WO2003082465A1

WO2003082465A1 - Method of preparation of calcined supported catalysts using metallosilsesquioxanes

Info

Publication number: WO2003082465A1
Application number: PCT/NL2002/000219
Authority: WO
Inventors: Rutger Van Santen; Hendrikus Abbenhuis; Nicolai Maxim; Wendy Teunissen; Rudolf Alfred Overbeek; Anton John Nagy
Original assignee: Avantium International BV
Current assignee: Avantium International BV
Priority date: 2002-04-03
Filing date: 2002-04-03
Publication date: 2003-10-09
Anticipated expiration: 2004-10-03
Also published as: AU2002249694A1

Abstract

Described is a method for the preparation of a catalyst comprising a metal compound, supported on a carrier material comprising the steps of a) treating of the carrier material with at least a metallasilsesquioxane, and b) calcining the treated carrier material, as well as a catalyst obtainable by the said method.

Description

METHOD OP PREPARATION OF CALCINED SUPPORTED CATALYSTS USING

METALLOSILSESQUIOXANES

The invention relates to novel catalysts comprising a metal compound, supported on a carrier, to a method for the preparation thereof and to the use of such a catalyst.

Methods for the preparation of such catalysts, supported on a carrier material are known in the art. The said catalysts are produced by impregnation of porous carrier materials, such as silica with a solution of a metal salt. The impregnated carrier is subsequently calcined, resulting in a carrier, having a metal oxide on the surface thereof. Such a metallic oxide catalyst can be used as such; optionally, however, said catalyst can be subjected to a reduction step, resulting in a catalyst, wherein the metal compound has a reduced valency as compared with the valency thereof as presend in the metallic oxide obtained after calcination. By such a reduction step, metallic catalysts can be produced, comprising e.g. neutral metallic particles on the carrier.

Metallic oxide and metallic catalysts are used for numerous industrial processes, such as propylene oxidation to acrolein (Bi-Mo mixed oxide catalyst) , methanol oxi-dehydrogenation to formaldehyde

(Fe-Mo-based mixed oxide catalyst or metallic silver) , butane oxidation to nαaleic anhydride (Vn-based catalyst) , styrene synthesis

(potassium promoted iron oxide catalyst) , Fischer-Tropsch synthesis

(A1₂0₃ supported metallic Co or massive iron oxide catalyst) .

Further, oxidation of propane, butane, butylene, CO, cyclohexane, partial oxidation of methanol and the reduction of nitrogen oxide can be mentioned.

It has been found however, that the particle size of the metallic compound, such as metallic oxide and/or neutral metallic particles on the carrier can be relatively large i.e. over 50 nm, resulting in a sub-optimal distribution of the metallic compounds on the surface of the carrier and hence imparting the accessibility of the metallic compound for the envisaged substrates, therewith impairing the activity of such catalysts. A further problem is that when preparing a solution of one or more catalyst precursors, most commonly in the form of a salt, to be impregnated on the carrier, the desired valence states of these precursor metals may be difficult to achieve. Different metals may have valence states that are unstable in a given solution and these metals may be oxidized and/or reduced according to the prevalent solution conditions. Yet another problem that can be encountered when aiming to prepare mixed metal or mixed metal oxide catalysts is that particular metal salts dissolve more readily in acidic solutions than in basic solutions, and vice versa. Closely related to this problem is that some metals require special additives to dissolve them in sufficient quantities. However, these additives may limit the dissolution of other metal salts. Examples are ammonia to dissolve copper carbonate, and citric acid to dissolve vanadium oxide (in the form of vanadyl, VO⁺) . Yet another problem is that after impregnation of a mixed metals precursor solution on a carrier, the metals become separated upon drying and calcination, each metal being deposited as its own metal oxide on the carrier surface instead of being deposited as a mixed metal oxide .

Thus, metal and metal oxide catalysts derived from such metal ions, supported on a carrier, are very difficult to produce by the above described impregnation and calcination method of the art using a solution of a metal salt.

