Membrane reformer

Abstract

The invention relates to a membrane reformer for generating hydrogen, comprising a first cavity (1) with an inlet (8) for a reactant, where hydrogen and at least one additional reaction product are generated; a second cavity (3) located downstream of the first, where hydrogen and at least one other reaction product are generated, simultaneously separating the hydrogen by means of a membrane and introducing it into a third cavity; a third cavity (5) with an outlet (10) for the hydrogen; a membrane (4) placed on a perforated film (7) and installed between the second and third cavities (5) adjacent to the membrane or film; and an outlet (9) for the gas containing hydrocarbons, the additional reaction product, and the vapor from the second cavity (3).The membrane reformer consists of a stack of plates with multiple individual plates on both sides of the membrane, and the cavities are produced by depressions or perforations in at least one of the plates.

Description

[0001] The invention relates to a membrane reformer, preferably a palladium membrane reformer, and to its use for hydrogen production according to the first and 23rd claims.

[0002] Membrane reformers of the type mentioned above are used in particular for the production of hydrogen from hydrocarbon- or alcohol-containing gas and steam or ammonia. Their compact designs, in particular, enable decentralized deployment. Preferred applications are therefore found in supplying industrial customers with capacities below 500 Nm³ / h, where membrane reformer units represent a more cost-effective alternative to cylinders or cylinder bundles when hydrogen is supplied from the natural gas network. They thus offer an ideal hydrogen source for H₂ refueling stations or fuel cell systems for mobile or stationary applications.

[0003] The hydrocarbons that can be used include both gaseous substances, such as methane and propane, but also substances converted into the vapor phase, such as (bio)ethanol or higher molecular weight substances (hexadecane), as well as possible unsaturated or partially oxidized derivatives (alkenes, alcohols, acids, etc.).

[0004] Pure hydrogen is often needed in small quantities at many chemical and other industrial sites. Currently, production from methane (natural gas) is the most economical method. However, transport in gas cylinders or tank trucks is costly and unsustainable. Therefore, small, compact units with high power density and low investment costs represent a very attractive solution. The fuel cell market is also seeking cost-effective hydrogen supply options.

[0005] Another important business area and profitable segment is supplying hydrogen to industrial customers or hydrogen refueling stations. Since hydrogen transport is very expensive and the transported weight of hydrogen is very low, units with a capacity of up to 500 Nm³ / h for producing hydrogen via membrane reformers are worthwhile. The acquisition costs are recouped relatively quickly here, as natural gas incurs very few costs.

[0006] One goal of developments in membrane reformers is to simplify and improve the energy efficiency of hydrogen production from hydrocarbon-containing gas and water on the one hand, and to reduce the number of components and the size of the device for decentralized applications on the other.

[0007] EP 1 669 323 A1 discloses by way of example a microstructurable reactor and method for producing hydrogen from ethanol and water. The hydrogen is drawn off through a membrane and thus separated from the remaining reaction products. The reactor is formed by a stack of individual plates.

[0008] Membrane reformers can also be used to accelerate dehydrogenation, shifting the thermodynamic boundary conditions to allow for greater conversion with the separation of the resulting hydrogen. These dehydrogenations include applications for hydrogen storage based on liquid organic hydrogen carriers (LOHCs). In these applications, a particularly compact and dynamic operating mode with high volume-specific hydrogen release rates or reaction rates is desired, for example, to discharge the hydrogen into a pressure storage tank within a short time or to feed it directly into a fuel cell system.

[0009] EP 2 578 532 A1 discloses the use of a combustion zone, a reaction zone with an integrated membrane, and a hydrogen extraction zone. Sealing and connection are achieved via screw connections.

[0010] US 7,922,781 B1, like the aforementioned EP 1,669,323 A1, describes a device for hydrogen production with a combustion zone, a reaction zone with an integrated membrane, and a hydrogen extraction zone. Several process engineering requirements are also outlined; for example, the system is to be heated by the catalytic combustion of stored hydrogen until the ignition point of the catalyst for other substances is reached. The implementation of a multi-layer system with regard to substance distribution is not discussed.

