MXPA97005671A - Procedure for the production of arabini - Google Patents

Abstract

The present invention describes a method for producing a pentitol, the present invention relates to a method for producing arabinitol from hexoses, for example, galactose and / or glucose, and / or fructose, or lactose hydrolysates, or invert sugar, or starch hydrolysates, the hexose is oxidatively decarboxylated to an aldonic acid of C5 followed by catalytic hydrogenation producing the arabinitol desired

Description

PROCEDURE FOR THE PRODUCTION OF ARABINITOL TECHNICAL FIELD The present invention devises a method for producing a pentitol. The present invention relates to a method for producing arabi or tol to couple of hexoses, for example, galactose and / or glucose, and / or fructose, or lactose hydrolyzate, or inverted sugar, or hydrolysates of starch. The hexose is oxidatively decarboxy to an acid to the ion of Cs followed by catalytic drogenation.

BACKGROUND OF THE INVENTION The chemical conversion of hexoses leading to arabirutol has been studied extensively. Andrews and others, 1. Org. Chem. (1989) 54_ 525? -5264, describe said chemical process, that is to say, the decarbonization of aldose sugars by chlorotop s- (tpfen? Lfo ma) rhodium (T). The unprotected Cn aldose sugars are decarbonylated by means of an equivalent to the chlorotri- (t-phenyl) phosphine) rhodium (I) to give the alditol of Cn-? correspondent. According to the authors, it has not been possible to perform these reactions under catalytic conditions. The large-scale application of this method, which involves the use of large quantities of rhodium, is not possible. In addition, the application of these reactions is limited by the required solvents, the preferred solvents are polar or sufficient to dissolve the sugar, however, they must be non-coordinating enough to allow the metal complexes to function effectively. . These characteristics have limited the solvents that can be used with the known metal complexes. The problems described with the application of the descpto method in the Andrews et al. Article (cited above) have been overcome to some degree as described in 1 < The co-pending patent application EP 0 7l 066. The materials such as arabinanos and arabmogalactans are also used as starting materials. These materials can be hydrolyzed to give the corresponding rnonosaccharides, for example, L-arabinose. which can be hydrogenated in addition to the corresponding polyols using known technology. However, hydrolysis suffers from the same disadvantages as the hydrolysis process to produce xylose from xylan-containing materials, that is, the main disadvantages of these processes are low yield and low product purity. An alternative synthesis of D-arabose consists of the oxidative degradation of glucomatic acid, described extensively by Ruff in "Bepchte der De? Tschen Chemischen Gesellschaft 32 (1899) 553-55-.". However, to obtain arabinitol, a minimum of three reaction steps are required from glucose. Oxidative decarboxylation is a well-known procedure and has been applied for the oxidative degradation of monosaccharides as well as disaccharides, such as lactose, maltose and cellobiose. The basic principle has been shown by Spengler and Pfannenstiel Z. Uirtschafts-gruppe Zuckerindustrie, Tech. 1935, 85, 546-552, and DE 620 248. To increase the selectivity of the reaction, oxygen is preferably used instead of air.

