Structured membrane unit, manufacturing process and setup process

Abstract

A membrane unit (10) for a membrane reactor comprises a membrane (12) and a support structure (14) for supporting the membrane (12). The support structure (14) is designed such that cavities (18) adjacent to the membrane (12) are provided for receiving catalyst material (20). In this way, a loose bed of catalyst material can be filled into the cavities, and catalyst material located in the cavities can be removed from the cavities. This makes it possible to exchange the catalyst material independently of the membrane.

Description

The invention relates to a membrane unit for a membrane reactor, to a method for producing such a membrane unit and to a method for setting up a membrane unit.Membrane reactors make catalytic reactions possible and at the same time the separation and / or supply of substances via the membrane. In this way, the thermodynamics of the reaction can be influenced, for example in order to increase the yield or to influence selectivities. Membrane reactors are used in a wide variety of applications, for example in the chemical industry or in fuel cells and electrolysers.Membrane reactors are known in which the catalyst material is part of the membrane. This can be achieved, for example, by impregnating the membrane material with catalytically active species, depositing prefabricated catalytic nanoparticles, immobilizing molecular catalysts or by using catalytically self-active membrane materials.On the other hand, membrane reactors are known in which the catalyst material is integrated into the supporting structure.In addition, fluidized-bed membrane reactors are known in which the catalyst material is not fixed, but is located in a movable layer in the region of the membrane. Loose catalyst beds are also known.It is the object of the invention to provide an improved membrane unit and a method for producing and a method for setting up such a unit.The object is achieved by the membrane unit according to claim 1 and by the production method and the setup method according to the subordinate claims. Advantageous embodiments are specified in the dependent claims.To achieve the object, a membrane unit for a membrane reactor is used. The membrane unit comprises a membrane and a support structure for supporting the membrane. The supporting structure is structured in such a way that cavities are present for receiving catalyst material. The voids are immediately adjacent to the membrane or are separated from the membrane by one or more intermediate layers.The solution according to the invention has the effect that a loose bed of catalyst material can be filled into the cavities and that catalyst material located in the cavities can be removed from the cavities. In this way, it becomes possible to exchange the catalyst material, for example in the case of irreversible deactivation, while the membrane together with the supporting structure is retained. If, on the other hand, the membrane is irreversibly deactivated, it can also be exchanged together with the supporting structure and the catalyst material can be used further. i.e. both the catalyst and the membrane can be regenerated, recycled or exchanged separately.In some processes, for example, the catalyst material cokes over time. The invention makes it possible to exchange the catalyst material and to re-equip and further use the membrane. In this way, the life of the membrane is significantly extended and costs and technical outlay are reduced. Typically, the membrane or membrane and reactor combination is cost driving in membrane reactors for catalytic reactions, while the catalyst has a lower cost fraction. Therefore, particularly high savings can be achieved in this field of technology.A further advantage is the position of the catalyst material directly adjacent to the membrane or to the intermediate layer. In this way, close contact is ensured and through short paths, material transfers are improved. Fabric transport limitations are minimized. In comparison with a loose catalyst bed on a membrane, the catalyst is fixed transversely to the direction of extension of the membrane. Thus, the susceptibility to errors is minimized. An improper transport of the catalyst up to its discharge is prevented. It is possible for the membrane to be constructed from a plurality of layers. The catalyst material is arranged adjacent to the outermost layer of the membrane or to the intermediate layer.Compared to membranes with immobilized catalyst, the amount of catalyst is not limited by the surface of the membrane, since a larger amount of catalyst material per unit area of the membrane can be provided in the cavities. Competition between permeation through the membrane and productivity of the catalyst is avoided. The catalyst loading can be adjusted or optimized in a targeted manner for different operating points.A membrane reactor is a reactor containing a membrane. In particular, the membrane serves for separation. In particular, the membrane reactor is configured to carry