Method for operating a reactor, which comprises a catalyst material, for catalytically storing or releasing hydrogen gas, and system comprising such a reactor

Abstract

The invention relates to a method for operating a reactor, which comprises a catalyst material, having the steps of catalytically hydrogenating or catalytically dehydrogenating a hydrogen carrier medium by bringing the catalyst material into contact with the hydrogen carrier medium in the reactor (2) and rinsing the catalyst material with a rinsing medium in the reactor (2), thereby removing catalyst-deactivating substances, the rinsing medium comprising a hydrogen carrier medium.

Description

[0001] Method for operating a reactor comprising a catalyst material for catalytic storage or release of hydrogen gas and plant with such a reactor

[0002] This patent application claims priority from German patent application DE 10 2022 210 824.8, the contents of which are incorporated herein by reference.

[0003] The invention relates to a method for operating a reactor comprising a catalyst material for catalytic storage or release of hydrogen gas and to a plant comprising such a reactor.

[0004] DE 10 2015 219 305 A1 discloses a device for the catalytic release of hydrogen gas from a hydrogen carrier medium. The release reaction is a dehydrogenation reaction of the hydrogen carrier medium. The dehydrogenation takes place in a dehydrogenation reactor using a catalyst. Studies have shown that the activity of the catalyst decreases with increasing use. As a result of the loss of activity, the reactor power decreases. The volumetric and gravimetric power density during hydrogen release are reduced. The technical performance of the reactor is diminished.

[0005] If a decrease in the catalyst material's activity is detected, complex regeneration measures are required, which could, in particular, lead to a temporary shutdown of the reactor. An oxidative process can be used to regenerate the catalyst material. Due to the use of oxygen, increased safety measures are required. Furthermore, there is a risk that oxygen-containing impurities will form as a result of oxidative regeneration, which would then have to be subsequently purified from the hydrogen carrier medium. Oxidative regeneration is complex and impairs the overall efficiency of the process.

[0006] It has been found that deactivation of the catalyst material can be caused by deposits, which may be degradation products of the hydrogen carrier medium. The formation of these degradation products depends on the process control during hydrogenation or dehydrogenation of the hydrogen carrier medium. Adapting the hydrogenation or dehydrogenation process in such a way that the formation of degradation products is reduced or avoided is very complex.

[0007] The invention is based on the object of increasing the service life of the catalyst material using inexpensive methods.

[0008] This object is achieved according to the invention by a method having the features of claim 1 and by a system having the features of claim 11.

[0009] The core of the invention is that catalyst-deactivating substances can be effectively rinsed off a catalyst material using a flushing medium. During flushing, the catalyst material can remain in a reactor used for the catalytic hydrogenation or dehydrogenation of hydrogen carrier medium. The flushing process is inexpensive. In particular, the flushing medium is liquid. This improves the flushing around the catalyst material and the removal of catalyst-deactivating substances.

[0010] A catalyst-deactivating substance is in particular a coke and / or a coke precursor, which are formed in particular during the catalytic hydrogenation or catalytic dehydrogenation of the hydrogen carrier medium in the reactor.

[0011] The catalyst-deactivating substances are, in particular, deposits, especially aromatic and / or unsaturated molecules, which are particularly large. Large molecules according to this definition are, in particular, planar, aromatic, pi-conjugated hydrocarbon compounds with at least 16 carbon atoms and, in particular, at least 20 carbon atoms in the carbon skeleton. The catalyst-deactivating substances can additionally or alternatively, particularly depending on the degree of coking, be completely graphitic carbon deposits on the catalyst material.

[0012] The catalyst-deactivating substances deposit in particular on a surface of the catalyst material and / or on the catalytically active noble metal, so that the hydrogenation and / or dehydrogenation reaction is inhibited. The process has been found to be particularly advantageously suited for a hydrogen carrier medium. Hydrogen can be reversibly chemically bound to the hydrogen carrier medium and released again. Such a hydrogen carrier medium is, in particular, a liquid organic hydrogen carrier medium (LOHC). A hydrogen carrier medium that is present in an at least partially hydrogen-laden form as perhydrodibenzyltoluene (HisDBT), perhydrobenzyltoluene (HnBT), dicyclohexane, and / or methylcyclohexane (C7H14), which can be dehydrogenated to toluene (C?Hx), has proven particularly suitable.It is also possible to use a mixture of hydrogen carrier medium in the at least partially hydrogen-laden form of perhydrodiphenylmethane and perhydrobiphenyl. These compounds can be dehydrogenated to diphenylmethane and biphenyl. A mixture of biphenyl to diphenylmethane in a ratio of 30:70, especially 35:65, and especially 40:60 is particularly advantageous.

[0013] The catalyst material comprises a metal, in particular platinum, palladium, nickel, rhodium, rhenium and / or ruthenium, and in particular mixtures and / or alloys of these metals. The catalyst material is in particular arranged on a catalyst support and in particular attached thereto. The catalyst support is in particular aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and / or activated carbon. In particular, the catalyst support is a porous oxide support. The material of the catalyst support has pores with a diameter of at least 10 nm, in particular at least 20 nm, in particular at least 50 nm and in particular at least 100 nm. The weight fraction of the catalyst material, based on the catalyst support, is between 0.1% and 10%.

[0014] The catalyst support comprises a plurality of catalyst particles, in particular catalyst support particles, which are present in particular as pellets. The catalyst particles have an average particle size of 0.5 mm to 10 mm, in particular of 1 mm to 8 mm, and in particular of 2 mm to 4 mm.

