EP2448661A2 - Catalyst-coated support, method for the production thereof, a reactor equipped therewith, and use thereof - Google Patents

Abstract

The invention relates to a catalyst-coated support containing a planar support, a primer layer composed of nanoparticles made of material containing silicon oxide, which primer layer is applied to the planar support, and at least one catalyst layer applied to the primer layer. The applied layers are characterized by an exceptionally good tensile adhesive strength and can be used exceptionally well in heterogeneously catalyzed gas-phase reactions, in particular in microreactors.

Description

 description

Catalyst-coated support, process for its preparation, a so

equipped reactor and its use

The present invention relates to a catalyst-coated support and a process for its preparation and a reactor containing this support

Supported catalysts are widely used in various fields of technology. In addition to catalysts which have been applied to finely divided support materials, catalyst layers already applied to flat supports have also been described.

DE 198 39 782 A1 describes metallic reaction tubes with catalytic coating. The coating is a multimetal oxide composition with molybdenum and bismuth, which is applied directly to the reaction tube. adhesion-promoting

Intermediate layers are omitted here.

DE 19904 692 A1 describes a structured adsorber system for removing low-concentration pollutants from process gases, waste air or ambient air. This comprises an adsorptively effective layer applied to a carrier and at least one catalyst layer; In this case, at least one adsorption layer in the phase of desorption is impressed on a time-varying temperature along the flow direction. Described is a metallic support having on the surface of an oxide adhesive layer on which the adsorbent or the catalyst has been applied. As a material for an oxide adhesive layer alumina is called. In DE 603 08 698 T2 a microchannel reactor with bound catalyst

described. One of the examples discloses a silica-coated aluminum plate. This coated surface is chemically modified with a solution of N, N-dimethylpropylamino-trimethoxysilane and used as a catalyst for the Michael addition of methyl vinyl ketone and nitroethane to 5-nitrohexan-2-one. The use of adhesion-enhancing layers is not described.

DE 695 23 684 T2 describes a catalyst for purifying exhaust gases. This consists of a support and two catalyst layers applied thereto.

Intermediate layers to improve adhesion are not disclosed.

From DE 10 2005 038 612 A1 is a process for the preparation of both sides

Catalyst-coated membranes known for use in electrochemical devices. In this case, two semi-finished products are produced by applying an ionomer layer to a support and then applying an anode catalyst layer or a cathode catalyst layer. After drying the catalyst layers, the respective carriers are removed and the two ionomer layers are bonded together to form a membrane having an anode and a cathode catalyst layer.

DE 10 2005 019 000 A1 describes catalytically coated supports with porous catalyst layers containing cavities. These are characterized by high adhesive tensile strengths. This document also describes the possibility of using a primer layer between substrate and catalyst layer; Their thickness is typically 100 nm to 80 μm and the layer is made up of materials which do not have single structures of more than 5 μm in diameter. Further details on the nature of this primer layer can not be found in the document.

EP 0 246 413 A1 describes a plate-shaped catalyst for reducing the nitrogen oxides in flue gases. To improve the adhesion between the carrier plate and the catalyst mass, an intermediate layer of ceramic material is provided, which has been applied by plasma spraying or by flame spraying. When The only example of a ceramic material is mentioned in this document titania.

DE 10 2004 048 974 A1 discloses an oxidation catalyst for the removal of pollutants from oxygen-rich exhaust gases and a process for its preparation. The catalyst contains tin oxide, palladium and a carrier oxide, wherein the carrier oxide is present in nanoparticulate form. It is therefore a catalyst comprising selected active materials which are supported on a nanoparticulate oxide. Molded articles can be produced from these supported catalysts, for example, or the supported catalysts can be used for coating honeycomb bodies. Among other things, the nanoparticulate oxide can contain silicon and can be produced, inter alia, by flame pyrolysis. An application of the catalytically active materials to a provided with a primer layer support is not disclosed.

It is known that it is advantageous to improve the adhesion of organic coatings, for example paints, by plasma spraying, in particular silicon oxide layers applied by flame spraying. Such methods are for example as a CCVD method ( "combustion chemical vapor deposition") are known. One example is the Pyrosil ^® process, which is already commercially used for the production of contingent liabilities better surfaces.

In the field of dental prosthetics, methods for the production of metal-plastic composites are known. For example, DE Patent No. 34 03 894 describes the production of a metal-plastic composite according to the so-called "silicoater process." A thin, glassy SiO _x -C layer is applied to a sandblasted metal surface by means of flame hydrolysis burners an activated adhesive silane is applied, the surface thus formed is sealed with an opaque layer and then a plastic is applied to this layer, a further process for the production of metal-plastic composites is known from DE 42 25 106 A1, in which on a metallic Part is formed an adhesion-promoting oxide layer, which is then covered with a plastic over an intermediate layer of a Adhesive silane is connected. The adhesion-promoting oxide layer is produced by decomposition of a silicon or organometallic compound in a spark gap.

