FR2845085A1 - Production of acetic acid by carbonylation of methanol catalysed by iridium in the presence of a bis-phosphonate promoter - Google Patents

Abstract

Process for obtaining acetic acid by carbonylation of methanol in the presence of an iridium catalyst, a methyl iodide co-catalyst and a bis-phosphonate promoter. Acetic acid is produced by carbonylation with CO of methanol and/or a reactive derivative in a carbonylation reactor. The reactive composition comprises an Ir catalyst, a MeI co-catalyst and a final concentration of water, acetic acid, methyl acetate and promoter. The water concentration is at or below that at which the maximum occurs in the graph of velocity of carbonylation as a function of concentration. The reaction liquid is free from a promoter comprising Ru, Os, W, Rh, Zn, Ga, Cd or In, but contains a bis-phosphonate conforming to formula (I); R1, R2, R3, R4 = H or an organic group; Y = 1 - 10C alkylene or 6 - 10C aryl(optionally substituted).

Description

R2-0 Y 0-R3

  R1.o --P / p / -O R4 IO Ig oo ([) The present invention relates to a process for the production of acetic acid and, in particular, to a process for the production of acetic acid by carbonylation in the presence of an iridium catalyst, a methyl iodide co-catalyst and a catalyst promoter. The preparation of carboxylic acids by

  iridium-catalyzed carbonylation processes is known and is described, for example, in documents GB-A-1234121, US-A-3772380, DE-A-1767150, EP-A-0616997, 10 EP-A-0618184, EP -A-0618183, EP-A-0657386 and WOA95 / 31426.

  WO-A-95/314 describes a process for the production of carboxylic acids or their esters comprising (n + 1) carbon atoms by liquid phase reaction of carbon monoxide with at least one alcohol comprising (n ) carbon atoms in the presence of a catalytic system based on an iridium compound and a halogenated cocatalyst. The process is characterized by maintaining in the reaction medium water in a volume 20 situated between more than 0 and 10%, typically between 0, 5 and 8%, preferably between 2 and 8%; ester corresponding to acetic acid and alcohol in a volume varying between 2 and 40%; and iodides in soluble form of a nature such that the atomic ratio of iodides to iridium is between more than 0 and 10, typically

  between more than 0 and 3, preferably between more than 0 and 1.5. The volume of the halogenated cocatalyst in the reaction medium is between more than 0 and 10%; typically between 0.5 and 10% and preferably between 1 and 6%. The process of document WO-A95 / 31426 is otherwise without promoter.

  Document EP-A-0643034 describes a process for the carbonylation of methanol and / or of its reactive derivatives in the presence of acetic acid, of an iridium catalyst, of methyl iodide, of at least one 5 finite concentration of water, and of a promoter chosen from ruthenium and osmium. Batch and continuous experiments are described in this one. In continuous experiments, the water concentration is also

as low as 6.8% by weight.

  EP-A-0752406 describes a process for the production of acetic acid comprising the steps of (1) continuously supplying methanol and / or one of its reactive derivatives and carbon monoxide to a carbonylation reactor which contains a Liquid reaction composition comprising an iridium carbonylation catalyst, a methyl iodide cocatalyst, a finite concentration of water, acetic acid, methyl acetate and at least one promoter; (2) bringing methanol and / or its reactive derivative into contact with carbon monoxide in the liquid reaction composition to produce acetic acid; and (3) recovering acetic acid from the liquid reaction composition, characterized in that are continuously maintained in the liquid reaction composition throughout the

  reaction (a) water at a concentration of not more than 6.5% by weight, b) methyl acetate at a concentration in the range of i to 35% by weight and (c) methyl iodide at a concentration in the range of 30 4 to 20% by weight.

  There remains a need for an improved iridium catalyzed promoter carbonylation process in which conventional metal promoters, such as ruthenium, osmium, rhenium, tungsten, zinc, gallium, cadmium, mercury and indium does

are not employed.

  The technical problem is solved by the use of a carbonylation process with an iridium-catalyzed promoter of a liquid reaction composition defined in terms of water composition and which contains a

  bis-phosphonate compound as a promoter.