[0015] The catalyst particles are arranged, in particular, in the form of a fixed bed through which the hydrogen carrier medium, which is in particular at least partially liquid, flows. The hydrogen carrier medium can also be present, at least partially, as vapor, particularly when benzyltoluene is used as the hydrogen carrier medium in the at least partially discharged form. Due to the vapor content of benzyltoluene in the dehydrogenation, coking can occur, particularly high-boiling coking, which is not removed in the gas phase. With increasing conversion in the dehydrogenation, the gaseous fraction of the hydrogen carrier medium increases, since released hydrogen gas causes a reduction in the partial pressure of the hydrogen carrier medium.

[0016] It has surprisingly been found that by flushing the catalyst material the initial activity of the catalyst can be restored at least partially and in particular to at least 50%, in particular to at least 70%, in particular to at least 80%, in particular to at least 90% and in particular to at least 95%. In particular, it was found that by flushing the catalyst-deactivating substances are rinsed off the surface of the catalyst material and / or the catalytically active noble metal. The hydrogenation reaction and / or the dehydrogenation reaction can be carried out uninhibited again after flushing. In particular, it was recognized that complex regeneration measures for the catalyst material, in particular oxidative regeneration, are unnecessary or at least the extent of oxidative regeneration can be reduced.

[0017] A further finding of the invention is based on the fact that a, in particular additional, hydrogen carrier medium serves as the purging medium. In particular, external purging media that systematically differ from the hydrogen carrier medium are dispensable. The purging medium can be the hydrogen carrier medium that is catalytically hydrogenated and / or dehydrogenated. In particular, the hydrogen carrier medium used as the purging medium can be identical to the hydrogenated or dehydrogenated hydrogen carrier medium. A hydrogen carrier medium with a comparatively low boiling point, such as toluene, facilitates the downstream removal of the catalyst-deactivating substances from the purging medium and / or the hydrogen carrier medium, since the catalyst-deactivating substances are high-boiling components.If the hydrogen carrier medium used as the flushing medium is itself a higher-boiling component, the catalyst material can be advantageously and sufficiently flushed, especially at higher temperatures, since the liquid phase fraction in the higher-boiling hydrogen carrier medium used as the flushing medium is higher than in low-boiling flushing media. It is particularly advantageous if the flushing medium is at least partially loaded with hydrogen carrier medium, in particular benzyltoluene.

[0018] It has been found that at least partially loaded hydrogen carrier medium is particularly suitable as a purge medium because the affinity of further deposits of degradation products, in particular coke deposits, on the catalyst material is reduced by the at least partially loaded hydrogen carrier medium. The risk of degradation product deposits can be reduced in particular by releasing hydrogen gas during purge. Under reduced reaction conditions and / or reduced purge conditions, the risk of coke formation is also reduced when using at least partially discharged hydrogen carrier medium as the purge medium.

[0019] Reduced reaction conditions mean, in particular, reduced reaction temperatures of at most 330 °C, in particular at most 320 °C, in particular at most 300 °C, and in particular at most 280 °C. The reduced temperatures result in lower conversions and thus a reduced proportion of discharged hydrogen carrier medium in the gas phase. It has been found that an increased gas phase proportion of the at least partially discharged hydrogen carrier medium can cause undesirable coking of the catalyst material. This risk is reduced at the reduced temperatures. As a result of the reduced temperatures, the thermal stress on the hydrogen carrier medium is also reduced.

[0020] The purging conditions, in particular the efficiency for removing coke deposits from the catalyst surface, is increased when an at least partially discharged hydrogen carrier medium is used as the purging medium. The coke deposits, like the at least partially discharged hydrogen carrier medium, are aromatic hydrocarbons. This increases their solubility. It has therefore been recognized as particularly advantageous that the use of a hydrogen carrier medium as the purging medium allows the purging conditions to be adjusted almost continuously during the purging process. The adjustment of the purging conditions is advantageously possible by using either an at least partially loaded hydrogen carrier medium, i.e. reactant, or an at least partially discharged hydrogen carrier medium, i.e. product, or a mixture of product and reactant, which has been adjusted in particular with a specific mixing ratio, as the purging medium.An advantageous adjustment of the purging conditions is also possible, additionally or alternatively, by recycling product from a hydrogenation or dehydrogenation reactor as reactant to this reactor, i.e., by recirculating the purging medium. This allows the degree of hydrogenation of the purging medium to be specifically and, in particular, continuously varied during the purging process.

[0021] The flushing out of the catalyst deactivating substances with the at least partially loaded hydrogen carrier medium is possible in an improved manner.

[0022] A hydrogen carrier medium is considered to be loaded if the degree of hydrogenation is at least 80%, in particular at least 90%, in particular at least 95% and in particular at least 99%.

[0023] In particular, the flushing medium comprises the at least partially loaded hydrogen carrier medium. The proportion of the at least partially loaded hydrogen carrier medium in the flushing medium is at least

[0024] 50%, in particular at least 70%, in particular at least 90%, in particular at least 95%, and in particular at least 99%. In particular, the flushing medium consists exclusively of the at least partially loaded hydrogen carrier medium.

[0025] Flushing the catalyst material can be easily integrated into reactor operation. In particular, flushing can be integrated as an integral part of a process cycle. Complex conversion measures are unnecessary.

