LOHC reactor and use of a porous, open-pore substrate catalytically coated on at least one side

Abstract

LOHC reactor for hydrogenating an organic carrier liquid - with a carrier liquid inlet (2) for supplying carrier liquid to be hydrogenated, a carrier liquid outlet (10) for removing the hydrogenated carrier liquid and a flow path connecting the carrier liquid inlet (2) to the carrier liquid outlet (10), - with at least one reaction chamber (5) through which the carrier liquid flows, which is delimited at least in part by a catalytically coated substrate (8), - with a hydrogen supply (7) for supplying hydrogen into the at least one reaction chamber (5) and - with means for providing a temperature required for the catalytic reaction, characterized in that the substrate (8) with its catalytic coating is porous and open-pored on its side facing into the reaction space (5).

Description

[0001] The invention relates to a LOHC reactor for carrying out a catalytic hydrogenation of an organic carrier liquid having the features of the preamble of claim 1 and for carrying out a catalytic dehydrogenation of an organic carrier liquid having the features of the preamble of claim 2. The invention further relates to the use of a porous, open-pore substrate which is catalytically coated on at least one side.

[0002] Hydrogen is becoming increasingly important as an energy carrier in the context of decarbonizing energy production. Its storage and transport are not entirely without challenges. Conventionally, pressure vessels are used for these purposes, in which hydrogen is stored at pressures of up to 700 bar. Alternatively, cryogenic tanks are also an option. Pipelines are also used for hydrogen transport, sometimes relying on existing gas pipeline networks, which must be appropriately prepared for hydrogen transport due to hydrogen's volatility.Since these options for storing and transporting hydrogen have disadvantages, which are also significant safety-relevant aspects when using pressure vessels, and in the case of hydrogen pipelines, their lack of leak-tightness, recent research has been initiated into hydrogen storage in a carrier fluid. Liquid organic hydrogen carriers are used as carrier fluids, which can absorb and release hydrogen through a chemical reaction. This allows storage at ambient pressure and transport in conventional tank containers. Liquid organic hydrogen carriers are also referred to as LOHCs (Liquid Organic Hydrogen Carriers).

[0003] The reactions of hydrogenation of the carrier liquid with hydrogen and its dehydrogenation are carried out in the presence of a catalyst, for example, one doped with platinum. Furthermore, both the hydrogenation and dehydrogenation reactions require elevated temperatures. Even though the hydrogenation reaction is generally exothermic, a certain starting temperature is required to initiate it. Furthermore, the hydrogenation reaction is carried out at elevated pressure, which is sometimes also useful for the dehydrogenation reaction. The temperatures and pressures required for the reactions depend on the respective system, particularly the carrier liquid used. The hydrogenation reaction is typically carried out at a lower temperature but at a higher pressure than the dehydrogenation reaction, which is carried out at a higher temperature but at a lower pressure.

[0004] The catalytic reactions are carried out in a LOHC reactor. The LOHC reactors for the hydrogenation and dehydrogenation reactions can differ in terms of their design and the catalysts used. LOHC reactors have also been developed in which both reactions can be carried out.

[0005] The effectiveness of such hydrogen storage depends on the course of the catalytic reactions. This determines the achievable degree of hydrogenation as well as the degree of dehydrogenation that can be achieved when the carrier fluid passes through the reactor. To increase efficiency, several LOHC reactors can be cascaded.

[0006] The chemical reactions take place on the catalytic surface contacted by the carrier fluid, whereby hydrogen must be present at the catalytic surface during the hydrogenation of the carrier fluid. Tube bundle reactors, for example, are used as LOHC reactors. Catalyst pellets are arranged between the individual tubes through which a heat transfer medium flows, and the carrier fluid flows around them. A disadvantage of such LOHC reactors is that the catalyst pellets in the respective reaction chamber cause a relatively high flow backpressure for the passing carrier fluid. In addition, heat transfer from the shell surface of the tubes to the catalyst pellets is sometimes insufficient, so that the temperature is not uniform across the cross-sectional area of ​​such a catalyst chamber and is typically lower in the flow center than at the walls surrounding such a reaction chamber.To achieve sufficient heating of the pellets located in the center of such a reaction chamber, the heat input must be sufficiently high. It is also important to consider that the carrier fluid flowing through such a reaction chamber dissipates heat and thus cools the catalyst pellets.

