FI101879B - Process for the preparation of epimer free sugar alcohols from the group xylitol, sorbitol (D-glucitol), 4-O- -D-galactopyranosyl-D-glucitol and 4-O- -D-glucopyranosyl-D-sorbitol - Google Patents

Description

1U18 / 9

Process for the preparation of epimer-free sugar alcohols belonging to the group of xylitol, sorbitol (D-glucitol), 4-O-β-β-galactopyranosyl-D-glucitol and 4-O-O-D-glucopyranosyl-D-sorbitol 5

The invention relates to a process for the preparation of the title sugar alcohols in epimeric form from the corresponding sugars, xylose, oD-glucose, 4-O-6-D-galactopyranosyl-αD-sorbitol or 4-O-α-D-glucopyranosyl-αD-glucuvyrellone by catalytic hydrogenation with hydrogen. The reaction flow can be shown by the following reaction schemes:

, c H-C = O CHoOH

15 I I

H-C-OH H-C-OH

I I

HO-C-H H7 HO-C-H

I -5—> I

H-C-OH H-C-OH

I I

20 CH2OH CH2OH

D-xylose Xylitol 25 I-

H-C-OH CH 2 OH

I I

H-C-OH H-C-OH

I I

HO-C-H O Ho HO-C-H

I I

H-C-OH H-C-OH

30 I I

H - C- H-C-OH

I I

ch2oh ch2oh α-D-glucose Sorbitol (D-glucitol) 35 2 101879

CHoOH

I 2

-C-H

, - I

H-C - 0 - C-H

5 1 1 5 HO-C-H H-C-OH H? I o I —5-.

H-C-OH O HO-C-H

I I

H-C-OH H-C-OH

I 'H-C-

10 I

ch2oh 4-Ο-β-D-galactopyranosyl-α-D-glucopyranose i (lactose, milk sugar) ch2oh 15 I 2

HO-C-H

.- I

H-C - 0-C-H

I I

HO-C-H H-C-OH

I I

H-C-OH O HO-C-H

20 I I

H-C-OH CH, OH

I 2 H-C- ch2oh • 25 4-O-β-D-galactopyranosyl-D-glucitol (lactitol) I- H-C - I-

I H-C-OH

H-C-OH I

I M-C-OH

HO-C-H O O I

30 I HO-C-H O H2 H-C-OH I -► I H-C-1 H-C- 1-1 I H-C-

ch2oh I

ch2oh 1 4-O-α-D-glucopyranosyl-α-D-glucopyranose (maltose) 3 101879

H-C - CH 2 OH

I I

H-C-OH HO-C-H

I I

5 HO-C-H O O-C-H

I I

H-C-OH H-C-OH

I I

H-C- HO-C-H

ch2oh ch2oh 10 4-O-α-D-glucopyranosyl-D-sorbitol (maltitol) These four epimer-free sugar alcohols according to the invention are known and can be described as follows:

The sweetening power of xylitol is about 80-100% of that of sucrose. To increase the sweetening ability, artificial sweeteners, for example cyclohexyl sulfamate 20 or phenylalanine aspartic acid methyl ester, can be added to the aqueous solution of xylitol, and the mixture is recovered as a crystalline by co-crystallization in vacuo. However, artificial sweeteners can also be mixed in solid form with xylitol crystals. Xylitol can also be mixed in solid or liquid form with other sweet-tasting carbohydrates, for example maltitol, lactitol, sorbitol and the like.

Due to its pleasant sweet taste, xylitol is suitable as a sugar substitute in the diet of diabetics and as a non-rot-inducing sweetener in confectionery and oral pharmaceutical products. For foods for diabetics, xylitol is permitted without restrictions by the Diet Ordinance (Rundes-gesetzblatt I 1982, page 7).

Pure xylitol is particularly well suited for blended confectionery such as caramels and chewing gum (Swiss 4 101879

Dent I (7/8) 1980, pages 25-27). Products used for oral and pharyngeal treatment, such as toothpastes, pharyngeal disinfectant tablets, cough drops, are also increasingly sweetened with xylitol (Swiss Dent. Ill. (7/8) 5 1982, pp. 25-30).

The human body is only able to resorb sorbitol to a small extent and only this part of it is broken down. For this reason, sorbitol is suitable as a sugar substitute and low-calorie sweetener for diabetics. In addition, it 10 causes less tooth decay than glucose or other sugars.

The sweetening power of sorbitol is about 50-60% of that of sucrose. To increase the sweetening ability, artificial sweeteners, for example cyclohexyl sulfamate or phenylalanine aspartic acid methyl ester, can be added to the aqueous solution of sorbitol, and the mixture crystallized by co-crystallization in vacuo. However, artificial sweeteners can also be mixed in solid form with sorbitol crystals. Sorbitol 20 can also be mixed in solid or liquid form with other sweet-tasting carbohydrates, for example, maltitol, lactitol, xylitol, and the like.

Even long-term studies have not been able to demonstrate toxic effects (Ullmanns Encyklopädie der 25 technischen Chemie, Vol. 24, Weinheim 1983, p. 774), so the potential use of sorbitol in foods as a manufacture of diabetic products and low-nutrition sugar-free sweets and foods is limited.

Xylitol or sorbitol is often prepared by a batch process using a powdered nickel catalyst in the form of a suspension.

Lactitol is not degraded in the human body as a carbohydrate 35 and is not hydrolyzed or absorbed in the small intestine. Thus, 5 101879 lactitol is suitable as a sugar substitute for diabetics. In addition, it is less likely to cause tooth decay than sucrose.

The sweetening power of lactitol is about 40% of that of sucrose 5. to increase the sweetening ability, artificial sweeteners, for example cyclohexyl sulfamate or phenylalanine aspartic acid methyl ester, may be added to the aqueous solution of sorbitol, and the mixture crystallized by co-crystallization in vacuo. However, artificial sweeteners can also be mixed in solid form with lactotol crystals. Lactitol can also be mixed in solid or liquid form with other sweet-tasting carbohydrates, for example fructose, sorbitol, xylitol and the like.