[0026] A process in which the purge medium is passed through the reactor in cocurrent with the hydrogen carrier medium simplifies purge processing. Alternatively, the purge medium can be passed through the reactor in countercurrent to the hydrogen carrier medium to be hydrogenated or dehydrogenated.

[0027] The process according to the invention is suitable for flushing catalyst material used for the hydrogenation and / or dehydrogenation of hydrogen carrier medium. It has been found that, compared to dehydrogenation, fewer, and in particular no, catalyst-deactivating cokes are formed during hydrogenation. Flushing the catalyst material by recirculating the flushing material is particularly advantageous during hydrogenation. In particular, the effort required to adjust pressure and / or temperature is reduced because the liquid phase fraction of the flushing medium in the hydrogenation reaction is sufficiently high. The basic mechanisms for carrying out the flushing process, i.e., increasing the pressure, reducing the temperature, and / or increasing the mass flow of the flushing medium, can promote efficient flushing.

[0028] A method according to claim 2 enables a targeted influencing of the purging properties and thus the reactivation of the catalyst material. It has been found that the purging properties change depending on the material properties of the purging medium, in particular its physiochemical properties and, in particular, the degree of hydrogenation of the additional hydrogen carrier medium serving as the purging medium. In particular, modified purging properties can be specifically defined.

[0029] In particular, it was discovered that the purging properties, especially the degree of hydrogenation of the additional hydrogen carrier medium, can be specifically adjusted before and / or during a purging process. This improves the ability to influence the purging properties.

[0030] It has been recognized that at least partially discharged hydrogen carrier medium comprising aromatic hydrogen carriers has improved solubility for the cokes, which typically have a similar molecular structure to the at least partially discharged hydrogen carrier medium.

[0031] At least partially loaded hydrogen carrier medium as a purge medium comprises saturated hydrogen carriers, so that the separation of coke from the purge medium in a downstream purification process is facilitated due to the different molecular structures. A method according to claim 3 simplifies switching between the catalytic hydrogenation or catalytic dehydrogenation of the hydrogen carrier medium and the purging of the catalyst material.

[0032] In particular, so-called dynamic purging can be performed. The process conditions in the reactor are comparable during catalytic hydrogenation or catalytic dehydrogenation and purging. Adapting the required process conditions is straightforward and, in particular, quick. It has been shown that purging the catalyst material at a purge temperature between 100 °C and

[0033] 350 °C, in particular between 150 °C and 330 °C and in particular between 200 °C and 300 °C. A purge pressure for dehydrogenation is in particular between 0.5 barg and 6.0 barg, in particular between 0.8 barg and 5.5 barg and in particular between 1.0 barg and 5.0 barg. The purge pressure for hydrogenation is between 0.5 barg and 50 barg, in particular between 5 barg and 40 barg and in particular between 10 barg and 30 barg.

[0034] In particular, it was recognized that the purge pressures for hydrogenation and dehydrogenation can be different, with the purge pressure for hydrogenation being in particular greater than the purge pressure for dehydrogenation.

[0035] Dehydration takes place at process temperatures between 280 °C and 330 °C and at a pressure between 0.5 barg and 5.0 barg.

[0036] The hydrogenation takes place at process temperatures between 200 °C and

[0037] 350 °C and at a pressure between 10 barg and 50 barg.

[0038] In particular, it was found that purging can be started directly from catalytic hydrogenation or catalytic dehydrogenation, whereby further process-related adjustments are unnecessary. Switching between catalytic hydrogenation or catalytic dehydrogenation and purging is achieved, in particular, by adjusting the pressure, i.e., from a hydrogenation pressure or dehydrogenation pressure to the purging pressure. In particular, the hydrogenation pressure or dehydrogenation pressure is increased to the purging pressure, so that, with respect to the catalytic dehydrogenation process, the altered chemical equilibrium leads to reduced hydrogen release. The reduced hydrogen release rate shifts the process equilibrium of the hydrogen carrier medium between vapor and liquid fractions toward the liquid fraction. This means that the liquid fraction of the hydrogen carrier medium increases, thereby promoting the flushing of the catalyst material with liquid.

[0039] In particular, it is possible that hydrogen gas may be released, at least in small quantities, even during purging. Relative to a nominal operating point of a dehydrogenation process, the hydrogen release rate during purging may be at least 5%, in particular at least 10%, in particular at least 20%, in particular at least 30%, and in particular up to 50%. The lower the release rate during purging, the lower the vapor content and the more efficient the purging.

[0040] In particular, it was found that switching between the catalytic hydrogenation or dehydrogenation process and purging is possible based on the hydrogen gas pressure in the reactor. Based on the hydrogen gas pressure, dynamic control between the hydrogenation or dehydrogenation process and the purging process is possible, in particular by adjusting the reaction pressure in the reactor accordingly. Additionally or alternatively, dynamic control is also possible using the reaction temperature to switch between the hydrogenation or dehydrogenation process and the purging process. In particular, reducing the reaction temperature can make it possible to switch from the hydrogenation or dehydrogenation process to the purging process.

[0041] Purging can be initiated, in particular, depending on the hydrogen consumption at a hydrogen consumer. If the hydrogen consumption at the hydrogen consumer falls below a defined threshold, a purging process can be initiated preventively, in particular to prevent a purging process at a later time from limiting the hydrogen gas release rate and preventing the hydrogen consumer from being supplied with sufficient hydrogen gas. This makes it possible, in particular, to initiate a purging process early on in light of increasing catalyst deactivation.It is particularly advantageous if the hydrogen released to a reduced extent during purging covers the needs of the hydrogen consumer, whereby the hydrogen consumer requires in particular no more than 30% of the hydrogen release rate based on a nominal operating point, in particular no more than 20%, in particular no more than 10% and in particular no more than 5%.