[0011] The disadvantages of the aforementioned systems lie in their handling, the complex interchangeability of modules, and the limited purity of the separated hydrogen. In particular, the systems often require branches of the media that are arranged perpendicular to the flow direction in the individual modules.

[0012] Based on this, a Object of the inventionthe aim is to make a membrane reformer of the aforementioned type and its use for a simplified and energy-efficient production of pure hydrogen from hydrocarbon-containing gas and water safer and more efficient, while avoiding the aforementioned disadvantages.

[0013] The problem is solved by a membrane reformer and a use with the features of claim 1 or 23. Subclaims relating thereto describe advantageous embodiments.

[0014] A membrane reformer for hydrogen production is proposed. This reformer comprises a first cavity (pre-reforming zone, i.e., pre-reaction zone without a membrane) containing a catalyst and a feed for a gaseous, dehydrogenable reactant, preferably together with steam, in which the production of hydrogen and at least one other reaction product takes place. This is followed by a second cavity (preferably with a catalyst corresponding to, and more preferably to, the catalyst of the first cavity) in which the production of hydrogen and at least one other reaction product continues, with the generated hydrogen being simultaneously separated via a membrane and introduced into a third cavity, followed by a third cavity with an outlet for hydrogen.

[0015] Preferably, the gaseous dehydrogenable starting material is or contains a hydrocarbon, more preferably an alcohol, preferably methanol, ethanol and / or ammonia, and more preferably contains water vapor.

[0016] The membrane is made of a metallic material, containing a metal, or manufactured from metal. It is applied flat over a porous or perforated film or inserted between two porous or perforated films. The membrane is located between the second and third cavities, which are directly adjacent to the membrane or film.

[0017] Furthermore, the membrane reformer includes a drain for the hydrocarbon-containing gas, which carries at least one further reaction product and optionally water vapor from the second cavity.

[0018] The membrane reformer has a layered structure, meaning it is formed by a stack of plates with several individual plates (sheets, foils) on both sides of at least one membrane. The cavities are formed by depressions or openings in at least one plate.

[0019] The membrane reformer is therefore particularly suitable for miniaturization, where the plates preferably have a thickness of 10 to 2000 µm, more preferably 20 to 1000 µm, and even more preferably between 30 and 200 µm. The lateral dimensions of the preferably rectangular or square individual plates of such a micromembrane reformer are preferably between 10 and 300 mm, more preferably between 20, 30, or 40 and 60, 80, or 100 mm.

[0020] Each transition in the stack of plates—between two plates, or between a plate and a film or membrane, or between a membrane and a film—is formed by circumferential welds that seal around the cavities and / or inlets and outlets. The welds connect two adjacent layers, i.e., individual plates, membranes, and / or films. A weld preferably penetrates only one transition and the two adjacent layers. After the weld is completed, the next layer is placed on top, forming another transition, and is then welded to the adjacent layer by a further welding process. The circumferential weld advantageously creates a material transition between the two layers, thus forming a sealing barrier at the transition.It is essential that the welds between two adjacent transitions in the stack of plates are offset and not intersecting each other, i.e., they do not touch each other.

[0021] The type of construction of the connection technology using laser or electron beam welding advantageously enables a distortion-free or low-stress design of the membrane reformer, which ultimately allows individual modules with a planar membrane surface to be built and stacked into a complete package via seals through a membrane access arranged perpendicular to the zones, i.e., they can be individually replaced in case of defect.

[0022] One embodiment of the membrane reformer is characterized by a first cavity filled with particles of a catalyst for the conversion of the dehydrogenable reactant and / or having a wall or wall coating made of the catalyst. In this way, the conversion begins in the first cavity without any separation of hydrogen. This initially generates a hydrogen partial pressure in the direction of reaction. The conversion is sufficiently low to avoid causing equilibrium limitations in the reaction. This arrangement prevents any potential recirculation of hydrogen into the reaction mixture, which could occur if the entire reaction chamber were covered with a hydrogen-permeable membrane.