[0007] In addition to such LOHC reactors, reactors designed according to the principle of plate heat exchangers are also used. In order to enlarge the surfaces in contact with the carrier fluid for the catalytic coating, it has been proposed to use aluminum as the wall material and then laser-process these surfaces into a foam-like structure. While this measure can provide a fairly large surface area for subsequent coating with the catalyst, the laser processing is complex, especially when larger wall segments are to be processed. Furthermore, this principle has so far only been implemented on aluminum surfaces. Aluminum is a good heat conductor when heat is applied to the outer shell to heat the catalytic surface and the carrier fluid to the appropriate reaction temperature.However, compared to other materials, and especially in relation to its production, aluminum is expensive and energy-intensive. In LOHC reactors constructed according to the plate heat exchanger principle, the catalyst is located on the wall bordering a reaction chamber, past which the carrier fluid flows. Thus, unlike a tube-bundle reactor, hydrogenation or dehydrogenation of the carrier fluid does not occur across the entire cross-sectional area of ​​the carrier fluid flow.

[0008] Various organic liquids can be used as carrier fluids. One possible compound is dibenzyltoluene.

[0009] Based on this discussed prior art, the object of the invention is to propose an improved LOHC reactor which, as a substrate, not only offers greater freedom in the choice of material despite the large surface area on its catalytically coated side, but also promises a higher degree of hydrogenation or dehydrogenation per unit time.

[0010] This object is achieved according to the invention by a LOHC reactor having the features of claims 1 or 2, depending on whether the LOHC reactor is intended for hydrogenating or dehydrogenating a carrier liquid. It is understood that each of these two LOHC reactors can be designed to be used both for hydrogenating a carrier liquid and for dehydrogenating a hydrogenated carrier liquid.

[0011] The increased effectiveness compared to previously known LOHC reactors is due to the use of a porous, open-pore substrate as the catalytically coated substrate. This substrate is porous throughout and thus permeable to media, particularly from one side to the other. The increased efficiency lies primarily in the extremely large catalytically active surface provided by such a substrate and the capillary action caused by its porosity, through which the carrier fluid is drawn at least into the peripheral section on the reaction chamber side. Ceramic materials such as cordierite or silicon carbide are suitable materials for the porous substrate. In addition to ceramic materials, sintered metal material is particularly suitable for forming the porous substrate for an LOHC reactor. Such materials are known from filter technology.The use of sintered metal material—that is, sintered metal particles bonded to form a sintered metal layer, for example, in the form of a circuit board—as a porous substrate offers the significant advantage that different metals or metal mixtures can be used to produce this substrate. Furthermore, the particle size, pore size, and pore volume of the sintered metal material to be produced can be easily adjusted.

[0012] Regardless of whether a ceramic material or a sintered metal material is used as the porous substrate, for example, a material otherwise used in filter technology, such as exhaust gas purification, these materials inherently already have a very large surface area. Therefore, the active surface area available for carrying out the desired reactions is correspondingly large if such a substrate is catalytically coated on its side facing the reaction chamber or carries a catalytically active component. Due to the pore size of such materials, the available surface area of ​​the pure, porous substrate is smaller than that of a previously described, laser-structured component, but this is not particularly significant due to the additional preparation steps.In a particularly preferred embodiment of such a porous substrate, ceramic materials and sintered metal materials are coated with a washcoat, sometimes even before the catalytically active component is applied. Such a washcoat serves the purpose of significantly increasing the already large surface area of ​​such a material. This concept cleverly utilizes the pore volume and pore size of such materials for the application of a washcoat in such a way that the pores are not clogged by a washcoat coating and the substrate does not lose its continuous, open-pore porosity.This is not possible due to the very small pore size of laser-textured aluminum components. The surface-enhancing particles in such a washcoat seal the textures introduced by laser processing, essentially negating the previous achievements of the laser texturing. This allows such a porous substrate to be equipped as a catalyst support with a significantly larger catalytically active surface area than conventional catalysts used for this purpose.