The present invention provides a novel method for the preparation of a catalyst comprising a metal compound, supported on a carrier material, wherein the above-mentioned drawbacks are avoided; thereto, the method according to the invention comprises the steps of a) treating of the carrier material with at least a metallasilsesquioxane, and b) calcining the treated carrier material. Metallasilsesquioxanes are known in the art.

Metallasilsesquioxanes are silsesquioxanes having one or more metal ligands . The terms "metallasilsesquioxanes" and "silsesquioxanes" are e.g. defined in Feher, F.J. et al, Polyhedron, 1995, 14, 3239, being incorporated herein by reference. Silsesquioxanes and metallasilsesquioxanes as used in this specification, also encompass partially condensed metallasilsesquioxanes and silsesquioxanes respectively. Examples of metallasilsesquioxanes are given in table 1 below, in conjunction with the following general formula for metallasilsesquioxanes :

{R¹Si0₁.₅)_n(R^2aSi0₁.₅)_m[(B)_q(0)_r]}_u(M)_v(Y)_W wherein n, m, r, u, v and w are integers of the same or of different values, and wherein R, B, M and Y are exemplified in table 1.

Table I Metallasilsesquioxanes

^a Cp=cyclopentane; a derivative is e.g. cyclopentadienyl . Instead of Cp or a derivate thereof methyl, benzyl, neopentyl, OH, halogen, or alkoxide can be used.

The metallasilsesquioxane mentioned in the table as no 6 is particularly preferred.

In this respect, it is to be noted that metallic oxide catalysts, produced by calcining one or more metallasilsesquioxanes are described in Maxim et al, Chin. J. Gem. (2001) , 19, 30-39. However, such materials have a limited accessible surface, are hardly or not resistant to attrition and cannot be produced in the desired forms, suitable for industrial application. Furthermore, very high amounts of silsesquioxanes are needed in order to provide a catalytically active surface. However, the catalyst according to the present invention, preformed carriers can be used, resulting in a catalyst of a defined shape of a defined particle size, having high resistance to attrition. Further, the carrier can provide an optimized surface, resulting in an optimal deposition of the metal oxides on the available surface and to a defined pore size and distribution of the catalyst, making the catalyst of the present invention highly suitable for industrial processes. It is known that by using the conventional impregnation techniques, it is extremely difficult to obtain homogeneously-dispersed, multicomponent mixed metal oxide moieties on a support surface.

Further, heterogeneous catalysts are often employed in processes where the catalyst is maintained in a gas or liquid suspension. The separation of the catalyst from reactants and products is made easier by using catalysts of a well-defined particle size according to the invention, which may easily be filtered or cycloned out of the mixture. The use of a catalyst support with a geometry providing maximum ease of separation from the reactant mixture results in a much more cost-effective process requiring less downstream processing. Up to now, it has been difficult if not impossible to provide a tailor-made catalyst geometry using simple, unsupported, bulk metal or metal-oxide catalysts.

Further, the catalyst according to the invention can advantageously be used in fixed-bed process. It is known that flowing reactant and products over the catalyst bed creates a pressure drop; the use of a supported catalyst according to the invention may significantly reduce the pressure drop across the bed and hence the costs related to pumping or compressing a fluid, which is flown over the bed, can be reduced.

In addition, the calcination of the silsesquioxane catalysts is shown to be an extremely exothermic process. Industrial-scale calcinations of bulk metallosilsesquioxane mixtures may therefore lead to uncontrollable temperature runaways . By supporting the silsesquioxanes according to the invention, far less silsesquioxane material is required, resulting to less production of undesired heat generated upon calcinations . In addition, a support material with a high thermal conductivity provides a more efficiently means to transport heat from a reactor to the cooling. This is both advantageous during the calcinations step and during reaction. Catalysts with high thermal conductivities as obtainable by the method according to the present invention may be employed in e.g. exothermic processes and may result in a significantly higher degree of isothermicity than catalysts of the art with lower thermal conductivities .