Starting from this prior art, it is an object of the present invention to provide a catalyst-coated carrier, which is characterized by excellent adhesion of the catalyst layers.

Furthermore, with the invention, an easy to be performed method for

Coating of sheet carriers with catalysts provided that works with easily accessible and inexpensive materials and thus is economically advantageous.

Surprisingly, it has now been found that primer layers of oxide silicon nanoparticles are excellent for improving the adhesion of

Catalyst layers on flat supports are suitable. These primer layers can be applied by conventional CCVD methods.

The present invention relates to a catalyst-coated carrier comprising a flat carrier, a primer layer of nanoparticles of silicon oxide-containing material applied thereto and at least one catalyst layer applied to the primer layer.

In the context of the present description, "flat carrier" is understood to mean a carrier which has one or more surfaces of at least 1 mm ² surface area. In contrast to finely divided carriers, surface carriers are therefore characterized by the presence of at least one surface with macroscopic dimensions They can be, for example, pipes, plates or other structures which can form reactor walls or reactor internals the catalyst layers are applied. The planar support is preferably made of metallic or ceramic

Materials. For example, the flat carrier may consist of an aluminum, iron, copper or nickel-containing metal or of a metal alloy; or this may consist of ceramics, such as aluminum, titanium or silicon oxide, silicon carbide or cordierite.

The surface of the flat carrier can be arbitrary. In addition to smooth, roughened or porous surfaces can be used. The surface may consist of the material of the carrier or have an oxide layer.

Preferably, the surface of the sheet carrier is smooth and the sheet carrier is rolled or stamped or pressed. In addition, flat carriers with milled surface are preferably used. According to the invention, an adhesion-promoting layer made of a material containing selected silicon oxide is applied to at least one of the surfaces of the planar support. Typical thicknesses of this adhesion-promoting layer are less than 100 nm, preferably 20 to 100 nm, very particularly preferably 30 to 50 nm. The adhesion-promoting layer is composed essentially of nanoparticulate particles. These may occur as disjoint units on the surface as single particles or in the form of aggregates on the surface, or these particles form a continuous layer of nanoparticulate particles. The shape and size of the individual nanoparticulate particles can vary widely. In addition to round or rotationally symmetric particles and irregular particle shapes are possible. The diameter of the particles typically ranges from 5 to 50 nm. The adhesion-promoting layer thus exhibits a largely homogeneous matrix in the micrometer range. The silica-containing materials which form the base material of the adhesion-promoting layer may have different chemical compositions. This layer may be hydrophobic or hydrophilic. The synthesis of the adhesion-promoting layer-forming compounds can be carried out by decomposition of organic or inorganic silicon compounds in thermal or non-thermal plasma. It is also possible to pyrolyze layers of hydrophobic inorganic aerogels in the presence of oxygen, as described, for example, in WO-A-96 / 26,890. Furthermore, silicate layers can also be applied to the planar support by introducing vapors or aerosols of silicon compounds into an oven which contains the support to be coated in a preferably inert atmosphere, wherein a silicon-containing layer is deposited on the support. This method is described in DE 10 2006 046 553 A1. In addition, as the materials for constituting the adhesion promoting layer, carbon particles-containing SiO 2 aerogels may be used. These are described, for example, in DE 43 00 598 A1. The adhesion-promoting layer is particularly preferred by plasma spraying, in particular by flame spraying, of silicon compounds in oxidizing

Atmosphere applied to the sheet carrier.

As silicon compounds, which can be used in particular in flame or plasma spraying, any Silizumverbindungen be used, provided that they can be sprayed into a flame or a plasma. In addition to silicon aerogels, preferably pyrolyzable silicon compounds are used.

Particularly preferred are soluble in water or organic solvents

Silicon compounds or vaporizable at flame or plasma temperatures silicon compounds used. These include in particular silicon-hydrogen compounds, silicon-carbon compounds or water-soluble silicates.

Examples of silicon-hydrogen compounds are silanes, such as compounds of the formula SiaH ₂ a-b + 2Rb, wherein R is a monovalent organic radical or a halogen atom. A is an integer of 1 to 20 and b is an integer of 0 to 19 , Examples of silicon-carbon compounds are organosilanes, such as compounds of the formula Si _a R ^' 2 _{a + 2} , wherein R ^' can have different meanings within a molecule and is a monovalent organic radical, preferably an alkyl and / or an alkoxy group, and a is an integer from 1 to 20.