[0013] The pore size and pore volume, which extend through the porous substrate transversely to its contact side with the carrier liquid, limit contact of its catalytic surface with the carrier liquid not only to the contact side directly facing the reaction chamber; it is also catalytically active within the porous substrate, at least to the extent that the catalytic coating has penetrated it. The pore size and pore volume of such materials are sufficiently large that a washcoat application and a catalytic coating are not limited to the upper layer of the particles of the porous substrate.

[0014] In contrast to previously known catalyst supports used for the chemical reactions in a LOHC reactor, the catalytically coated porous substrate can be used in the LOHC reactor for media separation, whereby, depending on the design of the LOHC reactor, one of the two media – hydrogen or carrier liquid – can still pass through the porous substrate. In an LOHC reactor for hydrogenating a carrier liquid, according to one embodiment, at least one reaction chamber is separated from a hydrogen collector into which the hydrogen supply flows. During operation of such a reactor, a higher pressure prevails in the hydrogen collector than on the other side of the porous substrate – the reaction chamber – so that the hydrogen passes through the porous substrate and is fed to the carrier liquid located or flowing on the other side.In this way, the hydrogen is fed into the carrier liquid in extremely fine bubbles, which in turn improves the conversion rate due to the large hydrogen surface created in this way.

[0015] In a reactor used to dehydrogenate a hydrogenated carrier liquid, the flow-through functionality of the catalytically coated porous substrate can be used to separate the hydrogen released from the carrier liquid from the carrier liquid directly at the site of dehydrogenation, namely at the catalytic surface of the porous substrate. Depending on the design of such a reactor, the hydrogen can either be separated from the carrier liquid by passing through the porous substrate without the carrier liquid passing through the porous substrate itself, or the carrier liquid to be dehydrogenated can be passed through the porous substrate.

[0016] The porous, open-pore substrate supporting the catalytic component can also be applied to a carrier material, for example, a carrier film designed to complete the catalyst of a LOHC reactor. In this case, the porous, open-pore substrate is located, for example, on the side of a heat exchanger facing the reaction chamber, typically designed as a plate heat exchanger.

[0017] The advantage of using sintered material to form the porous substrate as a catalyst support is that this material can be designed to be self-supporting even with a small layer thickness. Since the chemical reactions only take place on the catalytically coated surface, the layer thickness of such a porous substrate does not need to be particularly large. 0.3 to 2.5 mm is considered sufficient. According to a preferred embodiment for providing a self-supporting, permeable sintered metal material, a mesh-like sintered metal support is used, into the openings of which the metal powder is incorporated before this composite is sintered. Such a mesh-like sintered metal support can be, for example, an expanded metal plate or a wire mesh.The metal powder used to produce such a sintered metal material can be the one used to produce sintered metal diesel particulate filters.

[0018] In an advantageous development, the catalytically coated porous substrate is electrically heated or heatable. In the case of a porous substrate made of ceramic material, this can be achieved by incorporating electrical resistance heating elements, such as resistance heating wires. If the catalytically coated substrate is made of sintered metal material, this can itself be used as a resistance heating element. Providing such a heater as a means of providing the temperature required for the catalytic reaction is highly energy-efficient. By integrating the heating means into the porous substrate or by providing the porous substrate as the heating means, heat is only generated where it is needed. In comparison, introducing heat from outside into the reaction chamber of a LOHC reactor is much more energy-intensive.

[0019] If a LOHC reactor is to be used for both reactions—hydrogenation and dehydrogenation—it is possible to use different catalysts for the two different processes. This does not mean that the porous substrates in such a LOHC reactor would have to be replaced. Rather, the special properties of such a porous, open-pore substrate can be utilized in this regard, requiring only a change in the media flow in the LOHC reactor. The porous substrate carries the catalyst intended for the hydrogenation reaction on one side and the catalyst desired for the dehydrogenation reaction on the opposite side. It goes without saying that both sides of such a porous substrate can also be equipped with the same catalyst.

[0020] When using sintered metal material, its forming properties can be utilized to increase its surface area through appropriate shaping. This can be achieved, for example, by corrugating or pleating the sintered metal material. Other surface-enlarging forming structures are also possible, such as the formation of a labyrinth in the flow path of the carrier fluid in the at least one reaction chamber.

