GB2202165A - Process for the hydrocarbonylation of ethylene, acrylic acid and/or an acrylate ester - Google Patents

Abstract

Process for the hydrocarbonylation of ethylene, acrylic acid and/or an acrylate ester having less than 10 C atoms per molecule by contacting said compounds with CO and H2 in the presence of a solvent and of a novel catalytic system formed by combining:- a) a Pt (II) compound, b) a cheating organic compound containing at least two coordinating P atoms connected through a divalent organic bridging group having at least two C atoms in the bridge, and c) an acid having a pKa <3, except hydrohalogenic acids, and/or a metal salt of such an acid, except halides, the metal being a Group 4A metal or a non-noble transition metal.

Description

PROCESS FOR THE HYDROCARBONYLATION OF ETHYLENE, ACRYLIC ACID AND/OR AN ACRYLATE ESTER The invention relates to a process for the hydrocarbonylation of ethylene, acrylic acid and/or an acrylate ester having less than ten carbon atoms per molecule. The invention also relates to a novel catalytic system.

Hydrocarbonylation of ethylene yields 3-pentanone, a ketone that may be used as a solvent for oils, waxes and resins and for dewaxing of mineral oil fractions. An example of this hydrocarbonylation is given in Bull. Chem. Soc. Japan, 54, 2089-2092 (1981), where a Co2 (CO)8-phosphine catalytic system is used. This known process yields 3-pentanone with a high selectivity, but at a very low rate.

It is an object of the present invention to effect the hydrocarbonylation mentioned in the beginning at a high rate and also with a very high selectivity.

Accordingly, the invention provides a process for the hydrocarbonylation of ethylene, acrylic acid and/or an acrylate ester having less than ten carbon atoms per molecule, which process comprises contacting ethylene, acrylic acid and/or said acrylate ester with carbon monoxide and hydrogen in the presence of a solvent and of a catalytic system formed by combining::a) a platinum(II) compound, b) a chelating ligand comprising an organic compound containing as coordinating atoms at least two phosphorous atoms which are connected through a divalent organic bridging group having at least two carbon atoms in the bridge, and c) a protonic acid having a pK below 3, measured at 18 "C in aqueous solution, with the exception of hydrqhalogenic acids and/or a metal salt of such a protonic acid, with the exception of a halide, said metal being a non-noble transition metal or a metal belonging to Group 4a of the Periodic Table of the Elements.

Surprisingly, the products obtained by the hydrocarbonylation according to the present invention are obtained with a selectivity which is often about 95%, whilst a high reaction rate is observed.

The selectivity to a certain compound, expressed in a percentage, is defined as 100 x a : b, in which "a" is the amount of starting compound that has been converted into that certain compound and "b" is the total amount of starting compound that has been converted.

The starting compounds in the process according to the present invention are ethylene, acrylic acid, said acrylate esters and mixtures thereof. Preference is given to ethylene, this compound showing the highest reaction rates. The process according to the invention is therefore of particular importance for the preparation of 3-pentanone. The process can be used for the conversion of acrylic acid into 4-oxo-heptanedioic acid, and the use of a mixture of ethylene and acrylic acid gives a mixture of 3-pentanone, 4-oxo-heptanedioic acid and 4-oxo-hexanoic acid.

The relevant reaction equations are:

in which R represents a hydrocarbyl group having less than seven carbon atoms and, in case a mixture of ethylene and acrylic acid is used, reactions I and II take place and also the following reaction IV:

The arylate esters are derived from an aliphatic, cycloaliphatic or aromatic alcohol having less than seven carbon atoms per molecule. Alkyl acrylates having less than seven carbon atoms in the alkyl group are most preferred, particularly methyl acrylate.

Any platinum(II) compound capable of reacting with the chelating ligand described hereinbefore to form a complex can be used in the catalytic system. Suitably, the process is carried out in a homogeneous reaction mixture. As platinum(II) compounds may be mentioned organic Pt(II) complexes and inorganic Pt(II) salts, such as platinum(II) acetylacetonate, potassium tetracyanoplatinate, potassium trichloro(ethylene)platinate(II), Pt(PhCN)2(S04)2, potassium tetrachloroplatinate(II), Pt(PPh3)2(S04)2 and Pt(COD)(S04)2 in which "Ph" and "COD" stand for "phenyl" and "1,5-cyclooctadiene", respectively. Very good results have been obtained with platinum(II) acetylacetonate.Further examples of suitable platinum(II) compounds are salts of platinum(II) with nitric acid, sulphuric acid and alkanoic acids having not more than 12 carbon atoms per molecule, for example platinum(II) acetate.