[0023] Another embodiment of the membrane reformer involves filling the second cavity with particles of a catalyst for the conversion of the dehydrogenable reactant and / or having a wall or wall coating made of the catalyst. The conversion process continues in the second cavity, while the membrane separation of hydrogen occurs in parallel. This separation lowers the hydrogen partial pressure in the gas phase, thus preventing further equilibrium limitations in the reaction. This allows for higher conversion rates of the dehydrogenable reactant.

[0024] The aforementioned catalyst for the conversion of the dehydrogenable starting material is or preferably contains platinum, palladium, nickel, and / or copper. More preferably, the catalyst has an increased specific surface area accessible for the conversion of the dehydrogenable starting material. This large surface area is preferably provided in the form of a fractured surface topography or open porosity, or, in the case of particles, alternatively or additionally, a small particle size, preferably between 10⁻¹ and 10⁻⁴ nm.

[0025] The membrane reformer is preferably further designed such that the second and third cavities, arranged on both sides above a membrane, span a common membrane area over the membrane and one or both films in a perfectly overlapping manner. This ensures that a maximum effective area is available for the transport of hydrogen through the membrane.

[0026] The film or films surrounding the membrane area preferably have a circumferential, dense area that is neither perforated nor porous. This ensures that any mass discharge, preferably formed by the hydrogen to be removed, is carried away exclusively via the membrane.

[0027] In an advantageous embodiment, the third cavity is additionally provided with an inlet for a purge gas. The use of purge gas reduces the hydrogen partial pressure in the third cavity. This increases the parameter range for the device's operation, as hydrogen can be discharged even at relatively low partial pressures. Advantageously, the hydrogen outlet also serves as an outlet for the purge gas. Furthermore, preferably, a predominant volume fraction of the third cavity is arranged between the outlet and the inlet.

[0028] For the cavities, particularly the first two cavities, temperature control devices, preferably a channel system for a temperature control fluid, are provided. This advantageously allows the temperature, and thus the reactions in the first cavity, to be controlled or limited upwards and / or downwards. The preferred channel system further preferably comprises recessed structures in at least one plate or film for the passage of a temperature control fluid and preferably has no fluidic connection to the aforementioned cavities, including the supply, return, and connecting lines.

[0029] Alternatively, in a further possible embodiment, the aforementioned temperature control agents comprise a catalytic combustion of the residual components of the dehydrogenable reactant contained in the effluent of the second cavity, of unseparated hydrogen and / or other combustible products on a suitable catalyst, wherein the catalyst is arranged in a channel system comprising recess structures in at least one single plate of the plate stack for the passage of the effluent of the second cavity mixed with air.

[0030] A preferred embodiment of the membrane reformer features inlets and outlets configured such that the membrane reformers can be connected and operated in parallel with other membrane reformers, preferably of the same design, to form a membrane reformer system. This embodiment includes inlets and outlets to and from the cavities, which open into and open into collecting channels. The collecting channels preferably penetrate the plates (films) of the plate stack orthogonally, with the plates being connected at the transition to the respective adjacent plates not only via sealing welds around the cavities and / or inlets and outlets, but also through the collecting channels. Crucially, the welds between two adjacent transitions are offset and do not intersect.If the collecting channels penetrate the entire stack of plates orthogonally, identical membrane reformers with the same dimensions can be stacked on top of each other, with the collecting channels of the respective planes aligned. One embodiment therefore provides that the collecting channels penetrate the stack of plates in a straight line and orthogonally to the plates.

[0031] Alternatively, it is advisable to at least arrange the outlets and inlets of the collection channels uniformly, particularly in the respective closing plates or foil panels.

[0032] A preferred embodiment also provides that at least one inlet and / or outlet from a cavity in a first plate into a collecting channel is provided by a breakthrough in a second plate and further by a groove-shaped depression in a third plate towards the collecting channel.

[0033] The membranes used in the membrane reformer are preferably between 1, 2, or 3 and 10, 20, or 40 µm thick. Preferably, in the aforementioned micromembrane reformer, the thicknesses are between 1 and 10 µm.

