Title of Invention	PREPARATION OF METAL/METAL OXIDE SUPPORTED CATALYSTS BY PRECURSOR CHEMICAL NANOMETALLURGY IN DEFINED REACTION CHAMBERS OF POROUS SUPPORTS USING ORGANOMETALLIC AND/OR INORGANIC PRCURSORS AND REDUCTANTS CONTAINING METAL
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 m<2>/g and is also charged with a content of at least one catalytically active metal component amounting to at least 2.5 m<2> 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.

Title of Invention

PREPARATION OF METAL/METAL OXIDE SUPPORTED CATALYSTS BY PRECURSOR CHEMICAL NANOMETALLURGY IN DEFINED REACTION CHAMBERS OF POROUS SUPPORTS USING ORGANOMETALLIC AND/OR INORGANIC PRCURSORS AND REDUCTANTS CONTAINING METAL

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 m<2>/g and is also charged with a content of at least one catalytically active metal component amounting to at least 2.5 m<2> 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.

Full Text	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 The invention relates to a process for preparing a catalyst, to a catalyst obtainable by the process, and to its use. In the industrial synthesis of methanol, Cu/ZnO systems which are usually supplemented by A12O3 are used as catalysts. These catalysts are prepared on a large scale by precipitation reactions. Copper and zinc act as catalytically active substances, while the aluminium oxide is believed to have a thermally stabilizing action as structural promoter. The atomic ratios of copper to zinc can vary, but copper is generally present in excess. Such catalysts are known, for example, from DE-A-2 056 612 and US-A-4,279,781. A corresponding catalyst for the synthesis of methanol is also known from EP-A-0 125 689. This catalyst is characterized in that the proportion of pores having a diameter in the range from 20 to 75 A is at least 20% and the proportion of pores having a diameter of more than 75 A is not more than 80%. The Cu/Zn atomic ratio is from 2.8 to 3.8, preferably from 2.8 to 3.2, and the proportion of A12O3 is from 8 to 12% by weight. A similar catalyst for the synthesis of methanol is known from DE-A-44 16 425. It has an atomic ratio of - 2 - Cu/Zn of 2:1 and generally comprises from 50 to 75% by weight of CuO, from 15 to 35% by weight of ZnO and additionally contains from 5 to 20% by weight of A12O3. 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 comprises (a) copper oxide and zinc oxide, (b) aluminium oxide as thermally stabilizing substance and (c) at least one alkali metal carbonate or alkali metal oxide, with the oxidic precursor having a proportion of pores having a diameter in the range from 15 to 7.5 nm of from 20 to 70% of the total volume/ the alkali metal content being from 13 to 130 x 10-6 per gram of the oxidic precursor and the aluminium oxide component having been obtained from a colloidally dispersed aluminium hydroxide (aluminium hydroxide sol or gel). In the processes used hitherto for preparing catalysts for the synthesis of methanol, the loading of the support with appropriate precursor compounds of the catalytically active metals is usually followed by a plurality of oxidative and/or reductive preparation steps, usually using air or oxygen as oxidizing agent and hydrogen as reducing agent, at relatively high temperatures. In addition, these processes usually encompass a plurality of calcination steps, typically at 250-400°C. Particle growth of the catalytically active reaction sites occurs during these process steps, which leads to a reduction in the catalytic activity. The Cu/ZnO system is the basis of the industrial synthesis of methanol and an important component in fuel cell technology (reformer) . It is the prototype for research on synergistic metal/support interactions in heterogeneous catalysis [P.L. Hansen, J.B. Wagner, S. Helveg, J.R. Rostrup-Nielsen, B.S. Clausen, H. Topspe, - 3 - M. Science 2002, 295, 2053-2055]. Thus, studies carried out using high-resolution in-situ transmission electron microscopy (TEM) discovered dynamic shape changes in ZnO-supported Cu nanocrystallites (2-3 nm) as a function of the redox potential of the gas phase. Under the reducing conditions (Ha/CO) of the methanol synthesis, flattening of the Cu particles occurs and the ZnO support is significantly .more strongly wetted. In addition, there is a positive correlation between the degree of distortion of ZnO-supported Cu nanoparticles and the catalytic activity. The formation of Cu/Zn alloys is also of significance, as the promotion of Cu (111) surfaces as a result of Zn deposition demonstrates. Zeolites and zeolite-like structures, e.g. mordenite, VPI-5 or cloverite, and periodic mesoporous silicate minerals (PMS) such as MCM-41, MCM-48 or SBA-15, have, owing to their very high specific surface areas and the pore structure which can be set precisely in the sub-nm region, been found to be excellent supports for many catalytically active species, and Cu/PMS and CuOx/PMS materials in particular have been intensively studied. However, these Cu/PMS and CuOx/PMS materials are inactive or significantly less active in the synthesis of methanol [K. Hadjiivanov, T. Tsoncheva, M. Dimitrov, C. Minchev, H. Knozinger, "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 vapour deposition is known for a few metals, e.g. 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 H2", Chemistry Letters 1998, 315] or Pd - 4 - [C.P. Mehnert, D.W. Weaver, J.Y. Ying, "Heterogeneous Heck catalysis with palladium-grafted molecular sieves", Journal of the American Chemical Society 1998, 120, 12289] and for A12O3 [A.M. Uusitalo, T.T. Pakkanen, M. Kroger-Laukkanen, L. Niinisto, K. Hakala, S. Paavola, B. Lofgren, "Heterogenization of racemic ethylenebis(1-indenyl)zirconium dichloride on trimethylaluminum vapor modified silica surface", Journal of Molecular Catalysis A-Chemical 2000, 160, 343.] . It is an object of the invention to provide a process for preparing catalysts, in particular for the synthesis of methanol, by means of which catalysts having a very high activity can be obtained. This object is achieved by a process having the features of Claim 1. Advantageous embodiments of the process of the invention are subject-matter of the dependent claims. The invention provides a process for preparing a catalyst comprising a porous support, at least one active metal and at least one promoter. The catalyst is, in particular, suitable for the synthesis of methanol. In the preparation, a porous support having a specific surface area of at least 500 m2/g is made available. At least one active metal precursor comprising at least one active metal in a reducible form and at least one group bound via a ligator atom preferably selected from among oxygen, sulphur, nitrogen, phosphorus and carbon to the active metal atom is applied to the porous support. The active metal precursor is reduced by means of a reductor comprising at least one promoter metal and at least one hydride group and/or an organic group bound via a carbon atom to the promoter atom. The reductor or the promoter metal present in this is finally converted into the promoter. The promoter is usually formed by an oxide of - 5 -the promoter metal. The active metal precursor preferably has at least two groups bound via a ligator atom selected from among oxygen, sulphur, nitrogen, phosphorus and carbon to the active metal atom. The reductor likewise preferably has at least two hydride groups and/or organic groups bound via a carbon atom to the promoter atom, preferably from the group consisting of alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof. For the purposes of the present invention, a "porous support" is preferably a support which has voids which are open on at least one side. The opening of these voids has a diameter of from about 0.7 to 20 nm, preferably from about 0.7 to 10 nm, particularly preferably from about 0.7 to 5 nm, along at least one dimension. The term "void" is to be interpreted broadly. Such a void can be, for example, an approximately spherical void or a channel having a defined geometry, as is found, for example, in zeolite materials. However, the void can also be formed between two layers, for example in sheet silicates. However, the void has a comparatively small opening, so that the active metal precursor can diffuse into the void and be precipitated there in a controlled fashion. For this reason, the abovementioned diameter of from about 0.7 to about 20 nm essentially corresponds in the case of sheet silicates to the sheet spacing. In the case of spherical voids, the porous support has pores having an approximately spherical outline. The size of the opening of the void can be determined by nitrogen adsorption measurements in accordance with the BJH method (DIN 66134). - 6 - The porous supports preferably have a pore volume of more than 0.09 cm3/g, particularly preferably more than 0.15 cm3/g. If zeolites are used as supports, the pore volume is preferably less than 1.5 cm3/g. MOF systems ("metal organic framework") are also suitable as supports. These systems comprise metal atoms which are three-dimensionally linked via organic ligands to form a network and are suitable, for example, for hydrogen storage. These compounds have very high pore volumes of up to 10 cm3/g and very high specific surface areas of more than 1000 m2/g, particularly preferably more than 2000 m2/g. The porous support has a high specific surface area of at least 500 m2/g, preferably at least 600 m2/g, more preferably more than 800 m2/g, particularly preferably more than 1000 m2/g. The specific surface area is determined by nitrogen adsorption measurement in accordance with the BET method (DIN 66131). At least one active metal precursor comprising at least one active metal in a reducible form and a.t least one group bound via a ligator atom to the active metal is then applied to the porous support. The active metal atom is thus present in an oxidation state of greater than zero in the active metal precursor. For the present purposes, an active metal is a metal which in the finished catalyst displays a catalytic effect in respect of the reaction to be catalysed. In the case of a catalyst for the synthesis of methanol, this is, for example, copper which in the active form of the catalyst is present as metal. Correspondingly, an active metal precursor is a compound from which the active metal can be set free. In the process of the invention, compounds containing at least one atom of the active metal and at least one group bound via a ligator atom to the active metal atom are used as active metal precursors. The ligator atom is selected - 7 - from among oxygen, sulphur, nitrogen, phosphorus and carbon. The active metal preferably bears organic groups, i.e. groups which have at least one carbon atom in addition to the ligator atoms 0, S, N and P. These organic groups preferably have from 1 to 24 carbon atoms, in particular from 1 to 6 carbon atoms. The carbon framework can bear, in addition to the ligator atom, further heteroatoms or heteroatomic groups which can coordinate as Lewis bases to the active metal and thereby stabilize the active metal precursor. Suitable organic groups are, for example, alkoxides or amino-functionalized alkoxides. The active metal precursor is reduced by means of a reductor to precipitate the active metal on the walls of the pores. For the purposes of the present invention, a reductor is an organometallic compound which can reduce the active metal precursor to precipitate the active metal on the porous support. The promoter metal is set free from the reductor and is precipitated as promoter, usually in the form of the oxide, to the support in preferably nanodisperse form. The reductor therefore comprises at least one promoter metal and at least one hydride group and/or an organic radical bound via a carbon atom to the promoter metal. Bonding can in this case be either via a s bond or a p bond. The groups in the active metal precursor are preferably bound to the active metal via a ligator atom other than carbon, preferably via an oxygen atom or a nitrogen atom. However, if the groups on the active metal and on the promoter metal are both bound via a carbon atom to the metal atom, then the molecular weight of the groups of the reductor is preferably lower than the molecular weight of the groups of the active metal precursor. The groups bound in the reductor preferably have from 1 to 24, particularly preferably from 1 to 6, carbon atoms and may also have groups which are bound via a hetero-atom and can act as Lewis bases and thus stabilize the - 8 - reductor. The groups in the reductor are preferably-selected from among alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof and also a hydride group. For the purposes of the present invention, a promoter metal is the metal which forms the promoter in the finished catalyst. The promoter is generally present as oxide. In the case of a catalyst for the synthesis of methanol, zinc and optionally aluminium form the promoter metals. Particular organometallic compounds can thus be advantageously used as active metal precursors or as reductors in the process of the invention. For the present purposes, organometallic compounds are: 1. metal complexes in which direct metal-carbon bonds are present; 2. metal complexes in which no metal-carbon bond is present but (coordinated) ligands which are organic in nature, i.e. belong to the family of hydrocarbon compounds and derivatives thereof, are present. The term "organometallic" thus makes a distinction from purely inorganic metal complexes which 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 support is not subject to any restrictions per se. The support can firstly be impregnated with the active metal precursor and the reductor can then be applied to precipitate the active metal on the support. However, it is also possible to apply the reductor to the support first and to apply the active metal precursor subsequently. It is also possible to apply the active metal precursor and the reductor alternately to the support a number of times. The active metal - 9 - precursor or the reductor is firstly physisorbed or chemisorbed on the surfaces of the porous support, in particular on the surfaces of the voids. The active metal is then set free Erom the active metal precursor and precipitated by addition of the other component. In the process of the invention, use is made of specific support