BG100021A - Method and equipment for the preparation of monocarboxylic acids from carbohydrates, derivatives of carbohydrates or primary alcohols - Google Patents

Abstract

In the method proposed for the production of monocarboxylic acids from carbohydrates, carbohydrate derivatives or primary alcohols, the carbohydrates, carbohydrate derivatives or primary alcohols are oxidized continuously in aqueous solution at concentrations betweeen 0.1 and 60 % by oxygen or oxygen-containing gases, using noble-metal or mischmetal catalysts. The output flow of products thus formed is fed to an electrodialysis unit and the monocarboxylic acids removed and isolated.

Description

The invention relates to a method and apparatus for the production of monocarboxylic acids from carbohydrates, carbohydrate derivatives or primary alcohols.

It is possible to selectively oxidize carbohydrates through various biochemical processes. However, these production methods have significant drawbacks. First, the cultivation of microorganisms or the production of biocatalysts is fraught with considerable difficulties. Production methods in most cases involve fermentation (for example, in the production of gluconic acids), so that the use of nutrients in the fermentation solution is used in fermentation solutions. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · until significant amounts of salt are obtained. Another disadvantage is the sterility of operations, which is often required by these methods, so the considerable cost of the equipment must be borne in mind.

Of particular importance is the heterogeneous catalytic oxidation of suitable support materials with precious metals of the eighth subgroup. In this way, the oxidation of glucose to gluconic acid with atmospheric oxygen can be carried out, for example with a Pt / C catalyst. The disadvantage of this method, however, is the sharp decrease in the selectivity of the reaction and the rapid deactivation of the catalyst, Ullmanns Enzyklopaedie der Technischen Chemie, 4th newly revised edition, Vol.24, page 785, Verlag Chemie 1983.

Similar problems are observed with sucrose oxidation. Heyns and Paulsen have already investigated this reaction with platinum catalysts (K. Heyns, H. Paulsen, Adv. Carbohydr. Chem. 17, 169 (1962); K. Heyns, W. D. Soldat, P. Koell, Chem. Ber. 3619 ( 1975) As a final product, they receive mixtures of oxidized compounds which cannot be given chemical structure and composition due to their complexity.

In the method of producing diacetone ketogluconic acid, known from EP 0 040 709 B1, diacetone sorbose is partially oxidized and separated by electrodialysis. In this case, a discontinuous process is used and due to the introduction of protecting groups, the starting derivative has only one oxidizing group.

DE 38 03 465 Al, DE 39 16 206 A1 and US-PS 4 985 553 have known various periodic processes in which quantitatively unacceptable conversion is achieved or reaction mixtures containing unsatisfactory impurities of the genus are obtained.

compounds. In some cases, the isolation of the final product by expensive methods of purification is already proposed in the literature.

The method of partial oxidation of sucrose, described in EP 0 218 150 B1, strongly states that the discontinuous process produces wide-range polyoxide products.

Attempts to selectively oxidize sucrose to only one primary hydroxyl group have so far been unsuccessful in the use of conventional techniques.

In addition to the three possible monocarboxylic acids that can be obtained by oxidation of the primary hydroxyl groups, di- and tricarboxylic acids are also obtained as compounds in the reaction mixture. In addition, they are obtained in the case of the described variants of a number of cleavage products which are not described in detail, leading to significant losses in yield and a significant decrease in the selectivity of the reaction with respect to the formation of monocarboxylic acids. (Les A. Edye, George V. Meehan, Geoffrey N. Richards, Platinum catalyst oxidation of sucrose. J. Carbohydrate Chemistry, 10 (1), 11-23 (1991)).

The same is observed in the case of reducing saccharides, such as tests for palatine trait (Dissertation N. Puke, TU Braunschweig).

It is an object of the present invention to provide a method for the oxidation of carbohydrates, carbohydrate derivatives and primary alcohols with better selectivity in terms of monoxidized products.

The problem is solved as the carbohydrates, ria derivatives or primary alcohols are oxidized continuously in aqueous solution and concentration between 0.1 and 60% with · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Oxygen or oxygen-containing gases on precious metal or mixed metal catalysts, the flow of the products thus obtained is subjected to electrodialysis, in which the resulting monocarboxylic acid is removed.

