DE19925926A1 - Catalysts based on titanium-containing, organic-inorganic hybrid materials for the selective oxidation of hydrocarbons - Google Patents

Abstract

The invention relate to supported compositions containing gold and/or silver particles and Ti-containing, organic-inorganic hybrid materials. The invention also relates to a method for producing said compositions and to their use as a catalyst for the selective oxidation of hydrocarbons. The catalytically active compositions present high levels of selectivity and productivity.

Description

The present invention relates to supported compositions containing gold and / or silver particles and titanium-containing, organic inorganic hybrid materials, a process for their preparation and their use as a catalyst for selective oxidation of hydrocarbons. The catalytically active together Settlements show high selectivities and productivity.

The direct oxidation of ethene to ethene oxide by molecular oxygen is good known and becomes commercial for the production of ethene oxide in the gas phase applied. The typical catalyst for this application contains metallic or ionic silver, possibly modified with various promoters and Activators. Most of these catalysts contain a porous, inert Catalyst carriers with small surfaces such. B. alpha alumina on the Silver and promoters were applied. An overview of the direct oxidation of Ethene in the presence of supported silver catalysts was developed by Sachtler et al. in Catalysis Reviews: Science and Engineering, 23 (1 & 2), 127-149 (1981) posed.

It is also known that these silver catalysts and the reaction conditions, which have proven to be beneficial for the production of ethene oxide, none at all comparably good results in the direct oxidation of higher olefins, such as Propene, lead (US 5 763 630, US 5 703 254, US 5 760 254) and maximum propene oxide selectivities of approx. 50% can be achieved. In general, the Direct oxidation of these higher olefins with molecular oxygen in the gas phase - even in the presence of catalysts - not below 200 ° C, and it is therefore difficult to use oxidation-sensitive oxidation products, such as epoxies, selectively manufacture, since the subsequent reactions of these products are often faster than that Oxidation of the olefins used themselves. Another problem results  from the oxidation sensitivity of the allyl present in higher olefins groups.

For this reason, propene oxide is currently being phased out in the chemical industry finally produced indirectly in the liquid phase.

In the US Pat. No. 5,623,090 a gas phase direct oxidation of propene is disclosed Propene oxide with relatively small propene conversions (0.5-1% propene conversion based on one 10% propene feed concentration), but propene oxide selectivities of <90% described. It is a gold-titanium dioxide catalyzed Gas phase oxidation with molecular oxygen and hydrogen at temperatures from 40-80 ° C. Commercial titanium dioxide (anatase) is used as catalyst, which is coated with nanoscale gold particles. More drastic reaction conditions such as B. An increase in temperature to <100 ° C or an increase in pressure does not lead to Increase of productivity. This method has in addition to the relatively small Propen sales have the major disadvantage that all catalysts become strong over time deactivate. Typical half-lives at normal pressure and 50 ° C are 30- 150 minutes. The temperature and / or pressure increase described shorten the Half-lives continue.

Catalysts are also known in which gold particles are supported on a support, consisting of dispersed titanium centers on an inorganic silicon matrix, be applied (WO 98 00415 A1; WO 98 00414 A1; EP 0 827 779 A1). All these materials obtained by impregnation with subsequent calcination show relatively low propene conversions, they deactivate over time (typical Half-lives are around 5-50 h) and therefore cannot be carried out on an industrial scale Systems are used.

Furthermore, catalysts are known in which gold particles are deposited on microporous, crystalline framework silicates with a defined pore structure, in which silicon tetrahedra places areomorphically substituted by titanium (e.g. TS-1, TS-2, Ti zeolites such as Ti  Beta, Ti-ZSM-48 or titanium-containing, mesoporous molecular sieves such as B. Ti-MCM-41 or Ti-HMS) can be applied (WO 9800413 A1). All of these gold silicalite or Gold-zeolite structures show good selectivities, the sales of the coal Hydrogen and especially the catalyst life are for the application in the chemical industry completely inadequate.

The described methods for catalyst preparation are in relation to catalys Gate activity and service life extremely unsatisfactory. For technical processes that Working with low-activity catalysts, huge reactors are needed. Short catalyst downtimes result in production downtime during regeneration phase or require a redundant, cost-intensive product way.

The earlier applications DE 199 18 431.3 and DE 199 20 753.4 describe Precious metal-containing Ti-Si mixed oxides as catalysts for the direct oxidation of Hydrocarbons, as well as their production via the sol-gel process. Organic inorganic hybrid materials as carriers are not disclosed.

It is known to use organic inorganic hybrid materials as a paint component to be used (e.g. EP-A-743 313). The combination with precious metals and titanium and their use as a catalyst is unknown.

It is therefore desirable to develop new catalysts that can excellent selectivities high activities with technically interesting downtimes reachable.

An object of the present invention was therefore to develop new catalysts with high activities and excellent selectivities.

Another task was to create a process for this To develop catalysts.  

Another task was a technologically simple gas phase process for the selective oxidation of hydrocarbons with a gaseous oxide To provide agents on these catalysts, which at high Activities, very high selectivities and technically interesting catalyst tool life leads to high yields and low costs.

Another task was to find an alternative catalyst for direct To provide oxidation of hydrocarbons. Another object was to address the disadvantages of the known catalysts to at least partially eliminate.

According to the invention, the objects are achieved by supported compositions containing gold and / or silver particles and titanium-containing, organic inorganic Hybrid materials solved.

Organic-inorganic hybrid materials in the sense of the invention are organically modified amorphous glasses which are preferably formed in sol-gel processes via hydrolysis and condensation reactions of mostly low molecular weight compounds and contain organic groups bridging in the network. They have at least one structural element of the formula (I)

[R ¹ ] _j -SiR ² _k (O _1/2 ) _4-kj (I)

on, where
j is 1, 2 or 3 and
k represents 0, 1 or 2 and
k + j ≦ 3
R ^{1 is} a C ₁ to C ₁₀ alkylene radical bridging Si atoms and
R ^{2 represents} an optionally substituted alkyl or aryl radical.

