Title of Invention

A PROCESS FOR THE PREPARATION OF A CARBOXYLIC ACID

Abstract

The present invention relates to a process for the preparation of a carboxylic acid. Particularly, the present invention relates to a process for the preparation of a carboxylic acid by the reaction of an alcohol with carbon monoxide in the presence of a palladium compound as catalyst, an organic or an inorganic halide and an organic sulphonic acid as promoter, water and a solvent under mild conditions. The process steps comprises: carbonylating the corresponding alcohol in carbon monoxide atmosphere and in the presence of water, a solvent, a palladium catalyst and a promoter system consisting of an organic or inorganic halide and an organic sulphonic acid, at a temperature in the range of 50 - 250°C, at a pressure in the range of 50 - 2000 psig for 1 to 10 hours, the concentration of the catalyst being one mole of catalyst per every 50 - 50000 moles of the alcohol, the amount of the organic or inorganic halide being in the range of 5 - 500 moles per mole of the catalyst, and the amount of the organic sulphonic acid being in the range of 5 - 500 moles per mole of the catalyst, collecting the resulting product.

Full Text

PROCESS FOR THE PREPARATION OF A CARBOXYLIC ACLD Field of the invention The present invention relates to a process for the preparation of a carboxylic acid. Particularly, the present invention relates to a process for the preparation of a carboxylic acid by the reaction of an alcohol with carbon monoxide in the presence of a palladium compound as catalyst, an organic or an inorganic halide and an organic sulphonic acid as promoter, water and a solvent under mild conditions. Background of the invention Acetic acid has been produced industrially on a large scale by methanol carbonylation by the well known Monsanto and Cativa™ processes. US Patent 3816490, European Patents EP 728726A1 and EP 752406A1 disclose the use of rhodium or iridium as catalyst to produce acetic acid using methanol and carbon monoxide in the presence of iodide promoters and water. The disadvantage of these processes is the high costs and limited availability of the catalyst. The use of nickel in the presence of iodides has been reported for the carbonylation of methanol to acetic acid [US Patent 4902569 and J. Catal. (156), 290, (1995)]. However these processes use drastic conditions. Palladium and platinum catalysts carbonylation of methyl iodide to acetic acid with quaternary iodide promoter is disclosed in J. Chem. Soc. Chem. Commun. 179 - 180 (1999). However the activity level is low (Turn Over Number TON = 110), and methyl iodide is used as starting material. European Patent EP 0133331 discloses the palladium catalysed carbonylation of methanol to acetic acid in the presence of metal iodide, methyl iodide and sulfolane or sulfoxide. However, in this process sulfolane or sulfoxide are essential components. As can be seen, the prior art processes suffer from several disadvantages such as the use of expensive starting materials resulting in higher cost of production; low activity; or require extreme operating conditions thereby rendering the process expensive. It is therefore important to develop a process for the preparation of a carboxylic acid that overcomes the drawbacks enumerated above. Objects of the invention The main object of the present invention is to provide a process for the preparation of a carboxylic acid that overcomes the twin drawbacks of low activity and drastic reaction conditions. It is another object of the invention to provide a process for the preparation of a carboxylic acid that operates at milder reaction conditions. It is further object of the invention to provide a process of a carboxylic acid such as acetic acid using metal halides and organic sulphonic acid as promoters. It is yet another object of the invention to provide a process for the preparation of a carboxylic acid that is efficient and less expensive. Summary of the invention These and other objevts of the invention are achieved by providing a palladium catalysed process for the carbonylation of an alcohol to the corresponding carboxylic acid in the presence of halide and organic sulphonic acid promoters, water and a solvent at milder reaction conditions. 