[0034] The membrane must be permeable to hydrogen, preferably with selective permeability. A membrane made of palladium or a palladium alloy is particularly suitable for this purpose. Alternatively, such a membrane may contain palladium or a palladium alloy. Preferably, the membranes are produced by a rolling or sputtering process. An alternative production method involves mounting the membrane on a porous (open-pore) or perforated film as a support substrate (backing plate), preferably by direct vapor deposition onto the film via a sputtering process or, alternatively, by chemical deposition. The porous or perforated film is made of a metal and is preferably between 30 and 200 µm thick.

[0035] The cavities in the stack of plates are preferably arranged one above the other and each extends rectangularly within a plate, preferably as depressions or openings in the plates. Furthermore, the inlets and outlets are preferably slot-shaped and each spans a predominant portion of one side of a rectangular cavity.

[0036] A particular advantage of the described structure and the aforementioned designs within a stack of individual plates lies in the miniaturization and in the interconnection of a large number of small and therefore thermally well-controlled membrane reformers to form membrane reformer systems.

[0037] The invention is explained in more detail with reference to exemplary embodiments, the following figures, and descriptions. The features shown and their combinations are not limited to these exemplary embodiments and their configurations. Rather, they can be combined to represent further possible configurations that are not explicitly shown as exemplary embodiments. Fig. 1 a schematic diagram of a membrane reformer, Fig. 2 Principled exploded views showing all plates of a plate stack of an embodiment of a membrane reformer in two perspectives, Fig. 3 Principled exploded views showing all plates of a plate stack of another embodiment of a membrane reformer in two perspectives, Fig. 4 a perspective view of a design of a perforated film as a support substrate (support plate) for the membrane as well as Fig. 5A representation from a reaction of methane with steam: methane conversion X CH4 as a function of the hydrogen recovery rate φ H2 for eight different operating points.

[0038] The basic structure of an exemplary membrane reactor and the material flows within it are shown. Fig. 1 in a basic cross-sectional representation.

[0039] The membrane reformer essentially comprises a first cavity 1 as a pre-reforming stage, which follows a flow deflection 2 into a second cavity 3 transitioning to a reform stage, a third cavity 5 as well as a hydrogen-permeable membrane arranged between the second and third cavities 4. The first and second cavities also feature a catalyst layer away from the membrane. 6 on the walls of the cavity. The membrane itself is sandwiched between two perforated films. 7used as support substrates (support plates).

[0040] Through an inlet 8 A gaseous, dehydrogenable reactant, in this example CH₄ and H₂O, is introduced into the first cavity. Pre-reformation takes place in the first cavity, i.e., the reactant begins to react with hydrogen and another product under the influence of the aforementioned catalyst. As the reaction progresses, the reaction mixture is then passed through the flow deflector into the second cavity. 3 and thus also to the membrane 4, in which the reaction continues, but at the same time the hydrogen formed passes across the membrane into the third cavity 5 is transferred. While a residual portion of hydrogen (H₂), an unreacted residue of the reactant (CH₄, H₂O, i.e., hydrocarbon-containing gas), and the other reaction products (CO, CO₂) are transferred via a drain. 9Hydrogen (H2) is extracted from the second cavity via an outlet. 10 from the third cavity.

[0041] Furthermore in Fig. 1 A channel is shown. 11, In this process, a fuel (e.g., CH₄) is introduced along with oxygen (O₂), where it is oxidized (particularly to CO₂ and water) with the generation of heat and discharged to the right out of the channel. The heat generated in this process serves as a temperature control medium for the membrane reformer; that is, it is transferred via the channel wall, particularly to the aforementioned cavities. Preferably, there is no fluidic connection between the channel and any of the cavities.

[0042] Preferred embodiments of the membrane reformer realized by a stack of plates can be found in Fig. 2 and 3 as exploded views from a top-down (left) and a bottom-down (right) angle. These are particularly evident in Fig. 2The arrows shown on the left represent the material flows in the membrane reformer. The sheets of the plate stack are preferably made of corrosion-resistant steel and preferably have the same external dimensions, with the lateral extents and the arrangements of the first, second, and third cavities on the respective sheets preferably being identical.

[0043] Fig. 2 represents an embodiment without a temperature control agent, while Fig. 3 These tempering agents are contained in separate additional films.