The organic-inorganic hybrid materials preferably have a structural element of the formula (II)

[R ¹ ] _j -SiR ² _k (O _1/2 ) _4-kj (II)

on, where
j is 1,
k represents 0, 1 or 2 and
k + j ≦ 3
R ^{1 is} a C ₁ to C ₄ alkylene radical bridging Si atoms, and
R ^{2 is} a methyl or ethyl radical.

The formulation "O _1/2 " in the formulas (I) and (II) denotes bridging, difunctional oxygen, that is, for. B. a structural element Si-O-Si or Si-O-Ti.

The alkylene radical R ¹ in the formulas (I) and (II) is preferably linked to a chain-shaped, star-shaped (branched), cage-shaped or, particularly preferably, ring-shaped structural element. The ring-shaped structural element can be, for example, [-O-Si (CH ₃ ) -] ₃ or [-O-Si (CH ₃ ) -] ₄ .

The alkylene radical includes all alkylene, arylene and or alkylarylene radicals understood in the range from 1 to 10 carbon atoms, such as Methylene, ethylene, n-propylene, i-propylene, n-butylene, i-butylene, t-butylene, n- Pentylene, i-pentylene, neo-pentylene, n-hexylene, cyclenohexylene, i-hexylene, Heptylene, octylene, nonylene, decylene and phenylene, the radicals being cyclic or exist as branched or unbranched chains and may be substituted can. All residues that are not disadvantageous also come into question as substituents a catalyst component, such as. B. titanium or a promoter, such as e.g. B. alkyl, aryl or alkoxy radicals.  

In a particularly preferred embodiment of the invention, the organically inorganic hybrid materials have one or more of the following structural elements:

• a) Si [(C ₂ H ₄ ) Si (CH ₃ ) ₂ (O _1/2 )] ₄
• b) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) ₂ (O _1/2 )]} ₄
• c) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) (O _1/2 ) ₂ ]} ₄
• d) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (O _1/2 ) ₃ ]} ₄

Contain the organic-inorganic hybrid materials in the sense of the invention between 0.1 and 6% by weight of titanium, preferably between 0.8 and 5% by weight, particularly preferably between 1.5 and 4% by weight. The titanium is in and is in oxidic form preferably chemically via Si-O-Ti bonds in the organic inorganic hybrid material installed or connected.

The catalytic activity of these materials appears to be at higher titanium levels cannot be increased linearly with the total titanium content. This showed us that not all titanium centers have the same catalytic activity. We take indicates that in active catalysts titanium via heterosiloxane bonds to silicon is bound.

In addition to titanium, the organic-inorganic hybrid mate according to the invention rialien further foreign oxides, so-called promoters, from group 5 of the Perio densystems according to IUPAC (1985), such as vanadium, niobium and tantalum, in particular preferably tantalum, group 8, particularly preferably Fe, metals of group 15, such as Arsenic, antimony and bismuth, particularly preferably antimony and metals from the group 13, such as boron, aluminum, gallium, indium and thallium, are particularly preferred Contain aluminum and boron.

Most of these promoters are homogeneous, i. H. with few domains education, before. The built-in promoters "M" are in the organic anorga African hybrid materials highly disperse and are largely via Element-O-Si  Ties bound. The chemical composition of these materials can be vary over a wide range. The proportion of the promoter element is in the range from 0.05-10%. Of course, several different promoters can also be used be used. The promoters are preferred in the form of Solvent-soluble promoter precursor compounds, such as promoter salts or Promoter-organic compounds used.

These promoters can both increase the catalytic activity of the composition as well as the service life of the composition in catalytic oxidation reactions of hydrocarbons increase.

Organic inorganic hybrid materials with a large specific surface area are preferred. The specific surface area should be at least 1 m ² / g, preferably in the range of 25-700 m ² / g.

Organic inorganic hybrid materials with a modified surface are also used preferred area. Modified surface in the sense of the invention means that the Proportion of surface silanol groups through covalent or coordinative attachment formation of groups selected from silicon alkyl, silicon aryl, fluorine-containing alkyl and / or fluorine-containing aryl groups.

The supported composition according to the invention contains gold and / or silver the organic-inorganic hybrid material as carrier material. In the catalytic active state harbors gold and / or silver mainly as elemental metal (Analysis by X-ray absorption spectroscopy). Small gold and / or Silver components can also be present in a higher oxidation state. To Judging by TEM images is the largest proportion of gold available and / or silver on the surface of the carrier material. It is a matter of Gold and / or silver clusters on a nanometer scale. They preferably have gold particles have a diameter in the range from 0.5 to 50 nm, preferably 0.5 to 15 nm and particularly preferably 0.5 to 10 nm. The silver particles preferably have one  Diameters in the range from 0.5 to 40 nm, preferably 0.5 to 10 nm and particularly preferably 0.5 to 7 nm.

The gold concentration should be in the range of 0.005 to 4% by weight, preferably 0.01 to 2 wt .-% and particularly preferably 0.08-1.5 wt .-% gold.

The silver concentration should be in the range of 0.01 to 8% by weight, preferably 0.1 to 6% by weight and particularly preferably from 0.5 to 4% by weight of silver.

Effect higher gold and / or silver concentrations than the ranges mentioned no increase in catalytic activity. For economic reasons, the Precious metal content the minimum amount necessary to obtain the highest cataly sator activity.