15 Even long-term studies have not been able to show toxic effects (Ullmanns Encyklopädie der technischen Chemie, Vol. 24, Weinheim 1983, p. 779). thus, the potential uses of lactitol in foods for the manufacture of diabetic products as well as low-nutrition blind-20 free sweets and foods are diverse.

Lactitol, which has not hitherto been found in nature, can be prepared according to the known batch process 25 according to EP 39 981, which uses a powdered nickel catalyst in a slurry process.

Maltitol is only difficult to break down in the human body by amylocytic enzymes. Thus, maltitol is suitable as a sugar substitute for a low-calorie diet and for diabetics (Ullmanns's Encyklopädie der tecnischen Chemie, Vol. 24, Weinheim 1983, p. 771).

The sweetening power of maltitol is in the order of magnitude of sucrose. Maltitol can be mixed in liquid form with other sweet-tasting carbohydrates, for example, fructose, sorbitol, xylitol, and the like. The use of maltitol in the beverage industry is particularly advantageous due to its high sweetening ability and low tendency to crystallize, even at high concentrations.

Maltitol, which has not hitherto been found in nature, can be prepared according to the known batch process of U.S. Pat. No. 3,741,776, which uses a powdered nickel catalyst in a slurry process.

The disadvantage of discontinuous processes is that their capacity in terms of reaction volume is quite small and thus they require large reaction equipment and storage tanks. The need for energy is uneconomical and the need for staff is relatively high.

Continuous powder catalyst processes.

15 using several cascaded hydrogenation reactors avoid some of said disadvantages. However, the difficult activation, pumping out and quantitative filtration of the powdered catalysts remain difficult to get rid of the reaction product. Catalyst -20 sludge pumps are subjected to high mechanical stress. Quantitative removal of the powdered catalyst is cumbersome (alternating coarse and fine filtration equipment). In addition, there is a high risk that the catalyst will lose its activity relatively quickly (high catalyst consumption) due to these additional measures. Thus, the reaction is carried out with fixed catalysts which have a high specific activity and do not decrease even for a long period of time from one year to several years, since frequent catalyst changes in the fixed bed reaction are also expensive.

Also in the case of stationary catalysts, it is customary to connect several reactors in series, as a result of which several reaction zones are connected in series (DE application 3 214 432).

Suitable for use are supported (SiO 2 / Al 2 O 3) nickel catalysts with a very high active surface area (140-180 m 2 / g) so that the catalysts are so active that they must also be stabilized by chemical treatment methods, for example by oxygen gas treatment with monomolecular to form an oxygen layer on the surface of the catalyst (DE-A-10 3 110 493). However, the deactivating stabilization of the catalyst necessitates the use of such high temperatures in the hydrogenation of sugars (130-180 ° C) that uncontrolled side reactions such as caramelization of saccharide alcohols and hydrogenation cleavage (hydrogenolysis) and the formation of methanol and even methane are possible. In addition, in this reaction method, heavy metals such as nickel, iron or cobalt are always transferred in ionic form or in colloidal solution, which on the one hand requires the subsequent treatment of the hydrogenated product with activated carbon and on the other hand the removal of ions by ion exchangers.

Since the known hydrogenation methods are carried out in sugar solutions adjusted to pH 7-13, alkalis or alkaline earths must be added to the starting solutions, which again have to be difficult to remove from the final product (DE-A-3 110 493, 3 214 432).

In addition, significant epimerization is expected to occur under hydrogenation conditions, so that, for example, in addition to xylitol, lysitol 30 (arabinitol and ribitol) is also obtained from D-xylose; In addition to sorbitol, α-D-glucose would also give mannitol.

In addition, cleavage of the carbon chain of sugars by Raney nickel in catalytic hydrogenation is known; DE-A-2 756 270 describes this effect in a formulation of 8 101879 sugar formed by self-condensation of formaldehyde, in which case a clear transition from higher to lower C-chain numbers can be observed according to the embodiments described therein. According to DE-A-2 831 659, no such cleavage is observed with the noble metal catalysts of the 8th side group 5.

EP 152 779 discloses a process for the hydrogenation of α-D-glucopyranosido-1,6-fructose with a solid support catalyst. However, a mixture of two reduction products is obtained, namely a mixture of α-D-10 glucopyranosido-1,6-mannitol and α-D-glucopyranosido-1,6-sorbitol in a ratio of approximately 1: 1.

Thus, it would be surprising that with the process of the present invention the sugars not only react almost completely, but that the reaction yields ether formation, avoiding epimerization and C-chain cleavage, and avoiding the formation of higher molecular weight components due to condensation reactions. . This is important because the product can be used immediately without further purification as a nutrient.

The present invention relates to a process for the preparation of epimer-free sugar alcohols belonging to the group of xylitol, sorbitol (D-glucitol), 4-O-SD-galactopyranosyl-D-glucitol (lactitol) and 4-OaD-glucopyranosyl-D-sor-25 bitol (maltitol). by hydrogenation of the corresponding sugars, D-xylose, α-glucose, 4-OSD-galactopyranosyl-α-glucopyranose or 4-Oo-D-glucopyranosyl-α-D-glucopyranose in an aqueous solution with hydrogen at elevated pressure and elevated temperature. The process is characterized in that the hydrogenation is carried out continuously at a hydrogen pressure of 10,000 to 50,000 kPa and at a temperature of 60 to 125 ° C by a fixed bed process in one reaction zone over support-free shaped capsules acting as hydrogenation catalysts with a compressive strength greater than that of the surface. 50 N, preferably 100 to 400 N, and having an internal surface area of 10 to 90 m 2 / g and consisting of one or more elements belonging to the iron group of the Periodic Table.

According to the present invention, epimer-free sugar is defined as sugar alcohols whose epimer content can be disregarded insofar as these sugar alcohols, without further purification, meet the commercial regulations set forth in Deutsches Arzneimittebuch (DAB) and the United States Pharmacopeia (USP) and Food Chemicals Code. (FCC).