This method is extremely suitable for the production of monoxidized carbohydrates or derivatives of carbohydrates and primary alcohols. The soft continuous reaction process and the simultaneous separation of the oxidized products by electrodialysis actually results in almost exclusively monocarboxy compounds of carbohydrates and derivatives of ulehydrates or primary alcohols. At the same time, high yield per unit volume and time is possible.

The specific functionalization of the saccharides and derivatives of (the saccharides listed among the starting materials is of great industrial interest in the synthesis of hydrophilic building blocks for polymers and surfactant sectors on a carbohydrate basis. Due to their environmentally friendly properties, hese crude materials have significant advantages compared to synthetic products.

It turns out to be especially effective if the substances remaining after electrodialysis and removal of monocarboxylic acids go through the oxidation phase one more time. In this way, a continuous cycle and, in particular, efficient treatment of the starting materials is poured.

It is advantageous for the flow of starting material to pass first through a catalyst enriched in free bubbling with air so that sufficient oxygen is sucked in; ί s ο ο а а д а м р о а к ц 1 i> ha на ο к ί i * _ a> _. a a c.

Π ii,;:. i, HilpJ '1 o ii JOO p v Ί s H C i c Ο 1! ii., ii <i I i C H pc κ i.G t ί <. Ί \ i c TO E.

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wherein the carbohydrates or carbohydrate derivatives can be selectively converted to monocarbonyl derivatives when combined in two steps. The first step of the process involves continuous oxidation on precious metal or mixed metal catalysts. The latter are also suitable, but in terms of their recycling, noble metal catalysts with a catalytically active element are preferred.

The monocarboxylic acids obtained during oxidation are then also continuously removed from the reaction mixture in the second step of the process, electrodialysis. This combination, unspecified. of continuous oxidation followed by continuous removal of the resulting oxidized products is appropriate in a specific manner for the production of monocarboxylic acids from carbohydrates and their derivatives. Thus, a higher conversion is achieved than in the methods described so far and the selectivity, in terms of the production of monocarboxylic acids, is surprisingly above 95%.

The continuous oxidation process is carried out in the engineering aspect as follows:

(a) The reactor system consists of a gas separator (vessel equipped with a stirrer) together with a cylindrical reactor in which a fixed catalyst bed is placed. The gas separator may in particular be a vessel. equipped with stirrer (reactor equipped with stirrer). The reactor equipped with a stirrer is fitted with an oxygen concentrator or via the floor.

air vance, or it is inc can be gaseous the mixture is more with it partial pressure on oxygen, or submission to or C 1 oxygen like bubbles, and l and bubbling nr with special g and z o in and pressure hoses or without pressure. The memory of a patigue equipped with confusion: ι к а р <ыл. pomegranate is ι: ы pipit y e nopeι. ·. ril guidrn that H pci and -

• · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ············· fertilizer (possibly upstream and downstream) in which oxidation occurs in contact with the catalyst.

(b) Oxidation may also be carried out by means of suspended catalysts (slurry method) in a vessel equipped with a stirrer in which the connection to the electrodialysis device is carried out during the separation step. In the simplest case, decanters or cross-flow modules may be used for this purpose. The technological solution to this problem is also possible by using suitable retention systems such as anti-flush filters, separators, etc.

It is appropriate to use precious metal contact surfaces or mixed metal catalysts, which may be, for example, extrudates (C, oxides), fibers, tablets or powders as catalysts. When using precious metal as a catalyst, the metal portion should be between 0.1 and 10%. Particularly good results are achieved with platinum catalysts having a platinum content of only 1%, in powder form, in which, however, the fine fractions are separated by sorting. The flow coming from the cylindrical reactor is then fed into the electrodialysis apparatus so that the oxidized products migrate to the concentrate by applying current and are then diluted by the reaction system. In order to maintain the equilibrium state of the continuous reaction system, the amount of concentrate that is diluted in a controlled manner is dosed by adding a leach solution to the reactor equipped with a stirrer.

Mixed metal catalysts, for example, have been used as such by Degussa AC and described in a communication by K. Deiler and B. Despeyroux in Catalysis of organic reactions (1992).

