Electrocatalytic hydrogen carrier composition

Abstract

The present invention comprises at least one cyclohexyl compound having at least one unsaturated bond, and optionally one or more C 4-12 A lean liquid organic hydrogen carrier (lean-LOHC) component containing an alkyl alcohol in combination with at least one cyclohexyl compound, optionally containing C 4-7 Ketones, C 4-6 The present invention provides hydrogen carrier fluid (HCF) compositions comprising a rich liquid organic hydrogen carrier (rich-LOHC) component containing lactones or mixtures thereof, and an electrolyte component. The invention also provides the use of these HCF compositions for hydrogen storage and release in electrochemical reactor systems.

Description

[Technical Field]

[0001] This disclosure relates to hydrogen storage via liquid organic hydrogen carriers, as well as to electrochemical cells, batteries, and fuel cells that use hydrogen fuel. More specifically, the present invention relates to liquid organic hydrogen carrier compositions for processing by electrochemical methods. [Background technology]

[0002] Hydrogen is a net-zero fuel widely adopted as an alternative to conventional fossil fuels due to its cleanliness, high energy density, and sustainable, transportable nature, as its production routes are often derived from renewable resources. Hydrogen can be used in many applications to generate electricity and heat by powering fuel cell electric vehicles and stationary energy systems. Hydrogen storage is a crucial technology for the deployment of hydrogen and fuel cell technologies and for accelerating the adoption of clean energy worldwide. Although hydrogen has the highest energy per unit mass of all fuels, its low volumetric density makes hydrogen storage one of the major barriers to the widespread use of hydrogen in portable and stationary applications.

[0003] Achieving high-density hydrogen storage is a critical challenge not only for portable and stationary applications but also for long-distance transportation. Currently available technologies are generally based on gaseous hydrogen storage and require large-capacity systems, posing a significant challenge for portable applications. Over the past decade, substantial investments in hydrogen storage research and practical development have led to the development of commercially available solutions that chemically bond hydrogen to molecules of solid / liquid materials such as metal hydrides and liquid organic hydrogen carriers (LOHCs).

[0004] Hydrogen storage in LOHC is a promising technology that does not require extremely high pressure and / or high temperature, and allows for the safe storage of hydrogen for extended periods, with a hydrogen storage density per unit volume comparable to that of cryogenic liquefied hydrogen. Because LOHC and crude oil derivatives have similar properties at room temperature, it is possible to transport high-density hydrogen in LOHC using existing gasoline and diesel fuel supply infrastructure, reducing operating costs compared to compressed or liquid hydrogen.

[0005] Liquid organic hydrogen carriers (LOHCs) refer to compounds that can absorb and release hydrogen through chemical reactions. Such compounds include at least partially unsaturated hydrocarbons (also known as lean LOHCs), which can be hydrogenated, for example, at a hydrogen source site to provide a storable and transportable fluid in the form of a corresponding (more) saturated hydrocarbon (also known as rich LOHC). Saturated hydrocarbons can be dehydrogenated at the site of use to release hydrogen, forming a hydrogen-depleting fluid containing at least partially unsaturated hydrocarbons, which are then transferred to a hydrogen source site where they are converted to saturated form by a hydrogenation process. Common carrier fluids include, for example, cyclohexane / benzene, methylcyclohexane / toluene, cyclohexanol / phenol, and "molecular pairs" in hydrogenated and dehydrogenated forms, such as decalin / naphthalene, butanol / butanone, cyclohexanol / cyclohexenol, and cyclohexanol / cyclohexenone.

[0006] Hydrogen storage and release in LOHCs are based on a two-step cycle of hydrogenation and dehydrogenation via thermal or electrocatalytic reactions. While thermal catalytic hydrogenation and dehydrogenation in LOHCs require relatively high pressure and temperature, electrocatalytic reactions are simpler and potentially more efficient processes that proceed at room temperature. Therefore, electrocatalytic LOHC systems powered by electrical energy make rechargeable storage systems suitable for off-grid and decentralized hydrogen applications.

