BRPI0711627A2 - method for making alpha hydroxy carboxylic acids - Google Patents

Abstract

METHOD FOR MANUFACTURING ALPHA-HYDROXICARBOXYLIC ACIDS. The present invention relates to a continuous method for the manufacture of alpha-hydroxycarboxylic acid, in which, as educts, alpha-hydroxycarboxylic acid amide is reacted with an alcohol in the presence of a catalyst, obtaining a product mixture, which presents ester of alpha-hydroxycarboxylic acid as well as alcohol and catalyst, and educt currents are introduced into a fluid reactor under pressure comprising as educts an alpha-hydroxycarboxylic acid amide, an alcohol and a catalyst, the educt currents are reacted with each other in the pressure cooker under a pressure in the range of 0.1 mPa to 10 mPa (1 bar up to 100 bar), and in the product mixture the concentration of alcohol and ammonia is reduced, and the ammonia is removed by distillation, under a pressure that is constantly maintained above 0.1 mPa (1 bar), without the aid of additional extraction means. The continuous method can be applied on an industrial scale with special advantage.

Description

Report of the Invention Patent for "METHOD FOR MANUFACTING ALPHA-HYDROXIC CARBOXYLIC ACIDS".

The present invention relates to a method for manufacturing industrial scale alpha-hydroxy carboxylic acid esters. The present invention relates especially to a continuous method for making alpha hydroxy carboxylic acid esters according to the generic concept of claim 1.

Alpha-hydroxycarboxylic acid esters are valuable intermediates in the industrial scale synthesis of acrylic acid esters and methacrylic acid esters, hereinafter referred to as alkyl (meth) acrylate. Alkyl (meth) acrylates in turn find their main field of application in the manufacture of polymers and copolymers with other polymerizable compositions.

An overview of current processes for making (meth) acrylic acid esters can be found in the scientific literature such as Weissermel, Arpe ,, Industrial Organic Chemistry ", VCH, Weinheim 1994, 4. Edition, p.305 and or Kirk Othmer, Encyclopedia of Chemical Technology, "3rd edition, Vol. 15, page 357.

If synthesis of methacrylic acid esters such as methyl methacrylate such as alpha hydroxycarboxylic acid ester of 2-hydroxyisobutyric methyl esters (= HIBSM) is planned, it will be a central intermediate for their manufacture.

The manufacture of alpha hydroxy carboxylic acid ester by the reaction of an alcohol with an alpha hydroxy carboxylic acid amide is shown for example in DE-A-24-54 497. This document describes the use of compounds lead to catalyze the reaction. In this case, continuous methods are also mentioned, but without presenting a technical solution, in which the products are obtained with high efficiency.

In addition, DE-A-25 28 524 describes methods for making alpha hydroxy carboxylic acid esters. In this case different catalysts are used which comprise among other lanthanum compounds. Indeed, it is also mentioned in DE-A-25 28 524 that the described methods can be continuously performed, but no satisfactory solution to the problems that occur in this case is presented there either.

A method according to the genre is known from EP 0 945 423. In this case, a method for making alpha hydroxycaboxylic acid esters comprising the steps in which a hydrochloride amide is reacted is disclosed. alpha hydroxy carboxylic acid and an alcohol in the presence of a catalyst in a liquid phase while maintaining the ammonia concentration in the reaction solution at 0.1 wt% or less by removing the gas-produced ammonia in a gas phase .

To remove the ammonia from the reaction solution as a gas in the gas phase, it is removed from the reaction solution upon distillation. To this end, the reaction solution is heated to boiling and / or boiling an extraction gas, ie an inert gas, throughout the reaction solution.

The disadvantages of the method published in EP 0 945 423 with regard to the representation of alpha hydroxy carboxylic acid esters by alcoholization of corresponding alpha hydroxy carboxylic acid amides can be summarized as follows:

i. Simple distillation of ammonia by a variant of the method disclosed in EP 0 945 423 is ineffective. This proposal requires an extremely effective separation colony and, consequently, a special technical effort.

ii. If an inert extraction gas is used additionally or exclusively, the effectiveness of ammonia removal will in fact be improved, of course, by another process component, the manipulation of which means additional effort.

iii. If alpha hydroxy carboxylic acid amide and methanol are used as educts, the residual ammonia and methanol formed under the conditions set forth in EP 0 945 423 will be very difficult to separate from each other. The almost always necessary application of an inert gas for ammonia removal and the associated additional handling of a material stream (extraction gas / ammonia separation) make the proposed procedure relatively uninteresting in financial terms. which will also be reflected in the fact that until then there is no technical application of the disclosed method.

Considering the state of the art, it is therefore the task of the present invention to provide methods for making alpha-hydroxy carboxylic acid esters which can be made easily and at low cost.

Another task of the invention is to create a method in which alpha hydroxycaboxylic acid esters can be obtained very selectively.

Moreover, it is the task of the present invention to provide a method for making alpha hydroxy carboxylic acid esters in which no by-products or only small amounts of by-products are produced. In this case, the product should be obtained with the highest possible yield and overall low energy consumption.

These, as well as other tasks not explicitly mentioned, but which can be easily deduced and concluded from the context discussed here initially, are solved by methods with all the features of claim 1. Convenient variations of methods according to invention, are protected in the dependent claims referred to in claim 1.

The subject of the present invention are continuous methods for making alpha hydroxy carboxylic acid esters, in which alpha hydroxy carboxylic acid amide educts can be reacted with an alcohol in the presence of a catalyst to give a mixture of product which gives It has esters of alpha hydroxy carboxylic acid, ammonia, unreacted alpha hydroxy carboxylic acid amide as well as alcohol and catalyst, and the method is distinguished by the application of educt streams comprising as an alpha acid amide hydroxycarboxylic, an alcohol and a catalyst in a pressure fluid reactor; educt streams are reacted with each other in the pressure fluid reactor under a pressure in the range of 0.1 mPa to 10 mPa (1 bar to 100 bar); and the product mixture is low in alcohol and ammonia, whereby ammonia is obtained under a pressure which is constantly maintained above 0.1 mPa (1 bar), distilled off without the aid of additional extraction means.

Through the measures according to the invention, the following advantages can be obtained among others:

The resulting ammonia of the reaction according to the invention can be surprisingly and relatively effortlessly separated from alcohol, for example methanol, which is used for the alcohololysis and methanolysis of alpha hydroxy carboxylic acid amide. This is possible, although alcohol, methanol and ammonia are only separated from each other with much difficulty in dissolved form under usual conditions.

