EP1572607A1 - Continuous method for the production of sugar alcohols - Google Patents

Continuous method for the production of sugar alcohols

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Publication number
EP1572607A1
EP1572607A1 EP03780110A EP03780110A EP1572607A1 EP 1572607 A1 EP1572607 A1 EP 1572607A1 EP 03780110 A EP03780110 A EP 03780110A EP 03780110 A EP03780110 A EP 03780110A EP 1572607 A1 EP1572607 A1 EP 1572607A1
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EP
European Patent Office
Prior art keywords
hydrogenation
ruthenium
carrier material
solution
production
Prior art date
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Withdrawn
Application number
EP03780110A
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German (de)
French (fr)
Inventor
Jan-Dirk Arndt
Katrin Klass
Frederik Van Laar
Stephan Herwig
Jochem Henkelmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
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Filing date
Publication date
Priority claimed from DE2002158089 external-priority patent/DE10258089A1/en
Priority claimed from DE2003152336 external-priority patent/DE10352336A1/en
Application filed by BASF SE filed Critical BASF SE
Publication of EP1572607A1 publication Critical patent/EP1572607A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
    • C07C29/136—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH
    • C07C29/14—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group
    • C07C29/141—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group with hydrogen or hydrogen-containing gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/462—Ruthenium
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
    • C07C31/18—Polyhydroxylic acyclic alcohols
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
    • C07C31/18—Polyhydroxylic acyclic alcohols
    • C07C31/26—Hexahydroxylic alcohols
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/08—Silica
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J33/00—Protection of catalysts, e.g. by coating

Definitions

  • the present invention relates to a continuous process for the production of sugar alcohols by catalytic hydrogenation of suitable saccharides.
  • US 4,380,680, US 4,487,980, US 4,413,152 and US 4,471,144 describe the production of sorbitol by catalytic hydrogenation of glucose, in which catalysts are used which contain ruthenium on a support material which is stable under hydrothermal conditions.
  • 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) are proposed as hydrothermal carrier materials.
  • No. 4,503,274 discloses catalysts for the hydrogenation of glucose to sorbitol, which are prepared by impregnating a support which is stable under hydrothermal conditions with an aqueous ruthenium halide solution and then hydrogenating the solid at temperatures in the range from 100 to 300.degree.
  • No. 3,963,788 describes the hydrogenation of corn starch hydrolyzates to sorbitol over ruthenium catalysts in which the ruthenium was supported with a special zeolite based on an aluminosilicate.
  • No. 3,963,789 proposes crystalline aluminosilicate clays, in particular montmorillonite, as supports for ruthenium catalysts.
  • FR-A 2526782 describes the use of a ruthenium chloride prepared by reacting sodium chloride and ruthenium via Na 2 RuCI 6 for the production of ruthenium catalysts supported on silicon dioxide for the hydrogenation of mono- and oligosaccharides, for example for the production of sorbitol.
  • the present invention is therefore based on the object of providing a continuous process for the production of sugar alcohols by catalytic hydrogenation of the corresponding saccharides which form the desired sugar alcohols during hydrogenation, which avoids the disadvantages mentioned above and in particular the desired sugar alcohols with better space-time - Provides yields in which fewer by-products are obtained and which allows longer catalyst lives.
  • This object was surprisingly achieved by a continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous solution of a saccharide, which forms the corresponding sugar alcohol on hydrogenation, over a ruthenium catalyst, which is obtainable by:
  • step ii) reduction of the solid obtained in i) with hydrogen at a temperature in the range from 100 to 350 ° C., wherein step ii) is carried out immediately after step i), which is characterized in that the aqueous saccharide solution to be hydrogenated is brought into contact with the carrier material before the hydrogenation.
  • Suitable saccharides basically include all known tetroses, pentoses, hexoses and heptoses, namely both aldoses and ketoses and their di- and oligosaccharides.
  • the monosaccharides which can be used in the process according to the invention include, for example: erythrose, threose, ribose, arabinose, xylose, lyxose, allose, old rose, mannose, gulose, idose, galactose, talose, erythrulose, ribulose, xylulose, psicose , Tagatose, Glucose, Fructose and Gulose both the D-form and the L-form.
  • Invert sugar obtained by hydrolysis of sucrose is also suitable.
  • disacharides are: maltose, isomaltose, lactose, cellobiose, melobiose and sucrose.
  • Suitable mono- and oligosaccharides for the hydrogenation process according to the invention are in particular the monosaccharides mannose for the production of mannitol, galactose for the production of dulcite (galactite) and xylose for the production of xylitol, preferably the D-form of the monosaccharides, and the disaccharides maltose for the production of maltitol, isomaltulose (palatinose) for the production of isomaltitol and lactose for the production of lactitol.
  • the preferred starting material for the production of the sugar alcohol sorbitol is glucose and glucose-rich syrups such as hydrolysates of corn starch, wheat starch and potato starch.
  • glucose-rich syrups such as hydrolysates of corn starch, wheat starch and potato starch.
  • D-sorbitol by hydrogenation of the D-form of the aforementioned monosaccharides is of particular interest.
  • the other mono- and oligosaccharides mentioned can also be hydrogenated to the corresponding sugar alcohols in the presence of the ruthenium catalysts according to the invention.
  • the hydrogenation of aldoses to sugar alcohols which have the same configuration as the sugar used with regard 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 C atom, which carries the carbonyl function in furanosis.
  • the Isolation of the pure sugar alcohol from this mixture is generally possible without problems.
  • the mono- and oligosaccharides can be used as such or as mixtures, the educts preferably being used in pure form.
  • the high activity of the catalysts used in the process according to the invention can be attributed to the particularly good distribution of the ruthenium on the surface of the support material and to the substantial absence of halogen in the support material. Due to the production process, the ruthenium is present in the catalysts according to the invention as metallic ruthenium.
  • Electron microscopic investigations (TEM) of the catalysts have shown that the ruthenium on the support material is in atomically dispersed form and / or in the form of ruthenium particles which are almost exclusively, i.e. more than 90%, preferably more than 95%, based on the number of visible particles, are present as isolated particles with diameters below 10 nm, in particular below 7 nm.
  • the catalyst contains essentially none, i.e. less than 10%, in particular less than 5%, of ruthenium particles and / or agglomerates of ruthenium particles with diameters above 10 nm.
  • the use of halogen-free ruthenium precursors and solvents in the production also means that the chlorine content of the catalysts used according to the invention is below 0.05 % By weight ( ⁇ 500 ppm), based on the total weight of the catalyst.
  • An essential component of the catalysts used in the process according to the invention is the support material based on amorphous silicon dioxide.
  • amorphous means that the proportion of crystalline silicon dioxide phases makes up less than 10% of the carrier material.
  • the support materials used to produce the catalysts can have superstructures which are formed by regularly arranging pores in the support material.
  • the carrier material can also be another oxidic material, for example MgO, CaO, TiO 2 , ZrO 2 , Fe 2 O 3 or alkali metal oxide.
  • the carrier material used is also halogen-free, ie the halogen content is less than 500 ppm.
  • the carrier material preferably contains no more than 1% by weight and in particular no more than 0.5% by weight and in particular no detectable amounts ( ⁇ 500 ppm) of aluminum oxide, calculated as Al 2 O 3 .
  • support materials are used which contain less than 500 ppm Fe 2 O 3 .
  • the proportion of alkali metal oxide generally results from the production of the carrier material and can be up to 2% by weight. It is often less than 1% by weight.
  • Alkali metal oxide-free carriers ( ⁇ 0.1% by weight) are also suitable.
  • the proportion of MgO, CaO, TiO 2 or ZrO 2 can make up to 10% by weight of the carrier material and is preferably not more than 5% by weight.
  • carrier materials which do not contain any detectable amounts of these metal oxides are also suitable.
  • carrier materials which have a specific surface area in the range from 50 to 700 m 2 / g, in particular in the range from 80 to 600 m 2 / g and especially in the range from 100 to 600 m 2 / g (BET surface area in accordance with DIN 66131 ).
  • specific (BET) surface area is in the range from 200 to 600 m 2 / g.
  • specific surface area is in particular in the range from 100 to 300 m 2 / g.
  • Suitable amorphous carrier materials based on silicon dioxide are familiar to the person skilled in the art and are commercially available (see, for example, OW Flörke, “Silica” in Ullmann's Encyclopedia of Industrial Chemistry 5th ed. On CD-ROM). They can be produced both naturally and artificially Examples of suitable amorphous support materials based on silicon dioxide are diatomaceous earth, silica gels, pyrogenic silica and precipitated silica. In a preferred embodiment of the invention, the catalysts contain silica gels as support materials.
  • the carrier material can have different shapes. If the process is designed as a suspension process, it is usual to prepare the catalysts according to the invention. usually use the carrier material in the form of a finely divided powder.
  • the particle size of the powder particles is preferably in the range from 1 to 200 ⁇ m and in particular in the range from 10 to 100 ⁇ m.
  • shaped bodies made of the carrier material are usually used, which can be obtained, for example, by extrusion, extrusion or tableting and which can have, for example, the shape of spheres, tablets, cylinders, strands, rings or hollow cylinders, stars and the like.
  • the dimensions of these moldings usually range from 1 mm to 25 mm. Catalyst strands with strand diameters of 2 to 5 mm and strand lengths of 2 to 25 mm are often used.
  • the content of ruthenium in the catalysts can be varied over a wide range. As a rule, it will be at least 0.1% by weight, preferably at least 0.2% by weight, and often will not exceed a value of 10% by weight, in each case based on the weight of the carrier material.
  • the ruthenium content is preferably in the range from 0.2 to 7% by weight and in particular in the range from 0.4 to 5% by weight.
  • the ruthenium catalysts used in the process according to the invention are generally prepared by first treating the support material with a halogen-free aqueous solution of a low molecular weight ruthenium compound, hereinafter referred to as (ruthenium) precursor, in such a way that the desired amount of ruthenium is absorbed by the carrier material. This step is also referred to below as watering. The carrier thus treated is then dried at the temperatures indicated above. If necessary, the solid thus obtained is then treated again with the aqueous solution of the ruthenium precursor and dried again. This process is repeated until the amount of ruthenium compound taken up by the support material corresponds to the desired ruthenium content in the catalyst.
  • ruthenium halogen-free aqueous solution of a low molecular weight ruthenium compound
  • the treatment or impregnation of the carrier material can take place in different ways and depends in a known manner on the shape of the carrier material.
  • the carrier material can be sprayed or rinsed with the precursor solution or the carrier material can be suspended in the precursor solution.
  • the carrier material can be suspended in the aqueous solution of the ruthenium precursor and filtered off from the aqueous supernatant after a certain time.
  • the ruthenium content of the catalyst can then be controlled in a simple manner via the amount of liquid taken up and the ruthenium concentration of the solution.
  • the support material can also be impregnated, for example, by treating the support with a defined amount of the aqueous solution of the ruthenium precursor which corresponds to the maximum amount of liquid which the support material can hold.