The tasks are still solved by a manufacturing process of the supported compositions containing gold and / or silver particles and Ti-containing, organic inorganic hybrid materials.

The Ti-containing, organic-inorganic hybrid materials are sol-gel Processes. This is done, for example, by mixing suitable, mostly low molecular weight compounds in a solvent, after which by adding Water and optionally catalysts (e.g. acids, bases and / or metal organic compounds) the hydrolysis and / or condensation reactions be directed. The execution of such sol-gel processes is a basic requirement for the person skilled in the art additionally known.

Suitable low molecular weight compounds are e.g. B. organic inorganic bandage medium, silicon, titanium and promoter precursors. Low molecular weight is in the sense of the invention for monomeric or oligomeric.  

The sol-gel process is based on the polycondensation of hydrolyzed, colloidally dissolved metal component mixtures (sol) with the formation of an amorphous, three-dimensional network (gel). The following scheme serves to illustrate this:

Suitable starting materials are organic inorganic binders and all soluble titanium and silicon compounds known to the person skilled in the art can serve as a precursor for the corresponding oxides or hydroxides, such as corresponding alkoxides, soluble salts, and titanium or organosilicon Links.

Although all salts such as e.g. B. halides, nitrates and hydroxides can be used can, the alkoxides, for. As ethoxide, propoxide, etc., of these metals prefers.

Organic-inorganic binders in the sense of the invention are polyfunctional Organosilanes, e.g. B. polyfunctional silanols and / or alkoxides, with at least 2 silicon atoms bridged via a C1 to C10 alkylene radical.

The following may be mentioned as preferred organic inorganic binders:

• a) Si [(C ₂ H ₄ ) Si (OH) (CH ₃ ) ₂ ] ₄
• b) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OH) (CH ₃ ) ₂ ]} ₄
• c) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OC ₂ H ₅ ) ₂ (CH ₃ ]} ₄
• d) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OCH ₃ ) (CH ₃ ) ₂ ]} ₄
• e) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OC ₂ H ₅ ) ₃ ]} ₄

Syntheses of organic-inorganic binders and processes for through Management of sol-gel processes with these are described, for example, in EP 0 743 313, EP 0 787 734 and WO 98/52992.

Suitable silicon precursors include silicon alkoxides such as e.g. B. Si (OC ₂ K ₅ ) ₄ , Si (OCH ₃ ) ₄ , (H ₃ C) Si (OC ₂ H ₅ ) ₃ , (C ₆ H ₅ ) Si (OC ₂ H ₅ ) ₃ . Instead of monomeric alkoxides, their condensation products can also be used. Commercially available are e.g. B. Si (OC ₂ H ₅ ) ₄ condensates. Furthermore, polymeric systems such as. B. poly (diethoxysiloxane) can be used.

Suitable titanium precursor compounds as catalytic titanium species are from the Known in the art, such as soluble titanium salts (e.g. titanium halides, nitrates, sulfates), titanium salts of inorganic or organic acids and titanium acid esters.

Titanium derivatives such as tetraalkyl titanates with alkyl groups of C ₁ -C ₆ such as methyl, ethyl, n-propyl, n-butyl, iso-butyl, tert-butyl etc., or other organic titanium species such as titanium acetylacetonate, dicyclopentadienyl titanium dichloride are preferably used. Tetra-n-butyl orthotitanate, titanium acetylacetonate, titanocene dichloride and titanium tetrachloride are preferred titanium precursors. The titanium precursor compounds can also in the presence of complexing components such. B. acetylacetone or ethyl acetoacetate.

Suitable promoter precursor compounds are, for example, promoter salts, Pro motor complex compounds, promoter-organic compounds or promoter alkoxides. Alkoxide compounds are preferably used.

Preferred solvents for the sol-gel process are alcohols such as. B. methanol, Ethanol, isopropanol or butanol, ketones such as e.g. As acetone, and ethers such as. B. THF or tert-butyl methyl ether.  

In principle, any implementation of sol-gel known to the person skilled in the art is Processes for the synthesis of the Ti-containing, organic-inorganic Hybrid materials possible. The generation of -Si-O-Ti groups succeeds for example by simultaneous hydrolysis and / or condensation of Si and Ti Precursors, by reacting the organic-inorganic binders with Ti Precursors with or without subsequent addition of the Si precursors or by simultaneous implementation of organic-inorganic binders, Ti and Si precursors.

In a preferred embodiment, the Si precursor is in a solvent submitted, with the addition of a catalyst with a deficit of water, based to the theoretically necessary amount, hydrolyzed, then the Ti-Verbin dung added, further water, optionally with a catalyst, added and then added the organic inorganic binder.

After gel formation, which depends on the composition, the Catalyst, the amount of water and the temperature after a few minutes can take a few days; the gel becomes immediately or after an aging period of dried up to 30 days. If necessary, to complete the Hydrolysis and condensation reactions one or more treatments of the moist and / or already dried gels with an excess of water or Water vapor take place. Drying is preferably between 50 and 250 ° C, particularly preferably between 100 and 180 ° C.

The materials can optionally be powdered before or after drying be crushed (e.g. by grinding), or used as shaped bodies.

The noble metals can be in the form of precursor compounds such as salts or organic complexes or compounds during the sol-gel process ben, or after preparation of the gel in a known manner, for. B. by  Impregnation or precipitation can be applied. If necessary, follows this step a surface modification of the composition.

The surface modification can be done both before and after the precious metal assignment.

Modifying in the sense of the invention is in particular the application of Groups selected from silicon alkyl, silicon aryl, fluorine-containing alkyl or fluorine-containing aryl groups on the surface of the supported composition understood, the groups covalently or coordinatively to the functional Groups (e.g. OH groups) are bound on the surface. However also any other surface treatment expressly within the scope of the invention locked in.

