WO2008151731A1

WO2008151731A1 - Method for producing a shell catalyst using a base or acid mixture

Info

Publication number: WO2008151731A1
Application number: PCT/EP2008/004330
Authority: WO
Inventors: Alfred Hagemeyer; Silvia Obermaier; Alice Kyriopolous
Original assignee: Süd-Chemie AG
Priority date: 2007-05-31
Filing date: 2008-05-30
Publication date: 2008-12-18
Also published as: DE102007025324A1; DE112008001479A5

Abstract

The invention relates to a method for producing a shell catalyst which comprises a porous molded catalyst support having an outer shell in which at least one metal is contained in metallic form.

Description

Process for the preparation of a coated catalyst by means of a base or acid mixture

The present invention relates to a process for the preparation of a coated catalyst comprising a porous catalyst support molding having an outer shell in which at least one metal in metallic form is contained.

Supported metal catalysts in the form of

Shell catalysts and processes for their preparation are known in the art. In metal shell catalysts, the catalytically active metals are often also the

Promoters - contain only in a more or less wide outer region (shell) of a porous catalyst support molded body, i. they do not completely penetrate the catalyst support molding (cf., for example, EP 565 952 A1, EP 634 214 A1, EP 634 209 A1 and EP 634 208 A1). With metal shell catalysts, a more selective reaction is possible in many cases than with corresponding catalysts in which the support is loaded ("impregnated") into the carrier core with the catalytically active metals.

Vinyl acetate monomer (VAM), for example, is currently produced predominantly by noble metal shell catalysts in high selectivity. The majority of currently used coated catalysts for the preparation of VAM are shelled catalysts with a Pd / Au shell on a porous amorphous ball-shaped alumosilicate support based on natural ones acid-treated calcined bentonites which have been impregnated with potassium acetate as a promoter. In the Pd / Au system of these catalysts, the active metals Pd and Au are presumably not in the form of metal particles of the respective pure metal, but rather in the form of Pd / Au alloy particles of possibly different composition, although the presence of unalloyed particles is not excluded can be.

For example, VAM shell catalysts having a Pd / Au shell are typically prepared by a so-called chemical route on which the catalyst support is reacted with solutions of corresponding metal compounds, for example, by immersing the support in the solutions or by the incipient wetness method ), in which the carrier is loaded with a solution volume corresponding to its pore volume.

The Pd / Au shell of a corresponding VAM shell catalyst is preferably produced by first impregnating the catalyst support molding in a first step with an aqueous solution of the acidic metal salt compound Na ₂ PdCl ₄ and then in a second step with the Pd component of the metal salt compound NaOH solution is fixed on the catalyst support in the form of a Pd hydroxide compound. In a subsequent separate third step, the catalyst support is then impregnated with an aqueous solution of the acidic metal salt compound NaAuCl ₄ and then the Au component also fixed by means of NaOH as a hydroxide on the support. However, it is also possible, for example, first to soak the carrier with caustic and then the

Apply metal salt compounds on the thus pretreated support. After fixing the noble metal components in an outer shell of the catalyst support of the loaded catalyst support is then largely free of chloride and Na ions washed, then dried and finally reduced at about 150 ⁰ C to 500 ⁰ C with ethylene. The Pd / Au shell thus produced usually has a thickness of up to about 500 .mu.m, with the general rule that the product selectivity of a shell catalyst is higher, the smaller the thickness of its shell.

Usually after the fixation or reduction step, the loaded with the noble metals catalyst support is loaded with potassium acetate, wherein the loading of potassium acetate is not only in the outer, loaded with precious metals shell, but the catalyst support is completely impregnated with this promoter rather.

According to the prior art, the active metals Pd and Au, starting from chloride compounds in the region of a shell of the support, are applied to same by means of impregnation and fixed by means of the bases NaOH, KOH or Na ₂ SiO ₃ . However, this technique has reached its limits in terms of minimum shell thicknesses and maximum precious metal loadings. The minimum shell thickness according to the method described VAM catalysts is about 300 microns and it is not foreseeable that even thinner shells can be obtained by the conventional method.

The object of the present invention is therefore to provide a process for the preparation of a shell catalyst comprising a porous catalyst support molding having an outer shell in which at least one metal in metallic form is contained, by means of which shell catalysts can be produced which have a relatively thin shell and Accordingly, have a higher selectivity in the catalytic reaction.

This object is achieved by methods comprising the steps of

a) providing a porous catalyst carrier shaped body;

b) loading the outer shell of the catalyst carrier shaped body with a metal salt compound

Impregnating the catalyst support molding with an acidic aqueous solution in which the

Metal salt compound, and impregnating the catalyst support molded body with a basic aqueous solution in which two or more bases different from each other are contained, the base solution causing precipitation of the metal component of the metal salt compound; or

c) loading the outer shell of the catalyst support molded body with a metal salt compound by impregnating the catalyst support molded body with a basic aqueous solution containing the metal salt compound and impregnating the catalyst support molded body with an acidic aqueous solution in which two or more acids different from each other are contained, wherein the acid solution causes precipitation of the metal component of the metal salt compound;

d) reducing the precipitated metal component in the metallic form. Surprisingly, it has been found that by means of the process according to the invention it is possible to prepare shell catalysts with relatively thin shells which have a largely uniform and high concentration of catalytically active metal over a relatively large area of their shell thickness and correspondingly lead to high selectivities in the catalytic reaction.

By precipitation of the metal component of the metal salt compound, the metal component is fixed to the molding, whereby its further diffusion into the interior of the molding prevented and it can come in accordance with rapid precipitation to form relatively thin metal shells.

Produced by the method according to the invention

Shelled catalysts have improved selectivity and relatively high activity compared to the corresponding shell catalysts known in the art because of their lower shell thickness.

The thickness of the metal shell of a shell catalyst can be optically measured by means of a microscope. The area in which the metals are deposited appears black, while the metal-free areas appear white. The borderline between metal-containing and -free areas is usually very sharp and visually clearly visible. If the abovementioned boundary line is not sharp and can not be clearly seen visually, the thickness of the shell corresponds to the thickness of a shell, measured from the outer surface of the shell

Catalyst support in which 95% of the metal deposited on the support are contained. The acid or basic metal salt solution is preferably prepared by dissolving an acid or a basic metal salt compound in water. In the context of the present invention, the term "acidic metal salt compound" or "basic metal salt compound" is understood as meaning a metal salt compound which reacts acidically or basicly when dissolved in pure water, which is noticeable by lowering or increasing the pH.

In the context of the present invention, the terms "acids" and "bases" are understood to mean substances which, on dissolution in pure water, release protons or hydroxyl ions (directly or indirectly) and lead to a corresponding change in the pH.

If the shell catalyst in the shell to contain a plurality of different catalytically active metals, for example a plurality of different active metals or an active metal and a promoter metal, the catalyst support molding can be subjected to the inventive method, for example, often accordingly. In this case, both an acidic or a basic, as well as alternately an acidic and a basic metal salt solution can be applied to the molding, wherein the impregnation step with the base solution or with the acid solution when applying several acidic or basic

Metal salt solutions in principle needs to be done only once. Alternatively, the process of the present invention may be carried out with mixed solutions containing two or more different metal salt compounds of the desired metals.

According to a preferred embodiment of the method according to the invention, it is provided that the Impregnating the catalyst support molding with the acidic metal salt solution prior to impregnation of the Katalysatorträger- molded body is carried out with the base solution or that the impregnation of the catalyst support molded body with the basic metal salt solution before impregnation of the catalyst support molded body is carried out with the acid solution. In particular, when the base solution or the acid solution causes a very rapid precipitation of the metal component of the metal salt compound is ensured by this measure, that the metal component is not undesirable exclusively precipitates on the outer surface of the molding and is fixed there, but rather at all in the molding to form a Shell can penetrate.

