GB2327420A

GB2327420A - Production of oxygenated compounds

Info

Publication number: GB2327420A
Application number: GB9815547A
Authority: GB
Inventors: Andrew David Poole; John Glenn Sunley
Original assignee: BP Chemicals Ltd
Current assignee: BP Chemicals Ltd
Priority date: 1997-07-22
Filing date: 1998-07-17
Publication date: 1999-01-27
Anticipated expiration: 2018-07-17
Also published as: GB2327420B; GB9815547D0; GB9715402D0

Abstract

A process for the production of oxygenated organic compounds comprises contacting at elevated temperature carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) (i) at least one olefinically unsaturated compound and, optionally (ii) at least one alcohol and/or a reactive derivative thereof, (b) an iridium catalyst, (c) a halide co-catalyst, (d) at least a finite concentration of water, and (e) as promoter, at least one of (i) cadmium, (ii) mercury, (iii) zinc, (iv) gallium, (v) indium, (vi) tungsten, and (vii) rhenium provided that in the absence of an alcohol and/or a reactive derivative thereof (A) in the presence of promoters (i) to (vi) water is present in an amount less than 3% by weight based on the weight of the liquid reaction composition, and (B) in the presence of promoters (i) to (vii) the partial pressure of carbon monoxide is less than 5 bar.

Description

PROCESS FOR THE PRODUCTION OF OXYGENATED COMPOUNDS The present invention relates generally to the production of oxygenated organic compounds by the carbonylation of an olefinically unsaturated compound.

More particularly the invention relates to the production of oxygenated organic compounds by the carbonylation in the presence of an iridium catalyst of an olefinically unsaturated compound in the presence or absence of an alcohol and/or a reactive derivative thereof.

The process whereby oxygenated organic compounds are produced by the carbonylation of olefins in the presence of an iridium catalyst is known from, for example, US Patent Nos. 3,818,060 and 3,821,265.

US Patent No. 3,818,060 discloses a process for converting ethylenically unsaturated compounds selectively to carboxylic acids by reaction in the liquid phase with carbon monoxide and water at temperatures from about 50"C to 300"C, preferably 125 to 225 C, and at partial pressures of carbon monoxide from I psia to 15,000 psia, preferably 5 psia to 3,000 psia, in the presence of an improved catalyst system comprised of an iridium or rhodium-containing compound, a promoter portion, i.e. a halide, and a stabiliser component, i.e. an organic derivative of pentavalent phosphorus, arsenic, antimony, nitrogen or bismuth such as organic phosphine oxides and sulphides, arsine oxides and sulphides, stibine oxides, amine oxides and bismuth oxides.

US Patent No. 3,821,265 discloses the conversion of ethylenically unsaturated compounds selectively to carboxylic acids by reaction in the liquid phase with carbon monoxide and water at temperatures from about 50"C to 300"C and at partial pressures of carbon monoxide from 1 psia to 15000 psia in the presence of an improved catalyst system comprised of an iridium or rhodiumcontaining compound, a promoter portion, i.e. a halide, and a stabiliser component, i.e. a molybdenum or a chromium compound, the stabiliser performing the function of preventing catalyst precipitation during either reaction and/or distillation of the products from the catalyst solution after the reaction has taken place. In addition the catalyst systems are said to exhibit high reactivity and long catalyst life.

More recently our UK Application Publication No. 2298648 discloses a process for the carbonylation of a carbonylatable reactant having a carbonylatable moiety having at least two carbon atoms and/or a reactive derivative thereof, which reactants include olefins, which process comprises contacting said carbonylatable reactant and/or reactive derivative thereof with carbon monoxide in a liquid reaction composition in a carbonylation reactor characterised in that the liquid reaction composition comprises: (a) an iridium catalyst, (b) a halide, (c) at least a finite concentration of water, (d) a carbonylatable reactant as aforesaid, and (e) as promoter, at least one of ruthenium and osmium. A particularly preferred embodiment it is said is to co-feed methanol and/or (methyl acetate and water) with (ethylene and water) and/or ethanol and/or (ethyl acetate and water) to coproduce acetic acid and propionic acid.

The technical problem to be solved is the provision of an improved process for the production of oxygenated organic compounds by the carbonylation in the presence of an iridium catalyst and a halide co-catalyst of an olefinically unsaturated compound in the presence or absence of an alcohol and/or a reactive derivative thereof. A solution to the problem is the use in the process of at least one promoter selected from the group consisting of cadmium, mercury, zinc, gallium, indium, tungsten and rhenium.

