HK1118247B - Catalyst-coated support, method for producing the same, reactor comprising the same and use thereof - Google Patents

Description

Catalytically coated support, method for the production thereof, and reactor comprising the same and use thereof

Technical Field

The present invention relates to a supported catalyst layer with good adhesive strength and high flatness and low layer thickness tolerance (Toleranz), a process for its preparation, its use in heterogeneously catalyzed processes, and a reactor containing this catalyst layer.

Background

Many chemical reactions are carried out in heterogeneous catalytic mode in a wide variety of reactors. Reactors equipped with catalytic layers have been known for a long time.

DE7640618U discloses a method for the catalytic purification of exhaust gases, in which a metal tube is used, which is formed in a turbulent flow and is lined with a catalyst material. In addition to the direct application of the catalyst from the liquid or gas phase, porous layers applied by impregnation with catalytically active material inside the metal tube are also disclosed. This publication also suggests first applying a strongly adherent layer, such as alpha-alumina, on the metal tube and then or together with the strongly adherent layer placing the catalyst directly.

DE19839782a1 discloses metal reaction tubes with a catalytic coating comprising a multi-metal oxide material, which can be used in a catalytic gas phase reaction. The catalytic layer is applied directly to the metal reaction tube in the form of a solution, emulsion or dispersion without an adhesion-promoting intermediate layer. This can be done by spraying or dipping. Typical layer thicknesses range from 10 to 1000 microns. To produce thick layers, multiple coating of the reaction tubes is recommended.

DE19959973a1 discloses a method for producing arrays of heterogeneous catalysts, which are composed of shaped bodies having continuous channels with different catalysts applied therein. This method is reported to broaden the range of known arrays. The method can be automated.

It is known to impregnate a metal or ceramic honeycomb for coating in a suspension of a Washcoat (Washcoat) to apply a planar catalyst layer. Here, the catalytic component is already present in the primer sealer or is subsequently applied by dipping. Followed by drying, calcination and optionally reduction. This method is disclosed, for example, in the Catal. Rev., 2001, 43, 345-.

DE69906741T2 discloses a porous diesel exhaust gas filter, in which a through-flow filter body with a honeycomb wall structure is used, the surface of which is coated with a catalytically active material. The surface area enhanced coating is applied to the filter body by coating with a washcoat, for example by applying a sol containing small colloidal particles to the baked filter body. The catalytically active metal layer may then be applied, for example by impregnating the filter body with a metal slurry.

US-A-5316661 discloses A process for crystallizing A zeolite layer on A substrate.

WO-A-03/33146 discloses supported catalysts for the selective oxidation of carbon monoxide. These supported catalysts have a catalyst layer which is applied to an adhesion-promoting layer composed of crystalline silicate and silica particles on a metal support. The adhesion promoting layer is produced by applying an aqueous mixture of a crystalline silicate and a silica sol to a metal support.

EP- ｃA-1043068 discloses ｃA process for preparing supported catalysts in which ｃA catalyst-containing material is mixed with ｃA solvent and deposited by spraying on ｃA substrate heated above the boiling point of the solvent. The method enables the targeted deposition of catalyst materials with large active surface area and good adhesive strength on a substrate.

DE-A-10335510 discloses coated shaped catalyst support bodies which have a high adhesive strength and are characterized by the occurrence of cracks and a large overall crack length. According to the specification, most of these cracks terminate at the surface of the catalyst layer. The presence of voids and other porous cavities within the catalyst layer is not disclosed.

Recently, microreactors with catalytic wall elements and wall spacing < 1mm have been proposed. Examples thereof are disclosed in DE10042746a1 and DE10110465a 1.

In these wall reactors, the reaction mixture flows between two catalytically coated plate-shaped wall elements arranged in parallel in each case. Typically this reactor consists of a series of wall elements. Due to the small spacing of the wall elements, a high wall-to-volume ratio is achieved, which allows high heat dissipation rates and operation with reaction mixtures that can explode under normal conditions. The high heat dissipation rate allows very good temperature control and at the same time avoids so-called Hot Spots ("Hot Spots") in highly exothermic reactions. Thus, the wall reactor can be operated at a higher temperature level than in the case of a variable mode of operation. As a result, higher space-time yields can be achieved in the catalytic wall reactor. Other undesirable effects of hot spots, such as selectivity loss and deactivation, can also be circumvented. Owing to the good heat transfer, it is also possible in particular to use active catalysts whose heat generation in conventional reactors cannot be controlled.

In known reactors, catalytic wall elements have been used consisting of plates with fixing and sealing means. On the reaction side, the plate has one or more flat, catalyst-coated planar elements. The back of the plate can have various designs and channels for cooling or heating media are often suitable.

For such microreactors and other wall reactors, there is a need for a particularly strongly bonded catalyst layer having a uniform layer thickness and a low mass transport resistance.

The known methods and the catalyst layers prepared by said methods still need to be improved in many respects. The known methods therefore often require the use of special substance combinations or unsatisfactory layer thickness tolerances and/or adhesive strengths to be achieved.

In particular, the following requirements are present for industrially usable catalyst layers:

the layer must have a sufficiently good adhesive strength to avoid peeling during mounting and during handling

The stability of the layer must be ensured even after thermal stresses at the reaction temperature, or possibly during the calcination process required for the decomposition of the catalyst precursor

The layer thickness must be as uniform as possible in order that the flow rate in the reactor is approximately constant over the reactor width and the reactor length, a criterion which plays an important role in particular in microreactors

The layer thickness must be large enough to introduce enough catalytically active material into the reactor; typical layer thicknesses are 20 μm to 3mm

The catalyst layer must have sufficient catalytic activity, i.e. a sufficiently large internal surface area and porosity

The mass transport resistance in the catalyst layer must be sufficiently low.

