SK117595A3 - Carboxylic acid isomerisation method - Google Patents

Abstract

A method for isomerising carboxylic acids and particularly branched acids into the corresponding straight acids. In particular, the method is for isomerising at least one branched saturated carboxylic acid by heating it in the presence of an effective amount of an iridium catalyst and an iodinated or brominated promoter, the promoter:Ir molar ratio being from 0.1 : 1 to 20 : 1. The method is particularly suitable for upgrading methyl-glutaric and ethyl-succinic acids into adipic acid.

Description

A method for isomerizing carboxylic acids, in particular branched acids, to obtain the corresponding unbranched acids is described. the isomerization of the at least one saturated branched acid by heating is carried out in the presence of an effective amount of an iridium catalyst and in the presence of a promoter containing iodine or bromine, wherein the molar ratio promoter / iridium ranges from 0.1 / 1 to 20/1. In particular, this method allows the use of methylglutaric and ethylsuccinic acids in the production of adipic acid.

and

Process for isomerization of carboxylic acids

Technical field

The invention relates to a process for the isomerization of carboxylic acids, in particular saturated branched carboxylic acids, to give the corresponding linear acids.

BACKGROUND OF THE INVENTION

The hydroxycarbonylation of pentenoic acids in the production of adipic acid always results in the formation of more or less branched dicarboxylic acids as by-products of this reaction.

The utilization of these branched dicarboxylic acids thus represents a considerable problem to be solved in the context of the industrial process for the production of adipic acid by hydroxycarbonylation of pentenoic acids.

EP-A-0,374,687 discloses a process for isomerizing saturated carboxylic acids by heating with carbon monoxide under pressure in the presence of a rhodium catalyst and a promoter containing iodine or bromine.

SUMMARY OF THE INVENTION

The invention is characterized by the use of iridium, a catalyst that differs from the catalyst previously described for this reaction.

In particular, the present invention provides a method for isomerizing at least one saturated branched carboxylic acid by heating, wherein the isomerization is carried out in the presence of an effective amount of an iridium catalyst and a promoter containing iodine or bromine, wherein the molar ratio promoter / iridium is in ranging from 0.1 / 1 to 20/1.

Among the saturated branched carboxylic acids, the most preferred branched carboxylic acids are branched diyl carboxylic acids, economically, taking into account the large amounts thereof formed during the hydroxycarbonylation of pentenoic acids in the production of adipic acid.

More specifically, the acids that may be considered are 2-methylglutaric acid, 2-ethylsuccinic acid and mixtures thereof and / or mixtures thereof with other carboxylic acids or lactones formed concurrently with these acids, such as adipic acid, pentenoic acids, valeric acid and gamma-valerolactone.

In said mixture, compounds other than 2-methylglutaric acid and 2-ethylsuccinic acid may represent up to 50% by weight, based on the total weight of the starting mixture.

Various sources of iridium can be used to obtain the iridium catalyst required in the process of the invention.

Examples of such sources include:

iridium metal; IrO; Ir O;

23

IrCl; IrCl * 3 H O;

32

IrBr; IrBr. 3 H O;

32

Irl;

Ir _and / CO / ₄ Cl ₂ ; Ir ₂ / CO / ₄ I ₂ ;

Ir ₂ (CO) _a ; Ir ₄ / CO / _{x 2} ;

Ir / C 0 / [P / C _and H _e / _{3], and} I;

Ir / CO [P / C ₆ H _s / ₃ ] ₂ Cl;

Ir [P / D _E / _{3], and} I;

HIr [P / C _p H _e / _{3] 3} / CO /;

Ir / acac // CO / ₂ ;

[IrCl / cod / J ₂ ;

/ acac = acetylacetonate; cod = 1,5 cyclooctadiene /.

Particularly preferred iridium catalysts are, for example: [IrCl / cod] ₂ , Ir ₄ / CO / _{T 2} and Ir / acac / CO ₂ .

The amount of catalyst used can vary within wide limits. / ·

In general, the amount, expressed in moles of iridium metal per liter of reaction mixture, ranging from 10 ^-4 to 10 ^{x x} , gives satisfactory results. Smaller amounts can be used, but it can be seen that the reaction rate is low. Larger quantities have no disadvantages other than economic.

Preferably, the concentration of iridium in the reaction mixture ranges from 5 x 10 ^-4 to 5 x 10 ^-2 mol / liter.

