Compositions of organic liquids, uses thereof for transporting and storing hydrogen, and hydrogen generation methods using same

Abstract

The present invention relates to compositions (mixtures) of liquid organic hydrogen carriers (LOHC) and to pairs consisting of an LOHC mixture and corresponding dehydrogenated LOHC(s). The invention also relates to the uses of said mixtures for transporting and storing hydrogen as well as to hydrogen generation methods using same.

Description

[0001] DESCRIPTION

[0002] ORGANIC LIQUID COMPOSITIONS, THEIR USES FOR TRANSPORTING AND STORING HYDROGEN, AND METHODS FOR GENERATING HYDROGEN USING THEM

[0003] The present invention relates to compositions (mixtures) of organic hydrogen-carrying liquids (LOHC), as well as the corresponding LOHC / dehydrogenated LOHC mixture pairs. The invention also relates to their uses for the transport and storage of hydrogen, and to the methods for generating hydrogen using them.

[0004] After more than a century of intensive use of fossil fuels as the predominant energy source, these natural resources are becoming depleted, and there is a growing need to develop alternative energy sources to replace traditional ones. These must be inexpensive, safe, non-polluting, and easy to implement.

[0005] For these reasons, stable organic fluids have been developed that can safely and efficiently store and release an energy fluid, for example a fuel, through a catalytic reaction.

[0006] Containing the highest energy density per unit mass and producing only water when burned or oxidized in a hydrogen-oxygen fuel cell, hydrogen is considered one of the most efficient and environmentally friendly candidates as a future fuel, particularly through on-board dehydrogenation. This can be for light or heavy-duty mobility. The engine can be an H2 combustion engine or a fuel cell.

[0007] Hydrogen is a very energetic compound compared to conventional fossil fuels and burns in air at widely varying concentrations (including 5% to 75%).

[0008] The concept of using hydrogen as an important energy carrier was suggested as early as the 1970s. Transportation, including mass energy transport via hydrogen carrier (many countries have recently shown their willingness to import energy via decarbonized FH2), and stationary hydrogen storage, especially for peak shaving of weekly to annual production / consumption, are key points to access the attractive "hydrogen era." However, a major challenge is finding suitable hydrogen carriers. For decades, scientists have been searching for suitable materials for hydrogen storage. Recently, organic compounds, such as formic acid, methanol-water, formaldehyde-water mixtures, and carbohydrates, have been intensively studied as potential hydrogen storage materials.Among them, organic hydrogen-carrying liquids (OHCLs), which can be dehydrogenated and hydrogenated involving large amounts of hydrogen and could be used for land transportation applications, but also stationary storage, maritime or river transport, and mass transport, are of particular interest.

[0009] In principle, hydrogen is fixed on the hydrogen-poor organic liquid (dehydrogenated LOHC) through a hydrogenation reaction to produce a hydrogen-rich organic liquid (hydrogenated LOHC) which must be a stable liquid under ambient conditions and therefore transportable and storable. The hydrogen-rich organic liquid is then dehydrogenated in a second reaction in order to regenerate the hydrogen and the hydrogen-poor organic liquid. Advantageously, these LOHCs are therefore capable of being reversibly hydrogenated and dehydrogenated in the presence of a catalyst. In addition, thanks to their high volumetric density (50-100 g of hydrogen per liter of hydrogenated LOHC) and mass content (typically 5-7% by mass of hydrogen in the hydrogenated LOHC) and their stability under ambient conditions, it is possible to transport and store them in simple tanks, cisterns or pipelines.The most commonly cited LOHCs are aromatic hydrocarbons and heteroaromatic compounds of the carbazole family. Aromatic hydrocarbons are particularly benzene, toluene, naphthalene, biphenyl derivatives, benzyltoluenes including dibenzyltoluenes (DBT). In their hydrogenated form, they form cyclic alkanes. These compounds have the advantage of having a wide temperature range for their implementation in liquid form, for example from -40°C to more than 300°C for the dibenzyltoluene / perhydrodibenzyltoluene couple. In addition, these aromatic compounds, as well as their cyclic alkanes, exhibit great stability. Finally, certain aromatic compounds such as toluene are produced worldwide on a significant scale (25 Mt / year for toluene), making it possible to rapidly envisage the development of this type of transport for hydrogen.Their hydrogenation is carried out at high pressure and moderate temperature (example of DBT: 40-80 bar, 180°C, -71 kJ / molH2) while dehydrogenation is carried out at atmospheric pressure and higher temperature (example of DBT: 1 bar, 300°C, 71 kJ7molH2). Regarding heteroaromatic compounds of the carbazole family, the most frequent compounds are N-ethyl carbazole (NEC) and furan, pyrrole and indole derivatives. In this case, the hydrogenation reaction leads to cyclic amines or cyclic ethers. However, not all of these compounds are completely satisfactory. Thus, the main high-performance catalysts used during the hydrogenation and dehydrogenation reactions of LOHCs presented above are based on platinum, iridium, rhodium, ruthenium or palladium. However, these metals are not widely available on the planet and are therefore very expensive.Some alternatives using nickel-based catalysts have been proposed, but their low activity (300 to 3000 times lower than ruthenium-based catalysts) is an obstacle to their use in an industrial context. In addition, homogeneous phase catalysts are sometimes used, which does not allow easy separation of the catalyst from the reaction medium.