• During separation the ammonia already results in an extremely pure form and can therefore be reused in different processes without any further purification step. Alcohol also yields in a way that it is of a quality suitable for the process and can be recycled for example in a manufacturing process.

• In this case, the method of the invention avoids the use of auxiliary means for ammonia separation, especially by rendering inert use of inert gases as ammonia extraction means. Correspondingly in the case of the method according to the invention, a large amount of inert gas flow does not result, which in turn would have to be separated from the ammonia.

By the method according to the invention, alpha hydroxy carboxylic acid esters are obtained in large quantities and purity. This applies especially in comparison to the methods described in EP-A-0945423, in which alpha-hydrocarboxylic acid amides are subjected to an alcohololysis to form alpha-hydroxy carboxylic acid esters while maintaining an extremely small current ammonia concentration. in the liquid phase. Surprisingly it has been found that by applying pressure in combination with simple distillation / rectification, not only did the additional measurement of inert gas extraction become unreasonable but also a higher concentration of ammonia in the liquid phase was tolerable, without dispensing greater selectivities in total .

• In this case, the formation of by-products is incredibly small. In addition, high conversions are obtained especially taking into account the high selectivity.

• The method of the present invention furthermore has an extremely small tendency to form by-products.

• Moreover, the method according to the invention can be performed at low cost especially with low power consumption. In this case, the catalysts employed for the alcohololysis of the alpha hydroxy carboxylic acid amide for a long period without decreasing selectivity or activity, and the catalysts have a long shelf life.

Finally the method of the present invention may be carried out especially advantageously on an industrial scale. In the case of the method of the invention, alpha hydroxycaboxylic acid esters are manufactured by reacting the alpha hydroxy carboxylic acid amide educts in the presence of a catalyst.

• Of the alpha hydroxycarboxylic acid amides which can be used in the reaction of the invention are usually all carboxylic acid amides which have at the alpha position relative to the carboxylic acid amide group a hydroxy group.

In turn, carboxylic acid amides are generally known in the art. Usually compounds with groups of the formula - CONR'R "- where R'e R" independently represent hydrogen or a group containing 1 to 30 carbon atoms, comprising especially 1 to 20, preferably 1 to 10 and more especially 1 to 5 carbon atoms. The carboxylic acid amide may contain 1,2,3,4 or more groups of the formula - -CONR'R ". Particularly compounds of the formula R (-CONR'R") n, wherein the radical R represents a group containing 1 to 30 carbon atoms, especially comprising 1 to 20, preferably 1 to 10, more especially 1 to 5 carbon atoms, and more preferably 2 to 3 carbon atoms, Re R 'have the above meaning and a number. integer in the range 1 to 10, preferably 1 to 4 and more preferably 1 or 2.

The term "group containing 1 to 30 carbon atoms" means radicals of organic compounds having 1 to 30 carbon atoms. It comprises, in addition to aromatic and heteroaromatic groups, also aliphatic and heteroaliphatic groups, such as alkyl, cycloalkyl, alkoxy, cycloalkoxy, cycloalkylthio and achenyl groups. In this case, the groups mentioned may be branched or unbranched.

Aromatic groups according to the invention designate radicals of mono- or polynuclear aromatic compounds having preferably 6 to 20, especially 6 to 12 carbon atoms.

Heteroaromatic groups designate aryl radicals, where at least one CH group is substituted with N and / or at least two contiguous CH groups are substituted with S, NH or O.

Preferred aromatic or heteroaromatic groups according to the invention are derived from Benzol, Naphthalene, Biphenyl, Diphenyleter, Diphenylmethane, Diphenyldimethylmethane, Bisphenone, Diphenylsulfone, Thiophene, Furan, Pyrrole, Thiazole, Oxazole, Imidazole, Isothiazole, Isoxazole, Isoxazole, 1,3,4-Oxadiazole, 2,5-diphenyl-1,3,4-oxadiazole, 1,3,4-thiadiazole, 1,3,4-triazole, 2,5-diphenyl-1,3,4- triazole, 1,2,5-triphenyl, 3,4-triazole, 1,2,4-oxadiazole, 1,2,4-thiadiazole, 1,2,4-triazole, 1,2,3-triazole, 1, 2,3,4-tetrazole, Benzo [b] thiophene, Benzo [b] furan, lndol, Benzo [c] thiophene, Benzo [c] furan, Isoindol, Benzoxazole, Benzothiazole, Benzimidazole, Benzisoxazole, Benzisothiazole, Benzopyrazole, Benzothiadiazole, Benzotriazole, Dibenzofuran, Dibenzothiophene, Carbazole, Pyridine, Bipyridine, Pyrazine, Pyrazole, Pyrimidine, Pyridazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,4,5- triazine, tetrazine, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline, 1,8-naphthyridine, 1,5-naphthyridine, 1,6-naphthyridine, 1,7-naphthyridine, ft alazine, pyridopyrimidine, purine, pteridine or quinolizine, 4H-quinolizine, diphenyleter, anthracene, benzopyrrole, benzooxathiazidine, benzooxadiazole, benzopyridine, benzopyrazine, benzopyrimidine, benzopyrimidine, benzothriazine, pyridineazinine, pyridine Phenazine, Benzoquinoline, Phenoxazine, Phenothiazine, Acridizine, Benzopteridine, Phenanthroline and Phenanthrene, which may also be optionally substituted.

Preferred alkyl groups include methyl, ethyl, propyl, isopropyl, 1-butyl, 2-butyl, 2-methylpropyl, tert-butyl, pentyl, 2-methylbutyl, 1,1-dimethylpropyl, hexyl, heptyl, octyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-decyl, 2-decyl, undecyl, dodecyl, pentadecyl and eicosyl.

Preferred cycloalkyl groups include the cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl group, which may also be optionally substituted with branched or unbranched alkyl groups.

Preferred alkenyl groups include vinyl, allyl, 2-methyl-2-propene, 2-butenyl, 2-pentenyl, 2-decenyl and 2-eicosenyl.

Preferred heteroaliphatic groups include the above preferred alkyl and cycloalkyl radicals in which at least one carbon moiety is substituted with O, S or a group NR8 or NR8R9 and R8 and R9 independently signify an alkyl group containing 1 to 6 atoms carbon, an alkoxy or aryl group containing 1 to 6 carbon atoms.