Disclosure of Invention

It is an object of the present invention to provide a catalyst layer that meets these requirements.

It is a further object of the present invention to provide a process by means of which catalyst layers having good adhesive strength and high flatness and low layer thickness tolerances and low mass transport resistance can be produced in a simple and economical manner and which can be used universally with a large number of catalyst systems.

The invention relates to a carrier body having a catalytic coating comprising at least one porous catalyst layer having cavities. Within the context of the present description, "void" is understood to mean that at least two dimensions have a size of more than 5 microns or have a size of at least 10 μm²Irregular cavity of cross-sectional area.

These cavities are substantially closed and are connected to the layer surface or other cavities substantially only by pores having a diameter of less than 5 microns or cracks having a width of less than 5 microns. Cavities can be observed in REM electron micrograph of the catalyst layer impregnated with resin. The cross-sectional area or size can be determined by methods known per se, for example by quantitative microscopy. Within the scope of the present invention, "irregular cavity" is understood to mean a cavity having an aspherical and/or non-cylindrical geometry which deviates considerably from the ideal spherical and/or cylindrical shape, the inner surface of the cavity consisting of local roughness and macropores. In contrast to cracks, cavities do not have a well-defined preferential direction.

The voids are an integral part of the pore system. They are referred to as especially large macropores. In the IUPAC definition, macropores are pores with a diameter greater than 50 nanometers.

The proportion of cavities in the catalyst layer is preferably selected so that the proportion of the area of cavities visible in the representative cross-sectional view is from 2 to 60%, preferably from 3 to 50%, and very particularly preferably from 5 to 35%, where only greater than 10 μm in the cross-sectional view will be present²The visible area of (A) is evaluated as a cavity. The contrast and resolution in the image evaluation should be chosen so that only cavities (recognizable in the case of layers cast with resin at particularly dark contrast) are detected and no layer material and no pores or cracks emanating from the cavities and having a diameter of less than 5 μm are detected. In the present description, in the case of a non-uniform layer, the arithmetic mean of the area ratios of 5 randomly selected cross-sectional views distributed over the layer should be considered if not determined.

Surprisingly, such a layer rich in cavities has a particularly high adhesive strength despite a significantly reduced material density and thus reduced contact area of the particles constituting the layer. Without being bound to a theory, the inventors attribute this to two effective effects:

1. the voids prevent the propagation of cracks within the layer and thus assist in the removal of mechanically or thermally induced stresses such as those present during installation of the catalyst or during operation. In a microscopic cross-sectional view, it can be seen that the cracks appearing in the layer end up in the cavity and "fade away" there (see fig. 1). In the case of a layer without voids, such cracks extend through the entire layer and lead to mechanical instability (see fig. 2).

2. During the coating process, the cavities facilitate transport out of the solvent or suspension medium during the drying process and thereby prevent pressure build-up which can lead to mechanical damage to the layer.

The inventive layers exhibit high adhesive strength even after mechanical or thermal loading. This advantageously results in a low sensitivity during handling and use of the catalyst layer, for example during installation and operation. Typically, these layer systems exhibit an adhesive strength of > 1kPa (measured on the basis of DINEN ISO 4624), in particular > 10kPa, and very particularly > 50 kPa.

In addition to the voids, the catalyst layer of the invention preferably has a high proportion of further large pores of smaller diameter.

In a preferred embodiment, the catalyst layer contains 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. "pore volume" is understood to mean the pore volume of greater than 4 nm in diameter, as determined by mercury porosimetry in accordance with DIN 66133. It is assumed that for mercury, the contact angle is 140 ° and the surface tension is 480 mN/m. Prior to this measurement, the sample was dried at 105 ℃. The pore volume fraction in the macropores was also measured by mercury porosimetry.

According to a particularly preferred embodiment, a high proportion of macropores is responsible for the low mass transport resistance in the catalyst layer. It is thus possible to use thicker layers without loss of selectivity and activity. The advantage of a thicker layer is that more catalyst material is provided per unit area. The cost of microreactors in particular increases with the area requirement, so that potential cost savings are obtained from thicker layers.

The combination of pore volume and void volume of the catalyst layer, as measured by saturated water uptake and differential gravimetry, is typically in the range of 30 to 95%, preferably 50 to 90%, based on the total volume of the layer.

In a further preferred embodiment, the support coated according to the invention has a uniform layer thickness and a tolerance of preferably less than ± 30 μm.

Owing to the uniform layer thickness, a narrow residence time distribution can be set in the reactor, which can be caused by uniform axial and lateral flow conditions. This leads to an optimum selectivity and an optimum space-time yield.

The carrier may have any desired geometry and may be composed of a wide variety of materials. For example, they may be pipes. Planar shaped bodies, in particular sheets, are preferably used. It is particularly preferred to use planar shaped bodies having planar depressions onto which the catalyst layer is applied or grooves in addition to planar depressions.

A further design of the carrier is a so-called hot plate. It is generally understood to mean at least two at least partially parallel metal sheets which are joined to one another in point-like contact regions, for example by welding or soldering, and which are spaced apart at a distance outside these contact regions. Due to this configuration, the hot plate has a mat-like structure in which a network-like channel pattern is formed between planes of the metal sheets that are joined to each other and face each other by means of contact areas. This channel pattern can serve on the one hand as reaction spaces which are loaded with catalyst and on the other hand can be flowed through by a coolant. Hotplates are disclosed in particular in DE-A-10108380 and DE-C-10011568 and are commercially available from DEG Intense Technologies & Service GmbH, Germany.

The carrier substrate is preferably composed of a metal or ceramic material. For example, the support may consist of a metal containing aluminum, iron, copper or nickel or of a metal alloy; or it may consist of a ceramic, for example alumina, titania or silica, zirconia, silicon carbide or cordierite.

