CATALYTIC HYDROGENATION OF SACCHARIDES using RUTHENIUM catalysts on silica carrier

ES 2 312 596 T3

DESCRIPTION

Catalytic hydrogenated saccharides in ruthenium catalysts on a SiO support₂.

The present invention refers to new ruthenium catalysts, a process for their preparation, and their use for the catalytic hydrogenation of mono- and oligosaccharides in the production of sugar alcohols, except sorbitol.

The production of sugar alcohols on an industrial scale is generally carried out by catalytic hydrogenation of corresponding mono- and disaccharides (see H. Schiweck et al. "Sugar Alcohols" in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. On CD-ROM). To date, nickel catalysts, for example supported nickel catalysts or Raney catalysts, have hitherto been used primarily as catalysts. The use of catalysts containing ruthenium for this purpose was also reported on different occasions. As a general rule, the ruthenium catalysts are so-called supported catalysts, which contain ruthenium on an oxidic or organic support, such as carbon.

Thus, US 4,380,680, US 4,487,980, US 4,413,152 and US 4,471,144 describe catalysts for the hydrogenation of carbohydrates to give the corresponding ruthenium-containing sugar alcohols on a stable support material under hydrothermal conditions. As hydrothermal support materials, alpha-aluminum oxide (US 4,380,680), titanium (IV) oxide (US 4,487,980), aluminum oxide treated with titanium (IV) halide (US 4,413,152) and theta-aluminum oxide (US 4,471,144).

From US 4,503,274 catalysts are known for the hydrogenation of carbohydrates to give the corresponding sugar alcohols, which are obtained by impregnating a stable support under hydrothermal conditions with an aqueous solution of ruthenium halide, and their subsequent hydrogenation of the solid product to temperatures in the range of 100 to 300 ° C.

US 3,963,788 describes ruthenium catalysts for the hydrogenation of carbohydrates, in which the ruthenium was supported with a special zeolite based on an alumosilicate. US 3,963,789 proposes crystalline aluminosilicate clays, especially montmorillonite, as support for ruthenium catalysts.

FR-A 2526782 describes the use of a ruthenium chloride obtained by reacting sodium chloride and ruthenium via Na₂RuCl₆ to obtain ruthenium catalysts supported on silicon dioxide for the hydrogenation of mono- and oligosaccharides.

EP 992475 describes a process for obtaining alcohols by catalytic hydrogenation of aldehydes or ketones using ruthenium catalysts attached to a support. Example B5 describes the preparation of sorbitol by hydrogenating glucose on a catalyst containing 2% ruthenium on titanium dioxide.

EP 949233 describes a process for obtaining sugar alcohols by hydrogenating sugars, in which sugars are brought into contact with hydrogen in the presence of a catalyst, the catalyst comprising at least one metal from secondary group VIII of the Periodic System.

The parallel application WO 02/100539 refers to a process for obtaining sorbitol by catalytic hydrogenation of a monosaccharide, which forms sorbitol in the hydrogenation, in the liquid phase, which is characterized in that the catalyst used is selected from ruthenium catalysts, which are obtainable through: i) single or multiple treatment of a support material based on amorphous silicon dioxide with a halogen-free aqueous solution of a low molecular weight ruthenium compound, and subsequent drying of the treated support material at a temperature below 200 ° C, ii) reduction of the solid product obtained in i) with hydrogen at a temperature in the range of 100 to 350 ° C, step ii) being carried out immediately after step i).

The parallel application WO 02/100536 refers to a process for the hydrogenation of aromatic compounds with one or more nuclei using such catalysts.

The parallel application WO 02/100538 refers to the use of such catalysts for the production of cycloaliphatic compounds, which have side chains with epoxide groups, by catalytic hydrogenation of corresponding aromatic compounds.

The ruthenium catalysts known from the state of the art show only moderate reactivities in the hydrogenation of carbohydrates, with the consequence that the space-time yields achieved in sugar alcohols, based on the catalyst used, are low. Therefore, in view of the high costs for ruthenium, the profitability of these processes leaves something to be desired. Furthermore, the selectivities of catalysts are not sufficient, so that additional expense is necessary in the isolation of valuable products. In particular, an epimerization of hydroxy groups is frequently observed.

