EP1720656A1

EP1720656A1 - Preparation of metal/metal oxide supported catalysts by precursor chemical nanometallurgy in defined reaction chambers of porous supports using organometallic and/or inorganic precursors and reductants containing metal

Info

Publication number: EP1720656A1
Application number: EP05707729A
Authority: EP
Inventors: Richard Fischer; Roland Fischer; Ralf Becker; Kai-Olaf Hinrichsen; Martin Muhler
Original assignee: Sued Chemie AG
Current assignee: Sued Chemie IP GmbH and Co KG
Priority date: 2004-03-09
Filing date: 2005-03-08
Publication date: 2006-11-15
Also published as: RU2006132354A; MY141786A; DE102004011335A1; BRPI0508541A; RU2380155C2; WO2005087374A1; CN1905941A; JP2007527788A; AU2005221301A1; MXPA06007496A; NO20064487L

Abstract

The invention relates to a catalyst containing a porous support, which has cavities that open onto at least one face. Said openings have a diameter of approximately 0.7 to 20 nm, at least in one extension direction. The support has a specific surface area of at least 500 m2/g and is also charged with a content of at least one catalytically active metal component amounting to at least 2.5 m2 per gram of catalyst. The invention also relates to a method for producing a catalyst of this type and to the use of the latter in methanol synthesis or as a reformer in fuel-cell technology.

Description

March 7, 2005 Süd-Chemie AG Lenbachplatz 6

.., 4465-1-23.182

80333 Munich

Preparation of metal / metal oxide carrier analyzers by päkur s or r chemical nanometers ta lur gi e in defined reaction spaces of porous carriers using organometallic and / or inorganic precursors and metal-containing reducing agents

The invention relates to a method for producing a catalyst, a catalyst obtainable by the method, and the use thereof.

Cu / ZnO systems, which are usually supplemented by Al ₂ 0 ₃ , are used as catalysts for industrial methanol synthesis. These catalysts are produced on a large scale by precipitation reactions. Copper and zinc act as catalytically active substances, while the aluminum oxide is said to have a thermostabilizing effect as a structural promoter. The atomic ratios. copper and zinc may vary, but copper is generally in excess. Such catalysts are known for example from DE-A-2 056 612 and from US-A-4, 279, 781. A corresponding catalyst for methanol synthesis is also known from EP-A-0 125 689. This catalyst is characterized in that the proportion of pores with a diameter in the range from 20 to 75 Å is at least 20% and the proportion of pores with a diameter of more than 75 Å is at most 80%. The Cu / Zn atomic ratio is. between 2.8 and 3.8, preferably between 2.8 and 3.2, and the proportion of A1 ₂ 0 ₃ is 8 to 12% by weight.

A similar catalyst for methanol synthesis is known from DE-A-44 16 425. It has a Cu / Zn atomic ratio of 2: 1 and generally consists of 50 to 75% by weight of CuO, 15 to 35% by weight of ZnO and also contains 5 to 20% by weight of A1 ₂ 0 _3rd

Finally, EP-A-0 152 809 discloses a catalyst for the synthesis of alcohol mixtures containing methanol and higher alcohols, which in the form of an oxidic precursor (a) copper oxide and zinc oxide, (b) aluminum oxide as a thermostabilizing substance and (c ) contains at least one alkali carbonate or alkali oxide, the oxidic precursor having a proportion of pores with a diameter between 15 and 7.5 nm of 20 to 70% of the total volume, the alkali content 13 to 130 x 10 ^{~ 6} per gram of the oxidic precursor is and the alumina component has been obtained from a colloidally distributed aluminum hydroxide (aluminum hydroxide sol or gel).

In the processes hitherto used for the production of catalysts for the synthesis of methanol, after the support has been loaded with corresponding precursor compounds of the catalytically active metals, usually several oxidative and / or reductive preparation steps, mostly with air or oxygen as the oxidizing agent and hydrogen as the reducing agent, are added - go through relatively high temperatures. These procedures also include Ren usually several calcination steps, typically between 250-400 ° C. In these process steps, particle growth of the catalytically active reaction centers occurs, which leads to a reduction in the catalytic activity.

The Cu / ZnO system is the basis of industrial methanol synthesis and an important component of ^' fuel cell technology (reformer). It is considered a prototype for the research of synergistic metal / carrier interactions in heterogeneous catalysis [PL Hansen, JB Wagner, S. Helveg, JR Rostrup-Nielsen, BS Clausen, H. Tops0e, M. Science 2002, 295, 2053-2055 ]. Studies using high-resolution in-situ transmission electron microscopy (TEM) revealed dynamic changes in shape of ZnO-supported Cu nanocrystallites (2-3 nm) depending on the redox potential of the gas phase. Under the reducing conditions (H ₂ / CO) of the methanol synthesis there is a flattening. Cu particles with significantly increased wetting of the ZnO carrier. In addition, there is a positive correlation between the degree of tension of ZnO-supported Cu nanoparticles and the catalytic activity. The formation of Cu / Zn alloys is also important, as demonstrated by the promotion of Cu (111) surfaces as a result of Zn deposition.

Zeolites and zeolite-like structures, such as mordenite, VPI-5 or Cloverite, as well as periodic mesoporous silicate minerals (PMS) such as MCM-41, MCM-48, or SBA-15, have due to their very high specific surface areas and In the lower nm range, precisely adjustable pore structure has proven to be an excellent carrier for many catalytically active species and in particular Cu / PMS or CuO _x / PMS materials are being intensively investigated. This Cu / PMS or ^'CuO _x / PMS materials with respect to the methanol synthesis does not or significantly less active [K. Hadjiivanov, T. Tsoncheva, M. Dimitrov, C. Minchev, H. Knözinger, "Characterization of Cu / MCM-41 and Cu / MCM-48 mesoporous catalysts by FTIR spectroscopy of adsorbed CO ", Applied Catalysis A-General 2003, 241, 331] and do not contain the ZnO component.

The loading of PMS with metals and metal oxides by organometallic chemical vapor deposition is known for some metals, for example for Au [M. Okumura, S. Tsubota, M. Iwamoto, M. Haruta, "Chemical vapor deposition of gold nanoparticles on MCM-41 and their catalytic activities for the low-temperature oxidation of CO and of H ₂ ", Chemistry Letters 1998, 315.] or Pd [CP Mehnert, DW Weaver, JY Ying, "Heterogeneous Heck catalysis with palladium-grafted molecular sieves", Journal of the American Chemical Society 1998, 120, 12289.] and for A1 ₂ 0 ₃ [AM Uusitalo, TT Pakkanen, M. Kroger-Laukkanen, L. Niinistö, K. Hakala, S. Paavola, B. Lofgren, "Heterogenization of racemic ethylenebis (1-indenyl) zirconium dichloride on trimethylaluminum vapor modified silica surfacing", Journal of Molecular Ca talysis A Chemical 2000, 160, 343.].