• ·

Particularly suitable apparatus for carrying out the process of the present invention must be coupled in series with degassing, oxidation and electrodialysis steps.

In order to achieve particularly precise control of the quantities of substance treated in individual cases, it is particularly preferable to connect the branched line in parallel with the electrodialysis device.

By means of this additional parallel line, a type of bypass is made parallel to the electrodialysis device. Together with the appropriate flow control or pump controllers, it may be possible to supply the analyzer or for a number of substances outside the gas counterflow to the electrodialysis device only to the extent that they can interact and return unreacted quantities directly to the the degassing device once more via the bypass line. Therefore, at each stage, the exact optimal amount of substance is reacted.

The names of the three possible acids are used only in the abbreviated sucrose-monocarboxylic form in the present application.

The full names, along with those of the two other products mentioned below, are:

C _& -sucrose monocarboxylic acid:

1-0- (P-D-Fructofuranuronyl) is e / -D-glucopyranoside

C-sucrose monocarboxylic acid:

2-keto-2-0- (cZ-D-glucopyranosyl - D-glucofuranic acid

C, ₆ -sucrose monocarboxylic acid: 1-0- (-D-fructofuranosyl) - c / -D-glucopyranuronide

Cj-oxidized GMF: 5- (with <-D-glucopyranosyl-oxymethyl) -furan-2carboxylic acid

C -oxidized GMF:> - (cA-D-glucopyranuronyl-oxymethyl) furfural.

The apparatus for carrying out the method will be explained in detail below by means of diagrams and by some preferred parameters.

Figure shows a preferred scheme according to the invention;

Figure is a graphical dependence of the method according to the first example;

Figure 3 is a graphical dependence of the method according to the second example;

Figure 4 is an alternative diagram of

Figure 1.

The diagram shown in Figure 1 shows a vessel.

fitted with a stirrer or a tank 10 with a stirrer and a motor for the stirrer 11.

The product 10 is introduced into the product through, the pH controller 17 is shown schematically, the data goes to the thermostat and is returned from it through 19. Additionally, air (Ν ₂ / Ο _Ί ) is supplied to the tank 10.

After stirring in a stirrer vessel, the pH controlled product, for example a carbohydrate enriched and mixed with oxygen, is passed through one of the pumps marked P to the oxidation device 30. Said oxidation device 30 contains a noble metal or mixed metal catalyst, in the case is a catalyst for platinum on carbon. Continuous oxidation of the starting material takes place in the oxidation apparatus 30; the latter then passes through the next pump P to the electrodialysis device 40. The latter, an electrodialysis battery or an electrodialysis cell, is also shown schematically. In it, the monocaroonic acid is continuously separated from the partially oxidized mixture on the highway 41. to which conductive cell 42 is placed.

Carbohydrates, which are not monoxidized, are returned back on highway 43 to the tank 10 for further processing in addition to product 15, which in all cases corresponds chemically.

After passing through conductive cell 42, the monocarboxylic acids enter the tank 50 and concentrate there. In tank 50, pH is continuously measured by means of 51. The product is discharged through 52, while through the undiluted product 53 is returned one more time to the electrodialysis device via pump P.

Figure 4 shows a diagram in accordance with almost all the details of Figure 1. Here, in addition, line 60, a bypass line between the output of the oxidation device 30 and the return line 43 of the electrodialysis device in the tank 10 is placed.

This line 60 is only schematic; it may additionally include tanks, measuring instruments and vessels, pumps and flow control elements.

The already mentioned pumps P, included in the scheme according to Figure 1, are capable of transferring only those amounts of the substance to be optimally treated from the oxidation device 30 into the electrodialysis apparatus 40 alone or with the aforementioned elements. The excess can be returned through the bypass line 60 again to the degassing unit or tank 10 together with the carbohydrates which have not been monoxidized by the electrodialysis apparatus 40 through line 43.

As an example of the method described, the apparatus can not be selectively converted to its monocarboxylic acid.

Although three primary hydroxyl groups of a molecule are capable of reacting, in all cases the oxidation takes place in only one of them, so that only the monoxidized sucrose derivatives are produced. The selectivity for these products is at least 95% and the formation of di- or tricarboxylic acid is not possible when using this continuous method.