Examples of water-soluble silicates are water glasses, for example sodium, ammonium or potassium waterglass.

Devices for plasma spraying or for flame spraying are known and commercially available. Devices for producing non-thermal plasmas, microwave plasma generators, and thermal plasmas,

For example, flames are used. The process can be carried out within and preferably outside the plasma source. The silicon compounds are introduced into the plasma, preferably in the form of a flame, for example in the form of an atomized liquid or in vapor form. The plasma or flame spraying is preferably carried out in an oxidizing atmosphere, in particular in air. Under these conditions, the pyrolyzable silicon compound decomposes to form silica-containing products which precipitate in the form of nanoparticles or aggregates of nanoparticles on the surface of the sheet carrier. By applying a nanoparticulate surface layer of silicon oxide, surface silicization is achieved. This can be achieved by the above-described feeding of an organosilicon compound into a flame. By this treatment, a thin, but very dense and adherent silicon oxide layer with high surface energy is generated on the support surface. This layer adheres to virtually all surfaces and forms a nanoporous surface structure, on the one hand a better mechanical

Anchoring the subsequently applied layers and on the other hand ensures an optimal chemical bonding of components of the subsequent layers to the silicate layer. By additional coating of the nanoporous silicon oxide layer with adhesion promoters, a further improvement of the catalyst layer can be achieved. For the flame spraying, a butane or propane gas or a mixture of the two gases together with a silane and / or a silane-carbon compound can be used as the pyrolysis gas. Thus, the silane and / or the silane-carbon compound can be fed into a propane-butane gas flame. In the reducing part of the flame, in the nuclear flame, the hydrocarbons as well as the silane and / or the silane-carbon compound are burned. In the oxidizing outer part of the flame, the resulting silane fragments are deposited on the surface as a high-energy silicate layer. This is the surface to be coated

preferably treated with the oxidizing part of the flame for a short time and under constant movement of the burner.

Thickness and structure of the resulting primer layer can be determined by the person skilled in the art

Adjustment of process parameters, such as distance of the flame or the plasma from the surface, as well as the treatment time or the concentration of the pyrolyzable material in the flame or the plasma can be adjusted.

The primer layer applied according to the invention contains as the base material silicon oxide, preferably a material of the formula SiO _x , where x is a rational number of less than or equal to 2, in particular between 1 and 2. In addition to silicon and oxygen, the primer layer may contain other elements, for example halogen, nitrogen, carbon or metals, such as alkali metals in the form of alkali metal ions.

At least one layer of catalytically active material is applied to the primer layer; this preferably has pores, in particular structures with a diameter of more than 1 micron. Besides micropores with diameters of less than 1 μm, this layer also contains macropores with diameters of at least 1 μm.

The catalyst layer typically contains structures due to particles larger than 1 μm in diameter; In this case, the catalyst layer is composed of catalytically active material and optionally further, inert material together. Several catalytic active layers can also be applied to the primer layer.

Particularly preferably, the porous catalyst layer contains cavities. Among cavities are in the present description irregular cavities with

Dimensions greater than 5 μm in at least two dimensions or with

Cross-sectional areas of at least 10 microns ² understood.

These cavities in these preferred catalyst layers are substantially closed and connected essentially only by pores with diameters of less than 5 microns or cracks with a width of less than 5 microns with the layer surface or other cavities. Cavities can be observed in SEM microscopic

Recognize cross sections of resin impregnated catalyst layers. The determination of the cross-sectional area or the dimensions can be carried out by methods known per se, for example by quantitative microscopy. In the context of this description, irregular voids are understood to mean cavities with ashpary and / or acylindrical geometry that deviates greatly from the ideal spherical and / or cylindrical shape, whose inner surface consists of local roughnesses and macropores. In contrast to cracks, cavities have no clear preferred direction.

Cavities are a component of the pore system of these preferred catalyst layers. They are particularly large macropores. Macropores are pores with a diameter greater than 50 nm in the sense of the IUPAC definition.

The presence of cavities in the catalyst layer again gives the coated carrier an additional increase in the adhesive tensile strengths, even after mechanical or thermal stress. In addition to the cavities, the catalyst layer preferably used according to the invention preferably has further macropores of smaller diameter in a high proportion. In a particularly preferred embodiment, the catalyst layer contains a pore system in which at least 50%, preferably at least 70% of the

Pore volume are formed by macropores having a diameter of at least 50 nm. Pore volume is understood to mean the volume detectable by means of mercury porosimetry according to DIN 66133 in pores having a diameter of greater than 4 nm. It assumes a contact angle of 140 ° and a surface tension of 480 mN / m for mercury. Before the measurement, the sample is dried at 105 ° C. The proportion of pore volume in macropores is also with

Mercury porosimetry determined.