The modification is preferably carried out with organosilicon and / or fluorine-containing ones organosilicon or organic compounds, the organosilicon Compounds are preferred.

Organosilicon compounds include all known to those skilled in the art Silylating agents in question, such as organic silanes, organic silylamines, organic Silylamides and their derivatives, organic silazanes, organic siloxanes and others organosilicon compounds, of course also in combination can be used. Also among organosilicon compounds explicitly also compounds made of silicon and partially or perfluorinated orga African remnants subsumed.

Specific examples of organic silanes are chlorotrimethylsilane, dichlorodi methylsilane, chlorobromodimethylsilane, nitrotrimethylsilane, chlorotrimethylsilane, Iododimethylbutylsilane, chlorodimethylphenylsilane, chlorodimethylsilane, dimethyl-n propylchlorosilane, dimethylisopropylchlorosilane, t-butyldimethylchlorosilane, tripropyl chlorosilane, dimethyloctylchlorosilane, tributylchlorosilane, trihexylchlorosilane, Di  methylethylchlorosilane, dimethyloctadecylchlorosilane, n-butyldimethylchlorosilane, Bromomethyldimethylchlorosilane, chloromethyldimethylchlorosilane, 3-chloropropyldime thylchlorosilane, dimethoxymethylchlorosilane, methylphenylchlorosilane, triethoxy chlorosilane, dimethylphenylchlorosilane, methylphenylvinylchlorosilane, benzyldimethyl chlorosilane, diphenylchlorosilane, diphenylmethylchlorosilane, diphenylvinylchlorosilane, Tribenzylchlorosilane and 3-cyanopropyldimethylchlorosilane.

Specific examples of organic silylamines are N-trimethylsilyldiethylamine, Penta fluorophenyldimethylsilylamine including N-trimethylsilylimidazole, N-t-butyldi methylsilylimidazole, N-dimethylethylsilylimidazole, N-dimethyl-n-propylsilylimida zole, N-dimethylisopropylsilylimidazole, N-trimethylsilyldimethylamine, N-trime thylsilylpyrrole, N-trimethylsilylpyrrolidine, N-trimethylsilylpiperidine and 1-cyano ethyl (diethylamino) dimethylsilane.

Specific examples of organic silylamides and their derivatives are N, O-Bistri methylsilylacetamide, N, O-bistrimethylsilyltrifluoroacetamide, N-trimethylsilylacet amide, N-methyl-N-trimethylsilylacetamide, N-methyl-N-trimethylsilyltrifluoroacet amide, N-methyl-N-trimethylsilylheptafluorobutyramide, N- (t-butyldimethylsilyl) -N-tri fluoroacetamide and N, O-bis (diethylhydrosilyl) trifluoroacetamide.

Specific examples of organic silazanes are hexamethyldisilazane and heptamethyl disilazane, 1,1,3,3-tetramethyldisilazane, 1,3-bis (chloromethyl) tetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane and 1,3-diphenyltetramethyldisilazane.

Examples of other organosilicon compounds are N-methoxy-N, O-bistrime thylsilyl trifluoroacetamide, N-methoxy-N, O-bistrimethylsilycarbamate, N, O-Bistri methylsilyl sulfamate, trimethylsilyl trifluoromethanesulfonate and N, N'-bistrimethyl silylurea.  

Preferred silylation reagents are hexamethyldisilazane, hexamethyldisiloxane, N-methyl-N- (trimethylsilyl) -2,2,2-trifluoroacetamide (MSTFA) and trimethyl chlorine silane.

The supported compositions according to the invention containing gold and / or silver particles and Ti-containing, organic-inorganic hybrid materials can be described in the dried state approximately by the following empirical formula (the residues formed after modification on the surface and possibly incompletely reacted groups are not here considered):

Hyb.SiO ₂ .TiO ₂ .MO _x .E (III)

Hyb in formula (III) means that in the sol-gel process from the organic anorga constituents formed by the binder, M is a promoter, preferably Ta, Fe, Sb, Al or combinations thereof, y is the effective number for saturation the valences of M and E the precious metal.

The composition can be varied over a wide range. The percentage of Hyb can be between 0.5 and 98% by weight. It is preferably between 20 and 80%, particularly preferably between 30 and 60%. The proportion of TiO is between 0.2 and 10% (corresponds to 0.1 to 6% Ti), preferably between 1.3 and 8.3%, particularly preferably between 2.5 and 6.7%. The proportion of MO _x is between 0.06 and 12% and the proportion of E between 0.005 and 8%. For gold it is preferably between 0.01% and 2%, for silver it is preferably between 0.1 and 4%. The proportion of SiO ₂ can vary between 0 and 99%. The proportion is preferably between 10 and 80%, particularly preferably between 40 and 70%.

Surprisingly, we have found that the supported together according to the invention settings compared to previously known catalyst systems for catalyzing table oxidation of alkenes and alkanes by several orders of magnitude show higher catalytic activity and good catalyst life.  

Therefore, the use of the supported assembly according to the invention Another solution of the posed for the oxidation of hydrocarbons Object and also another object of the invention.

The after a long time partially deactivated catalysts can be both thermally (up to 250 ° C) and by washing with suitable solvents, such as. B. alcohols, or regenerate with dilute hydrogen peroxide solutions (z. B. 8% H ₂ O ₂ - methanol solution).

