EP1326709A1

EP1326709A1 - Method for producing catalysts consisting of metal of the platinum group by means of electroless deposition and the use thereof for the direct synthesis of hydrogen peroxide

Info

Publication number: EP1326709A1
Application number: EP01969806A
Authority: EP
Inventors: Martin Fischer; Thomas Butz
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-10-02
Filing date: 2001-10-01
Publication date: 2003-07-16
Also published as: DE10048844A1; US20040037770A1; KR100821423B1; JP2004516921A; DE50112872D1; CN1276789C; MXPA03002660A; EP1328344A1; JP2004516922A; CN1468150A; KR20030041143A; WO2002028528A1; ATE369912T1; CA2423009A1; WO2002028527A1; AU2002213986A1; JP4054676B2; US7070757B2; KR20030041144A; CA2422806A1

Abstract

The invention relates to a supported platinum group metal catalyst obtainable by controlled electroless deposition of at least one platinum group metal from a deposition solution which comprises i) at least one homogeneously dissolved platinum group metal compound, ii) a reducing agent and iii) at least one control agent selected from isopolyacids and heteropolyacids of niobium, tantalum, molybdenum, tungsten and vanadium or their salts.

Description

METHOD FOR PRODUCING PLATINUM METAL CATALYSTS BY CURRENTLY DEPOSITING AND THE USE THEREOF FOR DIRECT SYNTHESIS OF HYDROGEN PEROXIDE

Description 5

The present invention relates to a process for the preparation of catalysts by electroless deposition of at least one platinum metal on a non-porous non-metallic support, the catalysts obtainable by this process, the uses

10 d ng of the catalysts for the synthesis of hydrogen peroxide from the elements and for the hydrogenation of inorganic and organic compounds, as well as a process for the production of hydrogen peroxide and a process for catalytic reduction using these catalysts.

15

Catalysts, which contain platinum metals as catalytically active substances, are used in a variety of forms and are of great technical importance, e.g. B. in the reduction or hydrogenation of organic compounds and in catalytic cleaning

20 of exhaust gases from industry and traffic.

For technical applications, use is made of supported platinum metal catalysts, which only use small amounts of the expensive noble metals on mostly catalytically inactive support materials

25 with a large surface such. B. coal, aluminum oxide, silicon oxide, ceramic or other mineral carriers. The catalytically active metals are usually applied to such porous supports by impregnating or impregnating the supports with solutions of salts or organometallic compounds.

30 gene of the catalytically active metal and subsequent immobilization by precipitation, hydrolyzing, tempering, calcining and / or forming.

EP-A-0 875 235 describes a process for producing 35 supported noble metal catalysts on porous oxidic supports by electroless deposition of noble metals from aqueous solutions with reducing agents and in the presence of complexing agents.

40 The unpublished German patent application P 199 15 681.6 describes a process for the preparation of supported platinum metal catalysts on metallic supports by electroless deposition of a platinum metal from aqueous solution in the presence of at least one reducing agent and at least one complex.

45 educators. DE-A-44 12 463 describes the use of a palladium colloid solution containing at least one reducing agent and at least one protective colloid and additionally at least one noble metal or a noble metal compound for pretreating electrically non-conductive substrate surfaces before they are metallized with a metallizing solution. The deposition of at least one platinum metal on a non-porous non-metallic support is not described. This document also contains no teaching on the production of catalysts.

No. 5,082,647 describes a process for the direct synthesis of hydrogen peroxide, a catalyst being used which comprises at least one metal of subgroup VIII on a hydrophobic support. Styrene-divinylbenzene copolymers, homo- and copolymers of ethylene and propylene, hydrophobized silicon dioxide, polytetrafluoroethylene, fluorinated carbon and carbon which have been hydrophobized by treatment with a silane or with fluorine are mentioned as hydrophobic carrier materials. The hydrophobic carrier has a surface area of at least 50 m ² / g.

WO-A-99/32398 describes a process for the direct synthesis of hydrogen peroxide, wherein catalysts on supports with small BET surface areas of preferably less than 1 m ² per ml reactor volume are also to be used. Non-porous non-metals such as glass, quartz and organic polymers are proposed as carrier materials. For the preparation of the catalysts, a general reference is made to the disclosure of EP-A-0 878 235, US 5,338,531 and to JR Kosak "A new novel fixed bed catalyst for the direct combination of H ₂ and 0 ₂ to H ₂ 0 ₂ ", Chem. Ind. (Dekker), 1995, volume 62, Catalysis of Organic Reactions. However, none of the cited references describes the preparation of catalysts on non-metallic non-porous supports. According to the exemplary embodiment of WO-A-99/32398, glass wool which has not been pretreated to produce a catalyst is impregnated with palladium chloride and hexachloroplatinic acid and the metals are then reduced at 300 ° C. with hydrogen. In the subsequent production of hydrogen peroxide with this catalyst in the gas phase, only extremely low space-time yields of about 5 g / 1 × h are achieved.

The present invention has for its object to provide a method for producing improved non-metal-supported platinum metal catalysts. The aim here is to ensure that the expensive platinum metal is deposited as completely as possible and / or that the noble metal adheres well to the non-metal carrier. Furthermore, the ca Talysators preferably have a high catalytic activity and selectivity in hydrogenations, in particular in the direct synthesis of H ₂ 0 ₂ from hydrogen and oxygen. The catalysts should preferably be distinguished by improved service lives.

Surprisingly, the object was achieved by providing a process for the preparation of catalysts which comprise at least one platinum metal on a non-porous non-metallic support, wherein the support is first activated and then at least one platinum metal is electrolessly deposited on the support thus pretreated. For electroless deposition, an aqueous medium comprising at least one compound or a complex of a platinum metal and at least one reducing agent is brought into contact with the carrier. In contrast to catalysts known from the prior art, the catalysts produced according to the invention have excellent catalyst properties. In addition, essentially quantitative deposition of the platinum metal from the solution can be achieved. Surprisingly, good adhesion of the platinum metals is also achieved on the non-porous non-metallic supports used. Thus, the catalytic coatings produced according to the invention have even with strong mechanical stress, such as z. B. occurs in the hydrogen peroxide synthesis, high abrasion resistance. Even after prolonged operation, there is usually no mechanical detachment.

The present invention relates to a process for producing a catalyst which comprises at least one platinum metal on a non-porous non-metallic support, wherein

a) optionally roughening the surface of the support,

b) activating the support, which may have been roughened on the surface, by treating it preferably with a reducing agent and a salt of a platinum metal,

c) electrolessly depositing at least one platinum metal on the carrier treated according to step b), an aqueous medium comprising at least one compound or a complex of a platinum metal and at least one reducing agent being brought into contact with the carrier, and

d) optionally the catalyst obtained in step c) is formed. According to the invention, a non-porous support is used to produce the catalyst. A non-porous carrier is understood to mean a carrier with a pore volume determined by mercury porosimetry (Hg porosimetry) of at most 1.0 ml / g, preferably at most 0.1 ml / g and particularly preferably at most 0.05 ml / g. The proportion of the pore volume in the total volume of the carrier workpiece is preferably at most 2%, preferably at most 0.5%.

The supports used according to the invention preferably have a BET surface area of at most 5 m ² / g, in particular at most 0.2 m ² / g.

The non-metallic material used as the carrier is preferably selected from mineral materials, plastics and mixtures and combinations thereof.

In the present case, the expression “mineral material” encompasses very generally non-metallic inorganic materials, such as natural and synthetic minerals, glasses, ceramics etc. A glass is preferably used as the mineral material. Glasses made of molten silicon dioxide or molten quartz and glasses based on alkali metal, alkaline earth metal, borosilicate, aluminosilicate and lead silicate are preferred. Preferred mineral carrier materials are also borate, phosphate, germanate,

Chalcogenide and halide glasses, such as. B. from beryllium fluoride.