[0042] The initiation of purging can also be determined based on the changed volume flow of hydrogen gas in a defined time interval. The change in volume flow relates in particular to a stationary, specific operating point of the system. It is understood that the absolute volume flows can vary depending on the design of the respective system. The lower the stored released amount of hydrogen gas per time interval, the greater the relative deactivation of the catalyst material. It is possible to define limit values ​​or tolerance ranges that trigger the initiation of purging. For example, purging can be initiated when the hydrogen release rate is reduced by a maximum of 0.5% / h, in particular a maximum of 0.1% / h, in particular a maximum of 0.01% / h, and in particular a maximum of 0.001% / h.

[0043] Alternatively, a limit value or tolerance range can also be considered for the amount of hydrogen carrier medium or hydrogen gas used relative to the catalyst material. This consideration is independent of the reaction time. Due to the non-linear relationship between concentration and reaction rate, a non-linear decrease in hydrogen storage or hydrogen release can be observed with a constant decrease in the rate constant. The decrease in hydrogen storage or hydrogen release increases accordingly with a constant decrease in the rate constant over time. Exceeding a defined limit value can be used to initiate purging. During hydrogenation and / or dehydrogenation, purging can be initiated in particular when a relative hydrogen storage capacity decreases by 5% per kg (H2) / kg (catalyst), in particular by a maximum of 1%, in particular by a maximum of 0.1%.Based on the amount of hydrogen carrier medium used, purging is initiated when the relative storage capacity decreases by 1% per kg (hydrogen carrier medium) / kg (catalyst material), in particular 0.1% and in particular 0.01%.

[0044] A comparison of the current hydrogen storage performance or hydrogen release performance relative to a baseline level of the respective performance can also be used to initiate purging. In particular, purging is initiated as soon as the current performance value is less than

[0045] 80% of the initial value.

[0046] Purging can also be initiated if the storage of hydrogen or the release of hydrogen within a steady-state operating point reaches or falls below a previously defined deactivation limit. In general, the deactivation limit can be related to a time interval, to a specific performance of the catalyst and / or the hydrogen carrier medium, or to relative limits depending on a nominal power point. A reduction in the relative hydrogen performance of at least 10%, in particular of at least 1.0%, in particular of at least 0.1%, and in particular of at least 0.01%, relative to the output power can be considered.

[0047] A process according to claim 4 simplifies a direct transition of the various process steps, in particular a flexible change from catalytic hydrogenation or catalytic dehydrogenation to rinsing the catalyst material.

[0048] A method according to claim 5 enables targeted purging of the catalyst material. In particular, purging is performed based on measured values ​​that indicate an impending and / or already occurring deactivation of the catalyst material. This ensures, on the one hand, that purging is performed in a timely manner, especially before the catalyst material is insufficiently deactivated. On the other hand, it is guaranteed that purging is performed only when necessary. The effort required for unnecessary purging processes is reduced.

[0049] A method according to claim 6 can be advantageously integrated into a process sequence, in particular an automated one.

[0050] A method according to claim 7 enables the direct reuse of the flushing medium, in particular as a hydrogen carrier medium. Cleaning of the flushing medium can be carried out in particular on site, i.e. at the location of the plant where the reactor is arranged. Cleaning can also be carried out spatially separated, in particular at another location. A cleaning unit used for cleaning is particularly advantageous if the flushing medium is at least partially loaded with hydrogen carrier medium. Since the catalyst-deactivating substances to be removed are aromatic, cleaning is advantageous due to different physiochemical properties if the flushing medium contains at least a portion of saturated hydrocarbons and in particular consists exclusively of saturated hydrocarbons.

[0051] Spatially separated and separate purification of the rinsing medium is particularly advantageous when the rinsing medium is heavily contaminated. With increasing proportions of byproducts in the rinsing material and / or with longer rinsing times and a correspondingly higher amount of contaminated rinsing material, the cost of the on-site rinsing process increases. A spatially separated, particularly centralized purification unit, to which several reactors can be connected and / or which can be supplied with contaminated rinsing material from several reactors, is then particularly efficient in terms of purification performance. This type of purification is economically efficient.The economic efficiency is particularly advantageous when the proportion of contamination in the rinsing medium is at least 0.2%, in particular at least 0.5%, in particular at least 1%, in particular at least 3%, in particular at least 5%, in particular at least 10%, in particular at least 15% and in particular at least 20%.

[0052] The purification unit can be combined with either a dehydrogenation reactor or a hydrogenation reactor. A purification unit with appropriate sensors is particularly preferred upstream of the reactor, i.e., before the reactor inlet. Remaining catalyst-deactivating substances, which are carried over from the dehydrogenation process to the hydrogenation process, can thus be removed from the fluid stream.

[0053] A method according to claim 8 enables at least temporary continuation of reactor operation during purging. It has been recognized that the reactor can also be operated at least at reduced power during purging. In particular, the relative hydrogen gas release or storage rate is at most 80% based on nominal operation, in particular at most 75% and in particular at most 70%. The nominal load is a defined power with which a plant can be operated at a steady-state standard operating point. The nominal load is determined, in particular, on a plant-specific basis. For example, a nominal load point of a dehydrogenation plant can mean a release rate of 1 kg (H2) / h. In purging operation, a reduction in the release rate of 50% results in a corresponding release of 0.5 kg (H2) / h.