Furthermore, it is to be noted that particular silsesquioxanes, supported on a carrier material are described in WO 00/00519. However, the support has the function of presenting the silsesquioxanes as such, to be used as catalyst for the polymerisation of ethylene. In fact, the use of silsesquioxanes as a material for the formation of metal oxides on a carrier is not described, nor suggested in WO 00/00519.

It has been found, that by using a metallasilsesquioxane as starting material, providing the proper metal oxide (after calcination) results in metal oxide particles having a particle size that lies significantly below 10 nm. Furthermore, also metal oxide catalysts of metal ions that are not stable in solution can conveniently be prepared using the corresponding metallasilsesquioxane according to the invention.

The skilled person will be aware of proper treatment methods of the carrier material, resulting in deposition of the metallasilsesquioxane on the carrier material. Silsesquioxanes may be deposited on porous or nonporous materials via a number of methods. Porous materials are usually preferred as they offer the largest amount of surface area for deposition, which will result in more active catalyst for reaction. Nonporous materials such as but not restricted to metallic or ceramic plates may be used. These are particularly interesting substrates for use in automotive-based catalyst systems or for microreactor applications. Methods of depositing silsesquioxanes on supports are known in the art, such as e.g. pore-volume impregnation excess-impregnation deposition-precipitation, and spray coating

It has been found that metallasilsesquioxanes show an optimal distribution over the surface of the carrier, therewith providing a catalyst having homogeneously distributed metal oxides on the surface of the carrier, leading to an improved activity of the catalyst.

Calcination methods are known in the art and refer to treatment at elevated temperature in the presence of an oxidative medium, e.g. comprising oxygen and optionally a noble gas, although other oxidative media, comprising e.g. nitrogen oxides and/or water can be used. An overview of calcination techniques as can be used in the method of the present invention is e.g. given in "Handbook of Heterogeneous Catalysis, G. Ertl, J. Weitkamp, H. Knozinger, John Wiley & sons, ISBN3527292128" .

According to the invention, the catalyst is calcined to remove a desired amount of carbon from the silsesquioxanes. It may be advantageous to completely remove the carbon; in other cases, it may be desired to only partially oxidise the silsesquioxanes, therewith leaving a portion of the carbon in the structure. Calcination thus results in an oxidation state of the catalyst, therewith positively affecting the catalytic activity. Further, calcination has been found to import mechanical robustness to the catalytic system, and may lead to a desired change in the catalyst morphology, yielding, e.g. the desired surface area, depending on the nature of the chemistry in question.

Preferably, the carrier material is a solid porous support material and the treatment of step a) comprises impregnating the said support material with a solution, comprising the metallasilsesquioxane. Impregnation is a known technique for depositing matter on a porous support material, see Ertl et al, supra. Examples of suitable carrier materials are e.g. finely divided solid porous support materials, such as zeolites and other mineral clays, inorganic salts, such as MgCl₂, inorganic oxides, such as talk, silica, mesoporous silica, alumina, titania, zirconia, alumino silica, silica-alumina, mesoporous alumino phosphates, inorganic hydroxides, various forms of carbon, such as carbon black, graphite, fullerenic, exfoliated, setivated carbon, silicon carbide, base metal oxides, such as MgO, phosphates, sulphates, carbonates, resinous support materials, such as polyolefines, polystyrene. These carriers can be used as such or can be modified by a variety of pre-treatments before impregnation with the silsesquioxane solution. These pre- treatments may include reduction, oxidation, sealation and steam treatment. It will be appreciated by the skilled person that such pre-treatments can take place under different conditions of e.q. temperature and pressure with varying gas compositions and flow rates . Pre-treatment of the support may be advantageous to provide an optimal surface for the silsesquioxane to bind thereto. The finding of an optimal combination of support, support pre-treatment and impregnation method can easily be determined by the skilled artisan without the need for any inventive skills. Furthermore, the ligands of the silsesquioxanes, other than the envisaged metal, can be chosen in- such a way by the skilled person, to provide an optimal solubility in the envisaged solvent. Such ligands are indicated by "R" in the above table 1. The metallasilsesquioxanes are preferably dissolved in an organic solvent, known in the art, such as benzene, toluene, hexane, tetrahydrofurane. As indicated above the organic ligands attached to the silsesquioxane lattice may be modified to optimise the solubility. In a preferred embodiment, the carrier material comprises silica as it has been found that silica supported catalysts according to the invention show optimal attrition resistance and have the required surface qualities as indicated above. However, the choice of the support depends also on the chemistry to be performed; the skilled person will be capable of making the proper choice of a suitable carrier material for the envisaged aim.