The mineral material used as the carrier is preferably also selected from ceramic materials. Suitable ceramic materials can be produced from metal oxides, borides, nitrides and / or carbides. The ceramic materials used according to the invention can be glazed or unglazed, crystalline or partially crystalline. For the method according to the invention, ceramics made from base materials are preferably used, which are selected from aluminum oxide, silicon carbide, silicon nitride, zirconium dioxide and mixtures thereof. Ceramics containing cations, such as the z. B. in chelate, steatite, cordierite, anorthite, mullite or pollucite is the case. Ceramic composite materials are also preferred.

According to a further preferred embodiment, a plastic carrier is used for the method according to the invention.

The carriers used according to the invention preferably comprise at least one natural or synthetic polymeric material. Examples of such materials are:

1. Polymers of mono- and diolefins, for example polypropylene, polyisobutylene, polybutene-1, poly-4-methyl-pentene-1, polyisoprene or polybutadiene, and polymers of cycloolefins, such as, for. B. of cyclopentene or norbornene; also polyethylene (which may optionally be crosslinked), e.g. B. High density polyethylene (HDPE), high density and high molecular weight polyethylene (HDPE-HMW), high density and ultra high molecular weight polyethylene (HDPE-UHMW), medium density polyethylene

(MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), branched low density polyethylene (VLDPE).

2. Mixtures of the polymers mentioned under 1., for. B. Mixtures of polypropylene with polyisobutylene, polypropylene with polyethylene (e.g. PP / HDPE, PP / LDPE) and mixtures of different types of polyethylene (e.g. LDPE / HDPE).

3. Copolymers of mono- and diolefins with one another or with other vinyl monomers, such as. B. ethylene-propylene copolymers, and their mixtures with other polymers, such as. B. polyamides.

4. Polyvinyl aromatics such as polystyrene, poly- (p-methylstyrene), poly- (α-methylstyrene).

5. Copolymers of polyvinyl aromatics, such as styrene or α-methyl styrene, with dienes or acrylic derivatives, such as. B. styrene-butadiene, styrene-acrylonitrile, styrene-alkyl methacrylate, styrene-butadiene-alkyl acrylate and methacrylate, styrene-maleic anhydride, styrene-acrylonitrile-methyl acrylate; Mixtures of high impact strength from styrene copolymers and another polymer, such as. B. a polyacrylate, a diene poly eren or an ethylene-propylene-diene terpolymer; and block copolymers of styrene, such as. B. styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene / butylene-styrene or styrene-ethylene / propylene-styrene.

6. graft copolymers of polyvinylaromatics, such as styrene or α-methylstyrene, such as. B. styrene on polybutadiene, styrene on polybutadiene-styrene or polybutadiene-acrylonitrile copolymers, styrene and acrylonitrile (or methacrylonitrile) on polybutadiene; Styrene, acrylonitrile and methyl methacrylate on polybutadiene; Styrene and maleic anhydride on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleimide on polybutadiene; Styrene and maleimide on polybuta- diene, styrene and alkyl acrylates or alkyl ethacrylates on polybutadiene, styrene and acrylonitrile on ethylene-propylene-diene terpolymers, styrene and acrylonitrile on polyalkylacrylates or polyalkyl methacrylates, styrene and acrylonitrile on acrylate-butadiene copolymers, and mixtures thereof with the under 5. mentioned copolymers, such as. B. are known as so-called ABS, MBS, ASA or AES polymers.

7. Halogen-containing polymers, such as. B. polychloroprene, chlorinated rubber, chlorinated and brominated copolymer of isobutylene-isoprene (halobutyl rubber), chlorinated or chlorosulfonated polyethylene, copolymers of ethylene and chlorinated ethylene, epichlorohydrin homo- and copolymers, in particular polymers of halogen-containing vinyl compounds, such as , B. polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride; and their copolymers, such as vinyl chloride-vinylidene chloride, vinyl chloride-vinyl acetate or vinylidene chloride-vinyl acetate.

8. Polymers which are derived from α, β-unsaturated acids and their derivatives, such as polyacrylates and polymethacrylates, impact-modified polymethyl methacrylates, polyacrylamides and polyacrylonitriles with butyl acrylate.

9. copolymers of the monomers mentioned under 8 with each other or with other unsaturated monomers, such as. B. acrylonitrile-butadiene copolymers, acrylonitrile-alkyl acrylate copolymers, acrylonitrile-alkoxyalkyl acrylate copolymers, acrylonitrile-vinyl halide copolymers or acrylonitrile-alkyl methacrylate-butadiene terpolymers.

10. Polyurethanes.

11. Polyamides and copolyamides from diamines and dicarboxylic acids to and / or from aminocarboxylic acids or the corresponding LAECs Amen ^{^"derive",} ^"such ^as" polyamide ^{^"4",} ^"polyamide ^'6, ^~ amide PöTy- 6/6, 6 / 10, 6/9, 6/12, 4/6, 12/12, polyamide 11, polyamide 12, aromatic polyamides, for example starting from p-phenylenediamine and adipic acid, polyamides made from hexamethylene diamine in and Iso- and / or terephthalic acid and optionally an elastomer as modifier, for example poly-2,4,4-trimethyl-hexamethylene terephthalamide or poly-m-phenylene-isophthalamide. Block copolymers of the above-mentioned polyamides are also suitable Polyolefins, olefin copolymers, ionomers or chemically bonded or grafted elastomers, or with polyethers, such as, for example, with polyethylene glycol, polypropylene glycol or polytetramethylene glycol, are suitable also polyamides or copolyamides modified with EPDM or ABS; and polyamides condensed during processing (“RIM polyamide systems”).

12. Polyureas, polyimides, polyamideimides, polyetherimides, polyesterimides, polyhydantoins and polybenzimidazoles.

13. Polyesters which are derived from dicarboxylic acids and dialcohols and / or from hydroxycarboxylic acids or the corresponding lactones, such as polyethylene terephthalate, polybutylene terephthalate, poly-l, 4-dimethylolcyclohexane terephthalate, polyhydroxybenzoates, and block polyether esters which differ from polyethers Derive hydroxyl end groups; furthermore polyesters modified with polycarbonates or MBS.

14. Polycarbonates and polyester carbonates.

15. Crosslinked polymers, which, for. B. from aldehydes on the one hand and phenols, urea or melamine on the other hand, such as phenol-formaldehyde, urea-formaldehyde and melamine-formaldehyde resins.

16. Crosslinkable acrylic resins derived from substituted acrylic acid esters, such as. B. of epoxy acrylates, urethane acrylates or polyester acrylates.

17. Alkyd resins, polyester resins and acrylate resins which are crosslinked with melamine resins, urea resins, isocyanates, isocyanurates, polyisocyanates or epoxy resins.

18. Crosslinked epoxy resins derived from aliphatic, cycloaliphatic, heterocyclic or aromatic glycidyl compounds, eg. B. products of bisphenol A diglycidyl ether, bisphenol F diglycid lethern, using conventional hardeners, such as. B. anhydrides or amines with or without accelerators.

The carrier is preferably used in the form of a particulate, line-shaped, sheet-like or three-dimensional structure. The term particulate structures encompasses everything from fine pigments to macroscopic particles. These include in particular those with a particle size of 0.25 nm to 10 mm. Line-shaped structures are understood to mean in particular fibers, filaments and the like. The non-metallic supports are preferably used in the form of glass or plastic fibers. Sheet-like structures are in particular woven fabrics, knitted fabrics, felts, nonwovens, nets, knitted fabrics, mats, etc. Three-dimensional structures are generally shaped bodies of various dimensions.

The non-metallic supports are preferably used in the form of shaped bodies. The shaped bodies can have the shape of spheres, pellets, short strands, Raschig rings, Pall® rings, saddle bodies, cylindrical lattice fillers, Hackettes, spirals or helices.

The non-metallic supports are also preferably used in the form of fabrics. The tissues in turn can be in the form of monoliths, i.e. H. ordered packs.

