JPS5822094B2 - Method for manufacturing ethyl esters - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing esters.

In particular, it relates to a method for producing ethyl esters by reacting carboxylic acid with ethylene.

It has been known for many years that carboxylic acids add to olefins in the presence of acid catalysts.

Although the advantages of this method of synthesizing esters compared to traditional methods using alcohol and inorganic acid catalysts in the liquid phase were immediately recognized, this method is difficult, especially when it is desired to obtain ethyl esters. Therefore, it remains an unusual laboratory method.

Indeed, previous studies (Ind- & Eng, Che
rn-.

1951.43, P, 1596-1600 and J-A
ppl-Chem, 1963, P, 544-54
7) As shown, ethylene can only be esterified by carboxylic acids in the presence of acid catalysts under extremely harsh conditions.

These extremely harsh conditions encourage secondary reactions, especially polymerization reactions, which occur at the expense of the desired ester.

One object of the present invention is to provide an improved method for producing ethyl esters in high yields by reacting ethylene with carboxylic acids.

Another object of the present invention is to carry out the esterification of ethylene, which is known to be difficult, under much less harsh conditions and to make the process more economical on an industrial scale.

The research which has led to the present invention has shown that it is possible to operate under relatively mild conditions, in a liquid phase and in the presence of at least one acid catalyst, in certain solvents as defined below. It was found that ethyl esters were obtained in good yields, resulting in easy application of the method on an industrial scale.

Research has shown that this process can be achieved by a remarkable combination of the use of acid catalysts and the presence of special types of solvents and, in contrast to the prior art, this process for various carboxylic acids. It turns out that the method can be done successfully.

Ethyl esters are therefore prepared from ethylene by reacting ethylene in the liquid phase with a mixture consisting essentially of a carboxylic acid, an acid catalyst, and at least one dissociative solvent capable of increasing the acidity of the medium. We now know that it can be manufactured.

Furthermore, the solvent must be stable under the reaction conditions, especially in acid media and at high temperatures.

Furthermore, the solvent must be inert under the reaction conditions and must not itself react with either the reactants or the products.

It has been found that non-basic organic compounds having a dielectric constant of the order of at least 25 are particularly suitable for carrying out the method of the invention.

Examples of solvents that can be used within the scope of the invention include:
Mention may be made of nitrobenzene, dimethylsulfone, tetramethylenesulfone and also its derivatives such as 3-methyltetramethylenesulfone, 2,4-dimethyltetramethylenesulfone and dichlortetramethylenesulfone.

Tetramethylene sulfone and its derivatives are particularly suitable for carrying out the method of the invention.

The present invention also contemplates the use of mixtures of these solvents as long as they are compatible.

In particular, mixtures of tetramethylene sulfone and its derivatives can be used.

This reaction takes place in an essentially anhydrous medium.

According to the present invention, the choice of carboxylic acid used will quite obviously depend on the type of ethyl ester desired.

Examples of carboxylic acids that can be used within the scope of the present invention include those having up to 20 carbon atoms in the molecule, substituents,
Saturated or unsaturated aliphatic acids, especially those having one or more halogen atoms, especially acetic acid, propionic acid, butyric acid, isobutyric acid, hexanoic acid, monochloroacetic acid, dichloroacetic acid, bromoacetic acid, chloropropionic acid, acrylic acid, and methacrylic acid.

The present invention also relates to aromatic acids, especially cycloaliphatic acids such as benzoic acid, toluic acid, naphthenic acid, aliphatic diacids having 3 to 6 carbon atoms in the molecule, especially succinic acid, adipic acid, and aromatic diacids, particularly phthalic acid.

Within the scope of the process according to the invention, the catalysts used are inorganic acids or strong organic acids.

Examples of catalysts that can be used within the scope of the invention include sulfuric acid, alkanesulfonic acids, especially methanesulfonic acid and its higher homologues with up to 6 carbon atoms, arylsulfonic acids, especially benzenesulfonic acid, p-toluene Sulfonic acids, benzene disulfonic acid and hinaphthalene disulfonic acid, fluorosulfonic acid, and alkylhalogen sulfonic acids, especially polyfluoroalkanesulfonic acids and perfluoroalkanesulfonic acids having at least 8 carbon atoms in the molecule. can be mentioned.

The present invention also contemplates the use of these acids as catalysts, particularly in the form of lower alkyl esters having 1 to 4 carbon atoms in the alkyl group, more particularly in the form of ethyl esters.

The present invention also contemplates the use of mixtures of these catalysts.

According to a preferred variant of the invention, the acid catalyst used is a perfluoroalkane sulfonic acid or has at most 8 carbon atoms in the molecule and optionally partially or fully in the alkyl group, in particular 1 to 4 carbon atoms. A mixture of several perfluoroalkane sulfonic acids in the form of their lower alkyl esters having 5 carbon atoms, more particularly ethyl esters, is contemplated.