The carrier substrate can have any desired surface. Besides smooth surfaces, roughened or porous surfaces may also be used. The surface can consist of the material of the carrier substrate or of a layer consisting of a further applied material, for example with an oxide layer.

The thickness of the catalyst layer may cover a wide range, depending on the application; typically it is 50-3000 microns, preferably 200-1000 microns, where the catalyst layer may be composed of multiple monolayers which may be of the same or different composition.

Very particularly preferred supports are those in which the catalyst layer comprises an adhesion-promoting layer, which is applied directly to the support surface and may have no catalytic action. A typical thickness of this adhesion promoting layer is less than 100 microns, preferably between 100 nm and 80 microns.

Particularly preferred adhesion promoting layers exhibit a matrix that is substantially uniform in the micrometer range and preferably free of individual structures having a diameter greater than 5 micrometers, which may be formed, for example, when coarser particles are used in the supporting suspension. In contrast to the catalytic top layer, the adhesion promoting layer has no voids.

At least one macroporous layer of catalytically active material having structures with a diameter of more than 1 micrometer is applied onto the first layer.

The material of the first adhesion promoting layer may be any desired material provided that it does not change under the reaction conditions under which the catalyst layer is used. The material may include typical binder materials such as inorganic oxides and/or temperature change resistant plastics. The first layer may also contain a catalyst.

Examples of materials constituting the first adhesion promoting layer are silica, alumina, zirconia, titania and mixtures thereof.

At least one further layer containing voids is applied to the first adhesion promoting and void free layer. However, the layer containing cavities can also be applied directly to the support without an adhesion-promoting layer. The layer containing cavities typically contains structures based on particles with a diameter of more than 1 micron and consisting of catalytically active material and optionally further inert material.

The catalytic material may be selected in a wide range. Of particular interest are catalyst systems for strongly exothermic or endothermic reactions, especially for oxidation reactions. For example, the following systems can be mentioned as the basic system which is varied together with the accelerator:

noble metals supported on ceramics or activated carbon

Multimetal oxides consisting, apart from further doping, of a substance selected from the group consisting of oxides of molybdenum, bismuth, vanadium, tungsten, phosphorus, antimony, iron, nickel, cobalt and copper as a matrix

Zeolites, e.g. based on the formula (SiO)₂)_1-x(TiO₂)_xThe molecular sieve of the titanium-containing molecular sieve of (1), for example, titanium silicalite (Titansilikalite) -1(TS-1) having MFI crystal structure, titanium having MEL crystal structureSilicalite-2 (TS-2), titanium beta zeolite having the BEA crystal structure, and titanium silicalite-48 having the zeolite ZSM 48 crystal structure.

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

-in an oxide support matrix, preferably an oxide with a high proportion of silica, a metal of group VIII B of the periodic table of the elements, preferably a platinum metal, especially Pd, in combination with a metal of group IB of the periodic table of the elements, preferably Au, and an alkali metal salt, preferably an alkali metal salt of an organic acid, very preferably potassium acetate, and optionally a further promoter

-in an oxide support matrix, preferably an oxide with a high proportion of silica, a metal of group VIII B of the periodic table of the elements, preferably a platinum metal, especially Pd, in combination with a metal of group IIB of the periodic table of the elements, preferably Cd, and an alkali metal salt, preferably an alkali metal salt of an organic acid, very preferably potassium acetate, and optionally a further promoter

Mixtures and mixed oxides of the oxides of Mo, Bi, Fe, Co, Ni, and optionally further dopants, e.g. alkali metals, such as K

Mixtures and mixed oxides of Mo, V, Cu, W, and optionally further dopants, for example elements of group V A of the periodic Table of the elements, preferably Sb, and/or metals of group V B of the periodic Table of the elements, preferably Nb

Ag on alumina (which is preferably at least partially in the alpha-phase), and optionally further dopants, such as alkali metals, for example Cs, and/or metals of group VIIB of the periodic Table of the elements, for example Re

Vanadium pyrophosphate and optionally further dopants

Vanadium oxide on an oxide support and optionally further dopants

Metals of group VIII B of the periodic table of the elements, preferably platinum metals, in particular Pd and/or Pt, on alumina.

The catalytically active material may be present within an inert or supporting matrix of inorganic oxide or thermally stable plastic.

Preferred materials for this matrix are oxides of Si, Al, Ti, Zr and/or mixtures thereof.

In each case, further doping elements and other additional components conventionally used for the preparation of catalyst layers may also be present. Examples of such materials are, inter alia, alkali metal compounds, alkaline earth metal compounds, halides, phosphates and sulfate compounds.

The thickness of the catalytically active layer is particularly uniform, i.e. the layer is characterized by a high degree of flatness and low layer thickness tolerances. This is demonstrated by measuring the layer thickness using the eddy current (Wirbelstrom) principle according to DIN EN ISO 2360, which, using a plurality of individual measurements, exhibits a low standard deviation of < 35 micrometers, preferably < 25 micrometers. In contrast, the local roughness is relatively high. This local roughness does not impair the critical residence time distribution over the gap width and improves the mass transport between the gas space and the catalyst layer, since an at least partially turbulent flow occurs more rapidly in the gas space. The microscope can see a particularly open structure of the surface, which ensures good penetration of the reactants. According to the invention, this open-porous structure is formed by an open, i.e. non-closed, preforming of the cavities present on the surface of the layer, with at least two dimensions greater than 5 μm. The inner surface of these open structures facing the support has pores which open out into the catalytically active layer and thus ensure mass transport into the catalytic layer. Furthermore, there may be a separate connection between the open structure on the surface by means of the macroporous channels and the closed cavities present inside the catalytic layer, and/or there may be a separate connection between the closed cavities present inside the catalytically active layer.