The combined pore and cavity volume of the preferred catalyst layer which can be determined by saturating water absorption and differential weighing is typically from 30 to 95%, preferably from 50 to 90%, based on the total volume of the layer.

The thickness of the catalyst layer or catalyst layers is not particularly limited. Typically, the thickness of the porous catalyst layers is selected so that reactants can diffuse under the reaction conditions from the outer surface of the catalyst layer to the support substrate; preferably, these are thicknesses of up to 3 mm, for example between 50 μm and 2.5 mm, preferably between 100 μm and 1.5 mm. Thick catalyst layers ensure the best possible utilization of the catalyst per unit area of the coated surface.

The catalytic materials can be widely chosen. Of particular interest are catalyst systems for strongly exo- or endothermic reactions, especially for oxidation reactions. They are e.g. as basic systems to be varied with promoters:

Metal catalysts, such as stainless steel, molybdenum or tungsten catalysts, Noble metal catalysts, such as platinum, palladium, rhodium, rhenium, gold and / or silver catalysts, which may be supported, for example, on ceramic or activated carbon,

 Multimetal oxide catalysts which, as the main body, in addition to further dopants comprise a selection of the oxides of molybdenum, bismuth, vanadium, tungsten,

Phosphors, Antimons, iron, nickel, cobalt and copper exist

 Zeolite catalysts, e.g. Molecular sieves based on titanium-containing

Molecular sieves of the general formula (SiO ₂ ) i- _x (TiO 2) χ, such as titanium silicalite-1 (TS1) with MFI crystal structure, titanium silicalite-2 (TS-2) with MEL crystal structure, titanium-beta zeolite with BEA crystal structure and titanium silicalite-48 having the crystal structure of

Zeolite ZSM 48.

 - Fischer-Tropsch catalysts, in particular based on Co or Fe

 - Fe, Ni, Co or Cu based catalysts

 - Solid bases or acids

 - mixtures of these systems

The following catalyst systems are particularly preferably used:

 - titanium silicalite-1

 - Pd, Au and potassium acetate on an oxidic support, preferably on an oxide with a high silica content

 - Mixtures of oxides and mixed oxides of Mo, Bi, Fe, Co, Ni and

 optionally further admixtures, e.g. K

 Mixtures of the oxides and mixed oxides of Mo, V, Cu, W and optionally other admixtures, e.g. Sb, Nb

 Ag on an alumina, which is preferably at least partially in the alpha phase, and optionally further admixtures such as e.g. Cs, Re

 - Vanadium pyrophosphates and optionally further admixtures

 Pd and / or Pt optionally combined with tin on alumina

The catalytically active materials may be in an inert or supporting matrix of inorganic oxides or thermostable plastics. Preferred materials of this matrix are oxides of Si, Al, Ti, Zr and / or mixtures thereof.

In addition, in each case further doping elements and other Beikomponenten common for the preparation of catalyst layers may be included. Examples of such materials are alkali and alkaline earth compounds.

Particularly preferably, the catalytically active layers contain, in addition to the catalytically active material, binders of oxygen compounds of silicon, in particular of silicate material. These binders together with the material of the

Primer layer particularly high adhesive tensile strengths.

As catalyst materials it is possible to use all catalysts which can be used for the intended reaction.

The coated according to the invention carriers can be used for a variety of heterogeneously catalyzed reactions in the liquid phase and in particular in the gas phase. Examples of reactions are oxidation, hydrogenation or ammoxidation reactions, such as the catalytic oxidation of olefins, preferably the catalytic epoxidation of olefins, the catalytic oxidation of olefins to aldehydes and / or

Carboxylic acids, the catalytic hydrogenation of organic compounds or the complete or partial oxidation of a hydrocarbon-containing gas mixture, in particular the synthesis gas, the oxidative dehydrogenation of

Hydrocarbons or the oxidative coupling of hydrocarbons.

Examples of the epoxidation of ethylenically unsaturated compounds are the

Oxidation of propene to propene oxide or from ethylene to ethylene oxide; Examples of the oxidative coupling of hydrocarbons is the coupling of acetic acid and

Ethylene to vinyl acetate; Examples of oxidation reactions are the oxidation of ethane to acetic acid or the oxidation of propene to acrolein or acrylic acid. Further Examples of reactions are hydrogenation reactions, for example the

Selective hydrogenation of unsaturated organic compounds.

