METHOD FOR MONITORING THE STATE OF CONVERSION OF AN ORGANIC LIQUID CONTAINING HYDROGEN

Abstract

The present invention relates to a method for monitoring the conversion state of an organic liquid containing hydrogen. (no figure)

Description

Title of the invention: METHOD FOR MONITORING THE CONVERSION STATE OF A HYDROGEN-BEARING ORGANIC LIQUID

[0001] The present invention relates to a method for monitoring the conversion state of a hydrogen-bearing organic liquid.

[0002] 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 sources. These must be inexpensive, safe, non-polluting and easy to implement.

[0003] For these reasons, stable organic fluids have been developed in particular, capable of storing and releasing an energy fluid, for example a fuel, safely and efficiently by means of a catalytic reaction.

[0004] Containing the highest energy density per unit mass and producing only water upon combustion or oxidation in a hydrogen-oxygen fuel cell, hydrogen is considered one of the most efficient and environmentally friendly candidates as a future fuel. Hydrogen is a very energetic compound compared to conventional fossil fuels and burns in air at a wide range of concentrations (including 5% to 75%).

[0005] The concept of using hydrogen as an important energy carrier was suggested as early as the 1970s. However, the transportation and storage of hydrogen are key points to access the attractive "hydrogen era". Thus, a major challenge is to find suitable hydrogen carriers. For decades, scientists have been searching for suitable materials for hydrogen storage.

[0006] 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, liquid organic hydrogen carriers (LOHCs), which can be dehydrogenated and hydrogenated involving large amounts of hydrogen and could be used for land transportation applications, are of particular interest.

[0007] 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 in ambient conditions and therefore transportable and storable. The hydrogen-rich organic liquid is then dehydrogenated in a second reaction 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 / perhydro-dibenzyltoluene 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 quickly consider 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 kJ / molH2).Regarding the heteroaromatic compounds of the carbazole family, the most common compounds are N-ethylcarbazole (NEC) and furan, pyrrole and indole derivatives. In this case, the hydrogenation reaction leads to cyclic amines or cyclic ethers..

[0008] In addition, polyols have been used as LOHCs, releasing hydrogen by forming ketonic derivatives or lactones.

[0009] However, it remains extremely difficult to rapidly, or even in real time, monitor the cycling of LOHCs, especially to study whether the initial products are indeed converted into the desired final product(s).

[0010] Moreover, monitoring LOHCs over time to study their possible degradation, especially after cycling, is not easy.

[0011] Thus, an object of the invention is to provide a rapid and easy evaluation method, for example using an embedded or portable device, and / or in real time, of the conversion state of an LOHC of a hydrogenated LOHC / dehydrogenated LOHC pair.

[0012] Thus, according to a first aspect, the invention relates to a method for monitoring the conversion state of a hydrogen-carrying organic liquid (LOHC), comprising the following steps: i. At least one fluorescence measurement of a hydrogen-carrying organic liquid to obtain at least one quantitative data DE relating to at least one fluorescence parameter F of the studied hydrogen-carrying organic liquid; and ii. Comparing said fluorescence-related data DE for at least one fluorescence parameter F with the data DH and / or Dd corresponding respectively to the data related to at least one fluorescence parameter F of the fully hydrogenated hydrogen-carrying organic liquid and of the fully dehydrogenated hydrogen-carrying organic liquid.

[0013] According to one embodiment, said at least one fluorescence measurement of step (i) is carried out at the surface of said liquid.

[0014] According to a particular embodiment, said at least one fluorescence measurement of step (i) is carried out on the undiluted hydrogen-carrying organic liquid.

[0015] According to a particular embodiment, said at least one fluorescence measurement of step (i) is carried out with a light collection angle ranging from 40 to 50°, particularly about 45°.

[0016] According to a particular embodiment, said at least one fluorescence measurement of step (i) is carried out so that the excitation beam does not pass through said liquid throughout the entire height of the sample.

[0017] The fluorescence measurement is for example carried out using a Horiba Jobin Yvon spectrometer with a 450W Xenon lamp on an organic liquid carrying hydrogen, in a quartz cuvette, in particular an organic liquid carrying hydrogen ready for the conversion of hydrogen.

[0018] The measurements can in particular be carried out on undiluted samples, under conditions in which the excitation beam does not pass through the entire liquid. These may in particular be measurements carried out in a mode referred to as “Front Face”, by measuring the fluorescence on the surface of the liquid, with a light collection angle of 45°.

[0019] According to one embodiment, said at least one quantitative data DE relating to the fluorescence parameter F is obtained by measuring the excitation spectrum and / or the emission spectrum of said hydrogen-carrying organic liquid.

[0020] According to one embodiment, said fluorescence parameter F is the characterization of the maxima(s) of the excitation spectrum and / or of the emission spectrum, and said quantitative data DE is the wavelength of the maxima(s).

[0021] According to one embodiment, the fluorescence parameter F is the characterization of the maxima(s) of the excitation spectrum and / or the emission spectrum, and the quantitative data DE are the wavelength of the maxima(s) and the width at half-maximum. of the maximum or maximums.

[0022] According to one embodiment, the fluorescence parameter F is translated into a color, for example defined by its chromatic coordinates.