[0010] Furthermore, the dehydrogenation of conventional hydrogen-rich LOHC carriers consumes at least 17% (NEC) to 25% (DBT) of the gross calorific value (GCV) of the released hydrogen (taking into account only the reaction enthalpy). Therefore, the search for an energetically viable process requires considering thermal integration that limits the use of these compounds. If this thermal integration were not carried out, the energy efficiency of LOHC would not stand out from that of other transport solutions such as compressed or liquefied hydrogen.

[0011] Finally, these compounds are mainly obtained from non-renewable fossil resources, which are being depleted as mentioned above. Therefore, the hydrogen transported by these vectors cannot be considered perfectly decarbonated. Furthermore, polyols have been used as LOHCs, releasing hydrogen by forming ketone derivatives or lactones. However, the gravimetric density of H2 transported by these compounds is relatively low, i.e., less than or much less than 4.4% by mass.

[0012] Wu et al. (Angew. Chem. Int. Ed. 2020, 59, 10421-10425) and Trincado et al. (Coordination Chemistry Reviews 2021, 443, 213967) describe the preparation of glyceraldehyde (GAL), then lactic acid (LA) from ethylene glycol (EGO) and methanol, using an Iridium-NHCs (N-Heterocyclic Carbenes) catalyst.

[0013] The invention therefore aims to provide new hydrogenated organic liquids having a high gravimetric density of hydrogen, in particular greater than 4.4% by mass.

[0014] Another aim of the invention is to propose less energy-intensive dehydrogenation processes, in particular LOHC mixtures whose dehydrogenation enthalpy is less than 50 kJ / molH2.

[0015] Yet another aim of the invention is to provide new hydrogenated organic liquids which can be dehydrogenated and then rehydrogenated by reactions which can be at least partially or even entirely catalyzed by more available metals, which makes it possible to reduce or even eliminate the use of catalysts based on noble metals (in particular from the platinum group), and therefore to generate savings.

[0016] Yet another object of the invention is to provide mixtures of hydrogenated LOHCs whose dehydrogenated counterparts have the capacity to hydrogenate catalytically and reversibly, as well as dehydrogenated LOHCs having the capacity to hydrogenate catalytically and reversibly into these mixtures of hydrogenated LOHCs.

[0017] Yet another aim of the invention is to propose a process for dehydrogenating these mixtures of hydrogenated organic liquids which is efficient, with high conversion, and selective (to avoid any degradation of the LOHC, for example to avoid over-oxidations) while using fewer or no noble metal-based catalysts.

[0018] Thus, according to a first aspect, the invention relates to a composition of organic hydrogen-carrying liquids (LOHC) consisting of or comprising ethylene glycol and at least one compound of the following formula (I):

[0019] Ri-OH (I), in which Ri is a straight or branched C1 to C8 alkyl group, Ri not being an ethyl group.

[0020] This composition can be used as such. It can also be used via a twin tank separately comprising the at least one compound of formula (I) and ethylene glycol, or two tanks respectively comprising the at least one compound of formula (I) and ethylene glycol.

[0021] The molar ratio Rm between the quantity of at least one compound of formula (I) and the quantity of ethylene glycol is from 0.2 to 20, in particular from 1.6 to 2.5, in particular from 1.8 to 2.2, for example 2.

[0022] According to a particular embodiment, the invention relates to a composition of organic hydrogen-carrying liquids (LOHC) consisting of or comprising ethylene glycol and a compound of the following formula (I):

[0023] Ri-OH (I), in which Ri is a straight or branched C1 to C8 alkyl group, Ri not being an ethyl group.