Alternatively, for example, in the case of using base or acid solutions which cause a relatively slow precipitation of the metal component of the metal salt compound, it may be preferable that the impregnation of the catalyst support molded body with the acidic metal salt solution is carried out after impregnation of the catalyst support molded body with the base solution or that the impregnation of the catalyst support molded body with the basic metal salt solution takes place after impregnation of the catalyst support molded body with the acid solution.

At very slow precipitation kinetics, the base solution or the acid solution can also be premixed with the respective metal salt solution and then applied as a mixed solution in a single step on the catalyst support. In addition, it is also possible, for example, to spray the base solution or the acid solution and the respective metal salt solution simultaneously onto the support by means of a two-substance nozzle or several single-substance nozzles. The bases to be used in the process according to the invention may generally be selected from both the organic and the inorganic bases, preferably selected from the inorganic bases. However, the selection of the different bases of a base solution will usually be based on the metal salt compound (solution) to be used, from which the metal component is to be precipitated by means of the bases. Thus, for example, the precipitation rate and thus the shell thickness can be controlled by the targeted selection of the base mixture as well as by the individual base concentrations or the molar ratio of the mutually different bases.

It is preferred that the inorganic bases are selected from the group consisting of the ammonium hydroxides, ammonium carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates and alkali metal silicates, preferably from the group consisting of hydrazine, NH ₄ OH, NMe ₄ OH, (NH ₄ ) ₂ CO ₃ , (NMe ₄ ) ₂ CO ₃ , (NH ₄ ) HCO ₃ , ammonium carbamate, NaOH, KOH, Na ₂ SiO ₃ , Na ₄ SiO ₄ , K ₂ SiO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , NaHCO ₃ ₃ and KHCO ₃ . It has been found that mixtures of these bases can lead to particularly thin and uniform shells.

If an acidic metal salt solution and a base solution with two mutually different bases are used in the process according to the invention, the two bases should be present in a molar ratio of 1: 5 to 5: 1 in the base solution, since the formation of thin shells is particularly pronounced in this ratio range is. It has been found that the shells obtainable by the method according to the invention are all the thinner, depending more balanced is the molar ratio of the bases used, regardless of the number of bases. According to a further preferred embodiment of the method according to the invention, it is therefore preferred that the two bases are present in a molar ratio of 1: 4 to 4: 1 in the base solution, preferably in a molar ratio of 1: 3 to 3: 1, more preferably in a molar ratio from 1: 2 to 2: 1 and most preferably in a molar ratio of 1: 1.5 to 1.5: 1.

In the case where an acidic metal salt solution and a base solution having three mutually different bases are used in the method of the present invention, the three bases should be used in a molar ratio of 1: 1: 10 to 1: 10: 1 to 10: 1: 1 in the Base solution exist because in this ratio range, the formation of thin shells is particularly pronounced. It has also been found here that the more balanced the molar ratio of the bases used, the thinner the shells obtainable by the process according to the invention, even when using three different bases. According to a further preferred embodiment of the method according to the invention, it is therefore preferred that the bases are present in a molar ratio of 1: 1: 5 to 1: 5: 1 to 5: 1: 1 in the base solution, preferably in a molar ratio of 1: 1 : 3 to 1: 3: 1 to 3: 1: 1, more preferably in a molar ratio of 1: 1: 2 to 1: 2: 1 to 2: 1: 1, and most preferably in a molar ratio of 1: 1: 1.5 to 1: 1.5: 1 to 1.5: 1: 1.

The acids to be used in the process according to the invention may, like the bases, be chosen in general from both the organic and the inorganic acids, for example in the case where the anion of the acid with the metal component of the metal salt compound is one of them insoluble precipitate formed in each case, preferably selected from the organic acids. However, the selection of the mutually different acids of the acid solution is usually carried out taking into account the metal salt compound (solution) to be used, from which the metal component is to be precipitated. Thus, for example, the precipitation rate of the metal component and thus the shell thickness can be controlled via the targeted selection of the acid mixture and also via the individual acid concentrations or the molar ratio of the mutually different acids.

Preferred inorganic acids are, for example, selected from the group consisting of the mineral acids, preferably from the group consisting of carbonic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphorous acid, hypophosphorous acid and phosphoric acid.

As organic acids, acids are selected from the group consisting of formic acid, acetic acid, propionic acid, fumaric acid, maleic acid, nitrilotriacetic acid, tartaric acid,

Polyacrylic acid, citric acid, lactic acid, benzoic acid, oxalacetic acid, glycine, oxamic acid, oxalic acid, malic acid, glycolic acid, diglycolic acid, malonic acid, ketoglutaric acid and glyoxylic acid, in particular formic acid, acetic acid, oxalic acid, since these can form insoluble compounds, for example with some noble metals in suitable solvents, which can be converted without residue into the corresponding metal oxide by means of calcination, which can easily be converted by reduction into the corresponding metallic form.

The organic and inorganic bases or acids to be used in the process according to the invention are preferably halide- and sulfate-free, in particular chloride-free, since halide and sulfate anions act as catalyst poison for a large number of catalytically active metals and can correspondingly lead to deactivation of the catalyst to be prepared.

If a basic metal salt solution and an acid solution with two mutually different acids are used in the process according to the invention, the two acids should be present in a molar ratio of 1: 5 to 5: 1 in the acid solution, since the formation of thin shells is particularly pronounced in this ratio range is. It has been found that the shells which are obtainable by means of the method according to the invention are thinner, the more balanced the molar ratio of the acids used is. According to a further preferred embodiment of the process according to the invention, it is therefore preferred that the two acids are present in a molar ratio of 1: 4 to 4: 1 in the acid solution, preferably in a molar ratio of 1: 3 to 3: 1, more preferably in one Molar ratio of 1: 2 to 2: 1, and most preferably in a molar ratio of 1: 1.5 to 1.5: 1.

In the case where a basic metal salt solution and an acid solution having three mutually different acids are used in the process according to the invention, the three acids should be used in a molar ratio of 1: 1: 10 to 1: 10: 1 to 10: 1: 1 in the Acid solution are present, since in this ratio range, the formation of thin shells is particularly pronounced. It has been found that even with the use of three mutually different acids, the shells obtainable by the process according to the invention are thinner, the more balanced the molar ratio of the acids used is. According to one further It is therefore preferred that the preferred embodiment of the process according to the invention is that the acids are present in a molar ratio of 1: 1: 5 to 1: 5: 1 to 5: 1: 1 in the acid solution, preferably in a molar ratio of 1: 1: 3 to 1 : 3: 1 to 3: 1: 1, more preferably in a molar ratio of 1: 1: 2 to 1: 2: 1 to 2: 1: 1, and most preferably in a molar ratio of 1: 1: 1.5 to 1: 1.5: 1 to 1.5: 1: 1.

In order to achieve as complete as possible precipitation of the metal component of the applied or applied to the molding metal salt compound and thereby the

If the catalyst support molding does not have to be impregnated with an excessively large volume of base solution or acid solution, the bases or the acids in the respective solution are each in a minimum concentration which is to be matched to the particular metal salt compound, for example at least in a concentration of zero , 1 to 0.4 M. On a catalyst support molded body, an amount of base solution or acid solution is often applied, in which the bases or the acids are present together at least in a simple stoichiometric ratio to the metal salt compound. The simple stoichiometric ratio is calculated according to stoichiometric rules known to the person skilled in the art.