By the process of the invention, sugar alcohols 15 are obtained in almost quantitative yield. This is particularly important because the removal of higher molecular weight (hydrogenated) or lower molecular weight (hydrogenolysis) interfering impurities from the reaction product 20 by additional purification measures, such as recrystallization from solvents, normally significantly increases environmental damage. Of the sugar alcohols of the epimeric sugar alcohols type with xylitol, up to 25 traces (total <0.3%) can be detected in the reaction product. There are at most traces (<0.3%) of diastereomeric mannitol with sorbitol in the reaction product. With lactitol, the diastereomeric 4-O-S-D-galatopyranosyl-D-mannitol and with maltitol, the diastereomeric 4-O-α-D-glucopyranosyl-D-mannitol could not be detected in the corresponding reaction products.

In contrast to supported catalysts, the solid bed catalysts used according to the invention are not prone to "breakthrough", i. they do not transfer catalyst materials in the form of ions or colloids to the solvent phase of the substrate, since heavy metals do not enter the substrate as impurities, which can also normally be removed from the substrate only with difficulty, for example by increasing the ecological load with ion exchangers. After use, the catalysts can be easily regenerated because no separation of heavy metals from the support is required. In addition, in the case of polyhydroxy compounds, the possible formation of complex chelating compounds which could only be removed from solutions with difficulty was feared.

Thus, it is possible to produce the respective sugar alcohol with a purity of the dry matter of more than 99% by the method 10 according to the invention. The unreacted sugar content smokes values of less than 0.2% or less. Because the glycosidic ether bonds of the disaccharides are preserved, the concentrations of monosugar alcohols are only 0.3% or less. Commercial quality requirements for sugar-15 alcohols (e.g., DAB, USP, and FCC) can thus normally be directly met without further purification.

The starting material used in the process according to the invention is pure crystalline D-xylose or, respectively, pure α-D-glucose or pure α-lactose or α-lactose monohydrate or pure maltose (in liquid or B form, also as crystalline monohydrate). The starting material is dissolved in oxygen-free deionized water to give 15 to 45% by weight, preferably 35 to 40% by weight. 25% solution with a pH of 3.5 to 10.5. The solution of monosaccharides is preferably adjusted to pH 3.5 to 8, the solution of disaccharides is preferably adjusted to pH 5.5 to 10.5. A particularly preferred pH for all starting materials is 6 to 7.5. Aqueous solutions of said starting sugars have a neutral pH of 7 or are weakly acidic due to the formation of (traces) of sugar acids, but the solutions can be adjusted to the desired pH in a manner known per se, for example by adding sorbic acid or citric acid.

Pure hydrogen is used for the hydrogenation according to the invention, which is pre-pressurized to a pressure of 10,000 to 11,101,879 to 50,000 kPa, preferably 15,000 to 30,000 kPa. The hydrogenation is carried out by a continuous fixed bed process using the catalysts described below, either by passing the solution to be hydrogenated in a parallel stream from below 5 together with premixed hydrogen over the catalyst packed in the hydrogenation reactor (downstream process) or by passing a bottom-up upstream hydrate solution.

The hydrogenation reactor can be either a single high-pressure pipe made of steel or steel alloy, which is completely or partially filled with a catalyst, whereby in certain pipe cross-sections the catalyst can advantageously also be used with gratings (wire baskets, etc.) or with a jacketed high-pressure pipe bundle. a catalytic converter. In addition, instead of one large can reactor, equipment connected in series from several small individual tubular reactors can be used.

Support-free catalysts are prepared in shaped form from the elements of the iron group of the Periodic Table, in particular nickel, cobalt or their alloys or alloys with each other or with iron, particularly preferably nickel or alloys containing at least 70% nickel. In this case, powders of said individual metals or ground alloys thereof are suitable for use. The shaped bodies are produced by conventional methods by compressing the metal powder under high pressure, for example in a tableting or pelletizing machine, whereby graphite and / or adhesives can also be added in amounts of 0.5 to 3% by weight of the total catalyst-forming components to improve the adhesion of metal particles. The shaped bodies are made in an oxygen-free state in order to avoid oxidation of the surface. Examples of shaped articles are tablets, pellets or granules with a diameter of 3 to 7 mm. In addition, the tableted shaped bodies can be provided with an axial hole (hole core) in order to enlarge the outer surface. The surface of such shaped bodies 5 is smooth when viewed macroscopically.

The shaped catalysts according to the invention must be manufactured in a manner well known in the art in such a way that the compressive strength of the formed moldings against the surface of the molded article is greater than 10 50 N, preferably 100 to 400 N. This is important because low compressive strengths which would result in an undesirable metal powder entering the reaction product as an impurity. Furthermore, the catalyst moldings used according to the invention have a specific internal surface area of 10 to 90 m 2 / g. From the moldings made, such examination of the internal surface area and thus determination of the suitability of the moldings for use in the method according to the invention is carried out by the methods described below: F. M. Nelsen and F.

T. Eggertsen, Analyt, Chem. 30 (1958), 1387 and S. J. Gregg and S. W. Sing, Adsorption, Surface Area and Porosity, London 1967, paragraphs 2 and 8.

The hydrogenation is carried out at temperatures of 60 to 125 ° C, preferably 70 to 115 ° C. Lower temperatures would cause extended residence times or abandonment of the almost quantitative reaction of sugar. Higher temperatures lead to uncontrolled side reactions such as caramelization, ether cleavage, or hydrogenation-cracking, which can result in discoloration as well as the formation of unwanted by-products.

The catalyst load per hour is 25 to 100 g of starting sugars per liter of catalyst. By complying with said reaction requirements, surprisingly long catalyst durations of 13 101879 16,000 hours and more are achieved, with a specific catalyst consumption of at most 0.1% or less. Thus, the technical advantages of the process according to the invention are, in addition to the high yields obtained due to the almost quantitative reaction and the ecological advantages due to the purity of the product produced, a cost-saving continuous operation and extremely low catalyst consumption.

An aqueous solution of sugar alcohol which, after depressurization 10 to recover excess hydrogen and, after pressurization and replenishment with hydrogen, is returned to the reaction, can be used directly in liquid form as a sugar substitute after removal from the reactor.