Although catalysts containing a single metal or metal oxide are often excellent catalysts, there are many benefits to be obtained by combining two or more metal-containing species . Combining metal species often results in synergistic effects, which lead to improved yields to desired products. Additionally, the incorporation of certain metals improves catalyst lifetime by decreasing the rate of sintering or coke formation. It is often desirable to have a multifunctional catalyst capable of catalyzing a number of reactions at once. Aldol condensation with subsequent hydrogenation, hydration with subsequent dehydration and isomerization with subsequent hydrogenation represent just a few such reactions. Catalyst multifunctionality is most often realized by incorporating numerous metallic/metal-oxide species, each of which yields the desired catalytic effect. One of the primary advantages of the catalyst preparation method according to the invention is that it represents a flexible, easy to realize system, which allows the incorporation of many metallic species in various amounts in a single catalyst particle. As outlined above, the metal compound can e.g. be a metallic oxide, a metal compound, wherein the metal is a more reduced state, including the metal in neutral form. The metal compound is present on the catalyst in particle form. In a preferred embodiment, the metal compound, present on the catalyst comprises at least a metal oxide.

In an alternative embodiment, the method according to the invention further comprises a reduction step, providing the metal compound of the catalyst in a reduced state. The term "reduced state" herein refers to the metal compound having a reduced valency as compared with the valency of the said metal as present in the metallic oxide, as obtained after calcination. Calcination results in oxidation of the metal, present in the metallasilsesquioxane; by a reduction step, a catalyst can be obtained, wherein the metal is present in a less oxidised, i.e. reduced state.

In this respect it is to be noted that it has been found that calcination of iron containing silsesquioxanes primarily results in the formation of iron oxide particles, whereas calcination of Cr containing silsesquioxanes result in Cr-silicate particles. In this case, the Cr in the chrome silicate is in an oxidised state, but it is not in the metallic form. In general, the calcination conditions can be chosen such, that the desired oxidised state of the metal (in e.g. the metal oxide or metal silicate) can be obtained. E.g. the use of a stronger oxidizing agent (ex. oxygen instead of water) , higher temperatures, a higher partial pressure of oxidant or a longer calcination time will result in a more completely oxidized metal species. Transition metals are particularly easy to oxidize during calcination. Noble metals, in particular silver and gold are more difficult to oxidize.

By reduction, partially of completely reduced metal particles can be obtained. The reduction step can be carried out directly after impregnation, i.e. before the calcination step. Such an approach is advantageous, when the calcination is carried out in such a way, that the metal particles are not fully oxidised during the said calcination step, resulting in metal compounds, wherein the metal is still in a reduced state.

Further, such a partial calcination may result in incomplete removal of the carbon, present in the silsesquioxanes, resulting in a partially carbonised, supported catalyst. The metal compound may in such a case be present on the catalyst in the form of a metal carbide. Such a catalyst is particularly advantageous for reactions where a carbidic state of the metal is known or thought to be advantageous, such as the styrene synthesis using iron catalysts.