DE 1 044 793 describes a selectivity of 73% by applying air, the selectivity increases to 78% by applying oxygen gas. This is further shown in patent application DE 618 164. Of course, it is interesting to obtain high selectivity for this type of reactions. To obtain high selectivities, reactions are performed under high pressure, redox catalysts are added to the reaction medium, or organic solvents are added to improve oxygen transfer. Vourinen T. and others "Starch 1991 4_3 194-198" has described anthraquinone-2-sulphonic acid (AMS) as an efficient redox system to aid during oxidizing decarboxylation, hydrogen peroxide is generally added to re-oxidize the derivative of anthraquinone. However, even in the presence of anthraquinone-2-sulphonic acid, oxygen pressure of 6 bar is still required to obtain a good conversion. The omission of AMS requires increasing the oxygen pressure to at least 11 bar and preferably to 26 bar to increase the selectivity (Scholtz et al. U.S. Patent 4 125 559). further, organic solvents such as methane are added to the reaction medium to improve oxygen transfer. In accordance with FR 2 722 200 it is possible to replace oxygen gas with air and operate at atmospheric pressure, but then the addition of AMS and hydrogen peroxide is a necessity. The addition of methylene blue is described in the U.S. Patent. 2 587 905 to increase the selectivity of the oxidative degradation, but the removal of this additive is as difficult as the removal of anthraquinone-2-sulfonate (AMS). The reaction in the presence of AMS requires an extensive processing procedure to completely remove AMS from the substrate. FR 2 722 200 mentions the treatment with granulated active carbon, but without explaining the procedure or the results obtained. There is a need for an economically valuable method for producing high yield arabinitol, comprising reaction steps that give intermediates with a low level of impurities (e.g., good selectivity of the reaction), and which do not require extensive purification (e.g. that may be needed due to the addition of reagents that are not easily removed from the final product). Preferably, said reactions should start from already available substrates, ie, hexoses and should be carried out at low pressure, that is, less than about 6 bar and in the absence of AMS or other substance that is difficult to remove. The present invention provides a co-or such method.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pentitol, i.e., D-arabinitol from a hexose, characterized in that the method comprises oxidative decarboxylation followed by catalytic hydrogenation, preferably the method comprises the following steps; a) oxidative decarboxylation of a hexose to give a Cs intermediate consisting mainly of an alkali metal aldonate, b) crystallization of the alkali metal Cs aldonate, c) protonation of the alkali metal salt to the corresponding free acid, d) optionally crystallization of the Cd aldonolactone, e) hydrogenation of the aldonic acid (above) to the corresponding pentitol. The starting material is a hexose such as glucose (high dextrose, monohydrate, anhydrous (starch hydrolysate) syrups), and / or galactose, invert sugar or lactose hydrolyzate. In a preferred embodiment of the present invention, hexoea is glucose and the product is arabinitol.

The oxidative decarboxylation ee carried out at an oxygen pressure between 0.5 and 10 bar, preferably between 1 and 6 bar, very preferred between 2 and 5 bar. The reaction is carried out in the absence of anthraquinone derivatives and without the addition of orgone solvents. The product of oxidative decarboxylation can be hydrogenated without extensive purification. The method of the present invention is characterized in that in step a) it is an oxidative decarboxylation reaction without the addition of anthraquinone derivatives and without the addition of organic solvents, at low oxygen pressure, and optional addition of hydrogen peroxide. The crystallization step is carried out directly from water or from mixtures of water / alcohol, preferably water. The protonation is carried out using ion exchange resins, preferably strong ion exchange resins (cation exchange). Another part of the present invention is that the hydrogenation is carried out in the presence of a hydrogenation catalyst, preferably a ruthenium-based catalyst with a temperature for hydrogenation between 100 and 170 ° C, preferably between 110 and 150 ° C , very preferred between 120 and 140ßC. Hydrogenation is promoted by the addition of acids, preferably phosphoric acid or boric acid.

DESCRIPTION OF THE FIGURES Figure 1 shows a schematic presentation of the method of the present invention. Figure 2 shows the purity effect of substrate in hydrogenation of aldonic acid. Figure 3 shows the effect of the addition of AMS during the hydrogenation of aldonic acid. Figure 4 shows the effect of formic acid on the hydrogenation of aldonic acid. Figures 5 and 6 show the effect of inorganic salts and residual organic salts and acids in the hydrogenation of aldonic acid. Figure 7 shows the positive effect of phosphoric acid and boric acid on hydrogenation.