[0024] According to a particular embodiment, the at least one compound of formula (I) is chosen from methanol, propanol, in particular n-propanol, butanol, in particular n-butanol, and pentanol, in particular n-pentanol, the at least one compound of formula (I) being in particular methanol or propanol, in particular n-propanol, more particularly methanol. According to a particular embodiment, the invention relates to a composition as defined above, consisting of or comprising ethylene glycol, at least one compound of formula (I) as defined above, and at least one compound of the following formula (II):

[0025] R2-OH (II), wherein R2 is a linear or branched C1-C5 alkyl group, the compound of formula (II) being distinct from the compound of formula (I).

[0026] According to a particular embodiment, the invention relates to a composition as defined above, consisting of or comprising ethylene glycol, a compound of formula (I) as defined above, and a compound of the following formula (II):

[0027] R2-OH (II), wherein R2 is a linear or branched C1-C5 alkyl group, the compound of formula (II) being distinct from the compound of formula (I).

[0028] According to a particular embodiment, the compound of formula (I) and the compound of formula (II) are respectively: methanol and ethanol; methanol and propanol, in particular n-propanol; methanol and butanol, in particular n-butanol; propanol, in particular n-propanol, and ethanol; or methanol and pentanol, in particular n-pentanol.

[0029] According to a particular embodiment, the invention relates to a composition as defined above, further comprising propan-1,3-diol and / or butan-1,4-diol.

[0030] According to a particular embodiment, the invention relates to a composition as defined above, consisting of ethylene glycol, a compound of formula (I) as defined above, optionally a compound of formula (II) as defined above, and optionally propan-1,3-diol and / or butan-1,4-diol.

[0031] According to another aspect, the invention also relates to the use of a composition as defined above as an organic hydrogen-carrying liquid (LOHC).

[0032] All of the embodiments mentioned above with respect to the compositions may also be applied here, alone or in combination.

[0033] According to another aspect, the invention also relates to a pair (i) of a composition of organic liquids carrying hydrogen (LOHC), and (ii) of the corresponding dehydrogenated LOHC(s), the composition of organic liquids carrying hydrogen (LOHC) being constituted by or comprising ethylene glycol and at least one compound of the following formula (I):

[0034] Ri-OH (I), in which Ri is a straight or branched C1 to C8 alkyl group, Ri not being an ethyl group.

[0035] All of the embodiments mentioned above with respect to the compositions may also be applied here, alone or in combination.

[0036] The hydrogenated compositions of the invention are capable of being dehydrogenated to produce, in addition to the corresponding dehydrogenated LOHC(s), hydrogen. Said corresponding dehydrogenated LOHC(s) are in return capable of regenerating by catalytic hydrogenation the compositions according to the invention.

[0037] According to another aspect, the invention also relates to a pair (i) of a composition of organic liquids carrying hydrogen (LOHC), and (ii) of the corresponding dehydrogenated LOHC(s), the composition of organic liquids carrying hydrogen (LOHC) being constituted by or comprising ethylene glycol and at least one compound of the following formula (I):

[0038] Ri-OH (I), in which Ri is a linear or branched C1-C8 alkyl group, one of the corresponding dehydrogenated LOHCs or the corresponding dehydrogenated LOHC being of the following formula (III):

[0039] Ri-OC(=O)-C(=O)-O-Ri (III), in which Ri is as defined above.

[0040] All of the embodiments mentioned above with respect to the compositions may also be applied here, alone or in combination.

[0041] According to a particular embodiment, the invention relates to a couple as defined above, in which one of the corresponding dehydrogenated LOHCs or the corresponding dehydrogenated LOHC is of the following formula (III):

[0042] Ri-OC(=O)-C(=O)-O-Ri (III), in which Ri is as defined previously.

[0043] According to a particular embodiment, the invention relates to a pair as defined previously, which is chosen from the following pairs:

[0044] (i) ethylene glycol and a compound of formula (I): Ri-OH; (ii) Ri-OC(=O)-C(=O)-O- Ri;

[0045] (i) ethylene glycol, a compound of formula (I): Ri-OH, and a compound of formula

[0046] (II): R2-OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-C(=O)-O-R2 and / or R2-O- C(=O)-C(=O)-O-R2;

[0047] (i) ethylene glycol, propan- 1,3 -diol, and a compound of formula (I): Ri-OH; (ii) Ri-O- C(=O)-C(=O)-O-Ri and / or RI-OC(=O)-CH2-C(=O)-O-RI; (i) ethylene glycol, butan-1,4-diol, and a compound of formula (I): Ri-OH; (ii) Ri-O- C(=O)-C(=O)-O-Ri and / or RI-OC(=O)-CH2-CH2-C(=O)-O-RI;