In accordance with the invention, it is very especially preferable that carboxylic acid amides have branched or unbranched alkyl or alkoxy groups having 1 to 20 carbon atoms, preferably 1 to 12, conveniently 1 to 6, especially 1 to 4 atoms. carbon and cycloalkyl or cycloalkyloxy groups having from 3 to 20 carbon atoms, preferably from 5 to 6 carbon atoms.

The radical R may have substituents. Preferred substituents include halogens, especially fluorine, chlorine, bromine, as well as alkoxy or hydroxy radicals.

Alpha hydroxy carboxylic acid amides may be used in the method of the invention alone or as a mixture of two or three or several different alpha hydroxy carboxylic acid amides. Especially preferred alpha hydroxy carboxylic acid amides include alpha hydroxy isobutyric acid and / or alpha hydroxy isopropionic acid amides.

Further, in a variation of the method according to the invention of particular interest, such alpha hydroxy carboxylic acid amides, which are accessible by synthesis of cyanohydrin from ketones or aldehydes and hydrocyanic acid, can be used. In a first step the carbonyl compound, for example a ketone, especially acetone, or an aldehyde, for example acetaldehyde, propanal, butanal, is reacted with cyanhydric acid forming the respective cyanohydrin. Especially preferably acetone and / or acetaldehyde is reacted typically using a small amount of alkali or an amine as a catalyst. In another step the cyanohydrin thus obtained is reacted with water to form alpha hydroxy carboxylic acid amide.

This reaction is typically performed in the presence of a catalyst. In this case, especially manganese oxide catalysts are suitable as described for example in EP-A-0945429, EP-A-0561614 as well as EP-A-0545697. In this case, manganese oxide may be employed in the form of manganese dioxide, which is obtained by treating manganese sulfate with potassium permanganate under acidic conditions (see Biochem.J., 50 p. 43 (1951) and J. Chem. Soc., 1953, p. 2189, 1953) or by electrolytic oxidation of manganese sulfate in aqueous solution. In general, the catalyst is often used in the form of powder or granules of a suitable grain size. In addition, the catalyst may be placed in a carrier. In this case, the so-called slurry reactors or fixed bed reactors, which also appear can be operated as a drip bed and may be described, among others, in EP-A-956 898, may also be used. hydrolysis can be catalyzed by enzymes. Suitable enzymes include, among others, nitril hydratases. This reaction is described by way of example in "Screening, Characterization and Application of Cyanide-resistant Nitrile Hydratases" Eng. Life. Know. 2004, 4, No. 6. In addition, the acid hydrolysis reaction, especially sulfuric acid may be catalyzed. This is shown in JP Hei 4-193845. The alcohols successfully employed in the methods of the invention include all alcohols known to those skilled in the art as well as alcohol precursor compounds, which are in a position between the indicated pressure and temperature conditions of reacting with alpha-acid amides. hydroxycaboxylic acid in the sense of an alcoholysis. Preferably the reaction of α-hydroxycaboxylic acid amide is by alcoholization with an alcohol, preferably containing 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. Preferred alcohols are, among others, methanol, ethanol, propanol, butanol, especially n-butanol and 2-methyl-1-propanol, pentanol, hexanol, heptanol, 2-ethylhexanol, octanol, nonanol and cananol. As alcohol, especially preferably methanol and / or ethanol is used, methanol being more especially convenient. Even use of preliminary stages of an alcohol is at first possible. Thus, they may also be used for example alkylformiates. Especially suitable are methyl formate or a mixture of methanol and carbon monoxide.

The reaction between alpha hydroxycaboxylic acid amide and alcohol is carried out within the scope of the invention in a pressurized fluid reactor. In this case it is basically understood a reaction compartment, which allows to maintain an overpressure during the reaction. In this context, overpressure means a pressure greater than atmospheric pressure, that is, especially greater than 0.1 mPa (1 bar). Within the scope of the invention the pressure may be in a range greater than 0.1 mPa (1 bar) to less than or equal to 100 bar. It is therefore necessarily concluded that the pressure during both the reaction / alcoholysis according to the invention of the alpha hydroxycaboxylic acid amide as well as during the separation / removal of ammonia from the product mixture is greater than the atmospheric pressure. or greater than 0.1 mPa (1 bar). This mainly means that the ammonia produced during the reaction from the mixture is also distilled off under a pressure greater than 0.1 mPa (1 bar), making it absolutely unnecessary to use auxiliary media such as gas. extraction for distilling ammonia removal. The product mixture is poor not only in ammonia in the sense of the invention but also in unreacted alcohol. Exactly when methanol is used for alcoholysis, a mixture of product with the components that are almost inseparable from each other ammonia and methanol is obtained. In the simplest case, the two components referred to directly as the material mixture are separated from the product mixture to decrease the concentration of the ammonia product mixture and alcohol. The two substances are subjected to a subsequent separation operation for example a rectification. On the other hand, it is also possible in the sense of the invention to separate the two components alcohol (methanol) and ammonia in one process from the product mixture and in this case at the same time further separate the two components ammonia and alcohol (meta- nol).

In a variant of the preferred method of the invention it may also be of particular interest that the reaction step and the removal of the ammonia / alcohols from the product mixture be spatially separated and made into different units. To this end, it is possible to provide for example one or more pressurized fluid reactors and connect them to a pressurized distillation column. In this case, it is one or several reactors, which are housed outside the distillation / reaction column in a separate area.

In the broadest sense, this implies continuous methods for the manufacture of alpha-hydroxy carboxylic acid esters, in which as an educt the reaction of alpha hydroxy carboxylic acid amide with an alcohol in the presence of a catalyst is obtained to obtain a catalyst. mixture of product that contains alpha-hydroxy carboxylic acid ester, ammonia, unreacted alpha-hydroxy carboxylic acid amide as well as alcohol and catalyst, and the method stands out for the fact that

(a) educt streams comprising as an alpha hydroxy carboxylic acid amide, an alcohol and a catalyst are introduced into a pressurized fluid reactor;

(b) streams of ducts are reacted with each other in the pressurized fluid reactor with a pressure in the range greater than 0,1 mPa to 10 mPa (1 bar to 100 bar);

c) removing from the reactor the product mixture resulting from step b) having alpha hydroxy carboxylic acid esters, unreacted alpha hydroxy carboxylic acid amide and catalyst;

(d) lowering the alcohol concentration in the product mixture by distilling off ammonia under a pressure which is constantly maintained above 1 bar.