DETAILED DESCRIPTION OF THE INVENTION Basically, the method of the present invention demonstrates that it is possible to perform oxidative decarboxylation of a hexose under low pressure in the absence of AMS and with retention of selectivity. The presence of AMS makes it possible to carry out a catalytic hydrogenation in the product without requiring extensive purification. The present invention can be summarized as follows. The invention describes the oxidative decarboxylation of Ce carbohydrates to alkali metal Cs alonates. Oxidative decarboxylation is carried out at low oxygen pressure, optionally with the addition of hydrogen peroxide, but without the addition of other organic additives such as, for example, anthraquinone derivatives or β-ethylene blue. The process of the present invention can be carried out without organic solvents and a very substantial substance from the substrate while retaining the specificity of reaction. Starting with glucose (syrups with high dextrose content), monohydrate, anhydrous), and / or fructose or invert sugar, the oxidative decarboxylation produces alkali metal arabinonate. Starting with glucose, the product of the present process is lixonate, and the lactose hydrolysates give after oxidative deecarboxylation mixtures of lixonate and arabinonate. In accordance with the present invention, it is possible to apply low oxygen gas pressure without adding anthraquinone or rnetylene blue derivatives, and without the use of organic solvents, and still obtain good reaction selectivity. In particular, these anthraquinone derivatives are harmful to the next reaction step in the present process, for example, the hydrogenation of arabinonic acid to arabinitol in the presence of ruthenium-based catalysts. The reaction in the presence of AMS requires an extensive processing procedure to completely remove AMS from the substrate. FR 2 722 200 mentions the treatment with granulated active carbon, but without explaining the procedure or the results obtained. However, as shown in the examples of the present invention, treatment with active carbon alone is not sufficient to completely remove all traces of AMS. The complete removal of anthraquinone-2-sulfonic acid is required, since any trace of AMS poisons the ruthenium-based catalyst, applied for the hydrogenation of arabinonic acid in arabinitol. Therefore, it is evident that the reaction as described in FR 2 722 200 is not possible and the product will then be hydrogenated in the presence of certain catalysts. Several methods have been described for the removal of AMS from aqueous solutions: 3. Kiwi and others New. 3. Chem. 1993, 17 487-494 describe the heterogeneous photocatalytic degradation by means of titanium dioxide powder. In "Applied Catalysis B: Environmental 1997 3_ 85-99" 3. Kiwi et al. Describe homogeneous photocatalytic degradation by means of hydrogen peroxide and iron ions. 90% of the AMS is degraded in 3 hours, but a total of 15 hours is required for complete removal. A. T. Hunter describes in "3. Chrornatogr, 1985 319 319-330" the separation of sulfonic acid from anthraquinone using inverted phase HPLC in the presence of quaternary ammonium salts as ion pair agents. The interaction of ion pairs is demonstrated in the present invention as being by far the best technique but difficult to handle to remove all traces of antininin-2-sulonic acid. The present invention describes the production of arabinitol starting from glucose in a high yield at the same time working at a pressure between 0.5 and 10 bar, preferably 1 to 6 bar, very preferred 2 to 5 bar, without the addition of AMS and in absence of organic solvents. Reactions without the addition of AMS give products that can be easily processed by crystallization of the alkali metal aldonate, and protonation with a known treatment of ion exchange. In order to bring the oxidation decarboxylation reaction medium to the required alkaline pH, calcium hydroxide, potassium hydroxide or sodium hydroxide are most commonly used. Calcium hydroxide has already been described for this purpose and has the advantage of allowing easy crystallization of the resulting calcium arabinonate, but has the disadvantage of practically dosing the calcium hydroxide to the reaction medium when low oxygen pressures are applied. Potassium hydroxide or sodium hydroxide can be easily added to the reaction medium. The alkali metal arabinonates, such as potassium arabinonate and sodium arabinonate, are crystallized from the reaction medium by adding methane to the concentrated reaction medium. In the present invention, potassium arabinonate can be crystallized from the reaction medium, after concentrating the mixture to a very dry substance, but without adding additional methane. To be able to crystallize sodium arabinonate in high crystalline