The invention had for its object to provide a process for the preparation of catalysts, in particular for methanol synthesis, with which catalysts with a very high activity can be obtained.

This object is achieved with a method having the features of patent claim 1. Advantageous developments of the method according to the invention are the subject of the dependent claims.

The invention provides a method for producing a catalyst which comprises a porous support, at least one active metal and at least one promoter. The catalyst is particularly suitable for methanol synthesis. A porous carrier is prepared during manufacture. provided, which has a specific surface area of at least 500 m ² / g. At least one active metal precursor which comprises at least one active metal in a reducible form and at least one group which is bonded to the active metal atom via a ligator atom, which is preferably selected from oxygen, sulfur, nitrogen, phosphorus and carbon, is applied to the porous carrier. The active metal precursor is reduced with a reductor which has at least one promoter metal and at least one hydride group and / or an organic group which is bonded to the promoter atom via a carbon atom. The reductor, or the promoter metal contained therein, is finally transferred into the promoter. The promoter is usually formed by an oxide of the promoter metal.

The active metal precursor preferably comprises at least two groups which are bonded to the active metal atom via a ligator atom which is selected from oxygen, sulfur, nitrogen, phosphorus and carbon.

Likewise, the reductor preferably comprises at least two hydride groups and / or organic groups which are bonded to the promoter atom via a carbon atom, preferably from a group which is formed from alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof.

A “porous support” is preferably understood to mean a support which has cavities that are open at least on one side. The opening of these cavities has a diameter of at least about 0.7 to 20 nm, preferably about 0.7 to, along at least one direction of expansion 10 nm, particularly preferably about 0.7 to 5 nm. The term "cavity" is to be interpreted broadly. Such a cavity can be, for example, an approximately spherical cavity or a channel with a defined geometry, as used, for example, in zeolite materials is realized. The cavity can, however, also be formed between two layers, for example in layered silicates. However, the cavity has a comparatively small opening, so that the active metal precursor can diffuse into the cavity in a controlled manner and can be deposited there. In the case of layered silicates, the above-mentioned diameter of approximately 0.7 to approximately 20 nm therefore essentially corresponds to the layer spacing. In the case of spherical cavities, the porous carrier has pores with an approximately circular circumference.

The extent of the opening in the cavity can be determined by nitrogen adsorption measurements using the BJH method (DIN 66134).

The porous supports preferably have a pore volume of more than 0.09 cm ³ / g, particularly preferably more than 0.15 cm ³ / g. If zeolites are used as carriers, the pore volume is preferably less than 1.5 cm ³ / g.

MOF systems ("metal organic frame work") are also suitable as carriers. These systems include metal atoms that are three-dimensionally linked via organic ligands to form a network and are suitable for hydrogen storage, for example. These compounds are distinguished by very high pore volumes up to 10 cm ³ / g and by very high specific surface areas of more than 1000 m ² / g, particularly preferably more than 2000 m ² / g.

The porous support is distinguished by a high specific surface area of at least 500 m ² / g, preferably at least 600 m ² / g, preferably more than 800 m ² / g, particularly preferably more than 1000 m ² / g. The specific surface is determined by nitrogen adsorption measurement using the BET method (DIN 66131). At least one active metal precursor, which comprises at least one active metal in a reducible form and at least one group which is bonded to the active metal via a ligator atom, is now applied to the porous support. In the active metal precursor, the active metal atom is therefore in an oxidation state greater than zero. An active metal is understood to mean a metal which has a catalytic effect on the reaction to be catalyzed in the finished catalyst. In the case of a catalyst for methanol synthesis, this is, for example, copper, which is present as metal in the active form of the catalyst. An active metal precursor is accordingly understood to mean a compound from which the active metal can be released. In the inventive ^'methods are used compounds as active metal precursors that contain at least one atom of the active metal and at least one group which is bonded via a ligator at the active metal atom. The ligator atom is selected as oxygen, sulfur, nitrogen, phosphorus and carbon. The active metal preferably carries organic groups, ie groups which, in addition to the ligator atoms 0, S, N and P, have at least one carbon atom. These organic groups preferably have 1 to 24 carbon atoms, in particular 1 to 6 carbon atoms. In addition to the ligator atom, further heteroatoms or heteroatomic groups can be bound to the carbon skeleton, which coordinate as Lewis bases to the active metal and can thereby stabilize the active metal precursor. Suitable organic groups are, for example, alkoxides or amino-functionalized alkoxides.

The active metal precursor is reduced with a reductor in order to deposit the active metal on the walls of the pores. A reductor is understood to mean an organometallic compound which can reduce the active metal precursor in order to deposit the active metal on the porous support. The promoter metal is released from the reductor, which as a promoter, usually in Form of the oxide on which the support is deposited, preferably in nanodispersed form. The reducer therefore comprises at least one promoter metal and at least one hydride group and / or an organic radical which is bonded to the promoter metal via a carbon atom. The bond can take place both via a σ and via a π bond.

The groups in the active metal precursor are preferably bonded to the active metal via a ligator atom other than carbon, preferably via an oxygen or a nitrogen atom. However, if the groups on the active metal and on the promoter metal are both bonded to the metal atom via a carbon atom, the molecular weight of the groups of the reducer is preferably less than the molecular weight of the groups of the active metal precursor. The groups bonded in the reductor preferably have between 1 and 24, particularly preferably 1 to 6, carbon atoms and can optionally also contain groups bonded via a heteroatom which, as Lewis bases, can stabilize the reductor. The groups in the reductor are preferably selected from alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and its derivatives, and a hydride group. A promoter metal is understood to mean the metal which forms the promoter in the finished catalyst. The promoter is generally present as an oxide. In the case of a catalyst for methanol synthesis, zinc and possibly aluminum form the promoter metals.

Certain organometallic compounds are therefore advantageously considered as active metal precursors or as reductors in the process according to the invention.

Organometallic compounds are to be understood here: 1. Metal complexes in which there are direct metal-carbon bonds;

2. Metal complexes in which there is no metal-carbon bond, but which contain (coordinatively bound) ligands which are organic in nature, that is to say belong to the family of hydrocarbon compounds or derivatives thereof. "Organometallic" differentiates from purely inorganic metal complexes that contain neither metal-carbon bonds nor organic ligands.

The order in which the at least one active metal precursor and the at least one reductor are applied to the porous carrier is not in itself subject to any restrictions. The carrier can first be impregnated with the active metal precursor and then the reductor applied to deposit the active metal on the carrier. However, it is also possible to first apply the reductor to the carrier and then the active metal precursor. It is also possible to apply the active metal precursor and the reductor alternately to the support several times. The active metal precursor or the reductor is first physisorbed or chemisorbed on the surfaces of the porous support, in particular on the surfaces of the cavities. The active metal is then released from the active metal precursor by adding the respective other component. settles and depressed.