  • the liquid can be sprayed onto the carrier material, for example.
  • Suitable apparatus for this are the apparatuses usually used for mixing liquids with solids (see Vauck / Müller, Basic Operations of Chemical Process Engineering, 10th edition, German Publisher for Basic Industry, 1994, pp. 405 ff.), For example tumble dryers, water drums, drum mixers, paddle mixers and like.
  • Monolithic supports are usually rinsed with the aqueous solutions of the ruthenium precursor.
  • the aqueous solutions used for impregnation are halogen-free, ie they contain no or less than 100 ppm halogen. Therefore, only ruthenium compounds that do not contain chemically bound halogen and that are sufficiently soluble in the aqueous solvent are used as ruthenium precursors. These include, for example, ruthenium (III) nitrosyl nitrate (Ru (NO) (NO 3 ) 3 ), ruthenium (III) acetate and the alkali metal ruthenates (IV) such as sodium and potassium ruthenate (IV).
  • aqueous denotes water and mixtures of water with up to 50% by volume, preferably not more than 30% by volume and in particular not more than 10% by volume of one or more water-miscible organic solvents, for example mixtures of Water with -CC alkanols such as methanol, ethanol, n- or isopropanol. Water is often used as the sole solvent.
  • the aqueous solvent will often 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, in order to stabilize the ruthenium precursor in the solution. In many cases, therefore, a halogen-free mineral acid, e.g. B.
  • the concentration of the ruthenium precursor in the aqueous solutions naturally depends on the amount of ruthenium precursor to be applied and the absorption capacity of the carrier material for the aqueous solution and is generally in the range from 0.1 to 20% by weight.
  • Drying can be carried out using the customary methods of drying solids while maintaining the above-mentioned temperatures. Compliance with the upper limit of the drying temperatures according to the invention is important for the quality, i.e. the activity of the catalyst is important. Exceeding the drying temperatures given above leads to a significant loss of activity. Calcining the support at higher temperatures, e.g. Above 300 ° C or even 400 ° C, as proposed in the prior art, is not only superfluous but also has a disadvantageous effect on the activity of the catalyst.
  • the drying of the solid impregnated with the ruthenium precursor usually takes place under normal pressure. A reduced pressure can also be used to promote the drying. Often, to promote drying, a gas stream will be passed over or through the material to be dried, e.g. Air or nitrogen.
  • the drying time naturally depends on the desired degree of drying and the drying temperature and is generally in the range from 2 h to 30 h, preferably in the range from 4 h to 15 h.
  • the treatment of the treated carrier material is preferably carried out to such an extent that the content of water or volatile solvent components before the reduction ii) is less than 5% by weight, in particular not more than 2% by weight and particularly preferably not more than 1% by weight .-%, based on the total weight of the solid.
  • the stated weight fractions relate to the weight loss of the solid, determined at a temperature of 300 ° C., a pressure of 1 bar and a duration of 10 min. In this way, the activity of the catalysts according to the invention can be increased further.
  • Drying is preferably carried out by moving the solid treated with the precursor solution, for example by drying the solid in a rotary motion. tube furnace or a rotary kiln. In this way, the activity of the catalysts according to the invention can be increased further.
  • the solid obtained after drying is converted into its catalytically active form by hydrogenating the solid at the temperatures indicated above in a manner known per se.
  • the carrier material is brought into contact with hydrogen or a mixture of hydrogen and an inert gas at the temperatures indicated above.
  • the hydrogen partial pressure is of minor importance for the result of the reduction and can be varied in the range from 0.2 bar to 1.5 bar.
  • the hydrogenation of the catalyst material often takes place at normal hydrogen pressure in the hydrogen stream.
  • the hydrogenation is preferably carried out by moving the solid obtained in i), for example by hydrogenating the solid in a rotary tubular furnace or a rotary ball furnace. In this way, the activity of the catalysts according to the invention can be increased further.
  • the catalyst can be passivated in a known manner to improve handling, e.g. by briefly using the catalyst with an oxygen-containing gas, e.g. Air, but preferably treated with an inert gas mixture containing 1 to 10% by volume of oxygen.
  • an oxygen-containing gas e.g. Air
  • an inert gas mixture containing 1 to 10% by volume of oxygen
  • the saccharide is preferably hydrogenated by hydrogenating an aqueous solution of the respective saccharide or, in the case of invert sugar, as the starting material, the saccharide mixture.
  • aqueous is to be understood here in the manner defined above.
  • Water is expediently used as the sole solvent, which may contain small amounts of a preferably halogen-free acid for adjusting the pH.
  • the monosaccharide is used as an aqueous solution which has a pH in the range from 4 to 10, and especially in the range from 5 to 7.
  • the concentration of saccharide in the liquid phase can in principle be chosen freely and is frequently 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 saccharide solution is brought into contact with the support material before the hydrogenation, ie before it comes into contact with the ruthenium catalyst. The purpose of this is that the saccharide solution becomes saturated on the support material, ie above all on silicon dioxide, and as a result less support material is released from the catalyst, which has an advantageous effect on the service life (service life) of the catalyst.
  • the saccharide solution can be brought into contact with the carrier material in a number of ways, for example by suspending the powdery carrier material in the saccharide solution or by passing the saccharide solution through shaped bodies made of carrier material.
  • the passage of the saccharide solution through silica strands is a particularly preferred embodiment of the method according to the invention, in particular if the solution is pressed under pressure through tubes filled with silica strands.
  • Another advantage of the method according to the invention results from the fact that when the saccharide solution is pressed through the silica strands, any oligomeric sugars still present in the saccharide solution are retained and the purity of the sugar alcohol formed is thus increased. This can be observed particularly when using starch hydrolyzates as saccharides.
  • the actual hydrogenation is usually carried out in analogy to the known hydrogenation processes for the production of sugar alcohols, as described in the prior art mentioned at the beginning.
  • the liquid phase containing the saccharide is brought into contact with the catalyst in the presence of hydrogen.
  • the catalyst can either be suspended in the liquid phase (suspension mode) or the liquid phase is passed over a fluidized catalyst bed (fluidized bed mode) or a fixed catalyst bed (fixed bed mode).
  • the hydrogenation can be carried out either continuously or batchwise.
  • the process according to the invention is preferably carried out in trickle-bed reactors according to the fixed bed procedure.
  • the hydrogen can be passed both in cocurrent with the solution of the starting material to be hydrogenated and in countercurrent over the catalyst.
  • Suitable apparatus for carrying out a hydrogenation according to the suspension procedure and also for hydrogenation on a fixed catalyst bed are known from the prior art, for example from Ulimann's Encyclopedia of Industrial Chemistry, 4th edition, volume 13, p. 135 ff. And from PN Rylander, “Hydrogenation and Dehydrogenation "in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. on CD-ROM.
  • the hydrogenation is carried out at elevated hydrogen pressure, e.g. at a hydrogen partial pressure of at least 10 bar, preferably at least 20 bar and in particular at least 40 bar.
  • the hydrogen partial pressure will not exceed a value of 500 bar, in particular 350 bar.
  • the hydrogen partial pressure is particularly preferably in the range from 40 to 200 bar.
  • the reaction temperatures are usually at least 40 ° C and will often not exceed 250 ° C.
  • the hydrogenation process is carried out at temperatures in the range from 80 to 150 ° C.
  • the starting material is hydrogenated in an amount of 0.05 to 2 kg / (l (catalyst) * h), in particular in an amount of 0.07 to 0.7 kg / (l (catalyst) * h) over the Lead catalyst.
  • the sugar alcohol can be obtained, for example, by evaporation with subsequent crystallization (DE-A 2350690, EP-A 32288, EP-A 330352) or spray drying (DK 133603, DD 277176) the catalyst is separated off by customary processes and the reaction solution is subjected to decolorization with suitable filter aids and / or treatment with ion exchange to remove metal ions, gluconates or other organic acids.
  • sorbitol can be obtained from the reaction mixtures obtained in this way by selective crystallization.
  • the process according to the invention is distinguished on the one hand by the high space-time yields achieved and, when using glucose as the starting material, also by a high product selectivity.
  • the process according to the invention is distinguished by a particularly long service life of the ruthenium catalysts, which makes the process particularly economically attractive.
  • the catalysts used in this process can of course be regenerated according to the methods known to those skilled in the art for noble metal catalysts such as ruthenium catalysts.
  • treatment of the catalyst with oxygen as described in BE 882279 treatment with dilute, halogen-free mineral acids as described in US 4,072,628, or treatment with hydrogen peroxide, e.g. in the form of aqueous solutions with a content of 0.1 to 35% by weight, or the treatment with other oxidizing substances, preferably in the form of halogen-free solutions.
  • the catalyst is reactivated with a solvent, e.g. Water, rinse.
  • a defined amount of the respective carrier material was impregnated with the maximum amount of a solution of ruthenium (III) nitrosyl nitrate in water that could be absorbed by the respective carrier material.
  • the maximum amount absorbed by the respective carrier material was previously based on an authentic sample. been agreed.
  • the concentration of the solution was measured such that the desired concentration of ruthenium in the support material resulted.
  • the solid obtained in this way was then dried in a rotary ball oven at 120 ° C. for 13 h.
  • the residual water content was below 1% by weight.
  • the solid obtained in this way was reduced in a rotary kiln for 4 h 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 into nitrogen over a period of 120 min.
  • the preparation was carried out analogously to regulation A, but the solid obtained after drying was heated to 400 ° C. in an air stream for 4 h before the hydrogenation.
  • a defined amount of cylindrical support material strands (diameter 4 mm, length 3 to 10 mm) was impregnated with the maximum amount of a solution of ruthenium (III) nitrosyl nitrate in water which could be taken up by the respective support material.
  • the maximum amount absorbed by the respective carrier material had previously been determined on the basis of an authentic sample.
  • the concentration of the solution was measured such that the desired concentration of ruthenium in the support material resulted.
  • the soaked, soaked strands were then dried for 13 hours at 120 ° C. in a rotary ball oven.
  • the residual water content was less than 1% by weight.
  • the dried strands obtained in this way were reduced in a rotary kiln for 4 h at 300 ° C. in a stream of hydrogen at normal pressure.
  • the catalyst obtained in this way was passivated by passing 5% by volume of oxygen into nitrogen over a period of 120 min. »
  • the preparation was carried out analogously to regulation D, but ruthenium (III) chloride was used instead of ruthenium (III) nitrosyl nitrate.
  • a reaction unit consisting of a main reactor with circulation and a post-reactor is charged with the ruthenium catalyst prepared under I.
  • aqueous solution of corn starch hydrolyzate with a glucose concentration of 40% is passed under pressure through a tube filled with silica strands. This solution is then fed into the main reactor, which had a top temperature of 80 to 130 ° C., and then passed through the post-reactor, the top temperature of which was adjusted to the bottom temperature of the main reactor. The hydrogenation was carried out at a pressure of 140 bar.
  • the process delivers a conversion of 99.8% and a selectivity based on sorbitol of 99.3%.