[0023] Said fluorescence parameter F can be translated into a color, for example defined by its chromatic coordinates, according to techniques well known to those skilled in the art, for example those described by DB Judd and G. Wyszecki (Color in Business, Science and Industry, Wiley, 1962), RWG Hunt (Measuring Color, Ellis Horwood, 1991), or LD Carlos, RAS Ferreira and V. de Zea Bermudez (Hybrid Materials, ed. G. Kickelbic, Wiley-VCH, Weinheim, 2007).

[0024] Color coordinates can be calculated using the system proposed by the International Commission on Illumination (CIE) in 1931. This method is based on the response of the human eye to visible light, where there are three types of cone cells responsible for color distinction.

[0025] Each cone cell has a different sensitivity, which can be designated by:

[0026] [Math.l] And

[0027] with maximum values ​​at approx. 419, 531 and 558 nm, respectively. The sum of the three cone sensitivity functions is called the photon response and shows a maximum sensitivity centered at 555 nm, in the green spectral region.

[0028] In addition, the CIE defined three new primary colors X, Y and Z, necessary to have a correspondence to all specific colors. These quantities X, Y and Z are called tristimulus values. The emission can be translated into these coordinates via the following equation:

[0029] [Math.2] f .. f - n K = J ÿiEjd Z ~ J

[0030] where E represents the intensity of the emission spectrum and i represents the emission wavelength.

[0031] To facilitate the perception of colors, the tristimuli are converted into a two-dimensional system: the tristimuli are transformed into chromaticity coordinates (x,y)

[0032]

[0033]

[0034]

[0035]

[0036]

[0037] which are plotted in a two-dimensional chromaticity diagram. The chromaticity coordinates are related to X, Y and Z by: [Math.3] x + y + z x X + Y + Z F According to one embodiment, the comparison of step (ii) is made by means of a calibration curve, established from the DH and / or Dd data. The calibration curve can be established using techniques well known to those skilled in the art. It can in particular be obtained by carrying out measurements, in particular with a laboratory spectrometer, on: - On samples, for example on 3 to 10 samples, having a different concentration of organic liquid carrying fully hydrogenated hydrogen; - On samples, for example on 3 to 10 samples, having a different concentration of organic liquid carrying totally dehydrogenated hydrogen; - On mixtures of organic liquid carrying fully hydrogenated hydrogen / organic liquid carrying fully dehydrogenated hydrogen having different ratios and with known concentrations. According to one embodiment, the organic liquid carrying totally hydrogenated hydrogen is dehydrogenated into organic liquid carrying totally dehydrogenated hydrogen or the organic liquid carrying totally dehydrogenated hydrogen is hydrogenated into organic liquid carrying totally hydrogenated hydrogen, via one or more intermediaries, said step (ii) additionally comprising the comparison of said data DE relating to at least one fluorescence parameter F with the data D, corresponding to these intermediaries. According to one embodiment, the totally hydrogenated organic hydrogen-carrying liquid dehydrogenates into totally dehydrogenated organic hydrogen-carrying liquid or the totally dehydrogenated organic hydrogen-carrying liquid hydrogenates into totally hydrogenated organic hydrogen-carrying liquid, also forming one or more secondary products, said step (ii) additionally comprising the comparison of said data DE relating to at least one fluorescence parameter F with the data D, corresponding to these secondary products. According to one embodiment, the hydrogen-carrying organic liquid relates to a hydrogenated hydrogen-carrying organic liquid / organic liquid pair dehydrogenated hydrogen carrier whose organic liquid carrying hydrogenated hydrogen is made up of or comprises a compound chosen from: - Compounds comprising at least one perhydrogenated aryl or perhydrogenated heteroaryl group, in particular a perhydrogenated aryl group, more particularly a perhydrogenated aryl group with 6 carbon atoms; - Compounds comprising at least one secondary or primary alcohol; - Compounds comprising at least one primary amine; - Compounds comprising at least one primary amine and at least one alcohol primary or secondary; - Compounds comprising at least two primary alcohols, or at least one primary alcohol and one secondary alcohol, or at least one primary alcohol and one aldehyde, or one lactone.

[0038] According to one embodiment, the hydrogen-carrying organic liquid comprises at least one group chosen from perhydrogenated aryl, perhydrogenated heteroaryl, aryl and heteroaryl groups.

[0039] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of totally hydrogenated hydrogen-carrying organic liquid / totally dehydrogenated hydrogen-carrying organic liquid in which the totally hydrogenated hydrogen-carrying organic liquid is of the following formula (I):

[0040] [Chem.l]

[0041] (I),

[0042] in which:

[0043] n is 0, 1, 2, 3, 4 or 5;

[0044] at least one of the carbons of

[0045] [Chem.2]

[0046] being optionally substituted by a Rh group independently selected from linear or branched C1 to C4 alkyls and Y groups;

[0047] X and Y are independently a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups.

[0048] According to one embodiment, the fully hydrogenated organic hydrogen-carrying liquid (LOHC) has the following formula (Ia):

[0049] [Chem.3] M ,oh K '-

[0050] (the),

[0051] in which:

[0052] n is 0, 1, 2, 3 or 4;

[0053] Ri is H, a linear or branched C1-C4 alkyl group, or a group Y.