In the process according to the invention, special carrier materials are used on which the active metal and the promoter are deposited. The carrier materials are characterized by a high porosity, which is adjustable in the nanometer range, and thus an extremely high specific surface. The inventors assume that the cavities or pores act as dimensionally restricted reaction spaces for the reduction of the active metal precursor, so that undesired particle No growth in catalyst preparation. The cavity has a comparatively small opening, so that the active metal precursor can ^' diffuse into the cavity in a controlled manner and be deposited there. Therefore, only a limited amount of the active metal is deposited in each cavity. After the release, the active metal is therefore distributed in nanodispersed form on the walls of these reaction spaces. The maximum diameter of the particles at least in one direction does not exceed the pore diameter, which is 2 nm, for example using an MCM-41. In further process steps, in which the catalyst is heated to higher temperatures, for example, there is no exchange between the various cavities, so that growth of the catalytically active particles is suppressed and the nano-disperse distribution of the catalytically active centers is retained. This also has a favorable effect on the long-term stability of the catalysts under process conditions. The active metal precursors and the reductors preferentially adsorb on the inner surface of these carrier materials and thus come into direct chemical proximity in a very controllable manner. This has a positive effect on the efficiency of the reduction process, the dispersion of the active metal particles and the promoter components. _, This ensures in a new way a close surface or interface contact of the carrier, active metal particles and promoter components required for the catalytic properties.

If the catalytically active metal component comprises several metals or metal compounds, for example metal oxides, these are in intensive contact, since the individual components are each in nanodisperse form. The special characteristic of the method according to the invention is that, in contrast to other known impregnation methods, by a chemical reaction between the active metal precursors and the Reducers (reduction, or σ-bond metathesis or the like) the active metal in one by the carrier in nano-scale Di-. dimensionally limited reaction space, ie in a catalytically relevant close neighborhood, is separated and chemically fixed.

In the catalyst, which is stable in air, the active metals are usually in the form of an oxide. Exceptions are very noble active metals, e.g. Pt and Pd, etc. The oxides form as a result of air oxidation after the catalyst preparation. However, according to the state of the art, it is possible in an established manner to oxidize the metal mold only partially by special stabilization measures. The active metal is passivated through a thin oxide layer. After filling the reactor, the catalyst can then be converted back into its active form by a mild and simple re-reduction. For this purpose, these oxide layers are reduced with hydrogen, for example.

With regard to catalyst regeneration in particular, the quality of the catalytic activity of the system, as well as its chemical composition and structural characteristics, are not changed by repeated oxidation and reduction cycles; i.e. a corresponding catalyst regeneration to restore the original catalytic activity is advantageously possible.

The active metal is preferably selected from the group consisting of Al, Zn, Sn, Bi, Cr, ^' Ti, Zr, Hf, V, Mo, W, Re, Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, and Os.

The active metal can comprise only one metal from the group mentioned above, for example copper or zinc. However, it is also possible for the active metal to comprise several metals from the group mentioned above, for example two or three metals. The metals can be in reduced form as pure metal or also as a metal compound, in particular as a metal oxide. As already explained, the active metal in the transport form of the catalyst is usually in at least partially oxidized form, so that the catalyst is sufficiently stable even in air.

According to a preferred embodiment, the promoter metal is selected from the group which is formed from Al, Zn, Sn, rare earth metals, as well as alkali and alkaline earth metals. Suitable alkali and alkaline earth metals are e.g. Li, Na, K, Cs, Mg and Ba. The active metal and the promoter metal are selected differently for the catalyst.

In the process according to the invention, therefore, special metal-containing reducing agents are used, which are referred to here as reductors. These reductors release the active metals that are essential for the catalytic properties from the corresponding chemical precursors (active metal precursors) in which these metals are bound in a defined form by particularly efficient but at the same time very gentle chemical reduction. Those organometallic compounds which contain a metal which acts as a promoter of the catalytically active active metal are used as reductors.

If a catalyst for methanol synthesis or a reformer for fuel cell technology is produced by the method according to the invention, the catalyst preferably comprises the Cu / Zn / Al system. The atomic number ratios of Cu / Zn / Al are in the typical range between 1: 2: 0.1 to 2: 1: 1. The copper can be introduced through a suitable active metal precursor, the zinc through the reductor and the aluminum through the porous support.

The active metal precursor is preferably a compound of the formula MeX _p L ₀ , in which Me represents an active metal, X is selected from the group of alcoholates (OR *), amides (NR ₂ *), ß-diketonates (R * (= 0) CHC (= 0) R *) and their nitrogen analogues, especially ß-ketoiminates (R * (= 0) CHC (= NR *) R *) and ß-diiminates (R * (= NR *) CHC (= NR *) R *), carboxylates (R * COO), oxalates (C ₂ 0), nitrates (N0 ₃ ) and carbonates (C0 ₃ ), where R * stands for an alkyl radical with 1 to 6 carbon atoms, an alkenyl radical with 2 to 6 carbon atoms, an aryl radical with 6 to 18 carbon atoms, and furthermore the radicals R * are the same or different , p is an integer that corresponds to the valence of the promoter metal, o is an integer between 0 and the number of free coordination sites of the promoter metal atom, and L is a Lewis basic organic ligand that includes oxygen or nitrogen as the ligator atom. L and X can only include one type of the ligands or residues mentioned. However, it is also possible to provide combinations of the groups mentioned.

According to one embodiment of the process according to the invention, the reductor is a compound of the formula MR _n L _m , where M stands for a promoter metal, R for an alkyl radical with 1 to 6 carbon atoms, an alkenyl radical with 2 to 6 carbon atoms, an aryl radical with 6 to 18 Carbon atoms, a cyclopentadienyl radical or its derivatives, or represents a hydride group, where the radicals R may be the same or different, n is an integer which corresponds to the valence of the metal, L is a Lewis basic organic ligand which is oxygen or comprises nitrogen as the ligator atom, and m is an integer between 0 and the number of free coordination sites of the active metal atom. It also applies to the reductor that only one type of the groups mentioned can be used for the radical R and the ligand L. However, it is also possible to combine different groups. For example, compounds of the formula OR'R "or NR'R" R ^m can be used as ligands L, the radicals R ', R "and R'" representing an alkyl group having 1 to 6 carbon atoms, two of these radicals also being common can form a ring with the heteroatom.

Reductors of the formula MR _n L _m are particularly preferred selected from ZnR ₂ L _m and AlR ₃ L _m , with m = 0, 1 or 2, where R and L have the meaning given above.

In general, the active metal precursors with which the porous carrier is loaded are selected such that they are combined with one another or with the abovementioned reducers as a result of complete or partial X / R exchange in the restricted reaction spaces of the carriers to species of the composition MeR _x ( x ≤ m) react which, in turn, with the reductive elimination of R ₂ or fragments of R ₂ as a result of β-H elimination and hydrogen / alkene cleavage or radical decomposition subsequently to the elemental metal or in comparison to the active metal precursor MeX _p L _o into one reduced form can be transferred.