[0054] A method according to claim 9 enables an average power corresponding to a nominal power of 100%. It has been recognized that, during regular operation of the plant, a power above the nominal power can be set, in particular of at least 102% of the nominal power, in particular of at least 105%, and in particular of at most 110%. This comparatively slight excess of the nominal power is unproblematic for the plant. In particular, the plant is designed for a slight excess of the nominal power. Continuous operation in this power range does not lead to damage to the infrastructure, in particular to the reactor. Damage to the hydrogen carrier medium can also be ruled out.By operating the system at increased power during hydrogenation or dehydration, regular flushing cycles can be performed at reduced power, with the average or effective power still corresponding to the nominal power. Regular flushing does not impair the nominal load.

[0055] A method according to claim 10 enables an increase in the activity level of the catalyst material. It has been recognized that the effectiveness of a purging process is limited. During oxidative regeneration, organic residues on the catalyst material are burned off to achieve greater reactivation. In particular, oxidative regeneration produces no or at most small amounts of contaminated hydrogen carrier medium.

[0056] In particular, it was recognized that hydrogen in the dehydrogenation reactor can have a beneficial effect on catalyst regeneration. Hydrogen can, for example, be released during purging due to the dehydrogenation activity of the purging medium. Additionally or alternatively, hydrogen can be added separately. The presence of hydrogen reduces coke formation on the catalyst material. The presence of hydrogen also supports the regeneration of already coked catalyst material. Furthermore, it was found that the separate addition of hydrogen can prevent excessive reaction temperatures. These elevated reaction temperatures would be necessary if the dehydrogenation were carried out with at least partially deactivated, due to coking, catalyst material.The elevated temperatures would lead to an increased vapor content of the discharged hydrogen carrier medium and adversely affect catalyst stability. These problems are resolved by the addition of hydrogen gas.

[0057] Additionally or alternatively, rinsing with steam is possible.

[0058] A system according to claim 11 essentially has the advantages of the method according to claim 1, to which reference is hereby made.

[0059] A system according to claim 12 enables uncomplicated provision of the flushing medium. It is advantageous if the system has several storage containers in which the flushing medium, i.e. the additional hydrogen carrier medium, is stored depending on the degree of hydrogenation. For this purpose, it is advantageous if the degree of hydrogenation of the hydrogen carrier medium is measured or determined by means of a measuring unit. The degree of hydrogenation-dependent storage of the flushing medium enables the degree of hydrogenation of the flushing medium to be changed during flushing, i.e. in particular, the dehydrogenation of the flushing medium during the flushing process. Alternatively, it is possible to feed the flushing medium into one or more storage containers regardless of the actual degree of hydrogenation and mix them there. The measurement of the degree of hydrogenation of the hydrogen carrier medium is described, for example, in EP 3 218 711 B1.

[0060] A return line ensures, in particular, a continuous flow of flushing medium over the catalyst material. Fresh flushing medium can be added flexibly, particularly depending on the amount of contamination from catalyst-deactivating substances. Contaminated flushing medium can be removed from the circuit.

[0061] Alternatively, flushing medium can be passed over the catalyst material in the reactor as a throughflow. The contaminated flushing medium discharged from the reactor, particularly containing catalyst-deactivating substances, can be fed to a separate purification unit and cleaned there. This variant ensures that fresh, unused flushing medium is always available. The efficiency of the flushing process is increased.

[0062] A system according to claim 13 extends the possibilities, in particular with regard to the automated implementation of the method.

[0063] A system according to claim 14 enables the early detection of the deactivation of the catalyst material.

[0064] A system according to claim 15 enables the reuse of the flushing medium.

[0065] Both the features specified in the patent claims and the features specified in the exemplary embodiments of a system according to the invention are suitable, either individually or in combination with one another, for further developing the subject matter of the invention. The respective combinations of features do not represent any limitation with regard to further developments of the subject matter of the invention, but are essentially merely exemplary in nature.

[0066] Further features, advantages, and details of the invention will become apparent from the following description of an embodiment with reference to the drawings. They show:

[0067] Fig. 1 is a schematic representation of a system according to the invention,

[0068] Fig. 2 is a schematic representation of the functional relationship of a hydrogen gas release rate in the plant according to Fig. 1 as a function of the time of day in a first operating mode,

[0069] Fig. 3 shows a representation corresponding to Fig. 2 in a second operating mode. A system, designated as a whole by 1 in Fig. 1, serves for the catalytic storage or release of hydrogen gas using a hydrogen carrier medium.

[0070] Plant 1 comprises a reactor 2, which, according to the illustrated embodiment, is designed as a dehydrogenation reactor. Reactor 2 can also be designed as a hydrogenation reactor.

[0071] In the reactor 2, a catalyst material (not shown in detail) is arranged, which is contacted with the hydrogen carrier medium for catalytic dehydrogenation.

[0072] A first storage tank 3 is connected to the reactor 2 via a supply line 4. Hydrogen carrier medium can be supplied from the first storage tank 3 into the reactor 2 via the supply line 4. The first storage tank 3 stores, in particular at least partially loaded and in particular fully loaded, hydrogen carrier medium.

