JP2005336105A - Method for producing carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce by-products generated as a by-product while maintaining high productivity of a carboxylic acid or to produce a rhodium catalyst in producing a carboxylic acid by carbonylation of an alcohol and / or a reactive derivative thereof. It is an object of the present invention to provide a novel method for producing a carboxylic acid that stabilizes water.
SOLUTION: A carboxylic acid is produced by reacting an alcohol and / or a reactive derivative thereof with carbon monoxide in the presence of a rhodium catalyst, lithium iodide, an alkyl halide, and a finite amount of water (particularly under low moisture). A method for producing a carboxylic acid, characterized by reacting in the presence of at least one element selected from Zn, Sn, Ge, and Pb or a compound containing the element.
[Selection figure] None

Description

  The present invention relates to a novel process for producing carboxylic acids by carbonylation of alcohols and / or reactive derivatives thereof in the presence of a rhodium catalyst. More specifically, the present invention relates to a novel method for producing a carboxylic acid that reduces the by-product by-product or stabilizes the rhodium catalyst while maintaining high productivity of the carboxylic acid when producing the carboxylic acid by carbonylation. is there.

  A carbonylation method from an alcohol and / or a reactive derivative thereof in the presence of a rhodium catalyst is already known, and the production method of the carboxylic acid is the most industrially superior method. Improvement of reaction conditions, etc. has been studied, and by adding iodide salts, etc., and reacting under conditions of water concentration in the reaction solution lower than conventional conditions, productivity is high and energy in the purification process is increased. A method for producing carboxylic acid with low consumption is disclosed (for example, see Patent Document 1 and Patent Document 2). However, it is known that by-product gases such as methane, hydrogen, and carbon dioxide are generated in these carbonylation reactions (see, for example, Patent Document 2). Corrosion metals such as iron, chromium, molybdenum, and nickel are mixed in due to corrosion of the equipment materials, and these promote side reactions (water gas shift reaction, methane, acetaldehyde, propionic acid, etc.). It is described. In particular, the by-product of methane not only deteriorates the usage rate of alcohol and / or its reactive derivative, carbon monoxide, which is a raw material, but also increases the total pressure during the reaction. For this reason, it becomes necessary to give the reactor a pressure resistance higher than necessary, or measures such as lowering the carbon monoxide partial pressure at the expense of productivity are required. Furthermore, when methane that has accumulated to some extent in the reaction system is discharged out of the reaction system, it is discharged with a part of the raw material, carbon monoxide, which causes a reduction in the carbon monoxide usage rate, and is a by-product of methane. It is desirable to suppress as much as possible.

  In addition, acetaldehyde is a carbonyl impurity (butyraldehyde, crotonaldehyde, 2) that deteriorates the permanganate-reducing substance test (permanganate time), which is a quality test for examining the abundance of very small reducing impurities in acetic acid. -Known as causative substances such as carbonyl compounds such as ethyl crotonaldehyde, and aldol condensates thereof) and alkyl iodides that deactivate the vinyl acetate production catalyst in the process of producing vinyl acetate from ethylene and acetic acid (for example, It is desired that the acetaldehyde concentration in the reaction solution be reduced.

Further, Patent Literature 2 is cited as a method for carbonylation of alcohol using Zn and Sn compounds. Patent Document 2, the production rate of acetic acid in the case of using a variety of iodide salt are compared, although ZnI ₂ or SnI ₂ is used as an iodide salt, despite acetate is used a large amount The production rate is very low and is not sufficiently industrially applicable.
Japanese Examined Patent Publication No. 4-69136 Japanese Patent Publication No. 7-023337 Japanese Patent Publication No. 8-011199 JP-A-7-002722 Japanese Patent Application Laid-Open No. 8-067650

  The present invention reduces by-products produced as a by-product while maintaining high productivity of carboxylic acids when producing carboxylic acids by carbonylation of alcohols and / or reactive derivatives thereof, particularly under low moisture conditions. Another object is to provide a novel method for producing a carboxylic acid that stabilizes a rhodium catalyst.

  The inventors of the present invention have completed the present invention as a result of intensive studies on an efficient method for producing a carboxylic acid by carbonylation of an alcohol and / or a reactive derivative thereof.