Accordingly, the present invention provides a process for the production of oxygenated organic compounds which process comprises contacting at elevated temperature carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) (i) at least one olefinically unsaturated compound, and, optionally (ii) at least one alcohol and/or a reactive derivative thereof, (b)an iridium catalyst, (c) a halide co-catalyst, (d) at least a finite concentration of water, and (e) as promoter at least one of (i) cadmium, (ii) mercury, (iii) zinc, (iv) gallium, (v) indium, (vi) tungsten, and (vii) rhenium provided that in the absence of an alcohol and/or a reactive derivative thereof (A) in the presence of promoters (i) to (vi) water is present in an amount less than 3% by weight based on the weight of the liquid reaction composition, and (B) in the presence of promoters (i) to (vii) the partial pressure of carbon monoxide is less than 5 bar.

Suitable olefinically unsaturated compounds (a) (i) include mono-olefins and di-olefins, and fiinctionalised derivatives thereof. Preferred mono-olefins are C2 to C6 mono-olefins, more preferred are C2 to C4 mono-olefins, for example ethylene and propylene. Most preferred is ethylene. A mixture of mono-olefins may be employed. Functional derivatives of mono-olefins include, for example, mono-olefinically unsaturated carboxylic acids. Suitable di-olefins include C4 to C6 dienes. A preferred diene is butadiene. Gaseous olefins, for example ethylene or butadiene, may be fed to the carbonylation reactor either together with or separately from the carbon monoxide reactant. Typically, the concentration in the liquid reaction composition of the olefin may suitably be in the range from 1 to 50% by weight based on the weight of the composition.

Optional component (a) (ii) of the liquid reaction mixture is at least one alcohol and/or a reactive derivative thereof. Suitable alcohol reactants include monofunctional aliphatic alcohols, aliphatic diols and aliphatic polyols. Preferably the alcohol is selected from the group consisting of monofunctional alkyl alcohols, alkyl diols and alkyl polyols. Preferably component (b) is a C1 to C10, more preferably C1 to C6, most preferably C1 to C4, alkyl alcohol. A preferred alkyl alcohol is methanol.

Suitable reactive derivatives of the alcohol include the corresponding alkyl ester of the alcohol and the corresponding carboxylic acid product, dialkyl ethers and alkyl halides, preferably iodides or bromides. Suitable reactive derivatives of methanol include methyl acetate, dimethyl ether and methyl iodide. A mixture of alkyl alcohols and reactive derivatives thereof may be used as reactants in the process of the present invention. Preferably methanol and/or methyl acetate are used as reactants. At least some of the alkyl alcohol and/or reactive derivative thereof will be converted to, and hence be present as, alkyl esters in the liquid reaction composition by reaction with carboxylic acid product or solvent. The concentration, in the liquid reaction composition, of alkyl ester is suitably in the range from 1 to 70% by weight, preferably 2 to 50% by weight and yet more preferably 3 to 35% by weight.

The process is particularly applicable to the production of an oxygenated organic compound which is a carboxylic acid. Carbonylation of a mono-olefin having n carbon atoms provides a carboxylic acid having n+l carbon atoms, for example the carbonylation of ethylene provides propionic acid. Carbonylation of a monofunctional alcohol (i.e. one having one-OHgroup) having m carbon atoms and/or a reactive derivative thereof is a carboxylic acid having m+l carbon atoms and/or an ester ofthe carboxylic acid having m+l carbon atoms and the alcohol having m carbon atoms, for example the carbonylation of methanol and/or a reactive derivative thereof is acetic acid and/or methyl acetate. Thus, the product of carbonylating a mixture of at least one olefinically unsaturated compound having n carbon atoms and at least one monofunctional alcohol or reactive derivative thereof having m carbon atoms comprises a mixture of at least one carboxylic acid having n+l carbon atoms, at least one carboxylic acid having m+l carbon atoms and/or at least one ester of the carboxylic acid having m+l carbon atoms and the alcohol having m carbon atoms.

Component (b) of the liquid reaction composition is an iridium catalyst.

The iridium component of the catalyst in the liquid reaction composition may comprise any iridium-containing compound which is soluble in the liquid reaction composition. The iridium component of the catalyst may 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 to a soluble form.