materials onto which the active metal and the promoter are precipitated. The support materials have a high porosity which can be set in the nanometre range and thus an extremely high specific surface area. The inventors conceive of a model in which the voids or pores act as dimensionally restricted reaction chambers for the reduction of the active metal precursor, so that undesirable particle growth during preparation of the catalyst does not occur. The void has a comparatively small opening, so that the active metal precursor can diffuse into the void and be precipitated there in a controlled fashion. For this reason, only a limited amount of the active metal precipitates in each void. The active metal after it has been set free is therefore distributed in nanodisperse form on the walls of these reaction chambers. The maximum diameter of the particles does not exceed the pore diameter, which, for example, is 2 nm when using an MCM-41, in at least one direction. In further process steps in which the catalyst is, for example, heated to relatively high temperatures, no exchange occurs between the various voids, so that growth of the catalytically active particles is suppressed and the nanodisperse distribution of the catalytically active sites is maintained. In addition, this has a favourable influence on the long-term stability of the catalysts under process conditions. The active metal precxarsors and the reductors are preferably adsorbed on the internal surface area of these support materials and thus come into direct chemical proximity in a very controllable fashion. This has a positive effect both on the efficiency of the - 10 - reduction process and on the dispersion of the active metal particles and the promoter components. This ensures, in a novel way, a close surface or interfacial contact of support, active metal particles and promoter components necessary for the catalytic properties. If the catalytically active metal component comprises a plurality of metals or metal compounds, for example metal oxides, these are in intimate contact since the individual constituents are each present in nano-disperse form. The particular characteristic of the process of the invention is that, in contrast to other known impregnation processes, the active metal is deposited and chemically fixed by means of a chemical reaction between the active metal precursors and the reductors (reduction or cr bond metathesis or the like) in a restricted nanosize reaction chamber formed by the supports, i.e. in catalytically relevant close proximity. In the air-stable storage form of the catalyst, the active metals are usually present in the form of an oxide. Exceptions are very noble active metals, e.g. Pt and Pd, etc. The oxides are formed as a result of oxidation by air after the preparation of the catalyst. However, it is also possible to oxidize only a proportion of the metal form by means of specific stabilizing measures in an established manner known from the prior art. Here, the active metal is passivated by a thin oxide layer. After being introduced into the reactor, the catalyst can then be converted back into its active form by means of a mild and simple rereduction. For this purpose, these oxide layers are reduced, for example, by means of hydrogen. In particular with a view to regeneration of the catalyst, the quality of the catalytic activity of the system and its chemical composition and structural characteristics is not altered by repeated oxidation - 11 - and reduction cycles; i.e. appropriate regeneration of the catalyst to restore the original catalytic activity is possible in an advantageous manner. 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 abovementioned group, for example copper or zinc. However, it is also possible for the active metal to comprise a plurality of metals from the abovementioned group, for example two or three metals. The metals can be present in reduced form as pure metal or else as a metal compound, in particular as metal oxide. As mentioned above, the active metal is usually present in the transport form of the catalyst in at least partly oxidized form, so that the catalyst is also sufficiently stable in air. In a preferred embodiment, the promoter metal is selected from the group consisting of Al, Zn, Sn, rare earth metals and alkali metals and alkaline earth metals. Suitable alkali metals and alkaline earth metals are, for example, Li, Na, K, Cs, Mg and Ba. Different metals are selected as active metal and promoter metal for the catalyst. Specific metal-containing reducing agents, here referred to as reductors, are thus used in the process of the invention. These reductors set the active metals important for the catalytic properties free from the corresponding chemical precursors (active metal precursors) in which these metals are present in defined, bound form by means of a particularly efficient but at the same time very mild chemical reduction. Reductors used are organometallic compounds containing a metal which acts as promoter for the catalytically active active metal. - 12 - If a catalyst for the synthesis of methanol or a reformer for fuel cell technology is prepared by the process of the invention, the catalyst preferably comprises the system, Cu/Zn/Al. Here, the atomic ratios of Cu/Zn/Al are in typical ranges from 1:2:0.1 to 2:1:1. The copper can be introduced by means of a suitable active metal precursor, the zinc can be introduced via the reductor and the aluminium can be introduced via the porous support. The active metal precursor is preferably a compound of the formula MeXpLo, where Me is an active metal, X is selected from the group consisting of alkoxides (OR), amides (NR2) , b-diketonates (R* (=O) CHC(=O)R) and their nitrogen analogues, in particular b-ketoiminates (R(=O)CHC(=NR)R) and b-diiminates (R(=NR)CHC(=NR)R), carboxylates (RCOO), oxalates (C2O4) , nitrates (NO3) and carbonates (CO3) , where R is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, and the radicals R* can be identical or different, p is an integer corresponding to the valency of the promoter metal, o is an integer from 0 to the number of free coordination sites on the promoter metal atom and L is an organic Lewis, base ligand containing oxygen or nitrogen as ligator atom. L and X can here encompass only one type of the ligands or radicals mentioned. However, it is also possible to envisage combinations of the groups mentioned. In one embodiment of the process of the invention, the reductor is a compound of the formula MRnLm, where M is a promoter metal, R is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, a cyclopentadienyl radical or derivatives thereof, or a hydride group, with the radicals R being - 13 - able to be identical or different, n is an integer corresponding to the valency of the metal, L is an organic Lewis base ligand containing oxygen or nitrogen as ligator atom and m is an integer from 0 to the number of free coordination sites on the active metal atom. In the case of the reductor too, only one type of radicals or ligands can be used for the radical R and the ligand L. However, it is likewise possible to combine various groups. As ligands L, it is possible to use, for example, compounds of the formula OR'R' or NR'R'R'', where the radicals R' , R' ' and R' ' ' are each an alkyl group having from 1 to 6 carbon atoms, with it also being possible for two of these radicals together with the heteroatom to form a ring. Particular preference is given to reductors of the formula MRnLm selected from among ZnR2Lm and AlR3Lm, where m = 0, 1 or 2 and R and L are as defined above. In general, the active metal precursors applied to the porous support are selected so that they react with one another or with the abovementioned reductors as a result of complete or partial X/R exchange in the restricted reaction chambers of the supports to form species of the composition MeRx (x The abovementioned active metal precursors and reductors can be applied as solution to the porous support. The solvent and the active metal precursors or reductors are matched to one another so that no decomposition occurs in the solvent. After loading of the support with the active metal precursor, the - 14 - solvent together with excess active metal precursor is removed. To remove solvent residues, the laden porous support can, if appropriate, firstly be dried. The reductor, which is once again an organometallic compound, is subsequently applied to the porous support. The reductor reduces the active metal precursor applied initially, so that the catalytically active metal is precipitated and fixed on the porous support. However, this procedure can also be carried out in the reverse order, i.e. the porous support is firstly 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 vapour deposition (CVD). In this case, the active metal precursors or the reductors preferably have a vapour pressure of at least 0.1 mbar at 298 K. In a particularly preferred embodiment of the process of the invention, organometallic complexes are therefore used both as active metal precursors and as reductor. Combinations of these methods are also possible. For example, the active metal precursor can be applied as a solution and the reductor can subsequently be applied by chemical vapour deposition. Likewise, it is also possible for the active metal precursor to be applied first by vapour deposition and the reductor subsequently to be applied as a solution. The porous support can consist of any desired material. However, the support should have the above-described voids which have a relatively small opening having the dimensions indicated above. Thus, for example, the abovementioned MOF systems are suitable as porous support materials. Since the catalysts are usually employed at elevated temperature, it is preferred that the support is made up of an inorganic material. Examples of suitable inorganic materials are zeolites, - 15 - PMS, sheet silicates such as bentonites, clays or pillard clays, hydrotalcites and heteropolyacids, e.g. of molybdenum and tungsten. However, particular preference is given to using periodic mesoporous silicate materials (PMS) since these have very high specific surface areas and the pore structure can be set precisely in them. Examples are MCM-41, MCM-48 and SBA-15. Among the zeolites, preference is given to those which have a large pore radius. Zeolites having a pore radius of > 0.7 ran are, for example, mordenite, VPI-5 or cloverites. The preparation of the catalyst is carried out under extremely mild conditions. Thus, a temperature of 200°C is preferably not exceeded during the preparation of the catalyst. The active metal is as a result deposited in finely divided form, with the diameter of the particles of active metal produced generally being in the range from about 0.5 to 10 nm, preferably from 0.5 to 5 nm. The promoter, too, is deposited in finely divided form, so that a very large contact area between active metal and promoter can be achieved. This leads to catalysts having a very high activity. The invention therefore also provides a catalyst, in particular for the synthesis of methanol, comprising a porous support and at least one active metal precipitated on the porous support and at least one promoter precipitated on the porous support, wherein the porous support has a specific BET surface area of at least 500 m2/g, the active metal has a specific metallic surface area of at least 25 m2active metal/gactive metai and the promoter has a specific surface area of at least 100 m2/gpromoter, preferably at least 500 m2/gprOmoter• The specific surface area of the active metal can be determined by gas adsorption/desorption methods or by - 16 - reactive gas adsorption/desorption methods. An example of such a method is N20 reactive frontal chromatography for determining the specific surface area of copper. Analogous methods can be employed for other active metals. They are generally based on the occupation of the metal surface by a molecule having a known space requirement, with the amount of adsorbed molecules being determined. The specific surface area of the promoter can be estimated by determination of the degree of aggregation via X-ray absorption studies and by BET surface area determination on the laden support. The content of promoter component can be determined by means of elemental analysis (e.g. atomic absorption spectroscopy or , energy-dispersive X-ray absorption spectroscopy). A distinguishing feature of the catalysts prepared by the process of the invention compared to the catalysts prepared by alternative methods, in particular by coprecipitation/calcination, is the extremely low, even vanishing degree of aggregation of the promoter component (which can be determined by means of X-ray absorption studies) combined with a high BET surface area of the active catalyst of preferably far above 500 m2/g. It is usually not possible to determine any measurable degree of coordination. When the catalysts are examined by X-ray diffraction methods, no reflections for the promoter are observed in this case. When the catalyst is examined by X-ray absorption spectroscopy, only very low aggregation states are observed. This means that the atoms which are two or three atoms removed from a promoter atom are normally not promoter atoms. In general, the first other promoter atom is at least two or three atoms removed from a promoter atom. In other words, the promoter is preferably in the form of an at most two- or three-shell promoter. The degree of aggregation of the active metal component - 17 - is also typically very low, which is reflected, in particular, in the metal particles, e.g. copper, being so homogeneously distributed on the (internal) surface area of the support and having such small dimensions that they cannot be detected and characterized as well-formed particles by transmission electron microscopic methods, while a small but measurable degree of aggregation of the majority of the particles can be characterized as described by X-ray absorption measurements. The active metal preferably has a mean coordination number of not more than 10 in the catalyst of the invention. The coordination number is preferably less than 10, particularly preferably in the range from 4 to 7. A 'coordination number of about 6 is often 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, e.g. for transport from the place where it is prepared to the