[0048] (i) ethylene glycol, propan- 1,3 -diol, butan-1,4-diol, and a compound of formula (I): Ri- OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-CH2-C(=O)-O-RI, and / or Ri-O- C(=O)-CH2-CH2-C(=O)-O-RI;

[0049] (i) ethylene glycol, propan- 1,3 -diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-0H; (ii) Ri-OC(=O)-C(=O)-O-Ri and / or Ri-OC(=O)- CH2-C(=O)-O-RI, R2-OC(=O)-C(=O)-O-R2,R2-OC(=O)-CH2-C(=O)-O-R2, Ri-O- C(=O)-C(=O)-O-R2and / or RI-OC(=O)-CH2-C(=O)-O-R2;

[0050] (i) ethylene glycol, butan-1,4-diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-CH2-CH2- C(=O)-O-Ri, R2-OC(=O)-C(=O)-O-R2, R2-OC(=O)-CH2-CH2-C(=O)-O-R2, Ri-O- C(=O)-C(=O)-O-R2, and / or RI-OC(=O)-CH2-CH2-C(=O)-O-R2; or

[0051] (i) ethylene glycol, propan-1,3-diol, butan-1,4-diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, Ri-O- C(=O)-CH2-C(=O)-O-R1, R1-OC(=O)-CH2-CH2-C(=O)-O-R1, R2-OC(=O)-C(=O)- O-R2, R2-OC(=O)-CH2-C(=O)-O-R2, R2-OC(=O)-CH2-CH2-C(=O)-O-R2, Ri-O- C(=O)-C(=O)-O-R2, R1-OC(=O)-CH2-C(=O)-O-R2, and / or Ri-OC(=O)-CH2-CH2- C(=O)-O-R2,

[0052] RI being as defined above,

[0053] R2 being a linear or branched C1 to C2 alkyl group, the compound of formula (II) being distinct from the compound of formula (I).

[0054] According to a particular embodiment, the invention relates to a pair as defined previously, which is chosen from the following pairs:

[0055] (i) ethylene glycol and methanol; (ii) dimethyl oxalate;

[0056] (i) ethylene glycol and ethanol; (ii) diethyl oxalate;

[0057] (i) ethylene glycol and propanol; (ii) dipropyl oxalate;

[0058] (i) ethylene glycol, methanol and ethanol; (ii) dimethyl oxalate, diethyl oxalate, and / or methyl ethyl oxalate;

[0059] (i) ethylene glycol, methanol and propanol; (ii) dimethyl oxalate, dipropyl oxalate, and / or methyl propyl oxalate;

[0060] (i) ethylene glycol, methanol and butanol; (ii) dimethyl oxalate, dibutyl oxalate, and / or methyl butyl oxalate; (i) ethylene glycol, ethanol and propanol; (ii) diethyl oxalate, dipropyl oxalate, and / or ethyl propyl oxalate; or

[0061] (i) ethylene glycol, methanol and pentanol; (ii) dimethyl oxalate, dipentyl oxalate, and / or methyl pentyl oxalate.

[0062] According to another aspect, the invention also relates to a method for generating hydrogen comprising at least one step of catalytic dehydrogenation of a composition of organic liquids carrying hydrogen (LOHC) as defined previously.

[0063] All the embodiments mentioned above as to compositions or couples can also be applied here, alone or in combination.

[0064] According to a particular embodiment, the invention relates to a method for generating hydrogen comprising at least one step of catalytic dehydrogenation of a composition of hydrogen-carrying organic liquids (LOHC) as defined previously, further generating the dehydrogenated LOHC(s) as defined previously.

[0065] According to a particular embodiment, the at least one dehydrogenation step is carried out in the presence of one or more catalysts based on copper, gold, silver and / or nickel.

[0066] Said catalyst(s) are in particular those supported on oxides or promoted by these same metals or oxides, in particular metallic oxides, in particular Ce, Al, Zn, Mg, Zr, Zn, V, Cr, Sn, Ti, Si, and their mixtures, more particularly ternary or quaternary oxides; on ores such as hydrolactite or T hydroxyapatite; on sulfur compounds; on boron nitride, in particular hexagonal (hBN); or on a carbon support, for example graphene (reduced or not) or activated carbon (C). Homogeneous pincer catalysts based on Ru, Rh, Ir, Fe, Mn can also be grafted onto metal oxides and serve as catalysts for the reaction.

[0067] According to a particular embodiment, said catalyst(s) are on SiCh, AI2O3, MgO, ZrO2, ZnO, CeO2, TiCL, C, hBN or their mixtures.