The local roughness is shown in a profile map which can be recorded by a probe and passes a large number of maxima, minima and zero crossings per unit length and a high roughness depth. The layer is further characterized by particularly sharp and narrow peaks. When determining the morphology by means of a probe according to DIN EN ISO4287, the average number of zero crossings is typically > 2/mm, preferably > 2.5/mm, and most preferably 3-8/mm, provided that the measurement section under consideration is sufficiently long (measured with Form Talysurfseries 2, Taylor-Hobson Precision). The zero crossings are defined by the intersection of the contour with the midline. The roughness depth Rz measured by a probe and determined according to DIN EN ISO4287 is > 70 microns, preferably > 100 microns, most preferably > 120 microns. The total measuring section of 40mm and the individual measuring section of 8mm are used as a basis.

Catalyst coatings not according to the invention, which are obtainable, for example, by the customary casting or knife coating methods, generally exhibit large layer thickness fluctuations, but generally do not exhibit advantageous local roughness structures. Coating processes, such as CVD, which generally allow a precise adjustment of the layer thickness, are very complex and have locally smooth structures.

The roughness of the surface may optionally be reduced by post-treatment, such as grinding and polishing.

The support according to the invention with the catalytic coating can be produced by a particularly simple and economically operating process. This is also the subject of the invention.

The method of the invention comprises the following steps:

a) the initial introduction of the carrier substrate is carried out,

b) optionally applying a layer of an adhesion promoter,

c) spray solid contentIn an amount of at least 30 wt%, having a median diameter (D)₅₀Value) at least 5 μm (determined by laser diffraction in suspension) of a suspension of particles composed of the catalytically active material and/or precursors thereof and optionally further constituents of the catalytically active layer, and

d) optionally repeating step c) one or more times.

The process is carried out in such a way that the spreading of the suspension sprayed on the carrier substrate is substantially prevented. In other words, the moisture content of the droplets at the moment of impact is chosen such that, on the one hand, a sufficiently high viscosity prevents free run-off, but, on the other hand, the droplets have a sufficiently high aggregation capacity to firmly bond with the underlying layer. This can be checked under an optical microscope; the free-flowing layer has a smooth structure, whereas according to the method of the invention, a structure with a roughness in the order of microns and with openings and valleys is produced.

Under this precondition, the person skilled in the art can select the range which allows such spraying results from the parameters of solids content, mass flow, spraying distance, droplet size, substrate temperature and suspension temperature.

During the spraying process, it is preferred to use a nozzle technique which allows a well-focused jet of the spray in order to minimize overspray, i.e. the loss of material due to the sprayed material hitting parts of the support near or not to be coated. Suitable here are, for example, the HVLP nozzle technology in which the spray cone can be limited by additional compressed air nozzles.

In a particular embodiment, the carrier substrate is at an elevated temperature, but below the boiling point of the suspension medium, during the coating process. In the case of aqueous suspensions, the preferred temperature is from 30 to 80 ℃.

In a further preferred embodiment, the particles of the suspension have a broad particle size distribution with a span D_s＝(D₉₀-D₁₀)/D₅₀Is greater than 1.5. Here, D_xExpressed in a volume proportion of x% of the total particle volumeThe particle size of the largest particle in volume fraction of the smallest particles.

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

In a further preferred embodiment, a binder is added to the suspension. Suitable binders are inorganic or organic materials and mixtures thereof.

In particular, sols, very finely divided suspensions or solutions of oxides of Al, Si, Ti, Zr or mixtures thereof can be used as inorganic binder materials. Further preferred inorganic binders are median particle sizes (D)₅₀Values) < 2 μm of very finely divided oxides, e.g. pyrogenic oxides or very finely ground precipitated oxides, mechanical crosslinkers, e.g. glass fibres or special acicular or rodlike crystallites, e.g. Actigel^TM208 (manufacturer ITC-Floridin).

Organic binder materials which can be used are, in particular, polyols, such as glycerol, ethylene glycol or polyvinyl alcohol, PTFE, polyvinyl acetate, cellulose derivatives, such as methyl cellulose or cellulose fibers.

A preferred variant of the process of the invention comprises an optional substep b) in which a first suspension comprising nanoparticulate material having no particles with a diameter of greater than 5 μm is sprayed onto the support surface in such an amount that a first adhesion-promoting layer having a thickness of up to 80 μm, preferably from 5 to 30 μm, is formed.

In a further variant, the process of the invention comprises the steps a), optionally steps b) and c') defined above, with a median diameter (D) of at least 30% by weight of sprayed solids content₅₀Value) of at least 5 μm (in suspension, determined by laser diffraction) of particles composed of inert and/or catalytic material and optionally of further constituents of the catalytically active layer, and d ') optionally repeating c') one or more times, and as step e), after preparation of this layer system, using the catalytically active material and/or its precursorsAnd/or impregnation of the action-promoting material and/or its precursor.

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

Organic or other decomposable residues can be removed by calcination, for example at temperatures of 250 ℃ and 1200 ℃. The pre-treatment may include variably combining these individual processes from a sequential aspect.

The support substrate used in the process of the invention may optionally be pretreated before coating, in particular by roughening the surface of the support substrate intended to be coated with the catalyst by mechanical, chemical and/or physical means. This pretreatment can lead to a further improved adhesion of the layer to be coated to the support. This is particularly suitable for metal supports. For example, the surface of the carrier substrate to be coated can be roughened by mechanical methods, such as sandblasting or grinding, or by chemical methods, such as etching with acids or bases. Grease residues can be removed by a solvent.

The catalyst suspension to be sprayed contains at least one or more catalytically active materials or precursors thereof.

The precursor may for example be a nitrate, oxalate, carbonate, acetate or other salt which may be decomposed, e.g. converted to an oxide, by heat or oxidation.

The catalytically active material or a precursor thereof may be present in molecular, colloidal, crystalline or/and amorphous form. The actual catalytic material or a precursor thereof may be present in suspension or may be applied subsequently by impregnation.