Trifluoromethanesulfonic acid and/or its lower alkyl esters having in particular 1 to 4 carbon atoms in the alkyl group are particularly suitable for carrying out the process of the invention.

Trifluoromethanesulfonic acid and/or its ethyl ester are specifically contemplated.

The process according to the invention is particularly advantageous for producing ethyl acetate from ethylene and acetic acid, especially when tetramethylene sulfone and/or its derivatives are used as solvent.

In addition to its efficiency, the method shows the advantage that all or part of the reaction medium can be recycled.

In fact, at the end of the reaction, the ethyl acetate can be separated off by any suitable means and the catalyst, solvent and, if necessary, all or part of the unreacted acetic acid recycled.

The research that led to the present invention shows that the efficiency of the process in question is not essentially affected by the fact that all or part of the catalyst and solvent are subjected to recycling operations.

At the end of the first operation, the ethyl acetate produced is separated by any suitable means for the purpose of recovery and the remaining mixture is removed in a subsequent operation without the need to separate the components of the mixture and/or to purify them beforehand. can be recirculated.

The mixture thus obtained essentially contains catalyst, solvent and possibly unreacted acetic acid.

If, in a subsequent operation, ethylene is reacted with this mixture in the presence of acetic acid, even with several successive recycling operations, further acetic acid is produced with almost the same yield as that observed in the first operation. Get ethyl.

According to a preferred modification of the invention, an amount of fresh acetic acid is added during the recirculation operation which approximately corresponds to the amount converted in the previous operation.

Fresh acetic acid can be added to the recycle stream K or, for example, directly to the reactor.

The process of the invention essentially comprises at least one carboxylic acid, at least one acid catalyst and at least one acid catalyst, the properties of which are defined above, in a liquid phase.
The ethyl esters are obtained by reacting with a mixture containing the species solvent.

According to a preferred variant of the invention, a solvent and a carboxylic acid,
ie the relative amount of solvent, defined as the mole fraction f of the solvent in the mixture of acids constituting the acid portion of the desired ethyl ester, is greater than or equal to 0.4.

The amount of catalyst added to the reaction medium is not critical.

Generally, an amount between 0.05 and 2 mol per 11 of the reaction mixture is sufficient.

This amount is preferably between 0.1 and 1 mol/l.

Ethylene pressure must be greater than atmospheric pressure.

Pressures between 20 and 60 bar are particularly suitable for carrying out the invention.

Reaction temperature is not critical.

However, when the temperature was lower than 100°C, the reaction rate was slow, whereas when the temperature was higher than 200°C, secondary products due to decomposition were observed.

Preferably, the temperature is between 130 and 160°C.

The following examples illustrate how the method of the invention is carried out.

EXAMPLES Examples 1-7 Acetic acid, tetramethylene sulfone (TMS) and catalyst are placed in a 250J Hastelloy C bomb.

The mixture is heated in a furnace to the selected temperature while stirring longitudinally.

Ethylene was then passed through.

Unless otherwise stated, the ethylene pressure is 40 bar.

Unless otherwise specified, reactions are stopped after 4 hours.

The results obtained, expressed as conversion of acid to ethyl acetate (DC), and the specific conditions are shown in Table 1 below.

The last column shows the conversion of acid to ethyl acetate (DC8) obtained in the absence of tetramethylene sulfone with all other conditions being the same.

Note, in these examples, and all examples below, the selectivity for the desired ester is on the order of 100 parts.

(*) This experiment was conducted for 2 hours and 30 minutes using 30 bar ethylene pressure.

(-) This experiment was carried out using 10 g of perfluorosulfonic acid, commercially available under the trademark NAFION (duration of experiment 3 hours).

This resin includes a copolymer of perfluoroethylene and perfluorovinyl ether having sulfonic acid groups.

In this last column (DCo%), ε indicates that it cannot be measured (extremely small), and - indicates that it is not measured.

Examples 8-14 Acetic acid, trifluoromethane, according to the general method described above.
Add sulfonic acid and solvent.

The specific conditions and results obtained are shown in Table 2, Table 4 below.

In the table, MTMS stands for 3-methyltetramethylene sulfone, DMTMS stands for 2,4-dimethyltetramethylene sulfone, DMS stands for dithyl sulfone, NB stands for nitrobenzene, and TMS stands for tetramethylene sulfone.

Examples 15-17 Ethylene was converted to carboxylic acid (RC
OOH) to form various ethyl esters (RCOO
C2H2) was produced.

This reaction was carried out in the presence of trifluoromethanesulfonic acid as a catalyst.

The results obtained after the specific conditions and reaction time of 4 hours are shown in Table 3 below.

Examples 18 to 22 Various experiments were carried out for the production of ethyl acetate by reacting ethylene (40 bar pressure) with acetic acid using trifluoromethanesulfonic acid as a catalyst in a medium containing various proportions of tetramethylene sulfone according to the general procedure described above. An experiment was conducted.