out a physical, chemical and / or biochemical reaction. In particular, the membrane reactor is a fixed-bed reactor. In addition to chemical and biological membrane reactors, the solution according to the invention can also be used for any type of membrane separation process, with comparable advantages being produced.The membrane is in particular a selectively gas-permeable membrane, that is to say a membrane which allows only a specific gas or only a specific group of gases to pass through. The membrane is typically planar. In particular, the membrane is planar. In one embodiment, however, the membrane can also be curved, for example tubular, that is to say tubular. The membrane may be a metallic membrane or a ceramic membrane. The membrane may have an area that is greater than 1 mm 2 and / or less than 1 m 2. A variety of membranes may be used in a membrane reactor. The membrane may be constructed from one or more layers.The support structure serves for mechanically supporting the membrane. In this way, the mechanical forces acting on the membrane are absorbed or dissipated by the supporting structure. The supporting structure thus serves as a burst protection. In one embodiment, the support structure is porous. In this way, material transport can also take place through the support structure itself in addition to the path through the cavities. This improves the transport of the material.The support structure is structured. This means that the supporting structure is not present as a solid component which bears substantially over the full surface of the membrane, but that the supporting structure has shaped elements which form cavities between one another. In particular, there is a regular sequence of shaped elements. In one embodiment, at most 70% of the surface of the membrane is in contact with the support structure. The remaining 30% then fall onto cavities. In one embodiment, at most 50% or at most 30% of the surface of the membrane is in contact with the support structure. In one embodiment, at most 10% of the surface of the membrane is in contact with the support structure.The support structure is formed such that the cavities are present. The support structure encloses the cavities at least in one spatial direction. Pores of a porous medium are not hollow spaces within the meaning of the invention. In other words, the supporting structure is macroscopically structured. Typically, the cavities have been introduced in a targeted manner. Preferably, the cavities are arranged regularly. The cavities preferably have the same sizes and / or shapes. In this way, defined conditions for the operation of the membrane reactor can be created.In particular, the cavities are accessible. This means that the membrane unit is formed such that the cavities are open at least to a side on which the membrane or an intermediate layer does not lie. In this way, catalyst material can be filled in and / or removed. This does not exclude the possibility that closable openings for the cavities may be present in the membrane reactor into which the membrane unit is inserted or in a holder for the membrane unit. Such openings may allow for the filling and / or removal of the catalyst material into one or more cavities in the open state and / or prevent an improper penetration of catalyst material into one or more cavities and / or an improper removal of catalyst material from one or more cavities in the closed state.In particular, the catalyst material is present as a loose bed. The cavities are such that the catalyst material can be introduced into the cavities and removed from the cavities. For example, the catalyst material may be in a spherical shape, a cylindrical shape or a tablet shape. A desired grain size distribution can be used. The size and shape of the cavities can be adapted specifically to the catalyst material to be used.In one embodiment, there are connecting channels that connect a plurality of cavities to one another. In this way, a hierarchical structure can be generated. Via the connecting channels, catalyst material of a plurality of cavities can be removed or introduced simultaneously. Connecting channels typically do not have direct contact with the membrane. Connecting channels typically have a larger cross section than the cavities adjoining the membrane or intermediate layer.Between the membrane and the support structure, one, two or more intermediate layers may be present. Typically, at most one intermediate layer is present. An intermediate layer may be porous or dense. An intermediate layer can serve, for example, as a protective layer. For example, an intermediate layer can serve as a diffusion barrier, in particular if the membrane and the supporting structure consist of different materials. An intermediate layer may have, for example, the same or a similar thickness as the membrane. For example, the thickness of the intermediate layer can be between 20% and 500% of the thickness of the membrane, in particular between 50% and 200% of the thickness of the membrane and preferably between 70% and 