[0054] X and Y are independently a perhydrogenated aryl group or a heteroaryl group perhydrogenated, said group being optionally substituted by at least one R2 group, independently chosen from linear or branched C1 to C4 alkyl groups, in particular methyl, linear or branched C1 to C4 O-alkyl groups, in particular O-methyl, -NRaRb groups, with Ra and Rb independently chosen from linear or branched C1 to C4 alkyl groups, in particular the -N(Me)2 group.

[0055] According to a particular embodiment, X is a perhydrogenated aryl group, X being in particular a cyclohexyl group.

[0056] According to another particular embodiment, X is a perhydrogenated heteroaryl group, X being chosen in particular from the piperidinyl, piperazinyl, hexahydropyrimidinyl, and hexahydropyridazinyl groups.

[0057] According to a particular embodiment, n is 0, 1 or 2.

[0058] According to a particular embodiment, Ri is H or methyl.

[0059] According to a particular embodiment: - Ri is H; or - Ri is a Y group; and / or - X is a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups; and / or - n is 1, 2, 3 or 4.

[0060] According to one embodiment, the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is chosen from cyclohexyl-methanol, 1-cyclohexylethanol, 4-methylcyclohexanemethanol, dicyclohexylcarbinol, and cyclohexanepropanol.

[0061] According to a particular embodiment, the organic liquid carrying fully hydrogenated hydrogen is not 1-cyclohexylethanol.

[0062] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of totally hydrogenated hydrogen-carrying organic liquid of the following formula (I) / totally dehydrogenated hydrogen-carrying organic liquid of the following formula (II):

[0063] [Chem.4] xRzOh

[0064] (I),

[0065] [Chem.5] X - jy

[0066] (II),

[0067] in which:

[0068] n is 0, 1, 2, 3, 4 or 5;

[0069] at least one of the carbons of

[0070] [Chem.6] Y ' nV

[0071] being optionally substituted by an Rh group independently chosen from linear or branched C1 to C4 alkyls and Y groups;

[0072] Ri is H, a linear or branched C1-C4 alkyl group, or a group Y,

[0073] X is the perhydrogenated counterpart of the aryl or heteroaryl group X', optionally substituted by at least one group R2, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0074] Y is the perhydrogenated counterpart of the aryl or heteroaryl group Y', optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0075] A is -CH2- and n' is n, or A is -CH=CH- and n' is 1 or 2,

[0076] at least one of the carbons of group A being optionally substituted by a group Rb independently chosen from linear or branched C1 to C4 alkyls and Y' groups;

[0077] X' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0078] Y' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups.

[0079] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of totally hydrogenated hydrogen-carrying organic liquid of the following formula (Ia) / totally dehydrogenated hydrogen-carrying organic liquid of the following formula (IIa):

[0080] [Chem.7] Cl .oh Ri

[0081] (the),

[0082] [Chem. 8] THE J,0 R'i

[0083] (lia),

[0084] in which:

[0085] n is 0, 1, 2, 3 or 4;

[0086] Ri is H, a linear or branched C1-C4 alkyl group, or a group Y,

[0087] X is the perhydrogenated counterpart of the aryl or heteroaryl group X', optionally substituted by at least one group R2, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0088] Y is the perhydrogenated counterpart of the aryl or heteroaryl group Y', optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0089] A is -CH2- and n' is n, or A is -CH=CH- and n' is 1 or 2,

[0090] R' i is Ri, when Ri is H or a linear or branched C1 to C4 alkyl group; or a group Y',

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] X' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups; Y' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups. Thus, a compound of formula (II) or (IIa) with n'=1 corresponds to a compound (I) or (Ia) with n=2, and a compound of formula (II) with n'=2 corresponds to a compound (I) or (Ia) with n=4. According to one embodiment, the organic liquid carrying hydrogen relates to a pair chosen from the following pairs: - 1-Cyclohexylethanol / Acetophenone; - Cyclohexylmethanol / Benzaldehyde; - 4-Methylcyclohexanemethanol / (4-Methylphenyl)methanol; - Dicyclohexylcarbinol / Benzophenone; - Cyclohexanepropanol / Cinnamaldehyde. According to a particular embodiment, the couple according to the invention is not the 1-Cyclohexylethanol / Acetophenone couple. According to one embodiment, the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is of the following formula (I'): [Chem.9] x ' n (D, in which: n is 0, 1, 2, 3 or 4; at least one of the carbons of [Chem. 10] being optionally substituted by an Rh group independently selected from C1 to C4 linear or branched alkyls and Y groups;

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114]

[0115] X and Y are independently a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from C1-C4 linear or branched alkyl groups, C1-C4 linear or branched O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from C1-C4 linear or branched alkyl groups. According to a particular embodiment, none of the carbons of [Chem. 11] is not substituted by an Rb group According to a particular embodiment, at least one of the carbons of [Chem. 12] yny is optionally substituted with an RB group independently selected from C1-C4 straight or branched alkyls and Y groups. According to a particular embodiment, X is a perhydrogenated aryl group, X being in particular a cyclohexyl group. According to another particular embodiment, X is a perhydrogenated heteroaryl group, X being chosen in particular from the piperidinyl, piperazinyl, hexahydropyrimidinyl, and hexahydropyridazinyl groups. According to a particular embodiment, n is 0, 1 or 2. According to a particular embodiment, the invention relates to an organic liquid carrying hydrogen in which: - X is a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups; and / or - n is 1, 2, 3 or 4. According to one embodiment, the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is chosen from cyclohexylmethanamine, 2-cyclohexylmethanamine, cyclohexanepropanamine, 4-methylcyclohexylmethanamine, l-(2-methylcyclohexyl)methanamine, l-(3-methylcyclohexyl)methanamine.