Particularly suitable monoliths are made up of several layers of corrugated, kinked and / or smooth fabric, which are preferably arranged in such a way that adjacent layers form more or less closed channels. The hydraulic diameter of the channels is preferably in the range from 1 to 10 mm, in particular from 1.5 to 3 mm (as defined in VDI Heat Atlas, section LE 1). The channels can be straight or curved. Multi-layer fabrics are preferably used, in which smooth and wavy or kinked channels are formed. While packings are generally added to the reactor as a loose bed, monoliths are preferably installed in the reactor, in particular in such a way that the channels are inclined against the flow direction of the reaction medium. The fabric layers themselves are preferably installed parallel to the flow direction in the reactor. If several of these units are connected in series, the installation is preferably carried out in such a way that the throughflow channels are inclined alternately in opposite directions to the direction of flow. The structural units are preferably installed in such a way that the fabric layers of two successive structural units form an angle of preferably approximately 90 ° to one another. Winding modules made of corrugated or kinked and, if necessary, also of flat fabric layers are also suitable.

Step a)

In general, the non-porous non-metallic supports used according to the invention can be used for catalyst production in the way that they occur in their respective production process. If desired, however, the surface of the carrier can be roughened before the subsequent process steps.

Mechanical and / or chemical methods can be used to roughen the carrier surface. A roughening of carriers made of mineral materials, such as. B. of glass or ceramic carriers, is preferably carried out by known mechanical methods, such as. B. by grinding with a material that has a higher hardness than that of the carrier. Suitable abrasive materials are e.g. B. quartz, corundum, garnet, emery and diamond. A suitable method for roughening glass or ceramic balls involves treatment in a rotating rotary tube with a finely powdered abrasive. The abrasive can then be separated from the backing material by conventional methods such as sieving or rinsing out with water. Glass surfaces can also be roughened by sandblasting.

Another suitable method for increasing the roughness of the carrier surface is treatment with suitable chemicals. Mineral materials can preferably be etched, e.g. B. with hydrofluoric acid, aqueous alkali or aqueous mineral acid, such as. As hydrochloric acid, nitric acid, phosphoric acid, are roughened on the surface. Carriers made of plastic can preferably be roughened by treatment with chemicals attacking the surface, preferably with oxidizing agents. Suitable chemicals for roughening plastic surfaces are e.g. B. nitric acid, hydrogen peroxide, ammonia etc. Preferably about 10% nitric acid, about 50% hydrogen peroxide or a mixture of about 10% ammonia and about 10% hydrogen peroxide, optionally over several hours and at elevated temperatures , used.

Step b)

“Activation” of the carrier is understood to mean a process in which germs for electroless deposition are formed on the surface of the carrier. The nuclei for electroless deposition generally consist of a metal, preferably a platinum metal, particularly preferably palladium. The carrier is expediently activated by treating it with a reducing agent and a salt of a platinum metal.

The treatment of the carrier with the reducing agent and the platinum metal salt can be carried out simultaneously or in succession, in both cases the treatment can be carried out in one or more steps. If desired, the carrier can be cleaned prior to treatment. Likewise, a cleaning step can follow the treatment or, in the case of a treatment in several steps, each treatment step. According to a first preferred embodiment, the treatment of the carrier in step b) is carried out with an aqueous medium which comprises at least one reducing agent and at least one salt of a platinum metal. The treatment can take place in one or more steps.

According to a further preferred embodiment, the carrier is treated in step b) separately with at least one reducing agent and at least one platinum metal salt. A preferred method for treating the carrier in step b) comprises the following substeps:

bl) optionally cleaning the carrier,

b2) treating the carrier with an aqueous medium which contains at least one reducing agent,

b3) treating the support with an aqueous medium which comprises at least one salt of a platinum metal,

Steps b2) to b3) can be carried out once or several times. The treatment can be started and completed both with step b2) and with step b3). Steps b2) and b3) are preferably repeated one to ten times.

If desired, a cleaning step can follow treatment steps b2) and / or b3), e.g. B. by bringing the carrier into contact with a rinsing solution.

The carrier can be cleaned before the treatment steps by customary methods known to those skilled in the art. This includes e.g. B. see the treatment with aqueous surfactant solutions and / or the treatment with organic solvents and solvent mixtures, such as. As ethanol, ethanol-water mixtures, ethyl acetate, acetone, etc. If desired, cleaning can be carried out using ultrasound. As rinsing solutions for cleaning the carrier after a treatment step are, for. B. the pure aqueous media used for the treatment steps and in particular water.

Suitable aqueous media for the treatment steps are mentioned below in step c), to which reference is made here. In step b), an aqueous medium which is essentially free of organic solvents is preferably used. This medium preferably additionally contains at least one inorganic acid, in particular hydrochloric acid. Preferably point the aqueous media used in step b) have an acidic pH. A pH <6, in particular <5, is particularly preferred.

To treat the carrier with the reducing agent (and, if appropriate, simultaneously with the platinum metal salt), an aqueous medium is used which contains at least one reducing agent in completely or partially dissolved form. Suitable reducing agents are mentioned below in step c), to which reference is made here. Reducing agents preferably used in step b) are tin (II) chloride and titanium (III) chloride.

Platinum metal salts suitable for treating the carrier in step b) are mentioned in the following step c), to which reference is made here. At least one is preferred as the platinum metal salt

15 palladium salt used. That to treat the wearer in

Step b) the aqueous medium used can contain, in addition to at least one platinum metal salt, at least one further salt of a metal of the iron group and / or the 1st subgroup. Nickel and silver salts are preferred.

20

According to a preferred embodiment, the treatment of the carrier in step b) comprises contacting with an aqueous medium with a tin (II) chloride content in the range from about 1 to 20 g / 1 and a content of concentrated hydrochloric acid of about 1

25 to 50 ml / 1. The treatment is preferably carried out at a temperature in the range from about 10 to 40 ° C., in particular at ambient temperature. The treatment time with the reducing agent is in particular in a range from about 0.1 to 30 minutes, in particular 0.5 to 10 minutes. The carrier is preferably after

30 treatment with the reducing agent rinsed with water. This is then brought into contact with an aqueous medium with a palladium chloride content in the range from about 0.02 to 2 g / 1 and a content of concentrated hydrochloric acid in the range from about 0.1 to 10 ml / 1. This aqueous medium can

35 tall salts, as previously described, included. The treatment with the platinum metal is preferably also carried out at a temperature in the range from about 10 to 40 ° C., in particular at ambient temperature. The treatment time is preferably in a range from about 0.1 to 30 minutes, particularly preferably 0.5 to

40 10 minutes. Finally, the treated carrier is preferably rinsed again with water.

According to a further preferred embodiment, an aqueous medium which contains at least one reducing agent, at least one platinum metal salt and, if appropriate, at least one further salt of a metal of the iron group or the first subgroup, is first provided in step b) and the carrier then brought into contact with it. The treatment of the carrier with the solution provided is preferably carried out within about 24 hours. Finally, the treated carrier is preferably rinsed with water.

In step b) a quantity of platinum metal is deposited on the carrier which is small compared to the total quantity deposited on the carrier. The amount of platinum metal deposited in step b) is preferably at most 10% by weight, particularly preferably at most 1% by weight, based on the total amount deposited on the support.

The pretreatment of the support in step b) contributes to the fact that the process according to the invention gives catalysts in which the platinum metal adheres well to the non-porous support material. The catalytic coatings produced in this way have a high abrasion resistance even under heavy mechanical stress.

If desired, the support which has been pretreated in this way can finally be dried by customary processes known to those skilled in the art. However, it can also be used moist for the subsequent treatment in step c).