  Accordingly, the present invention provides a process for the production of acetic acid by carbonylation with carbon monoxide of methanol and / or its reactive derivatives in a carbonylation reactor containing a liquid reaction composition substantially free of a selected promoter in the group consisting of ruthenium, osmium, tungsten, rhenium, zinc, gallium, cadmium, mercury and indium, said liquid reaction composition comprising an iridium carbonylation catalyst, a methyl iodide cocatalyst, a finite water concentration, acetic acid, methyl acetate, and a promoter, a process in which the water concentration is at or below that at which the maximum in graph 25 of the carbonylation rate as a function of the water concentration occurs and in which the promoter is a bis-phosphonate compound corresponding to the formula I R2_ y O-R3

1-O _- \ Q - P / \ "P / -_ O R4

It 11

    I

  wherein R1, R2, R3, and R4 independently represent a hydrogen atom or an organic functional group; Y represents an optionally substituted C1-Clo alkylene group or a C6-C1O aryl group. The present invention also provides the use of a bis-phosphonate compound as a promoter in a process for the production of acetic acid by carbonylation with carbon monoxide of methanol and / or its reactive derivatives in a carbonylation reactor containing a liquid reaction composition substantially free of a promoter selected from the group consisting of ruthenium, osmium, tungsten, rhenium, zinc, gallium, cadmium, mercury and indium, said reaction composition liquid comprising an iridium carbonylation catalyst, a methyl iodide co-catalyst, a finite concentration of water, acetic acid, methyl acetate, and a promoter, the water concentration being at or below the one at

  which the maximum in the graph of the carbonylation rate as a function of the water concentration occurs and said promoter being a bisphosphonate compound of formula (I) as defined above.

  The present invention provides many advantages

  techniques. The increased carbonylation rate at a low water concentration of the present invention can allow operation at a reduced iridium catalyst concentration while maintaining the carbonylation rate.

  The degree of production of by-products, propionic acid, methane, hydrogen and carbon dioxide

can be reduced.

  The process of the present invention is carried out in the absence of conventional promoters used in iridium-catalyzed carbonylation processes, such as ruthenium, osmium, rhenium, zinc, gallium, tungsten, cadmium, mercury and indium,

  thereby allowing reduced costs.

  The process of the present invention does not require the presence of a co-promoter such as iodides of alkali metals, iodides of alkaline earth metals, metal complexes which can form I-, salts

  can form I- or their mixtures.

  Water can be formed in situ in the liquid reaction composition, for example, by the esterification reaction between the methanol reagent and the acetic acid product. Small amounts of water can also be produced by hydrogenation of methanol to give methane and water. Water can be introduced into the carbonylation reactor at the same time or separately from the other components of the liquid reaction composition. The water can be separated from the other components of the reaction composition withdrawn from the reactor and can be recycled in controlled quantities in order to maintain the required concentration of water in the composition.

liquid reaction.

  Referring to the previously stated European patent application No. 0752406, the carbonylation reaction rate is said to increase when the water concentration in the liquid reaction composition is reduced from a concentration greater than 6.5% by weight, passes through a maximum at a water concentration which is not more than 6.5% by weight and then decreases when very low water concentrations are approached. In FIG. 8 of the above-mentioned application, the graph of the reaction speed as a function of the water concentration is plotted, which clearly shows a maximum. The concentration of water at which the carbonylation rate is maximum 10 is said to increase when the concentration of methyl acetate in the liquid reaction composition increases. The concentration of water at the maximum carbonylation rate is believed to decrease as the concentration of methyl iodide in the liquid reaction composition increases. For the purposes of the present invention, the concentration of water in the liquid reaction composition is preferably kept below 6%, preferably below 4.5% by weight. The operation at such a low water concentration in accordance with the present invention provides the advantage that the recovery of acetic acid from the reaction composition withdrawn from the carbonylation reactor is facilitated since the amount of water which has to be being separated from acetic acid is reduced; separation of water from acetic acid is a very energy-intensive part of the recovery process and the reduced water concentration results in reduced processing difficulty

and / or reduced costs.

  In the present invention, suitable reactive derivatives of methanol include methyl acetate, dimethyl ether and methyl iodide. A mix

  methanol and its reactive derivatives can be used as reactants in the process of the present invention.

