RU2793733C2 - Process for producing and regenerating hydrogen-carrier compounds - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention proposes a process for producing a liquid siloxane hydrogen-carrier compound, including X, Y or Z reaction paths, comprising the following successive steps: obtaining a silicon dioxide based compound and/or a compound based on silicate and: in the case of reaction route X, carrying out a halogenation step silica-based compounds and/or silicate-based compounds to form silicon tetrahalide; carrying out a step of reducing silicon tetrahalide to obtain a halosilane, and carrying out a step of hydrolysing the halosilane to obtain a liquid siloxane hydrogen carrier compound; in the case of reaction route Y, carrying out the step of reducing the silica-based compound and/or the silicate-based compound to obtain silicon to obtain silicon; carrying out a step of hydrohalogenating silicon to obtain a halosilane, and carrying out a step of hydrolysing the halosilane to obtain a liquid siloxane hydrogen carrier compound; in the case of reaction route Z, carrying out the step of halogenating the silica-based compound and/or the silicate-based compound to obtain silicon tetrahalide; carrying out the stage of reduction of silicon tetrahalide to obtain silicon; carrying out a step of hydrohalogenating silicon to obtain a halosilane; and carrying out a step of hydrolysing the halosilane to obtain a liquid siloxane hydrogen carrier compound. Also proposed are a method for regenerating a liquid siloxane hydrogen carrier compound, a corresponding carbon-free liquid siloxane hydrogen carrier compound, a method for producing hydrogen using it, and using a liquid siloxane hydrogen carrier compound for storing and transporting hydrogen (variants).

EFFECT: improving the efficiency, productivity and economy of energy carriers.

29 cl, 6 dwg, 1 tbl, 3 ex

Description

The present invention relates to a process for the production and regeneration of siloxane hydrogen carrier compounds. The present invention also relates to hydrogen carrier siloxane compounds and to a process for producing hydrogen from said hydrogen carrier siloxane compounds.

Ensuring the ability of a source to store, transport and release hydrogen in a safe, convenient and environmentally friendly manner, and producing and storing hydrogen in an efficient, economical and safe manner, are the main challenges to be overcome in order to democratize the use of hydrogen as an energy carrier.

At present, hydrogen is mainly supplied by pipeline, in pipe trailers in the form of compressed gas, or in special tanks in its liquefied form.

There are usually 6 ways to supply hydrogen: it can be transported through a pipeline as a gas, it can be obtained at the place of use, it can be transported as a compressed gas in pipe trailers (for example, as disclosed in WO 2013/109918 (A1)), it can be transported as a condensed liquid in cryogenic tank trucks (for example, as disclosed in WO 2011/141287 (A1)), it can be stored in a solid state hydrogen carrier material and recovered at the point of use (for example, as disclosed in WO 2009/080986 (A2)), and it can be stored in a liquid state hydrogen carrier material and recovered at the point of use.

Hydrogen can be obtained at the point of use in two ways. It can be obtained at the point of use in one way and directly consumed in another way, it is called captured hydrogen. Another way to produce at the point of use is the electrolysis of water, in which hydrogen is produced from water and electricity. This can be considered environmentally friendly hydrogen production if renewable energy is used.

In addition to the above solutions to the supply problem, which are the supply of cryogenic and compressed hydrogen, alternative solutions for hydrogen production arise: the use of hydrogen carriers. Hydrogen carriers are solid or liquid materials that have the ability to store hydrogen and release it when needed. They provide transportation or storage advantages over the above solutions to the supply problem. Solid state carriers include metal hydrides in which hydrogen is captured by adsorption to metal particles, resulting in the formation of a metal hydride. These include magnesium hydride, which is stable at low pressure and standard temperature, making it convenient to transport and store. If necessary, the material is heated and hydrogen gas is released. Solutions using solid state materials have been found to be the most suitable for in-situ reversible energy storage procedures derived from renewable energy sources. In fact, the handling of solid materials is not as convenient as the handling of gaseous or liquid materials.

Liquid hydrogen carriers can be any materials in the liquid state capable of releasing hydrogen under specific conditions. Of the liquid hydrogen carriers, the class of liquid organic hydrogen carriers (LHOH) is the most widely represented. In a reaction called hydrogenation, which is a catalytic reaction that requires a supply of energy in the form of heat, hydrogen is chemically bonded to a liquid organic carrier. Typically, the carrier, which is an unsaturated and/or aromatic hydrocarbon, such as toluene, reacts with hydrogen to form the corresponding saturated hydrocarbon, which is transported in a liquid state at standard temperature and pressure, as described, for example, in WO 2014/082801 ( A1) or WO 2015/146170 (A1). Although the amount of hydrogen stored in the LEV depends on the yield of the hydrogenation reaction, the hydrogen content is up to 7.2 wt. % hydrogen, based on the weight of the liquid carrier. The hydrogen is then separated from the saturated hydrocarbons in a reaction called dehydrogenation, which is a catalytic reaction that requires energy in the form of heat (typically above 300° C.) due to the endothermic nature of the reaction. To produce hydrogen on demand, heat can be supplied using electricity from the grid (without verification of its source and environmental impact) or heat can be provided by burning part of the organic carrier.

Patent applications WO 2010070001 (A1) and EP 2206679 (A1) relate to a process for producing hydrogen, comprising the steps a) reacting a compound (C) containing one or more Si-H groups with a source of fluoride ions, thereby producing hydrogen and by-product (C1); and b) recovering the produced hydrogen. In all examples, silanes are used as hydrogen carriers; except for the use of polymethylhydrosiloxane ("PHMS") in example 12 and tetramethyldisiloxane in example 16.