Preferably, the reduction step is carried out after the calcination step b) . After calcination, preferably under such conditions that the metal compound is in a fully oxidised, i.e. metallic oxide state, and wherein preferably the carbon content of the silsesquioxanes is completely removed by the calcination method, the thus obtained metallic oxide catalyst can be reduced, resulting in a catalyst, comprising a metal compound in a more reduced state. According to the invention, such reduced metal particles are in close proximity to one another, enhancing synergetic effects, in particular when a plurality of different metal compounds is present in the catalyst (see below) . As an example, a Fe-metallasilsesquioxane, present on a carrier can be calcined, resulting in a catalyst comprising iron oxide particles. By reducing the said catalyst, the iron oxide particles are reduced into iron particles, which can be the precursors for active catalytic centres, as known in the art. It is in this respect to be understood that the reduction step can be carried out according to any suitable method known in the art, using any suitable reducing agent. The most commonly used reductant is hydrogen. Other reducing agents such as CO, H₂S or ammonia may also be used. A general overview of suitable reduction reactions may also be found in Ertl et al, Supra.

Thus, in a very attractive embodiment, the invention provides a method for the preparation of a catalyst, comprising a plurality of different metal compounds, such as a multimetal or a multimetallic oxide catalyst, wherein the treatment of step a) the carrier is treated with a plurality of metallasilsesquioxanes having different metal ligands. It has surprisingly been found that by using metallasilsesquioxanes having different metal ligands, a catalyst comprising a plurality of different metal compounds, supported on a carrier can be produced wherein the different metal compounds, after calcination, are equally distributed over the surface of the carrier and wherein the different metal compounds show an improved homogeneously intermixed distribution, i.e. resulting in particles of the said metal compounds on the surface of the catalyst, wherein the said particles have a high degree of identity to one another, i.e. regarding size, morphology and/or crystal structure. The metal compound particles can be obtained in a predetermined and predefined composition, in contrast to multimetallic and multimetallic oxide catalysts, obtained according to the art, using different dissolved metal salts for the impregnation. Without being bound to any theory, it is believed that the different metal ions, present in the impregnation liquids of the art (i.e. metal salts) results in seggregation of the metal ions on the carrier, based on the fact that the different metal salts show different crystallisation characteristics to one another. This leads to an inhomogeneous distribution of the different metal oxides on the carrier. In addition to the different metallic oxide particles, the said particles are also different in size and can have a particle size of 10 nm or more.

For example, a combined iron/copper catalyst can be produced according to the present invention by co-impregnation of Fe- silsesquioxanes and copper containing silsesquioxanes, followed by calcination and subsequent reduction of the respective oxides into the neutral metal states of the said metals.

In a preferred embodiment, the different metallasilsesquioxanes are combined in a single solution, that is used for impregnating the carrier material. However, in another embodiment of the present invention, the carrier material can be impregnated in multiple subsequent steps, wherein in each step the carrier is impregnated with a different metall silsesquioxane or another combination of metallasilsesquioxanes.

It is however preferred to mix the different metallasilsesquioxanes into a single solution, resulting in mixed metallo silicate complexes leading to an optimal distribution of the different metals on the support and among the different metals. The solution of the different metallasilsesquioxanes can be obtained by mixing required amounts of solutions, each comprising a single species of metallasilsesquioxanes.

With multimetallic and "multimetallic oxide" a mixture of two or more different metal compounds such as neutral metals and metallic oxides, respectively, is meant; according to the invention the number of different metal compounds, e.g. metallic oxides on the carrier is virtually unlimited and may even be 5 or more. In a preferred embodiment the metallasilsesquioxane or a mixture of two or more thereof are mixed with a suitable amount of metal-free silsesquioxanes. The advantage of adding metal-free silsesquioxanes is to be able to adjust the metal/silicon ratio in the catalyst. This may be important for catalysts where the metal/silicon ratio has an effect on catalytic activity or mechanical strength. In such a case, preferably metal: silicon ratios of 1:1 - 1:10,000 are used.