The invention also relates to the use of the catalytically coated carrier for these purposes.

Examples of catalytically active materials which may be contained in the catalyst layer are catalytically active metals, semimetals including

Alloys, oxide materials, sulfidic materials and siliceous materials.

The supported catalyst layer systems of the invention have high

Adhesive tensile strength on. Typically, these layer systems show

Adhesive tensile strengths of> 1 kPa (measured in accordance with DIN EN ISO 4624), in particular> 10 kPa and especially> 50 kPa.

Particular preference is given to flat supports with a catalytic coating, a thickness of the catalytically active layer of> 50 μm, preferably 50 μm to 2.5 mm, very particularly preferably 100 μm to 1.5 mm and an adhesive tensile strength of the layer of> 10 kPa.

The catalytic coating support of the invention can be prepared by a particularly simple and economical process. This is also the subject of the present invention. The invention therefore also relates to a process for the preparation of a catalyst-coated carrier with the measures:

 i) coating at least one surface of a planar support with a primer layer of nanoparticles of silicon oxide-containing material, by

 ii) at least one silicon compound in an oxidizing atmosphere in

Presence of a thermal or non-thermal plasma is applied to the surface of the sheet carrier, and iii) at least one layer containing catalytically active constituents or precursors thereof is applied to the support provided with the primer layer. Particularly preferably, the coating of the planar support with the primer layer takes place by plasma spraying, in particular by flame spraying, of silicon-hydrogen compounds, silicon-carbon compounds or aqueous solutions of water-soluble silicates in an oxidizing atmosphere. Very particular preference is given to using silanes and / or silane-carbon compounds as the silicon compound.

The flame or plasma temperature during flame or plasma spraying is chosen so that the pyrolyzable silicon compound decomposes under the conditions of application. Typically, temperatures of at least 500 ⁰ C are used, preferably between 500 ° C and 2000 ⁰ C.

Commercially available one- or two-substance nozzles can be used for flame spraying, wherein the nozzle is supplied with a combustible mixture and the silicon compound. As a combustible mixture, for example, a mixture of hydrocarbons and air, for example, a propane-air mixture can be used. The pyrolyzable silicon compound is injected into the flame or it is already contained in the combustible mixture. The leadership of the flame over the

Surface can be done manually or preferably automated. In the

automated procedure, it is advisable to move the nozzle computer-controlled on the surface to be sprayed and thereby monitor the order of the material and other process parameters targeted and adjust.

The spraying of the primer layer can be carried out in a manner known per se, wherein a variety of process parameters are available to the person skilled in the art. Examples are the injection pressure, the spray distance, the spray angle, the feed rate of the spray nozzle or fixed nozzle of the substrate, the Nozzle diameter, the material flow rate, the geometry of the spray jet, the flame temperature and the concentration of the pyrolyzable Silizumverbindung in the flame. As an alternative to a flame, the sputtering of the pyrolyzable silicon compound can also take place in another plasma, which can be generated, for example, by microwaves.

The application of the catalytically active layer (s) can by known per se

Procedure, for example by knife coating, brushing or in particular by spraying.

Preferably, a suspension having at least 40% by weight solids _content comprising particles of catalytically active material having an average diameter (D 5O) of at least 5 μm and / or its precursor and optionally further constituents of catalytically active layers is sprayed, this step being or repeated several times.

In a further preferred embodiment, the particles of the suspension have a rough surface and an irregular shape, as arises, for example, by grinding or breaking.

In a further preferred embodiment, a binder is added to the suspension. Suitable binders are, in particular, sols, very finely divided suspensions or solutions of the oxides of Al, Si, Ti, Zr or mixtures thereof, most preferably sols or solutions of silicon oxides.

In a further variant of the method according to the invention, a suspension having at least 40% by weight solids content comprising particles of inert material having an average diameter (D 50 value) of at least 5 μm and optionally further constituents of catalytically active layers is sprayed on, this step on or can be repeated several times. Subsequently, the layer system is after its preparation impregnated with a catalytically active material and / or its precursor.

After application of the individual layers or of the entire layer system or parts thereof, these may optionally be dried and / or calcined before further treatment of the layers takes place.

With a calcination, for example at a temperature of 250 to 1200 ° C, organic or other decomposable residues can be removed. The pretreatment may consist of a sequentially variable combination of these individual methods.

The applied catalyst suspension contains at least one or more catalytically active materials or their precursors.

