DE102018112463A1 - Process for carrying out strong gas-releasing reactions - Google Patents

Abstract

A method for carrying out strong gas-releasing reactions by discharging a gas product from a liquid starting material, characterized in that at least one liquid starting material flows through a porous structure loaded with a catalyst.

Description

The present invention relates to a method for carrying out strong gas-releasing reactions by discharging a gas product from a liquid starting material, wherein the liquid starting material flows through a catalyst-loaded porous structure. The invention further relates to devices for carrying out the discharge and the use of a catalyst-loaded porous structure for carrying out strong gas-releasing reactions.

Strong gas-releasing reactions, that is strong gas-generating reactions, are e.g. from the dehydrogenation of liquid, organic hydrogen carriers (LOHC: Liquid Organic Hydrogen Carriers) known.

In this type of reaction, a liquid organic substance (charged organic hydrogen carrier) is decomposed at elevated temperature on a solid catalyst into a liquid product (discharged organic hydrogen carrier) and hydrogen. Depending on the chemical nature of the organic substance, up to 9 molecules of hydrogen are released per molecule of the organic substance, causing a very strong and sudden evolution of gas. This evolution of gas impedes the achievement of a high degree of conversion in that the forming gas impedes the access of the unreacted liquid components to the catalyst. This is because the contact between the liquid molecules and the catalyst surface (nanoparticles) located predominantly inside the usually porous catalysts requires diffusion into the porous structure. If gas forms in the interior of the structure, which strives outwards, the penetration of the liquid is made more difficult and thus its implementation. For this reason, catalysts for this type of reaction are carried out as shell catalysts, i. The catalytically active nanoparticles are placed only in a thin shell on the outer surface of the one or more millimeter-diameter catalyst pellets. However, this leads to a small amount of catalyst per reactor volume and thus to poor volume utilization. Furthermore, in conventional reactor systems with flow-through packings of such pellets or with thin catalyst layers on structured supports (sponges, 3D printed structures, etc.), the gas evolution causes a considerable broadening of the residence time distribution of the liquid phase, which likewise counteracts complete conversion of the laden liquid because the shortest practical residence time must still be chosen so long that complete implementation is possible. This requires a large volume of construction to ensure high levels of discharge. These are necessary in the application of such systems in vehicles to achieve a high range per liter LOHC.

From the US 7,766,986 B2 (or equivalent publication US 2006 0143981 A1 ) a microchannel reactor with channels is known. In the microchannels is a catalyst of metal nanoparticles.

In the DE 2010 038 491 A1 A fuel supply device is described in which a hydrogen-enriched carrier, in particular LOHC, is brought in a reactor vessel for dehydrogenation for the provision of hydrogen. The reactor vessel is a pressure and temperature-resistant outer shell, in which there is a movable, in particular rotating body, wherein the body and / or the outer shell is equipped inside with a catalyst. The movable body may be provided on its outer contour with an inside coated with catalyst shroud, the inside being provided with grooves or with porous, in particular sponge-like structures.

The DE 10 2013 214 313 A1 describes a reactor for releasing hydrogen, in a reaction vessel containing at least one body with a metallic support structure, on which a solid, highly porous coating is applied, which contains catalytically active substances. The catalytic dehydrogenation is carried out under pressure at high temperatures along the coating, so that hydrogen is released and is discharged ascending upward.

The release of Wild 2010 at the " 18 , World Hydrogen Energy Conference "describes a dehydrogenation by the flow of an educt into microchannels. As a result, different flows are generated in the course of the gas release, which are difficult to control.

From the DE 10 2005 010 213 is a catalytically active membrane pore flow reactor for the reaction of organic compounds, preferably known for hydrogenation. The reactor comprises the use of ceramic membranes with different pore diameters.

The Hydrogenious Technology (LOHC) hydrogen release systems available today are still significantly too large to accommodate mobile applications in the trucking industry. This is mainly due to the low reactor productivity per volume at the required high discharge.

It was therefore an object of the present invention to provide a process which does not overcome the disadvantages of the prior art has more. In particular, a good contact of the products with the catalyst should be ensured in order to achieve a substantially complete reaction of the products. The method should also ensure the shortest possible residence time of the loaded product at a substantially complete implementation as mentioned above.

Another object of the present invention is the use of the method and the corresponding devices in the field of mobility, the so-called. On-board generation of hydrogen from LOHC, e.g. be in truck. In general, a high volumetric gas release rate, in particular hydrogen release rate and a low system weight should be achieved.

Furthermore, high degrees of discharge of the product are to be made possible with a small construction volume of the device necessary for the process.