150% of the thickness of the membrane. Taken together, all intermediate layers present typically have a smaller thickness than the supporting structure. An intermediate layer preferably has a similar thickness to the membrane or is thinner than the membrane. If the intermediate layers are too thick or if too many intermediate layers are present, the material transport and / or the supporting effect of the supporting structure can be impaired.In one embodiment of the membrane unit, the cavities are accessible. In this way, the removal of catalyst material and / or the filling with catalyst material is possible without additional working steps. In particular, the cavities are accessible on a side facing away from the membrane. Alternatively, the cavities can also be accessible laterally. "Accessible" means that the cavities have an opening to the environment. In particular, the opening to the environment has an opening width which has at least 20%, in particular at least 50%, preferably at least 80% or at least 90%, of the width of the respective cavity in the region adjoining the membrane or the intermediate layer. Thus, the removal of catalyst material and / or the filling with catalyst material can be carried out particularly easily.In a further embodiment, the supporting structure comprises webs. In particular, the supporting structure is constructed from webs. In particular, the webs are arranged spaced apart from one another. In other words, the webs typically do not touch one another at least in the region of the membrane. The webs typically form elongate cavities between one another in the region of the membrane. However, it is possible for the webs to contact one another in a region facing away from the membrane and / or to together form a continuous component. The webs can have rectilinear walls.In one embodiment, the webs are oriented at an angle α between 80° and 100°, preferably between 85° and 95°, in particular approximately 90°, with respect to the membrane surface. The angle α is measured between a central axis, as seen in cross section, of the respective web and the surface of the membrane facing the web. In this way, the cavities also extend at this angle to the membrane. The production of such a membrane unit is particularly simple.In one embodiment, the webs are oriented at an angle α between 20° and 80° to the membrane surface. In this way, filling with catalyst material and removal of catalyst material are facilitated. For example, the angle α is between 30° and 60°. It has been found that the filling and removal of catalyst material is thus possible in a particularly simple manner.In one embodiment, walls of the webs run straight. The course of the walls of the webs relates in particular to the walls which run along the main direction of extent of the webs. In particular, straight cavities are present between the walls. In particular, the walls of the webs are planar.In one embodiment, walls of the webs are corrugated. In one embodiment, walls of the webs are rough. By corrugation and suitable roughness, the filling with catalyst material and the removal of catalyst material can be further improved.In one configuration, the supporting structure is configured such that an extent of the cavities measured parallel to the membrane becomes greater with increasing distance from the membrane. The cavities thus taper in the direction of the membrane.In this way, filling with catalyst material and removal of catalyst material are further simplified. In particular, shaped elements of the support structure, between which the cavities are located, are shaped in such a way that a distance between adjacent shaped elements increases with increasing distance from the membrane. The shaped elements can be separate elements such as webs. The shaped elements can alternatively be regions of a component, in particular a coherent component. For example, in a contiguous part of the support structure, cylindrical or conical cavities can be present, which run as far as the membrane. In this case, the walls of the supporting structure delimiting these cavities can be the shaped elements.In a further embodiment, cavities are present which are surrounded over their entire circumference by the material of the supporting structure. The cavities are in particular at least partially cylindrical or conical. Such a configuration enables fixing of the catalyst material in all directions transversely to the membrane. Undesired transport or discharge of the catalyst material can thus be prevented.In particular, the membrane is located at one end of the cavities. In particular, the other end of the cavities is open. The cavities can be formed at least in sections cylindrically and / or at least in sections conically. Different regions of the cavities can be shaped differently. The different regions can be in particular different sections along the longitudinal extent of the cavities. The cavities may be completely cylindrical or conical in shape.The cylindrical cavities can be circular cylindrical. Alternatively, other