synthesis reactor. The maximum crystallite size of the active metal or of the promoter is in each case limited in one dimension by the maximum pore diameter. The catalyst of the invention comprises a porous support which preferably has voids open on at least one side. The opening of these voids has a diameter of from about 0.7 to about 20 nm, preferably from about 0.7 to 10 nm, particularly preferably from about 0.7 to 5 nm, along at least one dimension. Furthermore, the porous support has a high specific BET surface area of at least 500 m2/g, preferably at least about 600 m2/g, particularly preferably at least about 800 m2/g. These high specific surface areas are also measured on the finished catalyst. Although the specific surface area is reduced by application of the active metal and the promoter, the finished catalyst nevertheless has a BET surface area of at least 500 m2/g, preferably at least about 600 m2/g, particularly preferably at least about - 18 - 800 m2/g, which is very high compared to conventional catalysts. The porous support is laden with at least one catalytically active metal component which is present in finely divided form. The loading is at least about 2.5 m2active metal g-1catalyst, preferably at least about 3 m2active metal g-1ataiyst. particularly preferably about 5 m2active metal g-1cataiyst• However, an even higher loading can be achieved. This can be in the range from > 10 m2active metal/g-1 Catalyst to more than 20 inactive metal/ g-1catalyst. In other words, the loading with the active metal is at least about 25 m2active metai g-1active metal, preferably at least about 35 m2actlve metai g-1active metai, particularly preferably at least about 50 m2active metai g-1Active metal. In particularly preferred cases, the loading is accordingly more than 100 m2active metai g-1active metai/ in particularly preferred Cases more than 200 m2active metal g-1active metal- The loading of the catalyst with the active metal is preferably in the range from about 0.05 to 0.50 gactive metai g-1cataiyst, preferably from about 0.1 to 0.45 gactive metai g-1cataiyst, particularly preferably from about 0.1 to 0.3 0 gactive metai g-1Catalyst/ and the loading with the promoter is preferably in the range from about 0.01 to 0.3 gPromoter g-1Catalyst, preferably from about 0.05 to 0.2 gPromoter g-1cataiyst, particularly preferably from about 0.05 to 0.15 gpromoter g-1catalyst. The values and ranges indicated are in each case based on the metal or the promoter metal. The ratio of active metal/promoter metal is preferably in the range from about 10:1 to 1:5, more preferably from about 5:1 to 1:2, in particular from about 5:1 to 1:1. Preference is given to introducing a very large amount of active metal and very little promoter in the preparation of the catalyst. The preferred supports and active metals and promoters have been described above in connection with the process of the invention. - 19 - The catalyst obtainable by the process of the invention brings a series of advantages which are illustrated below for, by way of example, an embodiment of the catalyst of the invention as catalyst for the synthesis of methanol. The catalyst of the invention is distinguished from the known Cu/Zn/Al catalysts for the synthesis of methanol by the following criteria: (1) The dispersion of the Cu component (or the active metal) is higher, namely at least 25 m2cu g-1cu, i.e. the catalyst of the invention is more active at the same proportion by mass of catalytically active Cu component or a lower proportion by mass of copper (active metal) is sufficient to achieve the same activity in the case of the catalyst of the invention compared to known catalysts. Analytical characterization of the catalyst by means of EXAFS (extended X-ray absorption fine structure spectroscopy) and XRD (X-ray diffraction) indicates that the majority of the Cu particles have a dimension close to or below 1 nm, implying typical aggregates of 10-20 Cu atoms, and the minority of Cu particles has dimensions up to the channel or pore width of the PMS support material. (2) In contrast to known Cu/ZnO/Al2O3 catalysts, the ZnO component and the aluminium oxide component (promoter) is not aggregated in an ordered manner. Rather, they form, according to EXAFS data, a thin coating on the interior walls or surfaces of the support material. In this way, the specific surface area of the ZnO component reaches values in the order of the specific surface area of the support material (> 500 m2/g) and far exceeds the specific BET surface areas of previously known - 20 - high-surface-area ZnO support materials, viz. up to about 150 m2 g-1. [M. Kurtz, N. Bauer, C. Buscher, H. Wilmer, 0. Hinrichsen, R. Becker, S. Rabe, K. Merz, M. Driess, R.A. Fischer, M. Muhler, "New synthetic routes to more active Cu/ZnO catalysts for methanol synthesis", Catalysis Letters 2004, 92, 49; C.R. Lee, H.W. Lee, J.S. Song, W.W. 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, S.E. Pratsinis, "Homogeneous ZnO nanoparticles by, flame spray pyrolysis", Journal of Nanoparticle Research 2002, 4, 337.]. -In contrast to known Cu/ZnO/Al2O3 catalysts, the catalyst of the invention contains no nanocrystalline ZnO or A12O3 components which can be detected by TEM or XRD methods. These criteria apply not only to a catalyst for the synthesis of methanol using the system Cu/ZnO/Al2O3, but can be carried over to all catalysts obtainable by the process of the invention. The catalysts of the invention have a very high activity based on the proportion by mass of the cata-lytically active metal components. They are therefore particularly suitable for use as catalysts for the synthesis of methanol or as reformers in fuel cell technology. In summary, it can be stated that, taking into account preferred embodiments the advantages of the invention are: 1. the mild process conditions (in particular relatively low preparation temperatures, in particular temperatures of less than 200°C) which suppresses - 21 - undesirable particle growth processes which were unavoidable according to the prior art; 2. the combination of active metal precursors with metal-containing reducing agents (reductors) which make it possible to achieve an extraordinarily- high dispersion of active metal components (active metals) and promoter components together with a high surface or interfacial contact of metal/metal oxide-promoter. The latter leads to an improvement in the specific activity and selectivity of the catalysts; 3. the opportunity provided by the novel process of controlling the composition of the catalyst system while maintaining an unchanged high dispersion by means of permutation and/or cyclic repetition of the individual loading or reactions steps; 4. the elimination of problematical salt and/or stabilizer burdens, as result, for example, from impregnation techniques based on colloid-chemical processes according to the prior art; 5. the use of porous support materials as dimen- sionally restricted reaction chambers for the metathetic surface reaction between various precursors which is necessary for success. The dimensionally restricted reaction chambers (geometrically defined by the pore characteristics of the porous support systems) suppress unwanted particle growth due to their intrinsic geometry. In particular, this is aided by the larger optimized ratio of surface area to volume of porous supports compared to supports having a relatively low porosity. The support properties mentioned thus counter segregation of the components. This ensures a high dispersion of the catalytically active components and a high - 22 -specific loading of the support. The invention is illustrated below with the aid of examples with reference to the accompanying figures. In the figures: Fig. 1 shows a highly schematic presentation of the mechanism by which the deposition of the active metal and the promoter metal proceeds in the process of the invention; Fig. 2 shows X-ray powder diffraction patterns of the samples: a) the precursor Cu/ [Zn(0CHMeCH2NMe2)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. As a guide, the (111) , (200) and (220) reflection planes of polycrystalline copper are marked on the abscissa. Fig. 3 shows small-angle powder diffraction patterns of a) empty, calcined MCM-41 and b) Cu/ZnO/MCM-41. The characteristic drop in intensity of b) compared to a) is an indication of the loading of the pores. In the transmission electron micrograph also obtained on a Cu/ZnO/MCM-41 sample, the intact pore structure can clearly be seen; however, copper particles or zinc oxide particles cannot be identified because of their small size. The presence of copper and zinc is evidenced by the associated EDX spectrum (element dispersive X-ray fluorescence analysis). Fig. 4 shows a) CuK XANES and b) Cult EXAFS spectra (absolute value of the Fourier transforms) of - 23 - Cu/ZnO/MCM-41 and reference substances, c) analysis of the spectrum of Cu/ZnO/MCM-41; modelling parameters: nearest neighbour Cu; spacing (R) = 2.512 ± 0.002 A, coordination number (N) =5.8+0.3, Debye-Waller factor (a2) = (9.6 + 0.4) 10-3 A2. Nearest neighbour 0: R = 1.86 ± 0.04 A, N = 0.3 ± 0.1, O-2 (7 ± 0.11) 10-3 A2. Fig. 5 shows the reaction of [Cu(OCHMeCH2NMe2)2] with diethylzinc in the nanotubes of the MCM-41 support material. Fig. 1 shows a schematic presentation of the mechanism according to which the deposition of active metal and promoter occurs in the process of the invention. It goes without saying that this is only a model concept and in no way restricts the scope of the invention. Fig. la shows a section through a porous support 1 in which there is a pore 2 which is open to the outside of the support 1. The support 1 can, for example, be a zeolite. An active metal precursor 3 and a reductor 4 have diffused into the pore 2. Loading can be effected by the porous support 1 firstly being loaded with the active metal precursor 3 and subsequently with the reductor 4. However, it is also possible to load the porous support 1 ' firstly with the reductor 4 and subsequently with the active metal precursor 3. If the mixture of active metal precursor 3 and reductor 4 is sufficiently stable at the loading temperature, loading can also be carried out simultaneously. The active metal precursor 3 comprises an active metal AM to which groups L are bound. In Fig. 1, the active metal AM bears two groups L in the interests of clarity. However, it is also possible for more than two groups L to be present in the active metal precursor 3. Apart from the groups L, the active metal AM can additionally bear further ligands which stabilize the active metal - 24 - precursor, e.g. by coordinate bonding. The groups L are bound via a ligator atom (not shown) to the active metal AM. The ligator atom is selected from among oxygen, sulphur, nitrogen and carbon. The reductor 4 comprises a promoter metal PM to which organic groups R are bound via a carbon atom. In Fig. 1, the reductor has only two groups R in the interests or clarity. However, it is also possible for more than two groups R to be bound to the promoter metal PM or for further groups in addition to the groups R to be bound to the promoter metal PM. The letters x and y correspond to the molar ratio of active metal promoter 3 and reductor 4 employed. As central step in the deposition, ligand exchange between active metal AM and promoter metal PM then occurs. This is shown in Fig. lb. This results in a reactive intermediate 5 which comprises the active metal AM and the, groups R. In addition, the promoter compound 6 comprising the promoter metal PM •and the groups L is obtained. The reactive intermediate 5 subsequently decomposes. This decomposition process is, for example, aided or induced by heating. The active metal present in the reactive intermediate 5 is reduced to the active metal AM and deposits in nanodisperse form as crystallites 7 on the walls of the pores 2 (Fig. lc). At the same time, the compound R-R is formed from the groups R, e.g. in a metathesis reaction. This compound can be taken off as offgas. The promoter compound 6 is oxidized so that the promoter metal is likewise precipitated as promoter PR, for example in the form of an oxide, 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 liberated in this reaction and can likewise be taken off with the offgas. Example 1: Cu/ZnO/MCM-41 Freshly synthesized, calcined and dry MCM-41 (350 mg) and a portion of about 1.0 g of [Cu(OCHMeCH2NMe2) 2] are - 25 - placed in separate glass boats in a Schlenk tube and heated at 340 K in a static vacuum (0.1 Pa) for 2 hours. A sample of 200 mg of the blue-coloured product material and about 0.5 g of diethylzinc are positioned next to one another as above and left at room temperature in a static vacuum (0.1 Pa) for 2 hours. Variation of the vapour deposition time, temperature, molar amounts and PMS material leads to different loadings (Table 1). To produce the ZnO, the Cu/ [Zn(OCHMeCH2NMe2)2] /MCM-41 sample is taken out under protective gas and subsequently heated at 623 K in a dynamic vacuum (0.1 Pa) (2 h) . The procedure is repeated using other PMS materials, e.g. MCM-4 8. Example 2: Cu/MCM-41 and ZnO/MCM-41 Heating of [Cu(OCHMeCH2NMe2) 2] /MCM-41 (see above) at 523 K in a dynamic vacuum (0.1 Pa) (20 min) gives Cu/MCM-41. ZnO/MCM-41 is obtained in an analogous fashion using [Zn(OCHMeCH2NMe2) 2] as ZnO precursor by heating the intermediate [Zn(OCHMeCH2NMe2) 2]/MCM-41 at 623 K (0.1 Pa, 2 h) . [Zn(OCHMeCH2NMe2) 2] /MCM-41 was obtained by impregnating MCM-41 with a solution of [Zn(OCHMeCH2NMe2)2] (1.0 g) in pentane (40 ml) and separating off the solid and washing it a number of times. As an alternative, ZnO/PMS can be obtained by treatment of the supports with diethylzinc vapour and subsequent calcination. Characterization of the samples The X-ray powder diffraction patterns (PXRD) were recorded by means of a D8-Advance Bruker AXS diffractometer using Cu Ka radiation {X = 1.5418 A) in 0-20 geometry and using a position-sensitive detector (capillary technique, protective gas). All diffraction patterns were fitted by means of Profile Plus 2.0.1 software using a pseudo-Voigt function. TEM examinations were carried out using a Hitachi H-8100 instru- - 26 - ment at 200 kV using a tungsten filament (preparation with exclusion of air, Gold-Grids Piano, vacuum transfer holder). X-ray absorption spectra (XAS) were recorded on a Hasylab (DESY, Hamburg) at station XI in the transmission mode using an Si (311) double crystal monochromator (software VIPER). Nitrogen adsorption measurements were carried out using a Quantachrome Autosorb 1 MP apparatus. The pore diameter was calculated by the Barrett-Joyner-Halenda (BJH) method. The specific surface area (SBET) of the empty, calcined MCM-41 and the CuOx/MCM-41 was determined by means of the data of the linear part of the BET graph (p/po = 0.05-0.35) . 