  Preferably, methanol and / or methyl acetate are used as reactants. If methyl acetate or dimethyl ether are used, a water co-reagent is required to produce acetic acid. At least some of the methanol and / or its reactive derivatives will be transformed, and thus present, into methyl acetate in the liquid reaction composition by reaction with the acetic acid product or the solvent. In the

  process of the present invention, the concentration of methyl acetate in the liquid reaction composition is suitably in the range of 1 to 70% by weight, preferably 2 to 50% by weight, more preferably 5 to 40% by weight.

  In the present invention, the concentration of methyl iodide cocatalyst in the liquid reaction composition is suitably in the range of 1 to 30% by weight, preferably in the range of 1 to 20% by weight.

  One method of increasing the rate of carbonylation is to increase the concentration of methyl iodide. However, this process can lead to increased levels of corrosion. An advantage of the present invention is that high carbonylation rates at low concentrations of methyl iodide and water can be achieved while maintaining or even

reducing corrosion.

  In the present invention, the iridium carbonylation catalyst is suitably present in the liquid reaction composition at a concentration in the range of 400 to 5000 ppm measured as iridium, preferably in the range of 500 to 3000 ppm measured in iridium, most preferably, in the range of 700 to 3000 ppm measured in iridium. In the process of the present invention, the rate of the carbonylation reaction increases as the

iridium concentration increases.

  The iridium catalyst in the liquid reaction composition can comprise any compound containing iridium which is soluble in the liquid reaction composition. The iridium catalyst can be added to the liquid reaction composition for the carbonylation reaction in any suitable form which dissolves in the liquid reaction composition or is convertible into a soluble form. Examples of suitable iridium-containing compounds which can be added to the liquid reaction composition include IrCl3, IrI3, IrBr3, [Ir (CO) 2I] 2, [Ir (CO) 2C1] 2, [Ir (CO) 2Br ] 2, [Ir (CO) 2I2] H +, [Ir (CO) 2Br2] -H +, [Ir (CO) 2I41] -H +, [Ir (CH3) I3 (CO) 2] -H +, Ir4 (CO) 12, IrCl3.3H20, IrBr3.3H20, Ir4 (CO) 12, metal iridium, Ir203, IrO2, Ir (acac) (CO) 2, Ir (acac) 3, iridium acetate, [Ir30 (OAc) 6 ( H20) 3] [OAc], and hexachloroiridic acid [H2IrCl6], preferably, complexes lacking chlorine of iridium, such as acetates, oxalates and acetoketates which are soluble in one or more

  components of the carbonylation reaction such as water, alcohol and / or carboxylic acid.

  Particularly preferred is green iridium acetate which can be used in acetic acid or in an aqueous solution of acetic acid.

  In the present invention, one or more bis-phosphonate compounds of formula I:

R2-O Y O-R3

R1- - P P / - O R4

  Il 11 in which R1, R2, R3, R4 independently represent a hydrogen atom or an organic functional group; Y represents an alkylene group 5 in C1-Clo or an aryl group in C6-Co10 optionally substituted, are present in the composition

liquid reaction.

  The organic functional group (R1 ,, R2 R3, R4) suitably represents an unsubstituted or substituted hydrocarbon group, such as an alkyl group,

  unsubstituted or substituted aryl or cycloalkyl.

  Suitably, the hydrocarbon group

  represents an alkyl group such as a C1-C15 alkyl group, or an aryl group such as a C615 Clo aryl group.

  The hydrocarbon group can be substituted by one or

several substituents.

  Suitably, the substituted hydrocarbon group may be a C1-C10 alkyl group or a CC 0 aryl group substituted by one or more of -NH2, -NO2, -SH, a halogen atom, -CO2R, - COR6, -OR7, -COX, CSX-1, -CN, -NCS or -NCO o R5 R6 and R7 independently represent a hydrogen atom, an unsubstituted or substituted hydrocarbon group, such as a C1-alkyl group -Clo or a C6-C10 aryl group, optionally substituted with one or more heteroatoms such as an oxygen atom, a nitrogen atom or a sulfur atom; X and X1 are independently chosen from -NH2, -NO2, -SH, a hydrogen atom, -CH3, - (CH2) nX2, a halogen atom, -C02R8, -COR9, -COX3, -CSX4, - CN, -NCS or -NCO o R8 and R9 are defined as for R5 or R6 or R7 and X2, X3 and X4 are defined as for X or X1; n is worth

from 1 to 10.