Therefore, the present invention is based on the task of making available a process for obtaining sugar alcohols by catalytic hydrogenation of the corresponding carbohydrates, presenting

ES 2 312 596 T3 catalysts have high reactivities. Furthermore, the catalysts will exhibit high product selectivity, not least with regard to continuous hydrogenation conditioning.

Surprisingly, this problem was solved by using ruthenium catalysts containing ruthenium on a support material based on amorphous silicon dioxide in an amount of 0.2 to 7% by weight, based on the support material, the support material being constituted by silicon dioxide at least 90% by weight, based on the support material, and presenting less than 10% by weight of crystalline silicon dioxide phases, and the catalyst being obtainable by:

i) single or multiple treatment of the support material with an aqueous solution of a ruthenium compound selected from ruthenium (III) nitrosylnitrate, ruthenium (III) acetate, and potassium (IV) ruthenate, containing the aqueous solution, based on its weight total less than 500 ppm, and its subsequent drying of the treated support material at a temperature below 200 ° C, preferably <180 ° C, and especially <150 ° C, ii) reduction of the solid product obtained in i) with hydrogen at a temperature in the range of 100 to 350 ° C, preferably 150 to 350 ° C and especially 200 to 320 ° C, step ii) being carried out immediately thereafter from step i).

Consequently, the invention relates to the use of such catalysts in obtaining sugar alcohols by catalytic hydrogenation of the corresponding mono- and oligosaccharides, with the exception of the use for obtaining sorbitol. The use for obtaining sorbitol (= sorbitol) is the subject of parallel German patent application 101282036.6 and its subsequent application WO 02/100539.

The catalysts used according to the invention are distinguished by increased activity and high product selectivity in the hydrogenation of mono- and oligosaccharides.

It is suspected that the high reactivity of the catalysts used according to the invention can be attributed to the particularly good distribution of ruthenium on the surface of the support material, and to the noticeable absence of halogen in the support material. Due to the preparation, ruthenium occurs as metallic ruthenium in the catalysts according to the invention. Electron microscopic investigations (TEM) of the catalysts according to the invention have shown that ruthenium occurs on the support material in the form of atomic dispersion and / or in the form of ruthenium particles, which occur almost exclusively, that is, in more 90%, preferably more than 95%, based on the number of visible particles, as isolated particles with diameters below 10 nm, in particular below 7 nm. In other words, the catalyst contains essentially no, that is, it contains less than 10%, especially less than 5% of ruthenium particles and / or agglomerates of ruthenium particles with diameters above 10 nm. By using halogen-free and solvent-free ruthenium precursors in the preparation, the chlorine content of the catalysts according to the invention is also below 0.05% by weight (<500 ppm), based on the total weight of catalyst. In this case and below, all ppm data should be understood as weight fractions, unless otherwise indicated.

An essential aspect of the catalysts according to the invention is the use of a support material based on amorphous silicon dioxide. In this context, the term "amorphous" is understood to mean that the fraction of crystalline silicon dioxide phases constitutes less than 10% of the support material. The support materials used to prepare the catalysts according to the invention can, however, have superstructures which are formed by the regular arrangement of pores in the support material.

As support materials, in principle all amorphous types of silicon dioxide come into consideration, which consist of at least 90% by weight of silicon dioxide, the remaining 10% by weight being able to be, preferably not more than one 5% by weight of the support material, also another oxidic material, for example MgO, CaO, TiO₂, ZrO₂, Faith₂OR₃ or alkali metal oxide. It goes without saying that the support material used is also halogen-free, that is, the halogen content is less than 500 ppm, based on the total weight of the support material. The support material preferably does not contain more than 1% by weight, and especially not more than 0.5% by weight, and in particular does not contain identifiable amounts (<500 ppm) of aluminum oxide, calculated as Al2O3. In a preferred embodiment, support materials containing less than 500 ppm of Fe are used.₂OR₃. The metal oxide fraction generally results from obtaining support material and can amount to up to 2% by weight. This is frequently less than 1% by weight. Also suitable are supports free of alkali metal oxide (<0.1% by weight). The fraction of MgO, CaO, TiO₂, or ZrO₂ it may constitute 10% by weight of the support material, and preferably does not amount to more than 5% by weight. However, support materials that do not contain identifiable amounts of these metal oxides (<0.1% by weight) are also suitable.