The composition according to the invention can in principle be applied to all hydrocarbons fabrics are applied. The term hydrocarbon is used Saturated or saturated hydrocarbons such as olefins or alkanes understood that can also contain heteroatoms such as N, O, P, S or halogens. The too oxidie Rende organic component can be acyclic, monocyclic, bicyclic or poly cyclic and can be monoolefinic, diolefinic or polyolefinic. At organi Components with two or more double bonds can double bindings are conjugated and non-conjugated. Coal is preferred oxidized substances from which such oxidation products are formed, the Partial pressure is low enough to keep the product away from the catalyst remove. Unsaturated and saturated hydrocarbons with 2 to 20, preferably 2 to 10 carbon atoms, in particular ethene, ethane, propene, Propane, isobutane, isobutylene, 1-butene, 2-butene, cis-2-butene, trans-2-butene, 1,3- Butadiene, pentene, pentane, 1-hexene, 1-hexane, hexadienes, cyclohexene, benzene.

The organic-inorganic hybrid materials enable a kind of "catalyst design ", i.e. a comprehensive and at the same time targeted influencing of the material properties such as B. the hydrophobicity (polarity) and / or the porosity. Surprisingly, this leads to significantly improved catalysts. The Surface polarities directly affect the activities and selectivities of the Catalysts, e.g. B. water formed in side reactions to hydrophilic  Surfaces are easily adsorbed and lead to unwanted on and off reactions of the already formed epoxides. The hydrophobicity of this Materials is determined by the number and type of terminal and before all bridging Si-C bonds determined. These have compared to others organic bonds, such as B. Si-O-C bonds, the additional advantage that they are largely chemically inert, d. H. against hydrolysis and oxidation reactions are insensitive.

In contrast, is a common feature of all previously known Kataly the application of gold particles to purely inorganic substrates. Even with you through a subsequent surface modification, e.g. B. by applying terminal silicon alkyl groups, influencing the Surface polarity is conceivable, but this depends, among other things, on only a very limited number of reactive groups on the surface (e.g. Si-OH) scope possible.

The supported compositions can be in any physika be used form for oxidation reactions, for. B. ground powders, spherical particles, pellets, extrudates, granules etc.

A preferred use is the use for gas phase oxidation of Hydrocarbons, especially olefins, in the presence of oxygen and Hydrogen and the supported compositions of the invention. Here become selectively from olefins epoxides, from saturated secondary hydrocarbons substances ketones and alcohols obtained from saturated tertiary hydrocarbons. Depending on the starting material used, the catalyst service lives are a few days, Months, or longer.

The relative molar ratio of hydrocarbon, oxygen, hydrogen and Optionally, a dilution gas can be varied over a wide range.  

The molar amount of hydrocarbon used in relation to the total Mole number of hydrocarbon, oxygen, hydrogen and diluent gas can can be varied over a wide range. An excess of coals is preferred hydrogen, based on the oxygen used (on a molar basis). The The hydrocarbon content is typically greater than 1 mol% and less than 60 mol%. Hydrocarbon contents in the range of 5-35 mol% are preferred, particularly preferably used from 10-30 mol%. With rising hydro Productivity and hydrogen combustion are increased lowered.

The oxygen can be used in a variety of forms, e.g. B. Molecular Oxygen, air and nitrogen oxide. Molecular oxygen is preferred. The molar proportion of oxygen - in relation to the total number of moles from hydrocarbon, Oxygen, hydrogen and diluent gas - can vary widely become. The oxygen in molar deficiency to the hydrocarbon is preferred fabric used. Preferred are in the range of 1-12 mol%, particularly preferred 6-12 mol% oxygen used. With increasing oxygen levels the Productivity increased. For safety reasons, there is an oxygen content to choose from less than 20 mol%.

In the absence of hydrogen, the supported Zu according to the invention show compositions have very low activity and selectivity. That is up to 180 ° C Productivity low in the absence of hydrogen, higher at temperatures In addition to partial oxidation products, large quantities of carbon dioxide become 200 ° C educated. Any known hydrogen source can be used, such as. B. Moleku Larer hydrogen from dehydrogenation of hydrocarbons and alcohols. In In another embodiment of the invention, the hydrogen can also be used in one upstream reactor are generated in situ, for. B. by dehydrogenation of propane or isobutane or alcohols such as. B. isobutanol. The hydrogen can also be used as Complex-bound species, e.g. B. Catalyst-hydrogen complex, in the reak tion system. The molar proportion of hydrogen - in relation to the Ge  total number of moles from hydrocarbon, oxygen, hydrogen and diluent gas - can be varied in a wide range. Typical hydrogen levels are included greater than 0.1 mol%, preferably at 5-80 mol%, particularly preferably at 10-65 mol%. Productivity increases with increasing hydrogen levels.

The essential starting gases described above can optionally also be used a diluent gas such as nitrogen, helium, argon, methane, carbon dioxide or similar, inert gases are used. Mixtures of Inert components described can be used. The inert components additive is used to transport the heat released by this exothermic oxidation reaction and cheap from a safety point of view. If the invented Process carried out according to the invention in the gas phase are preferably gaseous Dilution components such as B. nitrogen, helium, argon, methane and possibly Water vapor and carbon dioxide are used. Water vapor and carbon dioxide are not completely inert, but at very low concentrations (<2% by volume) a positive effect.

When the invention is carried out in the liquid phase, one is expediently oxidation-stable and thermally stable inert liquid selected (e.g. alcohols, Polyalcohols, polyethers, halogenated hydrocarbons). The invention Carried compositions are also in the liquid phase for the oxidation of Suitable for hydrocarbons. Both in the presence of organic hydroper oxides (R-OOH) are described in the liquid phase as highly selective olefins benen catalysts to epoxides, as well as in the presence of oxygen and hydrogen, olefins are described in the liquid phase in a highly selective manner ben converted catalysts to epoxides.

We have found that the selective oxidation reaction described above is a has high catalyst structure sensitivity. In the presence of nanodisperse Gold and / or silver particles in the supported composition became one Increased productivity observed for selective oxidation product.  

