EA024478B1 - Catalytic system and its use for the manufacture of vinyl chloride by hydrochlorination of acetylene - Google Patents

Abstract

Catalytic system comprising: a) at least one N-alkylated imidazole and b) at least one compound of at least one metal selected from Pd, Pt, Hg, Ru and Os, and its use in the hydrochlorination reaction of acetylene with hydrogen chloride.

Description

The present invention relates to a catalytic system, which is particularly useful in a method for the production of vinyl chloride by hydrochlorination of acetylene. The present invention also relates to such a method.

The production of vinyl chloride by the reaction between acetylene and hydrogen chloride is traditionally carried out in the gas phase using a fixed-bed reactor in the presence of a heterogeneous solid mercury chloride catalyst on a support. Mainly due to toxicity reasons, there is currently increasing interest in catalytic systems that have a reduced mercury content or that do not contain mercury compounds.

A variety of catalysts have been developed to replace the catalysts currently used in gas phase processes.

For example, Japanese Patent Application 52/136104, which has not passed examination, describes a method for hydrochlorinating acetylene in the gas phase in the presence of a fixed catalyst bed consisting of noble metal halides supported on activated carbon. However, to date, the service life of such alternative catalysts for gas phase processes has remained significantly shorter than the service life of mercury based catalysts.

In addition, some examples of acetylene hydrochlorination in the presence of a liquid catalyst medium are presented in the literature.

German patent 709000 describes a method for producing vinyl halides by contacting acetylene at high temperatures with a molten mass of hydrohalide salts of organic bases containing a standard catalyst. Aliphatic, aromatic or heterocyclic amines and mixtures thereof are provided as organic bases.

USSR author's certificate 237116 describes the use of an aqueous acidic solution containing 46 wt.% Copper chloride (4) and from 14 to 16 wt.% Methylamine, dimethylamine or trimethylamine hydrochloride.

European patent application EP-A-0340416 describes a method for producing vinyl chloride by reacting acetylene with hydrogen chloride in the presence of a palladium compound as a catalyst in a solvent representing an aliphatic or cycloaliphatic amide at a temperature above ambient temperature. Although this method allows to obtain high yields, it, however, has some significant disadvantages: it was found that under the reaction conditions the liquid catalytic system gradually decomposes, forming blackish products similar to coal. In addition, in the presence of hydrogen chloride, the amide is converted to hydrochloride, the melting point of which, as a rule, significantly exceeds the ambient temperature. Ν Methylpyrrolidone hydrochloride, for example, becomes liquid only above 80 ° C. In practical implementation, this can cause serious problems associated with agglomeration of the catalytic medium during reactor shutdowns or blocking of pipelines at the coldest points of the installation. The entire reactor, as well as the pipelines in which the reaction medium flows, must be constantly maintained at a temperature above the melting point of the hydrochloride.

These various problems seemed to be solved thanks to the catalytic hydrochlorination systems that are described in European patent applications EP 0519548-A1 and EP 0525843-A1 and which include at least one group VIII metal compound and an amine hydrochloride whose melting point is less than or equal to 25 ° C, or a fatty amine hydrochloride containing more than 8 carbon atoms, the melting point of which is more than 25 ° C, and an organic solvent selected from aliphatic, cycloaliphatic and ar matic hydrocarbons and mixtures thereof. However, the catalyst systems described in these applications, in particular those in which the group VIII metal compound is platinum chloride (11) or palladium (P) chloride, are not fully satisfactory when considering the characteristics that they allow obtain in terms of production efficiency of vinyl chloride by hydrochlorination of acetylene and in relation to long-term stability.

International Patent Application DOO 2008/77868 describes a catalytic hydrochlorination system comprising at least one amine hydrochloride and at least one Group VIII metal compound selected from the group consisting of mixtures of platinum compounds DU) with chloride 8i (P), mixtures of platinum compounds ( P) with triphenylphosphine oxide and mixtures of the palladium compound (P) with triphenylphosphine. These catalytic systems exhibit improved performance compared to the systems described in European patent applications EP-A 0519548 and EP-A 0525843.

Finally, Chinese patent application No. 101716528 describes catalytic systems for the production of vinyl chloride by acetylene hydrochlorination, including an imidazolium-based ionic liquid containing chloride, bromide, hexafluorophosphate or tetrafluorophosphate ions as anions, as well as one or more gold, platinum, palladium, tin chlorides mercury, copper, or rhodium.

The latter catalyst systems mentioned above have the disadvantage of requiring an amine hydrochloride or ionic liquid in combination with a metal compound.