  • a reaction unit consisting of a main reactor with circulation and a post-reactor is charged with the ruthenium catalyst prepared under I.
  • aqueous solution of xylose (source: Aldrich, purity 99.6%) with a concentration of 30% is passed under pressure through a tube filled with silica strands hazards. This solution is then fed into the main reactor, which had a top temperature of 80 to 130 ° C., and then passed through the post-reactor, the top temperature of which was adjusted to the bottom temperature of the main reactor. The hydrogenation was carried out at a pressure of 90 bar.
  • the process delivers a conversion of 99.8% and a selectivity based on xylitol of 98.5%.

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

The invention relates to a continuous method for the production of sugar alcohols by catalytic hydrogenation of an aqueous solution of a saccharide, which forms the corresponding sugar alcohol on hydrogenation, on a ruthenium catalyst which may be obtained by: i) a single or multiple treatment of a support material made from 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 obtained in step i) with hydrogen at a temperature in the range 100 to 350 °C, whereby step ii) is carried out directly after step i). The aqueous saccharide solution is brought into contact with the support material before the hydrogenation.

Description

Kontinuierliches Verfahren zur Herstellung von ZuckeralkoholenContinuous process for the production of sugar alcohols
Beschreibungdescription
Die vorliegende Erfindung betrifft ein kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen durch katalytische Hydrierung geeigneter Saccharide.The present invention relates to a continuous process for the production of sugar alcohols by catalytic hydrogenation of suitable saccharides.
Die großtechnische Herstellung des Zuckeralkohols Sorbit erfolgt durch katalytische Hydrierung von Glukose, Fruktose, Saccharose oder Invertzucker (siehe H. Schiweck et al. Sugar Alcohols in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. on CD-ROM). Zu diesem Zweck wurden als Katalysatoren bislang in erster Linie Nickel- Katalysatoren, wie z.B. Nickel-Trägerkatalysatoren oder Raney-Nickel eingesetzt. Verschiedentlich wurde auch über den Einsatz von Ruthenium-haltigen Katalysatoren für diesen Zweck berichtet. In der Regel handelt es sich bei Ruthenium-Katalysatoren um sogenannte Trägerkatalysatoren, die Ruthenium auf einem oxidischen oder organischen Träger wie Kohle enthalten.The large-scale production of the sugar alcohol sorbitol takes place by catalytic hydrogenation of glucose, fructose, sucrose or invert sugar (see H. Schiweck et al. Sugar Alcohols in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. On CD-ROM). For this purpose, nickel catalysts, such as e.g. Nickel supported catalysts or Raney nickel are used. There have also been reports on the use of catalysts containing ruthenium for this purpose. As a rule, ruthenium catalysts are so-called supported catalysts which contain ruthenium on an oxidic or organic support such as coal.
So beschreiben die US 4,380,680, US 4,487,980, US 4,413,152 und die US 4,471,144 die Herstellung von Sorbit durch katalytische Hydrierung von Glucose, in denen Kata- lysatoren eingesetzt werden, die Ruthenium auf einem unter hydrothermalen Bedingungen stabilen Trägermaterial enthalten. Als hydrothermale Trägermaterialien werden alpha-Aluminiumoxid (US 4,380,680), Titan(IV)oxid (US 4,487,980), mit Titan- (IV)halogenid behandeltes Aluminiumoxid (US 4,413,152) und theta-Aluminiumoxid (US 4,471,144) vorgeschlagen.US 4,380,680, US 4,487,980, US 4,413,152 and US 4,471,144 describe the production of sorbitol by catalytic hydrogenation of glucose, in which catalysts are used which contain ruthenium on a support material which is stable under hydrothermal conditions. 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) are proposed as hydrothermal carrier materials.
Aus der US 4,503,274 sind Katalysatoren für die Hydrierung von Glucose zu Sorbit bekannt, die durch Imprägnieren eines unter hydrothermalen Bedingungen stabilen Trägers mit einer wässrigen Rutheniumhalogenid-Lösung und anschließendes Hydrieren des Feststoffs bei Temperaturen im Bereich von 100 bis 300°C hergestellt werden.No. 4,503,274 discloses catalysts for the hydrogenation of glucose to sorbitol, which are prepared by impregnating a support which is stable under hydrothermal conditions with an aqueous ruthenium halide solution and then hydrogenating the solid at temperatures in the range from 100 to 300.degree.
Die US 3,963,788 beschreibt die Hydrierung von Mais-Stärke-Hydrolysaten zu Sorbit an Ruthenium-Katalysatoren, in denen das Ruthenium mit einem speziellen Zeolithen auf Basis eines Alumosilikats geträgert wurde. Die US 3,963,789 schlägt als Träger für Ruthenium-Katalysatoren kristalline Alumosilikat-Tone, insbesondere Montmorillonit vor. Die FR-A 2526782 beschreibt die Verwendung eines durch Umsetzung von Natriumchlorid und Ruthenium via Na2RuCI6 hergestellten Rutheniumchlorids zur Herstellung von auf Siliziumdioxid geträgerten Ruthenium-Katalysatoren für die Hydrierung von Mono- und Oligosacchariden, z.B. für die Herstellung von Sorbit.No. 3,963,788 describes the hydrogenation of corn starch hydrolyzates to sorbitol over ruthenium catalysts in which the ruthenium was supported with a special zeolite based on an aluminosilicate. No. 3,963,789 proposes crystalline aluminosilicate clays, in particular montmorillonite, as supports for ruthenium catalysts. FR-A 2526782 describes the use of a ruthenium chloride prepared by reacting sodium chloride and ruthenium via Na 2 RuCI 6 for the production of ruthenium catalysts supported on silicon dioxide for the hydrogenation of mono- and oligosaccharides, for example for the production of sorbitol.
Die aus dem Stand der Technik bekannten Verfahren für die Herstellung von Sorbit durch Hydrierung an Ruthenium-Katalysatoren liefern aufgrund der nur mäßigen Aktivität der Katalysatoren Sobit nur mit mäßigen Raum-Zeit-Ausbeuten, bezogen auf den eingesetzten Katalysator. Angesichts der hohen Kosten für Ruthenium lässt daher die Wirtschaftlichkeit dieser Verfahren zu wünschen übrig. Zudem sind die Selektivitäten der Katalysatoren nicht ausreichend, so dass zusätzlicher Aufwand beim Isolieren der Wertprodukte erforderlich ist. Insbesondere wird häufig eine Epimerisierung der Hy- droxygruppen beobachtet.The processes known from the prior art for the production of sorbitol by hydrogenation on ruthenium catalysts only give sobitol with moderate space-time yields, based on the catalyst used, because of the moderate activity of the catalysts. Given the high cost of ruthenium, the economics of these processes leave something to be desired. In addition, the selectivities of the catalysts are not sufficient, so that additional effort is required when isolating the valuable products. In particular, epimerization of the hydroxy groups is frequently observed.
Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, ein kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen durch katalytische Hydrierung der entsprechenden Saccharide, die beim Hydrieren die gewünschten Zuckeralkohole bilden, bereitzustellen, das die oben genannten Nachteile vermeidet und das insbesondere die gewünschten Zuckeralkohole mit bessern Raum-Zeit- Ausbeuten liefert, bei dem weniger Nebenprodukte anfallen und das längere Katalysatorstandzeiten erlaubt.The present invention is therefore based on the object of providing a continuous process for the production of sugar alcohols by catalytic hydrogenation of the corresponding saccharides which form the desired sugar alcohols during hydrogenation, which avoids the disadvantages mentioned above and in particular the desired sugar alcohols with better space-time - Provides yields in which fewer by-products are obtained and which allows longer catalyst lives.
Diese Aufgabe wurde überraschenderweise gelöst durch ein Kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen durch katalytische Hydrierung einer wässrigen Lösung eines Saccharids, das bei der Hydrierung den entsprechenden Zuckeralkohol bildet, an einem Ruthenium-Katalysator, der erhältlich ist durch:This object was surprisingly achieved by a continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous solution of a saccharide, which forms the corresponding sugar alcohol on hydrogenation, over a ruthenium catalyst, which is obtainable by:
i) ein oder mehrfaches Behandeln eines Trägermaterials auf Basis von amorphem Siliziumdioxid mit einer halogenfreien wässrigen Lösung einer niedermolekularen Rutheniumverbindung und anschließendes Trocknen des behandelten Trägermaterials bei einer Temperatur unterhalb 200°C,i) one or more times treatment of a carrier 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 carrier material at a temperature below 200 ° C.,
ii) Reduktion des in i) erhaltenen Feststoffs mit Wasserstoff bei einer Temperatur im Bereich von 100 bis 350°C, wobei man Schritt ii) unmittelbar im Anschluss an Schritt i) durchführt, das dadurch gekennzeichnet ist, dass man die zu hydrierende wässrige Sacscharidlösung vor der Hydrierung mit dem Trägermaterial in Kontakt bringt.ii) reduction of the solid obtained in i) with hydrogen at a temperature in the range from 100 to 350 ° C., wherein step ii) is carried out immediately after step i), which is characterized in that the aqueous saccharide solution to be hydrogenated is brought into contact with the carrier material before the hydrogenation.
Geeignete Saccharide umfassen grundsätzlich alle bekannten Tetrosen, Pentosen, Hexosen und Heptosen und zwar sowohl Aldosen als auch Ketosen sowie deren Di- und Oligosaccaride. Zu den Monosacchariden, die im erfindungsgemässen Verfahren eingesetzt werden können, zählen beispielsweise: Erythrose, Threose, Ribose, Arabi- nose, Xylose, Lyxose, Allose, Altrose, Mannose, Gulose, Idose, Galactose, Talose, Erythrulose, Ribulose, Xylulose, Psicose, Tagatose, Glucose, Fructose und Gulose und zwar sowohl die D-Form als auch die L-Form. Geeignet ist auch Invertzucker, der durch Hydrolyse von Saccharose erhältlich ist. Beispiele für Disacharide sind: Maltose, Isomaltose, Lactose, Cellobiose, Melobiose und Saccharose.Suitable saccharides basically include all known tetroses, pentoses, hexoses and heptoses, namely both aldoses and ketoses and their di- and oligosaccharides. The monosaccharides which can be used in the process according to the invention include, for example: erythrose, threose, ribose, arabinose, xylose, lyxose, allose, old rose, mannose, gulose, idose, galactose, talose, erythrulose, ribulose, xylulose, psicose , Tagatose, Glucose, Fructose and Gulose both the D-form and the L-form. Invert sugar obtained by hydrolysis of sucrose is also suitable. Examples of disacharides are: maltose, isomaltose, lactose, cellobiose, melobiose and sucrose.