The above-mentioned active metal precursors and reductors can be applied to the porous support in solution. The solvent and the active metal precursors or reductors are matched to one another in such a way that no decomposition takes place in the solvent. After the active metal precursor has been coated on the support, the solvent is removed together with excess active metal precursor. To remove solvent residues, the loaded porous carrier can optionally be dried first. The reductor, which in turn is an organometallic compound, is then placed on the porous support. The reductor reduces the initially applied active metal precursor, so that the catalytically active metal is deposited and fixed on the porous support. This process can also be done in reverse Order are carried out, ie the porous support is first loaded with the reductor and then with the active metal precursor.

However, the individual metal or metal oxide components of the catalyst are particularly preferably applied to the porous support by chemical vapor deposition (CVD, chemical vapor deposition). In this case, the active metal precursors or the reductors preferably have a vapor pressure of at least 0.1 mbar at 298 K. In a particularly preferred embodiment of the process according to the invention, organometallic complexes are used both as active metal precursors and as reductors.

Combinations of these methods are also possible. For example, the active metal precursor can be applied in solution and then the reductor can be applied by chemical vapor deposition. Likewise, the active metal precursor can also be applied first by vapor phase deposition and then the reductor can be applied in solution.

The porous support itself can consist of any material. However, the carrier should include the cavities described above which have a relatively small opening with those indicated above. Have dimensions. For example, the previously mentioned MOF systems are suitable as porous support materials. Since the catalysts are mostly used at elevated temperature, it is preferred that the support is composed of an inorganic material. Examples of suitable inorganic materials are zeolites, PMS, layered silicates such as bentonites, clays or pillard clays, hydrotalcites, and also heteropoly acids, e.g. of molybdenum and tungsten.

However, periodic mesoporous silicate materials (PMS) are particularly preferred because they have very high specific Have surfaces and the pore structure can be adjusted precisely. Examples of these are MCM-41, MCM-48 or SBA-15.

In the case of the zeolites, those which have a large pore radius are preferred. Zeolites with a pore radius of> 0.7 nm are e.g. Mordenite, VPI-5 or cloverite.

The catalyst is produced under extremely mild conditions. Thus, a temperature of 200 ° C. is preferably not exceeded during the production of the catalyst. The active metal is thereby deposited in a highly disperse form, the diameter of the particles produced from the active metal generally being in the range from about 0.5 to 10 nm, preferably 0.5 to 5 nm. The promoter is also deposited in a highly disperse form, so that a very large contact area between the active metal and the promoter can be achieved. This leads to catalysts with very high activity.

The invention therefore also relates to a catalyst, in particular for methanol synthesis, with a porous support, and at least one active metal deposited on the porous support and at least one promoter deposited on the porous support, the porous support having a specific BET surface area of at least 500 m / g, the active metal has a specific metallic surface area of at least 25 m ² Ativmetaiι / gAtivmetaiι ^unc the promoter has a specific surface area of at least 100 m ² / gp _rθ motor _r, preferably at least 500 m gpr _omotor . The specific surface area of the active metal can be determined by gas adsorption / desorption processes or by reactive gas adsorption / desorption processes. One such method is, for example, N ₂ O reactive frontal chromatography for determining the specific surface area of copper. Analog procedures can be used for other tivmetal be applied. They are generally based on the occupation of the metal surface with a molecule with a known space requirement, the amount of adsorbed molecules being determined. The specific surface area of the promoter can be estimated by determining the degree of aggregation via X-ray absorption examinations and by determining the BET surface area on the loaded support. The content of promoter component can be determined by elemental analysis (eg atomic absorption spectroscopy or energy dispersive X-ray absorption spectroscopy).

A distinguishing feature of the catalysts produced by the process according to the invention compared to the catalysts produced by alternative processes, in particular by co-precipitation / calcination, is the extremely low, even disappearing degree of aggregation of the promoter component (can be determined by X-ray absorption studies) with a high BET surface area of the active Catalyst of preferably well over 500 m ² / g. Usually there is no measurable degree of coordination. In this case, when the catalysts are measured using X-ray diffraction methods, no diffraction reflections can be observed for the promoter. When measuring the catalyst with X-ray absorption spectroscopy, only very low aggregation states are obtained. This means that the next but one or the next but one neighboring atoms of a promoter atom are generally not promoter atoms. In general, at most the next but one or the next but one neighboring atom is again a promoter atom. In other words, the promoter is preferably at most a two- or three-shell promoter.

Also typical is the very low degree of aggregation of the active metal component, which is particularly evident in the fact that the metal particles, e.g. B. copper, on the (inner) surface of the carrier so homogeneously distributed and so small that they are using transmission electron microscopic methods cannot be recorded and characterized as well-formed particles, whereas a small but determinable degree of aggregation of the majority of the particles can be characterized as described by X-ray absorption measurements. The active metal in the catalyst according to the invention preferably has an average coordination number of at most 10. The coordination number is preferably less than 10, particularly preferably between 4 and 7. Often a coordination number of about 6 is observed. Since the active metal particles are preferably very small, the coordination number does not change when the active metal is converted into the oxidized form, for example for transport from the place of manufacture to the synthesis reactor.

The maximum crystallite size of the active metal or of the promoter is limited in each case by the maximum pore diameter in one dimension.

The catalyst according to the invention comprises a porous support which preferably has cavities open at least on one side. The opening of these cavities has a diameter of at least about 0.7 to about 20 nm, preferably about 0.7 to 10 nm, particularly preferably about 0.7 to 5 nm along at least one direction of expansion. Furthermore, the porous support is characterized by a high specific BET surface area of at least 500 m ² / g, preferably at least about 600 m ² / g, particularly preferably at least about 800 m ² / g. These high specific surfaces are also measured on the finished catalyst. The specific surface area is somewhat reduced by the coating with the active metal and the promoter. However, the finished catalyst has a very high BET surface area of at least 500 m ² / g, preferably at least about 600 m ² / g, particularly preferably at least about 800 m ² / g, in comparison with conventional catalysts. The porous support is loaded with at least one catalytically active metal component which is in a highly dispersed form. The loading is at least about 2.5 m ² _A ktivmetaij. ^ ^"" ^"Katalsators preferably at least about 3 m ² g ^-1 Aktimetaii κataiysator / 'more preferably about 5 m ² g ^_1 Aktivmetaii κataiysator • It may also be achieved an even higher load. These are in the range of more than 10

IΩ active metal ζf catalyst up to more than 20 Itl active metal <3 catalyst

In other words, the loading of the active metal is at least about 25 m ² g ^-1 A _k tivmetaii Aktivmetaiι _r preferably at least about 35 m ² Aktivmetaii more preferably at least about 50 m ² _A ktivmetaiι In particularly preferred cases, the loading is according .more than 100 m ² _Akt iv ii _meta g ^~ ¹ _r Aktivmetaii in particularly preferred cases more than 200 m ² Aktivmetaii y active metal •