Accordingly, it was an object of the present invention to provide a catalytic system 1,024,478, in particular for hydrochlorination reactions and, more specifically, for acetylene hydrochlorination, which is as simple and cheap as possible and provides very good performance. Another objective of the present invention was to provide a method for the synthesis of vinyl chloride by hydrochlorination of acetylene in the presence of such a catalyst system that does not decompose under the reaction conditions and which makes it possible to achieve very good vinyl chloride performance. In contrast to systems based on mercury compounds, the catalytic system according to the present invention also has the advantage of avoiding the toxicity problems associated with these compounds and preventing the evaporation of metal salts in the installation.

Thus, the present invention relates to a catalyst system, and more particularly, to a catalyst system for hydrochlorination of acetylene, as defined in claim 1.

Preferred embodiments of the catalyst system in accordance with the present invention are set forth in claims dependent on claim 10 and are described in more detail later in this document.

Another aspect of the present invention relates to a method for the production of vinyl chloride using the acetylene hydrochlorination reaction in the presence of a catalyst system, as defined in claim 1 and in the claims dependent on claim 1, and is described in more detail later in this document.

The catalytic system according to the present invention includes:

a) at least one Ν-alkylated imidazole and

b) optionally at least one compound of at least one metal.

Catalytic systems including:

a) at least one Ν-alkylated imidazole and

b) at least one compound of at least one metal selected from Pb, Ρΐ, Nd, Ki and 08 are new and provide good results in the framework of the present invention, especially if the metal is Pb.

The expression includes in the present description should be understood as meaning that in addition to at least one Ν-alkylated imidazole and optionally at least one compound of at least one metal, the catalytic system according to the present invention may include additional component (s) that affect the catalytic properties of the catalytic system or not. Among these additional components, ionic liquid (s) can be noted, which are introduced, for example, in order to influence the catalytic properties of the catalytic system and / or to reduce the viscosity of the catalytic system.

Preferably, the catalytic system according to the present invention consists mainly of:

a) at least one Ν-alkylated imidazole and

b) optionally at least one compound of at least one metal.

The expression consists primarily of the present description as meaning that in addition to at least one Ν-alkylated imidazole and optionally at least one compound of at least one metal, the catalyst system of the present invention may include additional component (s), preferably in a small the amount that do not affect the catalytic properties of the catalytic system, which do not produce a catalytic effect on the reaction, during Ora used catalytic system. Among these additional components can be noted ionic liquid (s), which are introduced, for example, to reduce the viscosity of the catalytic system.

More preferably, the catalyst system of the present invention consists of:

a) at least one Ν-alkylated imidazole and

b) optionally at least one compound of at least one metal.

The expression consists in the present description should be understood as meaning that the catalyst system consists solely of at least one рованного-alkylated imidazole and optionally at least one compound of at least one metal.

The catalyst system according to the present invention includes, as component (a), at least one Ν-alkylated imidazole.

In the present description, the expression of at least one Ν-alkylated imidazole should be understood as meaning one or more than one Ν-alkylated imidazole.

Preferably, the catalyst system comprises one один-alkylated imidazole.

In the rest of the text, the expression Ν-alkylated imidazole when used in the singular or plural is to be understood as meaning one or more than one alkylated imidazole, unless otherwise specified.

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Ν-Alkylated imidazoles according to the present invention are mainly defined by the following formula (I)

in which the radicals K ¹ , K ² , K ³ and K ⁴ can independently of each other, each represent hydrogen or an optionally substituted saturated or unsaturated alkyl group C ₁ -C ₁₈ (preferably C ₁ -C ₁₄ , preferably C ₁ - C ₁₂ , most preferably C ₁ -C ₁₀ and particularly preferably C ₁ -C ₈ ).

Examples of Ν-alkylated imidazoles are 1-methylimidazole, 1-ethylimidazole, 1 propylimidazole, 1-butylimidazole, 1-pentylimidazole, 1-hexylimidazole, 1-heptylimidazole, 1 octylimidazole-1-nonylimidazole-1-nonylimidazole-1-nonimidazole-1 , 1-ethyl-2-methylimidazole, 1-butyl-2-methylimidazole, 1-hexyl-2-methylimidazole and 1-decyl-2-methylimidazole.

Preferably, the Ν-alkylated imidazole is selected from 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-octylimidazole, 1-decylimidazole, 1-methyl-2-octylimidazole, 1-ethyl-2-methylimidylazole -2-methylimidazole, 1-hexyl-2-methylimidazole and 1-decyl-2methylimidazole.