performance, an ion exchange treatment is required first to bring the pH of the crude reaction medium from 13 to 8, preferably 7, as described by 3. Dubourg et al. "Bull. Soc. Chim. France 1959 1353-1362" In the present invention, the use of methane is omitted. The crystallization step that is optional is in fact a purification step to remove all traces of formate, glycolate and finally the traces of erythronate present. Because it is not possible to hydrogenate the aldonate salt, it must be converted to the corresponding free acid or lactone. Several methods can be applied for this purpose, for example, using concentrated sulfuric acid as described in FR 2 722 200. However, the final product must be free of any salt, since the most common salts, organic and inorganic salts , poison the hydrogenation catalyst. All traces of potassium perchlorate, potassium chloride, potassium sulfate and sodium acetate have a delay or inhibitory effect on the hydrogenation of aldonic acids. All other organic acids, such as tartaric acid, lactic acid and malic acid delay the respective hydrogenation reaction. Knowing this, the protonation of alkali metal aldonate to the corresponding aldonic acid is preferably done by applying strong ion exchange resins. Finally, arabinonic acid is hydrogenated in the presence of ruthenium-based catalysts. The present invention is illustrated by a series of examples. The examples indicate that it is perfectly possible to perform oxidative decarboxylation at low pressure and with high selectivity without the use of a redox catalyst such as AMS or organic solvent added. Example 1 demonstrates that the combination of AMS and hydrogen peroxide can be replaced with oxygen and that when the reaction is carried out at slightly elevated pressure, the molar yield of the product is of the same order as when AMS and hydrogen peroxide were used. In addition, it is shown that the reaction can be carried out at very dry substance concentration. Preferably, the reaction is carried out up to 10% dry substance, very preferred up to 20 or even 30%. However, the advantage of the present process is more evident if the catalytic hydrogenation step is considered. Example 2 shows that extensive purification of the arabinonate is required in order not to influence the subsequent hydrogenation, especially when AM ?. Figure 2 and the subsequent figures show the decrease in the amount of arabinonic acid in time where the starting amount is set to 100%. Figure 2 shows that as the arabinonic acid is cleaner, the amount of arabinonic acid decreases more rapidly. Thus, the performance increases and the completion reaction time decreases. The repeated crystallization gives a product of a purity with good performance in hydrogenation. Treatment with tridodecyl ina "ja still results better as seen in Figure 2. As a control experiment, AMS was added to a hydrogenation mixture resulting in a clear inhibition of the reaction. (Figure 3). In addition, the presence of anthraquinone derivatives such as anthraquinone-2-sulfonic acid also inhibits the hydrogenation reaction. For comparative purposes, an attempt was made to remove the AMS using active carbon. The result shows that it is very difficult to remove AMS in this way. Example 3 demonstrates that by using pure subetrato, the reaction temperature can be lowered from 150 to 135 ° C. At lower temperature, it decreases the amount of cracking, while the reaction time is not influenced to a large degree. Finally, it was shown that trace amounts of inorganic acids, or saltse, are included in the hydrogenation reaction. The hydrogenation reaction is stimulated by the addition of foorphoric or boric acid (example 4). It could be concluded that the present invention meets all the purity requirements to obtain good hydrogenation selectivity without catalyst poisoning. The advantages of this method in comparison with the processes described above such as the part of the process described in the international patent application UO 93/19030, are low processing costs, easy handling and easy processing of the reaction product due to the combination of the following steps: 1. an oxidative decarboxylation applying only depresses of oxygen gae without the addition of anthraquinone derivatives or the addition of solvents organic, optionally with the addition of hydrogen peroxide. 2. Crystallization preferably from water without the addition of organic solvents. 3. Protonation by applying ion exchange resin to release the product from all traces of foreign ions. 4. Hydrogenation in the presence of ruthenium-based catalysts and obtain good selectivities, due to the absence of poisoning impurities. The process of the present invention is shown schematically in Figure 1. The invention is further illustrated by the following examples.

