Removal of permanganate reducing compounds from methanol carbonylation process stream
AssigneeCelanese International Corporation
InventorsMark O. Scates, David A. Trueba, Raymond J. Zinobile
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Abstract
An improvement of the methanol carbonylation process for manufacturing acetic acid is disclosed. Specifically disclosed is a method for reducing the formation of alkyl iodides and C3-8 carboxylic acids by removing permanganate reducing compounds (“PRC's”) from the light phase of the condensed light ends overhead stream, including (a) distilling the light phase to yield a PRC enriched overhead stream; and (b) extracting the third overhead stream with water in at least two consecutive stages and separating therefrom one or more aqueous streams containing PRC″s.
Claims73
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.
A process for producing acetic acid, comprising the steps of
- (a) carbonylating at least one reactant selected from the group consisting of methanol, methyl acetate, methyl formate and dimethyl ether in a reactor containing a suitable reaction medium comprising an organic iodide;
- (b) separating the products of said carbonylation into a volatile product phase comprising acetic acid, and a less volatile phase;
- (c) distilling said volatile product phase to yield a purified acetic acid product and a first overhead comprising said organic iodide and at least one permanganate reducing compound (PRC);
- (d) distilling at least a portion of the first overhead to produce a PRC-enriched second overhead, said second overhead further comprising dimethyl ether;
- and
- (e) extracting the second overhead with water, wherein step (e) comprises at least two consecutive extraction steps, each extraction step comprising contacting the second overhead with water and separating therefrom an aqueous stream comprising said at least one PRC.
A process for separating a mixture comprising water, acetic acid, methyl iodide, methyl acetate, methanol, and at least one permanganate reducing compound (PRC), said process comprising the steps of (a) distilling the mixture to separate the mixture into a plurality of streams, at least one of said streams being a PRC enriched overhead stream comprising dimethyl ether;
- and (b) extracting the PRC enriched overhead stream with water to produce an aqueous stream comprising said at least one PRC, and a raffinate stream comprising methyl iodide.
A process for separating a mixture comprising water, acetic acid, methyl iodide, methyl acetate, methanol, and at least one permanganate reducing compound (PRC), said process comprising the steps of:
- (a) distilling the mixture to separate the mixture into a plurality of streams, at least one of said streams being a PRC enriched overhead stream comprising dimethyl ether;
- and
- (b) extracting the PRC enriched overhead stream with water to produce an aqueous stream comprising said at least one RRC, and a raffinate stream comprising methyl iodide,
- wherein step (b) comprises at least two consecutive extraction steps, each extraction step comprising contacting the PRC enriched overhead stream with a water stream and separating therefrom said aqueous stream comprising said at least one PRC and said raffinate stream comprising methyl iodide, wherein a fresh water stream is used in each discrete extraction stage;
- or
- wherein step (b) comprises at least two consecutive extraction steps, each extraction step comprising contacting the PRC enriched overhead stream with a water stream and separating therefrom said aqueous stream comprising said at least one PRC and said raffinate stream comprising methyl iodide, wherein a single water stream passes through each of said discrete extraction stages in series;
- or
- wherein step (b) comprises contacting the PRC enriched overhead stream with a water stream and separating therefrom said aqueous stream comprising said at least one PRC and said raffinate stream comprising methyl iodide using a continuous contacting extractor;
- or a combination thereof.
A process for separating a mixture comprising water, acetic acid, methyl iodide, methyl acetate, methanol, and at least one permanganate reducing compound (PRC), said process comprising the steps of:
- (a) distilling the mixture to separate the mixture into a plurality of streams, at least one of said streams being a PRC enriched overhead stream comprising dimethyl ether;
- and
- (b) extracting the PRC enriched overhead stream with water to form a first raffinate and a first aqueous extract stream comprising said at least one PRC;
- followed by extracting the first raffinate with water to fern a second raffinate and a second aqueous extract stream comprising said at least one PRC.
Dependencies are inferred from the claim text.