Preparation of sulphonated polyketones

Abstract: Sulphonated polyketones are prepared by reacting a linear alternating copolymer of carbon monoxide and one or more olefins (polyketone) with a sulphonating agent (eg chlorosulphoric acid) in a solvent (eg dichloromethane) at a temperature in the range -20 to +40°C. A molar excess of sulphonating agent is preferably used. The sulphonated polyketone produced contains one or more types of unit of formula -[COC(R¹)₂C(R¹)₂]- wherein the R¹ groups are independently H, C₁ to C₁₀ alkyl or SO₃H with the proviso that at least one R¹ group is SO₃H.

Description: The present invention relates to sulphonated polyketones and processes for their preparation. EP 121965 and EP 213671 disclose a class of polymers, hereafter called polyketones, which can be synthesised by the action of carbon monoxide on alkene(s) in an alcohol in the presence of a palladium catalyst, a chelate phosphine and an anion of an acid having a pKa less than two. The polyketones produced are linear alternating copolymers of carbon monoxide and the alkene(s) employed. It has now been found that polyketones of the type disclosed in EP 121965 and EP 213671 may be modified by sulphonation and that the resulting sulphonated polyketones are strongly acidic solids useful as acidic catalysts in for example homogeneous and heterogenous catalytic processes. These modified polyketones comprise one or more types of units of the general formula:- where the R¹ groups are independently selected from H or C₁ to C₁₀ alkyl or SO₃H with the proviso that at least one R¹ group is SO₃H. It is preferred that those R¹ groups which are not SO₃H are selected from H or C₁ to C₄ alkyl, most preferably H or methyl. The polymers are stable and the SO₃H groups are strongly acidic as a result of the electron withdrawing power of the ketone functionality. Whilst the polymers to be used according to the present invention may consist exclusively of units of the general formula given above it is envisaged that the polymers may also contain other units. In particular, since the polymer has been produced by sulphonation of a corresponding polyketone, the polymer may also contain one or more types of unit having the formula:- wherein the R¹ groups are independently selected from H or C₁ to C₁₀ alkyl only. The present invention also relates to novel copolymers comprising one or more types of units having the formula (I) and one or more types of units of the general formula:- due to dehydration of the polyketone. In this formula the R² groups are independently selected from H, C₁ to C₁₀ alkyl or SO₃H. The polymer to be used according to the present invention is preferably comprised of 15-100% by weight of units of formula (I). The polymer defined above can be prepared by a process which comprises the step of sulphonating a corresponding polyketone comprised of one or more types of unit of formula II. Typical processes for effecting such a sulphonation are described in the textbook "Sulphonation and Related Reactions" by E E Gilbert, Interscience Publishers, NY, 1965. A particularly good method of sulphonation consists of reacting a slurry of the polyketone with a sulphonating agent in the presence of a solvent. The preferred solvents are halogenated solvents eg dichloroethane and glacial acetic acid, with dichloroethane being most preferred. Preferably the process is carried out at a temperature in the range -20 to +40°C, most preferably -5 to +5°C. Suitable sulphonating agents include chlorosulphonic acid, concentrated sulphuric acid, pyridine/sulphur trioxide, 2,6-lutidine/sulphur trioxide and mixtures of chlorosulphonic acid with concentrated sulphuric acid, dimethyl formamide, 1,4-dioxane or triethyl phosphate. The most preferred sulphonating agent is chlorosulphonic acid. It is preferred that the sulphonating agent is used in a molar excess over the polyketone. The new polymers are chemically reactive and can be used as precursors for further chemical transformations. An example is the preparation of thiol containing polymers by reacting the sulphonated polyketone with PCl₅ and subsequent reduction. The product is a thiol polymer of one or more types of unit of the general formula: where R¹ can be independently selected from H or C₁ to C₁₀ alkyl or SH with the proviso that at