Preferred as Ν-alkylated imidazole are those used in the working examples presented later in this document, i.e. 1-methylimidazole, 1-ethylimidazole and 1-butylimidazole. These most preferred Ν-alkylated imidazoles are commercially available from, for example, ΛΟπΟι®.

Methods for the production of suitable alkylated imidazoles are known to those skilled in the art, and thus a detailed description thereof is not required herein.

The catalyst system of the present invention includes, as component (b), at least one compound of at least one metal.

As used herein, the expression of at least one compound of at least one metal includes one compound of one metal, as well as mixtures of various compounds of one metal or mixtures of compounds of various metals or compounds comprising two metals, as defined hereinabove , i.e. The catalyst systems of the present invention may include several metals and, accordingly, metal compounds as defined above.

Preferably, the catalyst system comprises one compound of at least one metal, and more preferably one compound of one metal.

In the rest of the text of the expression, a compound and a metal, when used in the singular or plural, should be understood as meaning respectively one or more than one compound and one or more than one metal, unless otherwise specified.

In the present description, the expression optionally includes at least one compound to be understood as meaning that such a compound is present or not in the catalyst system.

According to a first embodiment of the present invention, component (b) is not included in the catalyst system of the present invention, i.e. at least one compound of at least one metal.

The definitions and preferences presented above also apply to this first embodiment.

According to a second embodiment of the present invention, the catalytic system according to the present invention mainly includes:

a) at least one Ν-alkylated imidazole and

b) at least one compound of at least one metal.

The definitions and preferences presented above also apply to this second embodiment.

The catalyst system of the present invention optionally includes at least one compound of at least one metal as component (b).

The metal may be any metal. The metal is preferably selected from Ρά, Ρΐ, Au, Nd, Ki, Οδ, Ki, KN and 1 g. Preferably, the metal is selected from Ρά, Ρΐ, Au, Nd, Ki and Οδ.

Thus, the catalytic system according to the present invention preferably includes:

a) at least one Ν-alkylated imidazole and

b) at least one compound of at least one metal selected from Ρά, Ρΐ, Au,

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Nd, Ki and Θδ.

Although good results were obtained when the metal was selected from the above, very good results were obtained when the metal was selected from P6, Ki, Au and Οδ, especially good results were obtained when the metal was selected from P6, Ki and Au, and, in particular, very good results were obtained when the metal was selected from P6 and Ki. The most interesting results were obtained when the metal was P6.

Preferred compounds PKA), RCP) or P6 (P) are those that can be converted to the chlorides of the corresponding metals during the manufacture of the catalytic system in accordance with the present invention. Thus, chlorides, nitrates, acetates, carbonates or oxides of platinum (IV), platinum (11) or palladium (11) can be used. However, chlorides and acetates of these metals are preferred.

Among the platinum (A) compounds having a chloride base, mention may be made of platinum chloride (A) and hexachloroplatinic acid or its salts, for example No.-bP1C1 ₆ . K ₂ R1C1 ₆ or S ₂ RJ1 ₆ .

Among platinum compounds having a chloride base (11), platinum chloride (11) and alkali metal or alkaline earth metal tetrachloroplatinates can be mentioned, such as, for example, Xa ₂ (P1C1 ₄ ), K ₂ (P1C1 ₄ ), P ₂ (P1C1 ₄ ) and (ΝΗ ₄ ) ₂ (Р1С1 ₄ ).

Among the palladium compounds (11) having a chloride base, mention may be made of palladium chloride (11) and tetrachloropalladates of alkali metals or alkaline earth metals, such as, for example, No. ₂ (P6C1 ₄ ), K ₂ (P6C1 ₄ ), N ₂ (P6C1 ₄ ) and (ΝΗ ₄ ) ₂ (Р6С1 ₄ ).

It is particularly preferable to choose PY1 ₄ , PY1 ₂ , P6C1 ₂ and palladium (II) acetate as the compounds of platinum / A), platinum (11) and palladium (11), respectively. Most preferred are PY1 ₂ , P6C1 ₂ and palladium acetate (11).

Among the compounds, gold compounds An ³ 'are preferred and, similarly to the cases of P6 and P1, those compounds which can be converted to chlorides are more preferred. Most preferred is AuCl ₃ .

Suitable compounds Ki and Οδ are those in which these metals are trivalent, and again compounds that can be converted into chlorides or chlorides themselves are more preferred. Most preferred are CuCl ₃ and 0δ ₃ .