A promoter containing iodine or bromine is to be understood in the context of the process of the invention hydrogen iodide, hydrogen bromide and organic iodine or brominated compounds which are optionally capable of generating hydrogen iodide or hydrogen bromide under the reaction conditions; these organic iodine and bromine compounds are especially alkyl iodides or alkyl bromides having 1 to 10 carbon atoms, with methyl iodide and methyl bromide being preferred.

The preferred promoter / iridium molar ratio is in the range of 1/1 to 10/1.

The reaction is carried out in the liquid phase. The operating temperature is generally in the range of 120 ° C to 300 ° C and preferably in the range of 150 ° C to 250 ° C.

Although isomerization by the method of the invention can be carried out in the absence of carbon monoxide, it is preferable to work in the presence of carbon monoxide.

Thus, the total pressure at the reaction temperature can be varied within a wide range. The carbon monoxide partial pressure measured at 25 ° C is generally from 50 kPa to 10,000 kPa and preferably in the range from 100 kPa to 8,000 kPa.

The carbon monoxide used may be substantially pure carbon monoxide or may be of commercial grade carbon monoxide.

The isomerization reaction of saturated branched carboxylic acids is carried out either directly in the respective acid as in the reaction medium or in the solvent medium.

Particularly suitable as solvents are saturated or unsaturated aliphatic or aromatic carboxylic acids containing up to 20 carbon atoms, provided that they are liquid under the reaction conditions. Examples of such carboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, adipic acid, pentenoic acids, benzoic acid, and phenylacetic acid.

Other solvent groups may also be used, in particular saturated aliphatic or cycloaliphatic hydrocarbons and their chlorinated derivatives, provided that they are liquid under the reaction conditions. Examples of such solvents include benzene, toluene, chlorobenzene, dichloromethane, hexane and cyclohexane.

Mixtures of solvents may also be used.

If a solvent is present in the reaction mixture, it represents, for example, a volume of from 10 to 99 vol%, based on the total volume of the reaction mixture and preferably a volume of from 30 to 90 vol%.

Very often water is present in the reaction mixture. It is generally from 0 to 20% by weight of the reaction mixture and preferably from 0 to 10% by weight.

When the isomerization reaction is carried out in a solvent, a preferred variant consists in working in a mixture of water and a water-miscible solvent such as water / acetic acid. In this case, the amounts of the water / solvent mixture miscible with the water in the reaction mixture are those given above for the solvent alone.

The isomerization process according to the invention makes it possible, in particular, to use saturated branched dicarboxylic acids, which are obtained in larger or smaller amounts of the gesticular hydroxycarbonylation of pentenoic acids. This makes it possible to obtain a higher overall yield of the process of producing adipic acid from butadiene via pentenoic acids when adipic acid is one of the starting materials in the production of polyamides 6-6.

The final reaction mixture is worked up by some standard chemistry method to separate the individual compounds formed and the unreacted branched acids, allowing them to undergo repeated isomerization.

The process according to the invention can be carried out continuously or discontinuously. When carried out in a continuous form, the relative proportions of the reactants, catalyst, promoter and solvent can be determined by the person skilled in the art at optimum values, while in a batch process, these different ratios generally vary in accordance with the progressive conversion of the reactants.

The following Examples illustrate the invention.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

The following components are sequentially placed in a 125 ml autoclave pre-flushed with argon:

[IrCl / cod] ₂ 0.84 mmol hydrogen iodide / in aqueous solution with a concentration of 57% by weight. / 1.2 mmol 2-methylglutaric acid 39 mmol

acetic acid 40 ml

The autoclave is sealed, placed in a mixing furnace and coupled to a pressurized carbon monoxide feed. The carbon monoxide is added under a pressure of 500 kPa at 25 c and everything is then heated to 230 C. The pressure at this temperature is set at 2500 kPa using carbon monoxide / corresponding to a carbon monoxide partial pressure of 17.00 KPa measured at 25 ° C. and this pressure is maintained for 5 hours at 230 ° C.

The autoclave is first cooled and then degassed and the reaction mixture is analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC).

The following results are obtained:

conversion rate

2-methylglutaric acid 18% molar yield (CY) of adipic acid, based on converted 2-methylglutaric acid 37%

CY 2-ethylsuccinic acid 6%

CY gamma-valerolactone 6%

CY of 3-pentenoic acid 10%

CY 2-methylbutyric acid 26%

CY valeric acid 16%

Example 2

Example 1 was repeated under the same conditions and with the same amount of the same reactants, but using 2.5 mmol of hydrogen iodide and 0.42 mmol of [IrCl / cod /] _a .

The following results are obtained:

DC of 2-methylglutaric acid 36%

CY adipic acid 28%

Example 3 / ·

Example 1 was repeated under the same conditions and with the same amount of the same reactants, but using 2.5 mmol of hydrogen iodide and operating at 200 ° C.