[0044] A description of the individual sheets (individual plates) of the stack of plates follows, starting with the bottom sheet: The bottom closing slide 12 This is a sealing closure at the bottom of the membrane reformer. It has only one inlet. 8 for a gaseous dehydratable reactant from a first collecting channel penetrating all films 13as well as part of the process 9 for a residual portion of hydrogen, an unreacted residue of the reactant, and the other reaction products into a second collecting channel penetrating all the films. 14 The inlet and outlet are represented as groove-shaped depressions on the lower end sheet. Furthermore, an outlet, also penetrating all sheets, is present on each side. 10 for hydrogen from the third cavity and a purge gas channel 20 The lower sealing foil is for the supply of a purge gas into the third cavity. The pre-reforming foil 15The first cavity, preferably a rectangular, planar depression, has a section into which the aforementioned inlet preferably opens along one entire end face. The walls of the cavity are preferably coated with a catalyst of the aforementioned type. On the end face opposite the inlet, the first cavity opens into the flow deflector, thus achieving a flow cross-section that is as uniform as possible within the cavity. The reforming foil follows. 16 The second cavity also has walls coated with catalyst. As in the first cavity, the reaction mixture is introduced through one end face from the flow deflector and discharged through the opposite end face via the outlet. 9The flow is diverted, thus ensuring a uniform flow cross-section. The reforming foil is perforated with a foil that is preferably only open in the area extending to the second cavity. 7 The membrane is covered with support substrates (support plates). The membrane rests on the perforated film. 4 preferably extending – as shown – only over the second and third cavities and not over the aforementioned collecting channels. Preferably, the membrane is – as also shown – between the aforementioned perforated film. 7 and a second perforated foil 17 arranged. The hydrogen removal foil follows. 18 with the foil that was elaborated as a recess and perforated to form the second foil 17 pointing third cavity 5, the one towards the membrane spans the same area as the second cavity. The following deflection foil 19and the top closing slide 21 They serve in particular to deflect the purge gas from the purge gas channel. 20 into the third cavity and the deflection of the purge gas with the hydrogen separated by the membrane from the third cavity into the outlet 10. The deflection foil 19This advantageously enables the preferably proposed connection of the films to one another, wherein each transition in the plate stack between two plates, or between a plate and a film or membrane, or between a membrane and a film, is formed by weld seams that seal around the cavities and / or inlets and outlets, and the weld seams between two adjacent transitions in the plate stack are offset and not intersecting each other. The deflections themselves are essentially represented as recesses on the underside of the upper end film. Preferably, the openings of the lower and upper end films are congruent, so that a parallel connection of several membrane reformers can be realized by arranging them one above the other.

[0045] Fig. 3 It also shows three further slides, which cover the temperature control agents for the membrane reformer. In contrast to Fig. 1are these not directly adjacent to the pre-reforming stage (first cavity) 1) , but above the top closing slide 21 i.e. adjacent to the third cavity 5 arranged. Above the top finishing slide 21 is a combustion chamber foil 22 arranged in which a combustion chamber 23 The combustion chamber is formed as a recess. The lateral extent of the preferably cuboid-shaped combustion chamber on the combustion chamber foil preferably corresponds to that of the aforementioned cavities. Furthermore, a fuel gas inlet, preferably opening across an entire end face of the combustion chamber, is provided. 24 for a preferably gaseous fuel gas and an exhaust gas outlet preferably opening onto the opposite end face of the combustion chamber 25 provided, wherein fuel gas inlet and exhaust gas outlet are each fluidically designed, preferably as groove-shaped depressions, to a fuel gas collection channel 26or exhaust gas collection channel 27 are connected. The fuel gas collection channel and exhaust gas collection channel preferably penetrate all the sheets of the plate stack, preferably orthogonally to the sheets, as previously described for the collection channels for reactants and reaction products. Onto the combustion chamber sheet 22 is an air distribution film 28 with a distribution volume introduced as a depression at the top 29 arranged. The flat air distribution foil at the bottom preferably closes off the combustion chamber. 23 The forming depression slopes upwards. The extent of the distributor volume corresponds to that of the combustion chamber located below it. Air passages 30 The distributor volume, extending across its entire length to the combustion chamber, allows for an air supply across the entire combustion chamber volume, thus ensuring even combustion within the combustion chamber. The distributor volume is fluidically connected (via a groove-shaped depression) to an air collection channel. 31connected, which in turn preferably penetrates all the films of the plate stack, preferably orthogonally to the films. Above the air distribution film 28 is an upper tempering agent cover film 32 provided for, which in the example limits the distribution volume upwards.