Als geeignete Mono- und Oligosaccharide für das erfindungsgemäße Hydrierverfahren sind inbesondere die Monosaccharide Mannose für die Herstellung von Mannit, Galactose für die Herstellung von Dulcit (Galaktit) und Xylose für die Herstellung von Xylit, vorzugsweise die D-Form der Monosaccharide, sowie die Disaccharide Maltose für die Herstellung von Maltit, Isomaltulose (Palatinose) für die Herstellung von Isomaltit und Lactose für die Herstellung von Lactit zu nennen.Suitable mono- and oligosaccharides for the hydrogenation process according to the invention are in particular the monosaccharides mannose for the production of mannitol, galactose for the production of dulcite (galactite) and xylose for the production of xylitol, preferably the D-form of the monosaccharides, and the disaccharides maltose for the production of maltitol, isomaltulose (palatinose) for the production of isomaltitol and lactose for the production of lactitol.
Bevorzugtes Ausgangsmaterial für die Herstellung des Zuckeralkohols Sorbit ist Glucose sowie Glucose-reiche Sirupe wie Maisstärke-, Weizenstärke- und Kartoffel- stärke-Hydrolysate. Die Herstellung von D-Sorbit durch Hydrierung der D-Form der vorgenannten Monosaccharide ist von besonderem Interesse.The preferred starting material for the production of the sugar alcohol sorbitol is glucose and glucose-rich syrups such as hydrolysates of corn starch, wheat starch and potato starch. The production of D-sorbitol by hydrogenation of the D-form of the aforementioned monosaccharides is of particular interest.
Aber auch die anderen genannten Mono- und Oligosaccharide können in Gegenwart der erfindungsgemäßen Ruthenium-Katalysatoren zu den korrespondierenden Zu- ckeralkoholen hydriert werden. Dabei führt die Hydrierung von Aldosen zu Zuckeralkoholen, die hinsichtlich der OH-Gruppen die gleiche Konfiguration wie der eingesetzte Zucker aufweisen, und die Hydrierung von Furanosen in der Regel zu Gemischen zweier diastereomerer Zuckeralkohole, die sich nur in der Konfiguration des C-Atoms unterscheiden, welches in der Furanose die Carbonylfunktion trägt. Die Isolierung des jeweiligen reinen Zuckeralkohols aus dieser Mischung ist in der Regel ohne Probleme möglich.However, the other mono- and oligosaccharides mentioned can also be hydrogenated to the corresponding sugar alcohols in the presence of the ruthenium catalysts according to the invention. The hydrogenation of aldoses to sugar alcohols which have the same configuration as the sugar used with regard 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 C atom, which carries the carbonyl function in furanosis. The Isolation of the pure sugar alcohol from this mixture is generally possible without problems.
Die Mono- und Oligosaccharide können als solche oder als Mischungen eingesetzt werden, wobei man vorzugsweise die Edukte in Reinform einsetzt.The mono- and oligosaccharides can be used as such or as mixtures, the educts preferably being used in pure form.
Es wird vermutet, dass die hohe Aktivität der im erfindungsgemäßen Verfahren eingesetzten Katalysatoren auf die besonderes gute Verteilung des Rutheniums auf der Oberfläche des Trägermaterials und auf die weitgehende Abwesenheit von Halogen im Trägermaterial zurückgeführt werden kann. Herstellungsbedingt liegt das Ruthenium in den erfindungsgemäßen Katalysatoren als metallisches Ruthenium vor.It is suspected that the high activity of the catalysts used in the process according to the invention can be attributed to the particularly good distribution of the ruthenium on the surface of the support material and to the substantial absence of halogen in the support material. Due to the production process, the ruthenium is present in the catalysts according to the invention as metallic ruthenium.
Elektronenmikroskopische Untersuchungen (TEM) der Katalysatoren haben gezeigt, dass das Ruthenium auf dem Trägermaterial in atomar-disperser Form und/oder in Form von Ruthenium-Partikeln vorliegt, die nahezu ausschließlich, d.h. zu mehr als 90 %, vorzugsweise zu mehr als 95 %, bezogen auf die Anzahl der sichtbaren Partikel, als isolierte Partikel mit Durchmessern unterhalb 10 nm, insbesondere unterhalb 7 nm vorliegen. Mit anderen Worten, der Katalysator enthält im Wesentlichen keine, d.h. zu weniger als 10 %, insbesondere weniger als 5 % Ruthenium-Partikel und/oder Agglo- merate von Rutheniumpartikeln mit Durchmessern oberhalb 10 nm. Durch die Verwendung halogenfreier Rutheniumprekursoren und Lösungsmittel bei der Herstellung liegt der Chlorgehalt der erfindungsgemäß eingesetzten Katalysatoren zudem unterhalb 0,05 Gew.-% (< 500 ppm), bezogen auf das Gesamtgewicht des Katalysators.Electron microscopic investigations (TEM) of the catalysts have shown that the ruthenium on the support material is in atomically dispersed form and / or in the form of ruthenium particles which are almost exclusively, i.e. more than 90%, preferably more than 95%, based on the number of visible particles, are present as isolated particles with diameters below 10 nm, in particular below 7 nm. In other words, the catalyst contains essentially none, i.e. less than 10%, in particular less than 5%, of ruthenium particles and / or agglomerates of ruthenium particles with diameters above 10 nm. The use of halogen-free ruthenium precursors and solvents in the production also means that the chlorine content of the catalysts used according to the invention is below 0.05 % By weight (<500 ppm), based on the total weight of the catalyst.
Ein wesentlicher Bestandteil der im erfindungsgemäßen Verfahren eingesetzten Katalysatoren ist das Trägermaterial auf Basis von amorphem Siliziumdioxid. Unter dem Begriff amorph versteht man in diesem Zusammenhang, dass der Anteil kristalliner Siliziumdioxid-Phasen weniger als 10 % des Trägermaterials ausmacht. Die zur Herstellung der Katalysatoren verwendeten Trägermaterialien können allerdings Über- Strukturen aufweisen, die durch regelmäßige Anordnung von Poren im Trägermaterial gebildet werden.An essential component of the catalysts used in the process according to the invention is the support material based on amorphous silicon dioxide. In this context, the term amorphous means that the proportion of crystalline silicon dioxide phases makes up less than 10% of the carrier material. However, the support materials used to produce the catalysts can have superstructures which are formed by regularly arranging pores in the support material.
Als Trägermaterialien kommen grundsätzlich alle amorphen Siliziumdioxid-Typen in Betracht, die wenigstens zu 90 Gew.-% aus Siliziumdioxid bestehen, wobei die verbleibenden 10 Gew.-%, vorzugsweise nicht mehr als 5 Gew.-% des Trägermaterials auch ein anderes oxidisches Material sein können, z.B. MgO, CaO, TiO2, ZrO2, Fe2O3 oder Alkalimetalloxid. Es versteht sich von selbst, dass das eingesetzte Trägermaterial ebenfalls halogenfrei ist, d. h. der Halogengehalt beträgt weniger als 500 ppm. Vor- zugsweise enthält das Trägermaterial nicht mehr als 1 Gew.-% und insbesondere nicht mehr als 0,5 Gew.-% und insbesondere keine nachweisbaren Mengen (< 500 ppm) an Aluminiumoxid, gerechnet als AI2O3. In einer bevorzugten Ausführungsform verwendet man Trägermaterialien, die weniger als 500 ppm Fe2O3 enthalten. Der Anteil an Alkalimetalloxid resultiert in der Regel aus der Herstellung des Trägermaterials und kann bis zu 2 Gew.-% betragen. Häufig beträgt er weniger als 1 Gew.-%. Geeignet sind auch Alkalimetalloxid-freie Träger (< 0,1 Gew.-%). Der Anteil an MgO, CaO, TiO2 bzw. an ZrO2 kann bis zu 10 Gew.-% des Trägermaterials ausmachen und beträgt vorzugsweise nicht mehr als 5 Gew.-%. Geeignet sind aber auch Trägermaterialien, die keine nachweisbaren Mengen dieser Metalloxide enthalten (< 0,1 Gew.-%).Fundamentally, all amorphous silicon dioxide types which at least 90% by weight consist of silicon dioxide come into consideration as carrier materials, the remaining 10% by weight, preferably not more than 5% by weight, of the carrier material can also be another oxidic material, for example MgO, CaO, TiO 2 , ZrO 2 , Fe 2 O 3 or alkali metal oxide. It goes without saying that the carrier material used is also halogen-free, ie the halogen content is less than 500 ppm. The carrier material preferably contains no more than 1% by weight and in particular no more than 0.5% by weight and in particular no detectable amounts (<500 ppm) of aluminum oxide, calculated as Al 2 O 3 . In a preferred embodiment, support materials are used which contain less than 500 ppm Fe 2 O 3 . The proportion of alkali metal oxide generally results from the production of the carrier material and can be up to 2% by weight. It is often less than 1% by weight. Alkali metal oxide-free carriers (<0.1% by weight) are also suitable. The proportion of MgO, CaO, TiO 2 or ZrO 2 can make up to 10% by weight of the carrier material and is preferably not more than 5% by weight. However, carrier materials which do not contain any detectable amounts of these metal oxides (<0.1% by weight) are also suitable.
Bevorzugt sind Trägermaterialien, die eine spezifische Oberfläche im Bereich von 50 bis 700 m2/g, insbesondere im Bereich von 80 bis 600 m2/g und speziell im Bereich von 100 bis 600 m2/g aufweisen (BET-Oberfläche nach DIN 66131). Unter den pulver- förmigen Trägermaterialien sind insbesondere solche bevorzugt, deren spezifische (BET) Oberfläche im Bereich von 200 bis 600 m2/g liegt. Bei Trägermaterial in Form von Formkörpern liegt die spezifische Oberfläche insbesondere im Bereich von 100 bis 300 m2/g.Preference is given to carrier materials which have a specific surface area in the range from 50 to 700 m 2 / g, in particular in the range from 80 to 600 m 2 / g and especially in the range from 100 to 600 m 2 / g (BET surface area in accordance with DIN 66131 ). Among the powdered carrier materials, those are particularly preferred whose specific (BET) surface area is in the range from 200 to 600 m 2 / g. In the case of carrier material in the form of shaped bodies, the specific surface area is in particular in the range from 100 to 300 m 2 / g.
Geeignete amorphe Trägermaterialien auf Basis von Siliziumdioxid sind dem Fach- mann geläufig und kommerziell erhältlich (siehe z.B. O.W. Flörke, „Silica" in Ullmann's Encyclopedia of Industrial Chemistry 5th ed. on CD-ROM). Sie können sowohl natürlichen Ursprungs als auch künstlich hergestellt worden sein. Beispiele für geeignete amorphe Trägermaterialien auf Basis von Siliziumdioxid sind Kieselgur, Kieselgele, pyrogene Kieselsäure und Fällungskieselsäure. In einer bevorzugten Ausführungs- form der Erfindung enthalten die Katalysatoren Kieselgele als Trägermaterialien.Suitable amorphous carrier materials based on silicon dioxide are familiar to the person skilled in the art and are commercially available (see, for example, OW Flörke, “Silica” in Ullmann's Encyclopedia of Industrial Chemistry 5th ed. On CD-ROM). They can be produced both naturally and artificially Examples of suitable amorphous support materials based on silicon dioxide are diatomaceous earth, silica gels, pyrogenic silica and precipitated silica. In a preferred embodiment of the invention, the catalysts contain silica gels as support materials.