27 - 28 - [a] The copper surface area was determined by means of N2O-RFC. After a pretreatment with a dilute H2 atmosphere (2% by volume) , N20 (1% by volume of N20 in He, 3 00 K) was passed over the catalyst and the copper surface area was calculated from the, amount of nitrogen liberated (density of Cu surface atoms: 1.47'1019 m-2) . The activity in the syn thesis of methanol was examined under atmospheric pressure at a temperature of 493 K. A mixture of 72% of H2, 10% of CO, 14% of C02 and 14% of He was used as synthesis gas. The data reported were obtained after a reaction time of 2 hours. Due to the low conversion at atmospheric pressure, no products other than methanol were able to be detected. [b] Catalysis-specific data of catalysts which had been prepared by coprecipitation and whose perfor mance in the synthesis of MeOH was determined under conditions . analogous to those for the Cu/ZnO/PMS samples. The product rates from the regression analysis (production rate as a function of the Cu surface area of the catalysts having different metal concentrations) were interpolated (Cu/ZnO) or extrapolated (Cu/ZnO/Al2O3) to the Cu surface areas found in the Cu/ZnO/PMS. The data for the comparative samples come from: T. Genger, thesis, Ruhr-Universitat Bochum, 2000. [c] Not detectable. Further characterization of the samples: if a portion (350 mg) of pure, freshly calcined MCM-41 (0 BJH = 2.7 nm, SBET = 712 m2 g"1) is exposed to the vapour of an adjacent portion (1.0 g) of the blue-violet Cu precursor [Cu(OCHMeCH2NMe2)2] (1) at 340 K in a static vacuum (0.1 Pa) in a tightly sealed Schlenk tube, the originally colourless silicate material becomes light blue. The Cu precursor - 29 - [Cu(OCHMeCH2NMe2)2] remains intact, as comparison of the IR data of the laden MCM-41 with pure [Cu(OCHMeCH2NMe2)2] shows. The adsorption is strong, since [Cu(OCHMeCH2NMe2) 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 of free silanol groups which is otherwise observed at 3745 cm"1 indicates an interaction of the pore walls with [Cu(OCHMeCH2NMe2)2] , perhaps via hydrogen bonds. If the [Cu(OCHMeCH2NMe2)2]-laden support is then treated with diethylzinc vapour in a second step by placing the two samples next to one another in a Schlenk tube and evacuating and sealing the latter (0.5 g of ZnEt2, 300 K, 0.1 Pa), a colour change from light blue to reddish brown gradually occurs. In the X-ray diffraction pattern of a sample of the material prepared under inert gas in a capillary, a weak, very broad structure appears at 2 8 = 44.70° and can be assigned to the reflection of the [111] lattice plane of small Cu particles {Fig. 2 and 3) . Solid-state NMR spectroscopy reveals [Zn(OCHMeCH2NMe2) 2] (2) as by-product. This reaction occurring in the nanotubes of the PMS corresponds to the quantitative reaction as shown in Fig. 5 which can be carried out on the preparation gram scale in solution, with Cu metal precipitating (XRD), the zinc alkoxide [Zn(OCHMeCH2NMe2)2] remaining in solution (NMR identification) and butane being given off as gas (GC-MS). It is worth noting that when the reactivity of the zinc alkyl used is decreased, e.g. by use of very bulky alkyl radicals such as C(SiMe3)3, the alkyl/alkoxide metathesis does not occur and bimetallic alkylzinc/copper alkoxide complexes were isolated and characterized structurally. The solid-state pyrolysis of these complexes has hitherto led only to micro-crystalline, catalytically inactive Cu/ZnO materials. Gentle heating of the resulting samples Cu/ [Zn(OCHMeCH2NMe2)2] /PMS at 623 K in a dynamic vacuum (0.1 Pa, 2 h) gives predominantly CHx-free materials - 30 - which as before display a very broad Cu(lll) reflection. However, X-ray diffraction does not indicate the presence of ZnO nanocrystallites {Fig. 2). The specific Cu surface areas of the Cu/ZnO/PMS samples were determined as 5-6 m2cu;g-1 cat in each case before and after the catalysis test (Table 1) . The methanol productivities of from 19 to 130 umol'g-1cat'h-1 are in the range of the binary Cu/ZnO catalysts prepared by coprecipitation/calcination or in the case of the MCM-48 sample, are surprisingly significantly superior to these. The three-dimensional pore structure of the MCM-48 support allows efficient diffusion in comparison with MCM-41. The reduction (H2) of completely oxidized samples which have been stored in air (disappearance of the Cu(lll) reflection) restored the original activity and Cu surface area. The comparative samples Cu/MCM-41 (10-12% by weight; 5-7 m2cu'g-1cat) and ZnO/MCM-41, which had been obtained by heating of [M(OCHMeCH2NMe2)2] /MCM-41 (M = Zn, Cu) or treatment of MCM-41 with diethylzinc vapour and calcination, proved to be inactive. Extraordinarily high values for the Cu surface areas of up to 50-60 m2cu'g-1cat were measured on freshly prepared Cu/ZnO/PMS samples during the first oxidation/reduction cycles (N2O/H2) , but these dropped to the characteristic level of 5-6 m2cu'g-1cat during further cycles. This discrepancy is obviously not due to sintering of the Cu particles but is caused by the O-Zn-C2HS groups which are bound to the pore wall of the PMS and are present in excess on the basis of scheme 1, and are likewise oxidized by N20. The EXAFS spectra (Fig. 4) of Cu/ZnO/MCM-41 confirm the presence of very small Cu aggregates. The coordination number of 5.8 and the rather high Debye-Waller factor found for just the first metal shell indicate a high level of defects. On the assumption of spherical, monodisperse particles, a diameter of 0.7 nm can be calculated, corresponding to a cluster of 13 Cu atoms. Even if an underestimation of the particle size because - 31 - of the correlation of coordination number, - and Debye-Waller factor is assumed, the virtually complete absence of higher coordination shells shows that the characteristic dimension of the particles is certainly less than the pore radius of 2-3 ran. The Cu aggregates are present in a particle size distribution of which X-ray diffraction records only the coarse fraction (about 2 nm) . The Cu-Cu contact of 2.50 A6 calculated from the Cu(lll) reflection position of 2 9 = 44.35° corresponds to the value of 2.51 A6 obtained from the EXAFS data and is shortened compared to the Cu-Cu spacing of the bulk phase of 2.56 A6 (effect of small particles). The reason for the Cu-0 coordination found is uncertain. In view of the small mean particle size, it is obvious that oxygen atoms of the pore wall can be recorded in the EXAFS spectrum, as has been described in the literature. The presence of a small proportion of the copper as Cu+ can therefore not be. ruled out. Comparison of the ZnK spectra with test substances (not shown) indicates agreement neither with ZnO nor with Zn. The first 0 sphere has an intensity which is too low and the second sphere (Zn) is virtually completely absent. The fit with Si and Zn separated by one other atom is good, which, in agreement with the solid-state NMR data and the IR data (absence of free silanol groups) , indicates coating of the pore wall with ZnO. The degree of aggregation of the ZnO component is thus vanishing. An analogous situation is found for ZnO/PMS materials which have been obtained by aqueous impregnation/calcination techniques. Clear indications of CuZnOx 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/Al2O3 (I), Cu/ZnO (II) and the ternary system Cu/ZnO/Al2O3 (III) . In the case of materials prepared by classical methods, the activity at a different level in each case, increasing - 32 - from I to III, correlates linearly with the specific Cu surface area. Our activity found for the sample Cu/ZnO/MCM-48 of 13 0 umol -g-1 cat 'h-1 is thus far above the value to be expected for binary Cu/ZnO catalysts having the same specific surface area and is in the range III. Interactions of the Cu particles with the silicate matrix can hardly be responsible for this, since Cu/PMS comparative samples were inactive and the pore walls of the active Cu/ZnO/PMS samples are, as indicated above, obviously coated with ZnO. Rather, the simultaneously high dispersion of Cu and ZnO components appears to be a new, positive effect. An aggregated, (nano)crystalline ZnO phase as is inevitably obtained using coprecipitation/calcination procedures is quite clearly not necessary for the synergistic effect. This is supported by the Cu/Zn alloy formation cited at the outset and also our further observations, namely that a Cu/Al2O3 catalyst prepared by classical methods experienced an activity jump to above the region of the ternary systems as a result of even a short treatment with diethylzinc vapour. In addition, the use of a specific, nanodisperse ZnO support material having a particularly high surface area or level of defects (153 m2-g-1), which was obtained by solid-state pyrolysis of [ (Me3SiO) ZnMe] 4, led to an extraordinarily active, binary Cu/ZnO catalyst. The advantageous aspects of the process of the invention for the loading of PMS support materials, in particular for the preparation of Cu/ZnO catalysts are: not only the variation of dimensions and structure of the pores (e.g. MCM-41 vs. MCM-48 or other appropriate support materials) but also exploitation of the chemistry of the precursor substances allows molecular control over the active metal/promoter contact, for example the Cu/ZnO contact. The results indicate that nothing fundamental should stand in the way of the process of the invention surprisingly giving a simultaneous maximization of the specific active metal - 33 - surface areas (e.g. Cu surface area and the Cu/ZnO interfacial contact or the ZnO dispersion) and the interfacial contact between active metal/metal oxide or promoter so as to increase the catalyst activity far above that which has been possible hitherto. - 34 -Claims 1. Process for preparing a catalyst which comprises a porous support, at least one active metal and at least one promoter and is suitable, in particular, for the synthesis of methanol, wherein a porous support having a specific surface area of at least 500 m2/g is made available, at least one active metal precursor comprising at least one active metal in a reducible form and at least one group bound via a ligator atom preferably selected from among oxygen, sulphur, nitrogen, phosphorus and carbon to the active metal atom is applied to the porous support, the active metal precursor is reduced by means of a reductor comprising at least one promoter metal and at least one hydride group and/or an organic group bound via a carbon atom to the promoter atom, and the reductor is converted into the promoter. 2. Process according to Claim 1, wherein the at least one organic group on the reductor is selected from among alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof and a hydride group. 3. Process 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. Process according to any of the preceding claims, wherein the promoter metal is selected from the group consisting of Al, Zn, Sn, rare earth metals and alkali metals and alkaline earth metals. 5. Process according to any of the preceding claims, wherein the active metal precursor is a compound of the formula MeXpLo, where Me is an active metal - 35 - precursor, X is selected from the group consisting of alkoxides (OR), amides (NR2) , b-diketonates (R(=O)CHC(=O)R) and their nitrogen analogues, in particular b-ketoiminates (R(=0)CHC(=NR)R) and b-diiminates (R(=NR)CHC(=NR)R), carboxylates (RCOO) , oxalates (C2O4) , nitrates (N03) and carbonates (C03) , where R* is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, and the radicals R* can be identical or different, p is an integer corresponding to the valency of the promoter metal, o is an integer from 0 to the number of free coordination sites on the promoter metal atom and L is an organic Lewis base ligand containing oxygen or nitrogen as ligator atom. 6. Process according to any of the preceding claims, wherein the reductor is a compound of the formula MRnLm, where M is a promoter metal, R is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6" carbon atoms, an aryl radical having from 6 to 18 carbon atoms, a cyclopentadienyl radical or derivatives thereof, or a hydride group, with the radicals R being able to be identical or different, n is an integer corresponding to the valency of the metal, L is an organic Lewis base ligand containing oxygen or nitrogen as ligator atom and m is an integer from 0 to the number of free coordination sites on the active metal atom. 7. Process according to any of the preceding claims, wherein the active metal is copper and the promoter metal is zinc and aluminium. 8. Process according to any of the preceding claims, wherein the active metal promoter and/or the reductor are/is applied to the porous support by - 36 -vapour deposition. 9. Process according to any of the preceding claims, wherein the porous support is selected from the group consisting of porous silicate minerals, zeolites, sheet silicates, clays, pillard clays, hydrotalcites and heteropolyacids of molybdenum and of tungsten. 10. Process according to any of the preceding claims, wherein the support is selected from the group of supports consisting of mordenite, MCM-41, MCM-48, SBA-15, VPI-5 and cloverites. 11. Process according to any of the preceding claims, wherein a maximum temperature of 200°C is not exceeded during the preparation of the catalyst. 12. Catalyst, in particular for the synthesis of methanol, comprising a porous support and at least one active metal precipitated on the support and at least one promoter precipitated on the support, wherein the porous support has a specific surface area of at least 500 m2/g, the active metal has a specific surface area of at least 25 m2active metal/gactive metal and the promoter has a specific surface area of at least 100 m2/gprOmoter. 13. Catalyst according to Claim 12, wherein the active metal has a mean coordination number of not more than 10. 14. Use of a catalyst according to Claim 11 for the synthesis of methanol or as reformer for fuel cell technology.