However, the water in this solution can be removed by various methods, for example by spray drying, drying rollers or freeze drying. A process has been found to be advantageous in which the resulting colorless and glassy sugar alcohol solution is concentrated in a membrane evaporator or similar apparatus to a solution of about 70 to 80-20% by weight, which is then further evaporated in a vacuum crystallizer with cooling to give a partially or completely crystallized product. The crystalline product can be subsequently ground to a uniform granular product by grinding and possibly sieving. The product obtained is free-flowing 25.

Xylitol has a melting point of 93-94 ° C. Depending on the crystallization conditions, sorbitol can be prepared in various crystalline variants, the most stable of which is the y-form with a melting point of 101 ° C.

Depending on the crystallization conditions, lactitol is obtained either as a dihydrate having a melting point of 76 to 78 ° C or as a monohydrate having a melting point of 121 to 123 ° C. The solubility of both hydrates in water is different; the monohydrate is less soluble than the dihydrate. Hydrates are not hygroscopic and are thus technologically more advantageous than other polyols. Anhydrous lactitol can be precipitated as crystals from anhydrous ethanol. It has a melting point of 146 ° C and is hygroscopic.

Maltitol can be prepared as an anhydrous amorphous powder from anhydrous ethanol. It melts at 146-148 ° C and is hygroscopic (Helv. Chim. Acta 20 (1937), 86-90).

All sugar alcohols prepared according to the invention contain less than 1 ppm of catalyst components.

10 Example 1

A vertical high-pressure stainless steel high-pressure tube with an inner diameter of 45 mm and a height of 1 m was filled with 1.4 l of tableted hydrogenation catalyst as tablets with a height of 5 mm and a diameter of 5 mm with a compressive strength of 147 cylindrical surfaces. N and having an internal surface area of 33 m2 / g. 250 ml of a special 20 ml of pure hydrogen at a pressure of 30,000 kPa per hour in a 40% solution of D-xylose (pH 7.0) in deposited oxygen-free drinking water were continuously pumped through this tube from the bottom up.

The aqueous solution and the hydrogen were preheated together through a heat exchanger where they were heated so hot that their temperature when introduced into the high pressure pipe was 95 eC. The mixture of aqueous solution and excess hydrogen leaving the high pressure tube was passed through a condenser and separator, from which, after replacing the amount used, the hydrogen was again pumped together with fresh D-xylose solution 30 to a preheater and again to a high pressure tube.

After decompression, the colorless clear aqueous solution was concentrated in a membrane evaporator to a sugar alcohol content of about 70% and further crystallized by evaporation in a vacuum evaporator while cooling.

35 A white, slightly hygroscopic, odorless solid was obtained which was ground to a fine crystalline powder. The xylitol formed was very pure and its stable rhombic crystals melted at 93-94 ° C. The content of non-hydrogenated D-xyloose was <0.1%. The Ni content was <1 ppm. The Ka-5 talicator continued to operate just as efficiently after 5,600 hours of operation.

Example 2

Hydrogen was passed through the high pressure pipe described in Example 1 at 105 ° C under a hydrogen pressure of 10,000 kPa in the opposite direction to the rising D-cyclose solution in Example 1, hydrogenating an equal volume of a 40% aqueous solution of D-xylose at pH 1 per hour. was 6.5. The catalyst was prepared by tableting from nickel powder. The cylindrical tablets were 5 mm high and 5 mm in diameter. The tablets had a compressive strength of 149 N against the surface of the cylindrical shell and an internal surface area of 62 m 2 / g.

After 2,800 hours of use, their efficiency was unchanged and the D-xylose reaction was £ 99.9%.

The content of non-hydrogenated D-xylose in crystallized xylitol with a purity of> 99.5% was <0.1%. The Ni content was <1 ppm.

Example 3

In the high-pressure tube described in Example 1, hydrogenation was carried out at 115 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1 with an equal amount of 40% D-xylose solution (pH 7.5) per hour as in Example 1. The catalyst was prepared by tableting powdered nickel-iron alloy. The alloy contained 15% 30 iron in nickel. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, a compressive strength of 137 N against the surface of the cylindrical shell and an internal surface area of 83 m 2 / g. The purity of the crystalline xylitol obtained by adding seed crystals in the vacuum crystallizer was 35 £ 99.5%, was <0.1%. The Ni content was <1 ppm.

16 101879

Example 3

In the high-pressure tube described in Example 1, the same amount of 40% 5-D-xylose solution (pH 7.5) per hour as in Example 1 was spun at 115 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1. The catalyst was prepared by tableting powdered nickel iron alloy. The alloy contained 15% iron in nickel. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, the compressive strength of the tablets against the surface of the cylindrical shell was 137 N and their internal surface area was 83 m 2 / g. The purity of the crystalline xylitol obtained by adding seed crystals in the vacuum crystallizer was> 99.5%. The content of unreacted D-xylose was 0.1%.

The total Ni and Fe concentrations were <1 ppm. Catalyst-15 was still equally effective after 5,400 hours of operation.

Example 4

In the high-pressure tube described in Example 1, 150 ml of a 40% aqueous solution of D-xylose (pH 7.5) were hydrogenated at 110 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1. The catalyst was prepared by tableting cobalt powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, the compressive strength of the tablets against the surface of the cylindrical shell was 25,225 N and their internal surface area was 19 m 2 / g. The xylitol obtained in the vacuum circuit contained unreacted D-xylose <0.2%. The Co content was <1 ppm. The catalyst was still just as effective after 1,000 hours of operation.

Example 5 (Comparative Example) In the high-pressure tube described in Example 1, hydrogen was hydrogenated at 110 ° C under a pressure of 30,000 kPa in the same manner as in Example 1 for an equal amount of a 40% aqueous solution of D-xylose (pH 6.5). ). the catalyst was prepared by adding an aqueous solution of nickel salt to an inert support of Al 2 O 3 consisting of 5 mm diameter beads and converting nickel to metal by reduction in a stream of hydrogen. The nickel content of the catalyst was 20%. The internal surface area of the catalyst was 140 m2 / g. The purity of xylitol obtained in a vacuum crystallizer was 96.8%. The content of unreacted D-xylose was 1.5%. In addition, the product was found to contain other sugars as an impurity, so that the quyltol thus obtained could not be used in this formulation as a sugar substitute without ecologically harmful refining processes. By increasing the reaction temperature from 100 ° C to 125 ° C, it was possible to reduce the proportion of unreacted D-xylose to 1.2%, but at the same time the proportion of organic impurities increased to 3.2%, including lychexol and arabinitol combined. 1.4%. In addition, the reaction product-15 contained 36 ppm of nickel as an impurity.