[0116] According to a particular embodiment, the organic liquid carrying fully hydrogenated hydrogen is chosen from the compounds of the following formula:

[0117] [Chem. 13] \s'

[0118] [Chem. 14]

[0119] [Chem. 15]

[0120] [Chem. 16]

[0121] [Chem. 17]

[0122] [Chem. 18]

[0123] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of totally hydrogenated hydrogen-carrying organic liquid of the following formula (!') / totally dehydrogenated hydrogen-carrying organic liquid of the following formula (II'):

[0124] [Chem. 19] 'n'

[0125] (!'),

[0126] [Chem.20]

[0127] (II'),

[0128] in which:

[0129] n is 0, 1, 2, 3 or 4;

[0130] X is the perhydrogenated counterpart of the aryl or heteroaryl group X', optionally substituted by at least one group R2, independently chosen from C1-C4 linear or branched alkyl groups, C1-C4 linear or branched O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from C1-C4 linear or branched alkyl groups;

[0131] A is -CH2- and n' is n, or A is -CH=CH- and n' is 1 or 2,

[0132] at least one of the carbons of group A being optionally substituted by a group Rb independently chosen from linear or branched C1 to C4 alkyls and groups Y',

[0133] X' and Y' are independently an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups.

[0134] Thus, a compound of formula (II') with n'=1 corresponds to a compound (I') with n=2, and a compound of formula (II') with n'=2 corresponds to a compound (I') with n=4.

[0135] An example of a compound of formula (I') / compound of formula (II') pair with A being -CH=CH- can be the 3-cyclohexylpropanamine / cinnamonitrile pair.

[0136] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of composition of totally hydrogenated hydrogen-carrying organic liquids / totally dehydrogenated hydrogen-carrying organic liquid(s) in which the composition of totally hydrogenated hydrogen-carrying organic liquids comprises: - at least one first compound of the following formula (I”):

[0137] [Chem.21] ,OH ' 'nf R,

[0138] (I”),

[0139] and - at least one second compound of formula (II”) or (III”) following:

[0140] [Chem.22] R:;„ ,OH

[0141] (II”),

[0142] [Chem.23] O

[0143] (III”),

[0144] in which:

[0145] n is 0, 1, 2, 3 or 4;

[0146] Ri is H, a linear or branched C1-C4 alkyl group, or a group Y;

[0147] X is H, a linear or branched C1-C4 alkyl group, a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said perhydrogenated aryl or heteroaryl group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups;

[0148] or n=0, and X forms with Ri a perhydrogenated aryl group, or a perhydrogenated heteroaryl group;

[0149] Y is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups;

[0150] R3 is: - a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; - a group -R-Cy where R is a linear or branched C1 to C6 alkane diyl and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or - a linear or branched C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group;

[0151] or when the at least first compound of formula (I”) comprises at least one perhydrogenated aryl or perhydrogenated heteroaryl group: - H, or a linear or branched C1 to C6 alkyl group.

[0152] According to a particular embodiment, Ri is H.

[0153] According to a particular embodiment, Ri is H, and X is H or an alkyl group linear or branched in C1 to C4, n being in particular equal to 0, the at least first compound of formula (I”) being in particular MeOH.

[0154] According to a particular embodiment, Ri is H, and X is H, a linear or branched C1-C4 alkyl group, a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said perhydrogenated aryl or heteroaryl group being optionally substituted by at least one R2 group, independently chosen from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently chosen from linear or branched C1-C4 alkyl groups.

[0155] According to a particular embodiment, Ri is a linear or branched C1 to C4 alkyl group, or a group Y, in particular a linear or branched C1 to C4 alkyl group.

[0156] According to a particular embodiment, n=0, and X forms with RI an aryl group perhydrogenated, or a perhydrogenated heteroaryl group.

[0157] According to a particular embodiment, R3 is H or a linear or branched C1 to C6 alkyl group, in particular H.

[0158] According to a particular embodiment, R3 is a linear or branched C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group, in particular a linear C2 to C6 alkyl group substituted by at least one -CH2 -OH group, the second compound preferably being chosen from 1,4-butanediol, 1,3-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,4-pentanediol, 1,3-pentanediol, 2,4-pentanediol, and even more preferably 1,4-butanediol.

[0159] According to a particular embodiment, R3 is: a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or a group -R-Cy where R is a linear or branched C1 to C6 alkane diyl and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group.

[0160] According to a particular embodiment, the composition of the invention comprises: at least one first compound of the following formula (I):

[0161] [Chem.24] A ' 'n| Ri

[0162] (I),

[0163] and - at least one second compound of formula (II”) or (III”) following:

[0164] [Chem.25] r:k ...oh

[0165] (II”),

[0166] [Chem.26]

[0167] (III”),

[0168] in which:

[0169] n=0, and X forms with Ri a perhydrogenated aryl group, or a heteroaryl group

[0170] perhydrogenated; R3 is: a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or a group -R-Cy where R is a linear or branched C1 to C6 alkane diyl and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group.