For example, to set a simple stoichiometric ratio for 1 mole of HAuCl _4, 4 moles of OH ^{'should be used} to precipitate the Au purely theoretical completely as Au (OH) 3, namely 1 mole of OH ^" to neutralize the proton of the gold acid and 3 moles OH ^" to displace the Cl ^' ions from the AuCl ₄ ^' complex. Since some metals, especially precious metals, from certain complex compounds including chloro complexes can be very difficult to displace, it can according to a further in a preferred embodiment of the method according to the invention, the catalyst support molding is impregnated with an amount of base solution or acid solution containing 0.2 to 1.5 times the stoichiometric excess of bases or acids, based on the amount of coating applied or metal salt compound to be applied, wherein bases or acids in this case should also be present in a correspondingly high concentration. For example, to achieve a substantially complete precipitation of 1 mole of HAuCl ₄ as Au (OH) ₃ , an up to 1.5-fold excess (10 moles of OH ^" ) is generally added to the gold acid solution, for example containing a base solution 5 moles of NaOH and 5 moles of KOH in a concentration of about 0.1 to 0.4 mol / l.

It has been found that the advantageous properties of the process according to the invention are particularly pronounced, in particular in the case of the transition metals. Accordingly, it may be provided that the acidic metal salt compound or the basic metal salt compound is a corresponding compound of a transition metal.

Suitable metal salt compounds of the noble metals are suitable for carrying out the process according to the invention, in particular the noble metals Au, Ag, Pd, Pt, Re and Rh, preferably the noble metals Ag, Au, Pd and Pt.

Pd compounds which are particularly suitable for carrying out the inventive method and are therefore particularly preferred according to the invention are selected from the group consisting of Pd (NH ₃ J ₄ (OH) ₂ , Pd (NH ₃ J ₄ (OAc) ₂ , Pd (NH ₃ ) ₄ (HCO ₃ ) ₂ , Pd (NH ₃ J ₄ (HPO ₄ ), Pd (NH ₃ ) ₄ (NO ₃ ) ₂ , Pd (NH ₃ ) ₂ (NO ₂ ) ₂ , Pd (NH ₃ J ₄ Cl ₂ ,

Pd (NH ₃ J ₂ Cl ₂ , Pd (NH ₃ ) ₄ -oxalate, Pd-oxalate, PdCl ₂ , Na ₂ PdCl ₄ , K ₂ PdCl ₄ , Pd (NO ₃ J ₂ , K ₂ Pd (OAc) ₂ ( OH) ₂ , K ₂ Pd (NO ₂ J ₄ , Na ₂ Pd (NO ₂ J ₄ , Pd (OAc) ₂ , H ₂ PdCl ₄ and (NH ₄ J ₂ PdCl ₄ ₎ can also be used instead of the NH ₃ complexes the corresponding ethylenediamine (s) - or ethanolamine complexes are used.

In addition to Pd (OAc) ₂ , it is also possible to use other carboxylates of palladium, preferably the salts of the aliphatic monocarboxylic acids having 3 to 5 carbon atoms, for example the propionate or the butyrate salt.

According to a further preferred embodiment of the method according to the invention, Pd nitrite metal salt compounds may also be preferred. Preferred Pd nitrite

Metal salt compounds are, for example, those obtained by dissolving Pd (OAc) ₂ in a NaNO ₂ solution.

Au compounds which are particularly suitable for carrying out the process according to the invention and are therefore particularly preferred in the context of the present invention are selected from the group consisting of HAuCl ₄ , KAu (NO ₂ ) ₄ , NaAu (NO ₂ J ₄ , AuCl ₃ , NaAuCl ₄ , KAuCl ₄ , HAu (NO ₃ ) ₄ , Au (OAc) ₃ , KAuO ₂ , NaAuO ₂ , NMe ₄ AuO ₂ , RbAuO ₂ , CsAuO ₂ , KAu (OAc) ₃ OH, NaAu (OAc) ₃ OH, RbAu (OAc) ₃ OH, CsAu (OAc) ₃ OH and NMe ₄ Au (OAc) ₃ OH It may be advisable to use the Au (OAc) ₃ or the KAuO ₂ by means of precipitation of the oxide / hydroxide from a solution of gold acid , Washing and isolation of the precipitate and recording of the same in acetic acid or KOH fresh to set.

Pt compounds which are particularly suitable for carrying out the process according to the invention and are therefore also particularly preferred are selected from the group consisting of Pt (NH ₃ J ₄ (OH) ₂ , Pt (NO ₃ J ₂ , K ₂ Pt (OAc) ₂ (OH) ₂ , PtCl ₄ , H ₂ PtCl ₆ ,

K ₂ Pt (NO ₂ ) ₄ , Na ₂ Pt (NO ₂ J ₄ , Pt (OAc) ₂ , PtCl ₂ , Na ₂ PtCl ₄ , K ₂ PtCl ₄ , (NH ₄ ) ₂ PtCl ₄ , Pt (NH ₃ ) ₂ (NO ₂ ) ₂ , PtCl ₄ (NH ₃ J ₂ , Na ₂ Pt (OH) ₆ , K ₂ Pt (OH) ₆ , H ₂ Pt (OH) ₆ , NMe ₄ Pt (OH) ₆ , K (PtCl ₃ NH ₃ ), Pt (NH ₃ J ₄ Cl ₂ , Pt (NH ₃ ) ₄ (HCO ₃ ) ₂ , Pt (NH ₃ J ₄ (HPO ₄ ) and Pt (NH ₃ ) ₄ (NO ₃ ) ₂ .

In addition to Pt (OAc) ₂ , it is also possible to use other carboxylates of platinum, preferably the salts of aliphatic monocarboxylic acids having 3 to 5 carbon atoms, for example the propionate or butyrate salt. The acetylacetonate can also be used.

According to a further preferred embodiment of the method according to the invention, Pt-nitrite compounds may also be preferred. Preferred Pt nitrite metal salt compounds are, for example, those obtained by dissolving Pt (OAc) ₂ in a NaNO ₂ solution.

Ag compounds which are particularly suitable for carrying out the process according to the invention and are therefore preferred according to the invention are selected from the group consisting of Ag (NH ₃ ) ₂ (OH), Ag ₂ (NH ₃ ) ₂ CO ₃ , Ag (NO ₃ ) , K ₂ Ag (OAc) (OH) ₂ , Ag (NH ₃ ) ₂ (NO ₂ ), Ag (NO ₂ ), Ag-lactate, Ag-trifluoroacetate, K ₂ Ag (NO ₂ J ₃ , Na ₂ Ag ( NO ₂ ) ₃ , Ag (OAc), AgCl, Na ₂ AgCl ₃ , NH ₄ Ag oxalate, Ag (en) 0H, Ag (en) N0 ₂ , Ag (en) oxalate, Ag (NH ₃ ) ₂ - Oxalate, AgO, Ag (en) OAc, Ag (en) N0 ₃ , Ag (en) lactate, Ag ₂ (NH ₃ J ₄ CO ₃ and Ag ₂ (enJ CO ₃ .

Besides Ag (OAc) it is also possible to use other carboxylates of silver, preferably the salts of the aliphatic ones

Monocarboxylic acids having 3 to 5 carbon atoms, for example, the propionate, the butyrate or Salicylatsalz.