Je nach Ausgestaltung des erfindungsgemäßen Verfahrens kann das Trägermaterial unterschiedliche Gestalt aufweisen. Sofern das Verfahren als Suspensionsverfahren ausgestaltet ist, wird man zur Herstellung der erfindungsgemäßen Katalysatoren übli- cherweise das Trägermaterial in Form eines feinteiligen Pulvers einsetzen. Die Teilchengröße der Pulverteilchen liegt vorzugsweise im Bereich von 1 bis 200 μm und insbesondere im Bereich von 10 bis 100 μm. Bei Einsatz des Katalysators in Katalysatorfestbetten verwendet man üblicherweise Formkörper aus dem Trägermaterial, die z.B. durch Extrudieren, Strangpressen oder Tablettieren erhältlich sind und die z.B. die Form von Kugeln, Tabletten, Zylindern, Strängen, Ringen bzw. Hohlzylindem, Sternen und dergleichen aufweisen können. Die Abmessungen dieser Formkörper bewegen sich üblicherweise im Bereich von 1 mm bis 25 mm. Häufig werden Katalysatorstränge mit Strangdurchmessern von 2 bis 5 mm und Stranglängen von 2 bis 25 mm ein- gesetzt.Depending on the design of the method according to the invention, the carrier material can have different shapes. If the process is designed as a suspension process, it is usual to prepare the catalysts according to the invention. usually use the carrier material in the form of a finely divided powder. The particle size of the powder particles is preferably in the range from 1 to 200 μm and in particular in the range from 10 to 100 μm. When the catalyst is used in fixed catalyst beds, shaped bodies made of the carrier material are usually used, which can be obtained, for example, by extrusion, extrusion or tableting and which can have, for example, the shape of spheres, tablets, cylinders, strands, rings or hollow cylinders, stars and the like. The dimensions of these moldings usually range from 1 mm to 25 mm. Catalyst strands with strand diameters of 2 to 5 mm and strand lengths of 2 to 25 mm are often used.
Der Gehalt an Ruthenium in den Katalysatoren kann über einen breiten Bereich variiert werden. In der Regel wird er wenigstens 0,1 Gew.-%, vorzugsweise wenigstens 0,2 Gew.-% betragen und häufig einen Wert von 10 Gew.-%, jeweils bezogen auf das Gewicht des Trägermaterials, nicht überschreiten. Vorzugsweise liegt der Gehalt an Ruthenium im Bereich von 0,2 bis 7 Gew.-% und insbesondere im Bereich von 0,4 bis 5 Gew.-%.The content of ruthenium in the catalysts can be varied over a wide range. As a rule, it will be at least 0.1% by weight, preferably at least 0.2% by weight, and often will not exceed a value of 10% by weight, in each case based on the weight of the carrier material. The ruthenium content is preferably in the range from 0.2 to 7% by weight and in particular in the range from 0.4 to 5% by weight.
Die Herstellung der im erfindungsgemäßen Verfahren eingesetzten Ruthenium-Kataly- satoren erfolgt in der Regel dadurch, dass man zunächst das Trägermaterial mit einer halogenfreien wässrigen Lösung einer niedermolekularen Rutheniumverbindung, im Folgenden als (Ruthenium)prekursor bezeichnet, in einer Weise behandelt, dass die gewünschte Menge an Ruthenium vom Trägermaterial aufgenommen wird. Dieser Schritt wird im Folgenden auch als Tränken bezeichnet. Anschließend wird der so behandelte Träger bei den oben angegebenen Temperaturen getrocknet. Gegebenenfalls wird dann der so erhaltene Feststoff erneut mit der wässrigen Lösung des Ruthe- niumprekursors behandelt und erneut getrocknet. Dieser Vorgang wird so oft wiederholt, bis die vom Trägermaterial aufgenommene Menge an Rutheniumverbindung dem gewünschten Rutheniumgehalt im Katalysator entspricht.The ruthenium catalysts used in the process according to the invention are generally prepared by first treating the support material with a halogen-free aqueous solution of a low molecular weight ruthenium compound, hereinafter referred to as (ruthenium) precursor, in such a way that the desired amount of ruthenium is absorbed by the carrier material. This step is also referred to below as watering. The carrier thus treated is then dried at the temperatures indicated above. If necessary, the solid thus obtained is then treated again with the aqueous solution of the ruthenium precursor and dried again. This process is repeated until the amount of ruthenium compound taken up by the support material corresponds to the desired ruthenium content in the catalyst.
Das Behandeln bzw. Tränken des Trägermaterials kann in unterschiedlicher Weise erfolgen und richtet sich in bekannter Weise nach der Gestalt des Trägermaterials. Beispielsweise kann man das Trägermaterial mit der Prekursor-Lösung besprühen oder spülen oder das Trägermaterial in der Prekursor-Lösung suspendieren. Bei- spielsweise kann man das Trägermaterial in der wässrigen Lösung des Ruthenium- prekursors suspendieren und nach einer gewissen Zeit vom wässrigen Überstand abfiltrieren. Über die aufgenommene Flüssigkeitsmenge und die Ruthenium-Konzentration der Lösung kann dann der Rutheniumgehalt des Katalysators in einfacher Weise gesteuert werden. Das Tränken des Trägermaterials kann beispielsweise auch dadurch erfolgen, dass man den Träger mit einer definierten Menge der wässrigen Lösung des Rutheniumprekursors behandelt, die der maximalen Flüssigkeitsmenge entspricht, die das Trägermaterial aufnehmen kann. Zu diesem Zweck kann man beispielsweise das Trägermaterial mit der Flüssigkeitsmenge besprühen. Geeignete Apparaturen hierfür sind die zum Vermengen von Flüssigkeiten mit Feststoffen üblicherweise verwendeten Apparate (siehe Vauck/Müller, Grundoperationen chemischer Verfahrenstechnik, 10. Auflage, Deutscher Verlag für Grundstoffindustrie, 1994, S.405 ff.) beispielsweise Taumeltrockner, Tränktrommeln, Trommelmischer, Schaufelmischer und dergleichen. Monolithische Träger werden üblicherweise mit den wässrigen Lö- sungen des Rutheniumprekursors gespült.The treatment or impregnation of the carrier material can take place in different ways and depends in a known manner on the shape of the carrier material. For example, the carrier material can be sprayed or rinsed with the precursor solution or the carrier material can be suspended in the precursor solution. examples for example, the carrier material can be suspended in the aqueous solution of the ruthenium precursor and filtered off from the aqueous supernatant after a certain time. The ruthenium content of the catalyst can then be controlled in a simple manner via the amount of liquid taken up and the ruthenium concentration of the solution. The support material can also be impregnated, for example, by treating the support with a defined amount of the aqueous solution of the ruthenium precursor which corresponds to the maximum amount of liquid which the support material can hold. For this purpose, the liquid can be sprayed onto the carrier material, for example. Suitable apparatus for this are the apparatuses usually used for mixing liquids with solids (see Vauck / Müller, Basic Operations of Chemical Process Engineering, 10th edition, German Publisher for Basic Industry, 1994, pp. 405 ff.), For example tumble dryers, water drums, drum mixers, paddle mixers and like. Monolithic supports are usually rinsed with the aqueous solutions of the ruthenium precursor.
Die zum Tränken eingesetzten wässrigen Lösungen sind erfindungsgemäß halogenfrei, d.h. sie enthalten kein oder weniger als 100 ppm Halogen. Als Rutheniumprekur- soren werden daher nur solche Rutheniumverbindungen eingesetzt, die kein chemisch gebundenes Halogen enthalten und die in dem wässrigen Lösungsmittel hinreichend löslich sind. Hierzu zählen z.B. Ruthenium(lll)nitrosylnitrat (Ru(NO)(NO3)3), Rutheni- um(lll)acetat sowie die Alkalimetallruthenate(IV) wie Natrium- und Kaliumruthenat(IV).According to the invention, the aqueous solutions used for impregnation are halogen-free, ie they contain no or less than 100 ppm halogen. Therefore, only ruthenium compounds that do not contain chemically bound halogen and that are sufficiently soluble in the aqueous solvent are used as ruthenium precursors. These include, for example, ruthenium (III) nitrosyl nitrate (Ru (NO) (NO 3 ) 3 ), ruthenium (III) acetate and the alkali metal ruthenates (IV) such as sodium and potassium ruthenate (IV).
Der Begriff wässrig bezeichnet hier Wasser sowie Mischungen von Wasser mit bis zu 50 Vol.-%, vorzugsweise nicht mehr als 30 Vol.-% und insbesondere nicht mehr als 10 Vol.-% eines oder mehrerer mit Wasser mischbarer organischer Lösungsmittel, z.B. Mischungen von Wasser mit Cι-C -Alkanolen wie Methanol, Ethanol, n- oder Isopropanol. Häufig setzt man Wasser als alleiniges Lösungsmittel ein. Das wässrige Lösungsmittel wird häufig zusätzlich wenigstens eine halogenfreie Säure, z.B. Sal- petersäure, Schwefelsäure, Phosphorsäure oder Essigsäure, vorzugsweise eine halogenfreie Mineralsäure, zur Stabilisierung des Rutheniumprekursors in der Lösung enthalten. In vielen Fällen setzt man daher eine mit Wasser verdünnte, halogenfreie Mineralsäure, z. B. verdünnte bis halbkonzentrierte Salpetersäure als Lösungsmittel für den Rutheniumprekursor ein. Die Konzentration des Rutheniumprekursors in den wässri- gen Lösungen richtet sich naturgemäss nach der aufzubringenden Menge an Rutheni- umprekursor und der Aufnahmekapazität des Trägermaterials für die wässrige Lösung und liegt in der Regel im Bereich von 0,1 bis 20 Gew.-%.The term aqueous here denotes water and mixtures of water with up to 50% by volume, preferably not more than 30% by volume and in particular not more than 10% by volume of one or more water-miscible organic solvents, for example mixtures of Water with -CC alkanols such as methanol, ethanol, n- or isopropanol. Water is often used as the sole solvent. The aqueous solvent will often 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, in order to stabilize the ruthenium precursor in the solution. In many cases, therefore, a halogen-free mineral acid, e.g. B. dilute to semi-concentrated nitric acid as a solvent for the ruthenium precursor. The concentration of the ruthenium precursor in the aqueous solutions naturally depends on the amount of ruthenium precursor to be applied and the absorption capacity of the carrier material for the aqueous solution and is generally in the range from 0.1 to 20% by weight.
