WO1996023730A1

WO1996023730A1 - Method for preparing iridium iodides and use thereof as catalysts

Info

Publication number: WO1996023730A1
Application number: PCT/FR1996/000143
Authority: WO
Inventors: Dominique Nobel
Original assignee: Rhone-Poulenc Fiber And Resin Intermediates
Priority date: 1995-02-02
Filing date: 1996-01-29
Publication date: 1996-08-08
Also published as: FR2730225A1; FR2730225B1

Abstract

A method for preparing iridium iodides by reacting at least one iridium chloride or bromide with hydrogen iodide in a medium containing at least one carboxylic acid and/or water. The preparation of iridium iodide solutions that are particularly suitable for use as catalysts in carbonylation, isomerisation or hydroformylation reactions is also disclosed.

Description

PROCESS FOR THE PREPARATION OF IRIDIUM IODIDES AND THEIR USE AS CATALYSTS

The present invention relates to a process for the preparation of iridium iodides. It also relates to obtaining solutions of iridium iodides which can be used in particular as catalysts in carbonylation, isomerization or hydroformylation reactions.

The iridium compounds available, and more particularly available in sufficient quantities for possible industrial use, are essentially the iridium oxides, the iridium chlorides, the sodium or potassium chloro-iridates, the iridium bromides. . These compounds have drawbacks for certain catalytic applications of iridium. Thus the oxides are not sufficiently soluble in the solvents generally used for the carbonylation of pentenoic acids or their esters to adipic acid or to its esters or also for the carbonylation of methanol to acetic acid. On the other hand, the presence of chloride or bromide ions is to be avoided in an industrial process due to the corrosion that these ions generate.

Iridium tetraiodide, or more generally iridium iodides because these are generally in the form of mixtures of several of them, are suitable for the homogeneous catalysis of the carbonylation reactions indicated above. In the present text, unless otherwise stated, the term iridium iodide will include iridium tetraiodide, iridium triiodide and the various mixtures of iridium iodides.

The present invention therefore firstly consists of a process for the preparation of iridium iodide, characterized in that at least one iridium chloride or bromide is reacted with hydrogen iodide in a medium. comprising at least one carboxylic acid or water or a mixture of at least one carboxylic acid and water.

As carboxylic acid which can be used in the present process, there may be mentioned more particularly aliphatic carboxylic acids which are liquid under the reaction conditions such as acetic acid, propionic acid, butyric acids, valeric acid, pentenoic acids. . Acetic acid is the preferred carboxylic acid for this reaction. It is of course possible to use a mixture of several carboxylic acids.

The iridium chlorides and bromides used are generally commercially available in the form of mixtures of iridium trichloride and tidachloride or of tribromide and iridium tetrabromide.

Hydrogen iodide is most often used in the form of an aqueous solution (hydroiodic acid) and in particular, but not limited to a 57% by weight solution. The amount of hydrogen iodide used can vary within wide limits.

Expressed in hydrogen iodide / iridium molar ratio, it usually varies between

1 and 100 and preferably from 2 to 30.

The temperature at which the process of the invention is carried out can vary widely. It is generally between 0 ^β C and the boiling temperature of the reaction mixture, under atmospheric pressure or under pressure greater than atmospheric pressure. As an indication, we can indicate that this temperature is most often between 20 ° C and 190 ° C.

The amount of carboxylic acid and / or water used is also very variable. Generally it represents from 40% to 95% by weight of the total weight of the reaction mixture and preferably from 60% to 90%.

The duration of the reaction for preparing iridium iodide can be between a few minutes and a few days. Usually, it is between

1 hour and 48 hours without these values being limiting. The iridium iodide obtained, which is essentially iridium tetraiodide, precipitates in solid form in the reaction medium. It can be separated by any known means used in chemistry to separate a solid from a liquid, such as filtration or centrifugation.

The iridium iodide thus obtained is practically free of chloride or bromide ions, that is to say that it contains less than 0.1000% by weight of chloride or bromide ions per weight of iridium and preferably less than 0.0500%.

This iridium iodide thus prepared is preferably dissolved in order to be used as a carbonylation catalyst. This dissolution is carried out by bringing said iridium iodide, generally with stirring, into contact with carbon monoxide in the presence of water. The water is present in molar amount at least equal to the molar amount of the iridium used.