The platinum(II) compound and said protonic acid having a pK below 3 and the metal salts thereof preferably have anions which are non-coordinating, by which is meant that little or no covalent interaction takes place between the platinum and the anion of the protonic acid.

The chelating ligand preferably has the general formula I

in which R1, R2, R4 and R5 represent identical or different optionally substituted hydrocarbon groups and R3 represents a chain consisting of two to six optionally substituted methylene groups.

Any substituents present in the chelating ligand should not cause steric hindrance to the formation of complex compounds with the platinum(II) compound.

1 group R 2 4 and 5 Hydrocarbon groups R , R , R and R will as a rule contain 2 to 18 carbon atoms, preferably 6 to 14 carbon atoms. Aryl groups are the most suitable, in particular the phenyl group. Preferred bridging groups -R3 - are those having the formula -CR6R7-)- in R6 and R7 which R6 and R7 are hydrogen atoms or optionally substituted hydrocarbon groups offering no steric hindrance and n is an integer of at least two, preferably not more than 5, and most preferably 2, 3 or 4. Substituents R6 and R7 are preferably hydrogen atoms. The bridging groups R3 may also make part of a cyclic structure, e.g.

an aromatic or cycloaliphatic group, the carbon to carbon bond or bonds in the bridge may be saturated or unsaturated and in the bridge or in the cyclic or non-cyclic groups attached to the bridge one or more hetero atoms, e.g. sulphur, oxygen, iron or nitrogen atoms, may replace carbon atoms, other than the two carbon atoms which must be present in the bridge linking both phosphorus atoms.

Examples of suitable chelating ligands are 1,3-di(diphenylphosphino)propane, 1,4-di(diphenylphosphino)butane, 2,3-dimethyl-1,4-di(diphenylphosphino)butane, 1,5-di(methylphenylphosphino)pentane, 1,4-di(dicyclohexylphosphino)butane, 1,5-di(dinaphthylphosphino)pentane, 1,3-di(di-p-tolylphosphinojpropane, 1,4-di(di-p-methoxyphenylphosphino)butane, 1,2-di(diphenylphosphino)ethene, 2,3-di(diphenylphosphino)-2-butene, 1,3-di(diphenylphosphino)-2-oxopropane, 2-methyl-2-(methyldiphenylphosphino)-1,3-di(diphenylphosphino)- propane, o,o'-di(diphenylphosphino)biphenyl, 1,2-di(diphenylphosphino)benzene, 2,3-di(diphenylphosphino)naphthalene, 1,2-di(diphenylphosphino)cyclohexane, 2, 2-dimethyl-4, 5-di(diphenylphosphino) dioxolane and

Very good results have been obtained with 1,3-di(diphenylphosphino)propane.

A preferred group of acids has the general formula II

in which X represents a sulphur or a chlorine atom and, if X represents a chlorine atom, R8 represents an oxygen atom and, if X represents a sulphur atom, R8 represents an OH group or an optionally substituted hydrocarbon group.

When the hereinbefore stated acids are used in the process according to. the invention, the anions of the acids can be considered to be non-coordinating.

In the acids having the general formula II, the optionally substituted hydrocarbon group represented by R8 is preferably an alkyl, aryl, aralkyl or alkaryl group having 1-30, in particular 1-14, carbon atoms. The hydrocarbon group may, for example, be substituted with halogen atoms, in particular fluorine atoms.

Preferred acids of the general formula II are perchloric acid, sulphuric acid, p-toluenesulphonic acid and trifluoromethanesulphonic acid. p-Toluenesulphonic acid and trifluoromethanesulphonic acid are particularly preferred. Another suitable acid is 2-hydroxypropane-2-sulphonic acid. The acid of the general formula II can also be an ion exchanger containing sulphonic acid groups, such as, for example, Amberlite 252 H ("Amberlite" is a trade name). In that case, the hydrocarbon group R8 is a polymeric hydrocarbon group, for example a polystyrene group substituted with sulphonic acid groups.Further examples of suitable acids are those that can be formed, possibly in situ, by interacting a Lewis acid such as, for example BF3, AsF5, SbF5, PF5, TaF5 or NbF5 with a Broensted acid such as, for example, a hydrohalogenic acid, in particular HF, fluorosulphonic acid, phosphoric acid or sulphuric acid. Specific examples of acids of the latter type are H2SiF6, HBF4, HPF6 and HSbF6. Examples of suitable sulphonic acids are fluorosulphonic acid and chlorosulphonic acid. Other examples of suitable acids are trichloroacetic acid, trifluoroacetic acid, dichloroacetic acid and difluoroacetic acid.