  Suitably, the substituted hydrocarbon group can be - (CH2) nX5 o n is from 1 to 10, -CHX6X7, CXX9X o X 5, X 6, X7 'X8, X9 and X90 are defined

as for X and X1.

  The organic functional group can include nitrogen, oxygen, sulfur atoms or mixtures thereof.

  Suitably, the organic functional group may be -CO2R ', -SO2Rll, -COR2, -COXll, -CSX2, -CN, -NCS or -NCO o Rl, Rll, R12 are defined as for R5 or R6

  or R 7; Xll and X12 are defined as for X or X1.

  Suitably, when the organic functional group represents an aryl group, such as a C6-Co10 aryl group, it may be substituted by one or more heteroatoms, such as a sulfur atom, an oxygen atom, a nitrogen atom or combinations thereof. Preferably, R 'to R4 each represent a hydrogen atom or a C1-C15 alkyl group such as a group

-CH3 or -CH (CH3) 2.

  Y represents an optionally substituted C1-C1 alkylene group, such as a C3-C10 cycloalkyl group or Y represents an optionally substituted C1-C1 aryl group. The cycloalkyl or aryl group may be substituted by one or more substituents such as

  than those defined for X or X1 above.

  Y preferably represents an unsubstituted C130 Cl0 alkyl group such as -CH2, - (CH2) 2-, a C3-C1O cycloalkyl group or a substituted C6-Cl0 aryl group, such as substituted benzene. More

  preferably, Y represents a 1,2-disubstituted benzene or C3-C10 cycloalkyl group.

  Suitably, R1 and R4 each represents a hydrogen atom or each represents a C1-Cls alkyl group such as a -CH3 group or a group

  -CH3 (CH3) 2 and Y represents an unsubstituted C1-C10 alkylene group such as CH2, - (CH2) 2-, or an optionally substituted C3-C10 cycloalkyl group or an optionally substituted C6-C10 aryl group that a substituted benzene 10, for example, a 1,2-substituted benzene ring.

  Specific examples of suitable bisphosphonate compounds include tetraisopropyl 1,2-ethylenedisphosphonate, methylene diphosphonic acid and bis (1,2-dimethoxyphosphoryl) benzene.

  The bis-phosphonate promoter is present, so

  suitable, in the reaction composition in a molar ratio of promoter to iridium of [greater than 0 to 10]: 1, preferably [0.2 to 2]: 1, more preferably [greater than 0 to 0 , 5]: 1.

  The bis-phosphonate compound employed in the present invention may be added as such to the liquid reaction composition or may be formed in situ in the liquid reaction composition, for example, by the addition of the bis-phosphonic acid conjugate to the

liquid reaction composition.

  The carbon monoxide reagent may be essentially pure or may contain inert impurities such as carbon dioxide, methane, nitrogen, noble gases, water and C1 to C4 paraffinic hydrocarbons. The presence of hydrogen in the carbon monoxide charge and formed in situ by the

  The gas-to-water transformation reaction is preferably kept low since its presence can result in the formation of hydrogenation products.

  Thus, the amount of hydrogen in the carbon monoxide reagent is preferably less than 1 mole%; more preferably less than 0.5 mole% and still more preferably less than 0.3 mole% and / or the partial pressure of hydrogen in the carbonylation reactor is preferably less than 10 partial pressure d 'l bar, more preferably less than 0.5 bar and most preferably less than 0.3 bar. The partial pressure of carbon monoxide in the reactor is in the range

  greater than 0 to 40 bar, typically 4 to 30 bar.

  The total pressure of the carbonylation reaction is suitably in the range of 10 to 200 barg, preferably 15 to 100 barg, more preferably 15 to 50 barg. The temperature of the carbonylation reaction is suitably in the range of 100 to 300 ° C, preferably in the range of 150

at 2200C.