[0068] According to a more particular embodiment, said at least one dehydrogenation step is carried out in the presence of one or more catalysts chosen from catalysts based on copper, gold, silver and / or nickel, in particular copper or gold, for example Au-Pb / ALCf, Au / ZnO, Au / AhCL, CuZnOAhCL catalysts.

[0069] According to a particular embodiment, the at least one dehydrogenation step is carried out in a reactor, in particular in a reactor comprising the fixed-bed catalyst and / or in a batch, semi-batch or continuous type reactor. In general, the composition according to the invention is preheated to the reaction temperature, and in particular injected into a reactor. The different compounds of the composition may in this case be preheated together or separately.

[0070] At the reactor outlet, the liquids produced are generally separated from the hydrogen by gas / liquid separation.

[0071] According to a particular embodiment, the at least one dehydrogenation step is carried out at a temperature of 150 to 250°C, and / or at a pressure of 1 to 50 bar.

[0072] According to a particular embodiment, the present invention relates to a method as defined previously, comprising:

[0073] (a) A first dehydrogenation step, in the presence or absence of a catalyst based on silver, copper, gold and / or nickel, or under acid catalysis, in particular at a temperature of 50 to 300°C, and / or at a pressure of 1 to 50 bar;

[0074] (b) A second dehydrogenation step, in the presence of a catalyst based on copper, gold, silver and / or nickel, in particular at a temperature of 150 to 250°C, and / or at a pressure of 1 to 50 bar.

[0075] According to another aspect, the invention also relates to a process for regenerating a composition of organic liquids carrying hydrogen (LOHC) as defined above from one or more corresponding dehydrogenated LOHC(s) as defined above, the process comprising a step of catalytic hydrogenation of said compound of formula (II).

[0076] All the embodiments mentioned above as to compositions or couples can also be applied here, alone or in combination.

[0077] When more than one corresponding dehydrogenated LOHC is formed, the dehydrogenated LOHCs may be obtained as a mixture, and also used as a mixture for the formation of the corresponding hydrogenated LOHCs. Alternatively, these dehydrogenated LOHCs may be separated, for example by distillation, before their use to form the corresponding hydrogenated LOHCs.

[0078] Similarly, the mixture of hydrogenated LOHCs obtained can be used directly to form the corresponding dehydrogenated LOHC(s) again. The hydrogenated LOHCs can also be separated, for example by distillation, before their use to form the corresponding dehydrogenated LOHC(s) again.

[0079] According to a particular embodiment, the catalytic hydrogenation step is carried out in the presence of a catalyst based on copper, zinc, iron, gold, and / or nickel. Said catalyst(s) are in particular those supported on oxides or promoted by these same metals or oxides, in particular metallic oxides, in particular Ce, Al, Zn, Mg, Zr, Zn, V, Cr, Sn, Ti, Si, and their mixtures, more particularly ternary or quaternary oxides; on ores such as hydrolactite or hydroxyapatite; on sulfur compounds; on boron nitride, in particular hexagonal boron nitride (hBN); or on a carbon support, for example graphene (reduced or not) or activated carbon (C). Homogeneous pincer catalysts based on Ru, Rh, Ir, Fe, Mn can also be grafted onto metal oxides and serve as catalysts for the reaction.

[0080] According to a particular embodiment, said catalyst(s) are on SiCh, AI2O3, MgO, ZrO2, ZnO, CeO2, TiCh, C, hBN or their mixtures.

[0081] According to a more particular embodiment, said at least one dehydrogenation step is carried out in the presence of one or more catalysts chosen from catalysts based on copper, zinc, nickel, iron and / or gold, for example the catalysts Cu / SiCh, Cu / SBA-15, CuAu / SBA-15, CU / AI2O3, Cu / ZrO2, CuNi / SiO2, CuZnOAl2O3, Cu-Cu2O-Zn / SiO2, Cu-Cu2O- ZnO / SiO2, Cu-Cu2O-Fe2O3 / SiO2, CU-CU2O / AI2O3, CuZnO / SiO2

[0082] The processes can be operated in batch or semi-batch reactors or even continuously in “slurry”, “trickle bed”, fluidized bed or fixed bed type reactors.

[0083] Generally, the hydrogenation reaction is carried out at a temperature of 100 to 250°C, for example 180 to 220°C.

[0084] The pressure can vary from 10 to 50 bar.

[0085] Of course, the pressure / temperature couple can be adjusted according to the nature of the dehydrogenated LOHC / hydrogenated LOHC couple. The choice of catalyst is generally made taking into account the nature of the dehydrogenated LOHC / hydrogenated LOHC couple considered.