Example 6 (comparative example)

In the high-pressure tube described in Example 1, hydrogen was hydrogenated at 115 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1 for 20 hours in the same amount as in Example 1 of a 40% aqueous solution of D-xylose (pH 6.5). . The catalyst was prepared by adding aqueous solutions of nickel and iron salts to an inert Al 2 O 3 support consisting of 5 mm diameter spheres and converting nickel and iron to metals by reduction in a stream of hydrogen. The catalyst had a nickel content of 16% and an iron content of 4%. The internal surface area of the catalyst was 155 m2 / g.

The purity of xylitol obtained by evaporation in a vacuum crystallizer was 94.6%. The content of unreacted D-xylose 30 was 1.4%. In addition, the product was found to contain • 4.0% other sugars, 32 ppm nickel and 11 ppm iron as impurities, so that the xylitol thus obtained could not be used as a sugar substitute without ecologically harmful refining processes. For as little as 750 hours of operation, a significant reduction in catalyst activity could be observed.

Example 7

The high pressure tube described in Example 1 was charged with a hydrogenation catalyst prepared by tableting 5 1.4 l of nickel powder with a cylindrical body height of 5 mm and a diameter of 5 mm, a compressive strength of the tablets against the surface of the cylindrical shell of 147 N and an internal surface area of 33 m2 / g. . Through this tube, 250 ml of an ultra-pure hydrogen per hour in a 40% α-D-glucose solution (pH 7.0) in deionized oxygen-free drinking water were continuously pumped from the bottom up together with three times the molar amount at 30,000 kPa.

The aqueous solution and hydrogen were preheated together through a heat exchanger where they were heated so hot that their temperature when introduced into the high pressure tube was 95 ° C. The mixture of aqueous solution leaving the high pressure tube and excess hydrogen was passed through a condenser to a separator, from which, after replacing the amount used, the hydrogen was pumped together with fresh α-D-glucose solution into a preheater and again into a high pressure tube.

After depressurization, the colorless clear aqueous solution was concentrated in a membrane evaporator to a sugar alcohol content of about 70% and further crystallized by evaporation in a vacuum evaporator while cooling. A white, slightly hygroscopic, odorless solid was obtained which was ground to a fine crystalline powder. The sorbitol (D-glucitol) formed was very pure and had a melting point of 101 ° C for its stable y-form. The content of non-hydrogenated α-D-glucose was <0.1%. The Ni content was <1 ppm. After 9,800 hours of operation, the catalyst continued to operate as efficiently.

Example 8

Hydrogen was passed through the high pressure pipe described in Example 1 at 105 ° C under a hydrogen pressure of 19 101879 at 15,000 kPa in the opposite reaction flow to the ascending α-D-glucose stream in Example 1, hydrogenating an equal amount of 40% α-D-glucose per hour. aqueous solution (pH 6.5) as in Example 1. Catalyst 5 was prepared by tableting from nickel powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm. The tablets had a compressive strength against the surface of the cylindrical shell of 149 N and an internal surface area of 62 m 2 / g.

After 4,200 hours of operation, the efficiency of the catalyst 10 was constant and the reaction rate of o-D-glucose was 99.9%. The content of non-hydrogenated α-β-D-glucose in crystallized sorbitol (-glucitol) with a purity of £ 99.5% was <0.1%. The Ni content was <1 ppm.

Example 9 In the high pressure tube described in Example 1, hydrogenation was carried out at 115 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1 with an equal amount of 40% aqueous α-D-glucog solution (pH 7.5) per hour as in Example 1. The catalyst was made of a tableted nickel-iron alloy containing 15% iron in nickel, with a cylindrical tablet height of 5 mm and a diameter of 5 mm, a compressive strength of 137 N against the surface of the cylindrical shell and an internal surface area of 83 m 2. The crystalline sorbitol (D-glucitol) obtained in the vacuum crystallizer 25 had a purity of> 99.5% and an unreacted α-D-glucose content of 0.1%.

The total Ni and Fe concentrations were <1 ppm. The catalyst was still just as efficient after 8,400 hours of operation.

30 Example 10 • In the high pressure pipe described in Example 1, the hydrate- *.

was carried out at 110 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1,150 ml of a 359% aqueous solution of α-D-glucose (pH 6.5). The catalyst was prepared by tableting from cobalt powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, a compressive strength of 225 N against the surface of the cylindrical shell and an internal surface area of 19 m 2 / g. The sorbitol (D-glucitol) obtained in the vacuum circuit contained unreacted 5 α-D-glucose ≤ 0.2%. The Co content was <1 ppm. The catalyst was still just as effective after 1,000 hours of operation.

Example 11 (comparative example)

In the high-pressure tube described in Example 1, hydrogenation was carried out at 110 ° C and 30,000 hydrogen pressure in the same manner as in Example 1 and for the same time an equal amount of 40% aqueous o-D-glucose solution (pH 6.5). The catalyst was prepared by adding an aqueous solution of a nickel salt to an inert Al 2 O 3 support consisting of 5 mm diameter beads and then converting the nickel to metal by reduction in a stream of hydrogen. The nickel content of the catalyst was 20%. The internal surface area of the catalyst was 140 m2 / g.

The purity of sorbium toluene (D-glucitol) obtained by evaporation in a vacuum crystallizer was 94.9%. The concentration of unreacted α-D-glucose was 1.9%. In addition, the product was found to contain 3.2% of other sugars as impurities, e.g. mannitol 2.1%, so that the sorbitol thus obtained could not be used in this formulation as a sugar substitute without environmentally harmful purification processes.