To adjust the pH, an acid or base may be added. In addition, organic ingredients such as surfactants, binders or pore formers may be present. Suitable suspending media or solvents are especially water. However, organic liquids may also be used.

The suspension to be coated is applied by spraying or misting. The parts not to be wetted may be masked or degummed (abgeklebt).

Commercially available single or dual nozzles can be used for spraying, where the jet guidance can be carried out manually or preferably in an automated fashion. In an automated operating method, it is suitable to move the spray nozzles under computer control over the surface to be sprayed and to monitor and regulate the application of material and other parameters of the method in a targeted manner.

The spraying of the individual layers can be carried out in a manner known per se, there being a large number of process parameters available to the person skilled in the art. Examples of these are the spray pressure, the spray distance, the spray angle, the travel speed of the spray nozzle or, in the case of fixed spray nozzles, the travel speed of the substrate, the diameter of the spray nozzle, the flow rate of the material and the geometry of the spray jet. Furthermore, the properties of the suspension to be sprayed can influence the quality of the formed layer, for example the density, the dynamic viscosity, the surface tension and the zeta potential of the suspension used.

In order to produce the supports coated according to the invention, layer-by-layer coating is carried out. It may furthermore be advantageous to heat the carrier material at least during the spraying of the first suspension, but advantageously during the application of all layers. The support is preferably heated to a temperature below the boiling point of the solvent used.

After coating each layer, one-step or two-step heat treatment may be performed to perform drying and calcination. If the applied layer has not been dried, drying alone may be carried out, for example at a temperature of from 20 to 200 ℃ or drying in combination with calcination, for example at a temperature of from 200 ℃ to 1000 ℃. Drying and calcination may be carried out in an oxidizing atmosphere, for example in air, or in an inert atmosphere, for example in nitrogen.

It is also possible to apply all layers first and then to dry and calcine the layer system.

When multiple layers containing catalytically active material are sprayed, these may have the same composition; in this case, the same suspension is always used, i.e. after the optional application of the adhesion promoter layer. However, it is also possible to prepare catalytically active material-containing layers of different composition or layers composed of inert materials.

When the individual layers have been applied, it is preferred that planar layers with a total layer thickness tolerance as low as less than ± 25 μm can be produced as possible, so that no further processing is required. However, it is also possible to smooth the coated layer, for example by polishing the surface of the resulting layer system or by milling, for example using a CNC machine.

After drying or calcination, optionally further catalytic components or precursors thereof may be applied by impregnation. For reasons of operational safety and economics, it is generally appropriate to carry out this impregnation also only after possible final mechanical treatment. For this purpose, the carrier layer is coated with a solution or suspension containing the components or is immersed in the solution or suspension or is sprayed on. The impregnation may be followed by drying and/or calcination.

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

The invention furthermore provides a reactor comprising at least one support according to the invention, which support has a catalytic coating.

The supports according to the invention are preferably used in wall reactors, which also include microreactors. In the present specification, microreactors are understood to mean those reactors in which at least one dimension transverse to the flow direction of the reaction space or spaces is less than 10mm, preferably less than 1mm, particularly preferably less than 0.5 mm.

Wall reactors and, in particular, microreactors have a plurality of reaction spaces, preferably a plurality of reaction spaces extending parallel to one another.

The dimensioning of the reaction space can be arbitrary, provided that at least one dimension varies in the range of less than 10 mm.

The reaction space can have a circular, oval, triangular or polygonal, in particular rectangular or square, cross-section. The dimension of the cross section or one dimension, i.e. at least one side length or the diameter or one diameter, is preferably less than 10 mm.

In a particularly preferred embodiment, the cross-section is rectangular or circular, and only one dimension of the cross-section, i.e. one side length or the diameter, varies in the range of less than 10 mm.

The material surrounding the reaction space may be any as long as it is stable under the reaction conditions, allows sufficient heat dissipation, and completely or partially coats the surface of the reaction space with the layer system according to the invention containing the catalytically active material.

The invention therefore also relates to a reactor which can be used in particular for heterogeneously catalyzed gas-phase reactions, comprising:

i) at least one reaction space having at least one dimension of less than 10mm, and

ii) coating or partially coating the surface of the reaction space with a layer system as defined above containing the catalytically active material.

Preferred microreactors are distinguished by having a plurality of spaces arranged vertically or horizontally and in parallel, which have at least one inlet line and one outlet line each, wherein the spaces are formed by stacked plates or layers, and a part of the spaces are reaction spaces having at least one dimension in the range of less than 10mm, and the other part of the spaces are heat transfer spaces, wherein the inlet lines of the reaction spaces are connected to at least two distributor units, and the outlet lines leaving the reaction spaces are connected to at least one collection unit, wherein the heat transfer between the reaction spaces and the heat transfer spaces takes place via at least one common space wall, which is formed by a common plate.

A microreactor of the type which is particularly preferably used has spacer elements arranged in all spaces, which reactor contains at least in part the catalyst material applied to the inner wall of the reaction space by the process according to the invention, has a hydraulic diameter in the reaction space of less than 4000 micrometers, preferably less than 1500 micrometers and particularly preferably less than 500 micrometers, the hydraulic diameter being defined as the quotient of 4 times the area of the free flow cross section divided by the circumference, and the ratio of the smallest vertical distance between two adjacent spacer elements after coating with catalyst to the slit height of the reaction space is less than 800 and greater than or equal to 10, preferably less than 450 and particularly preferably less than 100.

The invention furthermore provides for the use of the support in a reactor for reacting organic compounds. These may be reactions in the gas phase, in the liquid phase or in a phase having a supercritical state.

The reactor is preferably a wall reactor, particularly preferably a microreactor.

The reaction of the organic compounds is preferably a strongly exothermic or endothermic reaction (. DELTA.H has a value of more than 50 kJ/mol).