According to a further preferred embodiment of the method according to the invention, Ag nitrite

Metal salt compounds may be preferred. Preferred Ag nitrite compounds are, for example, those obtained by dissolving Ag (OAc) in a NaNO ₂ solution. For carrying out the process according to the invention, in addition to the noble metals, in particular the metals selected from the group consisting of Co, Ni, Mn, Cu, Zn, Cd, Mo, W and Fe are suitable, in particular from the group consisting of Co, Ni and Cu. Suitable salt compounds of these metals are selected from the carbonate, bicarbonate, hydroxide, sulfate, halide, in particular chloride, nitrate, nitrite or carboxylate compounds, in particular formate, acetate, propionate or oxalate compounds, these metals. But also the amine complexes of these metals are suitable.

The metal salt compounds to be used in the process according to the invention are preferably halide- and sulfate-free, since halide and sulfate anions act as catalyst poisons for a large number of catalytically active metals and can accordingly lead to deactivation of the catalyst to be prepared.

As catalyst supports, in the process according to the invention, in principle, porous catalyst support shaped bodies formed from all materials can be used. However, preference is given according to the invention to catalyst support molded articles based on a silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, niobium oxide or a natural layered silicate, in particular an acid-treated calcined bentonite. With regard to the production of shell catalysts with the thinnest possible shells, the best results were achieved with the metal oxide supports mentioned, in particular with catalyst support molded bodies comprising or formed from natural sheet silicates, in particular comprising or formed from acid-treated calcined bentonites. In the present context, the term "on the basis" is understood to mean that the catalyst support molding comprises the particular metal oxide The term "based on a natural layer silicate" is understood herein to mean that the catalyst support molding comprises a natural layered silicate, wherein the natural Layered silicate may be contained in both untreated and treated form in the catalyst support. Typical treatments to which a natural layered silicate can be subjected before use as a carrier material include, for example, treatment with acids and / or a

Calcination. The term "natural sheet silicate", for which the term "phyllosilicate" is also used in the literature, in the context of the present invention is understood to mean silicate mineral originating from natural sources, in which SiO ₄ tetrahedron, which is the basic structural unit of all silicates form, in layers of the general formula [Si ₂ O ₅ ] ^{2 '} are cross-linked with each other. These tetrahedral layers alternate with so-called octahedral layers, in which a cation, especially Al and Mg, is octahedrally surrounded by OH or O. For example, a distinction is made between two-layer phyllosilicates and three-layer phyllosilicates. Phyllosilicates preferred in the context of the present invention are clay minerals, in particular kaolinite, beidellite, hectorite, saponite, nontronite, mica, vermiculite and smectites, with smectites and in particular montmorillonite being particularly preferred. Definitions of the term "layered silicates" can be found, for example, in "Lehrbuch der anorganischen Chemie", Hollemann Wiberg, de Gruyter, 102nd Edition, 2007 (ISBN 978-3-11-017770-1) or in "Rompp Lexikon Chemie", 10. pad,

Georg Thieme Verlag under the term "phyllosilicate." A natural layered silicate which is particularly preferred in the context of the present invention is a bentonite, bentonites in the true sense, no natural phyllosilicates, but rather a mixture of predominantly clay minerals, in which phyllosilicates are included. In the present case, therefore, in the case where the natural sheet silicate is a bentonite, it is to be understood that the natural sheet silicate is present in the catalyst support in the form or as part of a bentonite.

A shaped catalyst carrier comprising or formed from an acid-activated calcined bentonite can be prepared by molding an acid-treated (uncalcined) bentonite and water-containing molding mixture into a molded article by means known to those skilled in the art, such as extruders or tablet presses, and then the uncured shaped body is calcined to form a stable shaped body. The size of the specific surface of the catalyst support depends in particular on the quality of the (bent) bentonite used, the acid treatment process of the bentonite used, ie, for example, the nature and the relative amount of bentonite and the concentration of the inorganic acid used, the acid treatment time and temperature, the compression pressure as well as the calcination time and temperature and the calcination atmosphere. A corresponding catalyst support having a surface area of about 160 m ² / g or 100 m ² / g is marketed by SÜD-Chemie AG under the name "KA-160" or "KA-0".

Acid-treated bentonites can be obtained by treating bentonites with strong acids, such as sulfuric acid, phosphoric acid or hydrochloric acid. A definition of the term bentonite which also applies in the context of the present invention is given in Römpp, Lexikon Chemie, 10th ed., Georg Thieme Verlag, stated. Bentonites which are particularly preferred in the context of the present invention are natural aluminum-containing sheet silicates which contain montmorillonite (as smectite) as the main mineral. After the acid treatment, the bentonite is usually washed with water, dried and ground to a powder.

It has been found that, in particular, Pd / Au coated catalysts with a particularly thin noble metal shell can be produced by means of the process according to the invention if the catalyst support molding has a surface area of 160 m ² / g or less, preferably less than 140 m ² / g, preferably one of less than 135 m ² / g, more preferably one of less than 120 m ² / g, more preferably one of less than 100 m ² / g, even more preferably one of less than 80 m ² / g and more preferably, less than 65 m ² / g, especially when the catalyst support molded body comprises or is formed from an acid-treated calcined bentonite. In the context of the present invention, the term "surface area" of the catalyst support is understood to mean the BET surface area of the support, which is determined by adsorption of nitrogen in accordance with DIN 66132.

According to a further preferred embodiment of the method according to the invention, it may be provided that the catalyst support molding has a surface area of 160 to 40 μm ² / g, preferably one of between 140 and 50 m ² / g, preferably between 135 and 50 m ² / g, more preferably one of between 120 and 50 m ² / g, more preferably between 100 and 50 m ² / g and most preferably between 100 and 60 m ² / g. In the context of the method according to the invention, the

Catalyst supports are mechanically stressed, which can lead to a certain abrasion and a certain damage of catalyst supports, in particular in the region of the resulting shell. In particular, in order to keep the abrasion of the catalyst support within reasonable limits, the catalyst support as well as the finished catalyst has a hardness of greater than or equal to 20 N, preferably one of greater than / equal to 30 N, more preferably greater than or equal to 40 N and Most preferably one of greater than or equal to 50 N. The hardness is determined by means of a

Tablet hardness tester 8M of the company Dr. med. Schleuniger Pharmatron AG on 99 pieces of moldings as an average determined after drying of the molding or the catalyst at 130 ⁰ C for ² h, the device settings are as follows:

Hardness: N

Distance to the molded body: 5.00 mm

Time delay: 0.80 s

Feed type: 6 D

Speed: 0.60 mm / s

The hardness of the catalyst or of the catalyst support can be influenced, for example, by varying certain parameters of the process for its preparation, for example by selecting the support material, the calcination time and / or the calcining temperature of an uncured molding formed from a corresponding support mixture, or by certain additives such as methyl cellulose or magnesium stearate. It may be preferred that the catalyst support molding used in the process according to the invention has an integral pore volume to BJH greater than 0.30 ml / g, preferably greater than 0.35 ml / g and preferably greater than 0, 40 ml / g. The integral pore volume of the catalyst support is determined by the method of BJH by means of nitrogen adsorption.

The surface of the catalyst support and its integral pore volume are determined by the BET method or by the BJH method. The BET surface area is determined by the BET method according to DIN 66131; a publication of the BET method can also be found in J. Am. Chem. Soc. 60, 309 (1938). To determine the surface area and the integral pore volume of the catalyst support or the catalyst, the sample can be used, for example, with a fully automatic

Nitrogen porosimeter Micromeritics, type ASAP 2010 are measured by means of which an adsorption and desorption isotherm is recorded.