[0007] In a typical LOHC system, lean LOHC reacts with hydrogen during the hydrogenation reaction to produce rich LOHC, and the reverse reaction occurs during the dehydrogenation reaction. In an electrochemical system, this can be further explained by half-reactions occurring at the anode and cathode, as follows: where X is the number of hydrogen atoms added to / removed from the LOHC during the hydrogenation / dehydrogenation reaction. TIFF2026514565000002.tif77170

[0008] Electrochemical reactors are used for hydrogen gas production through electrolysis and in industrial processes (e.g., water treatment). While these electrochemical storage systems can store hydrogen stably and with low energy consumption, their applications are limited due to the low density of the stored hydrogen.

[0009] The application of electrochemical conversion to hydrogen transport in solution has been largely unstudied. Recent reports from Yokohama National University have studied the hydrogenation of toluene using a polymer electrolyte membrane (PEM) electrochemical reactor (Fukazawa et al., Bull. Chem. Soc. Jpn., 2018, 91 (6) pp. 897-899, Takano, et al., Bull. Chem. Soc. Jpn. 89 pp. 1178-1183, 2016). These early reports have limitations in demonstrating complete LOHC conversion or stable performance.

[0010] Therefore, there is a need for improved hydrogen storage and release systems, and hydrogen carriers designed for electrochemical reactors, that can overcome one or more limitations of existing technologies.

[0011] This background information is provided for the purpose of making public information that the applicant believes may be relevant to the present invention. It is not necessarily intended, nor should it be construed, that any of the aforementioned information constitutes prior art to the present invention. [Overview of the project]

[0012] The object of the present invention is to provide hydrogen carrier fluid compositions designed for storing and releasing hydrogen in systems and methods using electrochemical reactors.

[0013] According to one aspect of the present invention, a) comprises at least one cyclohexyl compound having at least one unsaturated bond, and optionally one or more C 4-12 Lean liquid organic hydrogen carrier (lean-LOHC) components included in combination with alkyl alcohols, or optionally C 4-7 Ketones, C 4-6 The following are provided: a) a rich liquid organic hydrogen carrier (rich-LOHC) component comprising a lactone or a combination thereof of at least one cyclohexyl compound, and a) a hydrogen carrier fluid (HCF) composition comprising an electrolyte component.

[0014] According to another aspect of the present invention, the use of the HCF composition described herein is provided for storing and releasing hydrogen in an electrochemical reactor system. [Brief explanation of the drawing]

[0015] Further features and advantages of this disclosure will become apparent from the following detailed description in conjunction with the attached drawings. [Figure 1] Figure 1 is a schematic diagram of the hydrogenation and dehydrogenation reactions of the LOHC component of a hydrogen carrier fluid (HCF) composition according to one embodiment of the present invention. [Figure 2] Figure 2 shows a cyclic voltammogram relating to the electrochemical dehydrogenation of LOHC components according to one embodiment of the present invention. [Figure 3] Figure 3 shows a linear scanning voltammogram relating to the electrochemical dehydrogenation of LOHC components according to one embodiment of the present invention. [Figure 4] Figure 4 shows a cyclic voltammogram relating to the electrochemical dehydrogenation of LOHC components according to one embodiment of the present invention. [Modes for carrying out the invention]

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0017] Unless the context dictates otherwise, throughout this specification and the claims, the terms "comprise", "comprising", and the like are to be construed in an open and inclusive sense.

[0018] As used herein, the articles "a" and "an" are used to refer to one or more than one (i.e., at least one) of the grammatical objects of the article. For example, "an element" means one element or more than one element.

[0019] As used herein, the term "about" refers to a variation of about ±10% from a given value. Such variations are understood to be always included in any value provided herein, whether or not specifically stated.

[0020] The present invention provides a hydrogen carrier fluid (HCF) composition for use in an electrocatalytic reactor system that enables hydrogenation / dehydrogenation reactions in a method / system for storing and releasing hydrogen.

[0021] In one aspect, the present invention is one or more C 4-12 A lean liquid organic hydrogen carrier (lean-LOHC) component optionally combined with an alkyl alcohol, or C 4-7 A ketone, C 4-6 A rich liquid organic hydrogen carrier (rich-LOHC) component optionally combined with a lactone or a mixture thereof, and an electrolyte component, to provide a hydrogen carrier fluid (HCF) composition.

