of concentrated reducing permanganate compound with water, where stage (b) includes at least two consecutive extraction stages, where each extraction stage involves bringing concentrated reducing permanganate compound into contact with water and separation of the aqueous stream, containing at least said one reducing permanganate compound, where dimethyl ether is added to the said distillate stream concentrated with reducing permanganate compound before extraction of the concentrated reducing permanganate compound with water.
EFFECT: process is described for removing reducing permanganate compounds from a stream from carbonylation of methanol.
28 cl, 2 dwg