The protonic acids having a pK below 3 may be used as such or a the metal salts thereof, as stated hereinbefore, may be used.

Mixtures of such acids or of such salts or of such acids and such salts may be used. Preference is given to salts of zirconium(II), tin(II), copper(II) and iron(II). Examples of other metal salts are those of scandium, yttrium, lanthanum, the lanthanides (atom numbers 58-71), titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, cobalt, nickel, zinc, germanium and lead.

The Pt(II) compound is used in a catalytic amount and the amount thereof is not critical. Usually, quantities between 10 and 10 and preferably between 10 5 and 10 mol Pt(II) compound per mol ethylene, acrylic acid and/or acrylate ester are used.

The chelating ligand can be used in quantities, relative to the Pt(II) compound, that can range within wide limits, for example from 0.1 to 10 mol per mol Pt(II) compound. Preferred quantities range from 0.3 to 3 and particularly from 1 to 3 mol per mol.

The metal salt and/or pro tonic acid that form part of the catalytic system can be used in quantities, relative to the Pt(II) compound, that can range within wide limits, for example from 0.5 to 100 mol per mol Pt(II) compound. Preferred quantities range from 1 to 20 mol per mol.

The hydrogen which is used as a starting material in the process according to the present invention may originate from an external source and added as molecular hydrogen, but, in a preferred embodiment, hydrogen is formed in situ. A preferred method to form the hydrogen in situ is allowing the process to be carried out in the presence of water; in this case the following reaction takes place in situ:

The amount of water then to be used in the process according to the present invention can vary within wide limits and is suitably between 0.005 and 5 and preferably between 0.5 and 2 mol per mol of starting ethylene, acrylic acid and/or acrylate ester.

According to another embodiment of the present invention the process is carried out in the presence of an alcohol and a catalytic amount of water, in which case the ketone formed is partly converted by the alcohol into the corresponding acetal and water. This water, in turn, reacts with further quantities of starting ethylene, acrylic acid and/or acrylate ester and carbon monoxide, forming further quantities of ketone and carbon dioxide.

This embodiment results in a mixture of ketone and acetal, which mixture may have a high acetal content. For example, ethylene is hydrocarbonylated in the presence of methanol and a catalytic amount of water with formation of 3,3-dimethoxypentane and 3-pentanone. The alcohol may be aliphatic, cycloaliphatic or aromatic; alkanols are preferred, particularly those having not more than five carbon atoms per molecule. Methanol is particularly preferred. The catalytic amount of water is suitably in the range of from 0.005 to 0.1 mol per mol of starting ethylene, acrylic acid and/or acrylate ester.

The carbon monoxide can be used in pure form or diluted with an inert gas such as nitrogen or a noble gas in the process according to the invention.

The process of this invention is preferably carried out at a temperature in the range of from 20 "C to 200 C, in particular 50 to 150 "C, and a total pressure in the range of from 2 to 100, in particular 20 to 75 bar. Suitably, a molar ratio carbon monoxide to starting ethylene, acrylic acid or acrylate ester in the range of from 0.5 to 2 is used. In general, reaction times between 1 and 20 hours appear to be adequate.

The process according to the invention is suitably carried out in the presence of a solvent, which may be protic or aprotic.