cross sections are possible, such as square or honeycomb cross sections. The conical cavities can likewise have the aforementioned cross sections. In the case of conical cavities, the cross section of the respective cavity narrows in one direction.In a viewing direction perpendicular to the membrane, the cavities are typically surrounded over their entire circumference by material of the supporting structure. The cavities are typically not surrounded by material of the supporting structure at the longitudinally situated ends of the cavities, but rather are open.In particular, the cavities are arranged regularly. The cavities can be arranged, for example, in rows and / or columns. Respectively adjacent cavities of each column and / or each row may have the same distances from one another. For example, a cubically dense arrangement can be achieved. In another exemplary embodiment, the cavities of adjacent rows and / or columns are arranged offset. Here too, adjacent cavities of each column and / or of each row can have the same distances from one another. Thus, for example, the hexagonally dense arrangement can be achieved.In one configuration, the supporting structure comprises walls having a wall thickness of at least 10 μm, in particular at least 30 μm and / or at most 1 cm, in particular at most 1000 μm, between which cavities are located.The cavities are separated from one another by walls of the supporting structure having the specified wall thickness. In particular, the wall thickness is meant in a position directly adjoining the membrane or the intermediate layer. This range has been found to be suitable for most applications.The walls may be in the form of webs. The walls can have a constant wall thickness, for example. Alternatively, the walls can be arranged in a continuous layer of the supporting structure and thereby separate individual cavities from one another. In this case, the wall thickness means the minimum wall thickness between two adjacent cavities.Alternatively or additionally, the cavities have an extent ≥50 μm and / or ≤1 cm, in exceptional cases also up to several cm. In particular, the extent of the cavities in a position directly adjoining the membrane or the intermediate layer is meant. The extension may be the minimum extension. Smaller cavities are difficult to fill with catalyst material and catalyst material is difficult to remove. Cavities that are too large, on the other hand, lead to a low mechanical stability of the membrane unit, since the membrane is then present over long distances without support. In order to operate reliably below the burst protection limit, the extent of the cavities must be limited according to the requirements. The specific size of the cavities depends on the particular specifications and boundary conditions, for example the transmembrane pressure.In a further configuration, the membrane unit comprises the catalyst material located in the cavities. The catalyst material is in particular a powder or granulate with a defined grain size distribution and / or with a defined shape. The following can apply to the grain size or size distribution of the catalyst: the diameter d of the catalyst grains is smaller than the diameter of the cavity and / or the diameter d is at least 20 μm, in particular at least 50 μm and / or at most 1 cm, in particular at most 1000 μm. The diameter d of the catalyst grains is in particular less than or equal to the diameter Dh of the cavity. In particular, the cross section of the cavity at the thinnest point is meant. Preferably, the ratio d / Dh is at least 0.01 and / or at most 0.9.In one embodiment, the membrane comprises a material or the membrane is produced from a material which is selected from the group of cation-conducting oxides, in particular the group of proton-conducting oxides, in particular from the group comprising BaCe x Ce y Y z O 3( BZCY) with x+y+z=1, BaCe x Y y O 3( BZY) with x+y=1 and SrCe x Ce y Y z O3(SZCY) with x+y+z=1.In one embodiment, the membrane comprises a material or the membrane is produced from a material which is selected from the group of the anion-conducting oxides, in particular the group of the oxygen-ion-conducting oxides, in particular from the group comprising Zr 0.92 Y 0.08 O 2(8 YSZ), Ce 0.9 Gd 0.1 O (CGO or GDC).In one embodiment, the membrane comprises a material or the membrane is made of a material selected from the group of mixed ion-electron-conducting oxides, in particular from the group comprising La 6-x WO12-δ(LWO), where 0.2<x<0.8; δ denotes the deviation from the nominal oxygen amount and is dependent on the composition and the ambient conditions, La 6-x W 1-y Mo y O12-δ(LWO-Mo), where y≤0.4, SrTi x Fe 1-x O 3( STF), where 0.5<x<1), Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O3-δ(BSCF), and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3-δ(LSCF).In one embodiment, the membrane comprises a material or the membrane is produced from a material which is selected from the group of the hydrogen-conducting metals, in particular from Pd, Pd-Ag or other ceramic-supported Pd-containing membranes.A further aspect of the invention is a method for producing a membrane unit according to the invention. The support structure is manufactured using an additive manufacturing method. All features, advantages and properties of the membrane unit described above apply analogously to the production method and vice versa.The additive manufacturing method is selected in particular from 3D screen printing, material extrusion, free jet binder application, free jet material application and bath-based photopolymerization. 