[0171] According to a particular embodiment, the organic liquid carrying hydrogen is relating to a pair composition of organic liquids carrying hydrogen totally hydrogenated / totally dehydrogenated hydrogen-carrying organic liquid(s) in which the composition of totally hydrogenated hydrogen-carrying organic liquids comprises: - at least one first compound of the following formula (I”):

[0172] [Chem.27] Ri

[0173] (I”),

[0174] and - at least one second compound of formula (II”) or (III”) following:

[0175] [Chem.28] ,Oh

[0176] (II”),

[0177] [Chem.29] Oh

[0178] (III”),

[0179] in which:

[0180] n=0, and X forms with Ri a perhydrogenated aryl group, or a heteroaryl group perhydrogenated;

[0181] R3 is H, or a linear or branched C1 to C6 alkyl group.

[0182] According to a particular embodiment, the hydrogen-carrying organic liquid relates to a pair of composition of totally hydrogenated hydrogen-carrying organic liquids / totally dehydrogenated hydrogen-carrying organic liquid(s) in which the composition of totally hydrogenated hydrogen-carrying organic liquids comprises: - at least one first compound of the following formula (I”):

[0183] [Chem.30] is OH X' < ■ Ri

[0184] (I”),

[0185] and - at least one second compound of formula (II”) or (III”) following:

[0186] [Chem.31] ■ X.-''

[0187] (II”),

[0188] [Chem.32] Ri XX Ri

[0189] (III”),

[0190] in which:

[0191] n is 0, 1, 2, 3 or 4;

[0192] Ri is H, or a linear or branched C1 to C4 alkyl group;

[0193] X is H, or a linear or branched C1 to C4 alkyl group;

[0194] Ri being in particular H, with in particular n=0 and X=H;

[0195] R3 is a linear or branched C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group, in particular a linear C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group, in particular one -CH2-OH group, the second compound preferably being chosen from 1,4-butanediol, 1,3-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,4-pentanediol, 1,3-pentanediol, 2,4-pentanediol, and even more preferably 1,4-butanediol.

[0196] According to a particular embodiment, the hydrogen-carrying organic liquid relates to a pair of composition of totally hydrogenated hydrogen-carrying organic liquids / totally dehydrogenated hydrogen-carrying organic liquid(s) in which the composition of totally hydrogenated hydrogen-carrying organic liquids comprises: - at least one first compound of the following formula (I”):

[0197] [Chem.33] 44 oh X' < Ri

[0198] (I”),

[0199] and - at least one second compound of formula (II”) or (III”) following:

[0200] [Chem.34]

[0201] (II”),

[0202] [Chem.35] 6

[0203] (III”),

[0204] in which:

[0205] n is 0, 1, 2, 3 or 4;

[0206] R! is H,

[0207] X is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said perhydrogenated aryl or heteroaryl group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups;

[0208] R3 is H, or a linear or branched C1 to C6 alkyl group.

[0209] According to a particular embodiment, the hydrogen-carrying organic liquid relates to a pair of composition of totally hydrogenated hydrogen-carrying organic liquids / totally dehydrogenated hydrogen-carrying organic liquid(s) in which the composition of totally hydrogenated hydrogen-carrying organic liquids comprises: - at least one first compound of the following formula (I”):

[0210] [Chem.36]

[0211] (I”),

[0212] and - at least one second compound of formula (II”) or (III”) following:

[0213] [Chem.37]

[0214] (II”),

[0215] [Chem.38] rm ,o. .R-. V K' Oh

[0216] (III”),

[0217] in which:

[0218] n is 0, 1, 2, 3 or 4;

[0219] Ri is H, or a linear or branched C1 to C4 alkyl group;

[0220] X is H, or a linear or branched C1 to C4 alkyl group;

[0221] Ri being in particular H, with in particular n=0 and X=H;

[0222] R3 is: - a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or - a group -R-Cy where R is a linear or branched diyl alkane in C1 to C6 and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group.

[0223] According to a particular embodiment: - X is a perhydrogenated aryl group, X being in particular a cy- group clohexyl; or - X is a perhydrogenated heteroaryl group, X being chosen in particular from the piperidinyl, piperazinyl, hexahydropyrimidinyl, and hexahydro-pyridazinyl groups.

[0224] According to a particular embodiment, n is 0, 1 or 2.

[0225] According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of composition of totally hydrogenated organic liquids carrying hydrogen / totally dehydrogenated organic liquid(s) carrying hydrogen in which the totally dehydrogenated organic liquid(s) carrying hydrogen are in particular of the following formula (IV”): • When Ri is different from H:

[0226] [Chem.39] x n'f |t R'1 Ô

[0227] (IVa”), • When Ri is H:

[0228] [Chem.40] Oh

[0229] (IVa”), and / or

[0230] [Chem.41] ïa) ,.os ...¾ "ô

[0231] (IVb”), • When R3 is substituted by a -CH2-OH group:

[0232] [Chem.42] O

[0233] (IVa”),

[0234] and / or

[0235] [Chem.43] 7a) ,.o.. Case x ” T 'l ? x R'i O Ô R'i

[0236] (IVc”)

[0237] and / or

[0238] [Chem.44] (Al „R3 -O. ,Rj XO. (Al X"' ]| V - ]ff n'X Ri Ô Ô Ô R3

[0239] (IVc'”), • When R3 represents H:

[0240] [Chem.45] x ' hH |î Ô

[0241] or, in the presence of an additional compound R4-OH, with R4 being a linear or branched C2 to C6 alkyl group,

[0242] [Chem.46] (Al ..() ...CL ir hT Y R', O

[0243] (IVd”);

[0244] and / or

[0245] [Chem.47] .h R', O

[0246] (IVa”), • When R3 represents H, and Ri is H:

[0247] [Chem.48]

[0248] (IVd”),

[0249] and / or

[0250] [Chem.49]

[0251] (IVa”),

[0252] and / or

[0253] [Chem.50]

[0254] (IVb”),

[0255] in which:

[0256] n is 0, 1, 2, 3 or 4;

[0257] Ri is H, a linear or branched C1-C4 alkyl group, or a group Y,

[0258] X is the perhydrogenated counterpart of the aryl or heteroaryl group X', optionally substituted by at least one group R2, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0259] Y is the perhydrogenated counterpart of the aryl or heteroaryl group Y', optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0260] A is -CH2- and n' is n, or A is -CH=CH- and n' is 1 or 2,

[0261] R' i is Ri, when Ri is H or a linear or branched C1 to C4 alkyl group; or a group Y',

[0262] X' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups;

[0263] Y' is an aryl or heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1 to C4 alkyl groups, linear or branched C1 to C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1 to C4 alkyl groups,

[0264] R3 is: - a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; - a group -R-Cy where R is a linear or branched C1 to C6 alkane diyl and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or - a linear or branched C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group;

[0265] or when the at least first compound of formula (I”) comprises at least one perhydrogenated aryl or perhydrogenated heteroaryl group: - H, or a linear or branched C1 to C6 alkyl group.

[0266] Thus, a compound of formula (IV”) with n'=1 corresponds to a compound (I) with n=2, and a compound of formula (IV”) with n'=2 corresponds to a compound (I') with n=4.

[0267] According to a particular embodiment, the couple according to the invention is chosen from

[0268]

[0269] the following couples: - cyclohexanol, cyclohexylmethanol / phenyl benzoate; - cyclohexanol, methanol / methyl-phenylformate and / or methyl-phenylcarbonate; - methanol, 1,4-butanediol / dimethylsuccinate; - methanol, 1,3-propanediol / methyldiesterpropanoate; - methanol, 1,5-pentanediol / methyldiesterpentanoate; - cyclohexylethanol, methanol / methyl-l-phenylethylformate and / or methyl- 1-phenylethylcarbonate. According to one embodiment, the hydrogen-carrying organic liquid relates to a pair of compositions of totally hydrogenated hydrogen-carrying organic liquids / totally dehydrogenated hydrogen-carrying organic liquid(s) in which said composition is chosen from the following compositions: - cyclohexanol + cyclohexylmethanol; - cyclohexanol + methanol; - methanol + 1,4-butanediol; - methanol + 1,3-butanediol; - methanol + 1,3-propanediol; - methanol + 1,5-pentanediol; - methanol + 1,4-pentanediol; - methanol + 1,3-pentanediol; - methanol + 2,4-pentanediol; - cyclohexylethanol + methanol. According to one embodiment, the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is chosen from the following compounds: - Methylcyclohexane; - Perhydrodibenzyltoluene; - Perhydrobenzyltoluene; - ethylamine; - propylamine; - isopropylamine; - butylamine; - penty lamin; - ethane-1,2-diamine; - propane-1,3-diamine; - butane- 1,4-diamine; - butane-1,3-diamine; - pentane-1,3-diamine; - pentane-1,5-diamine; - 2-(aminomethyl) propane-1,3-diamine; - (±)-l-Amino-2-propanol; - 3-Amino-l-propanol; - Monoethanolamine; - 1,4-butanediol / gamma-butyrolactone; - 1,4-pentanediol.

[0270] According to one embodiment, the method according to the invention is implemented in a portable, on-board, and / or autonomous device.

[0271] According to one embodiment, the method according to the invention is implemented in situ.

[0272] According to one embodiment, the method according to the invention is implemented before and / or after the transport of said hydrogen-carrying organic liquid.

[0273] According to one embodiment, the method according to the invention is implemented before and / or after: - the dehydrogenation of said organic liquid carrying hydrogen, which is in particular totally hydrogenated; - the hydrogenation of said organic liquid carrying hydrogen, which is in particular completely dehydrogenated; - one or more dehydrogenation / hydrogenation cycles relating to said hydrogen-carrying organic liquid.

[0274] According to one embodiment, the method according to the invention is implemented to monitor the degradation or wear of said hydrogen-carrying organic liquid. Definitions

[0275] As used herein, the value ranges in the form 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" designates 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.

[0276] 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, a term such as "C1-C4 alkyl" means an alkyl radical containing from 1 to 4 carbon atoms. The same is true for the term "alkane".

[0277] As used herein, the term "arene" means a mono- or bicyclic, substituted or unsubstituted, hydrocarbon aromatic ring system having 6 to 10 carbon atoms in the ring. Examples include benzene and naphthalene. Preferred arenes include unsubstituted or substituted benzene and naphthalene. Included within the definition of "arene" are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a cycloalkyl ring. Examples of such fused ring systems include, for example, indane, indene, and tetrahydronaphthalene.