Full Text

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
The invention relates to a process for preparing a catalyst, to a catalyst obtainable by the process, and to its use.
In the industrial synthesis of methanol, Cu/ZnO systems which are usually supplemented by A12O3 are used as catalysts. These catalysts are prepared on a large scale by precipitation reactions. Copper and zinc act as catalytically active substances, while the aluminium oxide is believed to have a thermally stabilizing action as structural promoter. The atomic ratios of copper to zinc can vary, but copper is generally present in excess.
Such catalysts are known, for example, from DE-A-2 056 612 and US-A-4,279,781. A corresponding catalyst for the synthesis of methanol is also known from EP-A-0 125 689. This catalyst is characterized in that the proportion of pores having a diameter in the range from 20 to 75 A is at least 20% and the proportion of pores having a diameter of more than 75 A is not more than 80%. The Cu/Zn atomic ratio is from 2.8 to 3.8, preferably from 2.8 to 3.2, and the proportion of A12O3 is from 8 to 12% by weight.
A similar catalyst for the synthesis of methanol is known from DE-A-44 16 425. It has an atomic ratio of

- 2 -
Cu/Zn of 2:1 and generally comprises from 50 to 75% by weight of CuO, from 15 to 35% by weight of ZnO and additionally contains from 5 to 20% by weight of A12O3.
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 comprises (a) copper oxide and zinc oxide, (b) aluminium oxide as thermally stabilizing substance and (c) at least one alkali metal carbonate or alkali metal oxide, with the oxidic precursor having a proportion of pores having a diameter in the range from 15 to 7.5 nm of from 20 to 70% of the total volume/ the alkali metal content being from 13 to 130 x 10-6 per gram of the oxidic precursor and the aluminium oxide component having been obtained from a colloidally dispersed aluminium hydroxide (aluminium hydroxide sol or gel).
In the processes used hitherto for preparing catalysts for the synthesis of methanol, the loading of the support with appropriate precursor compounds of the catalytically active metals is usually followed by a plurality of oxidative and/or reductive preparation steps, usually using air or oxygen as oxidizing agent and hydrogen as reducing agent, at relatively high temperatures. In addition, these processes usually encompass a plurality of calcination steps, typically at 250-400°C. Particle growth of the catalytically active reaction sites occurs during these process steps, which leads to a reduction in the catalytic activity.
The Cu/ZnO system is the basis of the industrial synthesis of methanol and an important component in fuel cell technology (reformer) . It is the prototype for research on synergistic metal/support interactions in heterogeneous catalysis [P.L. Hansen, J.B. Wagner, S. Helveg, J.R. Rostrup-Nielsen, B.S. Clausen, H. Topspe,

- 3 -
M. Science 2002, 295, 2053-2055]. Thus, studies carried out using high-resolution in-situ transmission electron microscopy (TEM) discovered dynamic shape changes in ZnO-supported Cu nanocrystallites (2-3 nm) as a function of the redox potential of the gas phase. Under the reducing conditions (Ha/CO) of the methanol synthesis, flattening of the Cu particles occurs and the ZnO support is significantly .more strongly wetted. In addition, there is a positive correlation between the degree of distortion of ZnO-supported Cu nanoparticles and the catalytic activity. The formation of Cu/Zn alloys is also of significance, as the promotion of Cu (111) surfaces as a result of Zn deposition demonstrates.
Zeolites and zeolite-like structures, e.g. mordenite, VPI-5 or cloverite, and periodic mesoporous silicate minerals (PMS) such as MCM-41, MCM-48 or SBA-15, have, owing to their very high specific surface areas and the pore structure which can be set precisely in the sub-nm region, been found to be excellent supports for many catalytically active species, and Cu/PMS and CuOx/PMS materials in particular have been intensively studied. However, these Cu/PMS and CuOx/PMS materials are inactive or significantly less active in the synthesis of methanol [K. Hadjiivanov, T. Tsoncheva, M. Dimitrov, C. Minchev, H. Knozinger, "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 vapour deposition is known for a few metals, e.g. 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 H2", Chemistry Letters 1998, 315] or Pd

- 4 -
[C.P. Mehnert, D.W. Weaver, J.Y. Ying, "Heterogeneous Heck catalysis with palladium-grafted molecular sieves", Journal of the American Chemical Society 1998, 120, 12289] and for A12O3 [A.M. Uusitalo, T.T. Pakkanen, M. Kroger-Laukkanen, L. Niinisto, K. Hakala, S. Paavola, B. Lofgren, "Heterogenization of racemic ethylenebis(1-indenyl)zirconium dichloride on trimethylaluminum vapor modified silica surface", Journal of Molecular Catalysis A-Chemical 2000, 160, 343.] .
It is an object of the invention to provide a process for preparing catalysts, in particular for the synthesis of methanol, by means of which catalysts having a very high activity can be obtained.
This object is achieved by a process having the
features of Claim 1. Advantageous embodiments of the
process of the invention are subject-matter of the
dependent claims.
The invention provides a process for preparing a catalyst comprising a porous support, at least one active metal and at least one promoter. The catalyst is, in particular, suitable for the synthesis of methanol. In the preparation, a porous support having a specific surface area of at least 500 m2/g is made available. At least one active metal precursor comprising at least one active metal in a reducible form and at least one group bound via a ligator atom preferably selected from among oxygen, sulphur, nitrogen, phosphorus and carbon to the active metal atom is applied to the porous support. The active metal precursor is reduced by means of a reductor comprising at least one promoter metal and at least one hydride group and/or an organic group bound via a carbon atom to the promoter atom. The reductor or the promoter metal present in this is finally converted into the promoter. The promoter is usually formed by an oxide of

- 5 -the promoter metal.
The active metal precursor preferably has at least two groups bound via a ligator atom selected from among oxygen, sulphur, nitrogen, phosphorus and carbon to the active metal atom.
The reductor likewise preferably has at least two hydride groups and/or organic groups bound via a carbon atom to the promoter atom, preferably from the group consisting of alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof.
For the purposes of the present invention, a "porous support" is preferably a support which has voids which are open on at least one side. The opening of these voids has a diameter of from about 0.7 to 20 nm, preferably from about 0.7 to 10 nm, particularly preferably from about 0.7 to 5 nm, along at least one dimension. The term "void" is to be interpreted broadly. Such a void can be, for example, an approximately spherical void or a channel having a defined geometry, as is found, for example, in zeolite materials. However, the void can also be formed between two layers, for example in sheet silicates. However, the void has a comparatively small opening, so that the active metal precursor can diffuse into the void and be precipitated there in a controlled fashion. For this reason, the abovementioned diameter of from about 0.7 to about 20 nm essentially corresponds in the case of sheet silicates to the sheet spacing. In the case of spherical voids, the porous support has pores having an approximately spherical outline.
The size of the opening of the void can be determined by nitrogen adsorption measurements in accordance with the BJH method (DIN 66134).

- 6 -
The porous supports preferably have a pore volume of more than 0.09 cm3/g, particularly preferably more than 0.15 cm3/g. If zeolites are used as supports, the pore volume is preferably less than 1.5 cm3/g.
MOF systems ("metal organic framework") are also suitable as supports. These systems comprise metal atoms which are three-dimensionally linked via organic ligands to form a network and are suitable, for example, for hydrogen storage. These compounds have very high pore volumes of up to 10 cm3/g and very high specific surface areas of more than 1000 m2/g, particularly preferably more than 2000 m2/g.
The porous support has a high specific surface area of at least 500 m2/g, preferably at least 600 m2/g, more preferably more than 800 m2/g, particularly preferably more than 1000 m2/g. The specific surface area is determined by nitrogen adsorption measurement in accordance with the BET method (DIN 66131).
At least one active metal precursor comprising at least one active metal in a reducible form and a.t least one group bound via a ligator atom to the active metal is then applied to the porous support. The active metal atom is thus present in an oxidation state of greater than zero in the active metal precursor. For the present purposes, an active metal is a metal which in the finished catalyst displays a catalytic effect in respect of the reaction to be catalysed. In the case of a catalyst for the synthesis of methanol, this is, for example, copper which in the active form of the catalyst is present as metal. Correspondingly, an active metal precursor is a compound from which the active metal can be set free. In the process of the invention, compounds containing at least one atom of the active metal and at least one group bound via a ligator atom to the active metal atom are used as active metal precursors. The ligator atom is selected

- 7 -
from among oxygen, sulphur, nitrogen, phosphorus and carbon. The active metal preferably bears organic groups, i.e. groups which have at least one carbon atom in addition to the ligator atoms 0, S, N and P. These organic groups preferably have from 1 to 24 carbon atoms, in particular from 1 to 6 carbon atoms. The carbon framework can bear, in addition to the ligator atom, further heteroatoms or heteroatomic groups which can coordinate as Lewis bases to the active metal and thereby stabilize the active metal precursor. Suitable organic groups are, for example, alkoxides or amino-functionalized alkoxides.
The active metal precursor is reduced by means of a reductor to precipitate the active metal on the walls of the pores. For the purposes of the present invention, a reductor is an organometallic compound which can reduce the active metal precursor to precipitate the active metal on the porous support. The promoter metal is set free from the reductor and is precipitated as promoter, usually in the form of the oxide, to the support in preferably nanodisperse form. The reductor therefore comprises at least one promoter metal and at least one hydride group and/or an organic radical bound via a carbon atom to the promoter metal. Bonding can in this case be either via a s bond or a p bond.
The groups in the active metal precursor are preferably bound to the active metal via a ligator atom other than carbon, preferably via an oxygen atom or a nitrogen atom. However, if the groups on the active metal and on the promoter metal are both bound via a carbon atom to the metal atom, then the molecular weight of the groups of the reductor is preferably lower than the molecular weight of the groups of the active metal precursor. The groups bound in the reductor preferably have from 1 to 24, particularly preferably from 1 to 6, carbon atoms and may also have groups which are bound via a hetero-atom and can act as Lewis bases and thus stabilize the

- 8 -
reductor. The groups in the reductor are preferably-selected from among alkyl groups, alkenyl groups, aryl groups, a cyclopentadienyl radical and derivatives thereof and also a hydride group. For the purposes of the present invention, a promoter metal is the metal which forms the promoter in the finished catalyst. The promoter is generally present as oxide. In the case of a catalyst for the synthesis of methanol, zinc and optionally aluminium form the promoter metals.
Particular organometallic compounds can thus be advantageously used as active metal precursors or as reductors in the process of the invention.
For the present purposes, organometallic compounds are:
1. metal complexes in which direct metal-carbon bonds
are present;
2. metal complexes in which no metal-carbon bond is
present but (coordinated) ligands which are
organic in nature, i.e. belong to the family of
hydrocarbon compounds and derivatives thereof, are
present. The term "organometallic" thus makes a
distinction from purely inorganic metal complexes
which 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 support is not subject to any restrictions per se. The support can firstly be impregnated with the active metal precursor and the reductor can then be applied to precipitate the active metal on the support. However, it is also possible to apply the reductor to the support first and to apply the active metal precursor subsequently. It is also possible to apply the active metal precursor and the reductor alternately to the support a number of times. The active metal

- 9 -
precursor or the reductor is firstly physisorbed or chemisorbed on the surfaces of the porous support, in particular on the surfaces of the voids. The active metal is then set free Erom the active metal precursor and precipitated by addition of the other component.
In the process of the invention, use is made of specific support materials onto which the active metal and the promoter are precipitated. The support materials have a high porosity which can be set in the nanometre range and thus an extremely high specific surface area. The inventors conceive of a model in which the voids or pores act as dimensionally restricted reaction chambers for the reduction of the active metal precursor, so that undesirable particle growth during preparation of the catalyst does not occur. The void has a comparatively small opening, so that the active metal precursor can diffuse into the void and be precipitated there in a controlled fashion. For this reason, only a limited amount of the active metal precipitates in each void. The active metal after it has been set free is therefore distributed in nanodisperse form on the walls of these reaction chambers. The maximum diameter of the particles does not exceed the pore diameter, which, for example, is 2 nm when using an MCM-41, in at least one direction. In further process steps in which the catalyst is, for example, heated to relatively high temperatures, no exchange occurs between the various voids, so that growth of the catalytically active particles is suppressed and the nanodisperse distribution of the catalytically active sites is maintained. In addition, this has a favourable influence on the long-term stability of the catalysts under process conditions. The active metal precxarsors and the reductors are preferably adsorbed on the internal surface area of these support materials and thus come into direct chemical proximity in a very controllable fashion. This has a positive effect both on the efficiency of the

- 10 -
reduction process and on the dispersion of the active metal particles and the promoter components. This ensures, in a novel way, a close surface or interfacial contact of support, active metal particles and promoter components necessary for the catalytic properties.
If the catalytically active metal component comprises a plurality of metals or metal compounds, for example metal oxides, these are in intimate contact since the individual constituents are each present in nano-disperse form. The particular characteristic of the process of the invention is that, in contrast to other known impregnation processes, the active metal is deposited and chemically fixed by means of a chemical reaction between the active metal precursors and the reductors (reduction or cr bond metathesis or the like) in a restricted nanosize reaction chamber formed by the supports, i.e. in catalytically relevant close proximity.
In the air-stable storage form of the catalyst, the active metals are usually present in the form of an oxide. Exceptions are very noble active metals, e.g. Pt and Pd, etc. The oxides are formed as a result of oxidation by air after the preparation of the catalyst. However, it is also possible to oxidize only a proportion of the metal form by means of specific stabilizing measures in an established manner known from the prior art. Here, the active metal is passivated by a thin oxide layer. After being introduced into the reactor, the catalyst can then be converted back into its active form by means of a mild and simple rereduction. For this purpose, these oxide layers are reduced, for example, by means of hydrogen.
In particular with a view to regeneration of the catalyst, the quality of the catalytic activity of the system and its chemical composition and structural characteristics is not altered by repeated oxidation

- 11 -
and reduction cycles; i.e. appropriate regeneration of the catalyst to restore the original catalytic activity is possible in an advantageous manner.
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 abovementioned group, for example copper or zinc. However, it is also possible for the active metal to comprise a plurality of metals from the abovementioned group, for example two or three metals. The metals can be present in reduced form as pure metal or else as a metal compound, in particular as metal oxide. As mentioned above, the active metal is usually present in the transport form of the catalyst in at least partly oxidized form, so that the catalyst is also sufficiently stable in air.
In a preferred embodiment, the promoter metal is selected from the group consisting of Al, Zn, Sn, rare earth metals and alkali metals and alkaline earth metals. Suitable alkali metals and alkaline earth metals are, for example, Li, Na, K, Cs, Mg and Ba. Different metals are selected as active metal and promoter metal for the catalyst.
Specific metal-containing reducing agents, here referred to as reductors, are thus used in the process of the invention. These reductors set the active metals important for the catalytic properties free from the corresponding chemical precursors (active metal precursors) in which these metals are present in defined, bound form by means of a particularly efficient but at the same time very mild chemical reduction. Reductors used are organometallic compounds containing a metal which acts as promoter for the catalytically active active metal.