Among suitable mercury compounds, NdC1 ₂ can be mentioned.

The content of the metal compound in the catalytic system according to the second embodiment, expressed in millimoles per 1 liter of Ν -alkylated imidazole, is preferably more than or equal to about 1 mmol / l and less than or equal to about 1000 mmol / l. The content of metal compounds in the catalyst system according to the second embodiment is preferably greater than or equal to approximately 1 mmol / L, preferably greater than or equal to approximately 5 mmol / L, and particularly preferably greater than or equal to approximately 10 mmol / L. The content of the metal compound in the catalyst system is preferably less than or equal to approximately 1000 mmol / L, preferably less than or equal to approximately 800 mmol / L, particularly preferably less than or equal to approximately 600 mmol / L, even more preferably less than or equal about 500 mmol / L, and most particularly preferably less than or equal to about 400 mmol / L. Although not required, it is generally considered preferable that all metal compounds that include the catalyst system are in dissolved form.

Typically, a catalyst system in accordance with a second embodiment of the present invention, when used in hydrogen chloride hydrochlorination reactions, is made by dissolving or dispersing a desired amount of a metal compound in a Ν-alkylated imidazole, and then saturating the resulting solution with hydrogen chloride. However, it is also possible to first saturate the алки-alkylated imidazole with hydrogen chloride, and then introduce the metal compound into the Ν alkylated imidazole. A commonly used amount of a metal compound in a catalyst system is such that the entire metal compound is in dissolved form. However, you can also use a metal compound of this nature or in such an amount that at least one fraction of this compound is present in the catalyst system in the form of a dispersed solid, without violating the conditions of the present invention.

The catalyst system in accordance with the first and second embodiments of the present invention can be used in the liquid phase or applied to a solid carrier such as silica, alumina, silica and alumina, cordierite, mullite or activated carbon (only some suitable materials are listed here -carriers), up to the limit of pore volume and accessible surface of the carrier. The carrier may take any form known for such carrier materials, including, but not limited to, cells and extrudates or similar forms.

When the catalyst system is used in the liquid phase, it can be diluted with an organic solvent. The choice of the nature of the organic solvent incorporated in such a case into the catalyst system of the present invention definitely depends on the requirement that it be

- 4 024478 which is inert with respect to the reagents under the reaction conditions, so that it can be mixed with an alkylated imidazole, and from the desire that it form a medium with this Ν-alkylated imidazole, whose viscosity is lower than the viscosity of pure Ν-alkylated imidazole.

Preferably, however, the Ν-alkylated imidazole itself serves as a solvent, so that no additional solvent is required.

The catalyst system of the present invention can be used for any reaction with alkyne, i.e. a compound in which two carbon atoms are connected via a triple bond. Among such alkynes, acetylene, propine, also called methylacetylene, dimethylacetylenedicarboxylate, 1,4-butynediol, as well as propargyl compounds can be noted. The reaction may be hydrohalogenation, in particular hydrochlorination (with hydrogen chloride), hydroiodination (with hydrogen iodide), hydrofluorination (with hydrogen fluoride) or hydrobromination (with hydrogen bromide), or with phosphorous acid.

The catalyst system of the present invention is particularly useful for hydrochlorinating acetylene.

In the present description, the term acetylene should be understood as acetylene or mixtures comprising acetylene, which may, in addition to acetylene, include other components, for example ethylene or other unsaturated hydrocarbons, which may be by-products of acetylene synthesis. The origin of such mixtures of various unsaturated compounds can be any known source of reaction mixtures that can be obtained by known methods for the synthesis of acetylene. Mixtures comprising less than 50% acetylene may be used. However, the term acetylene means mixtures comprising preferably at least 90% acetylene and more preferably 100% acetylene.

Acetylene is produced mainly by the partial combustion of methane, or it forms as a by-product in the ethylene stream after cracking of hydrocarbons.

Another method for producing acetylene is the hydrolysis of calcium carbide

CaC; -2H _; O> Ca (OH) _; -C; H _; .

for which extremely high temperatures of approximately 2000 ° C are required, which determines the mandatory use of an electric furnace or similar device.

Mixtures including acetylene and ethylene can be used directly unchanged, i.e. there is no need to separate the components, since the reactivity of acetylene compared with ethylene ensures that acetylene hydrochlorination is carried out in the first place, followed by separation of the resulting vinyl chloride and further use of ethylene. This ethylene can be chlorinated to give 1,2-dichloroethane for the combined process for the production of vinyl chloride monomer. By pyrolysis of 1,2-dichloroethane, hydrogen chloride can be produced for the first reaction with acetylene.