3D screen printing (3D screen printing) involves pressing material layer by layer through a printing form in order to build up the part to be produced layer by layer. In material extrusion (material extrusion), material is selectively deposited through an opening to build up the part to be produced layer by layer. In the case of binder jetting (free-jet binder application), pulverulent starting material is combined at selected positions with a binder, in order to produce workpieces. In the case of free-jet material application (material jetting), material is applied in the form of droplets and subsequently cured, in particular by UV light or heat. In bath-based photopolymerization (bath photopolymerization), liquid photopolymer in a container is selectively cured by photoactivated polymerization.Additive manufacturing methods make it possible to produce the cavities according to the invention particularly easily and cost-effectively. Cavities can thus be produced in a targeted manner. It is possible to produce directed channels, uniformly arranged cavities and thus membrane units, the behavior of which can be predicted and modeled. Moreover, hierarchical structures, for example with connecting channels, can be produced. It is possible to produce structures whose geometry is structured over several orders of magnitude, for example from the μm range to the cm range. Particularly advantageous structures can be produced which cannot be produced using conventional methods, such as, for example, oblique webs, undercuts or cavities.In particular, a support structure green body is provided with an additive manufacturing method. Sintering can then be carried out in order to produce the supporting structure.In one embodiment, a pore former is used to produce a porous layer. In particular, a porous support structure is thus produced.In one embodiment, the membrane is manufactured using an additive manufacturing method or using film casting. The additive manufacturing method is selected in particular from 3D screen printing, material extrusion, free jet binder application, free jet material application and bath-based photopolymerization.In film casting, an especially ceramic powder, typically together with a dispersant, is dispersed in a solvent in order to produce a slip. The slip is cast onto a casting substrate, dried, optionally a blank, and sintered. In particular, sequential film casting can be carried out, in which two or more layers are cast one above the other.Alternatively or additionally, a plurality of layers and / or layer composites can be connected to one another by heat treatment and / or lamination. A material bond can also be produced in this way.In sequential film casting, the membrane and the supporting structure can be produced with two different slips. A pore former can be used to produce a porous layer, for example in the region of the supporting structure.In particular, a membrane green body is provided by an additive manufacturing method or by film casting. Sintering can then be carried out in order to produce the supporting structure.In one configuration, the membrane green body and the support structure green body are provided in one working step, in particular by means of an additive manufacturing method.In a further embodiment, the method comprises the provision of a membrane green body, the provision of a support structure green body and a joint sintering of the membrane green body and the support structure green body for producing a composite of membrane and support structure.It is immaterial whether the membrane and the supporting structure are first produced from the respective green bodies and these are subsequently connected to one another, whether the green bodies are first connected to one another and the membrane and the supporting structure are subsequently produced therefrom, or whether these processes proceed at least partially simultaneously. By sintering, the membrane and the supporting structure are connected to one another in a materially integral manner. A one-piece composite component is thus produced.The membrane green body can be provided by means of an additive manufacturing method or using film casting. The support structure green body can be provided by means of an additive manufacturing method.In one configuration, the green bodies are produced separately and then contacted. In another embodiment, the green bodies are produced together. The composite is preferably a materially bonded composite.The method makes it possible