Another object was therefore to provide devices in which the method according to the invention can be carried out. These devices are intended to have a smaller construction volume than the prior art and allow equal or higher levels of discharge of the product.

The object is achieved by a method for carrying out strong gas-releasing reactions by discharging a gas product from a liquid starting material, characterized in that at least one liquid starting material flows through a catalyst-loaded porous structure. Alternatively, the object is achieved by a method for discharging a gas product from a liquid starting material, characterized in that at least one liquid educt flows through a catalyst-loaded porous structure.

In one embodiment, the method is characterized in that essentially the entire liquid product flows through the porous structure.

For the purposes of the invention, the term "essentially" is used with reference to an amount of substance to define that at least 80%, preferably 85%, 86, 87, 88, 89%, particularly preferably 90, 91, 92, 93, 94%. , in particular 95, 96, 97, 98, 99 or 100% of this substance are concerned. This means, for example, that in the case of the starting material which substantially flows through the porous structure or flows into it, is reacted, and preferably discharged and essentially leaves the porous structure as a product, at least 80%, preferably 85%, 86, 87 , 88, 89%, particularly preferably 90, 91, 92, 93, 94%, in particular 95, 96, 97, 98, 99 or 100% flow through the porous structure or flow into the structure.

Substantially complete conversion or discharge means for the purposes of the invention that at least 80%, preferably 85%, 86, 87, 88, 89%, particularly preferably 90, 91, 92, 93, 94%, in particular 95, 96, 97, 98, 99 or 100% of the educt are reacted or discharged.

Discharge in the sense of the present invention means that a gas is liberated as product from a liquid educt. The gas product, ie the gaseous product, can be bound in an alternative in the educt, in the sense of a solution, absorption, etc., or by partial evaporation of a liquid.

In a further, preferred alternative, the gas is formed during the reaction of the liquid starting material on the catalyst, that is synthesized in situ in a chemical reaction. Also possible are mixed forms, i. for example both synthesis in combination with desorption, partial evaporation, etc ..

An essential feature of the present invention is that at least one liquid product flows through a porous structure which is loaded (coated or coated) with catalyst.

However, flow according to the invention does not mean that the same product, which flows in on one side of the porous structure, flows out on the opposite side of the structure. For the purposes of the present invention, flow through only means that the product flows into the porous structure, is reacted upon contact with the catalyst, ie is discharged, and the gaseous product, if appropriate unreacted liquid educt and optionally at least one further product, preferably one pour out another liquid, discharged product.

In a further embodiment, the invention relates to a method characterized in that the porous structure is a material, preferably a monolith, which has three-dimensionally fluidically connected cavities.

Three-dimensionally fluidically interconnected cavities in the sense of the present invention means that a large number of individual pores, also referred to as cavities, are present in the porous structure and linked to one another, so that a flow through the porous structure is ensured by a fluid. In other words, the porous structure has a common solids-free space that extends across the porous structure, that is, from one edge to the opposite Edge. The solids-free space is formed by pores, cavities, which are fluidically linked together.

The process is characterized in an alternative in that the porous structure is loaded (coated or treated as equivalent termini) with catalyst particles.

The porous structure is loaded in one embodiment with catalyst particles.

In a further alternative or in addition, the catalyst is fixed to the walls of the pores or cavities of the porous structure.

Preference is given to using nanoscale catalyst particles, that is to say catalyst particles having an average diameter of 1 to 1000 nm, preferably 1 to 100 nm, more preferably 1 to 10 nm.

In a further embodiment, the porous structure has pores or cavities with a nominal pore size of 1 nm-20 μm.

In an alternative, the porous structure is a monolithic body. In one alternative, it contains or consists of at least one monolith of the following materials: Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Al-Si mixed oxides, cordierite, stainless steels or high-temperature steels.

In an alternative, the porous structure is a ceramic sponge, preferably a ceramic sponge monolith. In an alternative, the porous structure is formed of a plurality of monoliths.

Monoliths to be used according to the invention are catalyst-functionalized monoliths. In one alternative, the term monolith also includes other (micro) structured bodies or packages of catalyst powder.

The one or more materials, preferably monoliths of the porous structure, have pores, cavities with a cell density of 200 to 1000 cpsi, preferably 250 to 800, particularly preferably 200 to 700, 350 to 650, in particular 400 to 600. The monolith (s) are with catalyst functionalized, ie there is at least one catalyst in the pores.

The catalysts used are catalysts comprising metals, preferably noble metals, more preferably rutium, platinum, palladium and / or gold and / or transition metals, preferably nickel, copper, cobalt, iron, etc. In one alternative, microporous support materials are used to increase the surface area of the catalytically active material (metals). In this case, the support material (typically Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ ) is applied by conventional methods such as sol-gel technique, washcoat or the like on the monolith, alternatively on an otherwise coated body such as a microstructured system.