The loading of the catalyst with the active metal is preferably in the range of about 0.05 to 0.50g _A ktivmetaiι g ^{'xataiysator,} preferably ^¬, about 0.1 to 0.45 g _A ktivmetaiι g ^_1 κataiysator _r particularly preferably about 0.1 to 0.30 g _A ktivmetaiι g ^-1 κataiysator selected and the loading with the promoter preferred in. Range from about 0.01 to

0.3 gprootor Preferably about 0.05 to 0.2 g promoter g ^_1 κataiysato _r . particularly preferably selected about 0.05 to 0.15 gp _rom otor g ^_1 κ _a taiysa _tor ^. The values or ranges of values given relate in each case to the metal or the promoter metal. The ratio of active metal / promoter metal is preferably selected in the range from approximately 10: 1 to 1: 5, preferably approximately 5: 1 to 1: 2, in particular approximately 5: 1 to 1: 1. When producing the catalyst, as much active metal as possible and as little promoter as possible is preferably introduced.

The preferred carriers as well as active metals and promoters have already been explained in connection with the method according to the invention.

The catalyst obtainable with the process according to the invention has a number of advantages, as described below Example of an embodiment of the catalyst according to the invention is explained as a catalyst for methanol synthesis.

The catalyst according to the invention differs from the known Cu / Zn / Al catalysts for methanol synthesis by the following criteria:

(1) The dispersion of the Cu component (or the active metal) is higher, at least 25 m ² _Cu g ^_1 cu, ie with the same mass fraction of catalytically active Cu component _. Catalyst according to the invention more active, or for the same activity, a smaller mass fraction of copper (active metal) is sufficient in the catalyst according to the invention compared to known catalysts. The analytical characterization of the catalyst using EXAFS (extended x-ray absorption fine structure spectroscopy, X-ray absorption) and XRD (x-ray diffraction, X-ray diffraction) shows that the majority of the Cu particles have a dimension around or below 1 nm typically means aggregates around 10-20 Cu atoms, the minority of the Cu particles has dimensions of at most the channel or pore size of the PMS carrier material.

(2) In contrast to known Cu / ZnO / Al ₂ 0 ₃ catalysts, the ZnO and the aluminum oxide component (promoter) is not ordered in an ordered manner. Rather, according to EXAFS data, they form a thin coating on the inner walls or obex surfaces of the carrier material. In this way, the specific surface area of the ZnO component reaches the order of magnitude of the specific surface area of the carrier material (> 500 m ² / g) and surpasses previously known surface-rich ZnO carrier materials with their specific BET surface areas of up to approx. I50 m ² g ^"1 by far. [M. Kurtz, N. Bauer, C. Büscher, H. Wil er, O. Hinrichsen, R. Becker, S. Rabe, K. Merz, M. Driess, RA Fischer, M. Muhler, "New synthetic routes to ore active Cu / ZnO catalysts used for methanol synthesis ", Catalysis Letters 2004, 92, 49; CR Lee, HW Lee, JS Song, WW Kim, S. Park, "Synthesis and Ag recovery of nanosized ZnO powder by solution combustion process for photocatalytic applications", Journal of Materials Synthesis and Processing 2001, 9, 281; T. Tani, L. Madler, SE Pratsinis, "Homogeneous ZnO nanoparticles by flame spray pyrolysis", Journal of Nanoparticle Research 2002, 4, 337.]. In contrast to known Cu / ZnO / Al ₂ 0 ₃ catalysts, the catalyst according to the invention has no nanocrystalline ZnO or Al ₂ 0 ₃ components which can be detected using TEM or XRD methods.

These criteria apply not only to a catalyst for methanol synthesis using the Cu / ZnO / A1 ₂ 0 _{3 system} , but can also be applied to all catalysts obtainable by the process according to the invention.

The catalysts of the invention are distinguished by a very high activity based on the mass fraction of the catalytically active metal components. You _. . are therefore particularly suitable for use as a catalyst for methanol synthesis or as a reformer in fuel cell technology.

In summary, it can be said that taking into account preferred embodiments, the advantages of the invention exist

1. in the gentle process conditions (in particular lower preparation temperatures, in particular temperatures below 200 ° C.), which suppresses unfavorable particle growth processes which cannot be avoided according to the prior art;

2. in the combination of active metal precursors with metal-containing reducing agents (reductors), which an unusually high dispersion of active metal components (active metals) and promoter components with high Allow metal / metal oxide promoter to come into contact with the surface or interface. The latter leads to an improvement in the specific activity and selectivity of the catalysts;

3. in the conditional by the novel method, the composition is possible answer-t of the catalyst system while maintaining high dispersion by Peer mutation and / or cyclic repetition of the individual Belädungs- ^'or reaction steps to control;

4. in the absence of problematic salt and / or stabilizer loads, e.g. bring with them the prior art impregnation techniques based on colloidal chemical processes;

5. in the use of porous, sluggish cr materials as dimensionally restricted reaction spaces for the critical metathetical surface reaction between different precursors. The dimensionally restricted reaction spaces (geometrically defined by the pore characteristics of the porous carrier systems) suppress unwanted particle growth due to their inherent geometry. This is supported in a special way by the larger ratio of surface area to volume in the case of porous supports, which is optimized compared to ^' comparatively little porous supports. The carrier properties mentioned thus counteract segregation of the components. This ensures a high dispersion of the catalytically active components and a high specific loading of the carrier.

The invention is explained in more detail below with the aid of examples and with reference to the attached figures. Dabe ± shows: 1 shows a highly schematic representation of the mechanism by which the deposition of the active metal and the promoter metal proceeds in the process according to the invention;

2: X-ray powder diffractograms of the samples: a) the precursor Cu / [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 obtained at room temperature, b) the catalytically active sample Cu / ZnO / MCM-41 and c) the comparative sample ZnO / MCM-41 and d) the comparative sample Cu / MCM-41. The (111), (200) and (220) reflective layers of polycrystalline copper are marked on the abscissa for orientation.

Fig. 3: Small-angle powder diffractograms of a) empty, calcined MCM-41 and b) Cu / ZnO / MCM-41. The characteristic decrease in intensity of, b) compared to a) is an indication of the loading of the pores. In the TEM image of a Cu / ZnO / MCM-41 sample also shown, the intact pore structure can be clearly seen; However, copper or zinc oxide particles cannot be identified due to their small size. The presence of copper and zinc is evidenced by the associated EDX spectrum (element dispersive X-ray fluorescence analysis).