Step c)

Platinum metals in the sense of the invention are the noble metals of the 8th subgroup of the periodic table which do not belong to the iron group, namely ruthenium, rhodium, iridium, palladium, osmium and platinum. Ruthenium, rhodium, palladium and platinum are preferred, palladium and platinum are particularly preferred. The catalysts according to the invention can comprise several platinum metals. All combinations of the platinum metals mentioned are suitable, combinations of palladium and platinum, of palladium and rhodium, of palladium and iridium, of palladium, platinum and rhodium and of palladium, platinum and iridium are preferred. Palladium and platinum are particularly preferred as a combination. In the combinations with palladium, palladium is preferably the main platinum metal component. The palladium content is then preferably above 40% by weight, preferably above

60 wt .-% and particularly preferably above 80 wt .-%, based on the total platinum metal content. The further platinum metals optionally contained as secondary constituents can each account for up to 30% by weight, preferably up to 20% by weight and particularly preferably up to 15% by weight, of the total platinum metal content. The platinum metals preferably comprise 80 to 100% by weight of palladium and 0 to 20% by weight of platinum or iridium. In most cases make up 1 to 3 of the platinum metals mentioned more than 95 wt .-% of the amount of platinum metal used. If, in addition to a main platinum metal, other platinum metals are also present, these are generally present in amounts of greater than 0.001% by weight, preferably greater than 0.01% by weight, e.g. B. about 0.1% by weight, about 1% by weight or about 5% by weight.

In addition to platinum metals, the catalytically active component of the catalysts according to the invention can contain further elements as additional components or, if appropriate, in the form of impurities. Preferred additional components, the z. B. can affect the activity and / or selectivity of the catalyst are selected from metals, non-metals and their compounds. These preferably include metals such as cobalt, nickel, copper, silver, gold, chromium, molybdenum, tungsten, manganese, rhenium, aluminum, tin, lead, arsenic, antimony and bismuth, and non-metals such as boron, carbon, silicon, Nitrogen and phosphorus. The metals and non-metals mentioned can be present in the catalytically active coating both in ionic and in nonionic form. In addition, the catalytically active component may contain other elements (metals and non-metals) as impurities, e.g. B. by the fact that the catalytically active components used contain impurities, or that components of the components used in the process according to the invention are incorporated into the platinum metal coatings during the process for the preparation of the catalysts according to the invention, such as. B. alkali and alkaline earth metals, phosphorus, boron and halogens.

In step c), an aqueous medium is preferably used which additionally comprises at least one compound of a metal from the 6th, 7th or 1st subgroup, the iron group or bismuth.

The additional components can be present at 0.001 to 25% by weight, based on the platinum metal content. Additional components used as promoters or dopants generally make up 0.01 to 20% by weight, preferably 0.1 to 15% by weight and in particular 0.5 to 10% by weight, based on the platinum metal content ,

In the novel process, the platinum metals are preferential, as a ^'platinum metal complexes used. Platinum metal complexes in which the platinum metal is present in the oxidation states +1 to +4 are preferably used. Four-coordinate complexes are preferred. The process according to the invention is preferably suitable for the production of platinum metal catalysts in which palladium is the main platinum metal component.

Palladium (II) complexes are preferably suitable for the preparation of catalysts which contain palladium, and in particular of catalysts which contain palladium as the main platinum metal component. Palladium (II) complexes in which palladium has the coordination number 4 are particularly suitable.

Such combinations of platinum metal ions and ligand are preferably selected whose complex formation constant is> 1000 and in particular> 10000.

Suitable combinations of ligands and counterions for palladium complexes and for platinum metal complexes other than palladium can be selected according to the principle of charge neutrality. Suitable negatively charged ligands are e.g. B. selected from halides and pseudohalides, such as chloride, bromide, yodide, CN, OCN and SCN, -C-C ₆ carboxylic acids, such as formic acid, acetic acid and propionic acid and their salts, chelate ligands, such as ethylenediaminetetraacetic acid (EDTA), Nitrilotriacetic acid, 1,2-diaminocyclohexanetetraacetic acid and its salts, aminophosphonic acids such as nitrilomethylenephosphonic acid, diketonates such as acetylacetonate, hydroxycarboxylic acids such as glycolic acid, lactic acid, tartaric acid and gluconic acid, and their salts. Suitable as electroneutral ligands are e.g. B. alkyl nitriles such as acetonitrile, amines such as ammonia, primary, secondary and tertiary C ₁ -C ₆ alkyl amines such as ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine, dimethylamine, di - ethylamine, diisopropylamine, di-n-butylamine, trimethylamine, triethylamine, tripropylamine, N, N-dimethylethylamine, N, N-dimethylisopropylamine and N, N-dimethylbutylamine, di-, tri-, tetra- and poly- amines, such as ethylenediamine, diethylenetriamine and triethylenetetraamine, non-aromatic and aromatic cyclic amines, such as pyrolidine, piperidine, morpholine, piperazine, pyrrole and their nCC ₆ alkyl derivatives, pyridine and phenanthroline, phosphines, such as tertiary Ci-C _ö -Al yl and C ₆ -C ₂ arylphosphines, in particular triphenylphosphine, and sulfides, such as C ₆ -C ₆ mono- and dialkyl sulfides, C ₆ -C ₁₂ mono- and diaryl sulfides and oxygen compounds, di-Cι -C ₆ alkanols and phenols and their ethers.

The halides chloride and bromide are particularly preferred as complex ligands; Amines, especially ammonia and triethylamine, cyanide and ethylenediaminetetraacetic acid, and the di-, tri- or tetra-alkali metal (such as sodium) or ammonium salts thereof. Alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, nitrite, nitrate and ammonium are preferably suitable as counterions.

Suitable platinum metal complexes are preferably at least 0.01% by weight soluble in water at room temperature (25 ° C.). According to the invention, the platinum metal complex (s) are used in an aqueous medium, in such a concentration that the platinum metal content of the solution is in the range from 0.001 to 2 g / 1, preferably in the range from 0.1 to 0.5 g /1.

Preferred palladium complexes are H ₂ PdHal ₄ , M ₂ PdHal, M ₂ Pd (CN) ₄ , (NH ₄ ) ₂ PdHal ₄ , Pd (NH ₃ ) ₄ Hal ₂ , Pd (NH ₃ ) ₄ (N0 ₃ ) ₂ and Pd (NH ₃ ) ₄ (CN) ₂ , where M represents alkali metals, especially sodium and potassium, and shark represents halogen atoms, especially chlorine, bromine or iodine.

Preferred further platinum metal complexes are (NH ₄ ) ₂ IrCl ₆ , HPtCl, (NH) ₂ PtCl, Na ₂ PtCl ₄ and K ₂ PtCl ₄ .

In addition, the aqueous medium contains at least one reducing agent in completely or partially dissolved form. Suitable as reducing agents for steps b) and c) are all substances or mixtures of substances whose redox potential lies below the redox potential of the platinum metal complex used. Substances with a standard potential in aqueous medium of less than +0.5 volts are preferred, but preferably with a standard potential less than 0 volts. At least 1% by weight, preferably at least 10% by weight, of the reducing agent or mixture of reducing agents is lent in the aqueous medium at room temperature (25.degree. C.). In preferred embodiments of the present invention, the reducing agent or the reducing agent mixture is practically completely soluble in the aqueous medium.

Examples of suitable reducing agents are carboxylic acids, such as formic acid, citric acid, lactic acid, tartaric acid and in particular the salts of the carboxylic acids, preferably the alkali metal, alkaline earth metal, ammonium and Ci-Cio-alkylammonium salts, phosphorous or hypophosphorous acid, the salts of phosphorous or hypo - Phosphorous acid, especially the alkali metal or alkaline earth metal salts, Ci-Cio-alkanols, such as methanol, ethanol and isopropanol, sugar, such as aldoses and ketoses in the form of mono-, di- and oligosaccharides, especially glucose, fructose and Lactose, aldehydes, such as formaldehyde, hydrogen boron compounds, such as. B. borohydrides, boranes, metal boranates and borane complexes, for. B. diborane, sodium borohydride and aminoboranes, in particular trimethylamine borane, hydrazine and alkylhydrazines, such as methylhydrazine, hydrogendithionites and dithionites, especially sodium and potassium liumhydrogen dithionite, sodium, potassium and zinc dithionite, hydrogen sulfites and sulfites, in particular sodium and potassium hydrogen sulfite, sodium, potassium and calcium sulfite, hydroxylamine and urea, and mixtures thereof.