Precursors may be, for example, nitrates, oxalates, carbonates, acetates or other salts which can be converted into oxides by thermal or oxidative decomposition, for example. The catalytically active materials or their precursors can be present in molecular, colloidal, crystalline or / and amorphous form. The actual catalytic materials, or their precursors, may be contained in the suspension or later applied by impregnation. To adjust the pH, acids or bases can be added. Furthermore, organic constituents, such as surfactants, binders or pore formers may be included. As a suspension or solvent is particularly suitable water. But it can also be used organic liquids. This suspension to be applied can be applied by spraying or spraying. Non-wetting parts can be covered or taped. For spraying commercially available one- or two-fluid nozzles can be used, the beam can be done manually or preferably automated. In the automated procedure, it is advisable to move the nozzle computer-controlled on the surface to be sprayed and thereby monitor the order of the material and other process parameters targeted and set.

The spraying of the individual layers can take place in a manner known per se, the skilled person being able to use a large number of process parameters. Examples of this are the injection pressure, the spray distance, the spray angle, the feed rate of the spray nozzle or, if the spray nozzle of the substrate is stationary, the nozzle diameter, the material flow rate and the geometry of the spray jet.

Furthermore, the properties of the suspensions to be sprayed exert an influence on the quality of the resulting layers, for example density, dynamic viscosity, surface tension and zeta potential of the suspension used.

For the preparation of the coated carrier according to the invention, a layered application can take place, which is preferably repeated one or more times.

After applying the respective layer, one or two thermal

Treatments for drying and calcination follow. If the applied layer is not already dried, a separate drying, for example, at

Temperatures of 20-200 ⁰ C, or a drying in combination with a calcination, for example at temperatures of 200-1000 ⁰ C, carried out. The drying and the calcination can be carried out in an oxidizing atmosphere, for example in air, or in an inert atmosphere, for example in nitrogen.

It is also possible first to apply all layers and then to dry and calcine the layer system. When spraying several layers containing catalytically active material, they may have the same composition, so it is always the same second suspension used. But it can also contain layers containing catalytically active Material produced with different composition or some layers of inert material.

In order to smooth the applied layers, the surface of the produced can

Layered ground system or milled with CNC machines, for example. Preferably, as far as the application of the individual layers, it is possible to produce as-plane layers with a low tolerance of the total layer thickness of less than ± 25 μm, so that no further processing is necessary. After drying or calcining, further catalytic components or their precursors may optionally be applied by impregnation. For reasons of safety at work and economy, it is generally recommended to carry out such impregnation only after any mechanical final treatment. For this purpose, the carrier layer is coated with the solution or suspension containing the components or immersed in them or sprayed. After impregnation drying and / or calcination can be connected.

The coated according to the invention supports can be used in a variety of reactors, for example in plate or tubular reactors.

A further subject of the invention is a reactor containing at least one of the carriers according to the invention with catalytic coating. The supports according to the invention are preferably used in wall reactors, which also include microreactors. For the purposes of this description, microreactors are to be understood as meaning reactors in which at least one of the

Dimensions of the reaction space or the reaction spaces is less than 10 mm, preferably less than 1 mm, more preferably less than 0.5 mm.

Wall reactors and in particular microreactors have a plurality of reaction spaces, preferably a plurality of reaction spaces running parallel to one another. The dimensioning of the reaction spaces can be arbitrary, provided at least one dimension moves in the range of less than 10 mm. The reaction spaces may have round, ellipsoidal, triangular or polygonal, in particular rectangular or square cross sections. Preferably, the or a dimension of the cross section is smaller than 10 mm, that is at least one side length or the or a diameter. In a particularly preferred embodiment, the cross section is rectangular or round and only one dimension of the cross section, ie a side length or the

Diameter moves in the range of less than 10 mm.

The material enclosing the reaction space may be arbitrary provided that it is stable under the reaction conditions, sufficient heat removal is permitted and the surface of the reaction space is completely or partially coated with the layer system according to the invention containing catalytically active material.

The present invention thus also relates to a reactor which can be used in particular for the heterogeneously catalyzed gas phase reaction, wherein:

 a) at least one reaction space is present, of which at least one dimension is smaller than 10 mm, and

 b) the surface of the reaction space is coated or partially coated with the above-defined layer system of primer layer and layer (s) containing catalytically active material.

A preferred microreactor is characterized by having a plurality of vertically or horizontally and parallelly arranged spaces having at least one lead and one lead each, the spaces being formed by stacked plates or layers, and a part of the spaces being reaction spaces, of which at least one dimension moves in the range of less than 10 mm, and the other part of the spaces is heat transport spaces, the Supply lines to the reaction chambers are connected to at least two distributor units and the discharge lines from the reaction chambers are connected to at least one collection unit, the heat transfer between reaction and heat transport spaces being effected by at least one common room wall, which is formed by a common plate.