[0022] The lean liquid organic hydrogen carrier (lean-LOHC) component comprises at least one cyclohexyl-based compound having at least one unsaturated bond.

[0023] Rich liquid organic hydrogen carrier (rich-LOHC) components contain at least one cyclohexyl-based compound.

[0024] As used herein, the term "cyclohexyl compound" refers to a monocyclic compound or a fused ring compound, both of which may be optionally substituted with one or more OH groups and / or alkyl groups.

[0025] A condensed cyclohexyl compound comprises at least two condensed cyclohexyl rings, or a cycloalkyl ring, and a five-membered or six-membered heterocycle having at least one heteroatom such as N, O, or S, wherein the cyclohexyl ring may optionally be substituted with one or more OH groups and C1-C6 alkyl groups.

[0026] The substituents on the cyclohexyl ring may be further substituted with cyclohexyl or a 5-membered or 6-membered N-heterocyclic group.

[0027] Non-exclusive examples of cyclohexyl compounds suitable for use in rich-LOHC components include cyclohexane, methylcyclohexane, decalin, cyclohexanol, decahydro-N-alkylcarbazole, and alkylperhydroindole.

[0028] Non-limiting examples of cyclohexyl compounds suitable for use in lean-LOHC components having at least one unsaturated bond include cyclohexene, cyclohexanol, benzene, toluene, naphthalene, phenol, benzyltoluene, dibenzyltoluene, biphenyl, N-alkylcarbazole, alkylindole, and others.

[0029] In some embodiments, the rich-LOHC component comprises cyclohexane, methylcyclohexane, cyclohexanol, or a mixture thereof. In some embodiments, the rich-LOHC component comprises cyclohexanol or methylcyclohexane.

[0030] In some embodiments, the lean-LOHC component comprises cyclohexene, methylcyclohexene, cyclohexenol, cyclohexanone, phenol, or a mixture thereof. In some embodiments, the lean-LOHC component comprises phenol.

[0031] In some embodiments, the lean-LOHC component comprises methylcyclohexene, toluene, or a mixture thereof. In some embodiments, the lean-LOHC component comprises phenol.

[0032] Alcohols suitable for use in the lean-LOHC component are C 4-12 monohydroxyalkyl alcohols, C 4-12 polyhydroxyalkyl alcohols, or a mixture thereof.

[0033] In some embodiments, the alcohol is n-butanol, 2-butanol, n-pentanediol, 2-pentanol, 3-pentanol, or a mixture thereof. In some embodiments, the alcohol is n-butanol.

[0034] In some embodiments, ketones suitable for use in the rich-LOHC component are butanone, pentanone, pentanedione, or a mixture thereof.

[0035] In some embodiments, the ketone is butanone, pentanedione, or a mixture thereof. In some embodiments, the lactone is gamma-butyrolactone, delta-valerolactone, or a mixture thereof. In some embodiments, the lactone is delta-valerolactone.

[0036] Electrolyte components suitable for use in the HCF composition can include alkali metal salts, alkaline earth metal salts, ammonium salts, C 6-14 alkyl-C 6-10 -aryl sulfonic acids, or a mixture thereof.

[0037] In some embodiments, the electrolyte component includes alkali metal salts, alkaline earth metal salts, ammonium salts, or mixtures thereof.

[0038] In some embodiments, the alkali metal is lithium, sodium, or potassium.

[0039] The ammonium component of ammonium salts is NR4 + It can be defined as follows, where R is H or one or more C 1-4 It is selected independently of alkyl groups.

[0040] Non-limiting examples of counterions for alkali metal salts, alkaline earth metal salts, or ammonium salts include hydroxide anions, perchlorate anions, borate anions, carbonate anions, or acetate anions.

[0041] In some embodiments, the electrolyte component is an alkali metal or alkaline earth metal perchlorate. In some embodiments, the electrolyte component is lithium perchlorate.