The reaction temperature was 1500℃ and the reaction time was 4 hours.

The specific conditions and results obtained are shown in Table 4 below.

In the table, f indicates the ratio of the number of moles of the solvent to the total number of moles of the solvent and carboxylic acid.

*This experiment was conducted at 110'C.

**This experiment was carried out using an ethylene pressure of 20 bar.

Example 23 44. C9 acetic acid, 93.39 grams of tetramethylene sulfone, and 7.09 grams of trifluoromethanesulfonic acid were added into a 250-Hastelloy C bomb.

This mixture was stirred vertically using a furnace for 15 minutes.
Heat to a temperature of 0°C.

Ethylene was then passed under a pressure of 40 bar.

The reaction was stopped after 3 hours.

The produced ethyl acetate was distilled under reduced pressure.

This produces 45.1 g of ethyl acetate, 111.8 g of distillation residue containing essentially tetramethylene sulfone, trifluoromethanesulfonic acid and unreacted acetic acid.

Actual Cases 24 to 29 The distillation residue obtained in Example 23 (111.8 g) was added, but using the operating method described in Example 23, under the same conditions of temperature, pressure and time, 3.
5.5. ! Perform a second operation by adding fresh acetic acid of ii'.

The ethyl acetate produced at the end of this operation is distilled and the operation of Example 25 is carried out using the distillation residue.

The operations corresponding to Examples 24 to 29 are carried out according to the same principles.

For each example, Table 5 below shows the amount of recycled distillation residue from the previous operation (recirculation), the amount of fresh acetic acid (acid) added and the amount of distilled ethyl acetate (M
) is shown.

Claims (1)

[Scope of Claims] 1. A method for producing ethyl esters from ethylene and at least one carboxylic acid under pressure in a liquid phase in the presence of an effective amount of an acid catalyst, wherein the reaction is carried out under the acidity of the liquid phase. 1. A method for producing ethyl esters, which is carried out in the presence of at least one dissociative, inert and stable solvent capable of increasing the concentration of ethyl esters. 2. The method according to claim 1, wherein the solvent has a dielectric constant of at least about 250. 3 the carboxylic acid has up to 20 carbon atoms in the molecule,
selected from the group comprising saturated or unsaturated aliphatic acids which may have one or more halogen atoms in the molecule, and benzoic acid, toluic acid, naphthenic acid, succinic acid, adipic acid and phthalic acid A method according to claim 1 or 2, characterized in that: 4. Claim 1 or 2, characterized in that the carboxylic acid is selected from acetic acid, propionic acid, butyric acid, isobutyric acid, hexanoic acid, monochloroacetic acid, dichloroacetic acid, bromoacetic acid, and chloropropionic acid. The method described in section. 5. The method according to claim 1 or 2, wherein the carboxylic acid is acetic acid. 6 The solvent is tetramethylene sulfone and its derivatives,
The method according to claim 1, characterized in that the method is selected from among: and mixtures thereof. 7. Sulfuric acid, alkanesulfonic acids having at most 6 carbon atoms in the molecule, benzenesulfonic acid, p-toluenesulfonic acid, benzene, in which the catalyst is optionally contained in the form of a lower alkyl ester, isolated or in a mixture. 3. Process according to claim 1, characterized in that it is selected from the group comprising disulfonic acids, naphthalenedisulfonic acids and perfluoroalkanesulfonic acids having at most 8 carbon atoms. 8. Claim 8, characterized in that the catalyst is selected from perfluoroalkane sulfonic acids and their lower alkyl esters having at most 8 carbon atoms in the molecule, either in isolation or in a mixture. The method according to item 1 or 2. 9. Process according to claim 1 or 2, characterized in that the catalyst is selected from the group comprising trifluoromethanesulfonic acid and its lower alkyl esters, either in isolation or in a mixture. 10. Claims 7, 8, or 9, characterized in that some or all of the catalyst is in the form of an ester, the alkyl group of which contains 1 to 4 carbon atoms. The method described in section. 11. Process according to claim 7, 8 or 9, characterized in that part or all of the catalyst is in the form of an ethyl ester. 7. Process according to claim 1, 2 or 6, characterized in that the mole fraction f of the 12 solvent is greater than or equal to 0.4. 3. Process according to claim 1, characterized in that the amount of 13 catalyst is between 0.05 and 2 mol per mixture 11. 14. Process according to claim 13, characterized in that the amount of catalyst 14 is between 0.1 and 1 mol per mixture 11. 3. Process according to claim 1, characterized in that the 15-[-terene pressure is between 20 bar and 60 bar. 16. Process according to claim 1 or 2, characterized in that the reaction temperature is between 100°C and 200°C. 17. Process according to claim 16, characterized in that the reactivity is between 130°C and 160°C.