least one R¹ is SH. Such thiol polymers may of course also contain one or more types of unit having formulae analogous to the formulae (I)-(III) given above. Such thiol containing polymers can be used inter alia as ion-exchange resins. By virtue of their strongly acidic properties, the sulphonated polyketones of the present invention are also useful catalysts for processes which require an acid catalyst. An example of such a process is esterification wherein a carboxylic acid, typically a C₁ to C₁₀ aliphatic carboxylic acid is reacted with an alcohol, typically a C₁ to C₁₀ aliphatic alcohol to produce the corresponding ester. According to the present invention there is therefore provided a process for the preparation of an ester whose process comprises reacting a carboxylic acid with an alcohol in the presence of a sulphonated polyketone as described above. The sulphonated polyketones of the present invention are also effective as agents for removing ammonia or amines from solution. This is particularly advantageous when the medium containing ammonia or amines does not dissolve the sulphonated polyketone. Thus a solution of ammonia or amine in such a medium can be pumped or otherwise drawn through a bed of the sulphonated polyketone at a rate sufficient to effect complete removal from the medium of the ammonia or amines. The following examples illustrate the invention. Example 1 A slurry of an ethene/CO copolymer (4g) (prepared according to EP 121965) in 70ml of dichloroethane was prepared and cooled to 0°C. A solution of ClSO₃H (5.3ml) in 30ml of dichloroethane was then added to the slurry, with stirring, over a period of fifteen minutes. The resulting mixture was stirred for a further thirty minutes while the temperature was maintained at 0°C and then poured into 200ml of methanol. The resulting product was then filtered, the residue washed twice with water and dried under vacuum. A yield of 5.08g of a brown granular solid was obtained containing 7.7% by weight of sulphur and 2.95 mmoles g⁻¹ of acid sites. Results from ¹³C solid state NMR analysis were consistent with known SO₃H compounds. Example 2 The procedure of Example 1 was repeated using 20% oleum (15.1ml) as the sulphonating agent. A yield of 6.4g of a black solid was obtained containing 4.06 mmoles g⁻¹ of acid sites and 10.8% by weight of sulphur. Example 3 The procedure of Example 1 was repeated using concentrated sulphuric acid (10ml) as the sulphonating agent. A yield of 9.82g of a black solid was obtained which contained 7.54 mmoles g⁻¹ of acid sites and 14.2% by weight of sulphur. Example 4 The procedure of Example 1 was repeated using glacial aceticacid as the solvent and concentrated sulphuric acid (5mL) as the sulphonating agent. The experiment was carried out at 16°C for one hour. The product was filtered and washed twice with dichloroethane. A pale brown solid (4.20g) was obtained which contained 1.29 mmoles g⁻¹ acid sites and 3.4% by weight of sulphur. Example 5 The procedure of Example 1 was repeated using a mixture of ClSO₃H (5.3ml) and DMF (12.2ml) as the sulphonating agent. After addition, the resulting mixture was warmed to 16°C and stirred for two hours. A pale brown solid (4.20g) was obtained which contained 1.29 mmoles g⁻¹ acid sites and 3.4% by weight of sulphur. Example 6 The procedure of Example 1 was repeated using a mixture of ClSO₃H (5.3ml) and 1,4 - dioxane (13.4ml) as the sulphonating agent. A dark solid (6.28g) was obtained containing 2.02 mmoles g⁻¹ of acid sites and 3.5% by weight of sulphur. Example 7 The procedure of Example 1 was repeated using a mixture of ClSO₃H (5.3ml) and triethyl phosphate (26.7ml) as the sulphonating agent. A yield of 4.31g of polymer was obtained which contained 0.77 mmoles g⁻¹ acid sites and 1.7% by weight of sulphur. Example 8 The procedure of Example 1 was repeated using pyridine-sulphur trioxide (12.5g) as the sulphonating agent. The temperature was increased to 16°C and the reaction carried out over twenty four hours. A yield of 4.16g of polymer was obtained which contained 0.82 mmoles g⁻¹ of acid sites and 0.3% by weight of sulphur. Example 9 The procedure of Example 8 was repeated using 2,6-lutidine-sulphur trioxide (27g) as the sulphonating agent. A grey solid was obtained (3.68g) containing 0.23 mmoles g⁻¹ of acid sites and 