[0042] In some embodiments, the electrolyte component is tetrabutylammonium hydroxide. In some embodiments, the electrolyte component is dodecyl sulfonic acid.

[0043] In some embodiments, the HCF composition further comprises a transition metal complex or a post-transition metal complex.

[0044] In some embodiments, the transition metal is Pd, Ru, V, Fe, Mn, or Ni. In some embodiments, the post-transition metal is Al.

[0045] In some embodiments, the transition metal complex is Pd-pivalate (Pd-trimethylacetate).

[0046] In some embodiments, the HCF composition further comprises an organic redox mediator.

[0047] As used herein, the terms “organic redox mediator” or “catalyst” include compounds that form stable organic radicals that function as intermediate electron carriers or reservoirs without altering the final product of the electrochemical reaction of LOHCs. These compounds are regenerated on the electrode surface.

[0048] Non-limiting examples of organic redox mediators include quinones (such as benzoquinone, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, and naphthoquinone), TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl), N-hydroxyphthalimide, and C 1-6 Trialkylamine, C 1-6 Dialkylamine, C 1-8 Contains diamines, etc.

[0049] In some embodiments, the organic redox mediator is triethylamine, N,N'-dimethyl-1,3-propanediamine, or N-hydroxyphthalimide.

[0050] In some embodiments, the HCF composition includes a solvent. In some embodiments, the solvent is water.

[0051] The HCF composition may contain up to approximately 90% by weight of lean-LOHC components, up to approximately 60% by weight of alcohols, up to approximately 20% by weight of electrolyte components, up to 5% by weight of transition metals or post-transition metal complexes / compounds, and up to 5% by weight of redox mediators.

[0052] In some embodiments, the composition comprises about 40% to 90% by weight of a rich-LOHC component, about 20% to 60% by weight of ketones, lactones, or mixtures thereof, about 1% to 20% by weight of an electrolyte component, about 0.5% to 5% by weight of a transition metal or post-transition metal complex / compound, and about 0.5% to 5% by weight of a redox mediator.

[0053] While not bound by theory, it is thought that alcohols act as dispersants and / or liquid organic hydrogen carriers, and that electrolyte components mitigate capacitive charge generation.

[0054] In some embodiments, the alcohol acts as a hydrogen carrier and is reversibly dehydrogenated / hydrogenated between the alcohol and a ketone or lactone form, for example, butanol is converted to butanone, and pentanediol is converted to gamma valerolactone or pentanedione.

[0055] In another aspect, the present invention provides the use of HCF compositions for hydrogen storage and release in electrocatalytic reactor systems / methods.

[0056] When used in an electrocatalytic reactor system and method, the LOHC component of the HCF composition of the present invention can be circulated between a hydrogenated form (rich-LOHC) and a dehydrogenated form (lean-LOHC) using a hydrogenation reactor (H-reactor) and a dehydrogenation reactor (D-reactor).

[0057] HCF compositions can be transported by pipeline, truck, train, or personal tank, depending on the end-use. Lean LOHC can be rehydrogenated at facilities or hydrogen refueling hubs. Rich LOHC can be used on-site to produce hydrogen fuel for power generation, heating, or other hydrogen gas end-uses.

[0058] In some embodiments, the LOHC of the HCF composition of the present invention can be electrochemically dehydrogenated in a dehydrogenation reactor (D-reactor) containing an anode and a cathode to produce lean-LOHC.

[0059] In some embodiments, the HCF composition of the present invention is converted in-situ to produce hydrogen fuel via a D-reactor.

[0060] In some embodiments, the HCF composition of the present invention is transported to the site of the D-reactor via pipeline, concentric pipeline, tanker, personal tank, concentric personal tank, or similar means.

[0061] In some embodiments, the lean-LOHC of the HCF composition is returned to hydrogenation via pipelines, concentric pipelines, tankers, individual tanks, concentric individual tanks, or similar methods.

[0062] In some embodiments, lean-LOHC is rehydrogenated at a refueling hub or similar center using a hydrogenation reactor (H-reactor).