[0086] This step can also be carried out electrochemically, by techniques well known to those skilled in the art, in particular by electrocatalytic hydrogenation in an alcoholic-alkaline medium using ferromagnetic catalysts which can be prepared by leaching Ni-Al and Co-Al alloys, as for example described by Tusupbekova et al. (Pharmaceutical Chemistry Journal volume 19, pages 134-136 (1985)).

[0087] According to another aspect, the invention relates to a method for transporting and / or storing hydrogen, characterized in that it uses a composition of organic hydrogen-carrying liquids (LOHC) as defined above.

[0088] All the embodiments mentioned above with regard to the compositions or couples can also be applied here, alone or in combination. The compositions of organic liquids carrying hydrogen according to the invention can be used in particular in electrochemical or combustion energy conversion devices or in hydrogenation processes as a renewable source of hydrogen or even as fuel.

[0089] According to another of its aspects, the present invention relates to the use, in particular in electrochemical or combustion energy conversion devices, of at least one composition of organic liquids carrying hydrogen.

[0090] All the embodiments mentioned above as to compositions or couples can also be applied here, alone or in combination.

[0091] All of the compounds considered according to the invention are known organic liquids already used as solvents in fine chemistry. Thus, the infrastructure for transporting and / or storing them (ships, containers, tanks, pipelines, etc.) already exists.

[0092] Furthermore, these are stable compounds under normal temperature and pressure conditions, which makes it possible to consider their transport in standard containers or tanks which can be loaded onto ships, trains or trucks depending on the context.

[0093] The direct applications of a composition of hydrogen-carrying organic liquids according to the invention are the transport and storage of hydrogen.

[0094] The composition of organic liquids carrying hydrogen can be transported and stored to the place of use of the hydrogen, then transformed by dehydrogenation into one or more corresponding dehydrogenated LOHC(s) and into hydrogen.

[0095] The hydrogen produced can then be used as a reagent in an industrial process (hydrodesulfurization, hydrogenation of different compounds, recovery of CO2 into gaseous or liquid fuels, etc.).

[0096] The hydrogen produced can also be used as a decarbonized energy vector either by combustion or by powering an electrochemical energy conversion device.

[0097] Moreover, the liquid properties of these organic compounds make them good candidates for use as fuels for heat engines or electrochemical energy conversion devices.

[0098] They are compatible with packaging in the tank of a vehicle where dehydrogenation can be carried out in order to produce hydrogen to power the vehicle. Once dehydrogenated, the LOHC can be stored for later discharge in exchange for hydrogenated LOHC in accordance with the invention. Ethylene glycol and the compounds of formula (I) and (II) have the particular advantage of being biosourced, i.e. they can be derived from renewable resources in order to lower the CO2 balance of this H2 storage / transport solution.

[0099] Alcohols of the invention can also be obtained, for example, by fermentation of lignocellulose (Schubert, T., Biofuels, Bioprod. Bioref. 2020, 14, 845-878).

[0100] Ethylene glycol can be produced from bioethanol or by hydrogenolysis, particularly in one step, of sugar from plants.

[0101] Definitions

[0102] As used herein, the value ranges of "xy" or "from x to y" or "between x and y" include the bounds x and y as well as the integers between these bounds. For example, "1-5", or "from 1 to 5" or "between 1 and 5" denote the integers 1, 2, 3, 4 and 5. Preferred embodiments include each individual integer in the value range, as well as any subcombination of these integers. For example, preferred values ​​for "1-5" may include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, etc.

[0103] As used herein, the term "alkyl" means a straight or branched chain, especially straight, alkyl group having the number of carbon atoms indicated before said term, especially 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, etc. Thus, an expression such as "C1-C4 alkyl" means an alkyl radical containing from 1 to 4 carbon atoms. The same is true for the term "alkane".

[0104] EXAMPLES

[0105] Example 1: Generation of dihydrogen using a composition according to the invention An ethylene glycol / methanol mixture was dehydrogenated in one step according to the following reaction:

[0106] EG Methanol Dimethyl oxalate

[0107] DIVIO The ethylene glycol / methanol mixture is preheated to the reaction temperature and injected into a reactor filled with catalyst. This reaction is in fact globally endothermic (ArH°gas = 21 kJ / mobn) and therefore requires a heat input in order to maintain the operating conditions necessary for the reaction. This heat input can be achieved either by electrical heating of the reactor (heating element, oven, etc.), or by the circulation of a thermal fluid which exchanges its heat with the reactor (oil, steam, etc.). The reaction can also be carried out in a cascade of adiabatic reactors in which the heating of the reaction medium only takes place between the different reactors. Operating conditions are explained in the table below:

[0108] At the reactor outlet, the liquids produced are separated from the hydrogen by gas / liquid separation.