In an alternative, the catalyst located in the porous structure, ie in the pores of the material, preferably a monolith, exhibits a concentration gradient. The concentration of catalyst per unit volume of monolith or cell can change axially or radially.

The porous structure is preferably a sintered material containing or consisting of metal, glass, ceramic or temperature-stable plastic or any combination thereof.

In an alternative of the invention, the walls of the pores have an (additional) microporous layer which is loaded with catalyst nanoparticles.

One embodiment relates to a method characterized in that at least one liquid gas-laden product flows pressure-driven into the porous structure or flows through it.

The process according to the invention can be carried out continuously.

A strong gas-releasing reaction according to the invention is characterized by liberation of at least 2 moles of a gaseous product from one mole of liquid starting material or at least 100 ml of a gaseous product from 1 ml of a liquid product.

• Reaktionen, bei denen aus einem Mol eines flüssigen Edukts gegebenenfalls ein Mol eines flüssigen Produkts und mindestens zwei Mol eines gasförmigen Produkts, bevorzugt 3, 4, 5 Mol eines gasförmigen Produkts, besonders bevorzugt 6, 7 Mol eines gasförmigen Produkts, insbesondere 8, 9 oder mehr Mol freigesetzt werden.
• Alternativ werden solche Reaktionen über Volumina definiert als Reaktionen, aus denen aus 1 ml eines flüssigen Edukts mindestens 100 ml eines gasförmigen Produkts entstehen, bevorzugt 200, 300, besonders bevorzugt 400, insbesondere 500 ml oder mehr eines gasförmigen Produkts entsteht beziehungsweise synthetisiert wird.

Strong gas-releasing reactions are defined as follows:

• Reactions in which from one mole of a liquid educt optionally one mole of a liquid product and at least two moles of a gaseous product, preferably 3, 4, 5 moles of a gaseous product, more preferably 6, 7 moles of a gaseous product, in particular 8, 9 or more moles are released.
• Alternatively, such reactions are defined via volumes as reactions from which at least 100 ml of a gaseous product are formed from 1 ml of a liquid educt, preferably 200, 300, particularly preferably 400, in particular 500 ml or more of a gaseous product being formed or synthesized.

As mentioned above, in addition to the gas product, another fluid product may be formed.

Preference is given as a gas product H2 (Hydrogen) from LOHC (Liquid Organic Hydrogen Carrier, liquid organic hydrogen carrier) discharged as starting material. The range of eligible as LOHC substances is extremely large. Such systems can be used for energy-efficient transport of hydrogen from a central source to decentralized consumption or for hydrogen-powered mobility with fuel cells or internal combustion engines.

Essential for the present invention is the gas release in a flow-through of the liquid reactant pore in which a catalyst, preferably arranged in particle form. The wall of the cavity, so the pore, is preferably loaded or loaded with nanoscale catalyst particles. Such a porous structure corresponds to a three-dimensionally coated shell catalyst.

The liquid educt is introduced from one side by means of pressure in the porous structure. Upon contact with the catalyst, the gas discharge takes place. The three-dimensionally fluidically interconnected cavities allow a trouble-free removal of the resulting glass bubbles in the flow direction, in other words there is a convective transport of the discharged gas, so the transport of the gas bubbles with the flowing liquid. This liquid may on the one hand be the liquid starting material, but on the other hand also the discharged, liquid product. In the flow direction loaded laden educt is tracked. Due to the trouble-free removal of the discharged gas, this does not hinder the access of fresh educt to the catalyst. Schematically, this is in 1 shown.

In one embodiment of the invention, the method and the corresponding device are described as follows:

LIST OF REFERENCE NUMBERS

1

Loaded liquid educt (pressure pF)

2

Catalyst walls loaded with the cavity

3

Released gas (pressure pF)

4

Discharged liquid product (pressure pF <pF)

5

Porous membrane

6

filter discs

7

cavity walls

8th

Dense mechanical structure for fluidic heating

9

Porous metallic structure

• 1 schematically shows the inventive method. Here is with numeral 1 denotes the gas-loaded, liquid educt. digit 2 represents the catalysed cavity walls. The released gas is number 3 and the unloading product is numeral 4 ,
• 2 shows a device for carrying out the method according to the invention. With the numeral 5 is called the porous tube membrane. From two sides is the loaded, liquid educt 1 entered. On one side becomes the discharged liquid product 4 from the porous tube membrane 5 dissipated. On the other side is the discharging gas 3 dissipated.
• 3 shows another variant of the invention, in which rotating filter discs 6 be used. In the hollow shaft 7 the liquid reactant is fed. The rotation causes the liquid educt to enter the filter discs 6 introduced due to centrifugal force. The filter discs 6 are with a catalyst 2 applied. The discharged gas 3 and the discharged liquid product 4 are separated and discharged.
• 4 represents a component that is used for a fluidic heating. Such components have a dense, metallic structure for the fluidic heating 8th on. Furthermore, a porous, metallic structure 9 used as material.