In accordance with the above, a variant of the particularly convenient method provides that

(b1) the ducts are reacted with each other in the pressurized fluid reactor with a pressure in the range 0.5 mPa to 7 mPa (5 bar to 70 bar);

b2) the product mixture resulting from step b1) is decompressed at a pressure lower than the pressure within the reactor and greater than 1bar;

c1) the decompressed product mixture from step b2) is introduced into a distillation column;

(2) is removed by ammonia and alcohol distillation from the top distillation column, the pressure in the distillation column being maintained in the range from greater than 1 bar to less than or equal to 1 mPa (10 bar); and

d1) removing from the column the product mixture resulting from step c2) with reduced concentration of alcohol and ammonia having unreacted alpha hydroxycarboxylic acid esters, unreacted alpha hydroxycarboxylic acid amide and catalyst.

According to this method variant, the reaction and separation of ammonia / alcohol is carried out in two different units, separated separately from each other. In other words, they are separated from each other reactor / reaction compartment and separation unit for the removal of ammonia / alcohol from the product mixture. This has the advantage that different pressure areas are used for the reaction / conversion of the ducts and the subsequent ammonia / alcohol separation. By separating the method into a reaction step within the pressurized fluid reactor at higher pressure than in a distillation column separation step, the two steps are conducted under pressure, ie under pressure greater than 0.1 mPa (1 bar), the separation action can be significantly improved, not easily foreseeable, in addition to the advantages hitherto presented for the first variants of the method according to the invention, and increase the effectiveness of the separation of the ammonia / alcohol mixture.

The mentioned quality characteristics can be further enhanced by repeating the reaction within the reactor one or more times with the product mixture with decreased ammonia and alcohol concentration in the separation column collection well (distillation column under pressure), where the reaction step is shifted to a plurality of pressurized fluid reactors, which are connected in series.

A variant of the method thus becomes very especially preferred, characterized in that

e) the product mixture eliminated in step d1) is compressed to a pressure in the range of 5 to 7 mPa (70 bar);

f) the compressed mixture according to step e) may be introduced to react in another reactor, and may then be reacted again; and

g) steps b2), c1), c2) and d1) are repeated according to the above enumeration.

It is therefore of particular interest that the mixture with reduced concentration of ammonia and alcohol be removed from a base above the first distillation column collection well, compressed under greater pressure than the distillation column and then introduced into a second one. which in turn will be decompressed under a pressure lower than in the second reactor and greater than 0.1 mPa (1 bar), after reacting again under high pressure and temperature and at A reacted product mixture should be obtained twice and then returned to the first distillation column below the base, through which the introduction was made into the second reactor but above the collection well of the first distillation column, where upon obtaining a mixture with twice decreased concentration of ammonia and alcohol is removed by ammonia distillation and alcohol again at the top.

These method steps can be repeated as many times as desired, being especially favorable for example three to four repetitions. Preferred is a method characterized in that the reaction in the pressure fluid reactor is repeated several times, decompression of the reacted mixture, introduction in the first distillation column, decrease in ammonia and alcohol concentration in the first distillation column , the removal of the low concentration mixture, compression and introduction of the low concentration mixture into another reactor is obtained, depending on the quantity n of the reactors connected in series, a product mixture with n-times decreased concentration of ammonia and alcohol at the base of the distillation column. In this case, n can be a positive integer greater than zero. Preferably n is not in the range of 2 to 10.

A variant of the convenient method provides that the aforesaid and defined steps a and g) are repeated several times.

Totally special variants of the method consist in that the reaction and concentration decrease are made four times by the use of serially connected pressure fluid reactors, giving a product mixture with four times reduced concentration of ammonia. niac and alcohol. This variant of the method is characterized by the fact that steps e) to g) are repeated at least twice, so that the reaction is carried out in total in at least four serially connected restores.

For one of skill in the art, in this context of course there is a sufficient amount of alcohol in each reaction step. Therefore, the alcohol concentration is decreased in the product mixture preferably only partially. On the other hand, alcohol may also be conducted separately to the respective reaction.

Different column and reactor temperature ranges have proved especially convenient for the variant of the indicated method.

According to the above described variant of the method, the reaction according to step c) may be carried out under higher pressure than ammonia distillation according to step d). Preferably, the pressure difference is at least 1 mPa (10 bar), especially preferably at least 4 mPa (40 bar) and most preferably at least 5 mPa (50 bar).

Thus, the pressure distillation column in general and preferably has a temperature in the range of about 50 ° C to about 160 ° C. The exact temperature is typically adjusted through the boiling system as a function of the prevailing pressure conditions.

The temperature in the reactor is preferably in the range of about 120 ° C - 240 ° C. In this case it is especially convenient to decrease the temperature from reactor to reactor, for example in steps in the range of 3 - 15 ° C, preferably from 4 - 10 ° C and most preferably convenient in steps of 5 ° C. Thus, the selectivity of the reaction is positively influenced.

Another measure to increase selectivity may also be to reduce reactor to reactor volume. With a descriptive reactor volume and increasing conversion, improved selectivity is also obtained. Preferably, the reactor volume decrease may be in the range of 15 to 50%, more preferably from 2% to 20% and most preferably 5% to 10% relative to the volume of the respective reactor.

The different measures to increase selectivity can be combined in this case with particular advantage. Thus, those skilled in the art can simply optimize selectivity by varying pressure, temperature and residence time. The reaction may be carried out especially preferably for example under a temperature in the range of 200 to 220 ° C, with the residence time being optimized. By separating the ammonia from the reaction mixture, the reaction can be repeated several times, thus obtaining a particularly convenient reaction engine, ie high selectivity at low costs.

As previously mentioned, it is favorable to remove at some points from the column the product mixture to be removed from the pressure distillation column. In this case, it is used for guidance purposes as a local indication of the distance from the withdrawal points to the collection well (column base) of the column. It is especially preferable to proceed within the scope of the invention such that the decompressed product mixture according to step c1), after each new reaction, is introduced into a pressurized fluid reactor as close to the column collection well as possible. with respect to the feed point of the previous step c1).