[0109] The reaction can thus be carried out in a single reactor. The reaction can also be carried out in two stages, according to the following scheme:

[0110] EG Methanol methyl glycolate

[0111] MG methyl glycolate Methanol Dimethyl oxalate

[0112] MG DMO

[0113] T= 150-250°C

[0114] P = 1-50 bars

[0115] Cata = Cu

[0116] Example 2: Generation of dihydrogen using other compositions according to the invention

[0117] The dehydrogenation reaction can also be carried out by replacing methanol with one or more other alcohols from the following choices: ethanol, propanol (n-propanol or iso-propanol), butanol (n-butanol, iso-butanol or tert-butanol) or pentanol (n-pentanol, isopentanol or tert-pentanol).

[0118] The reaction can then be represented by the following diagram:

[0119] ° EG Alcohols

[0120] Dialkyl oxalate:

[0121] DAO The mass density obtained for each mixture is recorded in the table below:

[0122] Example 3: Generation of dihydrogen using compositions according to the invention further comprising another diol The composition according to the invention may further contain 1,3-propanediol, and / or 1,4-butanediol.

[0123] The dehydrogenation / hydrogenation reactions are then as follows:

[0124] Example 4: Storage of hydrogen according to the invention

[0125] Hydrogen is stored by hydrogenation of the hydrogen-poor carrier, e.g., dimethyloxalate).

[0126] Dimethyl oxalate P = 10-50 bars EG Methanol

[0127] BMD Cata = Cu

[0128] The hydrogen-poor carrier is preheated to the reaction temperature, mixed with hydrogen and injected into a reactor filled with catalyst (e.g. a fixed-bed reactor). The operating conditions of the reactor and the nature of the catalyst differ according to the examples and are explained in the table below. At the reactor outlet, the liquids produced are separated from the unreacted hydrogen by gas / liquid separation.

[0129]

[0130] This hydrogenation is exothermic (ArH° gaz = -21 kJ / mol) and is therefore favored by the use of isothermal reactors, limiting temperature inhomogeneities. However, the reaction can also be imagined in a cascade of adiabatic reactors. Furthermore, the energy released by the reaction in the form of heat can be used to preheat the reactants or provide heat to another unit of the process (H2 production, purification, etc.).

Claims

CLAIMS 1. Pair (i) of a composition of organic hydrogen-carrying liquids (LOHC), and (ii) of the corresponding dehydrogenated LOHC(s), the composition of organic hydrogen-carrying liquids (LOHC) consisting of or comprising ethylene glycol and at least one compound of the following formula (I): Ri-OH (I), in which Ri is a linear or branched C1-C8 alkyl group, one of the corresponding dehydrogenated LOHCs or the corresponding dehydrogenated LOHC being of the following formula (III): Ri-OC(=O)-C(=O)-O-Ri (III), in which Ri is as defined above.

2. Couple according to claim 1, in which the at least one compound of formula (I) is chosen from methanol, propanol, in particular n-propanol, butanol, in particular n-butanol, and pentanol, in particular n-pentanol, the at least one compound of formula (I) being in particular methanol or propanol, in particular n-propanol, more particularly methanol.

3. Couple according to any one of the preceding claims, in which composition (i) consists of or comprises ethylene glycol, at least one compound of formula (I) as defined in claim 1, and at least one compound of the following formula (II): R2-OH (II), wherein R2 is a linear or branched C1-C5 alkyl group, the compound of formula (II) being distinct from the compound of formula (I), the compound of formula (I) and the compound of formula (II) being, for example, respectively: methanol and ethanol; methanol and propanol, in particular n-propanol; methanol and butanol, in particular n-butanol; propanol, in particular n-propanol, and ethanol; or methanol and pentanol, in particular n-pentanol.

4. A couple according to any one of the preceding claims, wherein composition (i) further comprises propan-1,3-diol and / or butan-1,4-diol.