The close spatial interplay of gold and / or silver and titanium oxide (perimetric interface) on the organic-inorganic carrier works particularly well efficient, d. H. there are excellent epoxidation catalysts in the presence of Receive oxygen and hydrogen. The activity of the catalysts and the catalyze sator life can be reduced if necessary by installing small quantities Promoters, e.g. B. foreign metals, especially by incorporating tantalum and / or iron and / or antimony and / or aluminum, further increase. The invention Compositions can be processed easily and inexpensively in terms of process technology manufacture on a technical scale.

The characteristic features of the present invention are evident of catalyst preparations and catalytic test reaction in the following play illustrated.

It goes without saying that the invention is not limited to the examples below is limited.  

Examples Instructions for testing the catalysts (test instructions)

A metal tube reactor with an inner diameter of 10 mm and a length of 20 cm was used, which was tempered by means of an oil thermostat. The reactor was supplied with a set of four mass flow controllers (hydrocarbon, oxygen, hydrogen, nitrogen) with feed gases. For the reaction, 0.5 g of powdered catalyst were placed at 150 ° C and 1 bar pressure. The reactant gases were metered into the reactor from above. The standard catalyst load was 4 l / g cat./h. As a "standard hydrocarbon" propene was chosen as an example. To carry out the oxidation reactions, a gas stream enriched with nitrogen, hereinafter always referred to as the standard gas composition, was selected: N ₂ / H ₂ / O ₂ / C ₃ H ₆ : 15/65/10/10%. The reaction gases were analyzed quantitatively by gas chromatography. The gas chromatography separation of the individual reaction products was carried out using a combined FID / TCD method in which three capillary columns are run:
FID: HP-Innowax, 0.32 mm inner diameter, 60 m long, 0.25 µ layer thickness.
WLD: series connection of
HP-Plot Q, 0.32 mm inner diameter, 30 m long, 20 µ layer thickness HP-Plot Molsieve 5 A, 0.32 mm inner diameter, 30 m long, 12 µ layer thickness.

example 1

This example describes the preparation of a catalyst consisting of a titanium-containing, organic-inorganic hybrid material, which surface modes fected and subsequently coated with gold particles. The binder content is 40% and the titanium dioxide content is 4.5%.  

40.7 g of tetraethoxysilane (195.4 mmol) and 21.1 g of ethanol (pa) were mixed with 3.5 g of a 0.1 N solution of p-toluenesulfonic acid in water and the mixture was stirred for 1 hour. Then 4.0 g of tetrabutoxytitanium (11.75 mmol) were slowly added, the mixture was stirred for a further 30 minutes, a solution of 8.44 g of cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OH) ( CH ₃ ) ₂ ]} ₄ (13 mmol) in 20.0 g of ethanol (p. A.) added, stirred again for 30 minutes, while stirring with a mixture of 3.9 g of a 0.1 N solution of p- Toluene sulfonic acid in water and 3.9 g of ethanol (pa) are added and finally left to stand. The batch reaches the gel point after approx. 24 h. After an aging time of approx. 14 days, water was added to the gel until no more gas bubbles and streaks could be seen. The water is exchanged several times. The product was then heated in water at 60 ° C. for 1 hour, the supernatant solution was decanted off and the residue was dried at 150 ° C. for 8 hours.

The catalyst support obtained has a theoretical composition of 40 cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) ₂ (O _1/2 )]} ₄ , 55.6% SiO ₂ and 4, 5 % TiO ₂ .

To modify the surface, 20 g powder with 20 g were used under protective gas 1,1,1,3,3,3-hexamethyldisilazane in 200 g of dry n-hexane and under Stir under reflux for 2 hours. Then the supernatant Decanted solution, the residue washed 2 times with 300 ml of n-hexane, under Vacuum freed of volatile components and dried at 150 ° C for 4 hours.

The BET surface area is 345 m ² / g.

2.5 g of titanium-containing carrier were placed in 20 ml of methanol (Merck, pa), 40 mg of HAuCl ₄ × 3 H ₂ O (0.1 mmol, from Merck), dissolved in 5 ml of methanol, were mixed with 0.8 ml 2 N K ₂ CO ₃ adjusted to pH 8, stirred for 30 min, 2 ml of sodium citrate solution added, pH checked again, stirred for 120 min, solid separation, washed 3 × with 20 ml of methanol each, 10 h at 120 ° C. under normal pressure dried and calcined at 200 ° C for 5 h. The gold content of the gold-titanium silicon catalyst is 0.58% by weight (ICP analysis).

In a test according to the test instructions at constant PO selectivities of 95% over 50 h propene sales of 1.5% achieved.

Example 2

This example describes the preparation of a catalyst as in Example 1, consisting of a titanium-containing, organic-inorganic hybrid material, which surface modified and subsequently coated with gold particles. Before the The catalyst support was ground in noble metal.

For grinding, the titanium-containing material was suspended in isopropanol, in one Ball mill ground, the solvent removed on a rotary evaporator, the Powder dried for 4 hours at 150 ° C at normal pressure, then surface modified and covered with precious metal.

In a test according to the test specification (140 ° C) with constant PO-Selek activities of 95% over 50 h propene sales of 2.5% achieved. In a test according to the test specification at 150 ° C with constant PO selectivities of 95% 50 h propene sales of 3.4% achieved.

Example 3

This example describes the preparation of a catalyst consisting of a Titanium-containing, organic-inorganic hybrid material, which surface modes fected and subsequently coated with gold particles. The preparation was done analogous to Example 2, but the binder content is 20% and the titanium dioxide content is 3%.  