Support materials having a specific surface area in the range of 50 to 700 μm are preferred.²/ g, especially in the 80 to 600 m range²/ g, and especially in the range of 100 to 600 m²/ g (BET surfaces according to DIN 66131). Among the powdery carrier materials, those whose specific surface area (BET) is in the range of 200 to 600 μm are particularly preferred.²/ g. In the case of carrier material in the form of shaped bodies, the specific surface area is in particular in the range of 100 to 300 m²/ g.

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Appropriate silicon dioxide-based amorphous support materials are common to the skilled man, and commercially available (see, for example, OW Florke, "Silica" in Ullmann's Encyclopedia of Industrial Chemistry 5th ed. On CD-ROM). These can be of natural origin, or have been obtained by synthetic means. Examples of suitable amorphous support materials based on silicon dioxide are Kieselguhr, silica gels, fumed silicic acid and precipitated silicic acid. In a preferred embodiment of the invention, the catalysts have silica gels as support materials.

Depending on the conditions of the hydrogenation processes in which the catalysts according to the invention are used, the support material can have different configuration. As long as the process is configured as a suspension process, the support material is usually used in the form of a finely divided powder to obtain the catalysts according to the invention. The powder preferably has particle sizes in the range from 1 to 200 pm, especially 1 to 100 pm. When the catalyst is used in fixed catalyst beds, it is customary to use shaped bodies consisting of the carrier material, which are obtainable, for example, by extrusion, extrusion pressing or tableting, and can be, for example, in the form of balls. , tablets, cylinders, bars, rings, or hollow cylinders, stars and the like. The dimensions of these molded bodies are usually in the range of 1mm to 25mm. Catalyst bars with bar diameters of 2 to 5 mm and bar lengths of 2 to 25 mm are frequently used.

The ruthenium content in the catalysts used according to the invention is, based on the weight of the support material, and calculated as elemental ruthenium, in the range of 0.2 to 7% by weight, and in particular in the range of 1 0.4 to 5% by weight.

To obtain the ruthenium catalysts used according to the invention, the support material is first treated with a halogen-free aqueous solution of a low molecular weight ruthenium compound, then called a (ruthenium) precursor, so that the desired amount of ruthenium is absorbed by the support material. This step is also called impregnation in the following. Subsequently, the support treated in this way is dried in compliance with the upper temperature limits indicated above. If appropriate, the solid product thus obtained is treated again with the aqueous ruthenium precursor solution and dried again. This process is repeated frequently until the amount of ruthenium compound absorbed by the support material corresponds to the desired ruthenium content in the catalyst.

The treatment or impregnation of the support material can be carried out in different ways, and is adjusted in a known way to the conditioning of the support material. By way of example, the support material can be sprayed or washed with the precursor solution, or the support material can be suspended in the precursor solution. By way of example, the support material can be suspended in the aqueous solution of the ruthenium precursor, and the aqueous excess can be filtered off after a certain time. The amount of liquid absorbed and the ruthenium concentration of the solution can easily control the ruthenium content of the catalyst. The impregnation of the support material can also be carried out, for example, by treating the support with a defined amount of aqueous ruthenium precursor solution corresponding to the maximum amount of liquid that the support material can absorb. For this purpose, for example, the carrier material can be sprayed with the desired amount of liquid. Suitable installations for this purpose are the devices commonly used for mixing liquids with solid products (see Vauck / Müller, Grundoperationen chemischer Verfahrenstechnik, 10^to edition, Deutscher Verlag für Grundstoffindustrie, 1994, pages 405 and following), by way of example oscillating dryers, impregnating drums, drum mixers, paddle mixers and the like.

Monolithic supports are usually washed with the aqueous ruthenium precursor solutions.