0.1% by weight of sulphur. Example 10 A sample of an ethene/propene/CO terpolymer (5g), containing 7 mole % propene in form of beads of 250-600 um diameter, was suspended in 50ml of dichloroethane. The resulting mixture was cooled to 0°C. A solution of ClSO₃H (6ml) in dichloroethane (50ml) was added, with stirring, over a period of 45 minutes. The beads were then separated by filtration, washed twice with dichloroethane, twice with water and then dried under vacuum. The beads were found to contain 6.9% by weight of sulphur and 3.2 mmoles g⁻¹ of acid sites. Example 11 A sample of the sulphonated polyketone (5g) prepared as described in Example 1 was suspended in CH₃CCl₃(50ml) containing 4g of PCl₅. The resulting mixture was stirred at room temperature for three hours. The solution was then filtered and the solid product washed twice with CH₃CCl₃. The washed product was then suspended in 50ml of acetic acid and 5g of zinc powder added to the mixture, with stirring. The reaction was then left for sixteen hours. The resulting mixture was poured into 500ml water prior to filtration. The product was further treated with 500ml of 1M HCl and the resulting solution filtered again. A yield of 4.75g of a thiol - containing product was obtained. Example 12 - Esterification of Acetic Acid A sample of the sulphonated polyketone (100mg) prepared as described in Example 1 was suspended in a mixture of acetic acid (110 mmole), methanol (110 mmole) and cyclohexane (0.60g, used as internal standard in gas chromatography). The reaction mixture was stirred at 55°C for three hours. Samples were extracted at 30 minute intervals and analysed for ester content using gas chromatography. The reaction was repeated except the sulphonated polyketone was replaced by a commercial sulphonic acid polymer, Amberlyst 15. The reaction was further repeated in the absence of a catalyst. The results are shown in Figure 1. Example 13 A sample of the sulphonated polyketone (2g) prepared as described in Example 1 was added to a burette as a slurry in 30ml of methanol. Diethylamine (60mmole) was added to the burette and allowed to diffuse through the polymer at a rate of 10 bed volumes per hour. The polymer effluent was collected in 5ml aliquots. Alternate aliquots were titrated with 14mM HCl to determine amine content, using bromothymol blue as indicator. The results are shown in Figure 2.

Claims: A polymer which is a copolymer of one or more types of units having the formula (I) where the R¹ groups are independently selected from H or C₁ to C₁₀ alkyl or SO₃H with the proviso that at least one R¹ group is SO₃H, and one or more types of units having the formula:- where the R² groups are independently selected from H or C₁ to C₁₀ alkyl or SO₃H. A process for preparing a polymer of one or more types of unit of formula (I) which comprises the step of reacting a polyketone in a solvent with a sulphonating agent at a temperature in the range -20 to +40°C. A process as claimed in claim 2 wherein the sulphonating agent is selected from chlorosulphonic acid, concentrated sulphuric acid, pyridine/sulphur trioxide, 2,6 lutidine/sulphur trioxide and mixtures of chlorosulphonic acid with concentrated sulphuric acid, dimethylformamide, 1,4-dioxane or triethyl phosphate. A process as claimed in claim 2 wherein the sulphonating agent is chlorosulphonic acid. A process as claimed in claim 2 wherein the solvent is dichloroethane. A polymer of one or more types of unit having the general formula:- where R¹ groups are selected from H, C₁ to C₁₀ alkyl or SH with the proviso that at least one R¹ group is SH. A process for the preparation of an ester which process comprises reacting a carboxylic acid with an alcohol in the presence of a sulphonated polyketone which comprises one or more types of unit having the formula I as defined in claim 1. A process for removing ammonia or amines from solution comprising pumping or drawing a solution of ammonia or amine through a bed of sulphonated polyketone which comprises one or more units having the formula I as defined in claim 1.

Inventors: BROWN STEPHEN LAURENCE THE BRI, BROWN, STEPHEN LAURENCE, THE BRITISH PETROLEUM CO.
Applicants: BRITISH PETROLEUM CO PLC, THE BRITISH PETROLEUM COMPANY P.L.C.
Application year: 1990
Main classification: C08G67
IPC codes: C08G67, C08G61