The basic principle of the invention is that the contact between the liquid starting material and the catalyst is not effected by diffusion into a porous catalyst pellet counter to the direction of transport of the gaseous product, but by a pressure-driven flow through a porous catalyst body having pores in the range of less than 1 nm up to about 20 nm from the inside to the outside, in the simplest case, a sintered tube consisting of metal, glass, ceramic, or a temperature-stable plastic, in the three-dimensional pore system, the catalyst nanoparticles are deposited and fixed to the walls. In order to increase the amount of catalyst nanoparticles, a microporous layer can be applied to the walls in the interior of the tube, which then in turn absorbs the catalyst nanoparticles and does not make the pores of the tube impassable for the liquid. Instead of tubes, almost any shapes, such as capillaries, hollow fibers, filter disks or other, even 3D-printed porous structures with a large outer surface per volume can be used. To provide the required Dehydrierwärme also channel structures for a heating fluid can be integrated directly into the components, for example by means of 3D printing. Through the flow from inside to outside, the diffusive Eliminate mass transfer resistances. The forming gas can escape easily through the three-dimensional pore network to the outside and does not block the access of the internally tracked laden liquid. When exiting the pores occurs in the surrounding housing, for example, by gravity or when running as a rotating disc filter additionally supported by centrifugal forces separation of gas and liquid.

The present invention also relates to devices for carrying out the method according to the invention. The basic principle of such a device is in 2 represented by the example of the use of a raw membrane as a porous structure. It is a tubular or tubular structure whose walls have a porous structure. In this tube is preferably introduced from both ends loaded liquid educt at elevated pressure and or temperature.

A temperature increase can generally be carried out before introducing the educt into the device or porous structure or first or additionally in the device and / or porous structure.

For the purposes of the invention, elevated conditions such as e.g. an elevated pressure or temperature conditions above the standard conditions of 25 ° C and 1 atmospheric pressure. An increased pressure or a pressure difference between the supply and the discharge side of the porous structure according to the invention can be achieved by a pump or e.g. be generated by centrifugal forces.

The loaded liquid educt is introduced into the porous structure. Upon contact of the starting material with the catalyst, on the one hand gas is discharged and a discharged, liquid product remains. Both are displaced in the flow direction from the porous structure by nachrückendes liquid educt. The discharged gas has a lower pressure on the outside of the porous structure than the supplied liquid. Likewise, the discharged liquid product has a lower pressure than the introduced liquid product.

An apparatus according to the invention for the discharge of gases from liquid substances, in particular from highly gas-releasing educts, thus contains a porous structure, the pores are loaded with catalyst or acted upon and a device for increasing the pressure of the liquid educt or for generating a pressure difference between the Supply side of the educt and the discharge side of the products in order to achieve an inflow into the porous structure. Such an apparatus for increasing the pressure is in one alternative, a pump. In a further alternative, this is a device which sets one or more porous structures shaped as round filter pockets into rotation and generates a pressure difference between the inside and outside by the centrifugal force. For heating, ie for increasing the temperature of the liquid starting material and / or for introducing the heat energy required for the gas formation or for the gas release from the liquid, e.g. an electrical resistance heating are used, which preferably couples the heat required for the discharge of the gas directly into the porous structure, whereby a particularly efficient heat transfer is achieved.

In one embodiment of the present invention, a device according to the invention of rotating filter discs is constructed on a hollow shaft, as in 3 , shown. Loaded liquid educt is fed into the hollow shaft. Due to the rotation, the liquid educt is introduced into the filter discs due to the centrifugal force. The filter discs are the porous structures that are exposed to catalyst. The gas product present after the passage of the porous structure can easily be separated from an optionally liquid product by means of centrifugal force. Such a device is very compact.

A further embodiment relates to integrated components with a dense metallic structure, which are used for a fluidic heating. Such integrated components can be produced, for example, by means of 3D printing, for example 3D printing of metals by selective laser melting (SLM). An example will be in 4 shown.