Examples of reactions are oxidation or ammoxidation reactions, such as:

epoxidation of olefins, e.g. oxidation of propylene to propylene oxide or ethylene to ethylene oxide or oxidation of allyl chloride to epichlorohydrin

Oxidative coupling of acetic acid with ethylene to give vinyl acetate

By oxidation of ethane and/or ethylene to acetic acid

Oxidation of propene to acrolein

Oxidation of propene and/or acrolein to give acrylic acid

Oxidation of propane to give acrolein and/or acrylic acid

Oxidation of butane to formic acid or to acetic acid

Oxidation of isobutane and/or isobutene to give methacrolein and/or methacrylic acid

Oxidation of xylene and/or naphthalene to phthalic anhydride

Oxidation of butane and/or butene to give maleic anhydride

Ammoxidation of propylene to acrylonitrile

Ammoxidation of aromatic compounds to benzonitrile

Further examples of reactions are hydrogenation reactions of organic compounds, such as hydrogenation of aromatic and nitro compounds and selective hydrogenation of unsaturated organic compounds.

Further reactions of interest are the reaction of synthesis gas, for example the fischer-tropsch reaction, and methanol synthesis, or condensation reactions, for example the conversion of acetone to isophorone.

Detailed Description

The invention is described below with the aid of examples.

Example 1: wall catalyst TS-1 on aluminum 99.5

Grooves 1.0mm deep and 20mm wide were milled in the middle of three 100mm long, 30mm wide and 3mm thick aluminium plates (Al 99.5) each. The plates were acid washed in nitric acid solution for 30 minutes at room temperature, passivated with hydrogen peroxide solution after rinsing with deionized water, and then rinsed again with deionized water. After drying, the bridging part of the plate was covered with tape (Stege) and preheated to 50 ℃ in a drying oven.

In parallel with this, 16g of a starting material having a particle size distribution D was prepared₁₀/D₅₀/D₉₀: 8.05/41.5/78.4 TS-1, 20g silica sol, 1.8g water glass and 2.8g deionized water formed into a suspension. After mixing all the materials, the resulting suspension was dispersed at 15000rpm for 2 minutes using a disperser. After dispersion, the particle size distribution D of the suspension was measured₁₀/D₅₀/D₉₀：6.6/43.1/77.4。

This suspension was then used to coat preheated aluminium panels by spraying in several steps at a spraying distance of 20cm at a pressure of 0.7 bar. A binary nozzle with a nozzle diameter of 1.8mm was used. In a first step, a layer of 20 microns thickness is applied; in subsequent steps, a layer of 40 μm thickness was applied each. Thus, a catalyst layer system with a total thickness of 740 μm was produced in 18 steps. Between each step, the plates were each dried at 40 ℃ for 4 minutes. After the final step, the plates were dried at 80 ℃ for 12 hours.

The adhesive strength and morphology of the catalyst system thus prepared was investigated for one plate. The orthogonal bond strength of 100kPa was measured. For roughness, an arithmetic mean roughness value of 29 microns was measured, with a tolerance of ± 16 microns for the total layer thickness.

Fig. 3 shows a microscopic cross-section of the catalyst layer system prepared according to this example.

The void fraction of the catalyst system thus prepared was 32% of the area of the layer observed in the sectional view. The pore distribution measured by mercury porosimetry showed that 95% of the pores had a diameter > 50nm and the total porosity with cavities was 49%.

Two further plates were then installed in the experimental reactor in such a way that the grooves formed channels 20mm wide and 0.52mm high. A reaction gas consisting of propylene, gaseous hydrogen peroxide and nitrogen was passed through this channel in order to determine the catalytic performance of the catalyst system. This experiment was carried out at a temperature of 140 ℃ and a pressure of 1.2 bar over a period of 270 hours. A constant propylene conversion of 10% is achieved here at complete conversion of the hydrogen peroxide. The selectivity to propylene oxide was 93%.

Example 2: wall catalyst Pd/Au/SiO on stainless steel₂

Grooves of 1.05mm depth and 30mm width were milled in each of the middle of three 400mm long, 40mm wide and 8mm thick stainless steel plates (material No. 1.4571). The bridge remaining at the edge was masked with an aluminum template and the grooves to be coated were treated with corundum spray at a pressure of 3 bar. After removal of the template, the plate was acid-washed in a solution formed from nitric acid and hydrofluoric acid for 30 minutes at room temperature, and then rinsed to neutrality with deionized water. After drying the plates, the bridging portion of the plates was masked with tape and preheated to 50 ℃.

For this catalyst system, a particle size distribution D consisting of 37.5g of palladium, gold and silica will be used₁₀/D₅₀/D₉₀The suspension formed by the milled catalyst at 3.3/22.1/87.2 μm was mixed with 31.25g of silica sol and 31.25g of water and then dispersed at 15000rpm for 2 minutes using a disperser. Particle size distribution D of the suspension after dispersion₁₀/D₅₀/D₉₀：3.8/17.2/67.0。

The preheated steel sheet was coated with this suspension in a plurality of spraying steps at a pressure of 0.8 bar, with a spraying distance of 20cm between the sheet surface and the spray nozzles. A binary nozzle with a nozzle diameter of 1.8mm was used. In a first step, a layer of 20 microns thickness is applied; in subsequent steps, a layer of 40 μm thickness was applied each. The total thickness of the catalyst layer system thus produced was 786 μm. Between each step, the plates were dried at 40 ℃ for 4 minutes. After the final step, the plates were calcined at 250 ℃ for 6 hours.

The adhesive strength and morphology of the catalyst system thus prepared was investigated on one plate. Orthogonal bond strengths of > 100kPa were measured. For roughness, an arithmetic mean roughness value of 28 microns was measured, and the tolerance for total layer thickness was ± 15 microns.