Although raising the reaction temperature from 110 ° C to 125 ° C, the proportion of unreacted α-D-glucose could be reduced to 0.6%, while the proportion of organic impurities increased to 6.2%, including 30% mannitol. In addition, the reaction product contained 42 ppm of nickel as an impurity.

Example 12 (comparative example)

In the high-pressure tube described in Example 1, an equal amount of 21 101879 40% aqueous α-D-glucose solution (pH 6.5) was hydrogenated at 115 ° C and 30,000 hydrogen pressure in the same manner as in Example 1 for 1 hour. The catalyst was prepared by adding aqueous solutions of nickel and iron salts to an inert Al 2 O 3 support consisting of 5 mm diameter beads 5 and converting the nickel and iron to metals by reduction in a stream of hydrogen. The catalyst had a nickel content of 16% and an iron content of 4%. The internal surface area of the catalyst was 155 m2 / g.

The purity of sorbitol (D-glucitol) obtained by evaporation in a vacuum crystallizer was 93.8%. The concentration of unreacted α-D-glucose was 1.6%. In addition, the product was found to contain 4.6% organic impurities, e.g. mannitol 2.9%, as well as Ni impurities 38 ppm and Fe impurities 16 ppm, so that the sorbitol thus obtained could not be used in this preparation as a sugar substitute without ecologically harmful purification processes. Already after an operating time of 800 hours, a significant decrease in the activity of the catalyst was found.

Example 13 A hydrogenation catalyst prepared by tableting 1.4 L of nickel powder with a cylindrical body height of 5 mm and a diameter of 5 mm, a compressive strength of the tablets against the surface of the cylindrical shell and an internal surface area of the tablets of 25 mm was introduced into the high-pressure tube described in Example 1. the area was 33 m2 / g. Through this tube, 250 ml per hour of a 40% solution of 4-O-D-galactopyranosyl-α-glucopyranose (pH) were continuously pumped from the bottom up together with three times the molar amount at a pressure of 30,000 kPa. 7.0) in deionized 30 oxygen-free drinking water.

The aqueous solution and hydrogen were preheated together through a heat exchanger where they were heated so hot that their temperature when introduced into the high pressure pipe was 90 eC. The mixture of the aqueous solution leaving the high pressure tube and the excess hydrogen was passed through a condenser to a separator, from which, after replacing the amount used, the hydrogen was pumped together with fresh 4-O-β-D-galactopyranosyl-α-D-glucopyranose to the preheater and then again under high pressure.

After depressurization, the colorless clear aqueous solution was concentrated in a membrane evaporator to a sugar alcohol content of about 80% and further crystallized by evaporation in a vacuum evaporator while cooling. Under the crystallization conditions and depending on the residual water-10 content of the evaporated solution, either a dihydrate having a melting point of 76 to 78 ° C or a monohydrate having a melting point of 121 to 123 ° C was then isolated. The 4-O-6- D-galactopyranosyl-D-glucitol formed was very pure (purity> 99.6%). The content of non-hydrogenated 4-O-S-D-galactopyranosyl-α-D-glucopyranose was <0.1%.

Concentrations of sorbitol or dulkitol were £ 0.1%. 4-0-8-D-galactopyranosyl-D-mannitol and mannitol could not be detected in the product. The Ni content was <1 ppm. After 8,700 hours of operation, the catalyst continued to operate at 20 equal efficiencies.

Example 14

Hydrogen was passed through the high pressure tube described in Example 1 at 105 ° C under a hydrogen pressure of 15,000 kPa as an opposite reaction stream to the rising stream of 4-O-BD-galactopyranosyl-αD-glucopyranose solution in Example 1, hydrogenating an equal amount of 4-O-BD per hour. a 40% aqueous solution of galactopyranose-α-glucopyranose (pH 6.5) as in Example 1. The catalyst was prepared by tableting from nickel powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm. The tablets had a compressive strength of 149 N against the surface of the cylindrical shell and an internal surface area of 62 m 2 / g.

After 2,500 hours of operation, the efficiency of the catalyst 35 was unchanged. The concentration of 4-O-β-D-galactopyranosyl-23 101879 li-D-glucitol in the rotary evaporator in the dry evaporated reaction mixture was 99.4%. The content of non-hydrogenated 4-O-6-D-galactopyranosyl-α-D-glucopyranose was £ 0.1%. The concentration of sorbitol and dulsitol was 0.1%.

5 4-O-6--Galactopyranosyl-D-mannitol or mannitol could not be detected in the product. The Ni content was <1 ppm.

Example 15

In the high-pressure tube described in Example 1, a quantity of 40% aqueous solution of 4-O-3-D-galactopyranosyl-αD-glucopyranosyl was hydrogenated at 115 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1 for 1 hour. (pH 7.5). The catalyst was prepared by tableting a powdered nickel-iron alloy. The alloy contained 15 to 15% iron in nickel. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, the compressive strength of the tablets against the surface of the cylindrical shell was 137 N and their internal surface area was 83 m 2 / g. The purity of 4-O-3-D-galactopyranosyl-α-d-glucitol obtained in a vacuum crystallizer was 99.3%. It contained 0.1% of unreacted 4-O-3-D-galactopyranosyl-α-D-glucose. The sorbitol and dulsitol content was 0.1%. 4-O-6- D-galactopyranosyl-D-mannitol or mannitol could not be detected. Ni and Fe concentrations were <1 ppm. After 8,000 hours of operation, the catalyst was still equally effective.

Example 16

In the high-pressure tube described in Example 1, an amount equal to 30% of the 30% aqueous solution of 4-O-6--D-galactopyranosyl-α-D-glucopyranose was hydrogenated at 100 ° C under a hydrogen pressure of 20,000 kPa in the same manner as in Example 1. (pH 6.5). The catalyst was prepared by tableting a powdered nickel-cobalt alloy. The alloy contained 10% cobalt in nickel. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, a compressive strength of the tablets against the surface of the cylindrical shell 24 101879 was 147 N and an internal surface area of 29 m 2 / g. The purity of 4-O-β-D-galactopyranosyl-α-D-glucitol obtained in a vacuum circulator was 99.1%. It contained 0.2% of unreacted 4-O-β-D-galactopyranosyl-α-D-glucopyrano-5. The sorbitol content was 0.2%. The dustitol content was 0.15%. 4-O-8-D-galactopyranosyl-D-mannitol could not be detected. Ni and Co concentrations were <1 ppm. The catalyst was still just as effective after 1,000 hours of operation.