In addition to the high selectivity, this continuous method of operation shows a significant increase in the reaction rate compared to the discontinuous method. The advantages of the process according to the present invention over the discontinuous method in terms of reactivity relate to glucose and sucrose and are shown in Figures 2 and 3.

Figures 2 and 3 show the time in minutes in minutes; of ordinate - conversion rate in percent. In each case, the symbolic depiction of the discontinuous method, in Figure 2 for the glucose response, in Figure 3 for the sucrose reaction, is shown in symbol.

The dashed line shows the continuous method dependence again in Figure 2 for the glucose reaction and Figure 3 for the sucrose reaction; additionally, Figure 3 shows the dependence using pure oxygen (0 ₂ ) by the continuous method.

A further increase in the reaction rate with respect to the formation of monocarboxylic acids can be achieved by increasing the partial pressure of oxygen in the solution, for example by introducing pure oxygen (instead of air or oxygen / nitrogen mixtures).

Another technical advantage of the process according to the present invention is that no catalyst deactivation is observed (compared to K. Heyns, N. Paulsen (see above).

re); N. Puke, Dissertation TU Braunschweig). Even when typing giving clean oxygen surprisingly the catalyst does not desac- tivira. This an advantage has not yet been described in the relevant literature and also proves the great contribution of technology-

in terms of selectively producing carbohydrate derivatives.

The method can be used without difficulty for reducing sugars, such as palatinose and glucose.

Selectivity for monoxidized products may be controlled by selecting suitable catalysts or by using suitable carriers or mixed metal contact surfaces or by pH.

In the case of palatinose, it is also possible, using noble metal catalysts (narimer Pt / Al ^ O ^ (1% Pt) Aldrich), in which A £ ₉ 0 ₃ is used as a carrier, can be oxidized to the maximum degree of the primary hydroxyl group at the 6 'position. In this case, it was found that despite the possibility of dicarboxylic acid formation. only monocarboxylic acid is obtained.

Moreover, it can be observed that in this method selectivity is affected in such a way by the choice of catalyst that oxidation results in only one oxidized product.

Experiments with other catalysts also show that not only the selectivity for mono acids is controlled by this method, but also the selectivity for the desired product. The method is not only suitable for saccharide oxidation. but it also makes it possible to convert alcohols derived from sugars (eg isomaltz) into their corresponding mono acids.

In addition, it is possible to oxidize carbohydrate derivatives, such as glucopyranosylmethylfurfural, in which the corresponding monocarboxylic acid can be converted from the 6 'position on one side and the aldehyde group on the other.

However, no double oxidized products can be obtained. Notwithstanding the presence of an aldehyde group that is able to oxidize more readily, in the same way exclusively products with a formed carboxyl group at C position are isolated. The aldehyde functionality remains in these compounds.

By this method, alkyl glycosides or mixtures thereof, such as, for example, alkyl polyglycosides, may be oxidized.

The examples show that the method described above is suitable for the oxidation of aldehyde and primary hydroxyl groups to produce monoxidized products. The products used, mainly from the carbohydrate sector, must be water soluble or in mixtures of water and organic solvents (eg water / isopropanol) and non-volatile under the conditions used. The method is also suitable for the preparation of monoxidized products (for example, propanol - propionic acid), if they are (even partially) soluble in the medium described using products from the '' non-carbohydrate sector ''

The oxidation is carried out at temperatures between 0 and 80 ° C, preferably, however, between 20 and 00 ° C. Concentrations can range between 0. ί and ου ό, but preferably between 3 and 20%. The pH values can be maintained in the range 1 to 13 during oxidation by the addition of Na ₂ CO ₃ , NaHCO ₃ or NaOH, or other "alkalizing agents".

For the isolation of monocarboxylic acids, ion-exchange membranes may be used in electrodialysis. In this case, however, free acids can be obtained only at low pH values. Regardless of the neutral environment of the process, however, the sodium salts of monocarboxylic acids are predominantly isolated in this case.