[0021] The invention is described below with reference to exemplary embodiments in the accompanying figures. They show: Fig. 1: A schematic representation of an LOHC reactor according to the invention, designed to carry out a hydrogenation of an organic carrier liquid, Fig. 2: a highly magnified section of a section of a catalytically coated porous substrate defining a reaction space in which the hydrogenation reaction takes place, and Fig. 3: another LOHC reactor according to the invention, designed for a dehydrogenation process.

[0022] Fig. Figure 1 shows a schematic sectional view of a LOHC reactor 1. The LOHC reactor 1 has a carrier liquid inlet 2 through which the carrier liquid to be hydrogenated is introduced into the LOHC reactor 1. This organic carrier liquid to be loaded with hydrogen is in Fig. 1 as LOHC -The carrier liquid supply flows into a carrier liquid inlet collector 3 within the LOHC reactor 1. In the carrier liquid inlet collector 3, the supplied carrier liquid is distributed over the cross-sectional area of ​​the LOHC reactor 1. The carrier liquid inlet collector 3 borders a reaction section 4 in the LOHC reactor 1. The reaction section 4 has a plurality of cylindrical reaction chambers 5. The reaction chambers 5 are arranged at a distance from one another and distributed over the cross-sectional area of ​​the LOHC reactor 1. Between the reaction chambers 5 there is a hydrogen collector 6, which is supplied with hydrogen via a hydrogen supply 7. The reaction chambers 5 are each separated from the hydrogen collector 6 by an annular porous substrate 8, which is catalytically coated on its side facing into a reaction chamber 5.The flow direction of the carrier liquid between the carrier liquid inlet 2 into the carrier liquid inlet collector 3 and from there into the individual reaction chambers 5 is indicated in the figure by block arrows. Thus, the reaction chambers 5 open with the outlet at one end into the carrier liquid inlet collector 3. With the outlet at the other end, the reaction chambers 5 open into a carrier liquid outlet collector 9, from which the hydrogen-laden carrier liquid is discharged via a carrier liquid outlet 10. The hydrogen-laden carrier liquid is designated LOHC in the figure. + This carrier fluid can be fed, for example, to a storage vessel via the carrier fluid outlet 10.

[0023] The tubular porous substrate used in the illustrated embodiment is a sintered metal material with a sintered metal carrier, specifically an expanded metal, incorporated therein. On the inner side facing into a reaction chamber 5, the sintered metal material is provided with a washcoat, which further increases the already large inner surface of this material. The washcoat itself carries a catalytically active component. Thus, the inner surface of these porous, open-pore substrates 8 is enormously high.

[0024] The individual catalytically coated porous substrates 8 are, as indicated in the figure, electrically heatable, with the substrate 8 itself representing the resistance heater. The temperature required for incorporating hydrogen into the carrier liquid is generated by heating the catalytically coated substrates 8. In order to reduce the temperature difference on the carrier liquid caused by the heated substrates 8, and thus to enable the longest possible flow path of the carrier liquid through the reaction chambers 5 with the hydrogenation reaction taking place, the carrier liquid to be hydrogenated is introduced in a heated state into the carrier liquid inlet collector 3 and / or preheated therein to a temperature that is below the temperature intended for the reaction to proceed.Heating of the carrier liquid to the desired reaction temperature on the catalytically coated porous substrates 8 is then correspondingly shorter; this temperature can thus be raised almost spontaneously. The carrier liquid is pumped through the LOHC reactor 1 at a low pressure of, for example, 2 to 3 bar. Once sufficient carrier liquid has been introduced into the LOHC reactor 1 through the carrier liquid inlet 2 to fill the reaction chambers 5 and the substrates 8 have reached the reaction temperature, hydrogen is introduced into the hydrogen collector 6 via the hydrogen supply 7, or the pressure therein is increased, so that the pressure in the hydrogen collector 6 is greater than that in the reaction chambers 5. In the illustrated embodiment, a pressure of 5 bar prevails in the hydrogen collector 6 during operation of the LOHC reactor 1.