10 Example 17 (comparative example)

In the high-pressure tube described in Example 1, an equal amount of 40% aqueous solution of 4-O-6-D-galactopyranosyl-αD-glucopyran-15ose was hydrogenated at 100 ° C and 30,000 hydrogen pressure in the same manner as in Example 1 for the same time. pH 7.0). The catalyst was prepared by adding an aqueous solution of the nickel salt to an inert Al 2 O 3 support consisting of 5 mm diameter beads and then converting the nickel to metal by reduction in a stream of hydrogen. The nickel content of the catalyst was 20 to 20%. The internal surface area of the catalyst was 145 m2 / g.

The purity of 4-O-β-D-galactopyranosyl-α-D-glucitol obtained by evaporation in a vacuum crystallizer was 93.9%. The content of unreacted 4-O-β-D-galactopyranosyl-α-D-glucopyranose was 1.9%. Sorbitol and dulcitol concentrations were 0.4 and 0.2%, respectively. In addition, the product was found to contain 3.6% of other impurities, of which 2.6% of 4-O-β-D-galactopyranosyl-D-mannitol, so that the 4-O-8-D-galactopyranosyl-αD-glucitol thus obtained could not be obtained in this formulation. uses il-30 man ecologically harmful refining processes as a substitute for sugar. In addition. already after an operating time of 800 hours, a significant decrease in the activity of the catalyst was found. However, by raising the reaction temperature from 100 ° C to 120 ° C, the proportion of unreacted 4-O-BD-glucopyranosyl-αD-glucopyranose 35 could be reduced to 0.6%, while the proportion of impurities 25 101879 increased to 6.4%. . They contained 3.2% 4-O-β-D-glucopyranosyl-D-mannitol. In addition, the reaction product contained 42 ppm of nickel as an impurity.

Example 18 (Comparative Example) 5 In a high pressure tube described in Example 1, an equal amount of 40% aqueous solution of 4-O-8-D-galactopyranosyl-αD-glucopyranose was hydrogenated at 100 ° C and 30,000 hydrogen pressure in the same manner as in Example 1 for one hour. (pH 6.5). The catalyst was prepared by adding aqueous solutions of nickel and iron salts to an inert Al 2 O 3 support consisting of 5 mm diameter beads and converting the nickel and iron to metals by reduction in a stream of hydrogen. The catalyst had a Nikke lipid content of 16% and an iron content of 4%. The internal surface area of the catalyst 15 was 151 m2 / g.

The purity of 4-O-β-D-galactopyranosyl-α-D-glucitol obtained by evaporation in a vacuum crystallizer was 91.2%. The content of unreacted 4-O-β-D-galactopyranosyl-α-D-glucopyranose was 1.6%. Sorbitol and dulcitol concentrations were 0.3 and 0.1%, respectively. In addition, the product was found to contain 6.8% of other organic impurities, of which 2.9% of 4-O-BD-galactopyranosyl-D-mannitol, and 36 ppm of nickel and 14 ppm of iron as impurities, so that the 4-O-BD-galatopyranosyl αD-glucitol in this formulation could not be used as a sugar substitute without ecologically harmful purification processes.

Example 19

The high pressure tube described in Example 1 was charged with a hydrogenation catalyst prepared by tableting 1.4 L of nickel powder with a cylindrical body height of 5 mm and a diameter of 5 mm, a compressive strength of 174 N against the surface of the cylindrical shell, and an internal surface area of 33 mm. m2 / g. This tube was continuously pumped from the bottom up with a five-fold amount of moo-35 at a pressure of 30,000 kPa from ultrapure 26 101879 hydrogen in 250 ml per hour of a 40% solution of 4-O-8-D-glucopyranosyl-α-D-glucopyranose (pH value 7.0) in delonold-free acid-free drinking water.

The aqueous solution and the hydrogen were previously passed together through a heat exchanger, where they were heated so hot that their temperature when introduced into the high-pressure pipe was 80 ° C. The mixture of the aqueous solution leaving the high pressure tube and the excess hydrogen was passed through a condenser to a separator from which, after replacing the amount used, the hydrogen was pumped together with fresh 4-O-α-D-glucopyranosyl-α-D-Glu copyranose to a preheater and then to a high pressure tube.

After depressurization, the colorless clear aqueous solution was concentrated in a membrane evaporator to a sugar alcohol-15 content of about 80% and further crystallized by evaporation on a vacuum evaporator while cooling and possibly adding seed crystals. The purity of crystalline 4-O-α-D-glucopyranosyl-D-sorbitol was> 99.6%. The p-20 content of non-hydrogenated 4-O-α-D-glucopyranosyl-α-D-glucopyranose was £ 0.1%. The sorbitol content was <0.3% and no mannitol was detected in the product. The Ni content was <1 ppm. After 6,200 hours of operation, the catalyst continued to operate as efficiently.

Example 20 ·· 25 Hydrogen was passed through the high pressure pipe described in Example 1 at 85 ° C under a hydrogen pressure of 15,000 kPa in the opposite reaction flow to the ascending 4-0-αD-glucopyranosyl-αD-glucopyranose aqueous solution, which was hydrogenated for one hour. amount of 4-O-αD-glucopyranosyl-αD-glucopyranose · 40% aqueous solution (pH 6.5) as in Example 1.

The catalyst was prepared by tableting from nickel powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm. The tablets had a compressive strength of 149 N against the surface of the cylindrical shell and an internal surface area of 62 m 2 / g.

After 2,500 hours of operation with unchanged catalyst efficiency, the concentration of 4-O-α-D-glucopyranosyl-5D-sorbitol in the rotary evaporator in the dry evaporated reaction mixture was 99.4%. Content of non-hydrogenated 4-O-α-D-glucopyranosyl-α-D-glucopyranose £ 0.1%. The sorbitol content was 0.3%. The Ni content was <1 ppm.