4: a) C FC-XANES and b) Cu -EXAFS spectra (amount of the Fourier transform) of Cu / ZnO / MCM-41 and reference substances, c) analysis of the spectrum of Cu / ZnO / MCM-41; Model parameters: Neighbor Cu; Distance (R) = 2.512 ± 0.002 Ä, coordination number (N) = 5.8 ± 0.3, Debye-Waller factor (σ ² ) = (9.6 + 0.4) * 10 ^"3 Ä ^2. Neighbor 0: R = 1.86 + 0.04 Ä , N = 0.3 + 0.1, σ ² = (7 ± 0.11) * 10 ^{~ 3} Ä ² . Fig. 5: Reaction of [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] with diethyl zinc in the nanotubes of the MCM-41 carrier material.

Fig. 1 shows a schematic representation of the mechanism by which the deposition of active metal and promoter takes place in the inventive method. It is understood that this is only a model presentation and should in no way limit the scope of the invention.

FIG. 1 a shows a section through a porous carrier 1, in which a pore 2 runs, which is open to the outside of the carrier 1. The carrier 1 can be a zeolite, for example. An active metal precursor 3 and a reductor 4 are diffused into the pore 2. The loading can take place in such a way that the porous carrier 1 is first loaded with the active metal precursor 3 and then with the reductor 4. However, it is also possible to add the porous carrier 1 first with the reductor 4 and then with the active metal precursor 3 loaded. If the mixture of active metal precursor 3 and reductor 4 is sufficiently stable at the loading temperature, the loading can also take place simultaneously. The active metal precursor 3 comprises an active metal AM to which groups L are bound. In FIG. 1, the active metal AM carries two groups L for the sake of clarity. However, it is also possible for the active metal precursor 3 to comprise more than two groups L. In addition to the groups L, the active metal AM can also carry other ligands which stabilize the active metal precursor, for example by coordinative binding. The groups L are bonded to the active metal AM via a ligator atom (not shown). The ligator atom is selected from oxygen, sulfur, nitrogen and carbon. The reductor 4 comprises a promoter metal PM, to which organic groups R are bonded via a carbon atom. In Fig. 1 ^'of the reducer comprises the sake of clarity only two groups R. However, it is also possible that more than two groups R are bound to the promoter metal PM or that in addition to the groups R further groups are bound to the promoter metal PM. The letters x and y correspond to the molar ratio of active metal promoter 3 and reductor 4 used. As a central step of the deposition, a ligand exchange now takes place between active metal AM and promoter metal PM. This is shown in Fig. Lb. A reactive intermediate compound 5 is formed, which comprises the active metal AM and the groups R. In addition, the promoter compound 6 is obtained, which comprises the promoter metal PM and the groups L. The reactive intermediate 5 then disintegrates. This decay process is supported or initiated, for example, by heating. The active metal contained in the reactive intermediate compound 5 is reduced to the active metal AM and is deposited in nanodisperse form as crystallites 7 on the walls of the pores 2 (FIG. 1 c). At the same time, the compound RR arises from the groups R, for example in a metathesis reaction. This can be deducted as exhaust gas. The promoter compound 6 is still oxidized, so that the promoter metal as promoter PR, for example in the form of an oxide, also in nanodisperse form as crystallites 8 in the immediate vicinity of the active metal crystallites 7 on the walls of the pores 2. The groups L are released and can also be extracted with the exhaust gas.

Example 1: Cu / ZnO / MCM-41

Freshly synthesized, calcined and dry MCM-41 (350 mg) is placed together with a portion of approx. 1.0 g [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] in separate glass boats in a Schlenk tube and in a static vacuum (0.1 Pa) for 2 h heated to 340 K. A sample of 200 mg of the blue colored product material and approx. 0.5 g diethyl zinc are positioned next to each other as above and left in a static vacuum (0.1 Pa) for 2 h at room temperature. The variation of the loading Steaming time, temperature, amounts of material and PMS material lead to different loads (Table 1). To generate the ZnO, the sample Cu / [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 is removed under protective gas and then tempered to 623 K in a dynamic vacuum (0.1 Pa) (2 h). Accordingly, with other PMS materials, such as. B. MCM-48.

Example 2: Cu / MCM-41 and ZnO / MCM-41

Annealing [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 (see above) in a dynamic vacuum (0.1 Pa) at 523 K (20 min) provides Cu / MCM-41. Analogously, ZnO / MCM-41 is obtained using [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] as a ZnO precursor after tempering the intermediate stage [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 ^' at 623 K (0.1 Pa , 2 h). [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 was obtained by impregnating MCM-41 with a solution of [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] (1.0 g) in pentane (40 mL) and washing the obtained separated solid. Alternatively, ZnO / PMS can be obtained by treating the carrier with diethyl zinc vapor and then calcining it.

Characterization of the samples

The X-ray powder diffractograms (PXRD) were recorded using a D8 Advance Bruker AXS diffractometer with Cu K radiation (λ = 1.5418 Ä) in Θ-2Θ geometry and a position-sensitive detector (capillary technology, shielding gas). All diffractograms have been fitted using Profile Plus 2.0.1 software using a pseudo-Voigt function. TEM investigations were carried out with a. Hitachi H-8100 device carried out at 200 kV with a tungsten fila ent (preparation under exclusion of air, gold grids piano _r vacuum transfer holder). X-ray absorption spectra (XAS) were recorded at Hasylab (DESY, Hamburg) at station XI on a Si (311) double crystal monochromator in transmission (VIPER software). Nitrogen adsorption measurements were carried out with a Quantachrome Autosorb-1 MP apparatus. The pore diameter was calculated using the Barrett-Joyner-Halenda (BJH) method. The specific surface area (S _BET ) of the empty, calcined MCM-41 and the CuO _x / MCM-41 was determined using the data of the linear part of the BET graph (p / po = 0.05-0.35).

Table 1 Catalyst-relevant properties of the Cu / ZnO / PMS samples.

Production rate ' ^w in [μmol eθH ^, g ^"1 κat-h r ¹ ] at 4.6 m ² , _Cu 6.2 m cu 5.8 m ² _Cu μmol% by weight Cu% by weight Zn' g Cat 'g Kat "g Kat MeOH h-' m ^ cu

Cu / ZnO ^ ¹ 71 86 80. 13.8 10-90 10-75

Cu / ZnO / Al ₂ O ₃ ^w 167 184 172 27 30-50 20-40

Cu / ZnO / MCM-41 19 4.1 ^" 6.85 10.44

Cu / ZnO / MCM-41 36 5.8 9.30 15.57

Cu / ZnO / Al ₂ 0 ₃ / MCM-62 10.2 8.70 14.5.