This variant of the method can be advantageously highlighted by the fact that the reaction is carried out according to step b) under a pressure of 2 mPa (20 bar) to 9 mPa (90 bar), especially preferably from 4 mPa (40 bar) to 8 mPa (80 bar) and most preferably from 5 mPa (50 bar) to 7 mPa (70 bar).

The distillation of ammonia according to step d) may preferably be carried out under a pressure in the range of 0.12 mPa (1.2 bar) to 1 mPa (10 bar), especially preferably 0.15 mPa (1, 5 bar) at 0.3 mPa (3 bar).

In addition to the described variant, in which the reaction of the alpha-hydroxy carboxylic acid amide with alcohol is accomplished by removing the resulting ammonia in two spatially separated but connected units, it may be preferable in another modification of the method, carried out by carry out the reaction step and the removal step in a single unit. In this case, the reactor and the pressure distillation column are designed in a single unit, almost converging.

According to this particular embodiment of the invention, this implies continuous methods for the manufacture of alpha hydroxy carboxylic acid esters in which the reaction is carried out as alpha hydroxy carboxylic acid amide educts with an alcohol in the presence of a catalyst, a mixture of the product having alpha-hydroxy carboxylic acid esters, ammonia, unreacted alpha-hydroxy carboxylic acid amide, as well as alcohol and catalyst is obtained, and the method stands out for its

(a) educt streams comprising as an alpha hydroxy carboxylic acid amide, an alcohol and a catalyst are introduced into a pressurized fluid reactor;

(b) reacting pipelines in the pressure fluid reactor with a pressure in the range greater than 0,1 mPa to 10 mPa (1 bar to 100 bar);

(c) the concentration of alcohol and ammonia is decreased in the product mixture and ammonia is distilled off under a pressure which is continuously maintained at more than 0,1 mPa (1 bar) without the aid of any means. additional reduction and

d ') removing from the reactor the product mixture with reduced concentration in alcohol and ammonia resulting from step c'), containing alpha hydroxy carboxylic acid esters, alpha hydroxy carboxylic acid amide and catalyst.

The pressure range to be maintained in the variant according to the invention described above, preferably in a reactive distillation column serving as a reactor, is variable over wide ranges. A preferred embodiment of the invention comprises in this case the fact that steps a ') through c') are performed simultaneously on a reactive distillation column under a pressure in the range of 0.2 mPa to 5 mPa (2 bar at 50 bar), preferably 0.5 mPa to 4 mPa (5 bar to 40 bar). Especially preferable is a method which stands out because steps a ') through c') are performed on a reactive distillation column under a pressure in the range of 1 mPa to 3 mPa (10 bar to 30 bar).

In a preferred embodiment of the method, according to the invention, the reaction of the ducts is performed on a reactive distillation column designed as a pressure column and the formed ammonia is removed or distilled during the reaction continuously from the top. of the column. This gives the surprising effect that the ammonia is simply separated without the need to lower the pressure and can be recovered in high purity. Also of particular interest is a variant in which ammonia is removed by distillation under pressure from the top of the column and alcohol by the collection well or by a side stream from the column. Through a properly designed reactive distillation column separation action, a separation of ammonia and alcohol can also be achieved.

The reaction temperature of the reactions, according to the invention, may vary over a wide range, and generally increases the reaction speed with increasing temperature. The upper temperature limit usually results from the boiling point of the alcohol used. Preferably the reaction temperature is in the range of 40-300 ° C, especially preferably 120-124 ° C and most preferably 180 ° to 220 ° C.

For the invention it may be advantageous if a maximum of 10 wt.%, Preferably a maximum of 5 wt.% And especially preferably a maximum of 1 wt.% Of the alcohol in the reaction phase is removed along the gaseous phase. reaction system. Through this measure the reaction can be carried out especially cost-effectively. In this case, the reaction system is advantageously distinguished by the fact that it is constantly kept under a pressure of more than 0.1 mPa (1 bar). In this case, the reaction system may comprise in particular the areas of the system in which the reaction is carried out and the areas of the system in which ammonia is removed from the products and alcohol, especially the columns of distillation. Correspondingly, the separation of ammonia and alcohol can be performed very effectively under a pressure greater than 0.1 mPa (1 bar), especially preferably greater than 0.15 mPa (1.5 bar). In this case, it is particularly convenient that a maximum of 10% by weight of the alcohol, with respect to alcohol conducted within the residence time, be distilled off with the ammonia from the reaction system.

Preferably the residence time may be from 30 seconds to 2 hours, especially preferably from 1 minute to 30 minutes, and most preferably from 2 minutes to 15 minutes. These data preferably refer to the reaction volume. In the case of several reactors, the sum of the reactor volumes is established without the volume of the distillation equipment being computed. In the case of reactive distillation, the residence times result from the volume of reactive distillations.

For the present invention, in one embodiment, any multi-stage pressure-resistant distillation column having preferably two or more separation stages may be employed.

The quantity of the separation stages is indicated in the present invention as the number of the bases in a bottom column or the quantity of the theoretical separation stages in the case of a packaging column or a column with packaging bodies.

Examples of a multistage distillation column include those such as bell bottoms, perforated bottoms, tunnel bottoms, valve bottoms, cracked bottoms, split perforated bottoms, bell perforated bottoms, nozzle bottoms, centrifugal bottoms for a multistage distillation column with packaging bodies such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Intalox saddles and for multistage distillation column with such Mellapak (Sulzer), Rombopak ( Kühni), Montz-Pak (Montz) and packaging with catalyst bags such as Kata-Pak.

A distillation column with combinations of bottom areas, filler areas or packing areas may also be used.

The product mixture with decreased ammonia concentration presents among other things the planned alpha hydroxy carboxylic acid esters. For further isolation and cleaning of the ester the lower ammonia concentration product mixture can be extracted from the distillation column collection well and another second distillation column, where the alcohol is distilled off from the top of the column. and preferably led to a reactor, yielding a mixture with reduced concentration of both ammonia and alcohol.

For further isolation and obtaining the alpha-hydroxy carboxylic acid ester from the low ammonia and alcohol concentration mixture, a method is preferred whereby the low ammonia and alcohol concentration mixture is eliminated by the collection well of the other distillation column. and carried to yet another distillation column in which the alpha hydroxy carboxylic acid ester is removed by distillation from the top and the mixture with reduced concentration of alcohol, ammonia and alpha hydroxy carboxylic acid ester thus optionally obtained is distilled to the reactor. after other cleaning steps. The alpha hydroxy carboxylic acid ester product obtained from the top of the column is highly pure and can be carried advantageously to further reaction steps to obtain alkyl (meth) acrylates.