The aqueous solutions used for impregnation are halogen-free according to the invention, that is to say they do not contain or contain less than 500 ppm, preferably less than 100 ppm of halogen, based on the total weight of the solution. Therefore, as ruthenium precursors, only those ruthenium compounds are used which do not contain halogen bound by chemical bonding, and which are sufficiently soluble in the aqueous solvent, and are selected from ruthenium (III) nitrosylnitrate (Ru (NO) ( DO NOT₃)₃), ruthenium (III) acetate, as well as alkali metal (IV) ruthenates, such as sodium and potassium (IV) ruthenate.

In this case, the term "aqueous" designates water, as well as water mixtures with up to 50% by volume, preferably not more than 30% by volume, and especially not more than 10% by volume of one or more water-miscible organic solvents, for example mixtures of water with C 1 -C 4 alkanols, such as methanol, ethanol, n- or iso-propanol. Water is often used as the sole solvent. The aqueous solvent will frequently additionally contain at least one halogen-free acid, for example nitric acid, sulfuric acid, phosphoric acid or acetic acid, preferably a halogen-free mineral acid, for stabilizing the ruthenium precursor in solution. Therefore, in many cases a halogen-free mineral acid diluted with water, for example dilute to semi-concentrated nitric acid, is used as the solvent for the ruthenium precursor. The concentration of the ruthenium precursor in aqueous solutions naturally adjusts to the amount of ruthenium precursor to be applied and the absorption capacity of the support material for the aqueous solution, and is generally in the range of 0.1 to 20 % in weigh.

Drying can be carried out according to the usual solid product drying procedures while complying with the upper temperature limits mentioned above. Compliance with the upper limit of temperatures

ES 2 312 596 T3 of drying according to the invention is important for the quality, that is to say, the catalyst activity. An excess of the drying temperatures indicated above leads to a clear loss of activity. Calcinate the support at higher temperatures, for example above 300 ° C or even 400 ° C, as proposed in the state of the art, is not only superfluous, but also has a negative influence on the activity of the catalyst. To achieve sufficient drying rates, drying is generally carried out at elevated temperatures, for example at least 40 ° C, and in particular at least 70 ° C, and especially> 100 ° C.

Drying of the solid product impregnated with the ruthenium precursor is usually carried out under normal pressure, and a reduced pressure can also be applied to promote drying. Frequently, to promote drying, a gaseous stream will be passed over or through the product to be dried, for example air or nitrogen.

Naturally, the drying time depends on the desired degree of drying and the drying temperature, and is generally in the range of 2 hours to 30 hours, preferably in the range of 4 hours to 15 hours.

Preferably, drying of the treated support material is carried out until the content of water, or of volatile solvent components before reduction ii) constitutes less than 5% by weight, especially less than 2% by weight, and particularly preferably not more than 1% by weight, based on the total weight of solid product. The weight fractions indicated refer in this case to the loss of weight of the solid product, determined at a temperature of 300 ° C, a pressure of 1 bar and a time of 10 minutes. In this way, the activity of the catalysts used according to the invention can be further increased.

Drying is preferably carried out under movement of the solid product treated with the precursor solution, for example by drying the solid product in a rotary tube furnace or a rotary ball furnace. In this way, the activity of the catalysts used according to the invention can be further increased.

The transformation of the solid product obtained after drying into its form with catalytic activity is carried out according to the invention by hydrogenating the solid product at the temperatures indicated above in a manner known per se (step ii)).

To this end, the support material is contacted with hydrogen or a mixture of hydrogen and an inert gas at the temperatures indicated above. The hydrogen partial pressure is of minor significance to the reduction result and is generally varied in the range from 0.2 bar to 1.5 bar. The hydrogenation of the catalyst material is frequently carried out under normal hydrogen pressure in a stream of hydrogen. The hydrogenation is preferably carried out under movement of the solid product obtained in i), for example by hydrogenating the solid product in a rotary tube furnace or a rotary ball furnace. In this way, the activity of the catalysts used according to the invention can be further increased.

Following hydrogenation, the catalyst can be passivated to improve handling attitude in a known manner, for example by treating the catalyst briefly with an oxygen-containing gas, for example air, but preferably with an inert gas mixture containing a 1 to 10% by weight of oxygen.