Further alternatives relate to material variants for the porous structures, the materials being selected from the group consisting of or consisting of ceramic filters, metallic filters, polymer filters and composite materials. In further embodiments, electrically conductive materials (metals, conductive ceramics or polymers or composites) are used. Advantageously, the electrical resistance heating for direct coupling of the dehydrogenation of the educt discharge is possible. This can lead to particularly compact systems.

In one embodiment of the present invention, the walls of the cavities of the porous structure are not uniformly exposed to catalyst particles, there is an asymmetric arrangement of the catalyst particles. Such an asymmetric arrangement can, for example, according to the EP 1,599,613 A getting produced. As a result, the evolution of gas in the cavities of the porous structure can be additionally controlled.

In a further embodiment of the present invention, the method according to the invention is repeated or alternatively carried out in successively connected devices. Such a cascading according to the second alternative, ie the liquid phase, both liquid starting material and possibly liquid product, flows successively through several devices according to the invention, leading to an increase in sales per element, ie per device, as well as to an optimization of the overall sales.

The inventive method for the discharge of gas from liquid educts and the devices derived therefrom allow a much higher effective amount of catalyst per volume, while avoiding Stofftransportlimitierungen and ensure easy separation of gas and liquid in a compact housing than the prior art. With a suitable design (for example 3D printing of metals), microfluidic heating structures can be directly integrated. Due to the combined effect of the three effects, much higher hydrogen release capacities per volume are possible, which are crucial for all applications with high demands on system compactness, in particular in the mobile sector.

The use of a porous structure with integrated nanosize catalyst particles as catalyst for the dehydrogenation of liquid organic hydrogen carriers integrated into the inventive devices addressed several major weaknesses of the previous approaches: it ensures good contact between unreacted liquid reactant and catalyst despite gas evolution ensures a defined Dwell time of the liquid phase and prevents the formation of stagnant liquid films, minimizes mass transfer resistances, allows a high catalyst concentration per volume, an integrated phase separation and also a direct electrical or fluidic heating.

The principle is generalizable to all reactions that release large quantities of gas from a liquid and produce one or more liquid products in addition to the gas.

With regard to the configuration of the geometry of the porous structure through which it flows, possible porous carrier layers mounted inside the pore system, the materials for the flow-through structure and the active catalyst phase as well as the geometry of the reactor housing, numerous variations are possible. Also, the gas / liquid separation can be additionally supported by execution of the structure as a rotating disc filter.

The special effect results from the flow through the pore system of a catalyst in contrast to the conventional countercurrent diffusion of reactant and product. As a result, the transport resistances are largely eliminated, the obstruction of the entry of loaded liquid to the active centers by forming gas is overcome by the flow direction from the inside to the outside.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7766986 B2 [0004]
• US 20060143981 A1 [0004]
• DE 2010038491 A1 [0005]
• DE 102013214313 A1 [0006]
• DE 102005010213 [0008]
• EP 1599613A

Claims (15)

A method for carrying out strong gas-releasing reactions by discharging a gas product from a liquid starting material, characterized in that at least one liquid educt flows through a porous structure loaded with catalyst. Method according to Claim 1 characterized in that substantially the entire liquid educt flows through the porous structure. Method according to one of the preceding claims, characterized in that the porous structure is a material, preferably monolith, which has three-dimensional fluidly connected cavities. Method according to one of the preceding claims, characterized in that the porous structure is loaded with catalyst particles. Method according to one of the preceding claims, characterized in that the catalyst is fixed to the walls of the pores or voids of the porous structure. Method according to one of the preceding claims, characterized in that nanoscale catalyst particles are used. Method according to one of the preceding claims, characterized in that the porous structure has pores or cavities with a nominal pore size of 1 nm - 20 microns. Method according to one of the preceding claims, characterized in that the porous structure is a sintered material containing or consisting of metal, glass, ceramic or temperature-stable plastic or any combination thereof. Method according to one of the preceding claims, characterized in that the walls of the pores have a microporous layer which is loaded with catalyst nanoparticles. Method according to one of the preceding claims, characterized in that at least one liquid, gas-loaded educt flows pressure-driven into the porous structure or flows through it. Method according to one of the preceding claims, characterized in that it is carried out continuously. Method according to one of the preceding claims, characterized in that the strong gas-releasing reaction liberates at least 2 moles of a gaseous product from one mole of liquid educt or at least 100 ml of a gaseous product of 1 ml of a liquid product are released. Method according to one of the preceding claims, characterized in that in addition to the gas product, a further fluid product is formed. Method according to one of the preceding claims, characterized in that as the gas product H ₂ (hydrogen) from LOHC (liquid organic hydrogen carrier) is discharged as starting material. Use of a porous structure for discharging at least one gas product from a liquid educt, characterized in that the liquid educt flows through this porous structure.

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