Preferably the distillation apparatus as reported has at least one area, called a reactor, in which at least one catalyst is provided. Such a reactor may, as described, preferably lie within the distillation column.

In the context of the invention, it is emphasized that the reported procedure can tolerate a broad spectrum of quantitative relations of the educts. Thus, alcohololysis may be done in the case of a relatively high or low amount of alcohol relative to the alpha hydroxy carboxylic acid amide. Especially preferable are methods in which the reaction of the ducts may be carried out with an initial molar ratio of alcohol to alpha hydroxy carboxylic acid amide in the range of 1: 3 to 20: 1. Very particularly convenient is the ratio 1: 2 to 15: 1 and even more convenient 1: 1 to 10: 1.

In addition, methods are preferred in that they are used as an alpha hydroxy carboxylic acid amide and an alpha hydroxy carboxylic acid amide and as methanol alcohol.

The reaction according to the invention is carried out in the presence of a catalyst. The reaction can be accelerated through basic catalysts, for example. These comprise homogeneous catalysts as well as heterogeneous catalysts.

Of particular special interest for carrying out the method according to the invention as catalysts are lanthanum compounds, with water resistant lanthanum compounds being especially preferred. The application of these types of homogeneous catalysts in a method of the invention is novel and leads to surprisingly advantageous results. The term "water resistant" means that the catalyst in the presence of water contains its catalytic capabilities. Correspondingly, the reaction according to the invention may be carried out in the presence of up to 2% by weight of water without thereby impairing the catalytic capacity of the catalyst. In this context, the expression "essentially" means that the reaction rate and / or selectivity decreases by a maximum of 50% with respect to the reaction without the presence of water.

Lanthanum compounds refer to La, Ce, Pr, Nd, Pm, Sm, I, Gd, Td1 Dy, Ho, Er, Tm, Yb and / or Lu. Preferably a lanthanum compound having lanthanum is used.

Preferably, the lanthanum compound has a water solubility of at least 1 g / l, preferably at least 10 g / l at 25 ° C.

Preferred lanthanum compounds represent salts which are preferably present in the oxidation phase.

Especially preferred water resistant lanthanum compounds are La (NO3) 3 and / or LaCl3. Such compounds may be added as salts to the reaction mixture or formed in situ.

The homogeneous catalysts applicable to the present invention successfully include alkali metal alcoholates and titanium, tin and aluminum organometallic compounds. Preferably a titanium alcoholate or tin alcoholate such as tetraisopropyl titanium oxide or tetrabutyl tin oxide is used.

A special variant of the method implies that a soluble metal complex containing titanium and / or tin and the alpha hydroxy carboxylic acid amide is used as catalyst.

Another special modification of the method of the invention provides that a metal trifluoromethanesulfonate is used as catalyst. Preferably in this case a metal trifluoromethanesulfonate is used, in which the metal is selected from the group consisting of the elements in the groups 1,2,3,4,11,12,13 and 14 of the periodic system. Of these, those metal trifluoromethanesulfonates, in which the metal corresponds to one or more lanthanides, are preferably used.

In addition to preferred variants of homogeneous catalysis, methods using heterogeneous catalysts are convenient under certain conditions. Heterogeneous catalysts are successfully applicable to magnesium oxide, calcium oxide as well as ion exchangers and the like, among others.

Thus, for example, it may be preferable methods in which the catalyst is an insoluble metal oxide containing at least one element selected from the group Sb, Sc, V, La, Ce, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re, Fe, Co, Ni, Cu, Al, Si, Sn, Pb and Bi.

Alternatively, methods may be preferred in which an insoluble metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Co, Ni, Cu, Ga, is used as a catalyst. In, Bi and Te.

The ammonia released during alcoholization under the method of the invention can be easily returned for example to a total process for the manufacture of alkyl (meth) acrylates. For example, ammonia may be reacted with methanol to form hydrocyanic acid. This is disclosed for example in EP-A-0941984. In addition, hydrocyanic acid can be obtained from ammonia and methane according to the BMA- or Andrussow method, and these methods are described in Ullmann's Encyclopedia of Industrial Chemistry 5th edition on CD-ROM, title ,, Inorganic Cyano Compounds ". The acrylonitrile synthesis is described under the title Sohio-Prozess in Industrial Organic Chemistry by K. Weisermehl and H.-J. Arpe on page 307 et seq.

General sequence of the method of a first variant of the method according to the invention with reference to Figure 1.

According to a particularly preferred embodiment, the alcohololysis, preferably methanolysis in the combination shown in Figure 1, of a pressure rectifying column and various pressure fluid reactors. Alpha hydroxycarboxylic acid amide, for example hydroxy-superutiramide, is conducted through conduit (1) together with methanol through conduit (2) and with a methanol / catalyst mixture through conduit (3) through conduit (4) to a first pressurized fluid reactor (R-1). Under the above-mentioned reaction conditions a reaction mixture is formed in the reactor (R-1) from the alpha-hydroxy carboxylic acid ester and ammonia, unreacted alpha-hydroxy carboxylic acid amide and methanol, catalyst as well as traces of a by-product. This mixture is decompressed after leaving the reactor (R-1) at a small pressure level and through the conduit (5) to a pressure column (K-1). The column is preferably equipped with packages. There the ammonia was separated with part of the methanol from the reaction mixture and the top obtained as distillate. The highest boiling components, alpha-hydroxy carboxylic acid ester, by-product and unreacted alpha-hydroxy carboxylic acid amide are extracted again from the column with the remaining methanol, compressed under reactor pressure and brought to 2 ° C. ° - pressure reactor (R-2). The reaction is preferably carried out on 4 consecutively connected pressure reactors (R-1 to R-4). The product mixture leaving column (K-1) above the collection well is composed of alpha hydroxycarboxylic acid ester, traces of a by-product and hydroxyisobutyramide. It is conducted by the conduit (9) in the distillery (K-2). There alpha-hydroxy carboxylic acid ester accumulates as distillate and is extracted through conduit (10). The alpha hydroxy carboxylic acid amide / catalyst mixture leaves the column (K-2) at the top and is led back partially through conduits (12) and (4) to the first reactor (R-1). A partial flow (11) is fed to a thin layer steam generator (D-1). This makes it possible to eliminate a mixture of the amide, the high boiling by-product and the catalyst by the conduit (13).