If electrodialysis is carried out with bipolar membranes, the neutralizing agent can be rebuilt and further free monocarboxylic acids of the corresponding products are obtained. Although the use of bipolar membranes requires higher investment,

GO. , the economic factor must nevertheless be reviewed me in individual cases, depending on the pro- these in subsequent operations. Comparison with discontinued operation method (with periodic

action) clearly demonstrates the advantages of the above method.

In the batch method, the reaction rates are much lower. The selectivity for the monocarboxy compounds in the comparative method is greatly reduced, resulting in by-products not identified in detail.

With continuous operation, no deactivation of the catalyst is observed compared to the method described herein, even after a period of two months. In the batch method, the catalyst is inactivated after a short time, as already described in the literature.

• ♦ · ·

The oxidation is performed as described in FIG. 1 circulation apparatus. Gas evolution was carried out in a stirred cylindrical double-walled reactor (500 ml) above the molten base. A glass insert is used as a relaxation zone, from which part of the flow is transferred by a centrifugal pump to a fixed catalyst bed, which is placed in a glass column closed by two frits. After passing through the catalyst bed, this flow reaches the mouth.

birth for electrodialysis and after separation of oxidized ones products, returns to the reactor equipped with a stirrer. The product is diluted after a concentration cycle in the device- the nature of electrodialysis and equivalent amount of solution

The product is dosed into the stirrer-equipped reactor by means of a sleeve pump. The solution lost during the concentration cycle is replaced with distilled water.

Example 1

Continuous oxidation of palatinosis at 35 ° C.

Using the apparatus described, 20 g of platinum / activated carbon catalyst (5% Pt / C; particle size 40 100 Jxm, Degussa) and 1000 ml of 0.1 molar solution of palatinosis were charged into the circulation apparatus and dilution cycle of the electrodialysis device . Distilled water and IM Na ₂ SO _{4 are used} for washing the electrode for the concentration cycle.

The temperature is maintained at 35 ° C by means of a circulation thermostat, the gas used (Ν ^ / υ ^, 4: 1) is fed through pressure-reducing valves and needle valves and the speed of

I · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · The gas flow is measured with a rotameter so that the oxygen velocity is 100 cm ³ / min and that of nitrogen is 400 cm ^3. / min.

The pH was kept constant 6.5 by titrating the resultant acid with IM NaHCO _3. The electrodialysis device (Bel III, Berghof GmbH Labortechnik.) Was equipped with 6 AMV / CMX pairs of membranes (effective membrane area = 360 cm ² ). voltage 5 to 6 volts. The achievement of the equilibrium state of the reaction is controlled by HPLC measurements. The product of the resulting substances has the following composition in concentrate:

6-0- (C-D-glucopyranuronyl) -D-fructofuranose (C ₆ -acid J: 50%

2-keto-6-0- (σ <-O-glucopyranosyl-O-arabino-hexonic acid (N-acid): 42.5%

5-0 - (- D-glucopyranosyl) -D-arabic acid (GPA acid): 3.5%

Selectivity for monocarboxylic acids: 96%

Substances can be separated preparatively and characterized by magnetic resonance imaging and mass spectrometry.

Example 2.

Oxidation of palatinosis at 42.5 ° C.

Similar to Example 1, palatinosis was oxidized at a reaction temperature of 42.4 ° C. The mixture of products obtained in the concentrate has the following composition:

C, -acid:

Cj-acid:

GPA acid:

50.0%

42.5%

4.0%

Selectivity for mono acids:

96.5%

Comparative example of a batch method

Oxidation of palatinosis

The oxidation by the periodic action method is carried out in the circulating reactor system in the same way, but without electrodialysis and without dosing of the product.

g of palatinate is dissolved in 1000 ml of distilled water and oxidized at 35 ° C.

Platinum / activated carbon catalyst (5% used)

Degussa, 40

At palatinosis reaction rate%

the reaction was completed after 4 days and chromatography separated the non-oxidized products.

The resulting product has the following composition:

C-acid:

'

50.6

Su-acid:

23.5

D i-acid:

as well as some unidentified products. The selectivity over the preparation of monocaroonic acids in this case is only 74.1.

Example J

Glucose oxidation

Glucose oxidation was performed in the apparatus described in Example with the pH being 6.5 (by the addition of NaHCO ₃ ) and at 35 ° C. The permanently obtained product solution has the following composition:

Na gluconic acid salt:

-) from / o

Na glucuronic acid salt:

The selectivity for mono acids is 99%.