  The present invention can be carried out as a batch process or as a continuous process, preferably,

as a continuous process.

  The acetic acid product can be recovered from the

  liquid reaction composition by withdrawing the vapor and / or the liquid from the carbonylation reactor and recovering acetic acid from the material withdrawn.

  Preferably, the acetic acid is recovered from the liquid reaction composition by continuously withdrawing the liquid reaction composition from the carbonylation reactor and recovering the acid.

  acetic acid from the liquid reaction composition taken up by one or more stages of flash and / or fractional distillation in which acetic acid is separated from the other components of the liquid reaction composition such as the iridium catalyst, the methyl iodide cocatalyst , the promoter, methyl acetate, methanol and / or its unreacted reactive derivatives, water and the acetic acid solvent which can be recycled to the reactor to maintain their concentrations in the liquid reaction composition.

  In order to maintain the stability of the iridium catalyst during the recovery stage of the acetic acid product, the water in the process streams containing the iridium carbonylation catalyst to be recycled to the carbonylation reactor must be maintained at a

  concentration of at least 0.5% by weight.

  The invention will now be illustrated only with the aid of examples and with reference to the following examples.

  General description of carbonylation experiments

  The experiments were carried out in a 300 cm3 zirconium autoclave, equipped with an agitator and a liquid injection installation. The autoclave was pressure tested at 4 x 106 N / m2 with nitrogen, then rinsed three times with carbon monoxide to 1 x 106 N / m2. If a promoter or additive was used, it was placed in the autoclave and covered with part of the acid (approximately 10 g) before the pressure test. An initial charge which consists of methyl acetate (approximately 60.0 g), acetic acid (approximately 58.0 g) methyl iodide (approximately 14 g) and water (approximately 0.7 g) was placed in the autoclave, which was again purged with carbon monoxide and degassed slowly

  to prevent loss of volatile matter.

  Carbon monoxide (approximately 5 to 7 x 107 N / M2) was placed in the autoclave which was then heated with stirring (1500 rpm) to 190 ° C. The catalyst injection system was primed with approximately 1.35 g of hexachloroiridic acid (IV), acetic acid (approximately 10.0 g) and water 10 (approximately 5.0 g ) and a carbon monoxide overpressure was injected into the hot autoclave to bring the pressure of the autoclave to 2.8 x 106 N / m2. The reaction rate was controlled by the drop in carbon monoxide pressure from a charge tank, typically under a pressure of 7 x 106 N / m2. The temperature and pressure of the autoclave were maintained at constant values of 190 ° C. and 2.8 × 10 6 N / M2 over the entire duration of the reaction by means of pressure control and coolant valves. . The reaction was terminated when the charge pressure drop

  became less than 1 x 10 N / m2 for 5 minutes.

  After cooling, a gas analysis sample was taken and the autoclave was degassed. The liquid compounds were discharged and analyzed for liquid by-products by established known gas chromatography methods. The compounds detected are quantified by integrating the peaks of the compounds with respect to an external standard expressed in

parts per million (ppm) by weight.

  In the batch reaction, "total" propanoic acid was defined as the sum of propanoic acid and its precursors (ethyl acetate and ethyl iodide) converted to ppm (propanoic acid) detected in liquid products cooled from the reaction by

batches, expressed in ppm.

  The rate of gas uptake at some point in the course of the reaction was used to calculate the

  carbonylation rate, in number of moles of reagent consumed per liter of the composition of the cold degassed reactor per hour (mole / l / h), to a particular reactor composition (total reactor composition based on a degassed volume cold).

  The methyl acetate concentration was calculated during the reaction from the starting composition, assuming that one mole of methyl acetate was consumed for each mole of carbon monoxide which was consumed. There was no tolerance for

  organic compounds in the autoclave headspace.

  By monitoring the rate of the carbonylation reaction and calculating the concentration of the reaction compounds during the experiment, it is possible to determine the rate of the carbonylation reaction which should be expected if a carbonylation process were to be carried out continuously. maintaining a regular liquid reaction composition which is the same as the total reaction composition calculated at any particular point

in the batch experiment.