To determine the surface and the porosity of the

Catalyst support or the catalyst according to the BET theory, the data are evaluated according to DIN 66131. The pore volume is determined from the measurement data using the BJH method (E.P. Barret, L.J. Joiner, P.P. Haienda, J. Am. Chem. Soc. 73 (1951, 373)). In this procedure, too

Considered effects of capillary condensation. Pore volumes of certain pore size ranges are determined by summing up incremental pore volumes, which are obtained from the evaluation of the adsorption isotherm according to BJH. The integral pore volume according to the BJH method refers to pores with a diameter of 1.7 to 300 nm. Furthermore, it may be preferred that the carrier used in the method according to the invention has an integral pore volume to BJH of between 0.25 and 0.7 ml / g, preferably one of between 0.3 and 0.6 ml / g and preferably one from 0.35 to 0.5 ml / g.

Further, it may be preferable that the catalyst carrier molded body used in the method has an average pore diameter of 8 to 50 nm, preferably one of 10 to 35 nm, and more preferably 11 to 30 nm.

According to the invention, it is preferred that the shaped body used in the process according to the invention comprises or is formed from a natural sheet silicate, since very good results with respect to thin shell thicknesses are obtained, in particular, with such supports. It may be preferred that the proportion of the catalyst support to phyllosilicate, in particular to acid-treated calcined bentonite, is greater than or equal to 50% by mass, preferably greater than or equal to 60% by mass, preferably greater than or equal to 70% by mass preferably greater than or equal to 80% by mass, more preferably greater than or equal to 90% by mass and most preferably greater than or equal to 95% by mass, based on the mass of the catalyst support.

According to a further preferred embodiment of the process according to the invention, it may be preferred, in particular if the support comprises an acid-treated calcined bentonite, if the water absorbency of the catalyst support is 40 to 75%, preferably 50 to 70% calculated as weight increase by Wasseraufnähme. The absorbency is determined by soaking 10 g of the carrier sample with deionized water for 30 minutes until no more gas bubbles escape from the carrier sample. Then that will be Decant excess water and swab the soaked sample with a cotton cloth to remove the sample from adhering moisture. Then the water-loaded carrier is weighed and the absorbency calculated according to:

(Weight (g) - weight (g)) x 10 = water absorbency (%)

In order to ensure sufficient chemical resistance of the catalyst according to the invention in the case of an acid-treated calcined bentonite, the acid-treated calcined bentonite contained in the carrier has an SiO ₂ content of at least 65% by mass, preferably at least 80% by mass and preferably a from 95 to 99.5 Mass .-% based on the mass of the bentonite contained.

It has been found that the shell thickness can be controlled by the acidity of the carrier. According to a further preferred embodiment of the method according to the invention, the catalyst support has an acidity of between 1 and 150 μval / g, preferably one of between 5 and 130 μval / g and particularly preferably one of between 10 and 100 μval / g. The acidity is determined as follows: 1 g of finely ground carrier is mixed in 100 ml of water (with a pH blank) and extracted with stirring for 15 minutes. It is then titrated with 0.01 N NaOH solution until pH 7.0. The titration is gradual; 1 ml of the NaOH solution are added dropwise (1 drop / second), maintained for 2 minutes, while reading, again 1 ml is added, etc. The blank value of the water used is determined and the acidity calculation is corrected accordingly.

The titration curve (ml 0.01 N NaOH vs. pH) is then plotted. The intersection of the titration curve with pH 7 is determined. The molar equivalents are calculated in 10 ^'6 Equiv / g carriers resulting from NaOH consumption for the pH 7 intersection.

10 ml of 0.01 N NaOH.

Total acid: = μVal / g

1 carrier

The carrier used in the method according to the invention is formed as a shaped body. In this case, the catalyst support can basically take the form of any geometric body on which a metal shell can be applied. However, it is preferred that the catalyst support as a ball, cylinder (also with rounded faces), perforated cylinder (also with rounded faces), trilobus, "capped tablet", tetralobus, ring, donut, star, cartwheel, "inverse" cartwheel, or as a strand, preferably as Rippstrang or star train is formed.

The diameter or the length and thickness of the catalyst support is preferably 2 to 9 mm, depending on the reactor tube geometry in which the resulting catalyst is to be used. If the catalyst support is designed as a sphere, then the catalyst support preferably has a diameter of greater than 2 mm, preferably a diameter of greater than 3 mm and preferably a diameter of 4 mm to 9 mm.

Suitable solvents for metal salt compounds or for the base solution or the acid solution are all aqueous solvent systems in which the selected metal salt compounds, bases or acids are soluble and which after application to the catalyst support of the same can be easily removed by drying again.

In addition, with respect to the metal salt compounds, the solvent system must be acidic or basic in nature. Be adjustable value without causing precipitation of the metal component, if, for example, by dissolving the metal salt compound, the solution does not already react directly acidic or basic. Preferred solvent for the metal salt compounds, bases and acids is pure water.

If the metal salt compound, bases or acids are not sufficiently soluble in pure water, other solvents may be used in addition to water, as well as additives. Other suitable solvents are those solvents which are inert and miscible with water. Preferred solvents which are suitable as an additive to water include ketones, for example acetone, or alcohols, for example ethanol or isopropanol or methoxyethanol. Additives which can facilitate the solubility of the corresponding compounds are alkalis, such as aqueous KOH, NaOH or Na ₂ SiO ₃ , or organic acids, such as acetic acid, formic acid, citric acid, tartaric acid, malic acid, glyoxylic acid, glycolic acid, oxalic acid, pyruvic acid or lactic acid.

If chloride compounds or sulfate compounds are used as the metal salt compound, bases or acids, it must be ensured that the chloride ions or sulfate ions are reduced to a tolerable residual amount before use of the catalyst prepared by the process according to the invention, since chloride or sulfate acts as catalyst poison. For this purpose, the catalyst support is usually washed extensively with water after fixing the metal component of the metal salt compound on the catalyst support. This is generally done either immediately after precipitation fixation of the metal component or after reduction of the metal component to the corresponding metal. In the context of the process according to the invention, however, chloride-free and sulfate-free metal salt compounds, bases or acids are preferably used, as well as chloride-free and sulfate-free solvents in order to minimize the chloride / sulfate content of the catalyst and to avoid expensive chloride / sulfate-free washing. The corresponding formate, acetate, propionate, oxalate, hydroxide, nitrite, nitrate, carbonate or bicarbonate compounds are preferably used as metal salt compounds, since these contaminate the catalyst support only to a very small extent with chloride / sulfate ,

The impregnation of the catalyst support with the metal salt compound in the region of an outer shell of the catalyst support can be achieved by processes known per se. Thus, the metal salt compound can be applied by impregnation, e.g. the carrier is immersed in an aqueous solution of the metal salt compound or soaked in the incipient wetness method. Subsequently, the base solution or the acid solution can be applied to the catalyst support, which causes a precipitation of the metal component on the catalyst support. It is also possible, for example, first to impregnate the carrier with the base solution or with the acid solution and then apply the metal salt compound to the carrier pretreated in this way.

According to a further preferred embodiment of the method according to the invention, it is therefore provided that the metal salt compound is applied to the catalyst support by the catalyst carrier is impregnated with the solution of the metal salt compound. It is also preferred that the impregnation of the catalyst support with the base solution or with the acid solution by impregnation of the carrier with the respective solution.

In particular, the metal salt compounds, but also the base solution or the acid solution can be advantageously applied to the support by means of so-called physical methods. For this purpose, the support according to the invention can preferably be sprayed, for example, with a solution of the metal salt compound, the catalyst support being moved, for example, in a coating drum.