Das Trocknen kann nach den üblichen Verfahren der Feststofftrocknung unter Einhaltung der obengenannten Temperaturen erfolgen. Die Einhaltung der erfindungsgemäßen Obergrenze der Trocknungstemperaturen ist für die Qualität, d.h. die Aktivität des Katalysators wichtig. Ein Überschreiten der oben angegebenen Trocknungstemperaturen führt zu einem deutlichen Verlust an Aktivität. Ein Kalzinieren des Trä- gers bei höheren Temperaturen, z.B. oberhalb 300°C oder gar 400°C, wie es im Stand der Technik vorgeschlagen wird, ist nicht nur überflüssig sondern wirkt sich auch nachteilig auf die Aktivität des Katalysators aus.Drying can be carried out using the customary methods of drying solids while maintaining the above-mentioned temperatures. Compliance with the upper limit of the drying temperatures according to the invention is important for the quality, i.e. the activity of the catalyst is important. Exceeding the drying temperatures given above leads to a significant loss of activity. Calcining the support at higher temperatures, e.g. Above 300 ° C or even 400 ° C, as proposed in the prior art, is not only superfluous but also has a disadvantageous effect on the activity of the catalyst.
Die Trocknung des in mit dem Rutheniumprekursors getränkten Feststoff erfolgt übli- cherweise unter Normaldruck wobei zur Förderung der Trocknung auch ein verminderter Druck angewendet werden kann. Häufig wird man zur Förderung der Trocknung einen Gasstrom über bzw. durch das zu trocknende Gut leiten, z.B. Luft oder Stickstoff.The drying of the solid impregnated with the ruthenium precursor usually takes place under normal pressure. A reduced pressure can also be used to promote the drying. Often, to promote drying, a gas stream will be passed over or through the material to be dried, e.g. Air or nitrogen.
Die Trocknungsdauer hängt naturgemäss von dem gewünschten Grad der Trocknung und der Trocknungstemperatur ab und liegt in der Regel im Bereich von 2 h bis 30 h, vorzugsweise im Bereich von 4 h bis 15 h.The drying time naturally depends on the desired degree of drying and the drying temperature and is generally in the range from 2 h to 30 h, preferably in the range from 4 h to 15 h.
Vorzugsweise führt man die Trocknung des behandelten Trägermaterials soweit, dass der Gehalt an Wasser bzw. an flüchtigen Lösungsmittelbestandteilen vor der Reduktion ii) weniger als 5 Gew.-%, insbesondere nicht mehr als 2 Gew.-% und besonders bevorzugt nicht mehr als 1 Gew.-%, bezogen auf das Gesamtgewicht des Feststoffs ausmacht. Die angegebenen Gewichtsanteile beziehen sich auf den Gewichtsverlust des Feststoffs, bestimmt bei einer Temperatur von 300 °C, einem Druck von 1 bar und einer Dauer von 10 min. Auf diese Weise kann die Aktivität der erfindungsgemäßen Katalysatoren weiter gesteigert werden.The treatment of the treated carrier material is preferably carried out to such an extent that the content of water or volatile solvent components before the reduction ii) is less than 5% by weight, in particular not more than 2% by weight and particularly preferably not more than 1% by weight .-%, based on the total weight of the solid. The stated weight fractions relate to the weight loss of the solid, determined at a temperature of 300 ° C., a pressure of 1 bar and a duration of 10 min. In this way, the activity of the catalysts according to the invention can be increased further.
Vorzugsweise erfolgt das Trocknen unter Bewegen des mit der Prekursor-Lösung behandelten Feststoffs, beispielsweise durch Trocknen des Feststoffs in einem Dreh- rohrofen oder einem Drehkugelofen. Auf diese Weise kann die Aktivität der erfindungsgemäßen Katalysatoren weiter gesteigert werden.Drying is preferably carried out by moving the solid treated with the precursor solution, for example by drying the solid in a rotary motion. tube furnace or a rotary kiln. In this way, the activity of the catalysts according to the invention can be increased further.
Die Überführung des nach dem Trocknen erhaltenen Feststoffs in seine katalytisch aktive Form erfolgt erfindungsgemäß durch Hydrieren des Feststoffs bei den oben angegebenen Temperaturen in an sich bekannter Weise.According to the invention, the solid obtained after drying is converted into its catalytically active form by hydrogenating the solid at the temperatures indicated above in a manner known per se.
Zu diesem Zweck bringt man das Trägermaterial bei den oben angegebenen Temperaturen mit Wasserstoff oder einer Mischung aus Wasserstoff und einem Inertgas in Kontakt. Der Wasserstoffpartialdruck ist für das Ergebnis der Reduktion von untergeordneter Bedeutung und kann im Bereich von 0,2 bar bis 1 ,5 bar variiert werden. Häufig erfolgt die Hydrierung des Katalysatormaterials bei Wasserstoffnormaldruck im Wasserstoff ström. Vorzugsweise erfolgt das Hydrieren unter Bewegen des in i) erhaltenen Feststoffs, beispielsweise durch Hydrieren des Feststoffs in einem Drehrohr- ofen oder einem Drehkugelofen. Auf diese Weise kann die Aktivität der erfindungsgemäßen Katalysatoren weiter gesteigert werden.For this purpose, the carrier material is brought into contact with hydrogen or a mixture of hydrogen and an inert gas at the temperatures indicated above. The hydrogen partial pressure is of minor importance for the result of the reduction and can be varied in the range from 0.2 bar to 1.5 bar. The hydrogenation of the catalyst material often takes place at normal hydrogen pressure in the hydrogen stream. The hydrogenation is preferably carried out by moving the solid obtained in i), for example by hydrogenating the solid in a rotary tubular furnace or a rotary ball furnace. In this way, the activity of the catalysts according to the invention can be increased further.
Im Anschluss an die Hydrierung kann der Katalysator zur Verbesserung der Handhabbarkeit in bekannter Weise passiviert werden, z.B. indem man den Katalysator kurz- fristig mit einem Sauerstoff-haltigen Gas, z.B. Luft, vorzugsweise jedoch mit einer 1 bis 10 Vol.-% Sauerstoff enthaltenden Inertgasmischung behandelt.Following the hydrogenation, the catalyst can be passivated in a known manner to improve handling, e.g. by briefly using the catalyst with an oxygen-containing gas, e.g. Air, but preferably treated with an inert gas mixture containing 1 to 10% by volume of oxygen.
Im erfindungsgemässen Verfahren erfolgt die Hydrierung des Saccharids vorzugsweise durch Hydrieren einer wässrigen Lösung des jeweiligen Saccharids bzw. im Falle des Invertzuckers als Ausgangsmaterial, der Saccharid-Mischung. Der Begriff „wässrig" ist hierbei in der oben definierten Weise zu verstehen. Zweckmäßigerweise wird Wasser als alleiniges Lösungsmittel verwendet, das gegebenenfalls geringe Mengen einer vorzugsweise halogenfreien Säure zur Einstellung des pH-Wertes enthält. Insbesondere setzt man das Monosaccharid als wässrige Lösung ein, die einen pH-Wert im Bereich von 4 bis 10, und speziell im Bereich von 5 bis 7 aufweist.In the process according to the invention, the saccharide is preferably hydrogenated by hydrogenating an aqueous solution of the respective saccharide or, in the case of invert sugar, as the starting material, the saccharide mixture. The term "aqueous" is to be understood here in the manner defined above. Water is expediently used as the sole solvent, which may contain small amounts of a preferably halogen-free acid for adjusting the pH. In particular, the monosaccharide is used as an aqueous solution which has a pH in the range from 4 to 10, and especially in the range from 5 to 7.
Die Konzentration an Saccharid in der flüssigen Phase kann grundsätzlich frei gewählt werden und liegt häufig im Bereich von 10 bis 80 Gew.-% und vorzugsweise im Bereich von 15 bis 50 Gew.-%, bezogen auf das Gesamtgewicht der Lösung. Die Saccharidlösung wird vor der Hydrierung, d.h. bevor sie mit dem Rutheniumkatalysator in Kontakt kommt, mit dem Trägermaterial in Kontakt gebracht. Dies dient dazu, daß die Saccharidlösung an Trägermaterial, d.h. vor allem an Siliziumdioxid gesättigt wird und dadurch weniger Trägermaterial aus dem Katalysator herauslöst, was sich vorteilhaft auf die Lebensdauer (Standzeit) des Katalysators auswirkt. Das Inkontakt- bringen der Saccharidlösung mit dem Trägermaterial kann auf mehrere Arten erfolgen, beispielsweise durch Suspendieren des pulverförmigen Trägermaterials in der Saccharidlösung oder durch Überleiten der Saccharidlösung durch Formkörper aus Träger- material.The concentration of saccharide in the liquid phase can in principle be chosen freely and is frequently 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 saccharide solution is brought into contact with the support material before the hydrogenation, ie before it comes into contact with the ruthenium catalyst. The purpose of this is that the saccharide solution becomes saturated on the support material, ie above all on silicon dioxide, and as a result less support material is released from the catalyst, which has an advantageous effect on the service life (service life) of the catalyst. The saccharide solution can be brought into contact with the carrier material in a number of ways, for example by suspending the powdery carrier material in the saccharide solution or by passing the saccharide solution through shaped bodies made of carrier material.
Das Überleiten der Saccharidlösung durch Silica-Stränge ist eine besonders bevorzugte Ausführungsform des erfindungsgemäßen Verfahrens, insbesondere wenn die Lösung unter Druck durch mit Silica-Stränglingen gefüllte Rohre gepresst wird.The passage of the saccharide solution through silica strands is a particularly preferred embodiment of the method according to the invention, in particular if the solution is pressed under pressure through tubes filled with silica strands.
Ein weiterer Vorteil des erfindungsgemäßen Verfahrens ergibt sich dadurch, dass beim Durchpressen der Saccharidlösung durch die Silica-Stränge evt. noch in der Saccharidlösung vorhandene oligomere Zucker zurückgehalten werden und somit die Reinheit an gebildetem Zuckeralkohol erhöht wird. Dies ist insbesondere bei der Verwendung von Stärkehydrolysaten als Saccharide zu beobachten.Another advantage of the method according to the invention results from the fact that when the saccharide solution is pressed through the silica strands, any oligomeric sugars still present in the saccharide solution are retained and the purity of the sugar alcohol formed is thus increased. This can be observed particularly when using starch hydrolyzates as saccharides.