  In the batch experiment, the term "reaction composition" refers to the total composition of

  compounds in the autoclave in the cold degassed state.

  Experiments A to D and Examples 1 to 5 The general procedure described above was used. The load compositions are presented in

Table 1.

  Experiments A to D are not in accordance with the present invention in that no bisphosphonate compound was present in the composition

liquid reaction.

  Examples 1 to 5 demonstrate the effect on the carbonylation rate of the addition of a bisphosphonate compound in accordance with the present invention (1,2-bis (dimethoxyphosphoryl) benzene (dmpb), in the absence of a conventional promoter, using an iridium catalyst at 188 ° C. and a total pressure of 28 barg. The speed data at an acetate concentration of

  methyl (MeOAc) of about 30% at a water concentration of about 2% by weight are presented in Table 2.

  Table 1 Filler compositions for the reactions catalyzed by iridium in an autoclave in a batch with 20 zirconium of 300 cm3 Expe-Acid Amount riences MeOAc ctiue MeI Water H2IrC16 Promoter of / (g) a (g) (g) (ga) tor promoter Example (g)

A 61.08 59.19 13.99 0.80 1.349 -

B 60.52 58.94 13.97 0.70 1.360 -

C 60.02 68.99 13.96 6.46 0.642 -

D 60.02 69.00 13.96 6.40 0.636 -

  1 61.13 59.31 13.97 0.72 1.37 dmpb 0.142 2 60.25 59.39 13.98 0.71 1.39 dmpb 0.233 3 60.04 58.54 14.05 0.71 1 , 37 dmpb 0.347 4 60.11 58.01 13.99 0.70 1.39 dmpb 0.455 60.04 58.12 13.96 0.69 1.359 dmpb 0.542 a) Weight expressed as pure H2IrCl6 Table 2 Velocity data carbonylation for reactions catalyzed by iridium in a 300 cm3 zirconium autoclave Example Promoter Water Speed Acid Rate H2 C02 CH4 / molar% in / mol / l / h Propa- mmol) (mmol) (mmol) Expeditor: weight @ 30% our iridium MeOAc rience (ppm)

A - - 2.0 14,719 0.1 1.6 2.3

B - - 2.0 13.1 379 0.7 1.1 1.5

  C - 2.1 12.1 n / year / year / year / a D - 0.3: 1 2.0 13.3 n / year / year / year / a 1 dmpb 2.0 17.6 737 0, 1 1.1 1.5 2 dmpb 0.5: 1 2.0 15.8 501 1.3 1.4 1.8 3 dmpb 0.75: 1 2.0 16.6 373 0.8 2.2 1.3 4 dmpb 1: 1 2.0 18.8 566 0.8 1.2 1.6 dmpb 1.25: 1 2.0 17.5 397 0.7 2.0 1.3 Relating

to the blackboard

  2, a comparison of Examples 1 to 5 with experiments A to D demonstrates that by adding a bis-phosphonate compound in accordance with the invention, this provides a significant increase in the rate of carbonylation compared to that obtained by carbonylation catalyzed by iridium in the absence of a bis-phosphonate promoter and in the

same conditions.

Claims (25)