Water can be the only solvent for the solution reaction. It is also possible to use at least one liquid carboxylic acid in the reaction medium under the reaction conditions. This carboxylic acid can be chosen from those which have been defined previously for the preparation of iridium iodide or be different. A carboxylic acid will advantageously be chosen which will be present in the subsequent carbonylation reaction, that is to say either the acid which will be obtained during this carbonylation, such as for example acetic acid in the carbonylation of methanol, adipic acid and / or methylglutaric acid and or ethylsuccinic acid and / or valeric acid in the carbonylation of pentenoic acids, or also the acid subjected to the carbonylation reaction, such as for example pentenoic acids. The amount of water or the amount of water and carboxylic acid used can vary widely. In practice, it is between 10% and 99.5% by weight of the total weight of the reaction mixture and preferably between 50% and 99%.

Although this is not essential, it is also possible to use hydrogen iodide in the operation of dissolving iridium iodide, in order to facilitate dissolution in certain cases. As for the preparation of the iridium iodide described above, the hydrogen iodide is generally used in the form of an aqueous solution (hydroiodic acid), in particular at 57% by weight. The hydrogen iodide / iridium molar ratio is generally from 0 to 20 and preferably from 0 to 10.

The absolute partial pressure of carbon monoxide measured at room temperature (20 to 25 ° C) is generally between 1 bar (0.1 MPa) and 200 bar (20 MPa).

The temperature at which the dissolution operation is carried out can vary widely. In general, as for the actual preparation of iridium iodide, it is between 0 ° C and the boiling temperature of the reaction mixture, under the pressure chosen for dissolution. As an indication, we can indicate that this temperature is most often between 50 ° C and 200 ° C.

The duration of the reaction for dissolving iridium iodide can be between a few minutes and a few days. Usually, it is between 1 hour and 48 hours without these values being limiting.

A variant of the process of the invention consists in directly preparing a solution of iridium iodide by carrying out in one step the two operations for the actual preparation of iridium iodide and its dissolution. In this variant, the iridium chlorides or bromides which are the starting substrates are brought into contact with hydrogen iodide in a medium comprising water or a mixture of water and at least one acid. carboxylic, in the presence of carbon monoxide.

The operating conditions of this variant are those which have been described above for the operation for dissolving iridium iodide.

The iridium iodide solution obtained in one step according to this variant comprises chloride or bromide ions, the presence of which can be considered to be troublesome in the implementation of certain processes, in particular on an industrial scale. It may therefore be useful to remove some or all of these ions, for example by passing the solution over an ion exchange resin. As examples of such resins, mention may be made of strongly basic resins, generally containing quaternary ammonium functions, such as the benzyltrimethylammonium function. It is possible, for example, to use the resins sold under the brand AMBERLYST 26 (OH) E. Another object of the invention is the use of solutions of iridium iodide, prepared according to one or other of the variants of the process, as catalyst.

The solution can first of all be used as it is, optionally after adding one or more cocatalysts or after changing the solvent in order to better adapt it to the envisaged reaction, for catalysis reactions in homogeneous phase.

It can also be used to prepare a supported solid catalyst by applying conventional methods. The solid iridium iodide obtained in the first step of one of the process variants can also be used directly as a catalyst.

However, the iridium iodide solution will preferably be used as a catalyst or part of a catalytic system to carry out reactions in homogeneous phase.

These reactions are more precisely carbonylation, hydroformylation and isomerization reactions.

Carbonylation reactions in the liquid phase in the presence of carbon monoxide more particularly make it possible to obtain carboxylic acids and / or anhydrides of carboxylic acids.

The reagents used for the carbonylation or isomerization reactions are generally chosen from alcohols such as alkanols having 1 to 10 carbon atoms or aicenols having 3 to 10 carbon atoms, ethers having 2 to 20 carbon atoms. carbon, unsaturated carboxylic acids having 3 to 10 carbon atoms, esters of carboxylic acids having 2 to 20 carbon atoms, olefins or diolefins such as butadiene. The iridium iodide solutions thus prepared are particularly particularly suitable for the carbonylation of methanol to acetic acid, as described in particular in patents EP-A-0 618 184 and EP-A-0 618 183 or hydroxycarbonylation of pentenoic acids as described in patent EP-A-0 511 126 or in the carbonylation of allylic butenols as described in patent EP-A-0 612 713 or in the hydroxycarbonylation of lactones as described in patent EP-A-0 612 711 or to the isomerization of carboxylic acids, in particular branched dicarboxylic acids, as described in patent FR-A-2 703 045.