Preferred reducing agents for step c) are sodium and potassium hypophosphite, ammonium formate, trimethylamine borane, sodium borohydride, sodium dithionite and sodium hydrogen dithionite, and mixtures of ammonium formate and sodium hypophosphite.

As a rule, at least one redox equivalent, based on the sum of the platinum metals and additional components (e.g. promoters / doping components), of reducing agent is used. The reducing agent is preferably used in excess. A molar ratio of reducing agent to platinum metal of 10: 1 to 100: 1 and particularly preferably 20: 1 to 60: 1, such as for example about 30: 1, about 40: 1 or about 50: 1, is particularly suitable.

In step c), an aqueous medium with a pH of greater than 6 is preferably used for the electroless deposition of the platinum metal. This is preferably in a range from 7 to 14, in particular 8 to 12. To this end, it may be necessary to add at least one base to the aqueous medium containing the platinum metal complex and the reducing agent in order to achieve the desired pH. For the purposes of the present invention, bases are all substances or compounds which are suitable for adjusting the pH of the aqueous medium to the desired value. In particular, those bases are used which have complex stabilizing properties, i. H. at least partially have a Lewis base character. The base is preferably selected from metal oxides, metal hydroxides, in particular alkali metal hydroxides, such as sodium hydroxide and potassium hydroxide, metal carbonates, in particular alkali metal and alkaline earth metal carbonates, such as lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate and calcium carbonate, nitrogen bases, in particular ammonia, primary, secondary and tertiary amines, such as those previously described for the nitrogen-containing complex ligands. Buffer systems are also suitable, in particular those from the aforementioned bases, the salts of the aforementioned bases and / or suitable acids. Particularly preferred bases are ammonia and sodium hydroxide solution.

For the purposes of the invention, aqueous media are substances or mixtures of substances which are liquid under the process conditions and contain at least 10% by weight, preferably at least 30% by weight and in particular at least 50% by weight of water. The part other than water is preferably selected from water- at least partially soluble or at least partially miscible with water inorganic or organic substances. For example, the substances other than water are selected from organic solvents, -C ₂₂ alkanols, in particular methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, pentanols and hexanols, C ₄ -C _8- cycloalkyl ethers, such as tetrahydrofuran, pyrans, dioxanes and trioxanes, C 1 -C 4 -dialkyl ethers, such as dimethyl ether, dibutyl ether and methyl butyl ether, and customary auxiliaries, such as are used in processes for electroless deposition.

The aqueous medium preferably contains less than 40%, in particular less than 30% and particularly preferably less than 20% organic solvent.

In preferred embodiments of the method according to the invention, the aqueous medium is essentially free of organic solvents.

In addition to at least one compound or a complex of a platinum metal and the reducing agent, the aqueous solution preferably additionally comprises at least one ligand (complexing agent). The ligand preferably has at least one halogen, nitrogen, oxygen and / or phosphorus atom. Complexing agents in the sense of the present invention are ions or compounds which are able to stabilize metal ions in aqueous media. As a rule, such complexing agents are donors or salts of donors. Suitable donors usually have a lone pair of electrons that can interact with the metal ions. Complexing agents which have the above-mentioned hetero atoms as donors are particularly suitable for the process according to the invention. Examples of suitable complexing agents are the metal salts, in particular the alkali metal and alkaline earth metal salts, of the compounds previously mentioned as complex ligands of the platinum metals.

Particularly suitable as complexing agents are hydrohalic acids, such as hydrogen bromide, hydrogen chloride and hydrogen iodide, the metal salts of the hydrohalic acids mentioned, in particular the alkali metal and alkaline earth metal salts, and also tin dihalides, zinc dihalides, ammonium salts, such as ammonium chloride, ammonium nitride, ammonium ammonium, ammonium ammonium, ammonium ammonium, ammonium ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium, ammonium ammonium, Alkali metal, alkaline earth metal and ammonium salts of carboxylic acids and hydroxycarboxylic acids, e.g. B. sodium and / or potassium tartrate. As a rule, platinum metal complex, reducing agent, optionally base and optionally complexing agent can be added to the aqueous medium in any order. Preferably at least a portion of the base is added to the aqueous medium before the reducing agent is added.

In one embodiment of the process according to the invention, the platinum metal complex, if appropriate the complexing agent and / or the base, are initially introduced into the aqueous medium in step c) and the reducing agent is then added.

As a rule, the temperature in step c) is in the range between 0 and 100 ° C., preferably in the range from 30 to 100 ° C. and in particular in the range from 40 to 85 ° C.

The active component, ie the platinum metal or the platinum metals and any additional components which may be present, generally make up 5 × 10 ^-4 to 5% by weight, in particular 10 ^-3 to 1% by weight, particularly preferably 0.01 to 1 0% by weight, based on the total catalyst mass (support + catalytically active coating).

If an additional complexing agent is added to the solution, 0.1 to 10,000 equivalents, preferably 1 to 1000 equivalents, particularly preferably 10 to 600 equivalents of the complexing agent, based on the platinum metal component, are generally used.

For example, the activated non-metallic support in step c) is only brought into contact with the aqueous medium when the aqueous medium contains at least the platinum metal complex, the reducing agent, at least part of the base and optionally the additional complexing agent. Likewise, the carrier can first be brought into contact with all of the components mentioned above, except for the platinum metal. The platinum metal is then at reaction temperature or a z. B. added up to 30 ° C lower temperature. “Reaction temperature” in the sense of the present invention means the temperature at which the platinum metal is deposited on the carrier.

In the process according to the invention, it has proven to be advantageous to ensure sufficient circulation of the reaction solution or the reaction mixture during the deposition of the platinum metal on the support in step c), for. B. by pumping or stirring. The reaction time required for the deposition of the platinum metal on the supports is generally between 0.5 and 500 minutes, preferably 1 and 300 minutes and particularly preferably between 2 and 60 minutes.

In the process according to the invention, preferably more than 70% by weight, preferably more than 80% by weight and particularly preferably more than 90% by weight of the platinum metals used are deposited on the support. As a rule, the platinum metal is bonded so tightly to the metallic support that it is not significantly replaced by contact with liquids and gases when used in catalytic reactions.

Additional components, in particular the elements suitable as promoters or doping components, can optionally be added to the aqueous medium together with the platinum metal, so that the deposition of the platinum metal and the installation of the additional components take place essentially simultaneously. The additional components can also be added to the reaction solution towards the end or after the platinum metal deposition has ended, as a result of which the additional components are preferably installed on the surface of the active component. The additional components can also be applied to the catalysts of the invention in a separate second step, for. B. by vapor deposition or by electroless separation from aqueous and non-aqueous media. The application of additional components to the catalysts of the invention in a separate second step is particularly advantageous if you want to apply them specifically to the surface of the active component. Furthermore, other deposition conditions that deviate from the conditions according to the invention can be selected for the second step.

Step d)

The catalysts obtained in step c) can then be formed at temperatures of 0 to 500 ° C, preferably 10 to 350 ° C, and pressures between normal pressure and 200 bar gauge pressure. The formation can take place, for example, in the presence of water and / or hydrogen. These can be used in the form of mixtures with an inert gas such as nitrogen. Formation with hydrogen is preferred. The temperature is preferably 10 to 200 ° C, in particular 30 to 150 ° C. The pressure is preferably 1 to 150 bar, in particular 10 to 100 bar and particularly preferably 30 to 70 bar. Typically, formation lasts 0.1 to 10 hours, preferably 1 to

5 hours. In a preferred embodiment of the process according to the invention, the catalysts are formed in presence of the aqueous reaction medium which is described below for the synthesis of water peroxide according to the invention.