55.6 g of tetraethoxysilane (266.9 mmol) and 16.9 g of ethanol (pa) are mixed with 4.8 g of a 0.1 N solution of p-toluenesulfonic acid in water and the mixture is stirred for 1 hour. 2.65 g of tetrabutoxytitanium (7.78 mmol) are then slowly added, the mixture is stirred for a further 30 minutes, and a solution of 4.16 g of cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OH) ( CH ₃ ) ₂ ]} ₄ (6.4 mmol) in 10.0 g of ethanol (pa) added, stirred again for 30 minutes, while stirring with a mixture of 5.1 g of a 0.1 N solution of p-Toluenesulfonic acid in water and 5.1 g of ethanol (pa) are added and finally left to stand. The batch reaches the gel point after approx. 24 h. After an aging period of approx. 18 days, water is added to the gel until no more gas bubbles and streaks can be seen. The water is exchanged several times. The product is then heated in water at 60 ° C. for 1 hour, the supernatant solution is decanted off and the residue is dried at 150 ° C. for 8 hours. A yield of 21.9 g is obtained. The BET surface area is 118 m ² / g.

The catalyst support obtained has a theoretical composition of 20% cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) ₂ (O _1/2 )]} ₄ , 77% SiO ₂ and 3% TiO ₂ .

The catalyst support obtained is then surface-modified. To 10 g of product with 10 g of 1,1,1,3,3,3-hexamethyldisilazane in 100 g of dry n-hexane are introduced and refluxed with stirring for 2 hours heated. The supernatant solution is then decanted, the residue twice washed with 150 ml of n-hexane each, under vacuum of volatile constituents freed and dried at 150 ° C for 4 hours.

2.5 g of titanium-containing carrier were placed in 20 ml of methanol (Merck. Pa), 40 mg of HAuCl ₄ × 3 H ₂ O (0.1 mmol, Merck), dissolved in 5 ml of methanol, were added, with 0.8 ml 2 N K ₂ CO ₃ adjusted to pH 8, stirred for 30 min, 2 ml of sodium citrate solution added, pH checked again, stirred for 120 min, solid separation, washed 3 × with 20 ml of methanol each, 10 h at 120 ° C. under normal pressure dried and calcined at 200 ° C for 5 h. The gold content of the gold-titanium silicon catalyst is 0.55% by weight (ICP analysis).

In a test according to the test instructions at constant PO selectivities of 95% propene sales of 0.5% achieved over 50 h.

Example 4

This example describes the preparation of a catalyst consisting of a Titanium-containing, organic-inorganic hybrid material, which surface modes fected and subsequently coated with gold particles. The preparation was done Analogous to example 2, but the titanium dioxide content is 3%.

123.3 g of tetraethoxysilane (591.8 mmol) and 62.1 g of ethanol (pa) are mixed with 10.8 g of a 0.1 N solution of p-toluenesulfonic acid in water and the mixture is stirred for 1 hour. Then 7.95 g of tetrabutoxytitanium (23.3 mmol) are slowly added, the mixture is stirred for a further 30 minutes, a solution of 24.93 g of cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (OH) ( CH ₃ ) ₂ ]} ₄ (38.5 mmol) in 60.0 g of ethanol (pa) added, stirred again for 30 minutes, while stirring with a mixture of 11.4 g of a 0.1 N solution of p-Toluenesulfonic acid in water and 11.4 g of ethanol (pa) are added and finally left to stand. The batch reaches the gel point after approx. 24 h. After an aging period of approx. 10 days, water is added to the gel until no more gas bubbles and streaks can be seen. The water is exchanged several times. The product is then heated in water at 60 ° C. for 1 hour, the supernatant solution is decanted off and the residue is dried at 150 ° C. for 8 hours. A yield of 63.4 g is obtained.

The catalyst support obtained has a theoretical composition of 40 cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) ₂ (O _1/2 )]} ₄ , 57% SiO ₂ and 3% TiO ₂ .

The catalyst support is then surface modified. For this purpose, 25 g of product with 25 g of 1,1,1,3,3,3-hexamethyldisilazane in 250 g of dry n-hexane are placed in a protective gas and heated under reflux for 2 hours with stirring. The supernatant solution is then decanted off, the residue is washed twice with 400 ml each of n-hexane, freed of volatile constituents under vacuum and dried at 150 ° C. for 4 hours. The BET surface area is 264 m ² / g.

2.5 g of titanium-containing carrier were placed in 20 ml of methanol (Merck, pa), 40 mg of HAuCl ₄ × 3 H ₂ O (0.1 mmol, from Merck), dissolved in 5 ml of methanol, were mixed with 0.8 ml 2 N K ₂ CO ₃ adjusted to pH 8, stirred for 30 min, 2 ml of sodium citrate solution added, pH checked again, stirred for 120 min, solid separation, washed 3 × with 20 ml of methanol each, 10 h at 120 ° C. under normal pressure dried and calcined at 200 ° C for 5 h. The gold content of the gold-titanium silicon catalyst is 0.58% by weight (ICP analysis).

In a test according to the test instructions at constant PO selectivities of 95% over 50 h propene sales of 1.5% achieved.

Example 5

This example describes the preparation of an amorphous catalyst support, be standing from an organic-inorganic hybrid material and from the oxides of Silicon, titanium and tantalum, which has been surface modified and below was covered with gold particles.

The catalyst preparation is carried out analogously to Example 2, but 60 min after the addition of tetrabutoxytitanium, 2.4 g Ta (OEt) ₅ (6 mmol, Chempur, 99.9% strength) are added to the homogeneous batch, the mixture is stirred for 15 min and analogously to Example 2 mixed with a carbosilane crosslinker, gelled, worked up, modified and coated with gold.

In a test according to the test instructions at constant PO selectivities of 94% propene sales of 2.7% achieved over 50 h.