According to a particularly preferred embodiment of the method according to the invention, it is provided that the solution of the metal salt compound is applied to the catalyst support by the solution is sprayed onto a fluidized bed or a fluidized bed of the catalyst support, preferably by means of an aerosol of the solution. As a result, the shell thickness of the resulting shell catalyst can be further minimized and optimized, for example, up to a shell thickness of less than 100 microns.

As already stated above, the impregnation of the catalyst support with the solution of the metal salt compound can be carried out by means of a conventional fluidized bed system or with a fluidized bed system. With regard to fluidized bed systems, it is particularly preferred if a so-called controlled air sliding layer can be produced in the system. On the one hand, the catalyst support shaped bodies are thoroughly mixed by the controlled air sliding layer, while at the same time rotating about their own axis and being dried uniformly by the process air. On the other hand, the catalyst support shaped bodies pass due to the consistent caused by the controlled Luftgleitschicht uniform movement of the moldings the spraying process

(Application of the metal salt compound) in almost constant frequency. As a result, a substantially uniform shell thickness of a treated batch of moldings is achieved. Furthermore, it is achieved that the metal concentration of the resulting metal shell catalyst varies only relatively small over a relatively large range of shell thickness, i. in that the metal concentration over a wide range of shell thickness describes approximately a distorted rectangular function with high metal enrichment at the outer shell boundary and corresponding metal depletion at the inner shell boundary, thereby ensuring substantially uniform activity of the resulting catalyst across the thickness of the metal shell.

Suitable drageeing drums, fluidized bed plants and fluidized bed plants are known in the art and are e.g. by the companies Heinrich Brucks GmbH (Alfeld, Germany), ERWEK GmbH (Heusenstamm, Germany), Stechel (Germany), DRIAM Anlagenbau GmbH (Eriskirch, Germany), Glatt GmbH (Binzen, Germany), GS Divisione Verniciatura (Osteria, Italy) , HOFER-Pharma Maschinen GmbH (Weil am Rhein, Germany), LB Bohle Maschinen + Verfahren GmbH (Enningerloh, Germany), Lödige Maschinenbau GmbH (Paderborn, Germany), Manesty (Merseyside,

Great Britain), Vector Corporation (Marion, IA, USA), Aeromatic-Fielder AG (Bubendorf, Switzerland), GEA Process Engineering (Hampshire, UK), Fluid Air Inc. (Aurora, Ill., USA), Heinen Systems GmbH (Varel. Germany), Hüttlin GmbH (Steinen, Germany), Umang Pharmatech Pvt. Ltd. (Marharashtra, India) and Innojet Technologies (Lörrach, Germany). Particularly preferred for the process according to the invention Fluid bed plants are sold by Innojet Technologies under the brand names Innojet ^® Aircoater and Innojet ^® Ventilus.

Accordingly, it is provided according to a further preferred embodiment of the method according to the invention that the catalyst support molding is impregnated with the acidic metal salt solution or impregnated with the basic metal salt solution by the respective solution is sprayed onto a plurality of moldings, wherein the moldings thereby circulated become.

In addition, it can be provided that the circulation of the shaped bodies is accomplished by means of generating a fluidized bed or a fluidized bed of the shaped bodies, wherein the shaped bodies in the fluidized bed preferably circulate elliptically or toroidally. To give an idea of how the moldings move in such fluid beds, it should be understood that in "elliptical circulation" the catalyst support moldings in the fluidized bed move in a vertical plane on an elliptical orbit of varying major and minor axis sizes. In "toroidal recirculation", the catalyst support moldings in the fluidized bed move in the vertical plane on an elliptical orbit of varying majorities of the major and minor axes and in the horizontal plane on a circular orbit of varying size of radius. On average, in elliptical orbit, the molded bodies move in a vertical plane on an elliptical trajectory, in toroidal orbit on a toroidal trajectory, i.e., a shaped body helically travels down the surface of a vertical elliptical-shaped torus.

Furthermore, it may be preferred in the context of the present invention that the catalyst support molding with the Base solution is impregnated or impregnated with the acid solution by the respective solution is sprayed onto a plurality of moldings, wherein the moldings are thereby circulated. Analogous to the order of

Metal salt compound it may also be preferred that the circulation of the moldings is accomplished by means of generating a fluidized bed or a fluidized bed of the moldings, wherein the moldings in the fluidized bed preferably rotate toroidal (s.o.).

After precipitation of the metal component of the metal salt compound on the catalyst support, the support may be calcined to convert the metal component into an oxide. The calcination is carried out depending on the nature of the precipitate, but preferably at temperatures of less than 700 ⁰ C, more preferably between 300-450 ⁰ C with access of air. The calcination time depends on the calcining temperature and the nature of the precipitated metal compound, and is preferably selected in the range of 0.5-6 hours. At a calcination temperature of about 400 ^° C., the calcination time for the precipitates is Pd (OH) ₂ and Au (OH) _{3 is} preferably 1-2 hours. At a calcination temperature of 300 ^° C., the calcining time in this respect is preferably up to 6 hours.

The applied metal component is reduced before the use of the shell catalyst, wherein the reduction in situ, ie in the process reactor, or ex situ, ie in a special reduction reactor, can be performed. The reduction in situ is carried out in particular in the case of noble metals, preferably with ethylene (5% by volume) in nitrogen at a temperature of about 150 ^° C. over a period of, for example, 5 hours. The reduction ex situ can be carried out, for example, with 5% by volume of hydrogen in nitrogen, For example, be carried out by means of forming gas, at temperatures in the range of preferably 150-500 ⁰ C over a period of 5 hours.

Gaseous or vaporizable reducing agents such as CO, NH ₃ , formaldehyde, methanol and

Hydrocarbons may also be used, which gaseous reducing agents may also be diluted with inert gas such as carbon dioxide, nitrogen or argon. Preferably, an inert gas diluted reducing agent is used. Preference is given to mixtures of

Hydrogen with nitrogen or argon, preferably with a hydrogen content between 1 vol .-% and 15 vol .-%.

The reduction of the metal component can also be carried out in the liquid phase, preferably by means of

Reducing agents hydrazine, K-formate, H ₂ O ₂ , Na-hypophosphite, Na-formate, ammonium formate, formic acid, K-hypophosphite or hypophosphorous acid.

The amount of reducing agent is preferably selected so that at least the equivalent necessary for complete reduction of the metal component is passed over the resulting catalyst during the treatment period. Preferably, however, an excess of reducing agent is passed over the resulting catalyst to ensure rapid and complete reduction.

Preferably, it is depressurized, ie at an absolute pressure of about 1 bar, reduced. For the production of technical amounts of catalyst according to the process of the invention, a rotary kiln or fluidized bed reactor is preferably used for the reduction in order to ensure a uniform reduction of the catalyst. A preferred method according to the invention comprises, for example, the steps:

a) providing a porous Katalysatorträger- shaped body, preferably comprising a natural layered silicate; b) impregnating the catalyst support molding with an acidic aqueous solution in which at least one salt compound of at least one noble metal is dissolved; c) impregnating the catalyst support molded body with a basic aqueous solution in which two or more bases different from each other are contained for precipitating the noble metal component (s); d) transferring the precipitated noble metal component (s) into the metallic form.