The metal ligand of the metallasilsesquioxane is preferably chosen from the group, consisting of metals of the groups 1-6, 8, 10- 16 of the periodic table or a combination of two or more thereof. Preferably, the metal is chosen from Cr, Fr, Ti, Mg, Al, Ga, V, Mo, Ag, Au, or a combination of two or more thereof. It is to be noted that transition metals make particularly attractive catalysts because they may achieve a variety of oxidation states, which makes them extremely active for redox-type reactions (redox- reduction/oxidation) . Noble metal catalysts are particularly well suited for hydrogenation or dehydrogenation reactions .

As discussed above, any known calcination method can be used according to the method of the present invention. However, it is preferred that the temperature during the calcination step b) is between 300-1000°C, preferably between 300-800°C. It is prefered to calcinate at a low temperature as possible to minimise sintering of the metal. The calcination step b) is preferably executed in 0,5-10 hours, preferably in 1-5 hours and in a gaseous flow comprising 10-50 vol% 0₂, preferably 10-20 vol%. The gaseous flow preferably comprises air; most preferably being pure air, as air is an attractive and cost effective oxygen source.

Furthermore, the invention relates to a catalyst comprising a metal compound, supported on a carrier, obtainable by a method according to the present invention.

In a preferred embodiment, the invention provides a calcined catalyst comprising a metal compound, supported on a carrier, wherein the particle size of the metal compound on the carrier is less than 50 ran, preferably 8 nm or less, more preferably 6 nm or less, most preferably 4 nm or less.

In another preferred embodiment the invention relates to a calcined catalyst comprising a plurality of different metal compounds, supported on a carrier, wherein the carrier accommodates the different metal compound particles having a particle size of less than 50 nm, preferably 8 nm or less, more preferably 6 nm or less, and most preferably 4 nm or less. As outlined above, the said metal compound particles are of similar, preferably identical composition homogenously mixed on the carrier, and comprise two or more different metal compounds, preferably 2-5 different metal compounds, more preferably 2-4 different metal compounds.

As outlined above, the metal compound of the catalyst preferably comprises a metal oxide; in an alternative embodiment, the metal compound comprises the metal in a reduced state, such as in the form of neutral metal particles.

Preferably, the weight ratio metal compound: support in the catalyst according to the invention is between 0,001-20:99,999-80, preferably 0,01-10:99,99-90, more preferably 0,1-5:99,9-95.

Furthermore, the invention relates to the use of a catalyst according to the invention as heterogeneous catalyst. As outlined above, the catalyst according to the present invention shows an improved activity compared to the catalysts, known in the art. Without being bound to any theory, it is thought that the improved catalyst activity is due to the small particle size and homogeneous morphology, which offers a large active surface area for reaction with a large degree of homogeneity. The ability to easily create tailor-made catalysts with well defined and identical metal particles enables one to carry out reactions with an unparalleled degree of control over product selectivity and reactant conversion. In addition, when using more than one metal species, the close proximity of the metal species, which may be realized with this method significantly enhances the synergetic effects of the metals on one another and results in an overall, more efficient use of the metal species present (as opposed to having separate "islands" of metal species, which only exhibit synergy at a limited interfacial area, as obtained with catalysts of the art) .

The invention will now be further examplified by the following examples, which however are not intended to limit the scope of the invention. Example 1 :

Ammonia oxidation to nitrogen and water.

Ammonia is often used as a reducing agent for removing nitrogen oxides from power-plant emissions and other industrial-NOx emission sources. Despite the recent advances in process control enabling extremely accurate dosing of ammonia as a function of the measured NOx concentration, a small amount of ammonia is always released into the atmosphere. This is undesirable and a cheap, simple method for converting ammonia to inert nitrogen and water is desired. Catalysts containing iron and chrome were synthesized and tested for the oxidation of ammonia to nitrogen and water. A comparison was made between a silica-supported catalyst, which was synthesized via impregnation with iron and chrome nitrate solutions and one synthesized using a mixture of iron and chrome metallosilsesquioxane precursors. The catalyst prepared using silsesquioxane precursors exhibited a 5-50% improvement in selectivity to nitrogen and water in the oxidation of ammonia depending on the conditions used.