EXAMPLE 1 OXIDIZING DESCflRIX Oxidative decarboxilation applying 2-bar oxygen pressure gas A glucose solution (1.5 kg -10% solution by weight / weight) is heated at 45 ° C in a two-liter autoclave, stirring at the same time at 1000 rpm. The reactor containing the glucose solution is purged twice for 0.5 minutes with 1 barium oxygen pressure gas. After purging, the oxygen pressure in the reactor is adjusted to 2 bar. The reaction begins by dosing the potassium hydroxide solution (242 g - 50% solution by weight / weight) with a dosing specimen to the glucose solution using a rate of 1.3 mols of KOH / hour. The total dosage time required is 1.7 hours. The reaction mixture is stirred for a total reaction time of 5 hours, including the dosing time of the alkali. The product is determined by HPLC analysis (see table 1).

Comparative example with the use of flMS and hydrogen peroxide and oxygen gas at atmospheric pressure A glucose solution (1.5 kg 10% solution by weight / weight) is heated at 45 ° C in a two liter loading reactor, stirring at the same time at 1000 rpm. During heating, the glucose solution is saturated with oxygen gas. The oxygen gas is bubbled through the reaction mixture at a flow rate of 0.2 1 / min. The oxygen level in the solution is measured by an oxygen electrode. Anthraquinone-2-sulfonate (AMS - 2.25 g) and hydrogen peroxide (0.78 g - 30% solution by weight / weight) are dosed simultaneously to the glucose solution, before the addition of any alkali. The reaction begins by dosing the potassium hydroxide solution with a peristaltic pump to the glucose solution using a dosing rate of 0.9 moles KOH / hour. The total alkali dosing time requires 2.8 hours. After the alkali dosing, the reaction continues until a color change from red-brown to white is observed, due to the redox reaction of the AMS catalyst. The total reaction time for glucose decarboxylation, including the alkali dosing time, is 5.5 hours. The product is determined by HPLC analysis (see Table 1). The procedure is repeated, but oxygen gas is replaced by air at atmospheric pressure. The product is determined by HPLC analysis (see Table 1).

Comparative example with oxygen pressure of 2 bar and addition of AMS and hydrogen peroxide The procedure is similar to the first description, AMS and hydrogen peroxide are added simultaneously before purging with oxygen gas. The product is determined by HPLC analysis (see Table 1).

Comparative example with oxygen pressure at 2 bar and addition of hydrogen peroxide A solution of starch hydrolyzate, containing 95% glucose (30% weight solution / peeo), is heated at 35 ° C in a two liter autoclave, while stirring at 1000 rprn. 0.2% hydrogen peroxide is added and the reactor containing the glucose solution is purged twice for 0.5 minutes with 1 barium oxygen pressure gas. After purging, the oxygen pressure in the reactor is adjusted to 2 bar. The reaction begins by dosing the potassium hydroxide solution (50% solution by weight / weight) with a dosing specimen to the glucose solution using a dosing rate of 0.5 mol KOH / hour. The total dosing time requires 8 hours. The product is determined by HPLC analysis (see Table 1).

CUflDRO 1 Arabinonate of molar yield obtained with AMS H2O2 O2 at air pressure at pressure O2 at atmospheric atmospheric pressure of 2 bar + + 95% 80% 94% 55% 88% + 83% To demonstrate the applicability of this method even to a drier substance, the first description, applying oxygen pressure of 2 barium at 40 ° C, is followed for 10% glucose solutions., 20% and 30% dry substance. The glucose solution is heated at 40 ° C in a two liter autoclave, stirring at the same time at 1000 rpm. The reactor containing the glucose solution is purged twice for 0.5 minutes with oxygen gas at a pressure of 1 barium. After purging, the oxygen pressure in the reactor is adjusted to 2 barium. The reaction begins by dosing the sodium hydroxide solution (45% solution by weight / weight) with a doeification probe to the glucose solution using a rate of 0.65 mole of NaOH / hour.

FIGURE 2 % of dry substance Arabinonate of yield rnolar 10% 89% 20% 87% 30% 80% EXAMPLE 2 PURIFICATION OF ORPHlBINONflET (OBTAINED BY FLUIDING FROM OXIDIZING DESCflRlOXlFlATION IN THE PRESENCE OF FLflS, FOLLOWED BY PROTONATION AND HYDROGENATION FL ARABINITOL Crystallization The potassium arabinonate obtained in accordance with Example 1 and in the presence of AMS is crystallized first from methane / water. The crude reaction mixture (approximately 10% dry substance) is filtered on a paper filter in order to remove all of the insoluble AMS catalyst. After filtration, the reaction medium is concentrated at 70 ° C under reduced pressure until a concentration of 40% dry substance is obtained. The concentrated reaction mixture is precipitated in an equal weight of methane. The precipitated potassium arabinonate is collected by filtration. The collected potassium arabinonate is washed twice with methane and dried at room temperature. Eetoe crystals have a purity of 96.9% (measured with HPLC analysis). Eeta purity is insufficient for the next p > hydrogenation. (See figure 2, the substrate for hydrogenation has been protonated using resin Mitsubishi UBK 550).