[0073] A discharge line 5 is connected to the reactor 2, which leads into a second storage tank 6. The second storage tank 6 stores hydrogen carrier medium that has undergone a catalytic reaction, i.e., catalytic dehydrogenation, in the reactor 2. The second storage tank 6 stores at least partially discharged hydrogen carrier medium.

[0074] The use of two separate storage containers 3, 6 enables the hydrogen carrier medium to be stored depending on its degree of hydrogenation. More than two storage containers can also be used to separately store intermediate stages of the hydrogen carrier medium, i.e., those with different degrees of hydrogenation. It is also possible to use only one storage container, in which the at least partially loaded and the at least partially discharged hydrogen carrier medium are stored together, in particular mixed.

[0075] System 1 has a third storage tank 7, which serves to store flushing medium. The flushing medium storage tank 7 is fluidically connected bidirectionally to the discharge line 5 via a branch line 8.

[0076] The use of the third storage container 7 is particularly advantageous when the hydrogen carrier medium used as the flushing medium is fundamentally different from the hydrogen carrier medium to be dehydrogenated in the reactor 2 and / or when the purification of the flushing medium is to be carried out decoupled, in particular outside the plant 1, in particular at a remote location and / or when the flushing medium is not to be mixed with the hydrogen carrier medium as a reactant or product.

[0077] However, it is also possible for the flushing medium to be of the same type, and in particular identical to the hydrogen carrier medium to be dehydrogenated. In this case, it is particularly advantageous if separate storage tanks can be dispensed with. In particular, a single storage tank is sufficient, in which the at least partially loaded and at least partially discharged hydrogen carrier medium and the flushing medium of the same type are stored.

[0078] It is also conceivable, in principle, to use separate storage tanks for fresh and used flushing medium. If hydrogen carrier medium is used as the flushing medium, the first storage tank 3 can be used as the flushing medium storage tank. The flushing medium storage tank 7 then serves as the storage tank for contaminated flushing medium, i.e., used flushing medium that is removed from the hydrogen carrier medium circuit.

[0079] Also connected to the discharge line 5 is a return line 9, which opens with a first return line branch 10 into the first storage tank 3 and with a second return line branch 11 into the feed line 4 and / or directly into the reactor 2.

[0080] A first sensor unit 12, a cleaning unit 13, and a second sensor unit 14 are arranged on the discharge line 5 along the fluid flow direction. The return line 9 branches off from the discharge line 5 in an area between the second sensor unit 14 and the second storage tank 6. The flushing medium storage tank 7 is connected, in particular, directly to the first sensor unit 12 via the branch line 8.

[0081] The first sensor unit 12 serves to detect a proportion of catalyst-deactivating substances in the flushing medium. According to the exemplary embodiment shown, the first sensor unit is designed, in particular, as an optical analysis unit, in particular a photometer, an infrared spectrometer, a Raman spectrometer, or a fluorescence spectrometer. It has been recognized that the substances flushed away by the catalyst material cause a discoloration of the inherently transparent, colorless flushing medium. In particular, the substances cause a yellowish to reddish discoloration of the flushing medium. The flushed-off substances can be detected by detecting this discoloration, in particular in an automated manner.

[0082] The first sensor unit 12 is in signal communication with a control / regulation unit 15, which is indicated in Fig. 1 by the symbol 16 as a wireless signal connection. The signal connection can also be wired.

[0083] To evaluate the measurement result determined by the first sensor unit 12, a reference sensor unit 17 is arranged upstream of the reactor 2, in particular along the feed line 4. The reference sensor unit 17 is designed, in particular, identically to the first sensor unit 12. The reference sensor unit 17 can measure the discoloration of the, in particular unused, rinsing medium. Based on a relative discoloration of the rinsing medium, the contamination of the rinsing medium can be detected and, in particular, calculated by comparing the measured data from the first sensor unit 12 and the reference sensor unit 17.

[0084] The control / regulation unit 15 is in particular in signal communication with the reactor 2 in order, for example, to adapt the reaction conditions in the reactor 2, in particular the reaction pressure. The control / regulation unit 15 outputs in particular a control signal for initiating the purging process. In the event of a pressure increase, the amount of hydrogen released during dehydrogenation is not released from the reactor 2, or at least only to a reduced extent, resulting in the pressure increase in the reactor 2. This reduces the hydrogen release rate in the reactor. The generation of the pressure increase can be accelerated by returning hydrogen gas at a sufficient pressure level from a hydrogen gas buffer storage to the reactor 2 in order to increase the pressure in the reactor 2.

[0085] Additionally or alternatively, a reduction in the reaction temperature is possible, in particular by reducing the power of a heating unit provided for reactor 2. Because the dehydrogenation reaction is endothermic, reactor 2 cools at least partially and, in particular, automatically if no, and in particular insufficient, external heat is supplied. The mass flows of the purging medium during the purging process can be specifically influenced via a hydrogen carrier medium supply pump and / or separate pumps installed for the purging process.

[0086] According to the illustrated embodiment, the cleaning unit 13 is designed as an activated carbon adsorber. In the cleaning unit 13, the catalyst-deactivating substances are separated from the flushing medium, particularly by adsorption. The condition of the flushing medium can be detected by means of the second sensor unit arranged downstream of the cleaning unit 13, which is particularly identical to the first sensor unit 12. In particular, the concentration of the contaminating substances in the flushing medium is detected. The second sensor unit 14 is in signal communication, particularly with the control unit 15.

