Preparation of acetic acid
View Patent ↗A method for reducing aldehydes in an acetic acid production process is disclosed. The acetic acid is produced by reacting methanol and carbon monoxide in the presence of a carbonylation catalyst. The method comprises reacting an aldehyde-containing stream with an alcohol to form an acetal-containing stream. An acetal-enriched stream is separated from the acetal-containing stream and then hydrolyzed to form a hydrolysis mixture comprising the alcohol and the aldehydes. The alcohol is isolated from the hydrolysis mixture and used to react with the aldehyde-containing stream to form the acetal-containing stream. The invention reduces aldehydes in the acetic acid produced.
1. A method for reducing aldehydes from an acetic acid production process by reacting methanol and carbon monoxide in the presence of a carbonylation catalyst to produce at least one aldehyde-containing stream, said method comprising reacting the aldehyde-containing stream with an alcohol to form an acetal-containing stream, separating an acetal-enriched stream from the acetal-containing stream, hydrolyzing the acetal-enriched stream to form a hydrolysis mixture comprising the alcohol and the aldehydes, isolating the alcohol from the hydrolysis mixture, and recycling the alcohol to the acetal forming step.
2. The method of claim 1 wherein the alcohol is selected from the group consisting of C 4 -C 10 mono-alcohols, C 2 -C 10 glycols, C 3 -C 10 glycerins, and mixtures thereof.
3. The method of claim 1 , wherein the alcohol is a glycol selected from the group consisting of 2-methyl-1,3-propanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, cyclohexane-1,4-dimethanol, neopentyl glycol, and mixtures thereof.
4. The method of claim 1 , wherein the alcohol is 2-methyl-1,3-propanediol.
5. A method for producing acetic acid, said method comprising:
(a) reacting methanol and carbon monoxide in the presence of a carbonylation catalyst, a catalyst stabilizer, methyl iodide, water, and methyl acetate to produce a reaction mixture comprising acetic acid, water, methyl acetate, methyl iodide, the catalyst, the catalyst stabilizer, and aldehydes;
(b) flashing at least a portion of the reaction mixture to produce a vapor stream comprising acetic acid, water, methyl acetate, methyl iodide, and aldehydes and a liquid stream comprising the catalyst and the catalyst stabilizer;
(c) distilling the vapor stream to form an overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and aldehydes, and an acetic acid stream comprising acetic acid, aldehydes, and water;
(d) separating the overhead stream into a light aqueous phase comprising water and a heavy phase comprising methyl iodide and aldehydes;
(e) recycling the liquid stream and the heavy phase to step (a); wherein at least a portion of the aldehydes from the heavy phase is removed by the following steps:
(i) reacting at least a portion of the heavy phase with an alcohol to form an acetal-containing stream;
(ii) distilling the acetal-containing stream into a recovered methyl iodide stream and an acetal-enriched stream;
(iii) recycling the recovered methyl iodide stream to step (a);
(iv) hydrolyzing the acetal-enriched stream to form a hydrolysis mixture comprising the alcohol and the aldehydes; and
(v) isolating the alcohol from the hydrolysis mixture and recycling the alcohol to step (i).
6. The method of claim 5 further comprising purifying the acetic acid stream by a drying column distillation and a heavy-end column distillation to produce purified acetic acid.
7. The method of claim 5 wherein the alcohol is selected from the group consisting of C 4 -C 10 mono-alcohols, C 2 -C 10 glycols, C 3 -C 10 glycerins, and mixtures thereof.
8. The method of claim 5 , wherein the alcohol is a glycol selected from the group consisting of 2-methyl-1,3-propanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, cyclohexane-1 ,4-dimethanol, neopentyl glycol, and mixtures thereof.
9. The method of claim 5 , wherein the alcohol is 2-methyl-1 ,3-propanediol.
10. The method of claim 5 , wherein the reaction between the heavy phase and the alcohol is performed in the presence of an acidic resin.
11. The method of claim 10 , wherein the acidic resin is a sulfonic resin.
12. The method of claim 5 , wherein the hydrolysis of the acetal-enriched stream is performed in the presence of an acidic resin.
13. The method of claim 12 , wherein the acidic resin is a sulfonic resin.
14. The method of claim 5 , wherein the catalyst stabilizer is a pentavalent Group VA oxide.
15. The method of claim 5 , wherein the catalyst stabilizer is a phosphine oxide.