A microreactor of this type which is used with particular preference has spacer elements arranged in all chambers and contains at least partially applied to the inner walls of the reaction spaces by the process according to the invention

Catalyst material, has a hydraulic diameter, which is defined as the quotient of four times the surface to the circumferential length of the free flow cross section, in the reaction chambers less than 4000 .mu.m, preferably less than 1500 .mu.m, and more preferably less than 500 .mu.m, and a ratio between the perpendicular smallest distance between two adjacent spacer elements to the slot height of the reaction space after a coating with catalyst of less than 800 and greater than or equal to 10, preferably less than 450 and more preferably less than 100.

Yet another object of the invention is the use of the described carriers in a reactor for reacting organic compounds. These may be reactions in the gas phase, in the liquid phase or in the phase with supercritical state.

The invention will be described in more detail by examples. A limitation is not intended thereby.

Examples 1 - 4:? Preparation of coated nanoparticulate SiO layers Katalvsatorträgern platelets Hastalloy C-22 with dimensions of 40x50 mm were used in a flame spray system, which worked after the Pyrosil ^® process, provided ₂ layer having a nanoparticulate SiO. The flame pyrolysis became propane gas used, to which a small amount of an organosilicon compound (optionally tetramethylsilane or hexamethyldisiloxane) had been added. The coating of the samples was carried out by repeatedly flaming the platelet surface and by varying the distance between flame and platelet surface. The distance between the burner tip and platelet surface was considered as the distance. Before coating, the platelet surface was created by milling.

For Example 1, the plate surface was passed six times in succession at a distance of 10 mm from the flame.

For Example 2, the plate surface was passed six times in succession at a distance of 40 mm from the flame.

For example 3, the platelet surface was passed twelve times in succession at a distance of 10 mm from the flame.

For example 4, the platelet surface was passed twelve times in succession at a distance of 40 mm from the flame. The wettability of the surfaces produced in this way was checked by contact angle measurements. The contact angle measurements were made with a

Contact angle measuring system G2 (KRÜSS GmbH, Scientific Instrumentation Hamburg) performed. To determine the contact angle, the method of the lying drop was used. The measuring method used was the static contact angle measurement. In this case, a drop of liquid was deionized water of 2 to 6 mm diameter deposited on the surface of the catalyst plate and the

Contact angle over a longer period again and again determined. Within the applied diameter range, the contact angle to be measured is independent of the diameter of the drop. The contact angle was immediately after

Applying the drop via a video system coupled to the contact angle measuring system which records the profile of the applied liquid drop, measured during a period up to about 20 s. Of the eight readings obtained, the arithmetic mean was calculated.

As Comparative Example V1, a rolled plate surface of Hostalloy, 40x50 mm, was used.

The results of the contact angle measurements after different storage periods are given in the following table. table

Examples 5-8: Preparation of Catalyst Coated Samples

Platelets made of Hastalloy C-22 with dimensions of 45x10x2 mm were coated with nanoparticulate SiO 2 layers by flame spraying analogously to Examples 1-4. Thereafter, each catalyst layer was sprayed onto this plate. The catalyst coated samples corresponded to Examples 5-8.

The catalyst used was a bentonite catalyst prepared with Pd and Au. For this purpose, a catalyst suspension consisting of 8.5 g of catalyst powder, 3.75 g of binder (Köstrosol 2040 AS) and 7.75 g of water was prepared. The coupons were sprayed with a HS25 HVLP handgun has been. The nozzle diameter was 1, 8 mm, the injection pressure was 1, 1 bar, the spray distance 20 cm and the feed 10 cm / sec.

As Comparative Example C2, an untreated Hastalloy sample was coated with catalyst under the conditions mentioned above.

To characterize the composite stability, a three-point microbend test was performed. For this purpose, the sample plates were placed at their ends (free

 Distance: 40 mm) and in the middle a pressure fin was put on. The bending load was up to 2000 N and the pressure fin was at a speed of 20 microns / sec. emotional. The deflections of the test piece were determined, in which the first crack formed in the catalyst layer and in which the

 Base material stood out. In addition, an adhesive tensile strength measurement according to DIN EN ISO 4624 was performed. The results of these experiments are listed in Table 2 below.

Claims

claims

A catalyst-coated carrier comprising a flat carrier, a primer layer of nanoparticles of silicon oxide-containing material applied thereto and at least one applied to the primer layer

 Catalyst layer.

2. Catalyst-coated carrier according to claim 1, characterized in that the primer layer is applied by plasma spraying, preferably by flame spraying of silicon compounds in an oxidizing atmosphere layer.