Example 2 :

The catalysts of example 1 were tested in the oxidation of CO to C02. This is also a reaction, which is desirable in order to reduce the CO emissions from both stationary (power plant, factories, etc) and mobile (cars) sources. The catalyst prepared using metallosilsesquioxane precursors exhibited a weight-normalized conversion of CO to C02, 5 to 50% higher for the catalyst prepared using metallosilsesquioxane precursors, depending on the testing conditions used.

Example 3 :

TEM and Raman analysis of the catalysts of example 1 indicate that the catalysts prepared via using nitrate precursors indicate that iron oxide and monochromates, The catalyst synthesized with nitrate salt precursors yielded relatively large particles of iron and chome oxide. Very small particles of bi-metallic oxides were observed in the Fe-Cr-Si-0 system synthesized using silsesquioxane precursors .

Claims

C L A I M S

1. Method for the preparation of a catalyst comprising a metal compound, supported on a carrier material comprising the steps of a) treating of the carrier material with at least a metallasilsesquioxane, and b) calcining the treated carrier material.

2. Method according to claim 1, wherein the carrier material is a solid porous support material and wherein the treatment of step a) comprises impregnating the said support material with a solution, comprising the metallasilsesquioxane.

3. Method according to any of the preceding claims, wherein the metal compound comprises at least a metal oxide.

4. Method according to any of the preceding claims, further comprising a reduction step, providing the metal compound of the catalyst in a reduced state.

5. Method according to claim 4, wherein the reduction step is carried out after the calcination step b.

6. Method for the preparation of a catalyst comprising a plurality of different metal compounds according to any of the preceding claims, wherein in the treatment of step a) the carrier is treated with a plurality of metallasilsesquioxanes having different metal ligands .

7. Method according to any of the preceding claims, wherein the metal ligand of the metallasilsesquioxane is chosen from the group, consisting of Metals of the groups 1-6, 8, 10-16 of the periodic table or a combination of two or more thereof.

8. Method according to claim 7, wherein the metal is chosen from Cr, Fe, Ti, Mg, Al, Ga, V, Mo, Ag, Au, or a combination of two or more thereof.

9. Method according to any of the preceding claims, wherein the temperature during the calcination step b) is between 300-1000°C, preferably between 300-800°C.

10. Method according to any of the preceding claims, wherein the calcination step b) is executed in 0,5-10 hrs, preferably 1-5 hours.

11. Method according to any of the preceding claims, wherein the calcination step b) is executed in a gaseous flow comprising 10-50 vol.% 0₂, preferably 10-20 vol.%.

12. Catalyst comprising a metal compound supported on a carrier obtainable by the method according to any of the preceding claims.

13. Calcined catalyst comprising a metal compound supported on a carrier, wherein the particle size of the metal compound on the carrier is less than 50 nm, preferably 8 nm or less, more preferably 6 nm or less, most preferably 4 nm or less.

14. Calcined catalyst comprising a plurality of different metal compounds supported on a carrier, wherein the carrier accomodates the different metal compound particles having a particle size of less than 50 nm, preferably 8 nm or less, more preferably 6 nm or less, most preferably 4 nm or less.

15. Catalyst according to any of the claims 12-14, wherein the metal compound comprises a metal oxide.

16. Catalyst according to any of the claims 12-14, wherein the metal compound comprises the metal in reduced state.

17. Catalyst according to any of the claims 12-16, wherein the weight ratio metal compound: support is between 0,001-20:99,999-80, preferably 0,01-10:99,99-90, more preferably 0,1-5:99,9-95.

18. use of a catalyst according to any of the claims 12-17, as a heterogenous catalyst.

19. Use of a catalyst according to any of the claims 12-18, for the oxidation of propylene, propane, butane, butylene, CO, cyclohexane, the oxi-dehydrogenation of methanol, the synthesis of styrene, the partial oxidation of methane, the reduction of nitrogen oxide, and/or in the Fischer Tropsch synthesis.