Die eigentliche Hydrierung erfolgt üblicherweise in Analogie zu den bekannten Hydrierverfahren für die Herstellung von Zuckeralkoholen, wie sie im eingangs genannten Stand der Technik beschrieben werden. Hierzu wird die flüssige, das Saccharid enthal- tende Phase mit dem Katalysator in Gegenwart von Wasserstoff in Kontakt gebracht. Der Katalysator kann dabei sowohl in der flüssigen Phase suspendiert werden (Suspensionsfahrweise) oder man führt die flüssige Phase über ein Katalysator-Fließbett (Fließbett-Fahrweise) oder ein Katalysator-Festbett (Festbettfahrweise). Die Hydrierung kann sowohl kontinuierlich als auch diskontinuierlich ausgestaltet werden. Vor- zugsweise führt man das erfindungsgemäße Verfahren in Rieselreaktoren nach der Festbettfahrweise durch. Der Wasserstoff kann dabei sowohl im Gleichstrom mit der Lösung des zu hydrierenden Edukts als auch im Gegenstrom über den Katalysator geleitet werden. Geeignete Apparaturen zur Durchführung einer Hydrierung nach der Suspensionsfahrweise als auch zur Hydrierung am Katalysatorfestbett sind aus dem Stand der Technik bekannt, z.B. aus Ulimanns Enzyklopädie der Technischen Chemie, 4. Auflage, Band 13, S. 135 ff. sowie aus P. N. Rylander, „Hydrogenation and Dehydrogena- tion" in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. on CD-ROM bekannt.The actual hydrogenation is usually carried out in analogy to the known hydrogenation processes for the production of sugar alcohols, as described in the prior art mentioned at the beginning. For this purpose, the liquid phase containing the saccharide is brought into contact with the catalyst in the presence of hydrogen. The catalyst can either be suspended in the liquid phase (suspension mode) or the liquid phase is passed over a fluidized catalyst bed (fluidized bed mode) or a fixed catalyst bed (fixed bed mode). The hydrogenation can be carried out either continuously or batchwise. The process according to the invention is preferably carried out in trickle-bed reactors according to the fixed bed procedure. The hydrogen can be passed both in cocurrent with the solution of the starting material to be hydrogenated and in countercurrent over the catalyst. Suitable apparatus for carrying out a hydrogenation according to the suspension procedure and also for hydrogenation on a fixed catalyst bed are known from the prior art, for example from Ulimann's Encyclopedia of Industrial Chemistry, 4th edition, volume 13, p. 135 ff. And from PN Rylander, “Hydrogenation and Dehydrogenation "in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. on CD-ROM.
In der Regel führt man die Hydrierung bei erhöhtem Wasserstoffdruck, z.B. bei einem Wasserstoff partialdruck von wenigstens 10 bar, vorzugsweise wenigstens 20 bar und insbesondere wenigstens 40 bar durch. In der Regel wird der Wasserstoffpartialdruck einen Wert von 500 bar, insbesondere 350 bar nicht überschreiten. Besonders bevorzugt liegt der Wasserstoffpartialdruck im Bereich von 40 bis 200 bar. Die Reaktionstemperaturen betragen in der Regel wenigstens 40°C und werden häufig einen Wert von 250°C nicht überschreiten. Insbesondere führt man das Hydrierverfahren bei Temperaturen im Bereich von 80 bis 150°C durch.As a rule, the hydrogenation is carried out at elevated hydrogen pressure, e.g. at a hydrogen partial pressure of at least 10 bar, preferably at least 20 bar and in particular at least 40 bar. As a rule, the hydrogen partial pressure will not exceed a value of 500 bar, in particular 350 bar. The hydrogen partial pressure is particularly preferably in the range from 40 to 200 bar. The reaction temperatures are usually at least 40 ° C and will often not exceed 250 ° C. In particular, the hydrogenation process is carried out at temperatures in the range from 80 to 150 ° C.
Aufgrund der hohen Katalysatoraktivität benötigt man vergleichsweise geringe Mengen an Katalysator bezogen auf das eingesetzte Edukt. So wird man bei der diskontinuierl- chen Suspensionsfahrweise in der Regel weniger als 1 mol-%, z.B. 10"3 mol-% bis 0,5 moI-% Ruthenium, bezogen auf 1 mol Zucker einsetzen. Bei kontinuierlicher Aus- gestaltung des Hydrierverfahrens wird man üblicherweise das zu hydrierende Edukt in einer Menge von 0,05 bis 2 kg/(l(Katalysator)*h), insbesondere in einer Menge von 0,07 bis 0,7 kg/(l(Katalysator)*h) über den Katalysator führen.Due to the high catalyst activity, comparatively small amounts of catalyst are required, based on the starting material used. In the discontinuous suspension procedure, less than 1 mol%, for example 10 -3 mol% to 0.5 mol% ruthenium, based on 1 mol of sugar, is generally used. If the hydrogenation process is carried out continuously, usually the starting material to be hydrogenated in an amount of 0.05 to 2 kg / (l (catalyst) * h), in particular in an amount of 0.07 to 0.7 kg / (l (catalyst) * h) over the Lead catalyst.
Im erfindungsgemässen Verfahren fällt eine Lösung des Zuckeralkohols in dem jeweils eingesetzten wässrigen Lösungsmittel an, aus dem es nach bekannten Verfahren gewonnen werden kann (siehe H. Schiweck et al. „Sugar Alcohols" in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. on CD-ROM). Bei den bevorzugt erhaltenen wässrigen Reaktionsmischungen kann man den Zuckeralkohol beispielsweise durch Eindampfen mit nachfolgender Kristallisation (DE-A 2350690, EP-A 32288, EP-A 330352) oder Sprühtrocknen (DK 133603, DD 277176) gewinnen. Falls erforderlich wird zuvor der Katalysator nach üblichen Verfahren abgetrennt und die Reaktionslösung einer Entfärbung mit geeigneten Filterhilfsmitteln und/oder einer Behandlung mit lonentauschem zur Entfernung von Metallionen, Gluconaten oder anderen organischen Säuren unterworfen. Bei Verwendung von Invertzucker oder Fruktose wird neben Sorbit naturgemäß auch noch Mannit gebildet. Falls reine Zuckeralkohole gewünscht werden, kann aus den dabei erhaltenen Reaktionsmischungen beispielsweise Sorbit durch selektive Kristalli- sation gewonnen werden.In the process according to the invention, a solution of the sugar alcohol in the aqueous solvent used is obtained, from which it can be obtained by known processes (see H. Schiweck et al. "Sugar Alcohols" in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. On CD- In the aqueous reaction mixtures which are preferably obtained, the sugar alcohol can be obtained, for example, by evaporation with subsequent crystallization (DE-A 2350690, EP-A 32288, EP-A 330352) or spray drying (DK 133603, DD 277176) the catalyst is separated off by customary processes and the reaction solution is subjected to decolorization with suitable filter aids and / or treatment with ion exchange to remove metal ions, gluconates or other organic acids. When using invert sugar or fructose, mannitol is naturally formed in addition to sorbitol. If pure sugar alcohols are desired, sorbitol, for example, can be obtained from the reaction mixtures obtained in this way by selective crystallization.
Das erfindunggemäße Verfahren zeichnet sich zum einen durch die erreichten hohen Raum-Zeit-Ausbeuten und bei Verwendung von Glucose als Ausgangsmaterial auch durch eine hohe Produktselektivität aus. Zudem zeichnen sich das erfindungsgemäße Verfahren durch besonders hohe Standzeiten der Rutheniumkatalysatoren aus, wodurch das Verfahren wirtschaftlich besonders attraktiv wird.The process according to the invention is distinguished on the one hand by the high space-time yields achieved and, when using glucose as the starting material, also by a high product selectivity. In addition, the process according to the invention is distinguished by a particularly long service life of the ruthenium catalysts, which makes the process particularly economically attractive.
Selbstverständlich können die in diesem Verfahren eingesetzten Katalysatoren bei nachlassender Aktivität nach den für Edelmetallkatalysatoren wie Rutheniumkataly- satoren üblichen, dem Fachmann bekannten Methoden regeneriert werden. Hier sind z.B. die Behandlung des Katalysators mit Sauerstoff wie in der BE 882279 beschrieben, die Behandlung mit verdünnten, halogenfreien Mineralsäuren, wie in der US 4,072,628 beschrieben, oder die Behandlung mit Wasserstoffperoxid, z.B. in Form wässriger Lösungen mit einem Gehalt von 0,1 bis 35 Gew.-%, oder die Behandlung mit anderen oxidierenden Substanzen, vorzugsweise in Form halogenfreier Lösungen zu nennen. Üblicherweise wird der Katalysator nach der Reaktivierung und vor dem erneuten Einsatz mit einem Lösungsmittel, z.B. Wasser, spült.If the activity decreases, the catalysts used in this process can of course be regenerated according to the methods known to those skilled in the art for noble metal catalysts such as ruthenium catalysts. Here are e.g. treatment of the catalyst with oxygen as described in BE 882279, treatment with dilute, halogen-free mineral acids as described in US 4,072,628, or treatment with hydrogen peroxide, e.g. in the form of aqueous solutions with a content of 0.1 to 35% by weight, or the treatment with other oxidizing substances, preferably in the form of halogen-free solutions. Typically, the catalyst is reactivated with a solvent, e.g. Water, rinse.
Die folgenden Beispiele dienen der nähren Erläuterung der Erfindung:The following examples serve to illustrate the invention:
I Herstellung der KatalysatorenI Preparation of the catalysts
1. Vorschrift A: Pulverförmiger, halogenfreier Katalysator, nicht kalziniert.1. Regulation A: Powdery, halogen-free catalyst, not calcined.
Eine definierte Menge des jeweiligen Trägermaterials wurde mit der maximalen Menge einer Lösung von Ruthenium(III)nitrosylnitrat in Wasser getränkt, die vom jeweiligen Trägermaterial aufgenommen werden konnte. Die maximale vom jeweiligen Trägermaterial aufgenommene Menge war zuvor anhand einer authentischen Probe be- stimmt worden. Die Konzentration der Lösung wurde jeweils so bemessen, dass die gewünschte Konzentration an Ruthenium im Trägermaterial resultierte.A defined amount of the respective carrier material was impregnated with the maximum amount of a solution of ruthenium (III) nitrosyl nitrate in water that could be absorbed by the respective carrier material. The maximum amount absorbed by the respective carrier material was previously based on an authentic sample. been agreed. The concentration of the solution was measured such that the desired concentration of ruthenium in the support material resulted.
Anschliessend wurde der so erhaltene Feststoff 13 h bei 120°C in einem Drehkugel- ofen getrocknet. Der Restwassergehalt lag unter 1 Gew.-%.The solid obtained in this way was then dried in a rotary ball oven at 120 ° C. for 13 h. The residual water content was below 1% by weight.
Der so erhaltene Feststoff wurde in einem Drehkugelofen 4 h bei 300°C im Wasserstoffstrom bei Normaldruck reduziert. Nach Abkühlen und Inertisieren mit Stickstoff wurde der Katalysator durch Überleiten von 5 Vol.-% Sauerstoff in Stickstoff über einen Zeitraum von 120 min passiviert.The solid obtained in this way was reduced in a rotary kiln for 4 h 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 into nitrogen over a period of 120 min.
2. Vorschrift B: Pulverförmiger, halogenfreier Katalysator, kalziniert.2. Regulation B: Powdered, halogen-free catalyst, calcined.
Die Herstellung erfolgte analog Vorschrift A, jedoch wurde der nach dem Trocknen erhaltene Feststoff vor der Hydrierung 4 h auf 400°C im Luftstrom erhitzt.The preparation was carried out analogously to regulation A, but the solid obtained after drying was heated to 400 ° C. in an air stream for 4 h before the hydrogenation.
3. Vorschrift C: Pulverförmiger, halogenhaltiger Katalysator, nicht kalziniert.3. Regulation C: Powdery, halogen-containing catalyst, not calcined.