  That is, the present invention comprises reacting an alcohol and / or a reactive derivative thereof with carbon monoxide in the presence of a rhodium catalyst, lithium iodide, an alkyl halide, a finite amount of water (especially under low moisture) to produce a carboxylic acid. The present invention provides a method for producing a carboxylic acid characterized by reacting in the presence of at least one element selected from Zn, Sn, Ge, and Pb or a compound containing the element.

  According to the present invention, when an alcohol and / or a reactive derivative thereof is reacted with carbon monoxide to produce a carboxylic acid, the reaction is carried out in the presence of Zn element or a compound containing Zn element. By-products such as methane and acetaldehyde can be effectively suppressed while maintaining high productivity. In addition, when a corrosive metal is present in the reaction solution, the production of by-products can be suppressed particularly efficiently. Therefore, it becomes possible to improve the usage rate of the raw material alcohol and / or its reactive derivative and carbon monoxide, and in order to remove by-produced methane out of the reaction system, the reaction system is accompanied by methane. It became possible to reduce the amount of carbon monoxide that had been lost to the outside.

  Further, the present invention stabilizes the rhodium catalyst by maintaining the high productivity of the carboxylic acid by reacting in the presence of at least one element selected from Sn, Ge, and Pb or a compound containing the element. Can be manufactured.

Suitable alcohols include, for example, C _1-10 alkyl alcohols such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, C _3-10 cycloalkyl alcohols such as cyclohexanol, cyclooctanol, and phenols such as phenol. , Aralkyl alcohols such as benzyl alcohol and phenethyl alcohol, etc., and C _1-10 alkyl alcohols such as methanol, ethanol, propanol, butanol, pentanol and hexanol are preferred, and methanol is particularly preferred.

Examples of reactive derivatives of alcohol include esters such as C _2-6 alkylcarboxylic acid-C _1-6 alkyl ester such as methyl acetate and ethyl acetate, and iodide C such as methyl iodide, ethyl iodide and propyl iodide. _1-10 alkyls, halides such as bromides (such as methyl bromide and propyl bromide) and chlorides (such as methyl chloride) corresponding to these alkyl iodides, di-C such as dimethyl ether, diethyl ether, diisopropyl ether and dibutyl ether _And ethers such as _1-6 alkyl ethers.

As the rhodium catalyst, any rhodium compound that is soluble in the reaction solution can be used. Moreover, even if it is a thing with low solubility with respect to a reaction liquid, if it can produce | generate a soluble compound easily on reaction conditions, it can be used. Examples of usable rhodium compounds include [Rh (CO) ₂ Cl] ₂ , Li [Rh (CO) ₂ I ₂ ], [Rh (CO) ₂ I] ₂ , [Rh (COD) Cl] ₂ ( COD means cyclooctadiene.), RhCl ₃ , RhCl ₃ · 3H ₂ O, RhBr ₃ , RhI ₃ , rhodium (II) acetate, dicarbonylacetylacetonatodium, RhCl (CO) (PPh ₃ ) ₂ etc., but not limited to this.

  The concentration of the rhodium compound in the reaction solution is rhodium concentration, which is in the range of 50 to 5000 ppm, preferably 100 to 1500 ppm.

  The amount of lithium iodide is not particularly limited as long as it can be dissolved in the reaction solution, and is, for example, 0.1 to 30 wt%, preferably 2 to 20 wt%, and more preferably 5 to 20 wt%.

The alkyl halide is a C _1-10 , preferably C _1-6 , more preferably a C _1-4 alkyl halide, and an alkyl iodide or bromide is preferably used. More preferred is iodide, and methyl iodide is most preferred. The concentration of the alkyl halide in the reaction solution is 1 to 20 wt%, preferably 2 to 16 wt%, more preferably 5 to 16 wt%.

  Zn (zinc) to be present in the reaction solution can be selected from any zinc compound. Specific examples include zinc metal (zinc powder), zinc acetate, zinc acetate dihydrate, zinc chloride, zinc bromide, zinc iodide, zinc acetylacetonate, and the like. The amount of zinc present in the reaction solution is 10 to 5000 ppm, preferably 50 to 3000 ppm, more preferably 100 to 1500 ppm in terms of metallic zinc.