5. Couple according to any one of the preceding claims chosen from the following couples: (i) ethylene glycol and a compound of formula (I): Ri-OH; (ii) Ri-OC(=O)-C(=O)-O- Ri; (i) ethylene glycol, a compound of formula (I): Ri-OH, and a compound of formula (I): R2-OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-C(=O)-O-R2 and / or R2-OC(=O)- C(=O)-O-R2; (i) ethylene glycol, propan- 1,3 -diol, and a compound of formula (I): Ri-OH; (ii) Ri-O- C(=O)-C(=O)-O-Ri and / or RI-OC(=O)-CH2-C(=O)-O-RI; (i) ethylene glycol, butan-1,4-diol, and a compound of formula (I): Ri-OH; (ii) Ri-O- C(=O)-C(=O)-O-Ri and / or RI-OC(=O)-CH2-CH2-C(=O)-O-RI; (i) ethylene glycol, propan- 1,3 -diol, butan-1,4-diol, and a compound of formula (I): Ri- OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-CH2-C(=O)-O-RI, and / or Ri-O- C(=O)-CH2-CH2-C(=O)-O-RI; (i) ethylene glycol, propan- 1,3 -diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-0H; (ii) Ri-OC(=O)-C(=O)-O-Ri and / or Ri-OC(=O)- CH2-C(=O)-O-RI, R2-OC(=O)-C(=O)-O-R2,R2-OC(=O)-CH2-C(=O)-O-R2, Ri-O- C(=O)-C(=O)-O-R2and / or RI-OC(=O)-CH2-C(=O)-O-R2; (i) ethylene glycol, butan-1,4-diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-OH; (ii) Ri-OC(=O)-C(=O)-O-Ri, RI-OC(=O)-CH2-CH2-C(=O)-O-Ri, R2-OC(=O)-C(=O)-O-R2, R2-OC(=O)-CH2-CH2-C(=O)-O-R2, Ri-O-C(=O)-C(=O)-O-R2, and / or RI-OC(=O)-CH2-CH2-C(=O)-O-R2; or (i) ethylene glycol, propan-1,3-diol, butan-1,4-diol, a compound of formula (I): Ri-OH, and a compound of formula (II): R2-0H; (ii) Ri-OC(=O)-C(=O)-O-Ri, Ri-O- C(=O)-CH2-C(=O)-O-R1, R1-OC(=O)-CH2-CH2-C(=O)-O-R1, R2-OC(=O)-C(=O)- O-R2, R2-OC(=O)-CH2-C(=O)-O-R2, R2-OC(=O)-CH2-CH2-C(=O)-O-R2, R1-O- C(=O)-C(=O)-O-R2, R1-OC(=O)-CH2-C(=O)-O-R2, and / or RI-OC(=O)-CH2-CH2- C(=O)-O-R2, Ri is as defined above, R2 being a linear or branched C1 to C5 alkyl group, the compound of formula (II) being distinct from the compound of formula (I), the pair being chosen in particular from the following pairs: (i) ethylene glycol and methanol; (ii) dimethyl oxalate; (i) ethylene glycol and ethanol; (ii) diethyl oxalate; (i) ethylene glycol and propanol; (ii) dipropyl oxalate; (i) ethylene glycol, methanol and ethanol; (ii) dimethyl oxalate, diethyl oxalate, and / or methyl ethyl oxalate; (i) ethylene glycol, methanol and propanol; (ii) dimethyl oxalate, dipropyl oxalate, and / or methyl propyl oxalate; (i) ethylene glycol, methanol and butanol; (ii) dimethyl oxalate, dibutyl oxalate, and / or methyl butyl oxalate; (i) ethylene glycol, ethanol and propanol; (ii) diethyl oxalate, dipropyl oxalate, and / or ethyl propyl oxalate; or (i) ethylene glycol, methanol and pentanol; (ii) dimethyl oxalate, dipentyl oxalate, and / or methyl pentyl oxalate.

6. A method for generating hydrogen comprising at least one step of catalytic dehydrogenation of a composition of organic liquids carrying hydrogen (LOHC) according to claim 1.

7. Method according to claim 6, in which the at least one dehydrogenation step is carried out in the presence of one or more catalysts based on copper, gold, silver and / or nickel.

8. Process according to any one of claims 6 to 7, in which the at least one dehydrogenation step is carried out at a temperature of 150 to 250°C, and / or at a pressure of 1 to 50 bar.

9. Method according to any one of claims 6 to 8, comprising: (c) A first dehydrogenation step, in the presence or absence of a catalyst based on silver, copper, nickel and / or gold or under acid catalysis, in particular at a temperature of 50 to 300°C, and / or at a pressure of 1 to 50 bar; (d) A second dehydrogenation step, in the presence of a catalyst based on copper, silver, gold and / or nickel, in particular at a temperature of from 150 to 250°C, and / or at a pressure of 1 to 50 bar.

10. Process for regenerating a composition of organic hydrogen-carrying liquids (LOHC) according to claim 1 from one or more corresponding dehydrogenated LOHC(s) according to claim 1, the process comprising a step of catalytic hydrogenation of said compound of formula (II), which is carried out in particular in the presence of a catalyst based on copper, zinc, iron, gold, and / or nickel.

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