Examples of such solvents are hydrocarbons, such as hexane, heptane, octane, benzene, toluene, the three xylenes, ethylbenzene, cumene, cyclohexane and decalin; halogenated hydrocarbons, such as dichloromethane, chloroform, 1,2-dichloroethane, perfluoroalkanes, chlorobenzene and the three dichlorobenzenes; sulphones such as diethyl sulphone, diisopropyl sulphone and tetrahydrothiophene l,1-dioxide (also referred to as "sulfolane"); N,N-dialkyl-substituted amides such as N,-dimethylformamide and N-methylpyrrolidone; esters such as methyl benzoate, ethyl acetate and amyl acetate; ethers such as diethyl ether, 3,6-dioxaoctane, methyl tert.-butylether, tetrahydrofuran, diisopropyl ether, 1,4-dioxane, 2,5,8-trioxanonane (also referred to as "diglyme"), diphenyl ether and anisole. Very good results have been obtained with ethers. Acrylic acid or said acrylate ester may be used as a solvent.

The process according to the present invention may be carried out batchwise, semi-continuously or continuously. E7hen operating batchwise, the catalytic system, water and the solvent are charged to a reactor to form a liquid phase therein, the reactor is pressurized with carbon monoxide and ethylene if ethylene is used as a starting compound and the reactor is heated to the desired temperature. When operating continuously, the liquid components can be charged to the reactor continuously to form a liquid phase therein and the carbon monoxide and ethylene continuously introduced into the reactor to contact the liquid phase containing the catalyst. The gaseous reactants can be withdrawn from the reactor as a separate effluent, cooled, depressurized and the carbon monoxide and ethylene can be recycled for further contacting.

The hydrocarbonylation products may be isolated from the reaction mixture in any suitable manner, for example by means of distillation, obtaining a distillate fraction containing the hydrocarbonylation products, and a bottom fraction containing the catalytic system. Suitably, a solvent is chosen that substantially remains in the bottom fraction. Preferably, at least a portion of the bottom fraction containing solvent and catalytic system is re-used in the process according to the invention.

The invention further provides a novel catalytic system formed by combining:a) a platinum(II) compound, b) a chelating ligand comprising an organic compound containing as coordinating atoms at least two phosphorous atoms which are connected through a divalent organic bridging group having at least two carbon atoms in the bridge, and c) a protonic acid having a pK below 3, measured at 18 "C in aqueous solution, with the exception of hydrohalogenic acids and/or a metal salt of such a protonic acid, with the exception of a halide, said metal being a non-noble transition metal or a metal belonging to Group 4a of the Periodic Table of the Elements.

The following Examples further illustrate the invention.

EXAMPLES 1-5 A magnetically stirred 300 ml autoclave was charged with diglyme (50 ml), platinum(II) acetylacetonate (0.2 mmol), 1,3-di (diphenylphosphino)propane (0.3 mmol), water (5 ml, 278 mmol) and a salt or acid as indicated in Table 1 hereinafter. The autoclave was flushed with carbon monoxide, charged with carbon monoxide until a partial pressure thereof of 25 bar was reached, charged with ethylene until a partial pressure thereof of 25 bar was reached, sealed and heated to the temperature indicated in Table 1. After a reaction time of 5 h the reaction product was analyzed by means of gas-liquid mass spectroscopy. The results are presented in Table 1.

TABLE 1 Example Salt or acid, mmol Temp., Reaction rate, Selectivity OC mol 3-pentanone 3-pentanone, per mol Pt per h 1 Zr(SO4)2 1 120 150 95 2 p-toluenesul- 2 100 70 90 phonic acid 3 Sn(SO4)2 1 120 160 95 4 Cu(CF3SO3)2 1 120 100 95 5 Fe(C10 6H20 1 120 120 95 EXAMPLE 6 Example 1 was repeated with the difference that methanol (50 ml) instead of diglyme (50 ml) was used. The reaction rate was 150 mol 3-pentanone per mol platinum per h and the selectivity to 3-pentanone was 95%.

EXAMPLE 7 Example 1 was repeated with the difference that methanol (50 ml) and water (1 ml, 56 mmol) instead of diglyme (50 ml) and water (5 ml) were used. The reaction rate was 150 mol of a mixture of 3-pentanone and 3,3-dimethoxypentane per mol platinum per h and the selectivity to this mixture was more than 95%, the 3-pentanone content of this mixture being 40 %mol.

EXAMPLE 8 Example 1 was repeated with the difference that acrylic acid (20 ml, 0.29 mol) and carbon monoxide (50 bar) instead of ethylene (25 bar) and carbon monoxide (25 bar) were used. The reaction rate was 30 mol 4-oxo-heptanedioic acid per mol platinum per h and the selectivity to this acid was more than 90%.

The reaction mixture obtained in each of the eight Examples contained carbon dioxide.