[0046] In Fig. 2 and 3 There are also various welding lines on the foil. 33 The weld lines shown are preferably formed by laser welding. The weld lines indicate the lines that are preferably also traversed by the laser beam of the welding system. The welds along the weld lines preferably connect the transition between two films, in the illustrated embodiments connecting each film to the adjacent film located below it (more preferably excluding perforated films). 7 and 17as well as the membrane). Every transition in the plate stack between two plates, or between a plate and a film or membrane, or between a membrane and a film, through the cavities and / or inlets and outlets, is sealed to the outside by one of the circumferential weld seams. A key feature of this preferred embodiment of the joining technique is that the weld lines of two adjacent transitions do not cross, intersect, or otherwise overlap. Consequently, the weld seams between two adjacent transitions in the plate stack are offset and do not intersect each other.

[0047] Inside the membrane reactor, the circumferential weld lines are used to create a seal from the inside out and between the individual films. The welding is preferably carried out with a laser beam perpendicular to the individual films.

[0048] In particular, overlapping weld lines are avoided. For superimposed plates that have a penetration or circumferential sealing groove, an alternating sequence of smaller and larger radii of the circumferential groove (with otherwise identical groove dimensions) is implemented to prevent the weld root from encountering the groove of the weld below, thus ensuring reliable sealing and compressive strength.

[0049] Furthermore, the welding of the arrangement of plates, starting from the central plate with the membrane, is preferably carried out alternately from both sides in order to minimize distortion and to ensure planar parallelism for the films in the plate stack.

[0050] A preferred welding sequence for a Fig. 2 The depicted design of the membrane reformer is: Connection of the transition between pre-reformation foil 15 and reform foil 16,subsequent welding of hydrogen removal foil 18 through the underlying foils down to the reforming foil 16 (i.e., welding several transitions simultaneously); then attaching the lower finishing foil. 12 from below; finally, the deflection foil is attached. 19 and then the top closing slide 21.

[0051] For a joining of the foils of a in Fig. 3 The illustrated embodiment preferably refers first to the aforementioned sequence, followed by the foil-wise application and welding of the foils for tempering (combustion chamber foil). 22, Air distribution film 28 and tempering agent cover film 32 ) , where only one transition is welded at a time.

[0052] A key element of the design concerns the deflection foil. 19,which allows a common connection point for hydrogen extraction (channel) 10 ) and to the purge gas channel 20 to produce on the foils without the purge gas passing from the purge gas channel to the channel away from the third cavity 5 on the underside of the hydrogen removal foil 18 can take place.

[0053] Further advantages lie in the flow guidance in the first and second cavities. For example, pre-forming in the pre-forming foil enables 15 The build-up of a hydrogen partial pressure through reaction prior to contact with the membrane. The flow deflection. 2 The space between the first and second cavities again represents a flow resistance. This promotes a uniform flow across the frontal area into the second cavity and, on the other hand, hinders the backflow of fluid components from the second cavity back into the first cavity.

[0054] The membrane 4 is on both sides made of a perforated film 7 and 17 (preferably 50 µm thick and provided with 70 µm perforations) framed for stabilization. Preferably, the outer dimensions of the perforated films correspond to those of the other films of the membrane reformer. More preferably, the perforations extend laterally onto the membrane and / or only in the area of ​​the second and third cavities, while the remaining area has no perforations.

[0055] Preferably, a non-porous edge of an open-pore membrane support (film) 7 and 17 ) ensures the membrane is sealed to the outside. The Pd-containing membrane film (preferably made of Pd or PdAg) is preferably only 3 to 20 µm thick (rolled or sputtered). One embodiment provides for the membrane to be applied directly to at least one of the open-pore films. 7 or 17To build: first, a ceramic porous layer as a diffusion barrier for metal atoms into the palladium; then, deposition of Pd or its alloys by various means, e.g., sputtering, electroless deposition, electrochemically, or via suspension plasma spraying.