[0278] As used herein, the term "heteroarene" means an aromatic ring system containing 5 to 10 carbon atoms in which one or more ring carbon atoms are replaced by at least one heteroatom such as -O-, -N- or -S-, particularly -N- and / or -O-. Examples of heteroarenes include pyrrole, furan, thiophene, pyrazole, imidazole, thiazole, isothiazole, isoxazole, oxazole, oxathiol, oxadiazole, triazole, oxatriazole, furazane, tetrazole, pyridine, pyrazine, py-rimidine, pyridazine, triazine, indole, isoindole, indazole, benzofuran, isobenzofuran, purine, quinazoline, quinoline, isoquinoline, benzoimidazole, benzothiazole, benzo-thiophene, thianaphthene, benzoxazole, benzisoxazole, cinnoline, phthalazine, naph-tyridine and quinoxaline. Included in the definition of "heteroarene" are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a heterocycloalkyl ring.Examples of such fused ring systems include, for example, phthalamide, phthalic anhydride, indoline, isoindoline, tetrahydroisoquinoline, chromane, isochromane, chromene, and isochromene. FIGURES

[0279] [Fig.l] corresponds to the excitation spectrum of different molecules relating to the 1-cyclohexylethanol / acetophenone couple as described in the examples, obtained with a laboratory spectrometer (Jobin Yvon Horiba).

[0280] [Fig.2] corresponds to the emission spectrum of different molecules relating to the 1-cyclohexylethanol / acetophenone couple as described in the examples, obtained with a laboratory spectrometer (Jobin Yvon Horiba). EXAMPLES

[0281] The hydrogenated LOHC / dehydrogenated LOHC 1-cyclohexylethanol / acetophenone couple was studied.

[0282] The balances relating to this couple are as follows:

[0283] [Chem.51] ;>v

[0284] Scheme 1: equilibria involved in a cycle relating to the 1-cyclohexylethanol / acetophenone couple for the formation of dihydrogen.

[0285] The emission and excitation spectra of 1-cyclohexylethanol and acetophenone were first measured to establish their respective fluorescence signals.

[0286] The fluorescence measurement was carried out using a Horiba Jobin Yvon spectrometer with a 450W Xenon lamp on these compounds in a quartz cuvette. The measurements were carried out on undiluted samples, under these conditions the excitation beam could not pass through the entire liquid and therefore the measurements were carried out in the mode designated "Front Face", measuring the fluorescence on the surface of the liquid as in the case of measurements carried out on solid samples with a light collection angle of 45°.

[0287] The same was done for the intermediates acetylcyclohexane, 1-(1-cyclohexen-1-yl)ethanone, and 1-phenylethanol.

[0288] The results obtained are presented in [Fig.l] and 2.

[0289] [Fig.2] shows that the emission of 1-cyclohexylethanol is centered around 450 nm and that the emission of acetophenone is centered rather around 500 nm.

[0290] The excitation spectrum of two molecules is also very different, for the same emission length, 1-cyclohexylethanol having a maximum around 400 nm and acetophenone being centered rather around 425 nm ([Fig.l]).

[0291] The emission and excitation of these two molecules are therefore different, sufficiently different to allow their identification and to be able to follow the hydrogenation cycle.

[0292] Then the hydrogenation and / or dehydrogenation reaction relating to the 1-cyclohexylethanol / acetophenone couple was successfully monitored. This monitoring was carried out by measuring the excitation and / or emission spectra of the composition studied at different times of the reaction to establish the overall response of the products and intermediate products or "by-products" of the hydrogenation or dehydrogenation.

[0293] Quantitative monitoring could also be carried out by first establishing calibration curves.