Example 6

This example describes the preparation of a catalyst consisting of a titanium-containing, organic-inorganic hybrid material, which surface modes fected and subsequently coated with silver particles. The catalyst production was carried out analogously to Example 2. Instead of using gold particles, the catalyst support is added Silver particles coated.

To dissolve 150 mg of silver nitrate (0.97 mmol; Merck) in 25 ml of methanol 2.5 g of titanium-containing catalyst support are added at room temperature with stirring. The suspension was stirred at RT for 1 h, the solid was separated off and mixed once with Washed 20 ml of methanol. The moist, white solid became 3 h at 120 ° C dried and then calcined in air for 2 hours at 150 ° C. and 5 hours at 200 ° C.

In a test according to the test instructions at constant PO selectivities of 94% achieved propene sales of 0.3% over 50 h.

Example 7

Trans-2-butene is used as an unsaturated hydrocarbon instead of propene puts. A catalyst consisting of is used for the partial oxidation of trans-2-butene an organic-inorganic hybrid material and from the oxides of silicon, Titanium and metallic gold are used. The catalyst preparation is carried out analogously Example 2.

In a test according to the test instructions, at constant 2,3-epoxybutane Selectivities of 91% over 50 h trans-2-butene conversions of 2.0% achieved.  

Example 8

Cyclohexene is emitted instead of propene as an unsaturated hydrocarbon chooses. A catalyst consisting of is used for the partial oxidation of cyclohexene an organic-inorganic hybrid material and from the oxides of silicon, Titanium and metallic gold are used. The catalyst preparation is carried out analogously Example 2. Cyclohexene is brought into the gas phase using an evaporator.

In a test according to the test instructions, selectivities for cyclohexene oxide of 90% over 50 h cyclohexene sales of 1.8% achieved.

Example 13

1,3-butadiene is emitted instead of propene as an unsaturated hydrocarbon chooses. A catalyst consisting of is used for the partial oxidation of 1,3-butadiene an organic-inorganic hybrid material and from the oxides of silicon, Titanium and metallic gold are used. The catalyst preparation is carried out analogously Example 2.

In a test according to the test instructions, butene oxide selectivities of 85% over 40 h butadiene sales of 0.6% achieved.

Example 14

Propane is used as a saturated hydrocarbon instead of propene. For partial oxidation of propane becomes a catalyst consisting of a organic-inorganic hybrid material and from the oxides of silicon, titanium and metallic gold used. The catalyst preparation is carried out analogously Example 2.  

In a test according to the test instructions, acetone selectivities of 80% Over 40 h of propane sales of 0.4% achieved.

Claims (14)

1. Supported compositions, characterized in that they contain gold and / or silver particles and titanium-containing, organically inorganic hybrid materials. 2. Supported compositions according to claim 1, characterized in that the organic-inorganic hybrid materials have at least one structural element of the formula (I)
[R ¹ ] _j -SiR ² _k (O _1/2 ) _4-kj (I)
on, where
j is 1, 2 or 3 and
k represents 0, 1 or 2 and
k + j ≦ 3
R ^{1 is} a C ₁ to C ₁₀ alkylene radical bridging Si atoms and
R ^{2 represents} an optionally substituted alkyl or aryl radical. 3. Supported compositions according to one or more of claims 1 to 2, characterized in that the organic-inorganic hybrid materials have at least one structural element of the formula (II)
[R ¹ ] _j -SiR ² _k (O _1/2 ) _4-kj (II)
on, where
j is 1,
k represents 0, 1 or 2 and
k + j ≦ 3
R ^{1 is} a C ₁ to C ₄ alkylene radical bridging Si atoms, and
R ^{2 is} a methyl or ethyl radical. 4. Supported compositions according to one or more of claims 1 to 3, characterized in that the organic-inorganic hybrid materials contain at least one of the following structural elements

• a) Si [(C ₂ H ₄ ) Si (CH ₃ ) Z (O _1/2 )] ₄
• b) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Sl (CH ₃ ) ₂ (O _1/2 )]} ₄
• c) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (CH ₃ ) (O _1/2 ) ₂ ]} ₄
• d) cyclo- {OSi (CH ₃ ) [(C ₂ H ₄ ) Si (O _1/2 ) ₃ ]} ₄

5. Supported compositions according to one or more of claims 1 to 4, characterized in that the organic-inorganic hybrid materials between 0.1 and 6% by weight of titanium and, if appropriate, others Foreign oxides, so-called promoters, contain. 6. Supported compositions according to one or more of claims 1 to 5, characterized in that they are between 0.00 and 4 wt .-% gold or between 0.01 and 8% by weight of silver or a mixture of gold and Silver included. 7. Supported compositions according to one or more of claims 1 to 6, characterized in that the surface has been modified. 8. Process for the preparation of the supported compositions according to Claims 1 to 7, characterized in that the titanium-containing, organic inorganic hybrid materials can be produced via sol-gel processes. 9. The method according to claim 8, characterized in that organic anor ganic binder, silicon, titanium and optionally promoter precursors are mixed.   10. The method according to claim 9, characterized in that the organic inorganic binders polyfunctional organosilanes with at least 2 are bridged by a C1 to C10 alkylene silicon atoms. 11. The method according to one or more of claims 8 to 10, characterized characterized in that the organic-inorganic hybrid materials surface be modified and / or coated with gold and / or silver particles be, the precious metal is on a nanometer scale. 12. Use of the composition according to one or more of the An Proverbs 1 to 7 as a catalyst for the selective oxidation of hydrocarbons fabrics. 13. Use according to claim 12, characterized in that propene Propene oxide is oxidized. 14. Process for the selective oxidation of hydrocarbons in the presence one or more supported compositions according to one or more reren of claims 1 to 7 and of molecular oxygen and water material.