- 12 -
If a catalyst for the synthesis of methanol or a reformer for fuel cell technology is prepared by the process of the invention, the catalyst preferably comprises the system, Cu/Zn/Al. Here, the atomic ratios of Cu/Zn/Al are in typical ranges from 1:2:0.1 to 2:1:1. The copper can be introduced by means of a suitable active metal precursor, the zinc can be introduced via the reductor and the aluminium can be introduced via the porous support.
The active metal precursor is preferably a compound of
the formula MeXpLo, where Me is an active metal, X is
selected from the group consisting of alkoxides (OR*),
amides (NR2*) , b-diketonates (R* (=O) CHC(=O)R*) and their
nitrogen analogues, in particular b-ketoiminates
(R*(=O)CHC(=NR*)R*) and b-diiminates
(R*(=NR*)CHC(=NR*)R*), carboxylates (R*COO), oxalates (C2O4) , nitrates (NO3) and carbonates (CO3) , where R* is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, and the radicals R* can be identical or different, p is an integer corresponding to the valency of the promoter metal, o is an integer from 0 to the number of free coordination sites on the promoter metal atom and L is an organic Lewis, base ligand containing oxygen or nitrogen as ligator atom. L and X can here encompass only one type of the ligands or radicals mentioned. However, it is also possible to envisage combinations of the groups mentioned.
In one embodiment of the process of the invention, the reductor is a compound of the formula MRnLm, where M is a promoter metal, R is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, a cyclopentadienyl radical or derivatives thereof, or a hydride group, with the radicals R being

- 13 -
able to be identical or different, n is an integer corresponding to the valency of the metal, L is an organic Lewis base ligand containing oxygen or nitrogen as ligator atom and m is an integer from 0 to the number of free coordination sites on the active metal atom. In the case of the reductor too, only one type of radicals or ligands can be used for the radical R and the ligand L. However, it is likewise possible to combine various groups.
As ligands L, it is possible to use, for example, compounds of the formula OR'R' or NR'R'R'', where the radicals R' , R' ' and R' ' ' are each an alkyl group having from 1 to 6 carbon atoms, with it also being possible for two of these radicals together with the heteroatom to form a ring.
Particular preference is given to reductors of the formula MRnLm selected from among ZnR2Lm and AlR3Lm, where m = 0, 1 or 2 and R and L are as defined above.
In general, the active metal precursors applied to the porous support are selected so that they react with one another or with the abovementioned reductors as a result of complete or partial X/R exchange in the restricted reaction chambers of the supports to form species of the composition MeRx (x The abovementioned active metal precursors and reductors can be applied as solution to the porous support. The solvent and the active metal precursors or reductors are matched to one another so that no decomposition occurs in the solvent. After loading of the support with the active metal precursor, the

- 14 -
solvent together with excess active metal precursor is removed. To remove solvent residues, the laden porous support can, if appropriate, firstly be dried. The reductor, which is once again an organometallic compound, is subsequently applied to the porous support. The reductor reduces the active metal precursor applied initially, so that the catalytically active metal is precipitated and fixed on the porous support. However, this procedure can also be carried out in the reverse order, i.e. the porous support is firstly 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 vapour deposition (CVD). In this case, the active metal precursors or the reductors preferably have a vapour pressure of at least 0.1 mbar at 298 K. In a particularly preferred embodiment of the process of the invention, organometallic complexes are therefore used both as active metal precursors and as reductor.
Combinations of these methods are also possible. For example, the active metal precursor can be applied as a solution and the reductor can subsequently be applied by chemical vapour deposition. Likewise, it is also possible for the active metal precursor to be applied first by vapour deposition and the reductor subsequently to be applied as a solution.
The porous support can consist of any desired material. However, the support should have the above-described voids which have a relatively small opening having the dimensions indicated above. Thus, for example, the abovementioned MOF systems are suitable as porous support materials. Since the catalysts are usually employed at elevated temperature, it is preferred that the support is made up of an inorganic material. Examples of suitable inorganic materials are zeolites,

- 15 -
PMS, sheet silicates such as bentonites, clays or pillard clays, hydrotalcites and heteropolyacids, e.g. of molybdenum and tungsten.
However, particular preference is given to using periodic mesoporous silicate materials (PMS) since these have very high specific surface areas and the pore structure can be set precisely in them. Examples are MCM-41, MCM-48 and SBA-15.
Among the zeolites, preference is given to those which have a large pore radius. Zeolites having a pore radius of > 0.7 ran are, for example, mordenite, VPI-5 or cloverites.
The preparation of the catalyst is carried out under extremely mild conditions. Thus, a temperature of 200°C is preferably not exceeded during the preparation of the catalyst. The active metal is as a result deposited in finely divided form, with the diameter of the particles of active metal produced generally being in the range from about 0.5 to 10 nm, preferably from 0.5 to 5 nm. The promoter, too, is deposited in finely divided form, so that a very large contact area between active metal and promoter can be achieved. This leads to catalysts having a very high activity.
The invention therefore also provides a catalyst, in particular for the synthesis of methanol, comprising a porous support and at least one active metal precipitated on the porous support and at least one promoter precipitated on the porous support, wherein the porous support has a specific BET surface area of at least 500 m2/g, the active metal has a specific metallic surface area of at least 25 m2active metal/gactive metai and the promoter has a specific surface area of at least 100 m2/gpromoter, preferably at least 500 m2/gprOmoter• The specific surface area of the active metal can be determined by gas adsorption/desorption methods or by

- 16 -
reactive gas adsorption/desorption methods. An example of such a method is N20 reactive frontal chromatography for determining the specific surface area of copper. Analogous methods can be employed for other active metals. They are generally based on the occupation of the metal surface by a molecule having a known space requirement, with the amount of adsorbed molecules being determined. The specific surface area of the promoter can be estimated by determination of the degree of aggregation via X-ray absorption studies and by BET surface area determination on the laden support. The content of promoter component can be determined by means of elemental analysis (e.g. atomic absorption spectroscopy or , energy-dispersive X-ray absorption spectroscopy).
A distinguishing feature of the catalysts prepared by the process of the invention compared to the catalysts prepared by alternative methods, in particular by coprecipitation/calcination, is the extremely low, even vanishing degree of aggregation of the promoter component (which can be determined by means of X-ray absorption studies) combined with a high BET surface area of the active catalyst of preferably far above 500 m2/g. It is usually not possible to determine any measurable degree of coordination. When the catalysts are examined by X-ray diffraction methods, no reflections for the promoter are observed in this case. When the catalyst is examined by X-ray absorption spectroscopy, only very low aggregation states are observed. This means that the atoms which are two or three atoms removed from a promoter atom are normally not promoter atoms. In general, the first other promoter atom is at least two or three atoms removed from a promoter atom. In other words, the promoter is preferably in the form of an at most two- or three-shell promoter.
The degree of aggregation of the active metal component

- 17 -
is also typically very low, which is reflected, in particular, in the metal particles, e.g. copper, being so homogeneously distributed on the (internal) surface area of the support and having such small dimensions that they cannot be detected and characterized as well-formed particles by transmission electron microscopic methods, while a small but measurable degree of aggregation of the majority of the particles can be characterized as described by X-ray absorption measurements. The active metal preferably has a mean coordination number of not more than 10 in the catalyst of the invention. The coordination number is preferably less than 10, particularly preferably in the range from 4 to 7. A 'coordination number of about 6 is often 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, e.g. for transport from the place where it is prepared to the synthesis reactor.
The maximum crystallite size of the active metal or of the promoter is in each case limited in one dimension by the maximum pore diameter.
The catalyst of the invention comprises a porous support which preferably has voids open on at least one side. The opening of these voids has a diameter of from about 0.7 to about 20 nm, preferably from about 0.7 to 10 nm, particularly preferably from about 0.7 to 5 nm, along at least one dimension. Furthermore, the porous support has a high specific BET surface area of at least 500 m2/g, preferably at least about 600 m2/g, particularly preferably at least about 800 m2/g. These high specific surface areas are also measured on the finished catalyst. Although the specific surface area is reduced by application of the active metal and the promoter, the finished catalyst nevertheless has a BET surface area of at least 500 m2/g, preferably at least about 600 m2/g, particularly preferably at least about

- 18 -
800 m2/g, which is very high compared to conventional catalysts. The porous support is laden with at least one catalytically active metal component which is present in finely divided form. The loading is at least about 2.5 m2active metal g-1catalyst, preferably at least about 3 m2active metal g-1ataiyst. particularly preferably about 5 m2active metal g-1cataiyst• However, an even higher loading can be achieved. This can be in the range from
> 10 m2active metal/g-1 Catalyst to more than 20 inactive metal/
g-1catalyst. In other words, the loading with the active
metal is at least about 25 m2active metai g-1active metal,
preferably at least about 35 m2actlve metai g-1active metai,
particularly preferably at least about 50 m2active
metai g-1Active metal. In particularly preferred cases, the
loading is accordingly more than
100 m2active metai g-1active metai/ in particularly preferred
Cases more than 200 m2active metal g-1active metal-
The loading of the catalyst with the active metal is preferably in the range from about 0.05 to 0.50 gactive metai g-1cataiyst, preferably from about 0.1 to 0.45 gactive metai g-1cataiyst, particularly preferably from about 0.1 to 0.3 0 gactive metai g-1Catalyst/ and the loading with the promoter is preferably in the range from about 0.01 to 0.3 gPromoter g-1Catalyst, preferably from about 0.05 to 0.2 gPromoter g-1cataiyst, particularly preferably from about 0.05 to 0.15 gpromoter g-1catalyst. The values and ranges indicated are in each case based on the metal or the promoter metal. The ratio of active metal/promoter metal is preferably in the range from about 10:1 to 1:5, more preferably from about 5:1 to 1:2, in particular from about 5:1 to 1:1. Preference is given to introducing a very large amount of active metal and very little promoter in the preparation of the catalyst.
The preferred supports and active metals and promoters have been described above in connection with the process of the invention.