1. Accordingly the present invention provides A process for preparation of carboxylic acid comprising carbonylating the corresponding alcohol in carbon monoxide atmosphere and in the presence of water, a solvent, a palladium catalyst selected from palladium(II) or palladium(O) salt or metal complex of palladium(II) or palladium(O) and a promoter system consisting of an organic or inorganic halide and an organic sulphonic acid, at a temperature in the range of 50 - 250°C, at a pressure in the range of 50 - 2000 psig for 1 to 10 hours, the concentration of the catalyst being one mole of catalyst per every 50 - 50000 moles of the alcohol, the amount of the organic or inorganic halide being in the range of 5 - 500 moles per mole of the catalyst, and the amount of the organic sulphonic acid being in the range of 5 - 500 moles per mole of the catalyst, collecting the resulting product. In one of the embodiments of the present invention the reacting alcohol used is ROH, wherein R is an alkyl group having 1 to 5 carbon atoms. In another embodiment of the catalyst used comprises palladium (II) or palladium (0) compound selected from the group consisting of palladium chloride, palladium bromide, palladium iodide and palladium acetate, or a metal complex of palladium selected from the group consisting of bis (triphenylphosphino) dichloro palladium(II), bis(triphenylphosphino) bibromo palladium(II), bis(triparatolylphosphino) dichloropalladium(II), bis(triparatolylphosphino) bibromopalladium(II), tetrakis(triphenylphosphino) dichloropalladium(O) and tetrakis(triphenylphosphino) dibromopalladium(O). In a further embodiment of the invention, the organic halide used is of the formula RX wherein R is an alkyl group having 1 to 5 carbon atoms and X is a halogen selected from Cl,Br,and I. In another embodiment of the invention, the organic sulphonic acid used is selected from the group consisting of benzene sulphonic acid, paratolyl sulphonic acid, methane sulphonic acid, and trifluoromethane sulphonic acid. In a further embodiment of the invention, the solvent used comprises a ketone selected from the group consisting of acetone, diethyl ketone and acetophenone; or a cyclic ether selected from tetrahydrofuran and dioxan; or a nitrile selected from acetonitrile and benzonitrile; or an organic solvent selected from toluene and benzene. In another embodiment of the invention, the concentration of the catalyst is one mole of catalyst for every 100 - 5000 moles of the alcohol, preferably one mole of catalyst for every 150 - 1000 moles of the alcohol. In another embodiment of the invention, the amount of organic or inorganic halide promoter used is in the range of 25 to 150 moles per mole of catalyst. In yet another embodiment of the invention, the amount of the organic sulphonic acid used is in the range of 50 - 150 moles per mole of catalyst. In a further embodiment of the invention, the amount of water is in the range of 1 to 30%(v/v) of the total reaction mixture, preferably 3-25 %. In another embodiment of the invention, the pressure of the carbon monoxide used is in the range of 200 - 1000 psig. In a further embodiment of the invention, the temperature of the reaction mixture is in therangeof70-200°C. Detailed description of the invention The invention will now be described with reference to the following examples which are illustrative and should not be construed as limiting the scope of the invention in any manner. Example 1 A 50 ml autoclave was charged with the following: Methanol : 0.03125 mol Pd(OAc)2 : 0.0001 mol p-toluene sulphonic acid : 0.01 mol Lil : 0.01 mol H2O : 1 ml Methyl ethyl ketone : 21 ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 94% conversion of methanol with 65 % selectivity to acetic acid and 4% selectivity to methyl acetate with turn over frequency (TOF) of24h'1. Example 2 Methanol Pd(OAc)2 p-toluene sulphonic acid Nail H20 Methyl ethyl ketone A 50 ml autoclave was charged with the following: 0.03125 mol 0.0001 mol 0.01 mol 0.01 mol 1 ml 21ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 97 % conversion of methanol with 79 % selectivity to acetic acid and 5 % selectivity to methyl acetate with turn over frequency (TOF) of25h'1. Example 3 Methanol Pd(OAc)2 p-toluene sulphonic acid KI H2O Methyl ethyl ketone A 50 ml autoclave was charged with the following: 0.03125 mol 0.0001 mol 0.01 mol 0.01 mol 1 ml 21ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 4.5 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 97 % conversion of methanol with 74 % selectivity to acetic acid and 3 % selectivity to methyl acetate with turn over frequency (TOF) of21h'1. Example 4 A 50 ml autoclave was charged with the following: Methanol Pd(OAc)2 p-toluene sulphonic acid KI H20 Methyl ethyl ketone 0.03 125 mol 0.0001 mol 0.01 mol 0.01 mol 5ml 16ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 1 15°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 4.5 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 94 % conversion of methanol with 65 % selectivity to acetic acid and 4% selectivity to methyl acetate with turn over frequency (TOF) Example 5 Methanol Pd(OAc)2 p-toluene sulphonic acid CH3I H20 Methyl ethyl ketone 0.03125 mol 0.0001 mol 0.01 mol 0.01 mol 1ml 21 ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 23% conversion of methanol with 44 % selectivity to acetic acid and 44% selectivity to methyl acetate with turn over frequency (TOF)of3h4. Example 6 A 50 ml autoclave was charged with the following. Methanol : 0.03125 mol Pd(OAc)2 : 0.0001 mol Benzene sulphonic acid : 0.01 mol Lil : 0.01 mol H2O : 1 ml Methyl ethyl ketone : 21 ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 59 % conversion of methanol with 8 % selectivity to acetic acid and 8 % selectivity to methyl acetate with turn over frequency (TOP) of2h'1. Example 7 A 50 ml autoclave was charged with the following: Ethanol : 0.03125 mol Pd(OAc)2 : 0.0001 mol p-toluene sulphonic acid : 0.01 mol Lil : 0.01 mol H2O : 1 ml Methyl ethyl ketone : 21 ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 54% conversion of ethanol with 15 % selectivity to propionic acid and 6 % selectivity to ethyl propionate with turn over frequency (TOF)of3h'1. Example 8 A 50 ml autoclave was charged with the following: Methanol Pd(OAc)2 p-toluene sulphonic acid Lil H2O Acetonitrile 0.03125 mol 0.0001 mol 0.01 mol 0.01 mol 1 ml 21ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 10 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 83 % conversion of methanol with 67 % selectivity to acetic acid and 18 % selectivity to methyl acetate with turn over frequency (TOF)of 16h"'. Example 9 Methanol Pd(OAc)2 p-toluene sulphonic acid HI H20 Methyl ethyl ketone A 50 ml autoclave was charged with the following: 0.03125 mol 0.0001 mol 0.01 mol 0.01 mol 3.8ml 16ml The contents of the autoclave were flushed once with nitrogen and thrice with carbon monoxide at room temperature. Thereafter, the contents were heated at 115°C. The autoclave was pressurized with carbon monoxide to SOOpsig after the temperature was attained. The contents were stirred for 4.5 hours continuously. The reactor was then cooled to room temperature and the gas was vented off. The contents were analysed by gas chromatography. The results of the gas chromatography showed 88 % conversion of methanol with 92 % selectivity to acetic acid and 2 % selectivity to methyl acetate with turn over frequency (TOP) of 46 h4. When Examples 1, 2, and 3 were repeated in the absence of organic sulphonic acid, no acetic acid or methyl acetate was formed. This clearly establishes that metal iodide and organic sulphonic acid work together for the carbonylation of methanol. The novelty in this invention lies inter alia, in the use of a catalyst system comprising palladium catalyst, and a promoter comprising organic or inorganic halide and an organic sulphonic acid for the carbonylation of an alcohol to the corresponding carboxylic acid. Advantages of the invention 1. The process of the invention uses an alternative catalytic system that is more economical and efficient. 2. The process can also be used for other carboxylic acids and esters other than acetic acid and methyl acetate. 