10 Example 21

In the high-pressure tube described in Example 1, an amount equal to 40% of an aqueous solution of 4-O-αD-glucopyranosyl-αD-Glu-15 copyranose (pH 1) was hydrogenated at 80 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1. value 7.5). The catalyst was prepared by tableting a powdered nickel-iron alloy ring. The alloy contained 15% iron in nickel. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, the compressive strength of the tablets against the surface of the cylindrical shell was 20,137 N and their internal surface area was 83 m 2 / g. The purity of 4-O-α-D-glucopyranosyl-α-D-sorbitol obtained in a vacuum evaporator was 99.3%. It contained 0.1% unreacted 4-O-α-D-glucopyranosyl-α-D-glucose. The sorbitol lip content was 0.3%. Ni and Fe concentrations were <1 ppm.

·; 25 After 4,200 hours of operation, the catalyst was still equally effective.

Example 22

In the high-pressure tube described in Example 1, hydrogenation was carried out at 100 ° C under a hydrogen pressure of 20,000 kPa in the same manner as in Example 1 for an amount equal to 30% of a 30% aqueous solution of 4-O-αD-glucopyranosyl-αD-glucopyranose ( pH 6.5). The catalyst was prepared by tableting from cobalt powder. The cylindrical tablets had a height of 5 mm and a diameter of 5 mm, the compressive strength of the 35 tablets against the surface of the cylindrical shell was 28,101879,225 N and their internal surface area was 19 m 2 / g. The purity of 4-O-α-D-glucopyranosyl-α-D-sorbitol obtained in a vacuum circulator was 99.1%. It contained 0.1% unreacted 4-O-α-D-glucopyranosyl-α-D-glucose. The sorbitol-5 content was 0.2%. The Co content was <1 ppm. The catalyst was still just as effective after 1,000 hours of operation.

Example 23 (comparative example)

In the high-pressure tube described in Example 1, hydrogen was hydrated at 100 ° C under a hydrogen pressure of 30,000 kPa in the same manner as in Example 1 for the same time as in Example 1 in an amount equal to 40% of 4-O-α-D-glucopyranosyl-αD- aqueous glucopyranose solution (pH 7.0). The catalyst was prepared by adding an aqueous solution of nickel-15 salt salt to an inert Al 2 O 3 support consisting of 5 mm diameter beads and then converting the nickel to metal by reduction in a stream of hydrogen. The nickel content of the catalyst was 20%. The internal surface area of the catalyst was 148 m2 / g.

The purity of 4-O-α-D-glucopyranosyl-α-D-sorbitol obtained by evaporation in a vacuum evaporator was 92.9%. The content of unreacted 4-O-α-D-glucopyranosyl-α-D-glucopyranose was 1.4%. The sorbitol content was 3.6%. In addition, the product was found to contain unknown impurities of 2.1%, so that the 4-O-α-D-glucopyranosyl-α-D-sorbitol thus obtained in this formulation could not be used as a sugar substitute without ecologically harmful purification processes. In addition, even after 700 hours of use, the activity of the catalyst was found to be significantly reduced. By increasing the reaction temperature · From 100 ° C to 102 ° C, the proportion of unreacted 4-O-α-D-glucopyranosyl-α-D-glucopyranose could be reduced to 0.2%, while the proportion of sorbitol increased to 4.2%. In addition, the reaction product contained 35 to 48 ppm of nickel as an impurity.

29 101879

Example 24 (comparative example)

In the high-pressure tube described in Example 1, at 40 ° C and 30,000 hydrogen pressure, an equal amount of 40% aqueous 4-OaD-glucopyranosyl-αD-Glu-copyranose solution (pH 1) was hydrogenated in the same manner as in Example 1 per hour. 6.5). The catalyst was prepared by adding aqueous solutions of nickel and iron salts to an inert Al 2 O 2 support consisting of 5 mm diameter beads and then converting the nickel and iron to metals by reduction in a stream of hydrogen. The catalyst had a nickel content of 16% and an iron content of 4%. The internal surface area of the catalyst was 151 m2 / g.

The purity of 4-O-α-D-glucopyranosyl-α-D-sorbitol obtained by evaporation on a rotary evaporator was 93.4%.

The content of unreacted 4-O-α-D-glucopyranosyl-α-D-glucopyranose was 1.0%. The sorbitol content was 4.3%. In addition, the product was found to contain 1.3% of unknown organic impurities and 31 ppm of nickel and 12 ppm of iron, so that the sugar alcohol 20 thus obtained could not be used as a sugar substitute without ecologically harmful refining processes.

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Claims (4)

101879 A process for the preparation of epimer-free sugar alcohols belonging to the group of xylitol, sorbitol (D-glucitol), 4-O-ED-galactopyranosyl-D-glucitol and 4-OaD-gluco-5 pyranosyl-D-sorbitol by catalytic hydrogenation of the corresponding sugars, D-xylose, αD-glucose, 4-O-SD-galactopyranosyl-αD-glucopyranose or 4-O-αD-glucopyranosyl-αD-glucopyranose in aqueous solution at elevated pressure and elevated temperature, characterized in that the hydrogenation is carried out continuously with hydrogen at a pressure of 10,000 to 50,000 kPa and a temperature of 60 to 125 ° C by a fixed bed process in a single reaction zone over hydrogen-free catalyst-free shaped bodies having a compressive stiffness of more than 50 N, preferably 100 to 400 N, and an internal surface area of an area of 10 to 90 m2 / g and consisting of one or more elements belonging to the iron group of the Periodic Table. Method according to Claim 1, characterized in that the shaped bodies in question are shaped bodies made of a powdered metal, namely nickel, cobalt or their alloys or alloys with one another or with iron, which have a smooth surface when viewed macroscopically. Process according to Claim 1, characterized in that the hydrogenation catalysts are cylindrical or spherical shaped bodies with a diameter of 3 to 7 mm. Process according to Claim 1, characterized in that the hydrogenation of the sugars is carried out in a 14 to 45% aqueous solution having a pH of 3.5 to 10.5. 101879