US 6,657,078 B2Granted

Low energy carbonylation process

AssigneeCelanese International Corporation

InventorsMark O. Scates, George A. Blay, G. Paull Torrence, Jerry A. Broussard

Life of this patent

Estimating the term…

Loading patent…

Abstract

A low energy process for producing acetic acid by the carbonylation of methanol is disclosed. The process involves a rhodium-catalyzed system operated at less than about 14% water utilizing up to 2 distillation columns. The process is preferably controlled such that the product stream has a low level of propionic acid impurity and the level of aldehyde impurities is minimized by way of aldehyde removal or minimizing aldehyde generation. The level of iodides is controlled by contacting the product, at elevated temperatures, with ion exchange resins. In preferred embodiments, at least one silver or mercury exchanged macroreticular strong acid ion exchange resin is used to purify the product. The high temperature treatment provides the added benefit of controlling the Color Value (Pt—Co units) of the product stream.

Claims28

Dependent claims

A continuous process for producing acetic acid comprising:

(a) reacting methanol with a carbon monoxide feedstock in a carbonylation reactor holding a catalytic reaction medium while maintaining in said reaction medium during the course of said reaction at least a finite concentration of from about 0.1 weight percent up to less than 14 weight percent of water;
(b) withdrawing a stream of said reaction medium from said reactor and vaporizing a portion of said withdrawn medium in a flashing step;
(c) distilling the flashed vapor to form a liquid acetic acid product stream utilizing in a primary purification train up to two distillation columns while providing one or more recycle streams to said reactor;
and
(d) removing iodides from said liquid acetic acid product stream and simultaneously controlling the Color Value of said acetic acid stream such that the product has an iodide content of less than about 10 ppb iodide and a Color Value of less than about 10, wherein said step of removing iodides and controlling the Color Value of said product stream consists essentially of contacting said liquid acetic acid product stream with a silver or a mercury exchanged ion exchange substrate at a temperature of at least about 50° C. wherein at least one percent of the active sites of said resin have been converted to the silver or mercury form.

2 more elements

A continuous process for producing acetic acid comprising:

(a) reacting methanol with a carbon monoxide feedstock in a carbonylation reactor holding a catalytic reaction medium while maintaining in said reaction medium during the course of said reaction at least a finite concentration of from about 0.1 weight percent up to less than 14 weight percent of water together with (i) a salt soluble in the reaction medium at the reaction temperature in an amount operative to maintain a concentration of ionic iodide in the range of from about 2 to about 20 weight percent effective as a catalyst stabilizer and co-promoter, (ii) from about 1 to 20 weight percent methyl iodide, (iii) from about 0.5 to about 30 weight percent methyl acetate;
(iv) a rhodium catalyst, and (v) acetic acid;
(b) withdrawing a stream of said reaction medium from said reactor and vaporizing a portion of said withdrawn medium in a flashing step;
(c) distilling the flashed vapor to form a liquid acetic acid product stream utilizing in a primary purification train up to two distillation columns while providing one or more recycle streams to said reactor;
and
(d) removing iodides from said liquid acetic acid product stream such that the product has an iodide content of less than about 10 ppb iodide, wherein said step of removing iodides from the acetic acid product stream is selected from the group consisting of (i) contacting said liquid acetic acid product stream with an anionic ion exchange resin at a temperature of at least about 100° C. followed by contacting said liquid acetic acid product stream with a silver or mercury exchanged ion exchange substrate wherein at least 1 percent of the active sites of said resin have been converted to the silver or mercury form or (ii) contacting said liquid acetic acid product stream with a silver or a mercury exchanged ion exchange substrate at a temperature of at least about 50° C. wherein at least one percent of the active sites of said resin have been converted to the silver or mercury form, and further comprising controlling the level of aldehyde impurities in said product stream by removing aldehydes from said recycle stream.

3 more elements

A continuous process for producing acetic acid comprising:

(a) reacting methanol with a carbon monoxide feedatock in a carbonylation reactor holding a catalytic reaction medium while maintaining in said reaction medium during the course of said reaction at least a finite concentration of from about 0.1 weight percent up to less than 14 weight percent of water together with (i) a salt soluble in the reaction medium at the reaction temperature in an amount operative to maintain a concentration of ionic iodide in the range of from about 2 to about 20 weight percent effective as a catalyst stabilizer and co-promoter, (ii) from about 1 to 20 weight percent methyl iodide, (iii) from about 0.5 to about 30 weight percent methyl acetate;
(iv) a rhodium catalyst, and (v) acetic acid;
(b) withdrawing a stream of said reaction medium from said reactor and vaporizing a portion of said withdrawn medium in a flashing step;
(c) distilling the flashed vapor to form a liquid acetic acid product stream utilizing in a primary purification train up to two distillation columns while providing one or more recycle streams to said reactor;
and
(d) removing iodides from said liquid acetic acid product stream such that the product has an iodide content of less than about 10 ppb iodide, wherein said step of removing iodides from the acetic acid product stream is selected from the group consisting of (i) contacting said liquid acetic acid product stream with an anionic ion exchange resin at a temperature of at least about 100° C. followed by contacting said liquid acetic acid product stream with a silver or mercury exchanged ion exchange substrate wherein at least 1 percent of the active sites of said resin have been converted to the silver or mercury form or (ii) contacting said liquid acetic acid product stream with a silver or a mercury exchanged ion exchange substrate at a temperature of at least about 50° C. wherein at least one percent of the active sites of said resin have been converted to the silver or mercury form, and further comprising controlling the level of aldehyde impurities in said product stream by maintaining in said reactor a methyl iodide concentration of about 5 weight percent or less.

3 more elements

A continuous process for producing acetic acid comprising:

(a) reacting methanol with a carbon monoxide feedstock in a carbonylation reactor holding a catalytic reaction medium while maintaining in said reaction medium during the course of said reaction at least a finite concentration of from about 0.1 weight percent up to less than 14 weight percent of water together with (i) a salt soluble in the reaction medium at the reaction temperature in an amount operative to maintain a concentration of ionic iodide in the range of from about 2 to about 20 weight percent effective as a catalyst stabilizer and co-promoter, (ii) from about 1 to 20 weight percent methyl iodide, (iii) from about 0.5 to about 30 weight percent methyl acetate;
(iv) a rhodium catalyst, and (v) acetic acid;
(b) withdrawing a stream of said reaction medium from said reactor and vaporizing a portion of said withdrawn medium in a flashing step;
(c) distilling the flashed vapor to form a liquid acetic acid product stream utilizing up to two distillation columns while providing one or more recycle streams to said reactor;
(d) controlling the level of iodide impurities in said product stream by maintaining a hydrogen partial pressure of less than about 6 psia in the reactor at a total pressure of from about 15 to 40 atmospheres in the reactor;
and
(e) removing iodides from said liquid acetic acid product stream such that the product has an iodide content of less than about 10 ppm iodide by contacting said liquid acetic acid product stream with a silver or mercury exchanged ion exchanged substrate at a temperature of the product stream of greater than about 50° C., and wherein said product stream contains organic iodide with an aliphatic chain length of C10 or greater.

4 more elements

Dependencies are inferred from the claim text.