The following results are obtained:

DC of 2-methylglutaric acid 13%

CY adipic acid 30%

Example 4

Example 3 is repeated under the same conditions and with the same amount of the same reactants, but without attaching the autoclave to the carbon monoxide source.

The following results are obtained:

DC of 2-methylglutaric acid 60%

CY adipic acid 11%

It should be noted that a large amount of monocarboxylic acids containing 5 carbon atoms (especially valeric and methylbutyric acids) is obtained.

Example 5

In a 50 ml glass vial, flushed with argon beforehand, the following components are sequentially placed:

[IrCl (cod)] __ 0.21 mmol hydrogen iodide / in an aqueous solution at a concentration of 57% (2-methylglutaric acid)

0.54 mmol mmol

The glass ampoule was placed in a 125 ml autoclave previously flushed with argon. The autoclave is closed, placed in an oven equipped with stirring and connected to a carbon monoxide feed at pressure. The carbon monoxide is added to a pressure of 500 kPa at 25 ° C and then heated to 230 ° C. The pressure at this temperature is set to 10,000 kPa of carbon monoxide / corresponding to a partial pressure of 5,900 kPa of carbon monoxide measured at 25 ° C. and this pressure is maintained for 2 hours at 230 ° C.

The autoclave is first cooled and degassed and the reaction mixture is analyzed by GC and HPLC.

The following results are obtained:

DC of 2-methylglutaric acid 20%

CY adipic acid 37%

Example 6

Example 5 is repeated under the same conditions and with the same amount of the same reactants, but operating at a carbon monoxide pressure of 2500 kPa at 230 ° C instead of 10,000 kPa.

The following results are obtained:

DC of 2-methylglutaric acid 39%

CY adipic acid 35%

Example 7

Example 5 is repeated under the same conditions and with the same amount of the same reactants, but operating at a carbon monoxide pressure of 2500 kPa at 230 ° C instead of 10,000 kPa and a reaction time of 30 minutes at this temperature instead of 2 hours.

/ ·

The following results are obtained:

DC of 2-methylglutaric acid 9%

CY adipic acid 52%

Example 8

Example 5 is repeated under the same conditions and with the same amount of the same reactants, but working under

pressure of carbon monoxide 1000 kPa at 230 C instead at 10,000 kPa. The following results are obtained: DC of 2-methylglutaric acid 62 % CY of adipic acid 20 %

Example 9

Example 5 is repeated under the same conditions and with the same amount of the same reactants, but operating at 200 ° C instead of 230 ° C.

The following results are obtained:

DC of 2-methylglutaric acid

CY adipic acid%

Example 10

Example 6 is repeated under the same conditions and with the same amount of the same reactants, but operating at 200 ° C instead of 230 ° C.

The following results are obtained:

/.

DC of 2-methylglutaric acid 6%

CY adipic acid 73%

Example 11

Example 8 is repeated under the same conditions and with the same amount of the same reactants but operating at 200 ° C instead of 230 ° C.

The following results are obtained:

DC of 2-methylglutaric acid 6%

CY adipic acid 83%

Example 12

Example 6 was repeated under the same conditions and with the same amount of the same reactants, but additionally with the addition of 7.25 mmol water.

The following results are obtained:

DC of 2-methylglutaric acid 15%

CY adipic acid 41%

Example 13

Example 5 was repeated under the same conditions and with the same amount of the same reactants, but with the substitution of hydrogen for 0.54 mmol of hydrogen bromide in an aqueous solution at a concentration of 47% by weight.

The following results are obtained:

DC of 2-methylglutaric acid

CY of adipic acid / ·%

%

Example 14

Example 6 was repeated under the same conditions and with the same amount of the same reactants, but replacing the hydrogen iodide with 0.54 mmol of hydrogen bromide in an aqueous solution at a concentration of 47% by weight.

The following results are obtained:

DC of 2-methylglutaric acid 17%

CY adipic acid 25%

Example 15

Example 8 was repeated under the same conditions and with the same amount of the same reactants, but replacing the hydrogen iodide with 0.54 mmol hydrogen bromide in an aqueous solution at a concentration of 47% by weight.

The following results are obtained:

DC of 2-methylglutaric acid 24%

CY adipic acid 18%

Example 16

In a 50 ml glass vial pre-flushed with argon, the following components are sequentially placed:

[IrCl / cod] 0.21 mmol hydrogen iodide / in aqueous solution with concentration 57% w / 0.30 mmol 2-ethylsuccinic acid / 10 mmol acetic acid 10 ml

The procedure is carried out as in Example 5, at a carbon monoxide pressure of 2500 kPa at operating temperature and maintaining the experiment at 230 ° C for 5 hours.