In particular, the catalysts used according to the invention are suitable for hydrogenating the carbonyl function of mono- and oligosaccharides. They differ from these substrates by on the one hand very high activities, so that high space-time yields are achieved, based on the catalyst used, in particular the ruthenium used. Furthermore, the corresponding sugar alcohols are obtained in high yields. Furthermore, the product selectivity is high, that is, the presence of secondary reaction, such as epimerized, decarbonylated, oligomerized and the like, leading to yield losses, is lower than in the ruthenium catalysts of the state of the art. Due to the high product selectivity, the expense for isolating the desired hydrogenation product is further reduced. Furthermore, a continuous operation of the reaction is thus simplified. Furthermore, the catalysts used according to the invention are distinguished by long periods of application, even under the aggressive conditions of hydrogenation in an aqueous reaction medium. A loss of activity of the catalysts according to the invention is not observed, or not to a significant extent, even after a longer period of use in the hydrogenation process according to the invention, for example after 1100 hours.

Naturally, the catalysts used in this process can be regenerated in the case of decreasing activity according to the usual methods for noble metal catalysts, such as ruthenium catalysts, known to the specialist. In this case, mention should be made, for example, of the treatment of the catalyst with oxygen, as described in BE 882279, the treatment with dilute halogen-free mineral acids, as described in US 4,072,628, or the treatment with hydrogen peroxide. , for example in the form of aqueous solutions with a content of 0.1 to 35% by weight, or treatment with other oxidizing substances, preferably in the form of halogen-free solutions. Typically, the catalyst is washed with a solvent, for example water, after re-reactivation, and before reuse.

Therefore, the invention also relates to a process for obtaining sugar alcohols by catalytic hydrogenation of the corresponding mono- and oligosaccharides, especially mono- and disaccharides, in the liquid phase in a heterogeneous ruthenium catalyst, which is characterized because the heterogeneous ruthenium catalyst

ES 2 312 596 T3 is selected from a ruthenium catalyst according to the invention, with the exception of a process for obtaining sorbitol (= sorbitol), which is the subject of parallel German patent application 10128203.6.

Appropriate saccharides comprise in principle all known tetroses, pentoses, hexoses and heptoses, and certainly both aldoses, as well as ketoses, as well as their di- and oligosaccharides, with the exception of glucose, fructose, gulose and sucrose, since they provide sorbitol in the hydrogenate. . Among the monosaccharides that can be used in the process according to the invention are, for example, erythrose, treose, ribose, arabinose, xylose, lixose, allose, atrose, mannose, gulose, idosa, galactose, talose, erythrulose, ribulose, xylulose, psychosis and tagatose, and certainly both the D form, as well as the L form. Examples of disaccharides are: maltose, isomaltose, lactose, cellobiose and melobiose. The mono- and oligosaccharides can be used as such or as mixtures, the starting materials being preferably used in pure form.

As suitable mono- and oligosaccharides for the hydrogenation process according to the invention, mention should be made in particular of the monosaccharides mannose for the preparation of mannitol, galactose for the preparation of dulcite (galactite) and xylose for the preparation of xylite, preferably the D form of monosaccharides, as well as the disaccharides maltose to obtain maltite, isomaltulose (palatinose) to obtain isomaltite, and lactose to obtain lactite. However, the other mono- and oligosaccharides mentioned can also be hydrogenated in the presence of the ruthenium catalysts according to the invention to give the corresponding sugar alcohols. In this case, the hydrogenation of aldoses leads to sugar alcohols, which have the same configuration as the sugar used with respect to the OH groups, and the hydrogenation of furanoses generally leads to mixtures of two diastereomeric sugar alcohols, which differ only in the configuration of the carbon atom, which carries the carbonyl function in furanose. The isolation of the respective pure sugar alcohol from this mixture is generally possible without problems.

The hydrogenation is preferably carried out by hydrogenating a solution of the respective mono- or oligosaccharide in an aqueous solvent. The term "aqueous" is to be understood in this case as defined above.