Claims

1. Claims A method for monitoring the conversion status of a hydrogen-carrying organic liquid (HCOL), comprising the following steps: i. At least one fluorescence measurement of a hydrogen-carrying organic liquid to obtain at least one quantitative data De relating to at least one fluorescence parameter F of said hydrogen-carrying organic liquid studied; and Comparison of said data DE relating to at least one fluorescence parameter F with the data DH and / or Dd corresponding respectively to the data relating to at least one fluorescence parameter F of the totally hydrogenated organic liquid carrying hydrogen and of the totally dehydrogenated organic liquid carrying hydrogen; and in which the hydrogen-carrying organic liquid is relative to: • to a fully hydrogenated organic hydrogen-carrying liquid / fully dehydrogenated organic hydrogen-carrying liquid pair in which the fully hydrogenated organic hydrogen-carrying liquid has the following formula (I): [Chem. 52] (I), in which: n is 0, 1, 2, 3, 4 or 5; at least one of the carbons of [Chem. 53] being optionally substituted by a group independently selected from C1-C4 linear or branched alkyls and Y groups; X and Y are independently a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear or branched C1-C4 alkyl groups, linear or branched C1-C4 O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or branched C1-C4 alkyl groups; Or • to a fully hydrogenated organic liquid carrier / fully dehydrogenated organic liquid carrier couple in which the fully hydrogenated organic liquid carrier has the following formula (!): [Chem. 54] . ,NH2 (D, in which: n is 0, 1, 2, 3 or 4; at least one of the carbons of [Chem. 55] s . v / being optionally substituted by a group Rb independently selected from linear or branched C1 to C4 alkyls and groups Y; X and Y are independently a perhydrogenated aryl group or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from C1-C4 linear or branched alkyl groups, C1-C4 linear or branched O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from C1-C4 linear or branched alkyl groups; Or • to a pair of composition of totally hydrogenated organic liquids carrying hydrogen / totally dehydrogenated organic liquid(s) carrying hydrogen in which the composition of totally hydrogenated organic liquids carrying hydrogen comprises: at least one first compound of the following formula (I): [Chem. 56] (I”), And - at least one second compound of formula (II”) or (III”) following: [Chem.57] (H”), [Chem. 5 8] R:5Xv,0 O (III”), in which: n is 0, 1, 2, 3 or 4; Ri is H, a straight or branched C1-C4 alkyl group, or a Y group; X is H, a C1-C4 linear or branched alkyl group, a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said perhydrogenated aryl or heteroaryl group being optionally substituted with at least one R2 group, independently selected from C1-C4 linear or branched alkyl groups, C1-C4 linear or branched O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from C1-C4 linear or branched alkyl groups; or n=0, and X forms with Ri a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; Y is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group, said group being optionally substituted by at least one R2 group, independently selected from linear alkyl groups or C1-C4 branched, linear or C1-C4 branched O-alkyl groups, -NRaRb groups, with Ra and Rb independently selected from linear or C1-C4 branched alkyl groups; R3 is: a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; a group -R-Cy where R is a linear or branched C1 to C6 alkane diyl and Cy is a perhydrogenated aryl group, or a perhydrogenated heteroaryl group; or a linear or branched C2 to C6 alkyl group substituted by at least one -OH group or one -CH2-OH group; or when the at least first compound of formula (I”) comprises at least one perhydrogenated aryl or perhydrogenated heteroaryl group: H, or a linear or branched C1 to C6 alkyl group.

2.

3. The method of claim 1, wherein said at least one fluorescence measurement of step (i) is performed: on the surface of said liquid; and / or on the undiluted organic hydrogen-carrying liquid; and / or with a light collection angle of 40 to 50°, in particular about 45°. The method of claim 1 or 2, wherein said at least one quantitative data DE relating to the fluorescence parameter F is obtained by measuring the excitation spectrum and / or the emission spectrum of said hydrogen-carrying organic liquid, said fluorescence parameter F being in particular: the characterization of the maxima(s) of the excitation spectrum and / or the emission spectrum, and said quantitative data DE being in particular the wavelength of the maxima(s), and possibly the width at half-height of the maxima(s); or translated into a color, for example defined by its chromatic coordinates.

4. Method according to claim 1, in which the comparison of step (ii) is made by means of a calibration curve, established from the DH and / or Dd data.

5. Method according to any one of the preceding claims, in which the fully hydrogenated hydrogen-bearing organic liquid dehydrogenates into a fully dehydrogenated hydrogen-bearing organic liquid or the fully dehydrogenated hydrogen-bearing organic liquid hydrogenates into a fully hydrogenated hydrogen-bearing organic liquid: - via one or more intermediates, said step (ii) additionally comprising the comparison of said data DE relating to the at least one fluorescence parameter F with the data D, corresponding to these intermediates; and / or - by also forming one or more secondary products, said step (ii) additionally comprising the comparison of said data DE relating to the at least one fluorescence parameter F with the data D, corresponding to these secondary products.

6. The method of claim 1, wherein the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is selected from cyclohexyl-methanol, 1-cyclohexylethanol, 4-methylcyclohexanemethanol, dicyclohexylcarbinol, and cyclohexanepropanol.

7. The method of claim 1, wherein the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / fully dehydrogenated hydrogen-carrying organic liquid pair in which the fully hydrogenated hydrogen-carrying organic liquid is selected from cyclohexyl-methanamine, 2-cyclohexylethanamine, cyclohexanepropanamine, 4-methylcyclohexylmethanamine, l-(2-methylcyclohexyl)methanamine, l-(3-methylcyclohexyl)methanamine.

8. The method of claim 1, wherein the hydrogen-carrying organic liquid relates to a fully hydrogenated hydrogen-carrying organic liquid / carrying organic liquid pair. of fully dehydrogenated hydrogen in which the organic liquid carrying fully hydrogenated hydrogen is chosen from the following compositions: - cyclohexanol + cyclohexylmethanol; - cyclohexanol + methanol; - methanol + 1,4-butanediol; - methanol + 1,3-butanediol; - methanol + 1,3-propanediol; - methanol + 1,5-pentanediol; - methanol + 1,4-pentanediol; - methanol + 1,3-pentanediol; - methanol + 2,4-pentanediol; - cyclohexylethanol + methanol.

9. Method according to any one of the preceding claims, which is implemented: - in a portable, on-board, and / or autonomous device; and / or - in situ.

10. Method according to any one of the preceding claims, which is carried out before and / or after: - the transport of said hydrogen-carrying organic liquid. - the dehydrogenation of said hydrogen-carrying organic liquid, which is in particular completely hydrogenated; - the hydrogenation of said hydrogen-carrying organic liquid, which is in particular completely dehydrogenated; - one or more dehydrogenation / hydrogenation cycles relating to said hydrogen-carrying organic liquid.

11. A method according to any preceding claim, which is carried out to monitor the degradation or wear of said hydrogen-carrying organic liquid.

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