Thus, the present invention also relates to a method for the production of vinyl chloride by the reaction of acetylene with hydrogen chloride (hydrochlorination) in the presence of a catalyst system in accordance with the present invention.

The definitions and preferences presented above for the catalytic system according to the present invention apply to the method of producing vinyl chloride according to the present invention.

The method according to the present invention can advantageously be carried out at a temperature in the range from room temperature to 220 ° C. At higher temperatures, the catalytic system tends to decompose. The preferred reaction temperature, in other words, one that provides the best compromise between productivity, yield and stability of the catalytic medium, is more than or equal to about 40 ° C. Best results are obtained at temperatures that are greater than or equal to approximately 50 ° C, with more preferred temperatures being greater than or equal to approximately 80 ° C, and most particularly preferred temperatures are greater than or equal to approximately 120 ° C. Preferably, the reaction temperature does not exceed about 200 ° C. In particular, a reaction temperature of from about 40 to about 200 ° C is most preferred. In certain cases, the reaction temperature not exceeding 170 ° C is preferable.

The method according to the present invention is preferably carried out at atmospheric pressure or at higher pressures that comply with safety rules when working with acetylene. Typically, the partial pressure of acetylene does not exceed 5 MPa, preferably it does not exceed 2.5 MPa.

The method for producing vinyl chloride by hydrochlorination of acetylene according to the present invention is advantageously carried out in any suitable reactor by introducing gaseous reactants (acetylene and hydrogen chloride) into contact with the catalyst system.

The method according to the present invention can be carried out traditionally using any equipment that provides exchange between the gas and liquid phases, such as a disk column,

- 5,024,778 a flooded packed column or a flooded non-packed column. Another embodiment of the method, which provides a good exchange of matter between the liquid and gas phases, is to use a countercurrent reactor, optionally an irrigated packed bed, where the liquid catalyst system moves over the nozzle countercurrent to a stream of gaseous reactants.

In the method according to the present invention, the molar ratio of hydrogen chloride to acetylene introduced into the reactor is advantageously greater than or equal to approximately 0.5. Preferably, this ratio is greater than or equal to about 0.8. Advantageously, this molar ratio is less than or equal to about 3. Preferably, the molar ratio of hydrogen chloride and acetylene introduced into the reactor is less than or equal to about 1.5.

Good results were obtained when hydrogen chloride and acetylene were used in a molar ratio of from about 0.5 to about 3.

Acetylene and hydrogen chloride can be contacted in the reactor, or preferably they can be mixed before being introduced into the reactor.

For the purpose of increasing the amount of acetylene dissolved in the liquid phase, a method can also be used in which only acetylene in gaseous form is introduced into the reactor, where acetylene reacts with hydrogen chloride present in the form of hydrochloride in the liquid phase. Hydrogen chloride can be introduced in any form, including dilute gas, pure gas or a solution in a solvent, which is then to be extracted, for example, insoluble amine, mainly by intermediate substances during operation.

The catalyst system in accordance with the present invention can advantageously be used in the production of vinyl chloride by the method in accordance with the present invention.

Thus, the present invention also relates to the use of the catalyst system according to the present invention for the catalytic hydrochlorination of acetylene and the production of vinyl chloride.

The catalytic system in accordance with the present invention provides very good performance in terms of conversion and selectivity and, thus, also improves productivity and is characterized by long-term stability. By avoiding the use of mercury compounds, the catalyst system of the present invention also has the advantage of not having toxicity problems associated with these compounds.

The following examples are intended to illustrate the present invention without limiting, however, its scope. The examples denoted by the letter C are comparative examples, while other examples describe the catalytic systems in accordance with the present invention.

General procedure for working examples.

In a pyrex glass reactor (Rugeh), having an internal volume of 45 ml, equipped with a double jacket in which the oil circulates as a coolant, and a device for introducing reagents, which is a sintered glass nozzle designed to ensure dispersion of gases in a liquid medium, 30 ml of appropriate solutions, including catalytic systems, manufactured as described later in this document. The reactor was kept at a temperature of 150 ° C.

Reagents (acetylene and HC1) were introduced at a molar ratio of 1: 1.2 in quantities of 10 Nl / h and 12 Nl / h (measured at 0 ° C and atmospheric pressure).