[0025] In the illustrated embodiment, the porous substrates 8 are used for media separation between the hydrogen contained in the hydrogen collector 6 and the carrier liquid contained in the reaction chambers 5. Since the porous substrate 8 is porous throughout from its outer side to its inner side, the pressure prevailing in the hydrogen collector forces hydrogen into and through the porous substrate 8, so that the hydrogen comes into contact with the catalyst and the carrier liquid on the catalytically coated side of the porous substrate 8.

[0026] Fig. 2 shows an enlarged view of a section of the porous substrate 8 in a schematic sectional view, wherein the substrate 8 points with its one side 11 into the hydrogen collector 6 and with its other side 12 delimits a reaction chamber 5. The side 12 of the substrate 8 is the catalytically coated side of the substrate 8. Due to the excess pressure prevailing on the side of the hydrogen collector 6 compared to that in the reaction chamber 5, carrier liquid is prevented from passing through the porous substrate 8. Nevertheless, a not inconsiderable capillary effect can be observed, which causes carrier liquid to penetrate into the edge layer of side 12. Due to the catalytic coating of this edge section of the porous substrate 8, the hydrogen bubbles in very fine beads into the carrier liquid to be hydrogenated as a result of being forced through the porous substrate.The relevant hydrogen bubbles are shown schematically. Some are identified in the figure by reference numeral 13. When the hydrogen comes into contact with the carrier liquid on the catalytic surface of the substrate 8, the hydrogen is incorporated into the unloaded carrier liquid. Not all of the hydrogen bubbles 13 introduced into contact with the catalytic surface of the substrate 8 are incorporated into the carrier liquid. A certain amount of hydrogen slip is removed from the reaction chambers 5 with the carrier liquid. This hydrogen slip is collected in the carrier liquid outlet collector 9 and redirected to the hydrogen supply 7 (not shown in the figure).

[0027] Fig. 3 shows in principle the same LOHC reactor as Fig.1, which, unlike LOHC reactor 1, is designed for dehydrogenation operation. Unless otherwise stated below, the statements made regarding LOHC reactor 1 apply equally to LOHC reactor 1.1. Identical components are identified by the same reference numerals.

[0028] The carrier liquid to be dehydrogenated is introduced into the carrier liquid inlet collector 3 through the carrier liquid inlet 2. In the reaction chambers 5, which in turn are heated by the surrounding substrates 8, hydrogen is released upon contact with the catalytic surface of the substrates 8 and enters the hydrogen collector 6 through the substrates 8. From there, the released hydrogen is removed from the reactor 1.1 via a hydrogen outlet 14. The dehydrated carrier liquid enters the reaction chambers 5 into the carrier liquid outlet collector 9 and is removed from the LOHC reactor 1.1 via the carrier liquid outlet 10.

[0029] Both LOHC reactors 1, 1.1 can be implemented in a single reactor. In this case, for example, reactor 1, in addition to its hydrogen supply 7, also has a hydrogen exhaust like reactor 1.1. Depending on the reactor's operation, either the hydrogen exhaust 14 or the hydrogen supply 7 is closed.

[0030] The above describes only one possible embodiment of the claimed invention. Numerous other possibilities exist for exploiting the special properties of using a catalytically coated porous substrate as a catalyst in a LOHC reactor. For example, these can also be connected to the surfaces of heat exchanger plates, for example. In this case, the positive properties of the particularly large catalytically active surface are utilized, but not the possibility of allowing a medium to pass through the substrate.

[0031] The invention has been described using exemplary embodiments. Without departing from the scope of protection described by the applicable claims, numerous further embodiments for implementing the inventive concept will become apparent to those skilled in the art without the need for further explanation within the scope of these statements. List of reference symbols 1, 1.1 LOHC reactor 2 Carrier fluid inlet 3 carrier fluid inlet collectors 4 Reaction section 5 Reaction chamber 6 hydrogen collectors 7 Hydrogen supply 8 catalytically coated porous substrate 9 Carrier fluid drain collector 10 Carrier fluid drain 11 Page to the hydrogen collector of the substrate 8 12 Side to the reaction chamber of the substrate 8 13 hydrogen bubbles 14 Hydrogen extraction