[0056] An alternative design of the slides 7 and 17 The membrane is made possible by a laser sintering process, in which a dense edge is created. 34 is brought into the shape of the reactor shown above ( Fig. 4 A key aspect of this design is that the laser sintering takes place in the inner open-pore area. 35 a structure of additional groove-shaped channels 36This allows for channels that can simultaneously be used as hydrogen removal channels, i.e., as part of the third cavity. A coating with membrane material or the application of a membrane is then possible on both the top and bottom surfaces of the depicted film, making the reformer even more compact. It is important that the channels also extend across the porous area. 35 and the weld line 33 out into the dense border 34 continue and in a slot 37 etc. end so that the separated hydrogen from the various modules can be collected.

[0057] Fig. 5This graph shows experimental results from the reaction of methane with steam (methane conversion rate X CH4 [%]) as a function of the H2 recovery rate φ H2 [%] for eight different operating points. The lines represent calculated equilibrium conditions. Experimental values ​​are shown at pressures of 6, 8, 10, and 12 bar (from left to right) at 773 K (black filled symbols) and 823 K (white filled symbols), a constant W / F ratio of 0.33 g Cat h / mol CH4, and an S / C ratio of 3. Here, S / C indicates the molar ratio of steam to carbon (in the methane). W / F is the ratio of catalyst mass to methane molar flow rate. Reference symbol list:

[0058] 1 First cavity 2 Flow deflection 3 Second cavity 4 Membrane 5 Third cavity 6 Catalyst layer 7 Perforated foil 8 Inlet 9 Outlet 10 Exhaust 11 Channel 12 End foil 13 First collecting channel for reactants 14 Second collecting channel for reaction products 15 Pre-reforming foil 16 Reforming foil 17 Second perforated foil 18 Hydrogen removal foil 19 Deflection foil 20 Purge gas channel 21 End foil 22 Combustion chamber foil 23 Combustion chamber 24 Fuel gas inlet 25 Exhaust gas outlet 26 Fuel gas collecting channel 27 Exhaust gas collecting channel 28 Air distribution foil 29 Distribution volume 30 Air passages 31 Air collecting channel 32 Temperature control cover foil 33 Weld lines 34 Tight edge 35 open-pore area 36 grooved channels 37 oblong hole

Claims

1. Membrane reformer for generating hydrogen, comprising a) a first cavity (1) with a catalyst and a feed (8) for a gaseous dehydrogenatable reactant, in which hydrogen and at least one other reaction product is generated, b) a second cavity (3) arranged downstream of the first cavity and in which hydrogen and at least one other reaction product are further generated while simultaneously separating the generated hydrogen via a membrane and introducing same into a third cavity, c) a third cavity (5) with a discharge (10) for hydrogen, d) a membrane (4) made of a metallic material, containing a metal or made of metal and placed flat over a porous or perforated film (7) or inserted between two porous or perforated films (7, 17) and inserted between the second and third cavity (5), each of which directly adjoins the membrane or film, e) a discharge (9) for the hydrocarbon-containing gas, the at least one further reaction product and water vapour from the second cavity (3), f) wherein the membrane reformer is made of a plate stack with multiple individual plates on both sides of the at least one membrane, and g) wherein the cavities are formed by means of depressions or perforations in, in each case, at least one plate, wherein h) each transition in the plate stack between two plates or between one plate and a film or membrane or between a membrane and a film is formed by weld seams forming a seal around the cavities and / or feed and outlet lines, and i) the weld seams are offset between two adjacent transitions in the plate stack and are arranged not to cross each other.

2. Membrane reformer according to claim 1, characterised in that the first cavity is filled with particles of the catalyst for the conversion of the dehydrogenatable reactant and / or a wall or wall coating consists of the catalyst.

3. Membrane reformer according to claim 1 or 2, characterised in that the second cavity is filled with particles of a catalyst for the conversion of the dehydrogenatable reactant and / or a wall or wall coating consists of the catalyst.