Comparative example of the batch method 2

Glucose conversion at 35 ° C, pH 6.5 and the use of a platinum / activated carbon catalyst (5% Pt, Degussa, 40-100.

The main oxidized products are:

On salt on gluconic acid: 60% On salt on glucuronic acid: 15% On salt on glucose acid: 10%

as well as 15% unidentified detail products.

The selectivity for mono acids in this case is up to 75%.

The graphical dependence of Figure 2 shows the glucose oxidation curves of the continuous method and the periodic action method.

The reactivity of the continuous method of operation is significantly higher and no deactivation of the catalyst is observed.

Example 4

Oxidation of glucose at pH 3

Oxidation was carried out as described in Example pH was not strictly controlled by the addition of NaHCO ₃ ·

After the start phase, the pH value becomes 3 as a result of the acids formed.

Under these reaction conditions, gluconic acid is obtained

S-lactone of gluconic acid, which, however, is again converted to gluconic acid after an increase in pH.

Product composition:

Gluconic acid:

S-lactone of gluconic acid:

Glucuronic acid:

Example 4a

Mixed metal catalysts are precious metal catalysts that contain two or more catalytically active metals together with promoters such as, for example, bismuth. The problem with these catalysts in the batch method is that, despite the longer reaction time, they are not as selective. In this case.

• · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · However, follow-up reactions involving monocarboxylic acids are carried out so that significant amounts of by-products are obtained. This disadvantage can be overcome by using the method of the present invention. The products obtained are removed by electrodialysis as soon as they are formed and, therefore, they no longer come into contact with the catalyst.

This is practically demonstrated using a mixed metal catalyst Pt / Pd / Bi (Degussa) for the oxidation of glucose to gluconic acid or glucuronic acid.

The oxidation was carried out as described in Example 3, except that a mixed metal catalyst Pt / Pd / Bi was used.

Product composition:

Na gluconic acid salt:

%

Na glucuronic acid salt:

The selectivity for mono acids in this case is up to 98%.

Example 5.

Sucrose oxidation

Sucrose can be converted to the corresponding monocarboxylic acids according to the operations described in Example 1.

The oxidation is carried out at pH 6.5 and 35 ° C to give a final product of a mixture of three mono-carboxylic acids:

With sucrose 6 monocarbonate acid: 46.5 % With _& sucrose monocarbonate acid: 43.7 % With _(- sucrose monocarbonate acid: 4.9 %

Selectivity is over 95%.

Comparative example of the batch method 3

Sucrose oxidation

Oxidation by the method of periodic action at

35 ° C and pH 6.5 lead in days at a reaction rate of 90% to a product of the following composition:

C-sucrose monocarboxylic acid: 6 40.0% With ₆ ~ sucrose monocarboxylic acid: 31.0%, of which approximately 10% diacid Cj-sucrose monocarboxylic acid: 8.8%

The selectivity for monocarbonate compounds is up to about 70%.

The graphical representation of Fig. 3 shows the advantages of a continuous method of operation in relation to the reaction rate.

Example 6

Oxidation of glucopyranosyl-methyl-furfural (GMF) ·

··· ·

Continuous oxidation of GMF was performed according to the method described in Example 1.

At 35 ° C and pH 7, the following are obtained:

C-oxidized GMF:

Co-oxidized GMF:

%%

The selectivity for monocarbonate compounds is up to 99%.

Example 2

Sucrose oxidation was carried out in the apparatus described in Example 1 at pH 6.5 and at 35 ° C. Instead of a mixture of oxygen and nitrogen, pure oxygen is introduced, whereby the production of oxidized products is accelerated accordingly (Figure 3).

The main oxidation products are:

With ₆ -sucrose carbon acid: 43.0 % With sucrose 6 carbon acid: 43.0 % sucrose carbon acid: 9.5 %

Selectivity reaches over 95%.