Examples of suitable iridium-containing compounds which may be added to the liquid reaction composition include IrCl3, IrI3, IrBr3, [Ir(CO)2I]2, [Ir(CO)2CI]2, [Ir(CO)2Br]2, [Ir(CO)2I2]H+, [Ir(CO)2Br2]Y, [Ir(CO)2I2t, [Ir(CH3)I3(CO2)2]-H+, fr4(CO)12, IrCl3.3H2O, IrBr3.3H20, 1r4(CO)12, iridium metal, Ir203, IrO2, Ir(acac)(CO)2, Ir(acac)3, iridium acetate, [Ir3O(OAc)6(H2O)3][OAc], and hexachloroiridic acid [H2IrCl6], preferably, chloride-free complexes of iridium such as acetates, oxalates and acetoacetates which are soluble in one or more of the carbonylation reaction components such as water, alcohol and/or carboxylic acid.

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

Preferably, the iridium catalyst concentration in the liquid reaction composition is in the range 100 to 6000 ppm by weight of iridium.

Component (c) of the liquid reaction composition is a halide co-catalyst.

The halide co-catalyst is suitably a hydrogen halide, e.g. hydrogen iodide, or a hydrocarbyl halide, preferably an alkyl halide. Suitable alkyl halides have alkyl moieties corresponding to the alkyl moiety of the alkyl alcohol reactant and are preferably C1 to C10, more preferably C1 to C6, and yet more preferably C1 to C4 alkyl halides. Preferably the alkyl halide is an iodide or bromide, more preferably an iodide. A preferred alkyl halide is methyl iodide. Suitably the concentration of the halide co-catalyst in the liquid reaction composition is in the range from 0.1 to 20%, more preferably 0.1 to 16% by weight.

Component (d) of the liquid reaction composition is at least a finite concentration of water. Water may be formed in situ in the liquid reaction composition, for example, by the esterification reaction between alkyl alcohol reactant and carboxylic acid product. Water may be introduced to the carbonylation reactor together with or separately from other components of the liquid reaction composition. Water may be separated from other components of reaction composition withdrawn from the reactor and may be recycled in controlled amounts to maintain the required concentration of water in the liquid reaction composition. Suitably, the concentration of water in the liquid reaction composition is in the range 0.1 to 20% by weight, typically 1 to 15% by weight, for example 1 to 10% be weight, provided that in the absence of an alcohol and/or a reactive derivative thereof and in the presence of promoters other than rhenium water is present in an amount less than 3% by weight based on the weight of the liquid reaction composition.

Component (e) of the liquid reaction composition is at least one promoter selected from cadmium, mercury, zinc, gallium, indium, tungsten, and rhenium.

The promoter may comprise any cadmium, mercury, zinc, gallium, indium, tungsten, or rhenium-containing compound which is soluble in the liquid reaction composition. The promoter may 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 to a soluble form.

Examples of suitable cadmium-containing compounds which may be used include Cd(OAc)2. CdI2, CdBr2, CdCl2, Cd(OH)2, and cadmium acetylacetonate.

Examples of suitable mercury-containing compounds which may be used include Hg(OAc)2, HgI2, HgBr2, HgCl2, Hug212, and Hg2C12.

Examples of suitable zinc-containing compounds which may be used include Zn(OAc)2, Zn(OH)2, ZnI2, ZnBr2, ZnCl2, and zinc acetylacetonate.

Examples of suitable gallium-containing compounds which may be used include gallium acetylacetonate, gallium acetate, GaCI3, GaBr, GaI3, Ga2C4 and Ga(OH)3.

Examples of suitable indium-containing compounds which may be used include indium acetylacetonate, indium acetate, Inc3, InBr3, InI3, InI and In(OH)3.

Examples of suitable tungsten-containing compounds which may be used include W(CO)6, WCl4, WC16, WBr5, WI2, CsH12 W(CO)3 and any tungsten chloro bromo- or iodo-carbonyl compound.

Examples of suitable rhenium-containing compounds which may be used include Re2(CO)10, Re(CO)5CI, Re(CO)5Br, Re(CO)51, ReCI3. H20 and ReCI5 .yH2O.

The molar ratio of each promoter: iridium catalyst is suitably in the range (0.1 to 20): 1, preferably (0.5 to 10): 1. More than one promoter may be used.

Preferably the iridium catalyst and the promoter-containing compounds are free of impurities which provide or generate in situ ionic iodides which may inhibit the reaction, for example alkali or alkaline earth metal or other metal salts.