[0063] Although the present invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications are possible without departing from the spirit and scope of the invention. All such modifications that are apparent to those skilled in the art shall be included in the claims.

[0064] To better understand the present invention as described herein, the following examples are provided. It will be understood that these examples are intended to illustrate exemplary embodiments of the present invention and do not limit the scope of the invention in any way.

[0065] Examples Figure 1 shows an LOHC system containing the LOHC compound of the present invention, in which lean-LOHC (i.e., benzene) and ketone or lactone react with hydrogen during hydrogenation to produce rich-LOHC (i.e., cyclohexane) and alcohol, while the reverse occurs during dehydrogenation, with cyclohexane being converted back to cyclohexene and / or benzene, and alcohol being converted to ketone or lactone.

[0066] Example 1 An electrocatalytic HCF formulation, consisting of a 1:1 volume ratio mixture of methylcyclohexane and butanol with 0.1 M tetrabutylammonium hydroxide, was used in a parallel-current electrochemical reactor. The electrodes were made of Ni metal foam coated with a platinum group metal catalyst. The electrodes were connected to a power supply so that adjacent electrodes functioned as a monopolar anode and cathode, with a spacing of 0.3 mm between the electrodes, and a nylon flow distributor was attached. The applied potential increased to 2.5 V at a rate of 0.2 V / s. The electrochemical oxidation of methylcyclohexane and butanol was confirmed as an increase in current above 0.75 V, with the anodic reaction being the oxidation of a liquid organic hydrogen carrier and the cathode reaction being a hydrogen evolution reaction (Figure 2).

[0067] This system operated under chronoamperometric conditions for 2.5 hours with a fixed current of 20 mA and an average applied potential of 2.6 V, converting butanol to butanone (>2%) and methylcyclohexane to methylcyclohexene (<1%) while releasing hydrogen gas at the cathode.

[0068] Example 2 In a beaker-type electrochemical reactor, an electrocatalytic HCF formulation consisting of a mixture of 40 ml each of n-butanol and methylcyclohexane, 16 g of 4-dodecylbenzenesulfonic acid, and 0.15 g of palladium pivalate was used. The working electrode and counter electrode were made of Ni metal foam coated with a platinum group metal catalyst. A dummy reference electrode was a silver wire. The electrodes were connected to a potentiostat (Admiral Ace) and functioned as monopolar anode and monopolar cathode, with a distance of 3-5 mm between the electrodes. The applied potential was increased from -0.15 V to 1.5 V at a rate of 0.2 V / s. The electrochemical oxidation of methylcyclohexane and butanol was observed as an increase in current starting from -0.15 V, with the anodic reaction being the oxidation of a liquid organic hydrogen carrier and the cathode reaction being a hydrogen evolution reaction (Figure 3). At potentials above 0.2V, it was observed that the current remained constant at 1.6mA relative to the Ag pseudo-reference potential due to the mass transport limit of one or more chemical species. This system was operated under chronoamperometry conditions for 4 hours with a fixed current of 1mA and an average applied potential of 1V, resulting in the conversion of butanol to butanone (>5%) and methylcyclohexane to methylcyclohexene (~1%). Hydrogen gas was generated from the cathode and released into the atmosphere within the laboratory fume hood.

[0069] Example 3 An electrocatalytic HCF preparation containing 30 mg of cyclohexanol, 0.5 M lithium perchlorate, and 8 mg of the redox mediator N-hydroxyphthalimide was diluted in 1.5 ml of acetonitrile and tested in a beaker-type electrochemical reactor. The electrodes consisted of graphite rods with platinum group metal catalysts. The electrodes were connected to a power supply so that adjacent electrodes functioned as monopolar anode and cathode with a 0.2 mm gap between them. The applied potential was increased to 2 V at a rate of 0.05 V / s. Electrochemical oxidation of cyclohexanol was confirmed as an increase in current above 1.1 V, with the anodic reaction being oxidation of a liquid organic hydrogen carrier and the cathode reaction being a hydrogen evolution reaction (Figure 4, HCF with mediator). For comparison, the system was tested with the same electrochemical scanning profile without the addition of the redox mediator (Figure 4, HCF without mediator). This scan shows a significant change in the oxidation initiation voltage (indicated by the increase in current) from approximately 1V to over 1.5V, highlighting the catalytic behavior of the redox mediator in the electrochemical oxidation of HCF. The system was operated for 0.75 hours under chronoamperometry conditions with a fixed current of 2mA and an average applied potential of 1.8V, yielding a conversion of cyclohexanol to cyclohexanone / cyclohexenol (>10%), with less than 1% cyclohexenone and less than 0.1% phenol.