Recrystallization A 50% solution of dry potassium arabinonate substance precipitated with methane in water is prepared by heating the mixture to 95 ° C. The hot solution is filtered once more to remove the residual insoluble parts of AMS. The hot solution is cooled slowly, stirring the solution at the same time. The crystals of potassium arabinonate are collected by filtration. The crystals are dried at room temperature (harvest 1). The mother liquors are concentrated to 50% of the dry substance and a second harvest of crystals is collected (harvest 2). Both crops are harvested once more to perform a second recrystallization applying the same conditions as for the first recrystallization. The purity of the crystals collected is 100%. See figure 2 to observe the hydrogenation profile (the substrate for hydrogenation has been protonated using Mitsubishi UBK 550 resin). However, this product is not yet free of all traces of AMS, and AMS is harmful to the catalyst. During one of the hydrogenation tests, anthraquinone-2-sulfonate was added to the pure substrate to visualize the damaging effect of AMS (Figure 3).

Removal of residual a raqui ona-2-sulfonic acid by ion pair interaction Crystals collected with 100% purity, determined by HPLC analysis, are protonated using Mitsubishi UBK 550 resin. To 200 g of 50% solution by weight / weight of arabinonic acid, containing traces of anthraquinone-2-sulfonic acid, 3.18 g of tridodecyl ina was added. Shake during minutes at room temperature and add 2 g of active carbon. Shake the whole solution for half an hour at 70 ° C.

Cool to room temperature and filter the solution over a 0.45 μm filter. This product is concentrated to be applied in the consecutive hydrogenation or can be further concentrated to 70% dry substance to crystallize the corresponding arabinolactone. This product is free from AMS and the hydrogenation profile shows the improvement compared to the substrate that arises from three consecutive crystallisations (Figure 2). 9? Application of active carbon to remove anthraquinone-2-sulphonic acid Take the reaction mixture that arises from an oxidative decaboxylation in the presence of 0.2% AMS. The crude reaction mixture, at pH = 12 (approximately 10% dry substance), is filtered on a paper filter in order to remove all the insoluble AMS catalyst. Still 318 ppm of AMS, which is determined photometrically at 330 n, reside in the product. This product is treated with 0.5% active carbon and stirred for 1 hour at 80 ° C. After filtering on a 0.45 μm filter, still 48 ppm of AMS remain in the product. As a comparative test, the product containing 318 ppm of AMS is treated, at pH = 12, with active carbon and tridodecylamine (see above procedure) and under these conditions, that is, pH = 12, the actual AMS content is reduced at 22 ppm. Treatment with tridodecylamine is sometimes as good as treatment with active carbon alone.

Hydrogenation 110 g of arabinonic acid is dissolved in 440 ml of water, and it is taken in an autoclave under pressure. 6% Rut 5%) / C is added to the solution and the reaction medium is heated to 150 ° C. The reaction starts by pressurizing the autoclave with 40 bar hydrogen gas. The reaction is stopped half an hour after observing the complete absorption of hydrogen. In general, the reaction continues for 5 to 6 hours under the reaction conditions mentioned previously (see Table 3).

EXAMPLE 3 PURIFICATION OF ARflBINONflT (OBTAINED FROM FLUID OF OXIDANT DESCFLUXILFlATION WITHOUT FLMS). FOLLOWED BY PROTONflTION AND HYDROGENflCTION fl ARflBINITOL Crystallization Before crystallizing the alkali metal arabinonate (being sodium arabinonate or potassium arabinonate), the crude reaction mixture is brought to pH = 7 with the aid of ion exchange resin (for example, Lewatit S2528). The resulting reaction mixture (pH = 7) is concentrated under reduced pressure at 50 ° C to 70% dry substance. The crystals are collected by filtration or centrifugation and are dried at room temperature. Sodium arabinonate is obtained in 95-97% purity and potassium arabinonate is obtained in 98-99% purity. The remaining impurities are glycolate and formate.