  Normally, corrosive metals are present during the carboxylic acid production process, and it has been found that corrosive metals promote the formation of by-products such as methane and acetaldehyde. There is.

  When corrosive metals are present in the reaction solution, the amount of zinc present in the reaction solution is preferably 10 to 0.01, more preferably 5 to 0.1, in terms of the total amount ratio (weight ratio) of zinc / corrosion metal. Is preferred.

  The corrosive metal is unintentionally mixed in the reaction solution except for the rhodium catalyst added as a catalyst, lithium iodide, Zn, Sn, Ge, Pb, and the one that is intended to produce carboxylic acid. This refers to a metal species that is eluted from the material of equipment used mainly in the carboxylic acid production process. Specific examples include groups IVA to VIIA of the periodic table and iron, cobalt, and nickel, and iron, nickel, chromium, molybdenum, tungsten, and manganese are particularly exemplified. The mixing amount in these reaction solutions is usually in the range of several tens to several thousand ppm.

  Sn, Ge, and Pb present in the reaction liquid include elements, oxides, hydroxides, halides, carbonates, carboxylates, etc., but they do not adversely affect the reaction and the reaction apparatus. Any shape is acceptable. Among them, it is preferable to react in the presence of Sn, for example, tin metal, tin (II) chloride, tin (IV) chloride, tin (II) oxide, tin (IV) oxide, tin (II) iodide, iodide. Tin (IV), tin acetate (II), tin acetate (IV) and the like can be mentioned, and tin iodide (II) is particularly preferable.

  The amount of at least one element selected from Sn, Ge, and Pb present in the reaction solution or the compound containing the element is 10 to 20000 ppm, preferably 10 to 10000 ppm, more preferably 10 to 5000 ppm in terms of metal.

  As a method for causing the reaction solution to contain at least one element selected from Zn, Sn, Ge, and Pb or a compound containing the element, the reaction solution may be added directly to the reactor, or in the catalyst circulation liquid to be circulated to the reactor. In addition, it may be added as it is, or may be added after dissolving in a solvent such as methanol in advance, but it is preferable to add it to a reactor after dissolving it in a solvent in advance.

  The water concentration in the reaction solution is a finite amount, that is, 15% by weight or less, preferably 10% by weight or less, more preferably 1 to 5% by weight. % Is preferably applied in the case of low moisture.

  Carbon monoxide may be used pure or may be diluted with carbon dioxide, nitrogen, argon or lower hydrocarbons. The carbon monoxide partial pressure during the reaction is usually 5 MPa-G or less, preferably 2.5 MPa-G or less, more preferably 1.5 MPa-G or less. It is known that carbon dioxide and hydrogen are generated by the reaction of water and carbon monoxide (water gas shift reaction) existing in the system during the reaction, and therefore hydrogen is present in the reaction system. If the hydrogen partial pressure becomes too high, by-products such as lower hydrocarbons such as methane are produced, and therefore it is preferable to control the hydrogen partial pressure to 0.2 MPa-G or less, preferably 0.1 MPa-G or less.

  The total pressure of the carbonylation reaction is 1 to 20 MPa-G, preferably 1 to 10 MPa-G, more preferably 1.5 to 5 MPa-G.

  The temperature of carbonylation reaction is 100-300 degreeC, Preferably it is 150-250 degreeC, More preferably, it is 150-200 degreeC.

  The present invention can be carried out by a batch method or a continuous method, and a continuous method is preferred.

  Generally, carboxylic acid is produced by the reaction of carbon monoxide with an alcohol and / or reactive derivative thereof as a raw material in a carbonylation reactor. A reaction liquid composition comprising carboxylic acid and its ester, alkyl halide, rhodium catalyst, lithium iodide, zinc and the like is withdrawn from the carbonylation reactor and introduced into the flasher. In the flasher, volatile components mainly consisting of carboxylic acid and its ester, alkyl halide and water are taken out from the upper part of the flasher, and non-volatile components mainly consisting of catalyst components are taken out from the lower part of the flasher and circulated to the reactor. Is done.