The ammonia / methanol mixture obtained in column (K-1) as a distillate is compressed and through conduit (14) to another column (K-3). This separates the ammonia, which accumulates pure at the top, from the ammonia, which is fed back through the conduits (15) and (4) to the first pressure reactor (R1). <table> table see original document page 24 </column> </row> <table>

General sequence of the method of a second variant of the method according to the invention with reference to Figure 2.

For example, alcohololysis, preferably methanolysis may be carried out in the installation shown in Figure 2. The alpha hydroxycarboxylic acid amide, for example hydroxyisobutyramide is conducted by conduit (1) together with methanol by conduit (2) and a mixture methanol / catalyst through the conduit (3) of a reactive distillation column (K-1). The column is designed as a pressure column and is preferably fitted with bottoms. Under the above reaction conditions, a reaction mixture consisting of alpha-hydroxy carboxylic acid ester and ammonia, unreacted alpha-hydroxy carboxylic acid amide and methanol, catalyst as well as traces of a product is formed at the back of the column. - secondary. Ammonia accumulates as distillate and is extracted by the conduit (7). High boiling components, alpha-hydroxy carboxylic acid ester, by-product, and unreacted hydroxybutyric acid amide educts and methanol leave the column through the collection well. Through the conduit (6) this mixture is led to another distillery (K-2). In this column methanol accumulates as distillate, which can be led back to column (K-1) through conduits (9) and (5). The mixture obtained from the collection well, the alpha-hydroxycarboxylic acid ester, the secondary product and the hydroxyisobutyramide is conducted by conduit (8) to the distillery (K-3). There the alpha hydroxy carboxylic acid ester is extracted as distilled through the conduit (10). The alpha hydroxy carboxylic acid amide / catalyst mixture leaves the column through the collection well and is partially led through conduits (12), (4), and (5) back to column (K-1). A partial flow (11) is fed to a thin layer steam generator (D-1). This makes it possible to eliminate a mixture of the amide, high boiling components and catalyst through the duct (13). <table> table see original document page 25 </column> </row> <table>

In the following the present invention is further explained by way of examples.

Example 1:

In a laboratory test facility consisting of an educt dosing device and an agitated boiler reactor, a 48-hour test period of 157 g / hr of a methanol / catalyst mixture with a catalyst percentage of 0 was conducted. , 8 wt% and 35g / h alpha hydroxyisobutyramide. The reaction was carried out using La (NO3) 3 as a catalyst. The product mixture formed was analyzed by gas chromatography. The molar selectivity for alpha-hydroxyisobutyramide over alpha-hydroxyisobutyric acid methyl ester was 98.7%, resulting in an ammonia concentration in the product mixture of 0.7% by weight.

Examples 2-7:

Table 1 shows other examples which were performed on the indicated test equipment with a Me: OH: HIBA molar ratio of 14: 1, but under different reaction temperatures and residence times.

Table 1

<table> table see original document page 25 </column> </row> <table> Table 1 clearly shows that selectivity for α-hydroxyisobutyric acid methyl ester (HIBSM) depends not only on the ammonia concentration in the mixture. reactor, but also the technical reaction parameters, residence time and temperature and therefore exact reaction engineering.

Example 8:

In said laboratory test facility for a 48 hour test period a methanol / catalyst mixture having a catalyst percentage of 1.0 wt% and alpha hydroxyisobutyramide at a molar ratio of 7: 1 was continuously dosed. The reaction against HIBSM and ammonia was carried out under a pressure of 7.5 mPa (75 bar) and a reaction temperature of 200 ° C with a residence time of 5 minutes. The reaction was performed using La (NO3) 3 as catalyst. The mixture of product formed was analyzed by gas chromatography. The molar selectivity for alphahydroxyisobutyramide over alphahydroxyisobutyric acid methyl ester was 99%, resulting in an ammonia concentration in the product mixture of 0.63% by weight.

Examples 9-12:

In said laboratory test facility for a 48 hour test period a methanol / catalyst mixture with a catalyst percentage of 0.9 wt% and alpha hydroxyisobutyramide at a 10: 1 molar ratio was continuously dosed. The reaction against HIBSM and ammonia was carried out under a pressure of 75 mPa (75 bar) and a reaction temperature of 200 ° C and 220 ° C with a residence time of 5 minutes and 10 minutes. The reaction was performed using La (NOa) 3 as a catalyst. The product mixture formed was analyzed by gas chromatography. The molar selectivity for alphahydroxyisobutyramide relative to alphahydroxyisobutyric acid methyl ester and the ammonia concentration in the product mixture are listed in Table 2. Table 2:

<table> table see original document page 27 </column> </row> <table>

Claims (39)