In a preferred embodiment of the process according to the invention, the catalysts according to the invention are prepared by at least 0.01 to 3 g / 1, preferably 0.05 to 0.3 g / 1, of at least one platinum metal complex (weights based on the metal) , optionally 0.0001 to 0.3 g / 1, preferably 0.001 to 0.03 g / 1 of at least one further element compound and, based on the platinum metal, at least 20, preferably 50 and particularly preferably at least 100 equivalents of a complexing agent and at least 10 to 100, preferably 20 to 80 and particularly preferably 40 to 60 equivalents of a reducing agent dissolves in an aqueous medium.

Another object of the present invention is a catalyst obtainable by one of the methods described above.

The invention also relates to platinum metal catalysts with a non-metallic support and a catalytically active coating applied thereon, which are characterized in that the catalytically active coating has discrete platinum metal particles immobilized on the support surface with an average particle diameter of less than about 1 μ, preferably less less than about 100 nm. The platinum metal particles preferably have an average diameter of more than about 1 nm and can e.g. B. have diameters in the range of about 20 to 100 nm. The discrete particles preferably have an approximately spherical shape.

In particular, the subject matter is a catalyst in which the non-porous non-metallic support essentially consists of glass, ceramic or a polymer.

Such catalysts preferably have a platinum metal content in the range from 0.01 to 50 g / kg of support. In the direct synthesis of hydrogen peroxide from the elements, the catalysts obtainable by this process preferably have a selectivity of greater than 60%, in particular greater than 70% and particularly preferably greater than 80%.

The catalysts of the invention are preferably suitable for the hydrogenation of organic and inorganic compounds and in particular for organic compounds such as olefins, for. B. ethylene, propylene, acetylene and butadiene, carbonyl compounds, z. B. aldehydes, ketones, aromatics, such as. As benzene, and particularly preferably for the hydrogenation of oxygen.

Another object of the present invention is a process for the production of hydrogen peroxide, wherein a catalyst as described above in a liquid medium, preferably an essentially aqueous solution with an oxygen / hydrogen mixture with a mixing ratio in the range of about 5: 1 to 100: 1, especially 5: 1 to 30: 1.

The present invention also relates to the use of the catalysts according to the invention for the synthesis of hydrogen peroxide from the elements, both according to the anthraquinone process or an analogous process, and also by direct synthesis, ie by direct reaction of oxygen and hydrogen over a platinum metal catalyst in a liquid medium , Suitable methods are e.g. B. described in WO 98/16463, to which reference is made here in full. The use of the catalysts according to the invention for the direct synthesis of H ₂ 0 is particularly preferred.

Suitable reactors for the synthesis of H ₂ 0 ₂ are described, for example, in EP-A-068 862, EP-A-201 614 and EP-A-448 884. Tube reactors in which the catalyst according to the invention is present as a bed or in the form of cylindrical catalyst units are particularly preferred. Appropriate shaping for the carriers, as described above, can ensure optimum flow conditions for gas and liquid.

According to a preferred embodiment, the reaction is carried out in cocurrent with the reactor flooded with liquid and gas. The liquid phase preferably trickles down over the catalyst bed. The gas can be conducted in cocurrent or in countercurrent, preferably in cocurrent.

The hydrogen can preferably be fed to the reactor via one or more intermediate feeds downstream from the feed point of the oxygen or the air. The empty tube speed of reaction gas and reaction medium is preferably in a range from about 20 to 7000 m / h, particularly preferably in a range from 50 to 1400 m / h.

Water and / or Cχ-C ₃ -alkanols, in particular water and / or methanol, are preferably used as the reaction medium. If as a reaction medium water is used, this can be added up to 20 wt .-% of the alcohol, preferably methanol. If an alcoholic reaction medium is used, it can contain 40% by weight, preferably up to 20% by weight and particularly preferably up to 5% by weight of water. Water is very particularly preferably used as the sole reaction medium. To stabilize the hydrogen peroxide against decomposition, acids, the pK _a value of which is preferably smaller than that of acetic acid, in particular mineral acids, such as sulfuric acid, phosphoric acid or hydrochloric acid, are added to the reaction medium. The acid concentration is generally at least 10 ^-4 mol / liter, preferably 10 ^-3 to 10 ^-1 mol / liter. Furthermore, traces of bromide or chloride are generally added in concentrations of 1 to 1000 ppm, preferably 5 to 700 ppm and particularly preferably 50 to 600 ppm. However, other stabilizers, such as. B. formaldehyde can be used.

The reaction gas, which in addition to hydrogen and oxygen can also contain inert gases such as nitrogen or noble gases, generally has 0 ₂ : H ₂ ratios in the range from 2: 1 to 1000: 1. Molar ratios in the range from 5: 1 to 100: 1, in particular 20: 1 to 100: 1, are preferably used. The oxygen used in the reaction gas can also be added to the reaction gas in the form of air.

In a preferred embodiment, the reaction gas is circulated. In this case, the molar ratio in the fresh gas mixture is close to the stoichiometry, preferably in the range from 1.5: 1 to 0.5: 1. The molar ratio 0 ₂ : H ₂ in the cycle gas should be in the range from 5: 1 to 1000: 1, preferably in the range from 20: 1 to 100: 1. The reaction can be carried out at normal pressure and also under excess pressure up to 200 bar. The pressure is preferably 10 to 300 bar, in particular 10 to 80 bar. The reaction temperature can be in the range from 0 to 80 ° C., preferably in the range from 5 to 60 ° C. and in particular from 25 to 55 ° C. The partial pressures of the reaction gases in the reaction gas mixture in the reactor and in the cycle gas are preferably selected such that the hydrogen concentration is below the lower explosion limit under reaction conditions.

The described process can be used to produce hydrogen peroxide solutions with hydrogen peroxide contents above 2% by weight, preferably in the range from 3 to 25% by weight. The concentration can be preselected in the desired manner by adjusting the material flows. The selectivity of the hydrogen peroxide education lies z. B. above 65%, preferably> 70%. Long-term studies have shown that even after more than 40 days of operation, there is no or only a slight decrease in the catalyst activity and selectivity.

Another object of the invention is a method for catalytic reduction by reacting an inorganic or organic compound containing at least one hydrogen acceptor group with hydrogen, the reaction taking place in the presence of at least one catalyst according to the invention, as described above.

The catalysts of the invention are preferably suitable for the hydrogenation of carbon-carbon double and triple bonds.

The invention is illustrated by the following, non-limiting examples.

Examples

I. catalyst Preparation

Catalyst 1:

850 ml of glass balls made of soda-lime glass with a diameter of 1 mm are mixed with 850 ml of silicon carbide sand in a rotating flask for 24 hours. The balls are poured onto a suction filter with a perforated plate and the sand is washed out with water. Afterwards, place them on the built-in glass balls on a G3 nutsche. The glass spheres treated in this way had a pore volume which was below the limit of quantification of the Hg porosimetry and a BET surface area of 0.024 m ² / g. A solution of 10 g of tin (II) chloride and 20 ml of concentrated hydrochloric acid in 2 l of water is made up and allowed to seep through the glass spheres in 2 minutes. Then it is rinsed with 2 l of water. A solution of 0.4 g of palladium chloride and 2 ml of concentrated hydrochloric acid in 2 l of water is then allowed to seep through the glass ball layer again in 2 minutes and is then rinsed again with water. The entire procedure is repeated five more times. The activated spheres are then dried overnight at 75 ° C. and 100 mbar.

A third of the activated glass balls are filled into a double-walled glass tube 1 m long and 2.2 cm in diameter. To the Glass tube is connected to a hose pump for circulating liquid and a thermostat for heating via the jacket. A solution of 14.2 g sodium hypophosphi, 32.8 g ammonium chloride and 47.5 ml 25% ammonia in 412 ml water is poured into the tube, the circulation pump is switched on and the thermostat is heated to an internal temperature of 58 ° C , A solution of 265 mg sodium tetrachloropalladate and 1 mg hexachloroplatinic acid in 10 ml water is then added. The glass spheres turn black immediately with violent gas evolution. After 5 minutes, the liquid is drained off, rinsed with water and dried overnight at 75 ° C. and 100 mbar. An analysis shows that 87.4% of the palladium on offer and 77% of the platinum have deposited on the carrier. The coating process is repeated with a further third of the activated carrier. Finally, all three portions of catalyst 1 are mixed.