Conveniently, water is used as the sole solvent, containing possibly small amounts of an acid, preferably halogen-free, for adjusting the pH value, in particular the mono- or oligosaccharide is used as the aqueous solution which It has a pH value in the range of 4 to 10, and especially in the range of 5 to 7.

The concentration of starting materials in the aqueous phase can be freely selected in principle and is often in the range from 10 to 80% by weight, and preferably in the range from 15 to 50% by weight, based on the total weight of the solution.

The true hydrogenation using catalysts is usually carried out in analogy to the known hydrogenation processes for obtaining sugar alcohols, as described in the initially cited state of the art. For this purpose, the liquid phase containing the starting material is brought into contact with the catalyst in the presence of hydrogen. In this case, the catalyst can be suspended either in the liquid phase to be hydrogenated (suspension regime), or the liquid phase is conducted through a fluidized bed of catalyst (fluidized bed regime) or a fixed bed of catalyst (regime in suspension). fixed bed). In this case, the hydrogenation can be configured both continuously and discontinuously, the process according to the invention is preferably carried out in fluidized-bed reactors according to the fixed-bed regime. In this case, the hydrogen can be conducted both in a parallel current with the starting solution to be hydrogenated, as well as in a counter current above the catalyst.

Suitable systems for the implementation of a hydrogenation according to the suspension regime, as well as for the hydrogenation in the fluid catalyst bed and in the fixed catalyst bed are known from the state of the art, for example from Ullmanns Enzyklopadie der Technischen Chemie, 4^to edition, volume 13, pages 135 and following, as well as by PN Rylander, "Hydrogenation and Dehydrogenation" in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition on CD-ROM.

As a rule, the hydrogenation is carried out under elevated hydrogen pressure, for example at a hydrogen partial pressure of at least 10 bar, preferably at least 20 bar, and in particular at least 40 bar. As a general rule, the partial pressure of hydrogen should not exceed a value of 500 bar, especially 350 bar. The hydrogen partial pressure is particularly preferably in the range from 40 to 200 bar. The reaction temperatures are generally at least 40 ° C, and frequently do not exceed a value of 250 ° C. The hydrogenation process is carried out in particular at temperatures in the range from 80 to 150 ° C.

Due to the high catalyst activity, relatively small amounts of catalyst are required, based on the starting material used. Thus, in the batch suspension regime generally less than 1% by mole will be used, for example 10³% by mole to 0.5% by mole of ruthenium, based on 1 mole of sugar. In the continuous conditioning of the hydrogenation process, the starting material to be hydrogenated will usually be conducted in an amount of 0.02 to 2 kg / (1 (catalyst) * h), and preferably in an amount of 0.07 to 0.7 kg / (1 (catalyst) * h) above the catalyst.

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The following examples serve for a more detailed explanation of the invention:

I. Obtaining the catalysts used according to the invention

1. Prescription A: Halogen-free pulverulent catalyst, not calcined

A defined quantity of the respective carrier material was impregnated with the maximum amount of a solution of ruthenium (III) nitrosylnitrate in water, which could be absorbed by the respective carrier material. The maximum amount absorbed by the respective support material was previously determined by means of an authentic test. The concentration of the solution was respectively measured so that the desired concentration of ruthenium resulted in the support material.

The solid product obtained was then dried for 13 hours at 120 ° C in a drying cabinet. The residual water content was below 1% by weight (determined as weight loss of a sample dried 10 minutes at 300 ° C or 1 bar).

The solid product thus obtained was reduced in a reaction tube for 4 hours at 300 ° C in a stream of hydrogen at normal pressure. After cooling and inerting with nitrogen, the catalyst was passivated by passing 5% by volume of oxygen in nitrogen for a time interval of 2 hours.

2. Prescription B: Halogen-free pulverulent catalyst, stirred, dried, not calcined

The preparation was carried out analogously to prescription A, but drying was carried out in a rotary ball kiln. The residual water content was below 1% by weight.

3. Prescription C: Powder catalyst, halogen-free, calcined

The preparation was carried out analogously to prescription B, but the solid product obtained after drying was heated for 4 hours at 400 ° C in a stream of air before being hydrogenated.