[0087] The measurement result recorded by the second sensor unit 14 serves, on the one hand, as a basis for determining whether the rinsing agent can be fed back into the first storage tank 3 and / or the reactor 2 via the return line 9. However, the measurement result also provides information about the condition of the cleaning unit 13 and, in particular, the adsorption performance of the cleaning unit 13.

[0088] A method for operating reactor 2 is explained in more detail below. Loaded hydrogen carrier medium is fed from the first storage vessel 3 to reactor 2 via the feed line 4, where it is dehydrogenated, i.e., hydrogen gas is released from the hydrogen carrier medium. The hydrogen gas is released when the hydrogen carrier medium contacts a catalyst material present in reactor 2.

[0089] A mixture of at least partially discharged hydrogen carrier medium and released hydrogen gas is discharged from the reactor 2 via the discharge line 5. The at least partially discharged hydrogen carrier medium is stored in the second storage container 6 and can, for example, be reprocessed by further hydrogenation, i.e., loaded with hydrogen. It is advantageous if the mixture of discharging hydrogen carrier medium and hydrogen gas are separated from one another in a separation unit (not shown in detail). The storage of the at least partially discharged hydrogen carrier medium in the second storage container 6 is thereby improved. The released hydrogen gas can be used in a purely schematically shown hydrogen consumer 18, in particular a fuel cell. It is advantageous if the hydrogen consumer 18 is in signal communication with the control / regulation unit 15.

[0090] Hydrogen carrier medium which has been discharged from the reactor 2 but is at least partially, i.e. sufficiently, loaded can be fed back to the reactor 2 via the return line 9 for further dehydrogenation or stored in the first storage tank 3.

[0091] During operation of reactor 2, catalyst-deactivating substances, particularly in the form of aromatic compounds, can form on the catalyst material, especially coking. These substances cause deactivation of the catalyst material and thus a reduction in reactor performance.

[0092] A decrease in reactor power can be detected, for example, by means of the control unit 15, for example by detecting the volume flow of the hydrogen gas released in and discharged from the reactor 2 per unit of time. If a definable threshold value is undershot, a purging process can be initiated to purge the catalyst-deactivating substances from the catalyst material. To carry out the purging, purging medium is fed from the purging medium storage tank 7 to the reactor 2 via the discharge line 5, the return line 9, and the second return line branch 11. The purging medium is, in particular, a hydrogen carrier medium. In a particularly preferred embodiment, the purging medium is a low-boiling hydrogen carrier medium such as methylcyclohexane or toluene.In particular, the supply of the hydrogen carrier medium used for dehydrogenation is stopped during purging and only resumed after the purging process has ended. However, since the purging medium is a hydrogen carrier medium that is fundamentally suitable for dehydrogenation in reactor 2, a separation of the material flows with respect to dehydrogenation on the one hand and purging on the other is unnecessary. In particular, switching from dehydrogenation to purging occurs directly by increasing the pressure in reactor 2.

[0093] The advantages of dynamic switching of individual operating modes and the elimination of the need to separate the flushing medium and hydrogen carrier medium are particularly advantageous when using a hydrogen carrier medium as the flushing medium that is of the same or identical type to the hydrogen carrier medium to be dehydrogenated, especially benzyltoluene. When using dissimilar hydrogen carrier media as flushing media, and especially dissimilar flushing media, the basic control mechanisms are similar. However, to prevent mixing between the flushing medium and the hydrogen carrier medium, separate fluid circuits are advantageous, particularly the segregation of contaminated flushing medium in a separate flushing medium storage tank.

[0094] The flushing medium discharged from reactor 2, which contains the flushed-out catalyst-deactivating substances, is analyzed by the first sensor unit 12, i.e., the proportion of catalyst-deactivating substances is measured, in particular by comparing it with the reference measurement in the reference sensor unit 17. For this purpose, it may be advantageous if the flushing medium is conducted from the flushing medium storage tank 7 via a separate line through the reference sensor unit 17 before the flushing medium is fed to the reactor 2. Additionally or alternatively, a sensor (not shown) for measuring the catalyst-deactivating substances could be arranged along the return line 9.

[0095] The duration of the purging can be time-controlled. Purging can also be terminated, in particular, when the proportion of catalyst-deactivating substances in the purging medium is reduced and, in particular, when no catalyst-deactivating substances are detected. The reduction in these substances can be detected by the first sensor unit 12.

[0096] A dynamic switch back from rinsing mode to dehydration mode is possible, particularly under the control of the control unit 15. The rinsing medium containing the contaminating substances is cleaned in the cleaning unit 13, and the cleaning progress is recorded by the second sensor unit 14. Particularly when the rinsing cycle is completed, the rinsing medium cleaned in the cleaning unit 13 is returned to the rinsing medium storage tank 7 via a rinsing medium storage line 19.

[0097] High-boiling hydrogen carrier media, particularly dibenzyltoluene or perhydrodibenzyltoluene, can also be used as the purge medium. It has been found that purification of the purge medium in the purification unit 13 is simplified. Furthermore, the liquid phase fraction of the purge medium in reactor 2 can be easily increased.

[0098] It is advantageous if the cleaning unit 13 is regenerated, particularly at regular intervals and / or depending on the measurement result recorded by the second sensor unit 14. Regeneration of the cleaning unit 13 can be achieved, in particular, by counter-flushing, so that, in particular, the activated carbon adsorber can be released again.