Ionic contaminants such as, for example, (a) corrosion metals, particularly nickel, iron and chromium and (b) phosphines or nitrogen-containing compounds or ligands, which may quaternise in situ, should be kept to a minimum in the liquid reaction composition as these may generally have an adverse effect on the reaction by generating I- in the liquid reaction composition which may have an adverse effect on the reaction rate. Some corrosion metal contaminants such as for example molybdenum have been found to be less susceptible to the generation of I Corrosion metals which have an adverse effect on the reaction rate may be minimised by using suitable corrosion resistant materials of construction. Similarly, contaminants such as alkali metal iodides, for example lithium iodide, should in general be kept to a minimum. Corrosion metal and other ionic impurities may be reduced by the use of a suitable ion exchange resin bed to treat the reaction composition, or preferably a catalyst recycle stream. Such a corrosion metal removal process is described in US 4007130.

The carbon monoxide reactant 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 and generated in situ by the water gas shift reaction is preferably kept low, for example, less than 1 bar partial pressure, as its presence may result in the formation of hydrogenation products. The partial pressure of carbon monoxide in the reaction is suitably in the range 1 to 70 bar, preferably 1 to 35 bar, more preferably 1 to 15 bar, provided that in the absence of an alcohol and/or a reactive derivative thereof and in the presence of rhenium as promoter the partial pressure of carbon monoxide is less than 5 bar.

The total pressure ofthe carbonylation reaction is suitably in the range 10 to 200 barg, typically 10 to 100 barg, for example 10 to 50 barg. The temperature ofthe carbonylation reaction is suitably in the range 100 to 300 "C, preferably in the range 150 to 220"C.

Carboxylic acid and/or ester thereof may be used as a solvent for the reaction.

In a preferred embodiment of the present invention acetic acid and propionic acid are co-produced by the process comprising contacting at elevated temperature carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) ethylene, (b) methanol and/or methyl acetate, (c) an iridium catalyst, (d) methyl iodide, (e) water, and (f) as promoter at least one of cadmium, mercury, zinc, gallium, indium, tungsten, and rhenium.

The process of the present invention may be performed as a batch or a continuous process, preferably as a continuous process. The carboxylic acid(s) and/or ester(s) thereof product may be removed from the reactor by withdrawing liquid reaction composition and separating the carboxylic acid product(s) and/or ester(s) thereof by one or more flash and/or fractional distillation stages from the other components of the liquid reaction composition such as iridium catalyst, cadmium, mercury, zinc, gallium, indium tungsten, or rhenium promoter, alkyl halide, water and unconsumed reactants which may be recycled to the reactor to maintain their concentrations in the liquid reaction composition. The carboxylic acid product(s) and/or ester(s) thereof may also be removed as a vapour from the reactor.

In another preferred embodiment of the present invention propionic acid is produced by a process comprising contacting at elevated temperature in the absence of an alcohol and/or a reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of the liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.

In a further preferred embodiment of the present invention pentenoic acid is produced by a process comprising contacting at elevated temperature in the absence of an alcohol and/or a reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising butadiene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of the liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.

Pentenoic acid is a valuable product because it can be converted to adipic acid (HOOC(CH2)4COOH) which is used for making nylon and derived polymers.

In yet another preferred embodiment propionic acid is produced by a process comprising contacting at elevated temperature in the absence of an alcohol and/or a reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, ethyl iodide and/or hydrogen iodide, water in an amount of from 0.5 to 20% by weight based on the weight of the liquid reaction composition and as promoter rhenium, the partial pressure of carbon monoxide being less than 5 bar.

The invention will be now be illustrated by way of example only by reference to the following example.

Experimental Procedure I Experiment A and Example 1 were performed using a 300 ml zirconium autoclave equipped with a magnetically driven stirrer, liquid catalyst injection facility and cooling coils. A gas supply to the autoclave was provided from a ballast vessel, feed gas being provided during the course of an experiment to maintain the autoclave at a constant pressure.

Experiment A The autoclave was pressure tested with nitrogen and then vented via a gas sampling system. The autoclave was then flushed several times with carbon monoxide/ethylene 4 1. Acetic acid (45.3 lug), methyl acetate (60.03g), water (14.40g) and methyl iodide (13.97g) were then charged to the autoclave via a liquid addition port. The autoclave was pressurised with carbon monoxide/ethylene 4 : (1 to 8) barg and heated with stirring (1500 rpm) to 1900C.