to produce the membrane unit according to the invention in a simple and cost-effective manner.A further aspect of the invention is a membrane assembly which comprises a membrane unit according to the invention and a holder for holding the membrane unit. The holder can be designed as a frame for receiving the membrane unit. The membrane unit is fastened to the holder, for example by means of solder such as, for example, glass solder. In particular, at least the supporting structure of the membrane unit is mechanically fastened to the holder. Preferably, the membrane is also fastened to the holder. Typically, the membrane is sealed with respect to the holder, in particular with the glass solder. All features, advantages and properties of the membrane unit described above apply analogously to the membrane assembly and vice versa.A further aspect of the invention is a fixed-bed membrane reactor which comprises at least one membrane unit according to the invention. All features, advantages and properties of the membrane unit described above apply analogously to the fixed-bed membrane reactor and vice versa.A further aspect of the invention is a method for setting up a membrane unit according to the invention, in which a catalyst material to be replaced is removed from the cavities and / or catalyst material is introduced into the cavities. All features, advantages and properties of the membrane unit described above apply analogously to the setup method and vice versa. In other words, the method can be a method for introducing the catalyst material and / or a method for removing the catalyst material.The catalyst material can be introduced by showering, i.e. by gravity, brushing, blowing, for example fluidized in a fluid, which can be, for example, a liquid, a gas, a liquid-gas mixture or a gas mixture, and / or by pressure impact. The removal of the catalyst material from the cavity can be effected by pouring out, i.e. by gravity, brushing out, blowing out, for example fluidized in a gas or gas mixture, and / or by pressure impact. These methods can be combined as desired.The method may also comprise operating the membrane unit, preferably in a membrane reactor. In this case, the method may be referred to as a method for operating a membrane unit.In one exemplary embodiment, a membrane unit is joined, for example by means of solder such as, for example, glass solder. For example, the membrane unit is joined to another membrane unit or a holder.The invention is explained in more detail below with reference to examples.The following are shown: FIG. 1 : a section through a membrane unit from a first side; FIG. 2 : a section through a membrane unit from a second side; FIG. 3 : a view of a membrane unit from the supporting structure; FIG. 4 : Schematic illustration of an exchange of catalyst material; FIG. 5 shows a section through a further membrane unit; FIG. 6 : a membrane unit with catalyst material; FIG. 7 : removal of catalyst material from a membrane unit; FIG. 8 : shows a further filling of a membrane unit with catalyst material; FIG. 9 shows a section through a further membrane unit; FIG. 10 shows a section through a further membrane unit; FIG. 11 shows a section through a further membrane unit; FIG. 12 : a view of a further membrane unit from the supporting structure; FIG. 13 : a view of a further membrane unit from the supporting structure; FIG. 14 : a view of a further membrane unit from the supporting structure; and FIG. 15 : a view of a further membrane unit from the supporting structure.FIGS. 1 and 2 show sections of a membrane unit 10 according to the invention from two different sides. On the upper side is the membrane 12, which has a thickness of 50 μm, for example. Below this is a support structure 14, which mechanically supports the membrane 12. The support structure 14 is structured such that there are cavities 18 which adjoin the membrane 12. A catalyst material 20 can be arranged in these cavities 18. In addition to the embodiments shown here, one or more intermediate layers, not shown here, can also be present between membrane 12 and supporting structure 14.The support structure 14 is composed of webs 15. The wall 16 of the webs 15 has a width c of 30 μm and a depth b of 300 μm. The webs 15 have a spacing a of 50 μm. The depth b of the walls 16 corresponds to the depth of the cavities 18. the webs 15 are arranged at an angle α of 90° with respect to the membrane 12.The figures are purely schematic and the sizes or size ratios of the individual components are not true to scale.FIG. 3 shows a membrane unit 10, in particular from FIGS. 1 and 2, alignment of the supporting structure 14. Between the webs 15 the membrane 12 is visible in each case through the cavities 18.FIG. 4 shows a similar view in which a granulated catalyst material 20 is schematically arranged in the upper cavity 18 shown. To the right of the membrane unit 10 shown, a single grain or particle of the catalyst material 20 having the diameter d is shown. Arrow 25 denotes an introduction of catalyst material 20; arrow 26 denotes