Catalyst 2:

Roughening and activation with tin and palladium are repeated as described for catalyst 1 with glass balls made of soda-lime glass with a diameter of 2 mm. The roughened glass spheres had a pore volume determined by mercury porosimetry of 0.005 ml / g and a BET surface area of 0.018 m ² / g.

270 ml of the activated glass balls are filled into the coating tube. A solution of 32.4 g of sodium hypophosphite, 72.9 g of ammonium chloride and 108 ml of 25% ammonia in 540 ml of water is added, and the mixture is heated to 42 ° C. while being pumped over. A solution of 542 mg of sodium tetrachloropalladate and 2.05 mg of hexachloroplatinic acid in 17 ml of water is then added and the mixture is heated to 46 ° C. with further stirring. After 5 minutes, the liquid is drained off and the supported catalyst is rinsed with water. The catalyst is then dried overnight at 75 ° C and 100 mbar. The process is repeated two more times and the three portions are mixed to form catalyst sample 2.

Catalyst 3:

1 mm glass balls are roughened and activated as described for catalyst 1.

270 ml of the activated glass balls are filled into the coating tube. A solution of 168 mg of sodium tetrachloropalladate and 0.70 mg of hexachloroplatinic acid, 80 mg of sodium tungstate, 30.6 g of ammonium chloride and 45 ml of 25% ammonia in 438 ml of water is added. water and heated to 42 ° C with circulation. A solution of 13.6 g of sodium hypophosphite in 14.6 g of water is then added and the mixture is further heated to 46 ° C. After 5 minutes, the solution is drained off and rinsed with water. The subsequent analysis 5 shows that 88% of the palladium and 39% of the platinum have deposited. The process is repeated in the same way with the other two thirds of the activated support, and then the three parts are combined to give catalyst 3. The analysis showed a palladium content of 180 mg / kg. 10

Catalyst 4:

The process described for the preparation of catalyst 1 is repeated with the platinum acid omitted. The analysis showed

15 a content of 115 mg / kg palladium.

Catalyst 5:

20 The procedure described for the preparation of catalyst 3 is repeated with the omission of the roughening step. The analysis showed a content of 210 mg / kg palladium.

Catalyst 6:

25

The process described for the preparation of catalyst 3 is repeated ^* , the surface not being roughened mechanically but by etching with hydrofluoric acid.

30

Catalyst 7:

220 ml 1 mm diameter glass balls are roughened and activated as described for catalyst 1. The carrier will then

35 ßend in the coating tube with a solution of 187.2 mg ruthenium chloride and 10 ml of 25% ammonia in 200 ml of water and heated to 27 ° C with circulation. A solution of 200 mg of sodium borohydride in 10 ml of water is added in two portions. After 20 minutes, the mixture is heated to 40 ° C. and others

40 circulated for 15 minutes at this temperature. After draining the liquid, the catalyst is washed with water and dried at 75 ° C and 100 mbar.

The analysis shows that 87% of the ruthenium offered was deposited on the carrier. Catalyst 8: Comparative example with a porous support

375 ml of spheres of α-alumina having a diameter of 1 to 1.5 as described for Catalyst 1 with tin and Pal- ⁵ ladium activated mm. They are then filled into the tubular reactor and mixed with a solution of 41.9 g ammonium chloride, 18.6 g sodium hypophosphite and 62 ml 25% ammonia in 600 ml water and heated to 60 ° C. A solution of 346 mg of sodium tetrachloropalladate and 1.5 mg of hexachloroplatinic acid in 10 13 ml of water is added and the mixture is warmed to 40.degree. After 10 minutes, the liquid is drained off and the catalyst is washed with water.

The procedure is repeated once more and the two portions are combined to form catalyst 8.

15

Catalyst 9:

700 ml spheres of split steatite (with a pore volume of 0.011 ml / g determined by Hg porosimetry and a BET surface area of 0.031 m ² / g) with a diameter of 2-3 mm are described twice as for catalyst 1 treated with palladium chloride and tin chloride. 340 ml of the activated balls are filled into the coating reactor. After adding a solution 25 of 18.6 g of sodium hypophosphite, 41.9 g of ammonium chloride and 62 ml of 25% ammonia in 500 ml of water, the mixture is heated to 29 ° C. while being pumped over. A solution of 83.4 mg of sodium tetrachloropalladate and 4.8 mg of hexachloroplatinic acid in 8 ml of water is then added and the mixture is circulated further. After 15 minutes, the liquid is drained off, the catalyst is rinsed salt-free with water and dried at 75 ° C. in vacuo. The process is repeated once more and then both portions are mixed to form catalyst 9. Analysis shows that 95% of the palladium and 100% of the platinum have deposited on the support.

35

Catalyst 10:

700 ml balls made of steatite with a diameter of 1.5 - 2.5 mm (with a pore volume below the limit of determination of the mercury

40 porosimetry and a BET surface area of 0.005 m ² / g) are treated twice with palladium chloride and tin chloride as described for catalyst 1. 340 ml of the activated balls are filled into the coating reactor. After adding a solution of 18.6 g sodium hypophosphite, 41.9 g ammonium chloride and 62 ml

45 25% ammonia in 500 ml of water is heated to 44 ° C while pumping over. Then a solution of 83.4 mg sodium tetrachloropalladate and 4.8 mg hexachloroplatinic acid in 8 ml of water added and the mixture circulated further. After 20 minutes, the liquid is drained off, the catalyst is rinsed salt-free with water and dried at 75 ° C. in vacuo. The process is repeated once more and then both portions are mixed to form catalyst 10.

Catalyst 11:

740 ml (447 g) polystyrene extrudates measuring 1 mm in diameter and 1.1 mm in length (with a pore volume below the limit of quantification of mercury porosimetry and a BET surface area of 0.029 m ² / g) are mixed in as described for catalyst 1 Tin and palladium activated. Half of the carrier is then filled into the coating reactor and mixed with a solution of 18.6 g sodium hypophosphite, 41.9 g ammonium chloride and 62 ml 25% ammonia in 620 ml water and heated to 42 ° C. A solution of 346 mg of sodium tetrachloropalladate and 1.43 mg of hexachloroplatinic acid in 10 ml of water is then added with pumping. After 10 minutes, the solution is drained off and washed with water. The second half of the activated carrier is mixed with the same chemicals as above in a stirred flask, stirring at 45 ° C. at 1000 rpm. The catalyst is filtered off and washed with water. Both parts are mixed and dried at 50 ° C and 100 mbar. The analysis showed that the precious metals were separated quantitatively. The analysis shows a palladium content of 285 mg / kg.

Catalyst 12:

840 ml of 3 mm pellets made of a polyamide 6 (Ultramid® B3 from BASF AG) (with a pore volume below the limit of determination of the mercury porosimetry and a BET surface area of 0.027 m ² / g) are described with tin as described for catalyst 1 and activated palladium. 240 ml of the pellets are filled into the coating tube and mixed with a solution of 9.6 g sodium hypophosphite, 21.6 g ammonium chloride and 32 ml 25% ammonia in 160 ml water and heated to 45 ° C. A solution of 137 mg of sodium tetrachloropalladate and 0.52 mg of hexachloroplatinic acid in 10 ml of water and then 67.7 mg of sodium tungstate in 5 ml of water are then added with pumping. After 25 minutes, the solution is drained off and washed with water. The coating process is repeated with the remaining activated carrier (in 2 portions). Finally, all three portions of the catalyst 12 are mixed. Catalyst 13:

750 ml of 3 mm Raschig rings made of glass (with a pore volume determined by mercury porosimetry of 0.036 ml / g and a BET surface area of 0.034 m ² / g) are activated with tin and palladium as described for catalyst 1. A third of the activated Raschig rings are filled into a double-walled glass tube 1 m long and 2 cm in diameter. A peristaltic pump for circulating liquid and a thermostat for heating are attached to the glass tube

10 connected via the jacket. A solution of 15.6 g sodium hypophosphite, 35.1 g ammonium chloride and 52 ml 25% ammonia in 430 ml water is poured into the tube, the circulation pump is switched on and the thermostat is heated to an internal temperature of 46 ° C. Then add a solution of 250 mg sodium te-

15 trachloropalladate and 1.1 mg hexachloroplatinic acid in 10 ml water. with violent gas evolution, the glass rings turn black immediately. After 5 minutes, the liquid is drained off, rinsed with water and dried overnight at 75 ° C. and 100 mbar. The coating process is carried out with a further third of each

20 activated carrier repeated. Finally, all three portions of the catalyst 13 are mixed. The analysis shows a content of 155 mg / kg palladium.