Once stable at temperature the autoclave pressure was increased to 25 barg by feeding carbon monoxide/ethylene 4:1 from the ballast vessel. The catalyst, H2IrCl6 (0.643g), dissolved in acetic acid (10.01g)/water (5.71g), was then injected using an overpressure of carbon monoxide to give a total reactor pressure of 28 barg. The reactor pressure was maintained at a constant value (28 i 0.5 barg) by feeding carbon monoxide/ethylene (4:1) from the ballast vessel. The reaction temperature was maintained within + 1"C of the desired reaction temperature by means of a heating mantle connected to a Eurotherm (Trade Mark) control system. In addition, excess heat of reaction was removed by means of cooling coils. After 27 minutes the heater was turned off and the ballast vessel isolated. The reactor was then crash cooled by means of the cooling coils.

0.875 moles of gas (carbon monoxide/ethylene at a 4:1 volumetric ratio) were consumed from the ballast vessel. The off-gas vented from the autoclave was analysed by GC and contained 2.3% v/v hydrogen, 2.6% v/v carbon dioxide, 4.2% v/v methane, 0.2% v/v ethane and 1.9% v/v ethylene. GC analysis showed the solution recovered from the autoclave to contain 77% w/w acetic acid and 5.9% w/w propionic acid.

This is not an example according to the present invention because no promoter was present in the liquid reaction composition.

Example 1 Experiment A was repeated in the presence of an indium promoter. InI3 (3.87g) and acetic acid (10.02g) were charged to the autoclave. The autoclave was pressure tested with nitrogen and then vented via a gas sampling system. The autoclave was then flushed several times with carbon monoxide/ethylene (4 1).

Acetic acid (31.45g), methyl acetate (60.00g), water (14.36g) and methyl iodide (13.96g) were then charged to the autoclave via a liquid addition port. The autoclave was pressurised with carbon monoxide/ethylene (4:1) to 6 barg and slowly vented. The autoclave was then pressurised with carbon monoxide/ethylene (4:1) to 8 barg and heated with stirring (1500 rpm) to 1900C. Once stable at temperature the autoclave pressure was increased to 25 barg by feeding carbon monoxide/ethylene (4 1) from the ballast vessel. The catalyst, H2IrCl6 (0.635g), dissolved in acetic acid (10.Olg)/water (5.72g), was then injected using an overpressure of carbon monoxide to give a total reactor pressure of 28 barg. The reactor pressure was maintained at a constant value (28 l 0.5 barg) by feeding carbon monoxide/ethylene (4:1) from the ballast vessel. The reaction temperature was maintained within l 1"C of the desired reaction temperature by means of a heating mantle connected to a Eurotherm (Trade Mark) control system. In addition, excess heat of reaction was removed by means of cooling coils. After 27 minutes the heater was turned off and the ballast vessel isolated. The reactor was then crash cooled by means of the cooling coils.

1.215 moles of gas (carbon monoxide/ethylene at a 4:1 volumetric ratio) were consumed from the ballast vessel. The off-gas vented from the autoclave was analysed by GC and contained 1.1% v/v hydrogen, 7.4% v/v carbon dioxide, 13.5% v/v methane, 0.6% v/v ethane and 1.6% v/v ethylene. GC analysis showed the solution recovered from the autoclave to contain 77% w/w acetic acid and 9.8% w/w propionic acid.

This is an example according to the present invention and demonstrates the co-production of acetic and propionic acids by carbonylation of a mixed methyl acetate/ethylene and water feed using an indium promoted iridium catalyst.

Comparison of Example 1 with Experiment A demonstrates the beneficial effect of indium on the propionic acid yield. This is illustrated in Table 1 below.

Table 1

Experiment Reaction time / minutes Propionic acid / % w/w(a) A 27 5.9 1 27 9.8 a) By GC analysis of recovered solution.

The rate of gas uptake at a certain point in the reaction was used to calculate the carbonylation rate, based upon moles of carbon monoxide consumed per litre of cold degassed reactor composition per hour (moWhr). Carbonylation rates for Example 1, calculated at certain points in the reaction run, are compared with those calculated for Experiment A in Table 2 and demonstrate the promotional effect of indium on the carbonylation rate.