Ν-Alkylated imidazole was used as obtained. When it was present in the catalyst system, said metal compound was dissolved in the required amount in the used Ν-alkylated imidazole. The amount of metal, unless otherwise specified, was 22.6 mmol / L of ionic liquid.

The effluent from the reactor was analyzed to determine the conversion of acetylene. The selectivity was 100% in all experiments, i.e. in addition to vinyl chloride, which was the target product, there were no by-products. Thus, productivity could be calculated directly from acetylene conversion.

The following Ν-alkylated imidazoles were analyzed and recorded in a table that summarizes the investigated catalyst systems:

ΙΜ1 - 1-methylimidazole,

ΙΜ2 - 1-butylimidazole,

ΙΜ3 - 1-ethylimidazole.

The experimental results are presented in the following table and / or illustrated in FIG. 1 and 2, which demonstrate the conversion of acetylene (%) versus time (time in hours is shown on the x-axis). The number next to the curve indicates the number of the corresponding example.

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Examples 1-14

Example Number Ionic liquid Metal compound Result one ΙΜ1 / FIG. one 2 ΙΜ2 / FIG. one 3 ΙΜ3 / FIG. one 4 ΙΜ1 RyS1 ₂ FIG. 2 5 ΙΜ2 RyS1 ₂ FIG. 2 b’’ ΙΜ2 P1C1 ₂ FIG. 2 7 ΙΜ2 AiS FIG. 2 8 ΙΜ3 RyS1 ₂ FIG. 2 nine* ΙΜ3 P1C1 ₂ FIG. 2 10 ΙΜ3 AiS FIG. 2 eleven ΙΜ3 KISS FIG. 2 12 ΙΜ3 Oats fig 2 thirteen ΙΜ3 Ry (OAc) ₂ FIG. 2 14* ΙΜ3 n ₈ smiling FIG. 2

*: The amount of metal 22.6 was increased to 67.8 mmol / L during the experiment.

#: The amount of metal is 354 mmol / L.

The experimental results show that a very good conversion was obtained using the catalytic systems according to examples 1-14.

Claims (14)

CLAIM 1. A method for the production of vinyl chloride by the reaction of acetylene with hydrogen chloride in the presence of a catalytic system comprising at least one Ν-alkylated imidazole. 2. The method according to claim 1, in which the алки-alkylated imidazole is defined by formula (I) where the radicals K ¹ , K ² , K ³ and K ⁴ can independently of each other, each represent hydrogen or a saturated or unsaturated alkyl group C _1- C ₁₈ . 3. The method according to claim 2, in which the Ν-alkylated imidazole is selected from 1-methylimidazole, 1 ethylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-octylimidazole, 1-decylimidazole, 1-methyl-2-octylimidazole, 1-ethyl-2- methylimidazole, 1-butyl-2-methylimidazole, 1-hexyl-2-methylimidazole and 1decyl-2-methylimidazole. 4. The method according to claim 3, in which the алки-alkylated imidazole is selected from 1-methylimidazole, 1ethylimidazole and 1-butylimidazole. 5. The method according to claim 1, not including any metal compound. 6. The method according to claim 1, in which the catalytic system includes: a) at least one Ν-alkylated imidazole and optionally b) at least one compound of at least one metal. 7. The method according to claim 6, in which the metal is selected from Pu, P1, Au, Nd, Ki and 08. 8. The method according to claim 7, in which the metal is PY. 9. The method according to claim 1, in which the reaction is carried out at a temperature in the range from room temperature to 220 ° C. 10. The catalytic system for use in the method according to claims 1 to 9, including: a) at least one Ν-alkylated imidazole and b) at least one compound of at least one metal selected from Pu, P1, Nd, Ki and 08. 11. The catalytic system of claim 10, in which the рованный-alkylated imidazole is defined by formula (I) - 7 024478 where the radicals K ¹ , K ² , K ³ and K ⁴ can independently of each other, each represent hydrogen or a saturated or unsaturated alkyl group C ₁ -C ₁₈ . 12. The catalytic system according to claim 11, in which the Ν-alkylated imidazole is selected from 1 methylimidazole, 1-ethylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-octylimidazole, 1decylimidazole, 1-methyl-2-octylimidazole, 1-ethyl-2 methylimidazole, 1-butyl-2-methylimidazole, 1hexyl-2-methylimidazole and 1-decyl-2-methylimidazole. 13. The catalytic system according to item 12, in which the алки-alkylated imidazole is selected from 1 methylimidazole, 1-ethylimidazole, 1-butylimidazole. 14. The catalytic system of claim 10, in which the metal is PY