41 (@ wt% AI: 6.3)

Cu / ZnO / MCM-48 130 22.4 10.62 21.95 Cu ^• surface

Cu / MCM-41 5-7 m'cu-g ^"1 nn ^[cl 10-12 - Cat

ZnO MCM-41 nn ^M - 20.75

[a] The copper surface was determined using N ₂ 0-RFC. After pretreatment with a dilute H ₂ atmosphere (2% by volume), N ₂ 0 (1% by volume N ₂ 0 in He, 300 K) was passed over the catalyst and the copper surface was calculated from the amount of nitrogen released (density on Cu surface atoms: 1.47 • 10 ¹⁹ m ^-2 ). The methanol synthesis activity was investigated under normal pressure and a temperature of 493 K. A mixture of 72% H ₂ , 10% CO, 14% CO ₂ and 14% He was used as the synthesis gas. The data given were obtained after a reaction time of 2 hours. Due to the low material conversion at normal pressure, no products other than methanol could be detected.

[b] Catalyst-specific data of coprecipitated catalysts whose MeOH synthesis performance was determined under conditions similar to those of the Cu / ZnO / PMS samples. From regression ^analysis' (production rate as a function of the Cu surface of the catalysts of different metal concentration), the production rates to in the Cu / ZnO / PMS found Cu surfaces inter- (Cu / ZnO), or extrapolated (Cu / ZnO / Al ₂ 0 ₃ ). The data for the comparative samples come from: T. Genger, dissertation, Ruhr University Bochum, 2000.

[c] undetectable.

Further characterization of the samples: If a portion (350 mg) of pure, freshly calcined MCM-41 (0 _BJH = 2.7 nm, S _B ET = 712 m ² g ^"1 ) was placed in a static vacuum (0.1 Pa) the steam of a placed next to it Portion (1.0 g) of the blue-violet Cu precursor [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] (l). At 340 K in a tightly sealed Schlenk tube, the originally colorless silicate material turns light blue Precursor [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] remains intact, as the comparison of the IR data of the loaded MCM-41 with pure [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] shows. The adsorption is strong because [Cu ^' (OCHMeCH ₂ NMe ₂ ) ₂ ] cannot be desorbed even at elevated temperature (373 K) in a dynamic vacuum (0.1 Pa, 24 h). The absence of the IR absorption otherwise observed at 3745 cm ^"1 indicates free silanol groups an interaction of the pore walls with [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ], probably over hydrogen bonds. In a second step, the carrier loaded with [Cu (OCHMeCH ₂ NMe ₂ ) ₂ ] is then treated with diethyl zinc vapor by placing both samples next to one another in a Schlenk tube and sealing it in an evacuated manner (0.5 g ZnEt ₂ , 300 K, 0.1 Pa), the color changes gradually from light blue to red-brown. In the X-ray powder diffractogram of a sample of the material prepared under inert gas in a capillary, a weak, very broad structure appears at 2 θ = 44.70 °, which can be assigned to the reflection of the [111] network plane of small Cu particles {Flg. 2 and 3). Solid-state NMR spectroscopy shows [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] (2) as a by-product. This reaction, which takes place in the nano-tubes of the PMS, corresponds to the guantitative implementation according to FIG. 5, which can be understood in the preparative gram scale in solution, in which Cu metal fails (XRD), the zinc alkoxide [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] remains in solution (NMR identification) and butane escapes as a gas (GC-MS). It should be noted that when the reactivity of the zinc alkyl used is reduced, for example by using very bulky alkyl residues such as C (SiMe ₃ ) ₃ , the alkyl / alkoxide metathesis is absent and bimetallic alkyl zinc / copper alkoxide complexes are isolated and structurally characterized, the solids of which Pyrolysis has so far only led to microcrystalline, catalytically inactive Cu / ZnO materials.

Gentle tempering of the samples Cu / [Zn (OCHMeCH ₂ NMe ₂ ) ₂ ] / PMS at 623 K in a dynamic vacuum (0.1 Pa, 2 h) provides largely CH _x -free materials that still have a very broad Cu ( Show 111) reflex. However, there are no X-ray indications of ZnO'-nanocrystallites {Fig. 2). The specific Cu surfaces of the Cu / ZnO / PMS samples were determined before and after the catalysis tests to be 5-6 m ² cu'g ^-1 κat (Table 1). The methanol production capacities between 19 and 130 μmol ^■ g ^_1 κ _at "h ^{" 1} are in the range of those prepared by coprecipitation / calcination binary Cu / ZnO catalysts, or surpass them surprisingly significantly in the case of the MCM-48 sample. The three-dimensional pore structure of the MCM-48 carrier allows a more efficient diffusion compared to MCM-41. The reduction (H ₂ ) of completely oxidized samples stored in air (disappearance of the Cu (111) reflex) regenerated the original activity or Cu surface. The comparison samples Cu / MCM-41 (10-12% by weight; 5-7 m ² _Cu -g ^'"1 κat and ZnO / MCM-41, which were obtained by tempering [M (OCHMeCH ₂ NMe ₂ ) ₂ ] / MCM-41 (M = Zn, Cu), or treatment of MCM-41 with diethylzinc vapor and calcination were found to be inactive. For freshly prepared Cu / ZnO / PMS samples, oxidation / Reduction cycles (N ₂ 0 / H ₂ ) unusually high values for the Cu surfaces of up to 50-60 m ² _Cu .: G ^{~ 1} κ _a t measured, but in the further course to the characteristic level of 5-6 m ² cu "g ^-1 κat fell off. This discrepancy apparently does not result from sintering of the Cu particles, but is due to the 0-Zn-C ₂ H ₅ groups which are bound to the pore wall of the PMS and, relative to Scheme 1, which groups can also be oxidized by N ₂ 0.

The EXAFS spectra (Fig. 4) vό ^"n Cu / ZnO / MCM-41 confirmed the presence of very small Cu aggregates. The coordination number determined by 5.8 and the relatively high Debye-Waller factor already the first metal shell indicate A high degree of disorder, assuming spherical, monodisperse particles, a diameter of 0.7 nm can be calculated, which would correspond to a cluster of 13 Cu atoms, even if the particle size is underestimated due to the correlation between the coordination number and the Debye-Waller factor it can be assumed that the almost complete absence of higher coordination shells shows that the characteristic dimension of the particles is certainly below the pore radius of 2-3 nm. The Cu aggregates are present in a particle size distribution from which the X-ray Diffraction only the coarsely disperse fractions (around 2 nm) registered. The Cu-Cu contact of 2.50 Ä calculated from the Cu (111) reflex layer of 2 θ = 44.35 ° corresponds to the value of 2.51 Ä obtained from the EXAFS data and is 2.56 Ä compared to the Cu-Cu distance of the bulk phase shortened (effect of small particles). The origin of the Cu-O coordination found is not clear. In view of the small mean particle size, it is obvious that oxygen atoms of the pore wall can already be registered in the EXAFS spectrum, as has been described in the literature. It cannot be ruled out that a small proportion of the copper is present as Cu ⁺ . The comparison of the Zn spectra with test substances (not shown) shows no agreement for either ZnO or Zn. For example, the intensity of the first O sphere is too low and the second sphere (Zn) is almost completely absent. With Si and Zn as the next but one neighbors, the adaptation is good, which, in accordance with the solid-state NMR and IR data (lack of free silanol groups), indicates an occupation of the pore wall with ZnO. The degree of aggregation of the ZnO component is therefore vanishing. The same applies to ZnO./PMS materials which were obtained using aqueous impregnation / calcination techniques. Clear indications of CuZnO _x species or Cu-O-Zn coordination could not be extracted from the data.