- 19 -
The catalyst obtainable by the process of the invention brings a series of advantages which are illustrated below for, by way of example, an embodiment of the catalyst of the invention as catalyst for the synthesis of methanol.
The catalyst of the invention is distinguished from the known Cu/Zn/Al catalysts for the synthesis of methanol by the following criteria:
(1) The dispersion of the Cu component (or the active
metal) is higher, namely at least 25 m2cu g-1cu,
i.e. the catalyst of the invention is more active
at the same proportion by mass of catalytically
active Cu component or a lower proportion by mass
of copper (active metal) is sufficient to achieve
the same activity in the case of the catalyst of
the invention compared to known catalysts.
Analytical characterization of the catalyst by
means of EXAFS (extended X-ray absorption fine
structure spectroscopy) and XRD (X-ray
diffraction) indicates that the majority of the Cu
particles have a dimension close to or below 1 nm,
implying typical aggregates of 10-20 Cu atoms, and
the minority of Cu particles has dimensions up to
the channel or pore width of the PMS support
material.
(2) In contrast to known Cu/ZnO/Al2O3 catalysts, the
ZnO component and the aluminium oxide component
(promoter) is not aggregated in an ordered manner.
Rather, they form, according to EXAFS data, a thin
coating on the interior walls or surfaces of the
support material. In this way, the specific
surface area of the ZnO component reaches values
in the order of the specific surface area of the
support material (> 500 m2/g) and far exceeds the
specific BET surface areas of previously known

- 20 -
high-surface-area ZnO support materials, viz. up to about 150 m2 g-1. [M. Kurtz, N. Bauer, C. Buscher, H. Wilmer, 0. Hinrichsen, R. Becker, S. Rabe, K. Merz, M. Driess, R.A. Fischer, M. Muhler, "New synthetic routes to more active Cu/ZnO catalysts for methanol synthesis", Catalysis Letters 2004, 92, 49; C.R. Lee, H.W. Lee, J.S. Song, W.W. 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, S.E. Pratsinis, "Homogeneous ZnO nanoparticles by, flame spray pyrolysis", Journal of Nanoparticle Research 2002, 4, 337.]. -In contrast to known Cu/ZnO/Al2O3 catalysts, the catalyst of the invention contains no nanocrystalline ZnO or A12O3 components which can be detected by TEM or XRD methods.
These criteria apply not only to a catalyst for the
synthesis of methanol using the system Cu/ZnO/Al2O3, but
can be carried over to all catalysts obtainable by the
process of the invention.
The catalysts of the invention have a very high activity based on the proportion by mass of the cata-lytically active metal components. They are therefore particularly suitable for use as catalysts for the synthesis of methanol or as reformers in fuel cell technology.
In summary, it can be stated that, taking into account preferred embodiments the advantages of the invention are:
1. the mild process conditions (in particular relatively low preparation temperatures, in particular temperatures of less than 200°C) which suppresses

- 21 -
undesirable particle growth processes which were unavoidable according to the prior art;
2. the combination of active metal precursors with
metal-containing reducing agents (reductors) which
make it possible to achieve an extraordinarily-
high dispersion of active metal components (active
metals) and promoter components together with a
high surface or interfacial contact of metal/metal
oxide-promoter. The latter leads to an improvement
in the specific activity and selectivity of the
catalysts;
3. the opportunity provided by the novel process of
controlling the composition of the catalyst system
while maintaining an unchanged high dispersion by
means of permutation and/or cyclic repetition of
the individual loading or reactions steps;
4. the elimination of problematical salt and/or
stabilizer burdens, as result, for example, from
impregnation techniques based on colloid-chemical
processes according to the prior art;
5. the use of porous support materials as dimen-
sionally restricted reaction chambers for the
metathetic surface reaction between various
precursors which is necessary for success. The
dimensionally restricted reaction chambers
(geometrically defined by the pore characteristics of the porous support systems) suppress unwanted particle growth due to their intrinsic geometry. In particular, this is aided by the larger optimized ratio of surface area to volume of porous supports compared to supports having a relatively low porosity. The support properties mentioned thus counter segregation of the components. This ensures a high dispersion of the catalytically active components and a high

- 22 -specific loading of the support.
The invention is illustrated below with the aid of examples with reference to the accompanying figures. In the figures:
Fig. 1 shows a highly schematic presentation of the mechanism by which the deposition of the active metal and the promoter metal proceeds in the process of the invention;
Fig. 2 shows X-ray powder diffraction patterns of the samples:
a) the precursor Cu/ [Zn(0CHMeCH2NMe2)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.
As a guide, the (111) , (200) and (220) reflection planes of polycrystalline copper are marked on the abscissa.
Fig. 3 shows small-angle powder diffraction patterns of a) empty, calcined MCM-41 and b) Cu/ZnO/MCM-41. The characteristic drop in intensity of b) compared to a) is an indication of the loading of the pores. In the transmission electron micrograph also obtained on a Cu/ZnO/MCM-41 sample, the intact pore structure can clearly be seen; however, copper particles or zinc oxide particles cannot be identified because of their small size. The presence of copper and zinc is evidenced by the associated EDX spectrum (element dispersive X-ray fluorescence analysis).
Fig. 4 shows a) CuK XANES and b) Cult EXAFS spectra (absolute value of the Fourier transforms) of

- 23 -
Cu/ZnO/MCM-41 and reference substances, c) analysis of the spectrum of Cu/ZnO/MCM-41; modelling parameters: nearest neighbour Cu; spacing (R) = 2.512 ± 0.002 A, coordination number (N) =5.8+0.3, Debye-Waller factor (a2) = (9.6 + 0.4) *10-3 A2. Nearest neighbour 0: R = 1.86 ± 0.04 A, N = 0.3 ± 0.1, O-2 (7 ± 0.11) *10-3 A2.
Fig. 5 shows the reaction of [Cu(OCHMeCH2NMe2)2] with diethylzinc in the nanotubes of the MCM-41 support material.
Fig. 1 shows a schematic presentation of the mechanism according to which the deposition of active metal and promoter occurs in the process of the invention. It goes without saying that this is only a model concept and in no way restricts the scope of the invention.
Fig. la shows a section through a porous support 1 in which there is a pore 2 which is open to the outside of the support 1. The support 1 can, for example, be a zeolite. An active metal precursor 3 and a reductor 4 have diffused into the pore 2. Loading can be effected by the porous support 1 firstly being loaded with the active metal precursor 3 and subsequently with the reductor 4. However, it is also possible to load the porous support 1 ' firstly with the reductor 4 and subsequently with the active metal precursor 3. If the mixture of active metal precursor 3 and reductor 4 is sufficiently stable at the loading temperature, loading can also be carried out simultaneously. The active metal precursor 3 comprises an active metal AM to which groups L are bound. In Fig. 1, the active metal AM bears two groups L in the interests of clarity. However, it is also possible for more than two groups L to be present in the active metal precursor 3. Apart from the groups L, the active metal AM can additionally bear further ligands which stabilize the active metal

- 24 -
precursor, e.g. by coordinate bonding. The groups L are bound via a ligator atom (not shown) to the active metal AM. The ligator atom is selected from among oxygen, sulphur, nitrogen and carbon. The reductor 4 comprises a promoter metal PM to which organic groups R are bound via a carbon atom. In Fig. 1, the reductor has only two groups R in the interests or clarity. However, it is also possible for more than two groups R to be bound to the promoter metal PM or for further groups in addition to the groups R to be bound to the promoter metal PM. The letters x and y correspond to the molar ratio of active metal promoter 3 and reductor 4 employed. As central step in the deposition, ligand exchange between active metal AM and promoter metal PM then occurs. This is shown in Fig. lb. This results in a reactive intermediate 5 which comprises the active metal AM and the, groups R. In addition, the promoter compound 6 comprising the promoter metal PM •and the groups L is obtained. The reactive intermediate 5 subsequently decomposes. This decomposition process is, for example, aided or induced by heating. The active metal present in the reactive intermediate 5 is reduced to the active metal AM and deposits in nanodisperse form as crystallites 7 on the walls of the pores 2 (Fig. lc). At the same time, the compound R-R is formed from the groups R, e.g. in a metathesis reaction. This compound can be taken off as offgas. The promoter compound 6 is oxidized so that the promoter metal is likewise precipitated as promoter PR, for example in the form of an oxide, 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 liberated in this reaction and can likewise be taken off with the offgas.
Example 1: Cu/ZnO/MCM-41
Freshly synthesized, calcined and dry MCM-41 (350 mg) and a portion of about 1.0 g of [Cu(OCHMeCH2NMe2) 2] are

- 25 -
placed in separate glass boats in a Schlenk tube and heated at 340 K in a static vacuum (0.1 Pa) for 2 hours. A sample of 200 mg of the blue-coloured product material and about 0.5 g of diethylzinc are positioned next to one another as above and left at room temperature in a static vacuum (0.1 Pa) for 2 hours. Variation of the vapour deposition time, temperature, molar amounts and PMS material leads to different loadings (Table 1). To produce the ZnO, the Cu/ [Zn(OCHMeCH2NMe2)2] /MCM-41 sample is taken out under protective gas and subsequently heated at 623 K in a dynamic vacuum (0.1 Pa) (2 h) . The procedure is repeated using other PMS materials, e.g. MCM-4 8.
Example 2: Cu/MCM-41 and ZnO/MCM-41
Heating of [Cu(OCHMeCH2NMe2) 2] /MCM-41 (see above) at 523 K in a dynamic vacuum (0.1 Pa) (20 min) gives Cu/MCM-41. ZnO/MCM-41 is obtained in an analogous fashion using [Zn(OCHMeCH2NMe2) 2] as ZnO precursor by heating the intermediate [Zn(OCHMeCH2NMe2) 2]/MCM-41 at 623 K (0.1 Pa, 2 h) . [Zn(OCHMeCH2NMe2) 2] /MCM-41 was obtained by impregnating MCM-41 with a solution of [Zn(OCHMeCH2NMe2)2] (1.0 g) in pentane (40 ml) and separating off the solid and washing it a number of times. As an alternative, ZnO/PMS can be obtained by treatment of the supports with diethylzinc vapour and subsequent calcination.
Characterization of the samples
The X-ray powder diffraction patterns (PXRD) were recorded by means of a D8-Advance Bruker AXS diffractometer using Cu Ka radiation {X = 1.5418 A) in 0-20 geometry and using a position-sensitive detector (capillary technique, protective gas). All diffraction patterns were fitted by means of Profile Plus 2.0.1 software using a pseudo-Voigt function. TEM examinations were carried out using a Hitachi H-8100 instru-

- 26 -
ment at 200 kV using a tungsten filament (preparation with exclusion of air, Gold-Grids Piano, vacuum transfer holder). X-ray absorption spectra (XAS) were recorded on a Hasylab (DESY, Hamburg) at station XI in the transmission mode using an Si (311) double crystal monochromator (software VIPER). Nitrogen adsorption measurements were carried out using a Quantachrome Autosorb 1 MP apparatus. The pore diameter was calculated by the Barrett-Joyner-Halenda (BJH) method. The specific surface area (SBET) of the empty, calcined MCM-41 and the CuOx/MCM-41 was determined by means of the data of the linear part of the BET graph (p/po = 0.05-0.35) .

27

- 28 -
[a] The copper surface area was determined by means of
N2O-RFC. After a pretreatment with a dilute H2
atmosphere (2% by volume) , N20 (1% by volume of N20
in He, 3 00 K) was passed over the catalyst and the
copper surface area was calculated from the, amount
of nitrogen liberated (density of Cu surface
atoms: 1.47'1019 m-2) . The activity in the syn
thesis of methanol was examined under atmospheric
pressure at a temperature of 493 K. A mixture of
72% of H2, 10% of CO, 14% of C02 and 14% of He was
used as synthesis gas. The data reported were
obtained after a reaction time of 2 hours. Due to
the low conversion at atmospheric pressure, no
products other than methanol were able to be
detected.
[b] Catalysis-specific data of catalysts which had
been prepared by coprecipitation and whose perfor
mance in the synthesis of MeOH was determined
under conditions . analogous to those for the
Cu/ZnO/PMS samples. The product rates from the
regression analysis (production rate as a function
of the Cu surface area of the catalysts having
different metal concentrations) were interpolated
(Cu/ZnO) or extrapolated (Cu/ZnO/Al2O3) to the Cu surface areas found in the Cu/ZnO/PMS. The data for the comparative samples come from: T. Genger, thesis, Ruhr-Universitat Bochum, 2000.
[c] Not detectable.
Further characterization of the samples: if a portion (350 mg) of pure, freshly calcined MCM-41 (0 BJH = 2.7 nm, SBET = 712 m2 g"1) is exposed to the vapour of an adjacent portion (1.0 g) of the blue-violet Cu precursor [Cu(OCHMeCH2NMe2)2] (1) at 340 K in a static vacuum (0.1 Pa) in a tightly sealed Schlenk tube, the originally colourless silicate material becomes light blue. The Cu precursor

- 29 -
[Cu(OCHMeCH2NMe2)2] remains intact, as comparison of the IR data of the laden MCM-41 with pure [Cu(OCHMeCH2NMe2)2] shows. The adsorption is strong, since [Cu(OCHMeCH2NMe2) 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 of free silanol groups which is otherwise observed at 3745 cm"1 indicates an interaction of the pore walls with [Cu(OCHMeCH2NMe2)2] , perhaps via hydrogen bonds. If the [Cu(OCHMeCH2NMe2)2]-laden support is then treated with diethylzinc vapour in a second step by placing the two samples next to one another in a Schlenk tube and evacuating and sealing the latter (0.5 g of ZnEt2, 300 K, 0.1 Pa), a colour change from light blue to reddish brown gradually occurs. In the X-ray diffraction pattern of a sample of the material prepared under inert gas in a capillary, a weak, very broad structure appears at 2 8 = 44.70° and can be assigned to the reflection of the [111] lattice plane of small Cu particles {Fig. 2 and 3) . Solid-state NMR spectroscopy reveals [Zn(OCHMeCH2NMe2) 2] (2) as by-product. This reaction occurring in the nanotubes of the PMS corresponds to the quantitative reaction as shown in Fig. 5 which can be carried out on the preparation gram scale in solution, with Cu metal precipitating (XRD), the zinc alkoxide [Zn(OCHMeCH2NMe2)2] remaining in solution (NMR identification) and butane being given off as gas (GC-MS). It is worth noting that when the reactivity of the zinc alkyl used is decreased, e.g. by use of very bulky alkyl radicals such as C(SiMe3)3, the alkyl/alkoxide metathesis does not occur and bimetallic alkylzinc/copper alkoxide complexes were isolated and characterized structurally. The solid-state pyrolysis of these complexes has hitherto led only to micro-crystalline, catalytically inactive Cu/ZnO materials.
Gentle heating of the resulting samples
Cu/ [Zn(OCHMeCH2NMe2)2] /PMS at 623 K in a dynamic vacuum
(0.1 Pa, 2 h) gives predominantly CHx-free materials