In summary, the present invention relates to a method and apparatus for the production of monoxidized products from carbohydrates, carbohydrate derivatives and primary alcohols. The starting materials are charged into a continuous oxidation device comprising a noble metal catalyst or mixed metal catalysts. The flow containing monocarboxylic acids

obtained on the catalyst are charged to the electrodialysis device continuously producing monocarboxylic acids where acid is released.

Claims (19)

Claims A method for the production of monocarboxylic acids from carbohydrates, carbohydrate derivatives and primary alcohols, characterized in that the carbohydrates, carbohydrate derivatives or primary alcohols are oxidized continuously in aqueous solution and at concentrations between 0.1 and 60% with oxygen or oxygen-containing gases on noble metal or mixed metal catalysts, the stream containing the products thus obtained is electrodialysis to remove the monocarboxylic acids obtained. 2. The method according to claim 1, characterized in that after the separation of the monocarboxylic acids, the non-oxidized products are returned for oxidation one more time. 3. The method according to claim 1 or 2, characterized in that the material flow pre-passes over the catalyst bed and is enriched with oxygen in free bubbling. 4. The method according to claim 3, characterized in that during the oxidation step, oxygen is enriched in the reactor first by supplying air, or a gas mixture with a higher partial pressure of oxygen, or pure oxygen distributed under in the form of bubbles, or free bubbling under pressure or without pressure, and by means of which, through a pump, the flow of the reactor enters the parallel cylindrical reactor, together with the catalyst. 5. The method according to claim 3, characterized in that during the oxidation step, a slag method with suspended catalysts is operated in the reactor equipped with a stirrer. • · · · Method according to claim 5, characterized in that the oxidation step and the electrodialysis step are separated into different devices. A method according to any of the preceding claims, characterized in that the precious metals of the eighth subgroup are supported as catalysts. 8. A method according to claim 7, characterized in that platinum catalysts are used on carriers with a platinum content between 0.1 and 10%, in particular powder Pt / C catalysts with a platinum content between 0.1 and 10%, by removing fine fractions. A method according to any one of the preceding claims, characterized in that reduced saccharides such as, for example, palatinose, glucose, fructose, sorbose, and / or non-reduced saccharides such as, for example, mono-oxidizing starting materials are used. sucrose, trehalose, and / or alcohols derived from sugars such as, for example, palatinitol, sorbitol, and / or alkyl glycosides and polyalkyl glycosides such as, for example, methyl glycoside, octyl glycoside or similar mixtures, and / or specially modified carbohydrate derivatives such as, for example, or GMF. A process according to any one of the preceding claims, characterized in that water or mixtures of water and secondary alcohols, preferably isopropanol, are used as solvents of the starting materials. The method according to any of the preceding claims, characterized in that the oxidation and electrodialysis are performed at pll in the range from 1 to 13. A method according to any of the preceding claims, characterized in that the oxidation temperature is in the range from 0 to 80 ° C, preferably between 20 and 60 ° C. Method according to any one of the preceding claims, characterized in that the products are used in concentrations between 3 and 20%. A method according to any one of the preceding claims, characterized in that Na ₂ CO ₃ or NaHCO ₃ or MaOH or other alkalizing agents are used to adjust the pH. A method according to any of the preceding claims, characterized in that only the six positions of the unreduced glucopyranosyl units are selectively oxidized using a Pt / Ai ₂ O ₃ catalyst supported. Method according to any one of the preceding claims, characterized in that a branched line (60) is used and the flow of material coming from the oxidation device is isolated from the flow of material coming from the electrodialysis device. Apparatus for conducting any of the above methods according to any one of claims 1 to 16, characterized in that it includes devices for gas separation (10), for oxidation (30) and for electrodialysis (40), connected in series. Apparatus according to claim 17, characterized in that it includes an additional line (41) to the tank (50) and a return line (43) for the gas extraction device (10). Apparatus according to claim 17 or 18, characterized in that the gas separation device (10) is provided with a stirrer reactor. 20. Apparatus according to any one of claims 17 to 19, · · · · · · · · · · · · • · · · · · · · · · • · · · · · · · · · · · · · · · · · · 4 characterized with the fact that in the electrode device- ion exchange or bipolar membranes are used. Apparatus according to any one of claims 17 to 20, characterized in that the side line (60) provides a parallel to the electrodialysis device (40).