Table 2

Experiment Moles of gas Carbonylation rate / Moles of gas Carbonylation rate / consumed(a) mollllhr(b) consumed (a) moWh(b) 1 0.311 24.6 0.623 25.1 A 0.311 14.8 0.623 9.0 a) Number of moles of combined carbon monoxide/ethylene feed consumed from the ballast vessel. b) Based upon moles of carbon monoxide consumed per litre of cold degassed reactor composition per hour.

Exnerimental Procedure II Experiments B - E and Examples 2 - 5 were performed using the following general procedure: A 300mL Hastelloy B2 (Trade Mark) autoclave equipped with a Magnedrive (Trade Mark) stirrer and liquid injection facility was used for a series of batch carbonylation experiments. A gas supply to the autoclave was provided from a gas ballast vessel, feed gas being provided to maintain the autoclave at a constant pressure and the rate of gas uptake being calculated (with an accuracy believed to be +/-3%) from the rate at which the pressure falls in the gas ballast vessel.

At the end of each experiment liquid and gas samples from the autoclave were analysed by gas chromatography.

For each batch carbonylation experiment the autoclave was charged with a promoter selected from indium, rhenium, and gallium where appropriate and the liquid components of the liquid reaction composition excluding part of the water and acetic acid charge, in which the iridium catalyst was dissolved.

The autoclave was flushed twice with nitrogen, and once with carbon monoxide and was then heated with stirring (950 rpm) to 1800C. After allowing the system to stabilise for about 30 minutes, the iridium catalyst in acetic acid/water solution was then injected into the autoclave under pressure of carbon monoxide. The pressure in the autoclave was subsequently maintained at a precise pressure between 11 and 14 barG with carbon monoxide fed on demand from the gas ballast vessel through the liquid injection facility.

Gas uptake from the ballast vessel was measured every 2 seconds and from this was calculated the rate of carbonylation, expressed as millimoles of carbon monoxide per minute (mmoVmin). After the uptake of carbon monoxide from the ballast vessel had ceased or the period of the reaction reached 35 minutes, whichever was sooner, the autoclave was isolated from the gas supply. The autoclave was subsequently cooled to room temperature and the gases were cautiously vented from the autoclave and analysed. The liquid reaction composition was discharged from the autoclave, sampled and was analysed for liquid products and by-products.

To obtain a reliable baseline a number of identical baseline runs may have to be performed to condition the autoclave such that consistent rates are achieved.

This conditioning period is often different from autoclave to autoclave and may depend upon its previous history.

The autoclave charges, and reactor pressure for the following experiments and examples are shown in Table 3. The non-condensable gases in the autoclave were analysed and the relative volumes of carbon dioxide and hydrogen are listed in Table 4, the balances comprising nitrogen and carbon monoxide. Analysis of the liquid reaction media revealed n-heptanoic acid to be the major product, for example Example 2 contained 15% b.w. n-heptanoic acid and 3% b.w. 2-methylhexanoic acid, i.e. the branched isomer. All reactions were undertaken at 1800C.

Experiment B A baseline experiment was performed at a low water concentration using hex-1-ene as the carbonylatable olefin. The reaction was performed at a constant pressure of 14 barG. No linear carbonylation rate was observed during the reaction, moreover, the rate of carbonylation was found to decrease until the reaction was stopped after 35 minutes. The rate of carbon monoxide uptake was measured when the water concentration r

Example 3 Experiment B was repeated except that gallium triiodide (5.07 mmol) was added to the autoclave. Based on the rate of carbon monoxide uptake from the ballast vessel the carbonylation rate at a calculated water concentration of 2.8%w/w was found to be 4.4. mmol/min. The carbonylation rate decreased during the course of the reaction until all the reaction stopped after 19 minutes.

This example is according to the present invention. It demonstrates that addition of gallium promotes the iridium catalyst at low water concentrations and 14 barG.

Experiment D Experiment B was repeated except that dirhenium decacarbonyl (2.47 mmol) was added to the autoclave. Based on the rate of carbon monoxide uptake from the ballast vessel the carbonylation rate at a calculated water concentration of 2.8%w/w water was found to be 3.9 mmoUmin. The carbonylation rate decreased during the course ofthe reaction until the reaction was stopped after 35 minutes.

This example is not according to the present invention. It demonstrates that addition of rhenium does not enhance the carbonylation rate at 14 barG.

ExPeriment E Experiment B was repeated at 11 barG total pressure thus affording a further baseline experiment at lower carbon monoxide partial pressures.