Fig. 4 shows a microscopic cross-section of the layer system prepared according to this example.

Fig. 5 shows a profile of the surface of the layer system prepared according to this example according to DIN ISO4287 (determined with Form Talysurf Series 2, Taylor Hobson precision). The abscissa shows the scan width (in mm) and the ordinate shows the relative profile depth (in microns).

The pore distribution, measured by mercury porosimetry, gave 84% of the pores with diameters > 50 nm. The total porosity with voids was 68%.

Two further plates were then installed in the experimental reactor in such a way that their grooves formed channels of 0.53mm height and 30mm width. A reaction gas consisting of ethylene, oxygen and acetic acid was conducted through this channel in order to determine the catalytic performance of the catalyst system. This experiment was carried out at a temperature of 155 ℃ and at a pressure of 9 bar over a period of 180 hours.

Here, a yield of 1300g VAM/(kg catalyst. multidot.h) is achieved at a selectivity of greater than 95%.

Example 3: mixed oxide catalyst on stainless steel

Grooves of 1.05mm depth and 30mm width were milled in each of the middle of three 400mm long, 40mm wide and 8mm thick stainless steel plates (material No. 1.4571). The bridge remaining at the edge was masked with an aluminum template and the grooves to be coated were treated with corundum spray at a pressure of 3 bar. After removal of the template, the plate was acid-washed in a solution formed from nitric acid and hydrofluoric acid for 30 minutes at room temperature, and then rinsed to neutrality with deionized water. After drying the plates, the bridging portion of the plates was masked with tape and preheated to 50 ℃.

For this catalyst system, a suspension of 37.5g of acrolein catalyst according to example 1 of EP0900774 (catalyst 2 preparation), 31.25g of silica sol and 31.25g of deionized water was prepared and then dispersed using a disperser (Ultra Turrax) at 15000rpm for 2 minutes. Particle size distribution D after dispersion₁₀/D₅₀/D₉₀Is 0.49/13.24/24.98. The thus prepared suspension was used to coat a preheated steel plate by spraying in multiple steps at a distance of 20cm from the nozzle to the plate surface at a pressure of 1.6 bar. A binary nozzle with a nozzle diameter of 0.8mm was used. In a first step, a layer of 20 microns is applied; in subsequent steps, layers of 40 μm thickness were each applied by increasing the material flow at the nozzle. Between the individual steps, the plates were dried at 50 ℃ for 4 minutes. After the final step, the plate was calcined at 450 ℃ for 8 hours.

After cooling the plate, the adhesion strength, morphology and porosity of the catalyst layer were investigated.

Orthogonal bond strengths of > 100kPa were measured. An average roughness value of 25 microns and a layer thickness tolerance of ± 15 microns was measured. The pore distribution measured by mercury porosimetry showed that 76% of the pores had diameters > 50 nm. The total porosity was 57.4%.

Claims (48)

1. Support with catalytic coating comprising at least one porous catalyst layer containing cavities, wherein the cavities are of at least two dimensions greater than 5 microns or of at least 10 μm²Irregular cavity of cross-sectional area.

2. The carrier according to claim 1, wherein the proportion of holes in the area of 2 to 60% is determined by an arithmetic average of the proportion of areas in the catalyst layer of 5 randomly selected REM profiles.

3. The support as claimed in claim 1 or 2, wherein at least 50% of the pore volume is formed by macropores having a diameter of at least 50nm, as determined by mercury porosimetry according to DIN 66133.

4. The support of claim 1 or 2, wherein the volume formed by the pores and cavities in the catalyst layer is 30 to 95% based on the total volume of the layer.

5. The carrier according to claim 1 or 2, wherein the thickness of the catalyst layer is 50 to 3000 μm and the variation in layer thickness is < 50 μm.

6. The carrier of claim 1 or 2, wherein it has an adhesion promoting layer applied directly to the surface of the carrier substrate.

7. The carrier of claim 6, wherein the adhesion promoting layer has a thickness of up to 80 μm and consists of a nano-particulate material free of particles having a diameter of more than 5 μm.

8. The carrier of claim 6, wherein the material of the particles constituting the adhesion promoter layer is an inorganic oxide and/or a temperature change resistant plastic.

9. The carrier according to claim 1 or 2, wherein the carrier substrate is a planar shaped body having planar depressions which are coated with the catalyst layer, or wherein the planar shaped body has trenches in addition to the planar depressions.

10. A support having a catalytic coating according to claim 1 or 2, wherein it contains a further porous and cavity-containing layer consisting of a different or the same material applied to the first porous and cavity-containing catalyst layer.

11. The carrier according to claim 1 or 2, wherein the at least one porous and hole-containing catalyst layer contains particles composed of a catalytically active material and particles composed of an inert binder.

12. The support according to claim 1 or 2, wherein the catalytic coating has an adhesive strength > 1kPa measured according to DIN EN ISO 4624.

13. Support according to claim 1 or 2, wherein the measurement of the thickness of the catalytic coating according to DIN EN ISO 2360 using the eddy current principle has a standard deviation of < 35 μm.

14. The carrier body according to claim 1 or 2, wherein the surface of the catalytic coating exhibits a high local roughness, expressed by the mean of the zero crossings > 2/mm, and by the roughness depth R > 70 μm_zIs represented by R_ZMeasured by a probe and calculated to DIN EN ISO 4287.

15. The support of claim 1 or 2 wherein the at least one porous and hole-containing catalyst layer comprises a catalyst selected from the group of molecular sieves.

16. The support of claim 1 or 2 wherein the at least one porous and hole-containing catalyst layer comprises a metal of group VIII B of the periodic table in combination with a metal of group IB of the periodic table, and an alkali metal salt, and optionally an additional promoter, in an oxide support matrix.