  The volatile component taken out from the upper part of the flasher can be subjected to de-low boiling, dehydration and de-high boiling treatment as necessary to obtain a product carboxylic acid (acetic acid).

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Hereinafter, Examples 1 to 5 and Comparative Examples 1 to 5 show the byproduct reduction effect in the presence of Zn. The GC analysis conditions are as follows.
Gas analysis conditions _{(H 2, CO, CO 2} , CH 4)
Column conditions: Column SHINCARBON-T (manufactured by Shinwa Kogyo Co., Ltd.)
Mesh 60/80
Length 5m
GC condition: column temperature 50 ° C. (8 min) → 10 ° C./min→260° C. (1 min)
INJ 200 ℃
DET 200 ℃
Carrier Ar
Flow rate 20ml / min
Detector TCD
Current 50mA
Temp. 200 ℃
Sample preparation method; injection volume: usually 50-100ml
Sample tube capacity 0.5ml
Quantitative calculation method Absolute calibration method
Sample adjustment Off gas

Aldehyde analysis conditions Column conditions; Column DB-1
Length 30m
GC condition: Column temperature 40 ° C (10 min) → 5 ° C / min → 70 ° C (0 min)
→ 15 ℃ / min → 280 ℃ (10min)
INJ 200 ℃
DET 200 ℃
Carrier He
Flow rate 1.5ml / min
Split ratio 1/110
Detector FID
H ₂ 50kPa-G
Air 50kPa-G
Sample preparation method; injection volume 1 μl
Internal standard (IS) mesitylene
Spl / IS 4 / 0.02 (wt / wt)
<Example 1>
10 g of methyl acetate, 30 g of methyl iodide, 4 g of water, 40 g of anhydrous lithium iodide, 1.11 g of iron (II) iodide, 1.06 g of nickel (II) iodide, 0.88 g of chromium (III) acetate, molybdenum chloride ( V) 0.57 g was mixed and acetic acid was added so that the total amount was 200 g. In an autoclave made of Hastelloy B-2 (registered trademark) with an internal volume of 500 ml, 100 g of the above mixture was charged, 0.49 g of zinc (II) iodide and 0.23 g of rhodium (III) iodide as a catalyst were added, and hydrogen After substituting the inside of the autoclave with 1 MPa-G three times, hydrogen was introduced at an atmospheric pressure of 1 atm. Thereafter, 1 MPa-G of carbon monoxide was further charged. After charging carbon monoxide, the autoclave was immersed in an oil bath heated to 187 ° C. in advance and stirred at 1000 rpm to control the autoclave to be kept at 187 ° C. After heating at a predetermined temperature for 1 hour, the autoclave was cooled with ice water for 1 hour. The pressure after cooling was 0.6 MPa-G. When the gas remaining in the autoclave was analyzed by gas chromatography (hereinafter abbreviated as GC), 350 μmol of methane and 230 μmol of acetaldehyde were detected. The concentration of various metals added in this experiment was 1000 ppm for all of iron, nickel, chromium, molybdenum, and zinc.

<Comparative Example 1>
100 g of the mixture prepared in Example 1 and 0.23 g of rhodium (III) iodide were charged into the autoclave used in Example 1 and reacted in the same manner as in Example 1 without adding only zinc (II) iodide. It was. The pressure after cooling was 0.58 MPa-G. When the gas remaining in the autoclave was analyzed by GC, 860 μmol of methane and 1,020 μmol of acetaldehyde were detected.

<Example 2>
8 g of methanol, 28 g of methyl iodide, 4 g of water, 40 g of anhydrous lithium iodide, 1.11 g of iron (II) iodide, 1.06 g of nickel (II) iodide, 0.88 g of chromium (III) acetate, molybdenum chloride (V ) 0.57 g was mixed, and acetic acid was charged so that the total amount was 200 g. 100 g of the above mixture was charged into the autoclave used in Example 1, 0.49 g of zinc (II) iodide and 0.23 g of rhodium (III) iodide as a catalyst were added. Subsequent operations were carried out in the same manner as in Example 1. After cooling, the internal pressure was 0.35 MPa-G, and the gas remaining in the autoclave was analyzed by GC. As a result, 3,500 μmol of methane was detected.