an discharge of catalyst material 20; for example, a pressure impulse takes place, with which the catalyst material 20 contained in the cavity 18, which is, for example, irreversibly deactivated, is fluidized and in this way, in particular transversely to the membrane 12, is transported in the direction of longitudinal extent of the cavity 18, through the cavity 18 and out of the latter. Alternatively or additionally, a fresh catalyst material 20 can be introduced into the cavity 18 in the same way. Also, by filling in the fresh catalyst material 20, the catalyst material 20 contained can be displaced and in this way removed from the cavity 18. Alternatively or additionally, the catalyst material 20 can be introduced and / or removed by brushing in or brushing out.FIGS. 5 to 8 show a further embodiment of a membrane unit 10 in a sectional illustration. Here, the membrane 12 is vertically oriented. The support structure 14 is also composed of webs 15, the walls 16 of which are characterized with the same parameters as described above with reference to FIGS. 2 and 3. In this exemplary embodiment, however, the angle α is less than 80° and in particular between 40° and 60°, preferably between 50° and 55°. The cavities 18 also have corresponding angles α to the membrane 12, FIG. 6 shows a similar illustration in which a granulated catalyst material 20 is arranged schematically in the upper cavity 18 illustrated. The support structure 18 may be located on the sweep side or on the reactor side of the membrane 12.By the above-described selection of the angle α, the filling and removal of the catalyst material 20, as exemplarily shown in FIGS. 7 and 8, is substantially simplified. FIG. 7 shows a pouring of catalyst material 20 by gravity and / or in a fluidized state. Due to the inclined webs 15, the catalyst material 20 can be transported in a simple manner as far as the membrane 12 due to gravity. FIG. 8 shows the generation of a pressure surge 27, for example from a gas or gas mixture, for the introduction and / or discharge of catalyst material 20.FIG. 9 shows a further embodiment of a membrane unit 10. In addition to the support structure 14, which is arranged on the one side of the membrane 12, a support structure 14 is now also arranged on the opposite side of the membrane 12. The side shown on the left is the sweep side and the side shown on the right is the reactor side. Accordingly, the parameters characterizing the support structure 14 are provided with the indices S and R. In one embodiment, both supporting structures 14 are of similar or identical construction. For example, the same number of webs 15 can be provided with webs 15 with the same width c S, c R, of the same depth b S, b R, the same distance a S, a R and / or with the same angle α, β. Individual parameters such as, for example, the angle α, β or the depth b S, b R can also be chosen differently.FIG. 10 shows an embodiment of a membrane unit 10 which is similar to the embodiment from FIG. 2, the description of which is referred to here. Instead of walls running in a straight line, however, the webs 15 have corrugated and / or rough walls 16. The webs in this embodiment are also referred to as lamellae. In addition to the features and properties discussed above with respect to FIG. 2, which may analogously apply in the embodiment shown here, the roughness of the wall 16 and the periodicity may be selected in desired ranges. A mean roughness value between 0.05 μm and 300 μm, in particular between 2 μm and 100 μm, has proven to be particularly advantageous. In addition, a periodicity or a groove spacing between 1 μm and 300 μm, in particular between 5 μm and 100 μm, has proven to be particularly advantageous.FIG. 11 shows another embodiment of a membrane unit 10, which is likewise based on FIG. 2, to which reference is hereby made. The webs 15 of FIG. 1 have parallel walls 16. In contrast, the webs 15 according to FIG. 11 are shaped such that the cavities 18 taper conically towards the membrane 12. A distance a 1 between the individual webs 15 in the region directly adjacent to the membrane 12 is smaller than a distance a 2 between the webs 15 at the end of the webs 15 facing away from the membrane 12. Thus, when filling with catalyst material and when removing catalyst material, a funnel effect is obtained which facilitates filling. In the exemplary embodiment shown here, the walls 16 of the webs 15 additionally have, for example, a linear course. This is advantageous for reasons of fluidic technology.Further embodiments of a membrane unit 10 are shown in FIGS. 12 to 15. As in FIG. 3, the view is directed at the supporting structure 14 and the membrane 12 lying behind it. In contrast to the embodiments described hitherto, the supporting structure is not constructed from webs 15, but rather forms a continuous layer which has apertures. The apertures form the cavities 18 adjoining the membrane 12 for receiving catalyst material 20. The cavities 18 are accordingly surrounded over their entire circumference by the material of the supporting