The catalytic system used for the carbonylation reactions may comprise, in addition to the iridium iodide prepared according to the invention, at least one iodized or bromine promoter, such as hydrogen iodide or alkyl iodides which can liberate in situ hydrogen iodide or hydrogen bromide or alkyl bromides. Iodine promoters are generally preferred. However, the iridium iodide generating in situ hydrogen iodide, the addition of promoter is not always necessary. Generally, the carbonylation is carried out at a temperature of 50 ° C to 300 ° C and under a carbon monoxide pressure of 5 to 200 bar in temperature.

The carbonylation reaction is generally carried out in the presence of a solvent which can be more particularly, but not limited to, chosen from the compounds used or the compounds produced during the carbonylation.

If necessary, the solution of the iridium iodide can be carried out simultaneously, as described above, and the carbonylation reaction, when the substrate which is to be carbonylated is used for the solution. This is particularly the case when the iridium iodide is dissolved in a medium comprising at least one pentenoic acid.

The following examples illustrate the invention.

EXAMPLE 1 - Synthesis of iridium iodide. Charged into a glass reactor of 50 cm ^:

- 0.27 g of iridium trichloride (at 53% by weight of Ir)

- 2.0 g of an aqueous solution of hydroiodic acid at 57% by weight - 10 g of acetic acid.

The mixture is brought to reflux for 26 hours. By cooling, the precipitation of a black powder (iridium iodide) is observed. The powder is filtered through a sintered glass filter of porosity 4 and dried. 0.48 g of iridium iodide is thus obtained (78% yield) which has a residual chlorine content of less than 0.0200%.

EXAMPLE 2 Preparation of a solution of iridium iodide in acetic acid The following are loaded into an autoclave of 1.5 liters: • aqueous solution of Hl at 57% by weight: 90 g - acetic acid: 911 g

The mixture is stirred at 1500 rpm and 105 g of iridium iodide (having an Ir content of 28.2%) are added slowly so as to obtain a suspension of homogeneous appearance. A pressure of 5 bar is established with carbon monoxide and the mixture is heated at 150 ° C for 5 h. After cooling, the solution is filtered on a sintered glass filter of porosity 4. We obtain 1075 g of a red solution titrating 2.7% in iridium. This solution is stable over time (several months) and handling requires no special precautions. EXAMPLE 3 Preparation of a solution of iridium iodide in 3-pentenoic acid The following are loaded into a glass tube:

- Iridium iodide prepared in Example 1: 72.1 mg

- water: 2.27 g - 3-pentenoic acid: 25.2 g

A pressure of 5 bar is established with carbon monoxide and the mixture is heated to 185 ° C. in 30 min. The pressure is then adjusted to 20 bar with carbon monoxide and maintained at 185 ° C for a further 35 min. A homogeneous and stable straw-yellow solution is obtained.

EXAMPLE 4 Preparation of a solution of iridium iodide in 3-pentenoic acid e hvdroxycarbonylation of 3-pentenoic acid The following are charged in a glass ampoule: - iridium iodide prepared in Example 1: 72.1 mg

- water: 2.27 g

- 3-pentenoic acid: 25.2 g

The ampoule is introduced into an autoclave which is purged with carbon monoxide.

A pressure of 5 bar is established with carbon monoxide and the mixture is heated to 185 ° C. in 30 min. The pressure is then adjusted to 20 bar with carbon monoxide and maintained at 185 ° C for a further 1 h 30 min. A carbonylation rate of pentenoic acid of 5 moles per liter of reaction mixture and per hour is measured.

Adipic acid is obtained with a yield of 97% expressed as a molar ratio of adipic acid / adipic acid + saturated acids with 5 carbon atoms.

The linearity expressed as a molar ratio of adipic acid / sum of the diacids with 6 carbon atoms is 80%.

EXAMPLE 5 - Hydroxycarbonylation of methyl acetate One loads in a glass ampoule:

- Iridium iodide solution prepared in Example 2: 1.72 g

- methyl acetate: 2.90 g - methyl iodide: 1.16 g

- water: 2.27 g

- acetic acid: 19.2 g The ampoule is introduced into an autoclave which is purged with carbon monoxide.

A pressure of 10 bar is established with carbon monoxide and the temperature is brought to 190 ° C. When this temperature is reached, communication is established with a carbon monoxide reserve provided with a pressure regulator making it possible to maintain the total pressure at 30 bar. The carbonylation rate of methyl acetate to acetic acid is 7.3 moles per liter of reaction mixture and per hour.