"Catalyst 14:25

5 mm glass balls made of soda-lime glass are roughened and activated as with catalyst 1. 115 ml of the activated glass balls are filled into the coating tube. A solution of 6.8 g is added

30 sodium hypophosphite, 15.3 g of ammonium chloride and 23 ml of 25% ammonia in 228 ml of water are added and the temperature is raised to 25 ° C. while pumping over. A solution of 38.8 mg of sodium tetrachloropalladate in 3.8 ml of water is then added and pumped further. After 12 minutes the liquid is drained and the carrier catalyst

35 rinsed with water. The catalyst is then dried overnight at 75 ° C and 100 mbar. The coating is repeated with a further 115 ml of the activated glass balls, and both portions are mixed to form catalyst 14. The palladium content of the catalyst is 71 mg / kg.

40

Catalyst 15:

100 ml balls of steatite with a diameter of 1.5-2.5 mm are treated twice with palladium chloride and tin chloride as described for catalyst 1. The activated balls are filled into the coating reactor. After adding a solution of 40 mg hexachloroplatinic acid (as a 1% solution in water) 21.6 g Ammonium chloride and 32 ml of 25% ammonia in 220 ml of water are heated to 24 ° C. while pumping over. A solution of 200 mg of sodium borohydride in 7 ml of water is then added in two portions and the mixture is circulated further. After 40 minutes, the liquid is drained off, the catalyst is rinsed salt-free with water and dried at 75 ° C. in vacuo. The analysis shows that 60% of the platinum has deposited on the carrier.

II. Application properties

The properties of the catalysts were checked in the direct synthesis of hydrogen peroxide from hydrogen and oxygen (Examples B1 to B19) and in the hydrogenation of 2-ethylanthraquinone and hydrodehydrolinalool (Examples B20 and B21).

Examples B1 - B9 and B1 - B19, comparative example BIO:

example 1

A double jacket reactor with an inner diameter of 2.1 cm and a length of 2 m is charged with the catalyst 1. At 40 ° C and 50 bar pressure, a solution of 5 g / 1 phosphoric acid and 120 mg / 1 hydrogen bromide in water is poured over the catalyst bed at a rate of 250 ml per hour. At the same time, with the help of a gas compressor, a mixture of 3% hydrogen and 97% oxygen is pumped from top to bottom in a circle over the catalyst bed at a rate of 10,400 Nl / h. The gas mixture is generated using two mass flow meters for hydrogen and oxygen. Its composition is determined and readjusted with the help of a thermal conductivity detector, through which a small partial flow is passed as an exhaust gas flow.

The amount of hydrogen consumed by the reaction to form hydrogen peroxide and water is calculated from the introduced mass flows of the gases and from the exhaust gas flow.

The product mixture emerging from the reaction tube is separated from the gases under pressure in a separator and is conveyed out of the system in liquid form. The mass flow is balanced against the inflow flow. The hydrogen peroxide content in the liquid discharge is determined by titration.

The selectivity becomes from the mass of the discharge stream, the content of hydrogen peroxide and the amount of hydrogen consumed calculated based on hydrogen. The space-time yield results from the amount of hydrogen peroxide formed per unit of time based on the volume of 690 ml of catalyst bed in the tubular reactor.

Examples 1 to 9 and 11 to 19 and comparative example 10 were carried out analogously to the instructions for example 1. The reaction conditions and results of the reaction are summarized in Table 1.

Table 1

As the comparative example 10 shows with the catalyst 8 not according to the invention, catalysts on a porous support according to the prior art have a significantly lower activity than the catalysts according to the invention. Example 20: Hydrogenation of 2-ethylanthraquinone

A double jacket reactor with an inner diameter of 2.1 cm and a length of 2 m is charged with the catalyst 4. At 40 ° C. and 10 bar hydrogen pressure, a solution of 13% by weight of 2-ethylanthraquinone in a mixture of 70% by weight of a hydrocarbon mixture (Shellsol®) and 30% by weight of tetrabutylurea is left at a rate of 2700 continuously pour ml / h over the catalyst bed.

The hydrogenated working solution emerging from the reaction tube is separated from the gas in a separator and conveyed out of the system in liquid form.

The gas chromatographic analysis of the working solution showed one

Conversion of 73% and a selectivity of 99.9% regarding 2-ethylanthrahydroquinone.

Example 21: Hydrogenation of hydrodehydrolmalool

Catalyst 14 (152 ml) is filled together with hydrodehydrolmalool in a double jacket tube with a diameter of 2 cm. With appropriate pumps, the liquid and hydrogen are circulated at 1.1 bar and 80 ° C with cross-sectional loads of 200 m ³ / m ² each. The acetylene alcohol is hydrogenated with a conversion rate of 15% / h and a selectivity> 98% to hydrolinalool.

Claims

claims

1. A process for the preparation of a catalyst comprising at least one platinum metal on a non-porous non-metallic

Carrier comprises, wherein the carrier is activated and at least one platinum metal is electrolessly deposited on the activated carrier, an aqueous medium comprising at least one compound or complex of a platinum metal and at least one reducing agent being brought into contact with the carrier.

2. The method of claim 1, wherein the carrier is activated by treating it with a reducing agent and a salt of a platinum metal.

3. The method according to claim 1 or 2, wherein a mineral material is used as a carrier, which is selected from ceramic materials, glasses and mixtures thereof.

4. The method according to any one of the preceding claims, wherein the surface of the carrier is roughened before activation.

5. The method according to any one of the preceding claims, wherein a carrier is used, the pore volume determined by mercury porosimetry is at most 0.1 ml / g.

6. The method according to any one of the preceding claims, wherein an aqueous medium is used for electroless deposition, which additionally contains at least one compound of a metal of the 6th,

7th or 1st subgroup, the iron group or bismuth.

7. The method according to any one of the preceding claims, wherein for the electroless deposition an aqueous medium is used which additionally comprises at least one ligand which is capable of complexing with the platinum metal.

8. The method according to any one of the preceding claims, wherein for a currentless deposition, a reducing agent with a

Standard potential of at most +0.5 V is used.

9. A catalyst obtainable by a process according to any one of claims 1 to 8.

10. platinum metal catalyst, with a non-porous non-metallic support and a catalytically active coating applied thereon, characterized in that the catalytically active coating is immobilized on the support surface.

5 siert, discrete platinum metal particles having an average particle diameter of less than about 1 micron.

11. Use of a catalyst according to claim 9 or 10 for the hydrogenation of inorganic and organic compounds.

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12. Use according to claim 11, wherein the inorganic compound is molecular oxygen and hydrogen peroxide is obtained.

13. A process for the production of hydrogen peroxide by direct synthesis, wherein a catalyst according to claim 9 or 10 is brought into contact with oxygen and hydrogen in a liquid medium.

14. The method according to claim 13, wherein the catalyst is brought into contact in a liquid medium with an oxygen-hydrogen mixture with a mixing ratio in the range from about 5: 1 to 100: 1.

15. A process for the catalytic reduction by reacting an inorganic or organic compound containing at least one hydrogen acceptor group with hydrogen, the reaction being carried out in the presence of at least one catalyst as claimed in claim 9 or 10.

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