Claims

1. A hydrogen carrier fluid (HCF) composition, a) comprising at least one cyclohexyl compound having at least one unsaturated bond, and optionally one or more C ４－１２ Lean liquid organic hydrogen carrier (lean-LOHC) components composed in combination with alkyl alcohols, or It comprises at least one cyclohexyl compound, and optionally C ４－７ Ketones, C ４－６ A rich liquid organic hydrogen carrier (rich-LOHC) component composed of lactones or mixtures thereof, b) Electrolyte components, A hydrogen carrier fluid composition characterized by containing the following:

2. In the HCF composition according to claim 1, An HCF composition characterized in that the rich-LOHC component comprises cyclohexane, methylcyclohexane, cyclohexanol, or a mixture thereof.

3. In the HCF composition according to claim 1, An HCF composition characterized in that the lean-LOHC component comprises cyclohexene, methylcyclohexene, cyclohexenol, cyclohexanone, phenol, or a mixture thereof.

4. In the HCF composition according to any one of claims 1 to 3, An HCF composition characterized in that the alcohol is butanol, pentanediol, or a mixture thereof.

5. In the HCF composition according to any one of claims 1 to 3, An HCF composition characterized in that the ketone is butanone, pentanedione, or a mixture thereof, and the lactone is delta-valerolactone.

6. In the HCF composition according to any one of claims 1 to 5, The electrolyte components are alkali metal salts, alkaline earth metal salts, ammonium salts, and C ６－１４ Alkyl-C ６－１０ An HCF composition characterized by containing aryl sulfonic acid or a mixture thereof.

7. An HCF composition according to claim 6, characterized in that the counterions of the alkali metal salt, the alkaline earth metal salt, and the ammonium salt are hydroxide anions, perchlorate anions, borate anions, carbonate anions, or acetate anions.

8. An HCF composition according to claim 6, characterized in that the electrolyte component is dodecyl sulfonic acid.

9. An HCF composition according to any one of claims 1 to 8, further comprising a transition metal complex or a post-transition metal complex.

10. The HCF composition according to claim 9, characterized in that the transition metal is Pd, Ru, V, Fe, Mn, or Ni, and the post-transition metal is Al.

11. The HCF composition according to claim 10, characterized in that the transition metal complex is Pd-pivalate (Pd-trimethylacetate).

12. An HCF composition according to any one of claims 1 to 11, further characterized by comprising an organic redox mediator.

13. In the HCF composition according to claim 12, An HCF composition characterized in that the organic redox mediator is benzoquinone, naphthoquinone, N-hydroxyphthalimide, triethylamine, N,N'-dimethyl-1,3-propanediamine, or TEMPO.

14. An HCF composition according to any one of claims 1 to 8, wherein the composition is Approximately 40% to 90% by weight of lean LOHC components, Approximately 20% to 60% by weight of alcohol, Approximately 1% to 20% by weight of electrolyte components, An HCF composition characterized by containing the following:

15. An HCF composition according to any one of claims 1 to 8, An HCF composition comprising approximately 40% to 90% by weight of rich LOHC components, approximately 20% to 60% by weight of ketones, lactones, or mixtures thereof, and approximately 1% to 20% by weight of electrolyte components.

16. In the HCF composition according to claim 14 or 15, Furthermore, approximately 0.5% to 5% by weight of transition metal complexes or post-transition metal compounds / complexes and / or An HCF composition characterized by containing approximately 0.5% to 5% by weight of an oxidation-reduction mediator.

17. Use of the HCF composition according to any one of claims 1 to 16 for hydrogen storage and release.

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