Die Herstellung erfolgte analog Vorschrift A, jedoch wurde anstelle von Rutheni- um(lll)nitrosylnitrat Ruthenium(lll)chlorid eingesetzt.The preparation was carried out analogously to regulation A, but ruthenium (III) chloride was used instead of ruthenium (III) nitrosyl nitrate.
4. Vorschrift D: Strangförmiger, halogenfreier Katalysator, nicht kalziniert.4. Regulation D: strand-like, halogen-free catalyst, not calcined.
Eine definierte Menge von zylindrischen Trägermaterial-Strängen (Durchmesser 4 mm, Länge 3 bis 10 mm) wurde mit der maximalen Menge einer Lösung von Ruthenium- (lll)nitrosylnitrat in Wasser getränkt, die vom jeweiligen Trägermaterial aufgenommen werden konnte. Die maximale vom jeweiligen Trägermaterial aufgenommene Menge war zuvor anhand einer authentischen Probe bestimmt worden. Die Konzentration der Lösung wurde jeweils so bemessen, dass die gewünschte Konzentration an Ruthenium im Trägermaterial resultierte.A defined amount of cylindrical support material strands (diameter 4 mm, length 3 to 10 mm) was impregnated with the maximum amount of a solution of ruthenium (III) nitrosyl nitrate in water which could be taken up by the respective support material. The maximum amount absorbed by the respective carrier material had previously been determined on the basis of an authentic sample. The concentration of the solution was measured such that the desired concentration of ruthenium in the support material resulted.
Anschließend wurden die so erhaltenen, getränkten Stränge 13 h bei 120°C in einem Drehkugelofen getrocknet. Der Restwassergehalt betrug weniger als 1 Gew.-%. Die so erhaltenen, getrockneten Stränge wurden in einem Drehkugelofen 4 h bei 300°C im Wasserstoffstrom bei Normaldruck reduziert. Nach Abkühlen und Inertisieren mit Stickstoff wurde der so erhaltene Katalysator durch Überleiten von 5 Vol.-% Sauerstoff in Stickstoff über einen Zeitraum von 120 min passiviert. »The soaked, soaked strands were then dried for 13 hours at 120 ° C. in a rotary ball oven. The residual water content was less than 1% by weight. The dried strands obtained in this way were reduced in a rotary kiln for 4 h at 300 ° C. in a stream of hydrogen at normal pressure. After cooling and inerting with nitrogen, the catalyst obtained in this way was passivated by passing 5% by volume of oxygen into nitrogen over a period of 120 min. »
5. Vorschrift E: strangförmiger, halogenhaltiger Katalysator, nicht kalziniert.5. Regulation E: strand-like, halogen-containing catalyst, not calcined.
Die Herstellung erfolgte analog Vorschrift D, jedoch wurde anstelle von Rutheni- um(lll)nitrosylnitrat Ruthenium(lll)chlorid eingesetzt.The preparation was carried out analogously to regulation D, but ruthenium (III) chloride was used instead of ruthenium (III) nitrosyl nitrate.
II Kontinuierliche Hydrierung von Maisstärkehydrolysat am Katalysatorfestbett zur Erzeugung von SorbitII Continuous hydrogenation of corn starch hydrolyzate on a fixed catalyst bed to produce sorbitol
Eine Reaktionseinheit bestehend aus einem Hauptreaktor mit Umlauf sowie einem Nachreaktor wird mit dem unter I hergestellten Rutheniumkatalysator beschickt.A reaction unit consisting of a main reactor with circulation and a post-reactor is charged with the ruthenium catalyst prepared under I.
Eine wäßrige Lösung von Maisstärkehydrolysat mit einer Glucosekonzentration von 40% wird unter Druck durch ein mit Silica-Stränglingen gefülltes Rohr gefahren. Anschließend wird diese Lösung in den Hauptreaktor, der eine Kopftemperatur von 80 bis 130°C aufwies, gefahren und danach durch den Nachreaktor, dessen Kopftemperatur an die Sumpftemperatur des Hauptreaktors angeglichen wurde, gefahren. Die Hydrierung erfolgte mit einem Druck von 140 bar.An aqueous solution of corn starch hydrolyzate with a glucose concentration of 40% is passed under pressure through a tube filled with silica strands. This solution is then fed into the main reactor, which had a top temperature of 80 to 130 ° C., and then passed through the post-reactor, the top temperature of which was adjusted to the bottom temperature of the main reactor. The hydrogenation was carried out at a pressure of 140 bar.
Das Verfahren liefert einen Umsatz von 99,8% und eine Selektivität bezogen auf Sorbit von 99,3 %.The process delivers a conversion of 99.8% and a selectivity based on sorbitol of 99.3%.
III Kontinuierliche Hydrierung von Xylose am Katalysatorfestbett zur Erzeugung von XylitolIII Continuous hydrogenation of xylose on a fixed catalyst bed to produce xylitol
Eine Reaktionseinheit bestehend aus einem Hauptreaktor mit Umlauf sowie einem Nachreaktor wird mit dem unter I hergestellten Rutheniumkatalysator beschickt.A reaction unit consisting of a main reactor with circulation and a post-reactor is charged with the ruthenium catalyst prepared under I.
Eine wässrige Lösung von Xylose (Quelle: Aldrich, Reinheit 99,6 %) mit einer Konzentration von 30 % wird unter Druck durch ein mit Silica-Stränglingen gefülltes Rohr gefahren. Anschließend wird diese Lösung in den Hauptreaktor, der eine Kopftemperatur von 80 bis 130°C aufwies, gefahren und danach durch den Nachreaktor, dessen Kopftemperatur an die Sumpftemperatur des Hauptreaktors angeglichen wurde, gefahren. Die Hydrierung erfolgte mit einem Druck von 90 bar.An aqueous solution of xylose (source: Aldrich, purity 99.6%) with a concentration of 30% is passed under pressure through a tube filled with silica strands hazards. This solution is then fed into the main reactor, which had a top temperature of 80 to 130 ° C., and then passed through the post-reactor, the top temperature of which was adjusted to the bottom temperature of the main reactor. The hydrogenation was carried out at a pressure of 90 bar.
Das Verfahren liefert einen Umsatz von 99,8 % und eine Selektivität bezogen auf Xylitol von 98,5 %. The process delivers a conversion of 99.8% and a selectivity based on xylitol of 98.5%.

Claims

Patentansprüche claims
1. Kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen durch katalytische Hydrierung einer wässrigen Lösung eines Saccharids, das bei der Hydrierung den entsprechenden Zuckeralkohol bildet, an einem Ruthenium-1. Continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous solution of a saccharide, which forms the corresponding sugar alcohol on hydrogenation, on a ruthenium
Katalysator, der erhältlich ist durch:Catalyst available through:
i) ein oder mehrfaches Behandeln eines Trägermaterials auf Basis von amorphem Siliziumdioxid mit einer halogenfreien wässrigen Lösung einer niedermolekularen Rutheniumverbindung und anschließendesi) one or more treatment of a carrier material based on amorphous silicon dioxide with a halogen-free aqueous solution of a low molecular weight ruthenium compound and subsequent
Trocknen des behandelten Trägermaterials bei einer Temperatur unterhalb 200°C,Drying the treated carrier material at a temperature below 200 ° C.,
ii) Reduktion des in i) erhaltenen Feststoffs mit Wasserstoff bei einer Temperatur im Bereich von 100 bis 350°C,ii) reduction of the solid obtained in i) with hydrogen at a temperature in the range from 100 to 350 ° C.,
wobei man Schritt ii) unmittelbar im Anschluss an Schritt i) durchführt, dadurch gekennzeichnet, dass man die zu hydrierende wässrige Saccharidlösung vor der Hydrierung mit dem Trägermaterial in Kontakt bringt.wherein step ii) is carried out immediately after step i), characterized in that the aqueous saccharide solution to be hydrogenated is brought into contact with the carrier material before the hydrogenation.
2. Verfahren nach Anspruch 1 , wobei als Zuckeralkohol Sorbitol oder Xylitol hergestellt wird.2. The method according to claim 1, wherein sorbitol or xylitol is produced as the sugar alcohol.
3. Verfahren nach Anspruch 1 , worin die wässrige Saccharidlösung ein Weizen- oder Maisstärkehydrolysat ist.3. The method of claim 1, wherein the aqueous saccharide solution is a wheat or corn starch hydrolyzate.
4. Verfahren nach einem der vorhergehenden Ansprüche, worin die wässrige Saccharidlösung vor der Hydrierung durch Silica-Stränge gepresst wird. Kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen4. The method according to any one of the preceding claims, wherein the aqueous saccharide solution is pressed through silica strands prior to hydrogenation. Continuous process for the production of sugar alcohols
ZusammenfassungSummary
Kontinuierliches Verfahren zur Herstellung von Zuckeralkoholen durch katalytische Hydrierung einer wässrigen Lösung eines Saccharids, das bei der Hydrierung den entsprechenden Zuckeralkohol bildet, an einem Ruthenium-Katalysator, der erhältlich ist durch:Continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous solution of a saccharide, which forms the corresponding sugar alcohol on hydrogenation, over a ruthenium catalyst, which is obtainable by:
i) ein oder mehrfaches Behandeln eines Trägermaterials auf Basis von amorphem Siliziumdioxid mit einer halogenfreien wässrigen Lösung einer niedermolekularen Rutheniumverbindung und anschließendes Trocknen des behandelten Trägermaterials bei einer Temperatur unterhalb 200°C,i) one or more times treatment of a carrier 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 carrier material at a temperature below 200 ° C.,
ii) Reduktion des in i) erhaltenen Feststoffs mit Wasserstoff bei einer Temperatur im Bereich von 100 bis 350°C,ii) reduction of the solid obtained in i) with hydrogen at a temperature in the range from 100 to 350 ° C.,
wobei man Schritt ii) unmittelbar im Anschluss an Schritt i) durchführt, wobei man die zu hydrierende wässrige Saccharidlösung vor der Hydrierung mit dem Trägermaterial in Kontakt bringt. wherein step ii) is carried out immediately after step i), the aqueous saccharide solution to be hydrogenated being brought into contact with the carrier material before the hydrogenation.
EP03780110A 2002-12-11 2003-12-03 Continuous method for the production of sugar alcohols Withdrawn EP1572607A1 (en)

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DE10258089 2002-12-11
DE2002158089 DE10258089A1 (en) 2002-12-11 2002-12-11 Continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous saccharide solution in the presence of a ruthenium catalyst prepared by treatment of an amorphous silicon dioxide support material
DE2003152336 DE10352336A1 (en) 2003-11-06 2003-11-06 Continuous process for the production of sugar alcohols by catalytic hydrogenation of an aqueous saccharide solution in the presence of a ruthenium catalyst prepared by treatment of an amorphous silicon dioxide support material
DE10352336 2003-11-06
PCT/EP2003/013632 WO2004052813A1 (en) 2002-12-11 2003-12-03 Continuous method for the production of sugar alcohols

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