structure 14. The membrane 12 is visible through the apertures. The apertures may have various shapes, such as a square or rectangular shape as shown in FIG. 12, a circular shape as shown in FIG. 13, or a hexagonal or honeycomb shape as shown in FIG. 14, for example, the apertures may be arranged in a checkerboard pattern as shown in FIGS. 12 to 14. Alternatively, the apertures may be offset as shown in FIG. 15. The apertures can be cylindrical or conical, for example similar to FIG. 11, with a size decreasing in the direction of the membrane. The apertures can be arranged perpendicular or at an angle to the membrane 12.In one exemplary embodiment, a composite of membrane green body and support structure green body is produced using an additive manufacturing method, for example using 3D screen printing, free-jet binder application, free-jet material application or bath-based photopolymerization, and is then sintered. The two green bodies can be produced in one working step.In a further exemplary embodiment, a membrane green body is produced using an additive manufacturing method, for example 3D screen printing, and the support structure green body is produced using another additive manufacturing method, for example material extrusion, and is subsequently sintered. The sintering typically occurs together in order to obtain a single-piece component.In a further exemplary embodiment, the membrane and the supporting structure are produced from different materials and are subsequently connected to one another by a material bond by heat input.In a further exemplary embodiment, the membrane green body is produced by film casting and the support body green body is produced by an additive manufacturing method.List of reference characters10 Membrane unit 12 Membrane 14 Supporting structure 15 Web 16 Wall 18 Cavity 20 Catalyst material 25 Entry 26 Discharge 27 Pressure surge a, a S, a R, a 1, a 2 distance b, b S, b R depth c, c S, c R width d, d R diameter α, β angle

Claims

Membrane unit (10) for a membrane reactor, comprising a membrane (12) and a support structure (14) for supporting the membrane (12), characterized in that the support structure (14) is structured such that cavities (18) for accommodating catalyst material (20) are present, wherein the cavities (18) directly adjoin the membrane (12) or are separated from the membrane by one or more intermediate layers.Membrane unit (10) according to the preceding claim, characterized in that the cavities (18) are accessible on a side of the supporting structure (14) facing away from the membrane (12).Membrane unit (10) according to one of the preceding claims, characterized in that the supporting structure (14) is constructed from webs (15).Membrane unit (10) according to claim 3, characterised in that the webs (15) are oriented at an angle α between 80° and 100°, in particular between 85° and 95°, to the membrane surface.Membrane unit (10) according to claim 3, characterised in that the webs (15) are oriented at an angle α between 20° and 80° to the membrane surface.Membrane unit (10) according to one of Claims 3 to 5, characterized in that walls (16) of the webs (15) run straight.Membrane unit (10) according to one of Claims 3 to 5, characterized in that walls (16) of the webs (15) run in a corrugated manner.Membrane unit (10) according to one of the preceding claims, characterized in that an extent of the cavities (18) measured parallel to the membrane (12) increases with increasing distance from the membrane (12).Membrane unit (10) according to one of the preceding claims, characterized in that cylindrical or conical cavities (18) are present, which are surrounded over their entire circumference by the material of the supporting structure (14).Membrane unit (10) according to one of the preceding claims, characterized in that the supporting structure (14) comprises walls (16) with a wall thickness of between 10 μm and 1 cm, between which cavities (18) are located.Membrane unit (10) according to one of the preceding claims, characterized in that the membrane unit (10) comprises the catalyst material (20) located in the cavities (18).Method for producing a membrane unit (10) according to one of Claims 1 to 11, characterized in that the supporting structure (14) is produced using an additive manufacturing method.Method according to the preceding claim, characterized in that the membrane (12) is produced using an additive manufacturing method or using film casting.Method according to one of the two preceding claims, characterized in that the method comprises: - providing a membrane green body, - providing a support structure green body, - sintering the membrane green body and the support structure green body together to produce a composite of membrane (12) and support structure (14).Method for setting up a membrane unit (10) according to one of Claims 1 to 11, in which a catalyst material (20) to be replaced is removed from the cavities (18) and / or catalyst material (20) is introduced into the cavities (18).

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