Comparative Experiment A Example 1 was repeated with the difference that triphenylphosphine (1 mmol) instead of 1,3-di(diphenylphosphino)propane (0.3 mmol) was used. Hardly any reaction took place, only traces of ketone being formed.

Comparative Experiments B-H Example 1 was repeated with the difference that Zr(SO4)2 (1 mmol) was replaced with the amounts of the compounds stated-in Table 2 hereinafter.

TABLE 2 Comparative Experiment Compound Amount, mmol B none 0 C 1, 10-phenanthroline 0.4 D potassium p-tosylate 1 E SnCl2 1 F CuCl2 1 G acetic acid 2 H cupric acetate 1 In none of these cases a reaction was observed.

EXAMPLE 9 An experiment was carried out in the manner described in Examples 1-5, using 0.2 mmol platinum(II) acetylacetonate, 0.3 mmol 1,3-di(diphenylphosphino)propane, 1.0 mmol ZrSO4, 50 ml methanol, ethylene (25 bar), carbon monoxide (25 bar) and hydrogen (10 bar).

The reaction mixture was kept at 120 OC for 5 h. The reaction rate was 170 mol 3-pentanone per mol Pt per hour and the selectivity to 3-pentanone was more than 95%.

Claims (16)

1. A process for the hydrocarbonylation of ethylene, acrylic acid and/or an acrylate ester having less than ten carbon per molecule, which process comprises contacting ethylene, acrylic acid and/or said acrylate ester with carbon monoxide and hydrogen in the presence of a solvent and of a catalytic system formed by combining: a) a platinum(II) compound, b) a chelating ligand comprising an organic compound containing as coordinating atoms at least two phosphorous atoms which are connected through a divalent organic bridging group having at least two carbon atoms in the bridge, and c) a protonic acid having a pK below 3, measured at 18 OC in aqueous solution, with the exception of hydrohalogenic acids and/or a metal salt of such a protonic acid, with the exception of a halide, said metal being a non-noble transition metal or a metal belonging to Group 4a of the Periodic Table of the Elements.

2. A process as claimed in claim 1 in which only ethylene is hydrocarbonylated.

3. A process as claimed in claim 1 or 2 in which the Pt(II) compound is platinum acetylacetonate.

4. A process as claimed in any one of the preceding claims in which the chelating ligand has the general formula I

in which R, R, R4 and R5 represent identical or different, optionally substituted hydrocarbon groups and R3 represents a chain consisting of two to six optionally substituted methylene groups.

5. A process as claimed in claim 4 in which the chelating ligand is 1, 3-di (diphenylphosphino) propane.

6. A process as claimed in any one of the preceding claims in which the protonic acid has the general formula II

in which X represents a sulphur or chlorine atom and, if X represents a chlorine atom, R8 represents an oxygen atom and, if X 8 represents a sulphur atom, R represents an OH group or an optionally substituted hydrocarbon group.

7. A process as claimed in claim 6 in which the protonic acid is p-toluenesulphonic acid or trifluoromethanesulphonic acid.

8. A process as claimed in any one of the preceding claims in which the metal salt is a salt of zirconium, tin, copper or iron.

9. A process as claimed in any one of the preceding claims which is carried out at a temperature in the range of from 20 OC to 200 OC and a pressure in the range of from 2 to 100 bar.

10. A process as claimed in any one of the preceding claims in which the hydrogen is formed in situ.

11. A process as claimed in claim 10 in which the hydrogen is formed in situ by the presence of water.

12. A process as claimed in claim 11 in which an alcohol and a catalytic amount of water are present.

13. A process as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.

14. Hydrocarbonylation products whenever prepared by a process as claimed in any one of the preceding claims.

15. A catalytic system formed by combining:a) a platinum(II) compound, b) a chelating ligand comprising an organic compound containing as coordinating atoms at least two phosphorous atoms which are connected through a divalent organic bridging group having at least two carbon atoms in the bridge, and c) a protonic acid having a pK below 3, measured at 18 OC in aqueous solution, with the exception of hydrohalogenic acids and/or a metal salt of such a protonic acid, with the exception of a halide, said metal being a non-noble transition metal or a metal belonging to Group 4a of the Periodic Table of the Elements.

16. A catalytic system substantially as hereinbefore described with reference to the Examples.