Four. Prescription D: Halogen pulverulent catalyst, not calcined

The preparation was carried out analogously to prescription B, but instead of ruthenium (III) nitrosylnitrate, ruthenium (III) chloride was used.

5. Prescription E: Catalyst stick, halogen-free, uncalcined

A defined number of cylindrical support material bars (diameter 4 mm, length 3 to 10 mm) were impregnated with the maximum amount of a solution of ruthenium (III) nitrosylnitrate in water, which could be absorbed by the respective support material. The maximum amount absorbed by the respective support material had previously been determined by means of an authentic sample. The dissolution concentration was respectively measured in such a way that the desired concentration of ruthenium resulted in the support material.

Thereafter the bars obtained impregnated for 13 hours at 120 ° C were dried in a rotary ball oven. The residual water content was below 1% by weight.

The dried rods thus obtained were reduced in a rotary ball furnace for 4 hours at 300 ° C in a stream of hydrogen at normal pressure. After cooling and inerting with nitrogen, the catalyst thus obtained was passivated by passage of 5% by volume of oxygen in nitrogen for a time interval of 2 hours.

TABLE 1

Catalysts

<td>Catalyst No.</td><td>Ruthenium content [% by weight]</td><td>Prescription</td><td>Medium</td>

<td>K1</td><td> 5</td><td>B</td><td>Yes₂ dust¹’</td>

<td>K2 (V)</td><td> 5</td><td>D</td><td>Yes₂ dust¹’</td>

<td>K3</td><td> 5</td><td>TO</td><td>Yes₂ dust¹’</td>

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<td>K4 (V)</td><td> 5</td><td>c</td><td>S1O2 powder¹’</td>

<td>K5 (V)</td><td> 5</td><td>B</td><td>(X-AI2O3 powder²’</td>

<td>K6 (V)</td><td> 5</td><td>B</td><td>Θ-ΑΙ2Ο3 powder³’</td>

<td>K7 (V)</td><td> 5</td><td>B</td><td>T1O2 powder⁴’</td>

<td>K8</td><td> 1</td><td>AND</td><td>S1O2 Bars * '</td>

<td colspan="4">V Comparative catalyst 1) Silica gel powder with S1O2 content&gt; 99.95% by weight, a specific BET surface of 523 m²/ g, a water absorption of 1.4 ml / g, a pore volume of 0.75 ml / g (determined by nitrogen porometry according to DIN 66134). a defined pore size of 60 Á a particle size of 63 to 200 μιη; 2) Alpha aluminum oxide powder with an AI2O3 content&gt; 99.95% by weight, a specific BET surface of 7 m²/ g, a water absorption of 0.84 ml / g, a particle size of &lt;100 μιη; 3) Aluminum oxide theta powder with an AI2O3 content&gt; 99.95% by weight, a specific BET surface of 80 m²/ g, a water absorption of 1.05 ml / g, a pore volume of 0.67 ml / g (DIN 66134), a particle size of &lt;100 pm; 4) Titanium dioxide powder with a TIO2 content&gt; 99.9% by weight a specific BET surface of 325 m²/ g, a water absorption of 0.84 ml / g, a particle size of &lt;63 pm; 5) Silica gel bars (d 4 mm, 11 to 10 mm) of silica gel with a content of S1O2&gt; 99.5% by weight (0.3% by weight of Na2Ü), a specific BET surface of 169 m²/ g, a water absorption of 0.95 ml / g, a pore volume of 0.7 ml / g (DIN 66134).</td>

II. Hydrogenated xylose in suspension (examples 1 and 2, comparative examples V1 to V5)

General hydrogenation prescription

1200 ml of a 30% by weight solution of xylose in water together with 3 grams of the respective catalyst were placed in a 2.5 liter autoclave with stirrer, sample extraction devices and a pressurizer for hydrogen. The autoclave was inerted with nitrogen. Then 100 bar of hydrogen was applied under pressure and the autoclave was heated to 90 ° C. During the reaction it was stirred at 1000 rpm. For the determination of the conversion, samples were regularly drawn during the reaction and the content of xylose, xylite and other products was determined by means of HPLC. The reaction was stopped no later than after 10 hours. Table 2 indicates the time that is necessary to achieve maximum performance. In addition, the selectivity with respect to xylite formation is indicated, which could be determined with an accuracy of approximately 0.5% (absolute).