3. The reaction conditions required for performance are mild. We claim: 1. A process for preparation of carboxylic acid comprising carbonylating the corresponding alcohol in carbon monoxide atmosphere and in the presence of water, a solvent, a palladium catalyst selected from palladium(II) or palladium(O) salt or metal complex of palladium(II) or palladium(O) and a promoter system consisting of an organic or inorganic halide and an organic sulphonic acid, at a temperature in the range of 50 - 250°C, at a pressure in the range of 50 - 2000 psig for 1 to 10 hours, the concentration of the catalyst being one mole of catalyst per every 50 - 50000 moles of the alcohol, the amount of the organic or inorganic halide being in the range of 5 - 500 moles per mole of the catalyst, and the amount of the organic sulphonic acid being in the range of 5 - 500 moles per mole of the catalyst, collecting the resulting product. 2. A process as claimed in claim 1, wherein the alcohol is ROH, where R is any alkyl group having 1 to 5 carbon atoms. 3. A process as claimed in claims 1 and 2, wherein the catalyst used comprises palladium (II) or palladium (0) compound selected from the group consisting of palladium chloride, palladium bromide, palladium iodide and palladium acetate, or a metal complex of palladium selected from the group consisting of bis (triphenylphosphino) dichloro palladium(II), bis(triphenylphosphino) bibromo palladium(II), bis(triparatolylphosphino) dichloropalladium(II), bis(triparatolylphosphino) bibromopalladium(II), tetrakis(triphenylphosphino) dichloropalladium(O) and tetrakis(triphenylphosphino) dibromopalladium(O). 4. A process as claimed in claims 1 to 3, wherein the organic halide used is of the formula RX wherein R is an alkyl group having 1 to 5 carbon atoms and X is a halogen selected from Cl, Br, I. 5. A process as claimed in claims 1 to 3, wherein an inorganic halide used is of the formula MX where M is hydrogen or an alkali metal selected from the group consisting of Li, Na, K and X is halogen selected from Cl, Br, I 6. A process as claimed in any preceding claim , wherein organic sulphonic acid used is selected from the group consisting of benzene sulphonic acid, para tolyl sulphonic acid, methane sulphonic acid and or trifluoromethane sulphonic acid. 7. A process as claimed in any preceding claim wherein the solvent comprises a ketone selected from acetone, diethyl ketone, and acetophenone; or cyclic ether selected from tetrahydrofuran and dioxin; or a nitrile selected from acetonitrile and benzonitrile; or an organic solvent selected from toluene and benzene. 8. A process as claimed in any preceding claim , wherein the concentration of the catalyst is one mole of catalyst for every 100- 50000 moles of the alcohol, preferably one mole of the catalyst for every 150-1000 moles of the alcohol. 9. A process as claimed in any preceding claim wherein the amount of organic halide or an inorganic halide promoter used is preferably in the range of 25 to 150 moles per mole of the catalyst. 10. A process as claimed in any preceding claim wherein the amount of organic sulphonic acid used is preferably in the range of 50-150 moles per mole of the catalyst. 11 . A process as claimed in any preceding claim wherein the amount of water is in the range of 1 to 30%(v/v) of the total reaction mixture, preferably 3 to 25%(v/v) of the total reaction mixture. 12. A process as claimed in any preceding claim wherein the pressure of carbon monoxide used is preferably in the range of 200-1000 psig. 13. A process as claimed in any preceding claim wherein the temperature of the reaction mixture is preferably in the range of 70 to 200°C. 14. A process for preparation of carboxylic acid substantially as herein described with reference to the examples.

Documents:

893-del-2001-abstract.pdf

893-del-2001-claims.pdf

893-del-2001-correspondence-others.pdf

893-del-2001-correspondence-po.pdf

893-del-2001-description (complete).pdf

893-del-2001-form-1.pdf

893-del-2001-form-18.pdf

893-del-2001-form-2.pdf

893-del-2001-form-3.pdf

893-del-2001-petition-138.pdf