<Comparative example 2>
100 g of the mixture prepared in Example 2 and 0.23 g of rhodium (III) iodide were charged into the autoclave used in Example 1 and reacted in the same manner as in Example 1 without adding only zinc (II) iodide. It was. The pressure after cooling was 0.35 MPa-G. When the gas remaining in the autoclave was analyzed by GC, 8,200 μmol of methane was detected.

<Example 3>
4 g of methanol, 14 g of methyl iodide, 2 g of water, 20 g of anhydrous lithium iodide, 60 g of acetic acid, 0.49 g of zinc (II) iodide, and 0.23 g of rhodium (III) iodide as a catalyst were added. Subsequent operations were carried out in the same manner as in Example 1. After cooling, the internal pressure was 0.35 MPa-G, and the gas remaining in the autoclave was analyzed by GC. As a result, 800 μmol of methane was detected.

<Comparative Example 3>
The reaction was performed under the same conditions as in Example 3 except that zinc (II) iodide was not added. After cooling, the internal pressure was 0.35 MPa-G, and the gas remaining in the autoclave was analyzed by GC. As a result, 1,400 μmol of methane was detected.

<Example 4>
8 g of methanol, 28 g of methyl iodide, 16 g of water, 9 g of anhydrous lithium iodide, 1.11 g of iron (II) iodide, 1.06 g of nickel (II) iodide, 0.88 g of chromium (III) acetate, molybdenum chloride (V ) 0.57 g was mixed and acetic acid was added so that the total amount was 200 g. 100 g of the above mixture was charged into the autoclave used in Example 1, 0.49 g of zinc (II) iodide and 0.23 g of rhodium (III) iodide as a catalyst were added. Subsequent operations were carried out in the same manner as in Example 1. After cooling, the internal pressure was 0.35 MPa-G, and when the gas remaining in the autoclave was analyzed by GC, 1,700 μmol of methane was detected.

<Comparative example 4>
Without adding zinc iodide (II), 100 g of the mixture prepared in Example 4 and 0.23 g of rhodium (III) iodide as a catalyst were charged into the autoclave used in Example 1 and reacted in the same manner as in Example 1. Went. After cooling, the internal pressure was 0.36 MPa-G, and when the gas remaining in the autoclave was analyzed by GC, 4,200 μmol of methane was detected.

<Example 5>
4 g of methanol, 14 g of methyl iodide, 8 g of water, 4.5 g of anhydrous lithium iodide, 59.5 g of acetic acid, 0.49 g of zinc (II) iodide and 0.23 g of rhodium (III) iodide as a catalyst were added. Subsequent operations were carried out in the same manner as in Example 1. After cooling, the internal pressure was 0.35 MPa-G, and the gas remaining in the autoclave was analyzed by GC. As a result, 600 μmol of methane was detected.

<Comparative Example 5>
The reaction was carried out under the same conditions as in Example 5 without adding zinc (II) iodide. After cooling, the internal pressure was 0.34 MPa-G, and the gas remaining in the autoclave was analyzed by GC. As a result, methane was 1,100 μmol.

Hereinafter, Examples 6 to 8 and Comparative Example 6 show the effect of suppressing precipitation to a rhodium catalyst in the presence of Sn.

<Example 6>
Water 5.0 wt%, methyl iodide 1.7 wt%, methyl acetate 0.9 wt%, acetic acid 88.1wt%, LiI7.1wt%, rhodium 940 ppm (the RhI ₃ was used by dissolving treatment with CO / H2), It charged SnI ₂ 0.68wt% solution 300ml adjusted so that the liquid composition (about 2000ppm of SnI ₂ with 2 moles added / metal Sn conversion rhodium) in 500ml autoclave, were pasted nitrogen 3.1 MPa-G, a liquid When the time-dependent change in the rhodium concentration in the liquid at a temperature of 140 ° C. was observed, no change was observed in the rhodium concentration after 1 hour, 3 hours, and 5 hours later. That is, no precipitation of rhodium catalyst was observed.

<Example 7>
As a result of conducting the same experiment as in Example 6 except that the liquid temperature was changed to 180 ° C., no change was observed in the rhodium concentration after 1 hour, 3 hours and further 5 hours. That is, no precipitation of rhodium catalyst was observed.