Cu-based methanol catalysts can be grouped into three classes: the binary systems Cu / Al ₂ 0 ₃ (I), Cu / ZnO (II), and the ternary system Cu / ZnO / Al ₂ 0 ₃ (III). For classically prepared materials, the activity correlates linearly with the specific Cu surface at different levels, increasing from I to III. Our activity of 130 μmol ^■ g ^_1 _Kaf h ^"1 found for the sample Cu / ZnO / MCM-48 is now far above the value to be expected for binary Cu / ZnO catalysts with the same specific surface area and is already in area III Cu particles with of the silicate matrix are hardly responsible for this, since Cu / PMS comparison samples were inactive and the pore walls of the active Cu / ZnO / PMS samples are, as explained above, apparently covered with ZnO. Rather, the simultaneous high dispersion of Cu and ZnO components seems to be a new, positive effect. An aggregated, (nano) crystalline ZnO phase, which is inevitable after coprecipitation / calcination formulations, is clearly not necessary for the synergistic effect. This corresponds to the Cu / Zn alloy formation cited at the beginning, as well as our further observations, namely that a classically produced Cu / Al ₂ 0 ₃ catalyst experienced a jump in activity beyond the region of the ternary systems as a result of a short treatment with diethyl zinc vapor. In addition, the use of a special, particularly surface or defect-rich, nanodisperse ZnO carrier material (153 m ² -g ^-1 ), which was obtained by solid pyrolysis of [(Me ₃ SiO) ZnMe] ₄ , led to an unusually active , binary Cu / ZnO catalyst.

The perspectives of the method according to the invention for loading PMS support materials, in particular for the Cu / ZnO catalyst preparation, are: not only the variation in the dimension and structure of the pores (for example MCM-41 vs. MCM-48 or other suitable support materials) but also that Exhaustion of the chemistry of the precursor substances allows molecular control over the active metal / promoter, for example the Cu / ZnO contact. The results are interpreted to mean that the method according to the invention surprisingly maximizes the specific active metal surfaces (for example Cu surfaces and the Cu / ZnO interface contact or the ZnO dispersion) and the interface contact between active metal / metal oxide or promoter in a surprising manner Increase in catalytic activity far beyond what was previously possible, nothing should stand in the way.

Claims

claims

1. A process for producing a catalyst with a porous support, at least one active metal and at least one promoter, which is particularly suitable for methanol synthesis, wherein a porous support is provided, which has a specific surface area of at least 500 m / g, on the porous Carrier is applied at least one active metal precursor which comprises at least one active metal in a reducible form and at least one group which is bonded to the active metal atom via a ligator atom, which is preferably selected from oxygen, sulfur, nitrogen, phosphorus and carbon, the active metal precursor with a Reductor is reduced, which has at least one promoter metal and at least one hydride group and / or an organic group which is bonded to the promoter atom via a carbon atom, and the reductor is converted into the promoter.

2. The method according to claim 1, wherein the at least one organic group on the reducer is selected from alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and its derivatives, and a hydride group.

3. The method according to claim 1 or 2, wherein the active metal is selected from the group consisting of Al, Zn, Sn, Bi, Cr, Ti, Zr, Hf, V, Mo, W, Re, Cu, Ag , Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, and Os.

4. The method according to any one of the preceding claims, wherein the promoter metal is selected from the group which is formed from Al, Zn, Sn, rare earth metals, and alkali and alkaline earth metals.

, Method according to one of the preceding claims, wherein the active metal precursor is a compound of the formula MeX _p L ₀ , in which Me stands for an active metal precursor, X is selected from the group consisting of alcoholates (OR *), amides (NR ₂ *), ß- Diketonates (R * (= 0) CHC (= 0) R *) and their nitrogen analogues, especially ß-ketoiminates (R * (= 0) CHC (= NR *) R *) and ß-diiminates (R * (= NR *) CHC (= NR *) R *), carboxylates (R * C00), oxalates (C ₂ 0 ₄ ), nitrates (N0 ₃ ) and carbonates (C0 ₃ ), where R * stands for an alkyl radical with 1 up to 6 carbon atoms, an alkenyl radical with 2 to 6 carbon atoms, an aryl radical with 6 to 18 carbon atoms, and furthermore the radicals R * can be identical or different, p is an integer which corresponds to the valency of the promoter metal, o is an integer between 0 and the number of vacant coordination sites of the promoter metal atom, and L is a Lewis basic organic ligand which contains oxygen or nitrogen as a ligate includes oratom.

6. The method according to any one of the preceding claims, wherein the reductor is a compound of the formula MR _n L _m , where M stands for a promoter metal, R stands for an alkyl radical with 1 to 6 carbon atoms, an alkenyl radical with 2 to 6 carbon atoms, an aryl radical with 6 to 18 carbon atoms, a cyclopentadienyl radical or its derivatives, or for a hydride group, where the radicals R may be the same or different, n is an integer which corresponds to the valence of the metal, L is a Lewis-based organic ligand which is oxygen or Contains nitrogen as a ligator atom, and m is an integer between 0 and the number of free coordination sites of the active metal atom.

7. The method according to any one of the preceding claims, wherein the active metal is copper and the promoter metal is zinc and aluminum.

8. The method according to any one of the preceding claims, wherein the active metal promoter and / or the reductor is applied to the porous support by vapor phase deposition.

9. The method according to any one of the preceding claims, wherein the porous carrier is selected from the group consisting of porous silicate minerals, zeolites, phyllosilicates, clays, pillard clays, hydrotalcites, and heteropolyacids of molybdenum and tungsten.

10. The method according to any one of the preceding claims, wherein the carrier is selected from the group of carriers, which is formed from mordenite, MCM-41, MCM-48, SBA-15, VPI-5 and Cloverite.

11. The method according to any one of the preceding claims, wherein a maximum temperature of 200 ° C is not exceeded during the manufacture of the catalyst.

12. Catalyst, in particular for methanol synthesis, with a porous support, and at least one active metal deposited on the support and at least one promoter deposited on the support, the porous support having a specific surface area of at least 500 m ² / g, the active metal a specific surface area of at least 25 m ² _A tivmetaiι / gAktiwetaiι and the promoter has a specific 0- surface of at least 100 m ² / gp _rθ motor.

13. The catalyst of claim 12, wherein the active metal has an average coordination number of at most 10.

4. Use of a catalyst according to claim 11 for methanol synthesis or as a reformer for fuel cell technology.