The reaction rate was 5.6 mmoMmin at a calculated water concentration of 4.0%w/w, based upon carbon monoxide uptake rate. The reaction was stopped after 35 minutes.

Example 4 Experiment E was repeated except that Re2(CO)10(2.48 mmol) was also charged to the autoclave.

Based upon the rate of carbon monoxide uptake, the carbonylation rate at a calculated water concentration of 4%w/w was found to be 8.5 mmoMmin.

This example is according to the present invention as it demonstrates that addition of Re2(CO)10 to the carbonylation mixture affords the benefit of promotion of rate.

Example 5 Experiment E was repeated except that indium triiodide (4.84 mmol) was also charged to the autoclave.

The rate of carbon monoxide uptake was measured and found to be 10.3 mmoUmin at a calculated water concentration of 4%w/w.

This example is according to the present invention as it demonstrates that addition of indium to the carbonylation mixture affords the benefits of rate promotion at reduced carbon monoxide partial pressure.

Table 3

AcOH H2O Aqueous hex-1-ene hex-2-ene IrCl3.3H2O Promoter Reaction (grams) (grams) HI(a) (grams) (grams) (grams) Pressure (grams) (barG) Experiment B 117.98 0.30 0.60 16.80 - 0.354(b) - 14 Experiment C 117.99 0.30 0.65 - 16.79 0.350(b) - 14 Example 2 115.52 0.30 0.64 16.79 - 0.354(c) In(e) 14 Example 3 115.77 0.38 0.65 16.81 - 0.352(b) Ga(f) 14 Experiment D 116.40 - 1.80 16.80 - 0.352(d) Re(g) 14 Experiment E 117.99 0.31 0.66 16.81 - 0.353(b) - 11 Example 4 116.38 - 1.78 16.80 - 0.352(d) Re(h) 11 Example 5 115.52 0.32 0.65 16.81 - 0.357(c) In(i) 11 (a) A 57%w/w solution in H2O (b) IrCl3.3H2O dissolved in 5.7g H2O and 2.0g AcOH (c) IrCl3.3H2O dissolved in 5.7g H2O and 2.3g AcOH (d) IrCl3.3H2O dissolved in 5.5g H2O and 2.0g AcOH (e) InI3 (2.11g) (f) GaI3 (2.28g) (g) Re2(CO)10(1.61g) (h) Re2(CO)10(1.62g) (i) In3I (2.11g) Table 4

H2(%v/v) CO2(%v/v) Experiment B 6.3 5.6 Experiment C 4.8 4.5 Example 2 10.9 9.9 Example 3 8.2 5.4 Experiment D 5.6 3.2 Experiment E 3.5 14.6 Example 4 5.7 5.7 Example 5 10.5 13.5

Claims

Claims: 1. A process for the production of oxygenated organic compounds which process comprises contacting at elevated temperature carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) (i) at least one olefinically unsaturated compound and, optionally (ii) at least one alcohol and/or a reactive derivative thereof, (b) an iridium catalyst, (c) a halide co-catalyst, (d) at last a finite concentration of water, and (e) as promoter, at least one of(i) cadmium, (ii) mercury, (iii) zinc, (iv) gallium, (v) indium, (vi) tungsten, and (vii) rhenium provided that in the absence of an alcohol and/or a reactive derivative thereof (A) in the presence of promoters (i) to (vi) water is present in an amount less than 3% by weight based on the weight of the liquid reaction composition, and (B) in the presence of promoters (i) to (vii) the partial pressure of carbon monoxide is less than 5 bar.
2. A process as claimed in claim 1 wherein the olefinically unsaturated compound is a C2 to C6 mono-olefin or C4 to C6 diolefin.
3. A process as claimed in claim 1 or claim 2 wherein the alcohol is selected from monofirnctional aliphatic alcohols, aliphatic diols and aliphatic polyols.
4. A process as claimed in claim 3 wherein the alcohol is a C1 to C4 alkyl alcohol.
5. A process as claimed in claim 1 or claim 2 wherein the halide cocatalyst is hydrogen halide or a hydrocarbyl halide.
6. A process as claimed in claim 5 wherein the halide cocatalyst is present at a concentration of from 0.1 to 20% by weight.
7. A process as claimed in any one of the preceding claims wherein water is present at a concentration of from 0.1 to 20% by weight.
8. A process as claimed in any one of the preceding claims wherein the iridium catalyst is present at a concentration of from 100 to 6000 ppm by weight iridium.
9. A process as claimed in any one of the preceding claims wherein the molar ratio of promoter to iridium catalyst is in the range (0.1 to 20):1.
10. A process as claimed in any one of the preceding claims carried out under a pressure of from 10 to 200 barg and a temperature of from 100 to 300"C.
11. A process for the production of acetic acid and propionic acid which comprises contacting at elevated temperatures carbon monoxide in a carbonylation reactor with a liquid reaction comprising (a) ethylene, (b) methanol, and/or methyl acetate, (c) an iridium catalyst, (d) methyl iodide, (e) water, and (f) as promoter at least one of cadmium, mercury, zinc, gallium, indium, tungsten and rhenium.
12. A process for the production of propionic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or reactive derivative thereof, carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.
13. A process for the production of propionic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, ethyl iodide and/or hydrogen iodide, water in an amount of from 0.5 to 20% by weight, based on the weight of the liquid reaction composition and as promoter rhenium, the partial pressure of carbon monoxide being less than 5 bar.
14. A process for the production of pentanoic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or a reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid composition comprising butadiene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of the liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.
15. A process as hereinbefore described in accordance with examples, 1, 2, 3, 4 and 5.