1. A continuous method for the manufacture of alpha hydroxy carboxylic acid esters in which alpha hydroxy carboxylic acid amide is reacted with an alcohol in the presence of a catalyst to produce a mixture of acid ester ester product. alpha hydroxycarboxylic acid as well as alcohol and catalyst, characterized in that educt streams comprising an alpha hydroxy carboxylic acid amide, an alcohol and a catalyst are introduced into a pressure vessel reactor, wherein the educt streams are reacted between in the pressure restorant at a pressure in the range 0.1 mPa to 10 mPa (1 bar to 100 bar), and in the product mixture the concentration of alcohol and ammonia is decreased and the ammonia is distilled off, under a pressure which is continuously maintained at more than 0,1 mPa (1 bar) without the aid of additional extraction means. A method according to claim 1, characterized in that a) pipelines are introduced into a pressure reactor comprising as an educt an alpha hydroxy carboxylic acid amide, an alcohol and a catalyst; (b) the duct streams are reacted with each other in the pressure reactor under a pressure in the range 0.1 mPa to 10 mPa (1 bar to 100 bar); c) eliminating from the pressure reactor the resulting product mixture of step b) having unreacted alpha hydroxy carboxylic acid ester, unreacted alpha hydroxy carboxylic acid amide and catalyst; and (d) in the product mixture the concentration of alcohol and ammonia is decreased and the ammonia is distilled off under a pressure which is constantly maintained at more than 0,1 mPa (1 bar). Method according to Claim 2, characterized in that b1) the reactor ducts are reacted with each other under a pressure in the range of 5 bar to 7 mPa (70 bar); b2) decompressing the product mixture resulting from step b1) at a pressure lower than the pressure in the pressure reactor and greater than 0.1 mPa (1 bar); c1) a mixture of decompressed product resulting from step b2) is introduced into a distillation column; (c2) in the distillation column are removed by distillation of ammonia and alcohol from the top, with the pressure in the distillation column being maintained in the range greater than 0,1 mPa (1 bar) to less than or equal to 1 mPa (10 bar ); and (d1) the reduced ammonia-alcohol concentration product resulting from step c2) having unreacted alpha-hydroxycarboxylic acid ester, unreacted alpha-hydroxy carboxylic acid amide and catalyst is removed from the column. Method according to Claim 3, characterized in that e) the product mixture eliminated in step d1) is compressed at a pressure in the range of 5 to 7 mPa (70 bar); f) introducing the compressed mixture according to step e) into another pressure reactor for reaction purposes and to be reacted again; and g) repeating steps b2), c1), c2) and d1) as defined in claim 2. Method according to claim 4, characterized in that steps e to g) are repeated several times. Method according to Claim 5, characterized in that steps (e) to (g) are repeated at least twice, so that the reaction is carried out in total in at least four consecutively connected pressure reactors. Method according to any one of claims 4 to 6, characterized in that the decompressed product mixture according to step c1) is introduced after each further reaction into a pressure reactor as close as possible. from the distillation column collection well with respect to the feed point of the previous step c1). Method according to any one of claims 4 to 7, characterized in that the temperature is decreased from reactor to reactor. Method according to claim 8, characterized in that the temperature decrease is in the range of 3 to 15s C. Method according to any one of claims 4 to 9, characterized in that the reaction volume is reduced from reactor to reactor. 11. Method according to claim 10, characterized in that the reduction in the reaction volume is in the range of 2% to 20% with respect to the reactor volume respectively greater. Method according to any one of claims 2 to 11, characterized in that the reaction is carried out according to step c) under a higher pressure than ammonia distillation according to d). Method according to claim 12, characterized in that the pressure difference is at least 4 mPa. Method according to any one of claims 2 to 13, characterized in that the distillation of ammonia according to step d) under a pressure in the range of 0.15 mPa (1.5 bar) to 3 bar. Method according to any one of claims 2 to 14, characterized in that the reaction of the ducts is carried out according to step b) under a pressure in the range of 50 to 7 mPa (70 bar). . Method according to claim 1, characterized in that a ') educt streams comprising as an alpha hydroxy carboxylic acid amide, an alcohol and a catalyst are introduced into a pressurized fluid reactor; (b) reacting pipelines in the pressure fluid reactor with a pressure in the range greater than 0,1 mPa to 10 mPa (1 bar to 100 bar); (c) the concentration of alcohol and ammonia is decreased in the product mixture and ammonia is distilled off under a pressure which is continuously maintained at more than 0,1 mPa (1 bar) without the aid of any means. additional reduction and d ') eliminating from the reactor the product mixture with reduced concentration in alcohol and ammonia resulting from step c') having alpha hydroxy carboxylic acid esters, alpha hydroxy carboxylic acid amide and catalyst. Method according to claim 16, characterized in that steps a ') to b') are simultaneously performed on a reactive distillation column under a pressure in the range 0.5 mPa to 4 mPa (5 bar a 40 bar). Method according to claim 17, characterized in that steps a ') to c') are simultaneously performed in a reactive distillation column under a pressure in the range of 1 mPa to 3 mPa (10 bar to 30 bar ). Method according to claim 17 or 18, characterized in that ammonia is removed by pressure distillation from the top of the column and alcohol is removed from the column by the collection well or by a side stream. Method according to any one of the preceding claims, characterized in that the reaction of the ducts is carried out in the case of an initial molar ratio of alcohol to alpha-hydroxy carboxylic acid amide in the range 1: 3 to 20: 1. Method according to any one of the preceding claims, characterized in that Î ± -hydroxyisobutyric acid amide and / or Î ± -hydroxyisopropionic acid amide are used. Method according to claim 21, characterized in that it is used as an amide hydroxycarboxylic acid hydroxy isobutyramide and as methanol alcohol. Method according to at least one of the preceding claims, characterized in that the reaction is carried out under a temperature in the range 120-240 ° C. Method according to at least one of the preceding claims, characterized in that the residence time is during the reaction of the ducts in the range of 1 to 30 minutes. Method according to claim 24, characterized in that the residence time is in the range of 2 to 15 minutes. Method according to at least one of the preceding claims, characterized in that at most 10% by weight of the alcohol conducted within the residence time together with the ammonia of the reaction systems is removed by distillation. Method according to any one of the preceding claims, characterized in that the reaction is catalyzed by at least one lanthanide compound. Method according to claim 27, characterized in that the reaction is catalyzed by at least one water resistant delanthanide compound. Method according to claim 27 or 28, characterized in that the lanthanide compound is a salt. Method according to any one of the preceding claims 27 to 29, characterized in that the lanthanide compound is used in the oxidation stage III. Method according to at least one of the preceding claims 27 to 30, characterized in that the lanthanide compound shows a water solubility of at least 10 g / l. Method according to at least one of the preceding claims 27 to 31, characterized in that the lanthanide compound comprises lanthanum. A method according to claim 32, characterized in that the lanthanide compound comprises La (NO3) 3 and / or LaCl3. Method according to at least one of the preceding claims, characterized in that a soluble metal complex containing titanium and / or tin and the alpha hydroxy carboxylic acid amide is used as a catalyst. Method according to at least one of the preceding claims, characterized in that a metal trifluoromethanesulfonate is used as a catalyst. A method according to claim 35, characterized in that a metal trifluoromethanesulfonate is used in which the metal is selected from the group consisting of elements in the groups -1,2,3,4,11,12,13 and 14 of the periodic system. A method according to claim 36, characterized in that a metal trifluoromethanesulfonate is used, wherein the metal is one or more lanthanides. Method according to at least one of the preceding claims, characterized in that the catalyst is an insoluble metal complex containing at least one group consisting of Sb, Sc, V, La, Ce, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re, Fe, Co, Ni, Cu, Al, Si, Sn, Pb and Bi of the selected element. Method according to at least one of the preceding claims, characterized in that an insoluble metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W is used as a catalyst. , Fe, Co, Ni, Cu, Ga, In, Bi and Te.