  1. Process for the production of acetic acid by carbonylation with carbon monoxide of methanol 5 and / or its reactive derivatives in a carbonylation reactor containing a liquid reaction composition substantially free of a promoter chosen from the group consisting of ruthenium , osmium, tungsten, rhenium, zinc, gallium, cadmium and indium, said liquid reaction composition comprising an iridium carbonylation catalyst, a methyl iodide co-catalyst, a finite concentration of water, acetic acid, methyl acetate, and a promoter, a process in which the water concentration is at or below that at which the maximum in the graph of the carbonylation rate as a function of the water concentration occurs and in which the promoter is a bisphosphonate compound corresponding to the formula I R2 O y \ -R3    (I) I 2 3 4   wherein R, R, R, R independently represent a hydrogen atom or an organic functional group; Y represents an alkylene group   optionally substituted C1-Clo or C6-C10 aryl.   2. The method of claim 1, wherein R1, R2, R3, R4 independently represent a functional, organic group selected from an unsubstituted hydrocarbon group and a substituted hydrocarbon group. 3. Method according to claim 1 or 2, wherein R1, R2, R3, R4 each represent a hydrogen atom or each represent a hydrocarbon group not substituted.   4. The method of claim 3, wherein each unsubstituted hydrocarbon group represents a -CH3 group or CH (CH3) 2- group.   5. Method according to any one of   claims 1 to 4, wherein Y is selected from the group consisting of a non-C1-C10 alkylene group   substituted, an optionally substituted C6-C1O aryl group and a C3-C10 cycloalkyl group optionally unsubstituted.   6. The method of claim 5, wherein the unsubstituted C1-C10 alkylene group is selected from   the group consisting of -CH2- and (CH2) 2-.   7. The method of claim 5, wherein the optionally substituted C6C10 aryl group   represents a substituted benzene group.   8. The method according to claim 1, in which Y is chosen from an unsubstituted C1-C10 alkylene group, an optionally substituted C3-ClO cycloalkyl group and an optionally substituted C6-C10 aryl group and R ,, R R3, R4 each represents a hydrogen atom or each represents a hydrogen group not substituted.   9. The method of claim 8, wherein each unsubstituted hydrocarbon group represents a methyl group.   10. The method of claim 1, wherein   bis-phosphonate is chosen from the group which consists of tetra- 1,2ethylenediphosphonate   isopropyl, methylene diphosphonic acid and bis (1,12dimethoxyphophoryl) benzene. 11. Method according to any one of   claims 1 to 10, wherein the bis-phosphonate is   formed in situ in the liquid reaction composition. 12. The method of claim 11, wherein   bis-phosphonate is formed from conjugated bisphosphonic acid.   13. Method according to any one of   Claims 1 to 10, wherein the bisphosphonate promoter is added to the reaction composition   liquid in the form of a bis-phosphonate compound.   14. Method according to any one of   claims 1 to 13, wherein the bis15 phosphonate compound is present in the reaction composition   liquid at a molar ratio of the bis-phosphonate compound:   iridium in the range [greater from 0 to 10]: 1.   15. The method of claim 14, wherein   the molar ratio of the bis-phosphonate compound: iridium 20 is in the range of [0.2 to 2]: 1.   16. Method according to any one of   claims 14 or 15, wherein the molar ratio of bisphosphonate: iridium is in the range of [0.5 to 1.2]: 1.   17. Method according to any one of   claims 1 to 16, wherein the concentration of the iridium carbonylation catalyst in the liquid reaction composition is in the range of   400 to 5000 ppm measured in iridium.   18. Method according to any one of   claims 1 to 17, wherein the concentration of   methyl acetate in the reaction composition   liquid is in the range of 1 to 70% by weight.   19. Method according to any one of   claims 1 to 18, wherein the concentration of methyl iodide in the reaction composition   liquid is in the range of l to 30% by weight.   20. Method according to any one of   claims 1 to 19, wherein methanol,   methyl acetate or their mixtures are carbonylated.   21. Method according to any one of   claims 1 to 20, wherein the water concentration in the liquid reaction composition is   kept below 6% by weight.   22. The method of claim 21, wherein the concentration of water in the reaction composition   liquid is kept below 4.5% by weight.   23. Method according to any one of   claims 1 to 22, wherein the carbonylation reaction temperature is in the range of 100 to 20,300 "C and the total pressure is in the range of 10 to barg.   24. Method according to any one of   claims 1 to 23, wherein the liquid reaction composition is substantially free of a co-promoter selected from the group consisting of iodides   of alkali metals, alkaline earth metal iodides, metal complexes which can form I-,   salts which can form I- and their mixtures.   25. The method of claim 1, wherein the concentration of iridium carbonylation catalyst in the liquid reaction composition is in the range of 400 to 5000 ppm measured in iridium, the concentration of methyl acetate in the liquid reaction composition is in the range of 1 to 70% by weight, the concentration of methyl iodide in the liquid reaction composition is in the range of 1 to 30% by weight, the bis-phosphonate compound is present   in the liquid reaction composition at a molar ratio of the bis-phosphonate: iridium compound in the range [greater than 0 to 10]: 1 and the water concentration in the liquid reaction composition is kept below 6% by weight.