4. Membrane reformer according to one of the preceding claims, characterised in that the catalyst for the conversion of the dehydrogenatable reactant contains platinum, palladium, nickel and / or copper.

5. Membrane reformer according to one of the preceding claims, characterised in that the second and third cavities arranged in each case over a membrane on both sides, span and fully overlap a common membrane area over the membrane and the one film or both films.

6. Membrane reformer according to one of the preceding claims, characterised in that the one film or both films around the membrane area have a peripheral sealed area which is neither perforated nor porous.

7. Membrane reformer according to one of the preceding claims, characterised in that a feed is provided for a purge gas into the third cavity and the discharge for hydrogen is at the same time also a discharge for the purge gas.

8. Membrane reformer according to claim 7, characterised in that a predominant volume portion of the third cavity is arranged between the discharge and feed.

9. Membrane reformer according to one of the preceding claims, characterised in that temperature control means are provided for the first cavity.

10. Membrane reformer according to claim 9, characterised in that the temperature control means is formed by a channel system, comprising depression structures in at least one plate for the passage of a temperature control fluid.

11. Membrane reformer according to claim 9, characterised in that the temperature control means comprise a catalytic combustion of the remaining fractions of the dehydrogenatable reactant contained in the discharge of the second cavity, from non- separated hydrogen and / or other combustible products on a suitable catalyst, wherein the catalyst is arranged in a channel system, comprising depression structures in at least one of the individual plates of the plate stack for the passage of the discharge of the second cavity mixed with air.

12. Membrane reformer according to one of the preceding claims, characterised in that a) the feeds and discharges to and from the cavities start and end in collector channels, b) the collector channels go through the plates of the plate stack and c) the plates in the transition to their respective adjacent plates are connected to the respective adjacent plates or membranes not only via the weld seams forming a seal around the cavities and / or feed and discharge lines, and also by the collector channels, d) wherein the weld seams are offset between two adjacent transitions and arranged not to cross each other.

13. Membrane reformer according to claim 12, characterised in that at least one feed and / or discharge from a cavity in a first plate takes place in a collector channel through a perforation of a second plate and further through a groove-shaped depression in a third plate to the collector channel.

14. Membrane reformer according to claim 12 or 13, characterised in that the collector channels perforate the plate stack in a straight line and orthogonally to the plates.

15. Membrane reformer according to one of the preceding claims, characterised in that the membrane is between 3 and 20µm thick.

16. Membrane reformer according to one of the preceding claims, characterised in that the permeability of the membrane is selective for hydrogen.

17. Membrane reformer according to claim 16, characterised in that the membrane is made of palladium or a palladium alloy or contains palladium or a palladium alloy.

18. Membrane reformer according to claim 16 or 17, characterised in that the membrane is made by a rolling or sputtering process.

19. Membrane reformer according to one of claims 16 to 18, characterised in that one of the films is porous and the membrane is sputtered via a sputtering process or deposited by a chemical process directly onto the film.

20. Membrane reformer according to one of the preceding claims, characterised in that the one or two porous or perforated films are made of metal and are between 30 and 200µm thick.

21. Membrane reformer according to one of the preceding claims, characterised in that the cavities are arranged one over the other in the plate stack, extend in each case rectangularly in a plate, and the feeds and discharges are slot-shaped and each span the predominant portion of one side of a rectangular cavity.

22. Membrane reformer system comprising a plate stack with at least two membrane reformers arranged one over the other in the plate stack according to one of the preceding claims.

23. Use of a membrane reformer according to claim 1 for the generation of hydrogen, characterised in that the gaseous dehydrogenatable reactant contains water vapour.

24. Use of a membrane reformer according to claim 1 for the generation of hydrogen, characterised in that the dehydrogenatable reactant is or contains hydrocarbon.

25. Use of a membrane reformer according to claim 1 for the generation of hydrogen, characterised in that the dehydrogenatable reactant is or contains an alcohol, preferably methanol or ethanol.

26. Use of a membrane reformer according to claim 1 for the generation of hydrogen, characterised in that the dehydrogenatable reactant is or contains ammonia.

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