[0099] It is therefore particularly advantageous if the system 1 comprises at least two cleaning units 13, which are arranged, in particular, parallel to one another in the fluid flow. This makes it possible to regenerate one of the cleaning units 13 and simultaneously use the at least one other cleaning unit 13 to clean the flushing medium. System downtime due to the required regeneration of the cleaning unit 13 is thus avoided. The overall efficiency of the process is thereby increased.

[0100] As shown in Fig. 2, it is advantageous if reactor 2 is operated with a hydrogen gas release rate r(t) greater than 100%. According to the illustrated embodiment, the hydrogen gas release rate in dehydrogenation mode TD is 105%. The release rate in dehydrogenation mode is therefore 5% above the nominal release rate r. nOm of 100% and thus above the nominal power of the dehydrogenation reactor. From Fig. 2, it can also be seen that purging takes place at the end of a working day, i.e., after approximately twenty hours of operation of reactor 2. During purging operation, the hydrogen gas release rate rs is approximately 75%. Because the hydrogen gas release rate in dehydrogenation operation TD is above the nominal hydrogen gas release rate r nO m, the average hydrogen gas release rate is r m exactly the nominal hydrogen gas release rate r nOm of the dehydrogenation reactor 2. Fig. 3 shows an alternative operating mode in which several purge cycles are distributed over a working day. According to the illustrated embodiment, four purge cycles take place, in particular regularly every five hours. As in the previous example, during purge operation, the hydrogen gas release rate rs is temporarily reduced to approximately 75% of the nominal hydrogen gas release rate r nO m. Due to the fact that in regular dehydrogenation operation the hydrogen gas release rate TD is above the nominal hydrogen gas release rate r nO m, especially at 105%, the average hydrogen gas release rate r m corresponding to the nominal hydrogen gas release rate r nO m of the dehydrogenation reactor 2.

Claims

Patent claims 1. A method for operating a reactor comprising a catalyst material, comprising the process steps of catalytic hydrogenation or catalytic dehydrogenation of hydrogen carrier medium by contacting the catalyst material with the hydrogen carrier medium in the reactor (2), Flushing the catalyst material with a flushing medium in the reactor (2) and thereby removing catalyst-deactivating substances, wherein the flushing medium comprises a hydrogen carrier medium.

2. Method according to claim 1, characterized in that rinsing properties are determined in a targeted and variable manner depending on material properties of the rinsing medium, in particular the physiochemical properties of the rinsing medium.

3. Process according to one of the preceding claims, characterized in that during the purging in the reactor (2) a purge temperature (Ts) between 100 °C and 350 °C, in particular between 150 °C and 330 °C and in particular between 200 °C and 300 °C, and / or a purge pressure (ps) for the dehydrogenation between 0.5 barg and 6.0 barg, in particular between 0.8 barg and 5.5 barg and in particular between 1.0 barg and 5.0 barg, and / or a purge pressure (ps) for the hydrogenation between 0.5 barg and 50 barg, in particular between 5 barg and 40 barg and especially between 10 barg and 30 barg.

4. Method according to one of the preceding claims, characterized in that the rinsing takes place under a hydrogen atmosphere, the proportion of hydrogen gas in the total pressure being at least 10%, in particular at least 50% and in particular at least 90%.

5. Method according to one of the preceding claims, characterized in that the rinsing is controlled, in particular regulated, by means of a control-Zregulation unit (15). is carried out, in particular as a function of the catalyst activity and / or as a function of the hydrogen consumption at a hydrogen consumer (18). Method according to one of the preceding claims, characterized in that the purging is carried out regularly, in particular in a fixed cycle, in particular several times a working day and / or at the beginning or at the end of a working day. Method according to one of the preceding claims, characterized in that the purging medium comprising the catalyst-deactivating substances is purified in a purification unit (13), wherein the purification unit (13) is designed in particular as an adsorption unit, as a distillation unit and / or as a purification unit with a separation membrane. Method according to one of the preceding claims, characterized in that the purging takes place during a low-power phase of the reactor (2).Process according to one of the preceding claims, characterized in that the catalytic hydrogenation or the catalytic dehydrogenation takes place in a power range above the nominal load. Process according to one of the preceding claims, characterized in that, in particular after the purging, an oxidative regeneration and / or a purging with hydrogen gas and / or a purging with steam takes place. Plant for the catalytic storage or release of hydrogen gas from a hydrogen carrier medium, comprising a. a reactor (2) for the catalytic hydrogenation or for the catalytic dehydrogenation of the hydrogen carrier medium by contacting it with catalyst material, b. a purging medium feed (4, 7) for feeding a purging medium into the reactor.

12. Plant according to claim 11, characterized by a return line (9) for returning hydrogen carrier medium from the reactor (2) as a flushing medium to the reactor (2), wherein a storage tank (3) is connected, in particular, to the return line (9).

13. Plant according to claim 11 or 12, characterized by a control / regulation unit (15) for the controlled and, in particular, regulated execution of the flushing.

14. Plant according to one of claims 11 to 13, characterized by at least one sensor unit (12, 14, 17) for detecting a proportion of catalyst-deactivating substances in the flushing medium, wherein the sensor unit (12, 14, 17) is designed in particular as a photometer and / or as a fluorescence spectrometer and is arranged in particular outside the reactor (2).

15. Plant according to one of claims 11 to 14, characterized by a cleaning unit (13) for cleaning the flushing medium containing the catalyst-deactivating substances.

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