Another preferred method according to the invention comprises, for example, the steps:

a) providing a porous Katalysatorträger- shaped body, preferably comprising a natural layered silicate; b) impregnating the catalyst support molding with an acidic aqueous solution in which a Pd and / or Au

Salt compound dissolved, preferably HAuCl ₄ , Na ₂ PdCl ₄ or HAuCl ₄ and Na ₂ PdCl ₄ . c) impregnating the catalyst support molding with a basic aqueous solution in which at least KOH and NaOH, KOH and Na ₂ SiO ₃ or NaOH and Na ₂ SiO _{3 are dissolved} as bases, for the precipitation of the noble metal component (s); d) transferring the precipitated noble metal component (s) into the metallic form.

The present invention further relates to the use of a basic solution in which Na ₂ SiO _{3 is dissolved} as a single base, for precipitating the noble metals Pd and / or Au from a precious metal precursor / ene-containing solution, in particular in the preparation of coated catalysts , The precipitation with a solution in which only Na ₂ SiO _{3 is} contained as base also leads to thin Au, Pd or Au and Pd-containing shells.

The following description of exemplary embodiments and a comparative example serves to explain the invention.

Example 1:

40 g of catalyst support molding from Süd-Chemie AG with the designation KA-160 (geometric shape: spheres, diameter: 5 mm, material: calcined acid-treated bentonite) were prepared by the incipient wetness method with a mixed solution of 2.23 g of a 15.87% (based on Pd) Na ₂ PdCl ₄ solution, 0.50 g of a 31.36% (based on Au) HAuCl ₄ solution and 20.57 g of water impregnated.

After the mixed solution had been taken up by the shaped bodies, the mixed solution was allowed to act on the supports for a further 30 minutes. Thereafter, the molded articles were immersed in 88 g of a 0.132 molar NaOH and 0.132 molar KOH solution, and the base solution was allowed to act on the supports for 23 hours.

After base fixation, the base solution was decanted off and the catalyst supports were used to reduce the Pd and Au components for a period of 3.75 h with 26 ml of a 2 molar aqueous NaH ₂ PO ₂ solution, then washed extensively with water and dried. Thereafter, the thus obtained coated catalysts were impregnated with potassium acetate.

The precious metal shell of the shell catalysts produced in this way have a thickness of 241 μm on average.

Comparative Example 1

Coated catalysts were prepared analogously to Example 1 with the exception that 88 g of a 0.264 molar NaOH solution was used as the base solution.

The noble metal shell of the shell catalysts produced in this way have a thickness of on average 340 μm.

Example 2:

20 g of catalyst support molding from Süd-Chemie AG with the designation KA-160 (see above) were mixed by Incipient Wetness method with a mixed solution of 1.10 g of a 15.87% (based on Pd) Na ₂ PdCl ₄ solution, 0.21 g of a 31.36% (based on Au) HAuCl ₄ solution and 11.53 g of water impregnated.

After the mixed solution had been taken up by the shaped bodies, the mixed solution was allowed to act on the supports for a further 25 minutes. Thereafter, the molded articles were immersed in a mixture of 14.24 g of 0.35 molar NaOH solution and 7.12 g of 0.35 molar Na ₂ SiO ₃ solution, and the base solution was allowed to act on the supports for 21.5 hours.

After base fixation, the base solution was decanted off and the catalyst supports were used to reduce the Pd and Au components treated with 26.68 g of a 10% aqueous NaH ₂ PO ₂ solution for a period of 2 h, then washed extensively with water and dried. Thereafter, the thus obtained coated catalysts were impregnated with potassium acetate.

The noble metal shell of the shell catalysts produced in this way have a thickness of on average 209 μm.

Example 3:

Coated catalysts were prepared analogously to Example 2 with the exception that a mixture of 8.54 g of 0.35 molar NaOH solution and 9.97 g of 0.35 molar Na ₂ SiO ₃ solution was used as the base solution.

The noble metal shell of the shell catalysts produced in this way have a thickness of 200 μm on average.

Claims

claims

A process for producing a coated catalyst comprising a porous catalyst support molded body having an outer shell in which at least one metal in metallic form is contained, comprising the steps of

a) providing a porous catalyst carrier shaped body;

b) loading the outer shell of the catalyst support molded body with a metal salt compound by impregnating the catalyst support molded body with an acidic aqueous solution containing the metal salt compound and impregnating the catalyst support molded body with a basic aqueous solution in which two or more bases different from each other are contained, the base solution causing precipitation of the metal component of the metal salt compound; or

d) reducing the precipitated metal component in the metallic form.

2. The method according to claim 1, characterized in that the impregnation of the catalyst support molded body with the acidic metal salt solution prior to impregnation of the catalyst support molded body with the base solution takes place or that the impregnation of the catalyst support molded body with the basic metal salt solution prior to impregnation of the catalyst support Molded article with the acid solution.

3. The method according to any one of the preceding claims, characterized in that the bases are selected from the organic and / or from the inorganic bases, preferably from the inorganic bases.

4. The method according to claim 3, characterized in that the inorganic bases are selected from the group consisting of the ammonium hydroxides, ammonium carbonates,

Alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates and the alkali metal silicates, preferably from the group consisting of NaOH, KOH, NMe ₄ OH, (NMe 4) 2CO 3, Na ₂ SiO ₃ , Na ₄ SiO ₄ , K ₂ SiO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , NaHCO ₃ and KHCO ₃ .

5. The method according to any one of the preceding claims, characterized in that the base solution comprises two mutually different bases, which are present in a molar ratio of 1: 5 to 5: 1 in the base solution.

6. The method according to any one of the preceding claims, characterized in that the base solution comprises three mutually different bases, which are present in a molar ratio of 1: 1: 10 to 1: 10: 1 to 10: 1: 1 in the base solution.

7. The method according to any one of the preceding claims, characterized in that the acids are selected from the organic and / or from the inorganic acids.

8. The method according to claim 7, characterized in that the inorganic acids are selected from the group consisting of the mineral acids, preferably from the group consisting of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

9. The method according to any one of the preceding claims 7 to 8, characterized in that the organic acids are selected from the group consisting of formic acid, acetic acid, propionic acid, fumaric acid, maleic acid, nitrilotriacetic acid, tartaric acid, polyacrylic acid, citric acid, lactic acid, benzoic acid, oxaloacetic acid, Glycine, oxamic acid, oxalic acid, malic acid, glycolic acid, diglycolic acid, malonic acid, ketoglutaric acid and glyoxylic acid.

10. The method according to any one of the preceding claims 7 to 9, characterized in that the acid solution comprises two mutually different acids which are present in a molar ratio of 1: 5 to 5: 1 in the acid solution.

11. The method according to any one of the preceding claims 7 to 10, characterized in that the acid solution comprises three mutually different acids which are present in a molar ratio of 1: 1: 10 to 1: 10: 1 to 10: 1: 1 in the acid solution ,

12. The method according to any one of the preceding claims, characterized in that the catalyst support molding is impregnated with an amount of base solution or acid solution, which is 0.2 to 1.5 times stoichiometric Excess of bases or acids contains, based on the amount of metal salt compound applied or to be applied.

13. The method according to any one of the preceding claims, characterized in that the metal salt compound a

Transition metal salt compound is.

14. The method according to claim 13, characterized in that the transition metal salt compound is a noble metal salt compound, preferably a

Salt compound of a noble metal selected from the group consisting of Au, Ag, Pd, Re, Rh and Pt.