ES 2 312 596 T3

TABLE 2

<td>Example</td><td>Catalyst No.</td><td>Medium</td><td>t-max. [h]</td><td>Conversion [%]</td><td>Selectivity [h]</td>

<td> 1</td><td>K1</td><td>S1O2 powder</td><td> 3</td><td> 99,85</td><td> &gt;98,5</td>

<td>SAW</td><td>K2 (V)</td><td>Yes₂ dust</td><td> 7</td><td> 99,85</td><td> &gt;98,5</td>

<td> 2</td><td>K3</td><td>S1O2 powder</td><td> 5</td><td> 99,95</td><td> &gt;98,5</td>

<td>V2</td><td>K4 (V)</td><td>Yes₂ dust</td><td> 10</td><td> 99,96</td><td> &gt;98,5</td>

<td>V3</td><td>K5 (V)</td><td>OC-AI2O3 powder</td><td> ' 10</td><td> 94,15</td><td> 98,5</td>

<td>V4</td><td>K6 (V)</td><td>Θ-ΑΙ2Ο3 powder</td><td> 10</td><td> 99,53</td><td> &gt;98,5</td>

<td>V5</td><td>K7 (V)</td><td>Uncle₂ dust</td><td> 10</td><td> 76,84</td><td> 98,2</td>

The results show that the catalysts according to the invention have better reactivities with comparable or better selectivities than catalysts not corresponding to the invention.

III. Hydrogenated manose, maltose and lactose in suspension (examples 3, 4 and 5)

Analogously to the general hydrogenation prescription indicated in II, 1200 ml of a 30% by weight solution of the respective mono- or disaccharide in water were hydrogenated together with 3 g of the respective catalyst at 50 bar of hydrogen and at a temperature of 120 ° C. Conversion and selectivity were determined as described in II by means of HPLC. Table 3 indicates the time that is necessary to achieve a maximum conversion (> 99.8%). In addition, the selectivity with respect to the formation of the desired sugar alcohol is indicated.

TABLE 3

<td>Example</td><td>Catalyst No.</td><td>Educto</td><td>Product</td><td>t-max. [hl</td><td>Conversion [%]</td><td>Selectivity [h]</td>

<td> 3</td><td>K1</td><td>Crafty</td><td>Little hand</td><td> 2</td><td> &gt;99,8</td><td> 96</td>

<td> 4</td><td>K1</td><td>Maltose</td><td>Maltite</td><td> 1</td><td> &gt;99,8</td><td> 69</td>

<td> 5</td><td>K1</td><td>Lactose</td><td>Lactite</td><td> 3</td><td> &gt;99,8</td><td> 87</td>

III. Hydrogenated xylose and lactose in a fixed catalyst bed (examples 6 and 7)

A heatable reaction tube made of refined steel served as the reactor, which was loaded with K8 catalyst. The reaction arrangement featured a feed pump for the starting materials, a circulation pump, devices for the extraction of samples, as well as a separator with level regulation and exhaust gas regulation.

In this reaction arrangement, a 30% by weight solution of the respective mono- or disaccharide was circulated at a temperature of 100 ° C and a hydrogen pressure of 50 bar at a rate of 50 ml / (g (catalyst ) * h), and meanwhile the reduction of educt, the increase of product and the formation of secondary products were determined by means of the analytical described in II. Upon reaching a conversion of 99.4%, the reaction was stopped. The contact time required to achieve maximum conversion is indicated in Table 4 together with the selectivity. Contact time = volume (solution) / volume (reaction tube) * reaction time.

ES 2 312 596 T3

TABLE 4

<td>Example</td><td>Educto</td><td>Product</td><td>Contact time [h]</td><td>Selectivity [%]</td>

<td> 6</td><td>Xylose</td><td>Xilite</td><td> 0,81</td><td> 97,2</td>

<td> 7</td><td>Lactose</td><td>Lactite</td><td> 1,0</td><td> 94,1</td>