Recrystallization The collected crystals are dissolved once more in water to obtain 70% of a solution. Cooling at room temperature allows the crystallization of sodium arabinonate, obtained in 100% purity. This recrystallization is almost always required to remove all traces of forrniato. Complete removal is required since any trace of formic acid poisons the catalyst (Figure 4).

Hydrogenation The cracks thus obtained are protonated by applying ion exchange resin (for example, Lewat.it S2528). 110 g of arabinonic acid is dissolved in 440 ml of water, and it is taken in an autoclave under pressure. 6% Ru (5%) / C is added to the solution and the reaction medium is heated to 135 ° C. The reaction starts by pressurizing the autoclave with 40 bar hydrogen gas. The reaction is stopped half an hour after observing the complete absorption of hydrogen. In general, the reaction continues for 6 hours under the reaction conditions mentioned previously. Using completely pure substrate, the reaction temperature of the hydrogenation can be reduced from 150 ° C to 135 ° C, while the reaction time is not extended. This reduction in the reaction temperature has a significant effect on the cracking reactions that occur apart from the hydrogenation of arabinonic acid (see Table 3). The reaction products are analyzed by HPLC.

TABLE 3 Substrate Temperature Acid Time Pentitoles Agri_ from source * of reaction reaction res. etarn + AMS 130 lh30 20% 69% 11% + AMS 150 5h30 0% 84% 16% -AMS 150 5h 0% 88% 12% -AMS 140 5h 4% 85% 11% -AMS 135 6h 3% 89% 8% -AMS 130 7h 3% 90% 7% -AMS 125 lOh 2% 92% 6% * describes where the substrate arises: oxidative deecarboxylation reaction with or ein anthraquinone-2-sulphonic acid (AMS).

EXAMPLE 4 PROTONATION WITH ION EXCHANGE RESIN The protonation of alkali metal arabinonate to arabinonic acid is preferably carried out with ion exchange resin (for example, Mitsubishi UBK 550, Lewatit S2528). After protonation with common inorganic acids (for example, sulfuric acid, hydrochloric acid, perchloric acid) the inorganic ealee trazoe remain on the substrate for hydrogenation and inhibit the hydrogenation catalyst. Protonation is not possible with the help of organic acids, since most of them poison the hydrogenation catalyst. The ruthenium bake catalysts, applied for this hydrogenation, are sensitive to any salt trace (see figures 5 S 6). The ruthenium-based catalyst is promoted by the addition of phosphoric acid or boric acid (Figure 7).

Claims (8)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for producing arabinitol from glucose (syrups with a high content of dextroea, monohydrate, anhydroe (starch hydrolyzate)) and / or fructose, and / or galactose, or lactose hydrolysates, or invert sugar also characterized in that the The method comprises the following steps: a) oxidative decarboxylation of a hexose to give a Cs intermediate consisting mainly of an alkali metal aldonate, b) crystallization of the alkali metal Cd aldonate, c? protonation of the alkali metal salt to the corresponding free acid, d) optionally crystallization of the Cd aldonolactone, e) hydrogenation of the aldonic acid (above) to the corresponding pentitol.

2. The method according to claim 1, further characterized in that step a) is an oxidative deecarboxylation reaction without the addition of anthraquinone derivatives and without the addition of organic solvent, low oxygen pressure, and optional addition of hydrogen peroxide.

3. The method according to claim 2, further characterized in that the oxygen pressure is between 0.5 to 10 bar, preferably between 1 to 6 bar, most preferred between 2 to 5 bar.

4. The method according to claim 1, further characterized in that step b) is carried out directly from water or water / alcohol mixtures, preferably water.

5. The method according to claim 1, further characterized in that step c) is carried out using ion exchange resins, preferably strong ion exchange resins.

6. The method according to claim 1, further characterized in that step d) is carried out in the presence of a hydrogenation catalyst, preferably a ruthenium-based catalyst.

7. The method according to claim 6, further characterized in that the temperature for hydrogenation is between 100 and 170 ° C, preferably between 110 and 150 ° C, preferably between 120 and 140 ° C.

8. The method according to claim 6 or 7, further characterized in that the hydrogenation is promoted by the addition of acids, preferably phosphoric acid or boric acid.