Claims

1) - Process for the preparation of iridium iodide, characterized in that at least one iπdium chloride or bromide is reacted with hydrogen iodide in a medium comprising at least one carboxylic acid or water or a mixture of at least one carboxylic acid and water

2) - Process according to claim 1, characterized in that the carboxylic acid used is chosen from carboxylic acids with liquid phatics under the reaction conditions such as acetic acid, propionic acid, butyπques acids, vaiéπque acid, pentenoic acids and is preferably acetic acid

3) - Method according to one of claims 1 or 2, characterized in that the amount of carboxylic acid and / or water used represents from 40% to 95% by weight of the total weight of the reaction mixture and preferably 60% to 90%.

4) - Method according to one of claims 1 to 3, characterized in that the quantity of hydrogen iodide used, expπmée in molar ratio hydrogen iodide / indium, vane between 1 and 100 and preferably of 2 to 30

5) - Method according to one of claims 1 to 4, characterized in that the temperature to which it is conducted is between 0 ° C and the boiling temperature of the reaction mixture, under atmospheric pressure or under pressure greater than l atmospheric pressure and is preferably between 20 ° C and 190 ° C

6) - Method according to one of claims 1 to 5, caractéπsé in that the indium iodide obtained which precipitates in solid form in the reaction medium is separated by any known means such as filtration or ceπtπfugation

7) - Method according to claim 6, characterized in that the separated indium iodide is dissolved by bringing said indium iodide into contact with carbon monoxide in the presence of water 8) - Process for the preparation of an indium iodide solution, characterized in that at least one indium chloride or bromide is brought into contact with hydrogen iodide in a medium comprising l water or a mixture of water and at least one carboxylic acid, in the presence of carbon monoxide, the quantity of hydrogen iodide used, expressed in molar ratio hydrogen iodide / iπdium, ranging between 1 and 100 and preferably between 2 and 30.

9) - Method according to one of claims 7 or 8, characterized in that the water is present in molar amount at least equal to the molar amount of iπdium used

10) - Method according to one of claims 7 to 9, caractéπsé in that water constitutes the only solvent for the solution reaction.

11) - Method according to one of claims 7 to 9, characterized in that at least one liquid carboxylic acid is used in the reaction medium under the reaction conditions, such as acetic acid, propionic acid, butyric acids, valéπque acid, adipic acid, methylglutanic acid, ethylsuccinic acid, pentenoic acids and mixtures of several of these acids

12) - Method according to one of claims 7 to 11, characterized in that the amount of water or the amount of water and carboxylic acid used is between 10% and 99.5% by weight of the total weight of the reaction mixture and preferably between 50% and 99%

13) - Method according to one of claims 7 and 9 to 12, caractéπsé in that one implements hydrogen iodide

14) - Method according to one of claims 7 and 9 to 13, caractéπsé in that the molar ratio hydrogen iodide / iπdium is from 0 to 20 and preferably from 0 to 10

15) - Method according to one of claims 7 to 14, caractéπsé in that the partial pressure of carbon monoxide measured at room temperature is between 1 bar (0.1 MPa) and 200 bar (20 MPa) and in that the temperature at which the dissolution operation is carried out is between 0 ° C and the boiling temperature of the reaction mixture, under the pressure chosen for the dissolution and is preferably between 50 ° C and 200 ° C 16) - Use of the iridium iodide prepared according to one of claims 1 to 15, characterized in that the iridium iodide solution is used as it is, optionally after addition of one or more cocatalysts or after changing the solvent in order to better adapt it to the envisaged reaction, for homogeneous phase catalysis reactions such as carbonylation, hydroformylation and isomerization reactions.

17) - Use according to claim 16, characterized in that the iridium iodide solution is used for the carbonylation or isomerization reactions of compounds chosen from alcohols having 1 to 10 carbon atoms or alkenols having 3 to 10 carbon atoms, ethers having 2 to 20 carbon atoms, unsaturated carboxylic acids having 3 to 10 carbon atoms, esters of carboxylic acids having 2 to 20 carbon atoms, olefins or diolefins.

18) - Use according to one of claims 16 or 17, characterized in that the iridium iodide solution is used for the carbonylation reaction of methanol to acetic acid.

19) - Use according to one of claims 16 or 17, characterized in that the iridium iodide solution is used for the hydroxycarbonylation reaction of pentenoic acids, for the carbonylation reaction of allyl butenols, for the lactone hydroxycarbonylation reaction or for the isomerization reaction of branched dicarboxylic acids.