Claims

[1] LOHC reactor for hydrogenating an organic carrier liquid - with a carrier liquid inlet (2) for supplying carrier liquid to be hydrogenated, a carrier liquid outlet (10) for removing the hydrogenated carrier liquid and a flow path connecting the carrier liquid inlet (2) to the carrier liquid outlet (10), - with at least one reaction chamber (5) through which the carrier liquid flows, which is delimited at least in part by a catalytically coated substrate (8), - with a hydrogen supply (7) for supplying hydrogen into the at least one reaction chamber (5) and - with means for providing a temperature required for the catalytic reaction, characterized by that the substrate (8) with its catalytic coating is porous and open-pored on its side facing into the reaction chamber (5). [2] LOHC reactor for dehydrating an organic carrier liquid - with a carrier liquid inlet (7) for supplying carrier liquid to be dehydrated, a carrier liquid outlet (10) for removing the dehydrated carrier liquid and a flow path connecting the carrier liquid inlet (2) to the carrier liquid outlet (10), - with at least one reaction chamber (5) through which the carrier liquid flows, which is delimited at least in part by a catalytically coated substrate (8), - with a hydrogen discharge to remove hydrogen from the reactor and - with means for providing a temperature required for the catalytic reaction, characterized by that the substrate (8) with its catalytic coating is porous and open-pored on its side facing into the reaction chamber (5). [3] LOHC reactor according to claim 1 or 2, characterized bythat the substrate (8) carries a washcoat, at least on its catalytically coated side, to increase its active surface, to which the catalytically active component is applied or which contains it. [4] LOHC reactor according to one of claims 1 to 3, characterized by that the porous substrate (8) is a sintered metal material. [5] LOHC reactor according to claim 4, characterized by that the sintered metal material is incorporated into the openings of a mesh-like sintered metal carrier, such as an expanded metal plate or a wire mesh. [6] LOHC reactor according to claim 4, characterized by that the catalytically coated sintered metal material is applied with its side opposite the catalytic coating to a carrier foil as a carrier of the porous substrate. [7] LOHC reactor according to one of claims 4 to 6, characterized by that the sintered metal material is pleated. [8] LOHC reactor according to one of claims 1, 3 to 7 in their respective reference back to claim 1, characterized by that the catalytically coated porous substrate (8) is arranged in the LOHC reactor (1) to provide a media separation between the carrier liquid located in the reaction chamber (5) and the hydrogen supply (7), and the hydrogen for supplying into the reaction chamber (5) is passed through the porous substrate as a result of a pressure gradient towards the reaction chamber (5) and is introduced into the carrier liquid in fine bubbles. [9] LOHC reactor according to one of claims 2 to 7 in their respective reference back to claim 2, characterized bythat the catalytically coated porous substrate (8) is arranged in the LOHC reactor (1.1) to provide a media separation between the carrier liquid to be dehydrogenated located in the reaction chamber (5) and the hydrogen discharge (14), and the hydrogen or the carrier liquid flows through the porous substrate (8) to separate these two media. [10] LOHC reactor according to one of claims 1 to 9, characterized by that the LOHC reactor (1, 1.1) has a plurality of tubular or channel-shaped reaction chambers (5) which are enclosed by the catalytically coated substrate (8) and spaced apart from one another and are arranged in a hydrogen collector (6), wherein the reaction chambers (5) open with the mouth of one of their ends into a first carrier liquid collector (3) and with the mouths of the respective opposite ends into a second carrier liquid collector (9). [11] LOHC reactor according to one of claims 1 to 10, characterized bythat the catalytically coated porous substrate (8) is electrically heated. [12] Use of a porous, open-pore substrate (8) catalytically coated on at least one side as a catalytically coated substrate in a LOHC reactor for hydrogenating or dehydrogenating a carrier liquid. [13] Use according to claim 12, characterized by that during the process of hydrogenating an organic carrier liquid through the catalytically coated, porous, open-pored substrate (8), a media separation takes place between the hydrogen acting on one side of the substrate (8) and the organic carrier liquid contacting the organic carrier liquid to be hydrogenated on its other, catalytically coated side. [14] Use according to claim 12 or 13, characterized by that the porous, open-pored substrate (8) is a sintered metal plate or is formed from such a plate.

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