The following results are obtained:

DC of 2-ethylsuccinic acid

CY of adipic acid

CY of 2-methylglutaric acid%

%%

Industrial usability

The process according to the invention makes it possible to economize the production of adipic acid by utilizing branched dicarboxylic acids, which are formed as by-products in the hydroxycarbonylation of pentenoic acids. This process, feasible continuously or discontinuously, characterizes the use of an iridium catalyst and its compounds, optionally in the presence of an iodine or bromine-containing promoter, either in the form of inorganic or organic compounds. Adipic acid is an important starting material for the production of polyamides.

Claims (14)

A method for isomerizing at least one saturated branched carboxylic acid by heating, characterized in that the isomerization is carried out in the presence of an effective amount of an iridium catalyst and a promoter containing iodine or bromine, wherein the molar ratio promoter / iridium is in the range of 0.1 / 1 to 1 do 20/1. Process according to claim 1, characterized in that the saturated branched carboxylic acid used is selected from the group consisting of 2-methylglutaric acid, 2-ethylsuccinic acid or mixtures thereof and / or mixtures with other carboxylic acids or lactones formed simultaneously with these acids, such as adipic acid, pentenoic acids, valeric acid and gamma-valerolactone. Process according to claim 2, characterized in that in the mixture used, compounds other than 2-methylglutaric acid and 2-methylsuccinic acid represent at most 50% by weight, based on the total weight of the starting mixture. Process according to any one of claims 1 to 3, characterized in that the iridium catalyst used is selected from the group consisting of iridium metal; IrO Ir 0; 2 ⁹ 23 IrCl; IrCl. 3 H 0; 3 32 IrBr; IrBr. 3 H 0; 3 32 Irl; Ir ₂ / C0 / ₄ Cl_ _! ; Ir ^ / CO / ^ I ^; Ir ₂ / CO / _e ; Ir ₄ / CO / _{i 2} ; Ir / C 0 / [P / C _p H _e / _{3], and} I; Ir / C 0 [L / C _p H _e / _{3] Cl2;} Ir [P / C _p H _e / _{3], and} I; HIr [P / C _e H _s / ₃ ] ₃ (CO); Ir / acac / y c o / ^; [IrCl / cod / J _o . Process according to one of Claims 1 to 4, characterized in that the amount of catalyst, expressed in moles of iridium metal per 1 liter of reaction mixture, is in the range of 10 ^-4 to 10 ^-1 s. preferably it is in the range of 5 x 10 ^-4 to 10 ^-2 mol / liter. A process according to any one of claims 1 to 5, wherein the promoter comprising iodine or bromine is selected from the group consisting of hydrogen iodide, hydrogen bromide and organic iodine and bromine compounds which are optionally capable of generating under reaction conditions. hydrogen iodide or hydrogen bromide. The method according to any one of claims 1 to 6, characterized in that the molar ratio promoter / iridium is in the range of 1/1 to 10/1. Process according to one of Claims 1 to 7, characterized in that the reaction is carried out in the presence of carbon monoxide, its partial pressure measured at 25 ° C. C 1 is in the range of from 50 kPa to 10,000 kPa and preferably from 100 kPa to 8000 kPa. Process according to any one of claims 1 to 8, characterized in that the reaction is carried out in the liquid phase at a temperature in the range from 100 ° C to 300 ° C and preferably in the range from 150 ° C to 250 ° C. Process according to one of Claims 1 to 9, characterized in that the isomerization reaction of the carboxylic acid is carried out in the same carboxylic acid as the liquid reaction medium. Process according to any one of claims 1 to 9, characterized in that the isomerization reaction of the saturated branched carboxylic acid is carried out in a solvent medium selected from the group consisting of saturated or unsaturated aliphatic or aromatic carboxylic acids having up to 20 carbon atoms, saturated aliphatic or cycloaliphatic hydrocarbons and their chlorinated derivatives, which are liquid under the reaction conditions. / · Process according to claim 11, characterized in that the volume of the solvent is in the range of from 10% to 99% by volume, based on the total volume of the reaction mixture, and preferably in the range of from 30% to 90% by volume. Process according to one of Claims 1 to 12, characterized in that the reaction is carried out in the presence of water. Process according to one of claims 1 to 13, characterized in that water represents 0 to 10% by weight of the reaction mixture and preferably 0 to 10% by weight.