<Example 8>
As a result of conducting the same experiment as in Example 6 except that the liquid temperature was changed to 200 ° C., no change was observed in the rhodium concentration after 1 hour, 3 hours and further 5 hours. That is, no precipitation of rhodium catalyst was observed.

<Comparative Example 6>
Water 5.0 wt%, methyl iodide 1.7 wt%, methyl acetate 0.9 wt%, acetic acid 88.1wt%, LiI7.1wt%, rhodium 940 ppm (the RhI ₃ was used by dissolving treatment with CO / H ₂₎ 300 ml of the liquid adjusted to the liquid composition was charged into a 500 ml autoclave, nitrogen 3.1 MPa-G was added, and the change over time in the rhodium concentration in the liquid at a liquid temperature of 140 ° C. was observed. The rhodium concentration was 590 ppm and 400 ppm after 5 hours. That is, the rhodium catalyst is considerably settled as compared with Example 6 in which SnI ₂ is present at 2 mole times rhodium.


Hereinafter, the acetic acid production rate in the presence or absence of Sn is shown in Comparative Example 7 and Example 9. The GC analysis conditions are as follows.
Reaction solution analysis conditions (methyl acetate, methanol, methyl iodide, acetic acid)
Column conditions: Column RESTEK STABILWAX-DA (made by RESTEK)
Inner diameter 0.32mm
Length 30m
GC condition: column temperature 50 ° C. (7 min) → 15 ° C./min→220° C. (20 min)
INJ 200 ℃
DET 220 ° C
SPLIT 50: 1
Carrier He
Flow rate 1.8ml / min
Detector FID
Sample preparation method; injection volume 1 μL
Quantitative calculation method Internal method
Internal standard solution Cyclohexanone
Preparation of internal standard solution Inject 100 mg of cyclohexanone into 100 g of propionitrile, and use that solution as an internal standard solution.
Sample solution After injecting 200 mg of reaction solution into 8.8 g of propionitrile for dilution, add 1 g of internal standard solution to make a sample solution.

<Comparative Example 7>
2 g of water, 60 g of acetic acid, 20 g of lithium iodide, 14 g of methyl iodide, 4 g of methanol, 0.235 g of rhodium iodide (CO1 MPa-G, H ₂ 100 kPa-G (30 ° C.) are added, and activation is performed at 187 ° C. for 60 minutes. Used after treatment; Rh concentration is 500 ppm / batch), reaction at 187 ° C, total pressure 2.5 MPa-G, CO partial pressure 1.5 MPa-G, H ₂ partial pressure 0.1 MPa-G Went. As a result of measuring the reaction solution composition after 10 minutes by GC analysis, the residual amount of raw material methanol (methyl acetate was converted back to methanol) was 47 mmol, which was 78 mmol of methanol consumption from the start of the reaction. .

<Example 9>
Furthermore, the reaction was performed in the same manner as in Comparative Example 7 except that SnI ₂ (about 1500 ppm in terms of metal Sn) having a molar amount twice the rhodium concentration was charged.
As a result of measuring the reaction solution composition after 10 minutes by GC analysis, the residual amount of raw material methanol (methyl acetate was converted back to methanol) was 40 mmol, which was 85 mmol methanol consumption from the start of the reaction, Compared with Comparative Example 7, the reaction rate was increased.

Claims (3)

In a method for producing a carboxylic acid by reacting an alcohol and / or a reactive derivative thereof with carbon monoxide in the presence of a rhodium catalyst, lithium iodide, an alkyl halide, and a finite amount of water, Zn, Sn, Ge, Pb A process for producing a carboxylic acid, comprising reacting in the presence of at least one element selected from the group consisting of: The method for producing a carboxylic acid according to claim 1, wherein the concentration of Zn element or the compound containing Zn element in the reaction solution is 10 to 5000 ppm (in terms of metallic Zn). The method for producing a carboxylic acid according to claim 1, wherein the concentration of at least one element selected from Sn, Ge, and Pb or a compound containing the element in the reaction solution is 10 to 20000 ppm (in metal conversion).