3. Catalyst-coated carrier according to claim 2, characterized in that the silicon compounds are silicon-hydrogen compounds, silicon-carbon compounds or water-soluble silicates.

4. Catalyst-coated carrier according to one of claims 1 to 3, characterized

 in that the flat support is made of metal or of ceramic, preferably of steel, aluminum, copper or nickel, or of aluminum, titanium or silicon dioxide, of zirconium dioxide, of silicon carbide or of cordierite.

5. Catalyst-coated carrier according to one of claims 1 to 4, characterized

 in that the planar carrier is designed in the form of a plate, a tube, a reactor wall or a reactor installation.

6. Catalyst-coated carrier according to one of claims 1 to 5, characterized

 in that the surface of the flat carrier is milled, rolled, punched or pressed.

7. A catalyst-coated carrier according to any one of claims 1 to 6, characterized

in that the primer layer has a thickness of 20 to 100 nm, preferably of 30 to 50 nm.

A catalyst-coated carrier according to any one of claims 1 to 7, characterized in that the silica-containing material is SiO _x , wherein x is a rational number of less than or equal to 2.

9. A catalyst-coated carrier according to any one of claims 1 to 8, characterized

 characterized in that the catalyst layer is porous and has a thickness such that reactants can diffuse from the surface to the support substrate, preferably has a thickness of up to 3 mm.

10. Catalyst-coated carrier according to claim 9, characterized in that the catalyst layer contains cavities containing irregular cavities

Dimensions of greater than 5 microns in at least two dimensions or with cross-sectional areas of at least 10 microns ² are.

A catalyst-coated carrier according to claim 10, characterized in that the catalyst layer comprises a pore system in which at least 50%, preferably at least 70%, of the pore volume is formed by macropores having a diameter of at least 50 nm.

12. A process for the preparation of a catalyst-coated carrier with the

 Activities:

 i) coating at least one surface of a planar support with a primer layer of nanoparticles of silicon oxide-containing material, by

 ii) at least one silicon compound in an oxidizing atmosphere in

 Presence of a thermal or non-thermal plasma is applied to the surface of the sheet carrier, and

iii) at least one layer containing catalytically active constituents or precursors thereof is applied to the support provided with the primer layer.

13. The method according to claim 12, characterized in that the coating of the flat carrier with the primer layer by flame spraying of silicon hydrogen compounds, silicon-carbon compounds or aqueous solutions of water-soluble silicates takes place in an oxidizing atmosphere.

14. The method according to claim 12, characterized in that silanes and / or silane-carbon compounds are used as silicon compounds.

15. The method according to any one of claims 12 to 14, characterized in that the flame or plasma temperature during flame or plasma spraying at least

500 ⁰ C is preferably from 500 ⁰ C to 2000 ° C.

16. The method according to any one of claims 12 to 15, characterized in that the application of the layer containing catalytically active constituents or precursors thereof by spraying a suspension of particles of catalytically active

Ingredients or precursors thereof containing at least 30% by weight

 Solids content is carried out and that this step is optionally repeated once or several times.

17. The method according to any one of claims 12 to 15, characterized in that the application of the layer containing catalytically active constituents or precursors thereof by spraying a suspension of particles of inert and / or catalytically active ingredients containing at least 30 wt.% Solids content takes place this step is optionally repeated one or more times and that the layer system after its preparation with catalytically active material or a precursor thereof is impregnated.

18. Reactor comprising at least one catalyst-coated carrier according to one of claims 1 to 11.

19. A reactor according to claim 18, characterized in that the reactor a

Microreactor is.

20. Reactor according to claim 19, characterized in that it can be used for the heterogeneously catalyzed gas phase reaction and at least one

 Reaction space, of which at least one dimension is smaller than 10 mm, wherein at least one surface of the reaction space consists of a coated support according to one of claims 1 to 11.

21. Reactor according to claim 20, characterized in that the coated carrier has the form of a tube, a plate, a reactor wall or a reactor installation.

22. Use of a catalyst-coated carrier according to any one of claims 1 to 11 in processes for the catalytic oxidation of olefins, preferably for katalytisphen epoxidation of olefins, for the catalytic oxidation of olefins to aldehydes and / or carboxylic acids, for the catalytic hydrogenation of

 organic compounds or for the complete or partial oxidation of a hydrocarbon-containing gas mixture, in particular for the production of synthesis gas, for the oxidative dehydrogenation of hydrocarbons or for the oxidative coupling of hydrocarbons.

23. Use according to claim 22, characterized in that the complete oxidation of hydrocarbon-containing gas mixtures is used in a process for the purification of combustion or process gases.