17. The support of claim 1 or 2 wherein the at least one porous and hole-containing catalyst layer comprises a metal of group VIII B of the periodic table in combination with an alkali metal salt, and optionally an additional promoter, in an oxide support matrix.

18. The support according to claim 1 or 2, wherein the at least one porous and hole-containing catalyst layer contains the elements Mo, Bi, Fe, Co and Ni and optionally alkali metals as further dopants.

19. The carrier according to claim 1 or 2, wherein the at least one porous and hole-containing catalyst layer contains the elements Mo, V, Cu and W and optionally an element of group V A of the periodic table of the elements and/or a metal of group V B of the periodic table of the elements as further dopants.

20. The support of claim 1 or 2, wherein the at least one porous and hole-containing catalyst layer contains elemental Ag and optionally further dopants within an oxide support matrix.

21. The support of claim 1 or 2, wherein the at least one porous and hole-containing catalyst layer contains vanadium pyrophosphate and optionally a further dopant, or contains vanadium oxide and optionally a further dopant on an oxide support.

22. The support of claim 1 or 2 wherein the at least one porous and hole-containing catalyst layer comprises a metal of group VIII B of the periodic table of elements in an oxide support matrix.

23. A process for preparing a support having a catalytic coating according to claim 1, comprising the steps of:

a) the carrier substrate is initially added to the reaction mixture,

b) optionally applying a layer of an adhesion promoter,

c) having a solids content of at least 30 wt.% and a median diameter D, determined by laser diffraction, in suspension₅₀Particles of catalytically active material having a value of at least 5 micrometers and/or the likeA suspension of the precursor and optionally further constituents of the catalytically active layer, and

d) optionally repeating step c) one or more times.

24. A process for preparing a support having a catalytic coating according to claim 1, comprising the steps of:

a) the carrier substrate is initially added to the reaction mixture,

b) optionally applying a layer of an adhesion promoter,

c') a spray solids content of at least 30% by weight, a median diameter D determined by laser diffraction in suspension₅₀A suspension of particles of inert and/or catalytic material having a value of at least 5 μm and optionally further constituents of the catalytically active layer, and

d ') optionally repeating step c') one or more times, and

e) after the layer system has been produced, it is impregnated with the catalytically active material and/or its precursors.

25. The method of claim 23 or 24, wherein a nozzle technique is used in connection with spraying, in which the spray cone is limited by additional compressed air nozzles.

26. The method of claim 23 or 24, wherein the carrier substrate is at an elevated temperature but below the boiling point of the suspension medium during the coating process.

27. The method of claim 23 or 24, wherein the particles used therein have a span D_s＝(D₉₀-D₁₀)/D₅₀Suspensions with broad particle size distribution > 1.5.

28. The method of claim 23 or 24, wherein the suspension contains milled or broken particles having a rough surface and irregular shape.

29. The method of claim 23 or 24, wherein the suspension contains a binder.

30. The process of claim 23 or 24, wherein in step b) a first suspension comprising nanoparticulate material having no particles having a diameter of greater than 5 micrometers is formed, wherein the first suspension is sprayed onto the support surface in an amount such that the first adhesion promoting layer has a thickness of up to 80 micrometers.

31. A method according to claim 23 or 24, wherein the carrier substrate used is treated prior to coating.

32. The method according to claim 23 or 24, wherein the individual layers of the upper total layer system or parts thereof are dried and/or calcined after spraying of these layers.

33. A reactor comprising at least one catalytically coated support according to claim 1.

34. The reactor of claim 33, wherein it is a plate reactor or a tubular reactor.

35. The reactor according to claim 33 or 34, wherein it contains a planar support with a catalytic coating and is a microreactor.

36. The reactor according to claim 33 or 34, wherein it is useful for heterogeneously catalyzed gas phase reactions and comprises:

i) at least one reaction space having at least one dimension of less than 10mm, and

ii) coating or partially coating the surface of the reaction space with a layer system according to claim 1 containing a catalytically active material.

37. The reactor according to claim 35, wherein it has a plurality of spaces arranged vertically or horizontally and in parallel, said spaces having at least one inlet line and one outlet line each, wherein the spaces are formed by stacked plates or layers, and a part of the spaces are reaction spaces having at least one dimension in the range of less than 10mm, and the other part of the spaces are heat transfer spaces, where the inlet lines of the reaction spaces are connected to at least two distributor units and the outlet lines leaving the reaction spaces are connected to at least one collection unit, where the heat transfer between the reaction spaces and the heat transfer spaces is effected by means of at least one common space wall, which is formed by means of a common plate.

38. The reactor according to claim 35, wherein it is provided with spacer elements arranged in all spaces, at least partially contains the layer system containing catalytically active material according to claim 1 on the inner walls of the reaction space, and has a hydraulic diameter in the reaction space of less than 4000 micrometers, said hydraulic diameter being defined as the quotient of 4 times the area of the free flow cross section divided by the circumference, and the ratio of the smallest vertical distance between two adjacent spacer elements after coating with catalyst to the slot height of the reaction space is less than 800 and greater than or equal to 10.

39. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of propylene to propylene oxide.

40. Use of a support according to any one of claims 1 to 22 in a process for the oxidative coupling of acetic acid with ethylene by means of oxygen to give vinyl acetate.

41. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of propylene to acrolein and/or acrylic acid.

42. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of propane to acrolein and/or acrylic acid.

43. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of ethylene to ethylene oxide.

44. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of allyl chloride to epichlorohydrin.

45. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of xylene and/or naphthalene to phthalic acid (anhydride).

46. Use of a support according to any one of claims 1 to 22 in a process for the catalytic oxidation of butane and/or butene to maleic anhydride.

47. Use of a support according to any one of claims 1 to 22 in a process for the catalytic hydrogenation of an organic compound.

48. Use of a support according to any one of claims 1 to 22 in a process for synthesis gas reactions.