15. A process as hereinbefore described in accordance with the accompanying examples.

Amendments to the claims have been filed as follows Claims: 1. A process for the production of at least one carboxylic acid which process comprises contacting at elevated temperature carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) (i) at least one olefinically unsaturated compound and, optionally (ii) at least one alcohol and/or a reactive derivative thereof, (b) an iridium catalyst, (c) a halide co-catatyst, (d) at last a finite concentration of water, and (e) as promoter, at least one of (i) cadmium, (ii) mercury, (iii) zinc, (iv) gallium, (v) indium, (vi) tungsten, and (vii) rhenium provided that in the absence of an alcohol and/or a reactive derivative thereof (A) in the presence of promoters (i) to (vi) water is present in an amqunt less than 3% by weight based on the weight of the liquid reaction composition, and (B) in the presence of promoters (i) to (vii) the partial pressure of carbon monoxide is less than 5 bar 2. A process as claimed in claim l wherein the olefinically unsaturated compound is a C2 to C6- mono-olefin or C4 to C6 diolefin.

3. A process as claimed in claim I or claim 2 wherein the alcohol is selected from monofunctional aliphatic alcohols, aliphatic diols and aliphatic polyols.

4. A process as claimed in claim 3 wherein the alcohol is a C to C, alkyl alcohol.

5. A process as claimed in claim I or claim 2 wherein the halide cocatalyst is hydrogen halide or a hydrocarbyl halide.

6. A process as claimed in claim 5 wherein the halide cocatalyst is present at a concentration of from 0. I to 20% by weight.

7. A process as claimed in any one of the pr-ecedin claims wherein water is present at a concentration of from 0. 1 to 20% by weight.

8. A process as claimed in any one of the preceding claims wherein the iridium catalyst is present at a concentration of from 100 to 6000 ppm by weight iridium.

9. A process as claimed in any one of the preceding claims wherein the molar ratio of promoter to iridium catalyst is in the range (0. 1 to 20): 1.

10. A process as claimed in any one of the preceding claims carried out under a pressure of from 10 to 200 barg and a temperature of from 100 to 300 C.

11. A process for the production of acetic acid and propionic acid which comprises contacting at elevated temperatures carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising (a) ethylene, (b) methanol, and/or methyl acetate, (c) an iridium catalyst, (d) methyl iodide, (e) water, and (f) as promoter at.least one of cadmium, mercury, zinc, gallium, indiurn, tungsten and rhenium.

12. A process for the production of propionic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or reactive derivative thereof, carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.

13. A process for the production of propionic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid reaction composition comprising ethylene, an iridium catalyst, ethyl iodide and/or hydrogen iodide, water in an amount of from 0.5 to 20% by weight, based on the weight of the liquid reaction composition and as promoter rhenium, the partial pressure of carbon monoxide being less than 5 bar.

14. A process for the production of pent(noic acid which comprises contacting at elevated temperature in the absence of an alcohol and/or a reactive derivative thereof carbon monoxide in a carbonylation reactor with a liquid composition comprising butadiene, an iridium catalyst, hydrogen iodide, water in an amount less than 3% by weight based on the weight of the liquid reaction composition and as promoter at least one of cadmium, mercury, zinc, gallium, indium and tungsten.