- 30 -
which as before display a very broad Cu(lll) reflection. However, X-ray diffraction does not indicate the presence of ZnO nanocrystallites {Fig. 2). The specific Cu surface areas of the Cu/ZnO/PMS samples were determined as 5-6 m2cu;g-1 cat in each case before and after the catalysis test (Table 1) . The methanol productivities of from 19 to 130 umol'g-1cat'h-1 are in the range of the binary Cu/ZnO catalysts prepared by coprecipitation/calcination or in the case of the MCM-48 sample, are surprisingly significantly superior to these. The three-dimensional pore structure of the MCM-48 support allows efficient diffusion in comparison with MCM-41. The reduction (H2) of completely oxidized samples which have been stored in air (disappearance of the Cu(lll) reflection) restored the original activity and Cu surface area. The comparative samples Cu/MCM-41 (10-12% by weight; 5-7 m2cu'g-1cat) and ZnO/MCM-41, which had been obtained by heating of [M(OCHMeCH2NMe2)2] /MCM-41 (M = Zn, Cu) or treatment of MCM-41 with diethylzinc vapour and calcination, proved to be inactive. Extraordinarily high values for the Cu surface areas of up to 50-60 m2cu'g-1cat were measured on freshly prepared Cu/ZnO/PMS samples during the first oxidation/reduction cycles (N2O/H2) , but these dropped to the characteristic level of 5-6 m2cu'g-1cat during further cycles. This discrepancy is obviously not due to sintering of the Cu particles but is caused by the O-Zn-C2HS groups which are bound to the pore wall of the PMS and are present in excess on the basis of scheme 1, and are likewise oxidized by N20.
The EXAFS spectra (Fig. 4) of Cu/ZnO/MCM-41 confirm the presence of very small Cu aggregates. The coordination number of 5.8 and the rather high Debye-Waller factor found for just the first metal shell indicate a high level of defects. On the assumption of spherical, monodisperse particles, a diameter of 0.7 nm can be calculated, corresponding to a cluster of 13 Cu atoms. Even if an underestimation of the particle size because

- 31 -
of the correlation of coordination number, - and Debye-Waller factor is assumed, the virtually complete absence of higher coordination shells shows that the characteristic dimension of the particles is certainly less than the pore radius of 2-3 ran. The Cu aggregates are present in a particle size distribution of which X-ray diffraction records only the coarse fraction
(about 2 nm) . The Cu-Cu contact of 2.50 A6 calculated
from the Cu(lll) reflection position of 2 9 = 44.35°
corresponds to the value of 2.51 A6 obtained from the
EXAFS data and is shortened compared to the Cu-Cu
spacing of the bulk phase of 2.56 A6 (effect of small particles). The reason for the Cu-0 coordination found is uncertain. In view of the small mean particle size, it is obvious that oxygen atoms of the pore wall can be recorded in the EXAFS spectrum, as has been described in the literature. The presence of a small proportion of the copper as Cu+ can therefore not be. ruled out. Comparison of the ZnK spectra with test substances (not shown) indicates agreement neither with ZnO nor with Zn. The first 0 sphere has an intensity which is too low and the second sphere (Zn) is virtually completely absent. The fit with Si and Zn separated by one other atom is good, which, in agreement with the solid-state NMR data and the IR data (absence of free silanol groups) , indicates coating of the pore wall with ZnO. The degree of aggregation of the ZnO component is thus vanishing. An analogous situation is found for ZnO/PMS materials which have been obtained by aqueous impregnation/calcination techniques. Clear indications of CuZnOx 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/Al2O3 (I), Cu/ZnO (II) and the ternary system Cu/ZnO/Al2O3 (III) . In the case of materials prepared by classical methods, the activity at a different level in each case, increasing

- 32 -
from I to III, correlates linearly with the specific Cu surface area. Our activity found for the sample Cu/ZnO/MCM-48 of 13 0 umol -g-1 cat 'h-1 is thus far above the value to be expected for binary Cu/ZnO catalysts having the same specific surface area and is in the range III. Interactions of the Cu particles with the silicate matrix can hardly be responsible for this, since Cu/PMS comparative samples were inactive and the pore walls of the active Cu/ZnO/PMS samples are, as indicated above, obviously coated with ZnO. Rather, the simultaneously high dispersion of Cu and ZnO components appears to be a new, positive effect. An aggregated, (nano)crystalline ZnO phase as is inevitably obtained using coprecipitation/calcination procedures is quite clearly not necessary for the synergistic effect. This is supported by the Cu/Zn alloy formation cited at the outset and also our further observations, namely that a Cu/Al2O3 catalyst prepared by classical methods experienced an activity jump to above the region of the ternary systems as a result of even a short treatment with diethylzinc vapour. In addition, the use of a specific, nanodisperse ZnO support material having a particularly high surface area or level of defects (153 m2-g-1), which was obtained by solid-state pyrolysis of [ (Me3SiO) ZnMe] 4, led to an extraordinarily active, binary Cu/ZnO catalyst.
The advantageous aspects of the process of the invention for the loading of PMS support materials, in particular for the preparation of Cu/ZnO catalysts are: not only the variation of dimensions and structure of the pores (e.g. MCM-41 vs. MCM-48 or other appropriate support materials) but also exploitation of the chemistry of the precursor substances allows molecular control over the active metal/promoter contact, for example the Cu/ZnO contact. The results indicate that nothing fundamental should stand in the way of the process of the invention surprisingly giving a simultaneous maximization of the specific active metal

- 33 -
surface areas (e.g. Cu surface area and the Cu/ZnO interfacial contact or the ZnO dispersion) and the interfacial contact between active metal/metal oxide or promoter so as to increase the catalyst activity far above that which has been possible hitherto.

- 34 -Claims
1. Process for preparing a catalyst which comprises a
porous support, at least one active metal and at
least one promoter and is suitable, in particular,
for the synthesis of methanol, wherein a porous
support having a specific surface area of at least
500 m2/g is made available, at least one active
metal precursor comprising at least one active
metal in a reducible form and at least one group
bound via a ligator atom preferably selected from
among oxygen, sulphur, nitrogen, phosphorus and
carbon to the active metal atom is applied to the
porous support, the active metal precursor is
reduced by means of a reductor comprising at least
one promoter metal and at least one hydride group
and/or an organic group bound via a carbon atom to
the promoter atom, and the reductor is converted
into the promoter.
2. Process according to Claim 1, wherein the at least
one organic group on the reductor is selected from
among alkyl groups, alkenyl groups, aryl groups, a
cyclopentadienyl radical and derivatives thereof
and a hydride group.

3. Process 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. Process according to any of the preceding claims,
wherein the promoter metal is selected from the
group consisting of Al, Zn, Sn, rare earth metals
and alkali metals and alkaline earth metals.
5. Process according to any of the preceding claims,
wherein the active metal precursor is a compound
of the formula MeXpLo, where Me is an active metal

- 35 -
precursor, X is selected from the group consisting of alkoxides (OR*), amides (NR2*) , b-diketonates (R*(=O)CHC(=O)R*) and their nitrogen analogues, in particular b-ketoiminates (R*(=0)CHC(=NR*)R*) and b-diiminates (R*(=NR*)CHC(=NR*)R*), carboxylates (R*COO) , oxalates (C2O4) , nitrates (N03) and carbonates (C03) , where R* is an alkyl radical having from 1 to 6 carbon atoms, an alkenyl radical having from 2 to 6 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, and the radicals R* can be identical or different, p is an integer corresponding to the valency of the promoter metal, o is an integer from 0 to the number of free coordination sites on the promoter metal atom and L is an organic Lewis base ligand containing oxygen or nitrogen as ligator atom.
6. Process according to any of the preceding claims,
wherein the reductor is a compound of the formula
MRnLm, where M is a promoter metal, R is an alkyl
radical having from 1 to 6 carbon atoms, an
alkenyl radical having from 2 to 6" carbon atoms,
an aryl radical having from 6 to 18 carbon atoms,
a cyclopentadienyl radical or derivatives thereof,
or a hydride group, with the radicals R being able
to be identical or different, n is an integer
corresponding to the valency of the metal, L is an
organic Lewis base ligand containing oxygen or
nitrogen as ligator atom and m is an integer from
0 to the number of free coordination sites on the
active metal atom.
7. Process according to any of the preceding claims,
wherein the active metal is copper and the
promoter metal is zinc and aluminium.
8. Process according to any of the preceding claims,
wherein the active metal promoter and/or the
reductor are/is applied to the porous support by

- 36 -vapour deposition.
9. Process according to any of the preceding claims,
wherein the porous support is selected from the
group consisting of porous silicate minerals,
zeolites, sheet silicates, clays, pillard clays,
hydrotalcites and heteropolyacids of molybdenum
and of tungsten.
10. Process according to any of the preceding claims,
wherein the support is selected from the group of
supports consisting of mordenite, MCM-41, MCM-48,
SBA-15, VPI-5 and cloverites.
11. Process according to any of the preceding claims,
wherein a maximum temperature of 200°C is not
exceeded during the preparation of the catalyst.
12. Catalyst, in particular for the synthesis of
methanol, comprising a porous support and at least
one active metal precipitated on the support and
at least one promoter precipitated on the support,
wherein the porous support has a specific surface
area of at least 500 m2/g, the active metal has a
specific surface area of at least 25 m2active
metal/gactive metal and the promoter has a specific
surface area of at least 100 m2/gprOmoter.
13. Catalyst according to Claim 12, wherein the active
metal has a mean coordination number of not more
than 10.
14. Use of a catalyst according to Claim 11 for the
synthesis of methanol or as reformer for fuel cell
technology.

Documents:

01555-kolnp-2006 assignment-1.1.pdf

01555-kolnp-2006 correspondence others-1.1.pdf

01555-kolnp-2006-abstract.pdf

01555-kolnp-2006-asignment.pdf

01555-kolnp-2006-claims.pdf

01555-kolnp-2006-correspondence other.pdf

01555-kolnp-2006-description (complete).pdf

01555-kolnp-2006-drawings.pdf

01555-kolnp-2006-form-1.pdf

01555-kolnp-2006-form-3.pdf

01555-kolnp-2006-form-5.pdf

01555-kolnp-2006-international publication.pdf

01555-kolnp-2006-international search authority report.pdf

01555-kolnp-2006-pct form.pdf

1555-KOLNP-2006-ABSTRACT 1.1.pdf

1555-KOLNP-2006-CANCELLED PAGES.pdf

1555-KOLNP-2006-CLAIMS 1.1.pdf

1555-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1555-KOLNP-2006-DRAWINGS 1.1.pdf

1555-KOLNP-2006-FORM 1.1.1.pdf

1555-kolnp-2006-form 18.pdf

1555-KOLNP-2006-FORM 2.pdf

1555-KOLNP-2006-OTHERS.pdf

1555-KOLNP-2006-PETITION UNDER RULE 137.pdf

1555-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

1555-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

« Previous Patent

Next Patent »

Patent Number

241164

Indian Patent Application Number

1555/KOLNP/2006

PG Journal Number

26/2010

Publication Date

25-Jun-2010

Grant Date

22-Jun-2010

Date of Filing

06-Jun-2006

Name of Patentee

SUD-CHEMIE AG

Applicant Address

LENBACHPLATZ 6, 80333 MUNCHEN

Inventors:

#	Inventor's Name	Inventor's Address
1	FISCHER RICHARD	VOGEL WEIDSTR. 2A, 83043 BAD AIBLING
2	BECKER RALF	MARTIN-LUTHER-STR. 10, 01099 DRESDEN,
3	HINRICHSEN KAI-OLAF	SCHATTBACHSTR. 3, 44801 BOCHUM,
4	MUHLER MARTIN	HAARHOLZER STR. 35A, 44797 BOCHUM,
5	FISCHER ROLAND	IM OSTHOLZ 103, 44879 BOCHUM

PCT International Classification Number

B01J 35/10

PCT International Application Number

PCT/EP2005/002429

PCT International Filing date

2005-03-08

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2004 011 335.1	2004-03-09	Germany