15. The method according to claim 14, characterized in that the noble metal compound is a Pd compound selected from the group consisting of Pd (NH ₃ J ₄ (OH) ₂ , Pd (NH ₃ J ₄ (OAc) ₂ / Pd (NH ₃ J ₄ (HCO ₃ J ₂ , Pd (NH ₃ J ₄ (HPO ₄ ), Pd (NH ₃ J ₄ (NO ₃ J ₂ , Pd (NH ₃ J ₂ (NO ₂ J ₂ , Pd (NH ₃ J ₄ Cl ₂ , Pd (NH ₃ J ₂ Cl ₂ , Pd (NH ₃ ) ₄ -oxalate, PdCl ₂ , Na ₂ PdCl ₄ , K ₂ PdCl ₄ , Pd (NO ₃ ) ₂ , K ₂ Pd (OAc) ₂ (OH) ₂ , K ₂ Pd (NO ₂ J ₄ , Na ₂ Pd (NO ₂ J ₄ , Pd (OAc) ₂ , H ₂ PdCl ₄ and (NH ₄ J ₂ PdCl ₄ .

16. The method according to claim 14 or 15, characterized in that the noble metal compound is an Au compound selected from the group consisting of HAuCl ₄ , KAu (NO ₂ J ₄ , NaAu (NO ₂ J ₄ , AuCl ₃ , NaAuCl ₄ , KAuCl ₄ ,

HAu (NO ₃ J ₄ , Au (OAcJ ₃ , KAuO ₂ , NaAuO ₂ , NMe ₄ AuO ₂ , RbAuO ₂ , CsAuO ₂ , KAu (OAc) ₃ OH, NaAu (OAc) ₃ OH, RbAu (OAc) ₃ OH, CsAu (OAc) ₃ OH and NMe ₄ Au (OAc) ₃ OH.

17. The method according to claim 14, 15 or 16, characterized in that the noble metal compound is a Pt compound selected from the group consisting of Pt (NH ₃ ) ₄ (OH) ₂ , Pt (NO ₃ ) ₂ , K ₂ Pt ( OAc) ₂ (OH) ₂ , PtCl ₄ , K ₂ Pt (NO ₂ J ₄ , Na ₂ Pt (NOs) ₄ , Pt (OAc) ₂ , PtCl ₂ , Na ₂ PtCl ₄ , K ₂ PtCl ₄ , Pt (NH ₃ ) ₂ (NO ₂ ) ₂ , PtCl ₄ (NH ₃ ) ₂ , Na ₂ Pt (OH) ₆ , K ₂ Pt (OH) ₆ , H ₂ Pt (OH) ₆ , NMe ₄ Pt (OH) ₆ , K (PtCl ₃ NH ₃ ), Pt (NH ₃ ) ₄ Cl _{2 /} Pt (NH ₃ ) ₄ (HCO ₃ ) ₂ , Pt (NH ₃ J ₄ (HPO ₄ ), Pt (NH ₃ J ₄ (OH) ₂ and Pt (NH ₃ ) ₄ (NO ₃ ) ₂ .

18. The method according to any one of claims 14 to 17, characterized in that the noble metal compound is an Ag compound selected from the group consisting of Ag (NH ₃ J ₂ (OH), Ag ₂ (NH ₃ J ₂ CO ₃ , Ag ₂ (NH ₃ ) ₄ CO ₃ , Ag (NO ₃ ), K ₂ Ag (OAc) (OH) ₂ , Ag (NH ₂ ) ₂ (NO ₂ ), Ag (NO ₂ ), Ag lactate, ag trifluoroacetate, K ₂ Ag (NO ₂ J ₃ , Na ₂ Ag (NO ₂ ) ₃ , Ag (OAc), AgCl,

Na ₂ AgCl ₃ , NH ₄ Ag oxalate, Ag (en) OH, Ag (en) NO ₂ , Ag (en) oxalate, Ag (NH ₃ ) ₂ oxalate, AgO ₂ , Ag (en) OAc, Ag (EN) NO ₃ , Ag (en) lactate and Ag ₂ (en) CO ₃ .

19. The method according to claim 13, characterized in that the transition metal salt compound is a compound of one of the metals selected from the group consisting of Co, Ni, Mn, Cu, Zn, Cd, Mo, W and Fe, in particular from the group consisting of Co, Ni and Cu.

20. The method according to claim 19, characterized in that the transition metal salt compound of the selected group of metals is a carbonate, bicarbonate, hydroxide, sulfate, halide, in particular chloride, nitrate, nitrite or carboxylate compound, in particular a formate Acetate, propionate or oxalate compound, is one of these metals.

21. The method according to any one of the preceding claims, characterized in that the catalyst support molded body is formed on the basis of a silicon oxide, alumina, zirconia, titanium oxide, niobium oxide or a natural phyllosilicate.

22. The method according to any one of the preceding claims, characterized in that the catalyst carrier molded body has a surface area of less than / equal to 160 m ² / g, preferably a smaller than 140 m ² / g, preferably a smaller than 135 m ² / g, more preferably one of less than 120 m ² / g, more preferably one of less than 100 m ² / g, even more preferably one of less than 80 m ² / g and particularly preferably one of less than 65 m ² / g ,

23. The method according to any one of the preceding claims, characterized in that the catalyst carrier molded body has a surface area of 160 to 40 m ² / g, preferably one of between 140 and 50 m ² / g, preferably one of between 135 and 50 m ² / g, more preferably one of between 120 and 50 m ² / g, more preferably between 100 and 50 m ² / g and most preferably between 100 and 60 m ² / g.

24. The method according to any one of the preceding claims, characterized in that the catalyst or the catalyst carrier molded body has a hardness of greater than or equal to 20 N, preferably one of greater than / equal to 30 N, more preferably one of greater than or equal to 40 N and most preferably one of greater than or equal to 50 N.

25. The method according to any one of the preceding claims, characterized in that the proportion of Katalysatorträger- shaped body of natural phyllosilicate, in particular on acid-treated calcined bentonite, greater / equal to 50 mass .-%, preferably greater than / equal to 60 mass .-%, preferably greater than or equal to 70% by mass, more preferably greater than or equal to 80% by mass, more preferably greater than or equal to 90% by mass, and most preferably greater than or equal to 95% by mass, based on the mass of the catalyst support.

26. The method according to any one of the preceding claims, characterized in that the catalyst support molded body has an acidity of between 1 and 150 μval / g, preferably one of between 5 and 130 μval / g and particularly preferably one of between 10 and 100 μval / G.

27. The method according to any one of the preceding claims, characterized in that the catalyst carrier molded body as a ball, cylinder, perforated cylinder, trilobus, ring, star or strand, preferably as a rib strand or star strand, is formed.

28. The method according to any one of the preceding claims, characterized in that the catalyst carrier shaped body is designed as a ball with a diameter of greater than 2 mm, preferably with a diameter of greater than 3 mm and preferably with a diameter of greater than 4 mm.

29. The method according to any one of the preceding claims, characterized in that the catalyst carrier-shaped body is impregnated with the acidic metal salt solution or impregnated with the basic metal salt solution by the respective solution is sprayed onto a plurality of moldings, wherein the moldings are thereby circulated ,

30. The method according to claim 29, characterized in that the circulation of the shaped body is accomplished by means of generating a fluidized bed or a fluidized bed of the shaped body, wherein the shaped bodies in the fluidized bed preferably rotate toroidally.

31. The method according to any one of the preceding claims, characterized in that the catalyst support molding is impregnated with the base solution or impregnated with the acid solution by the respective solution is sprayed onto a plurality of moldings, wherein the moldings are thereby circulated.

32. The method according to claim 31, characterized in that the circulation of the moldings is accomplished by means of generating a fluidized bed or a fluidized bed of the moldings, wherein the moldings in the fluidized bed preferably rotate toroidally.