Patent application WO 2011098614 (A1) relates to a process for producing hydrogen comprising the steps of: i) reacting a compound (C) containing one or more Si-H groups with a phosphorus-based catalyst in the presence of a base, in water used as a solvent, thereby producing hydrogen and a by-product (C1) without the need to supply any energy (eg, supply heat, electric power, etc.); and ii) recovering the generated hydrogen. In all examples, silanes are used as hydrogen carriers; tetramethyldisiloxane is the only siloxane-containing compound listed in the list of possible hydrogen carriers. WO 2011098614 (A1) also discloses step c) reusing the resulting by-product (C1) together with the acyl halide and reacting the resulting product with a metal hydride, thereby regenerating the compound (C), where the acyl halide is CH ₃ C(=O )Cl and the metal hydride is LiAlH ₄ .

Patent application WO 2010094785 (A1)) relates to a process for producing hydrogen comprising the steps of: i) reacting a compound (C) containing one or more Si-H groups with an amine-based catalyst in a solvent selected from the group, comprising an alcohol or an aqueous solution, thereby producing hydrogen and a by-product (C1) without the need to supply any energy (eg, supply heat, electric power, etc.); and ii) recovering the generated hydrogen. In most examples, silanes are used as hydrogen carriers; except for the use of polymethylhydrosiloxane ("PHMS") in Example 12 and tetramethyldisiloxane in Example 16. WO 2010094785 (A1) also discloses step c) reusing the resulting by-product (C1) together with the acyl halide and reacting the resulting product with a metal hydride with thus providing regeneration of the compound (C) wherein the acyl halide is CH ₃ C(=O)Cl and the metal hydride is LiAlH ₄ .

Although WO 2010070001 (A1), EP 2206679 (Al), WO 2011098614 (A1) and WO 2010094785 (A1) have already presented a significant advance in the field of a hydrogen-based carrier system that provides hydrogen on demand, these techniques will be favorable improved efficiency, productivity and economy; in addition, since in the whole hydrogen-based carrier regeneration method according to WO 2011098614 (A1) and WO 2010094785 (A1), it is necessary to use an expensive reducing agent - LiAlH ₄ , the use of which leads to the production of a by-product - alumina, the reprocessing of which is energy-intensive (a large amount of electricity is needed for the electrolysis step), leads to pollution and the release of carbon dioxide (CO ₂ ), carbon monoxide (CO), fluorine-containing effluents and polycyclic aromatic hydrocarbons (PAHs), further work is still needed to develop more environmentally friendly a favorable and carbon-free regeneration method applicable to a hydrogen-based carrier.

Thus, there remains a need for further improvements in the efficiency, performance and economy of such clean energy carriers for a wide variety of applications such as hydrogen delivery and hydrogen infrastructure construction. There remains a need for improvements to provide a greater amount of transportable hydrogen, improved efficiency, productivity and economy. There remains a particular need for environmentally friendly liquid hydrogen carriers that are capable of releasing hydrogen on demand without the need for additional power supply. In addition, there remains a need for an integrated clean process in which not only can hydrogen carriers be used as a valuable source of hydrogen, but they can also be produced without the need for a carbonaceous reagent and/or without carbon emissions, and also recovered from the by-products obtained in the separation of hydrogen, in an environmentally friendly manner and without significant carbon emissions, preferably without carbon emissions.

DESCRIPTION OF THE INVENTION

According to the invention, it has been found that liquid hydrogen-carrying siloxane compounds can be obtained from a silica-based compound and/or a silicate-based compound without the need for a carbonaceous reactant and/or without significant carbon emissions, preferably without carbon emissions.

In accordance with the present invention, a silica-based compound can be defined as a silica-containing compound and/or a mixture of two or more of said silica-containing compounds.

In one embodiment of the present invention, the silica-based compound is selected from the following:

a silica-based compound of the generic formula SiO ₂ ⋅xH ₂ O, [SiO ₂ ] _n , where n is greater than or equal to 2, or

- a mixture of two or more of these compounds based on silicon dioxide.

In accordance with the present invention, a silicate-based compound can be defined as a silicate-containing compound and/or a mixture of two or more of said silicate-containing compounds.

In one embodiment of the present invention, the silicate-based compound is selected from the following:

a sodium or potassium silicate compound of the generic formula Na _2x SiO _2+x or K _2x SiO _2+x , in which x is an integer from 0 to 2, or a silicic acid compound of the generic formula [SiO _x (OH) _4-x ] ^x , in which x is an integer from 0 to 4, or the generic formula [SiO _x (OH) _4-2x ] _n , in which if n=1, then x=0 or 1 and, if n=2, then x=1/2 or 3/2, or

a silicate-based compound having a polymer structure, such as a disilicate ion having the structure (Si ₂ O ₇ ) ^6- , or a macroanion having the generic structure [SiO ₃ ^2- ] _n , [Si ₄ O ¹¹ ₆ ] _n or [ Si ₂ O ₅ ^2- ]n, where n is greater than or equal to 2, or

- a mixture of two or more of these compounds based on silicate.

According to the invention, it has also been found that liquid siloxane hydrogen carrier compounds can be regenerated without the need for a carbon-containing reagent and/or without significant carbon emissions, preferably without carbon emissions.

The most important advantages of the production/regeneration processes of the present invention are that they can be carried out continuously; such continuous processes can also be carried out without the need to add starting materials and/or without emitting by-products.

According to the invention it has also been found that by using certain liquid hydrogen carrier siloxane compounds,

- it is possible to obtain hydrogen in large quantities, with high yields, in a very short time and at very low production costs, without the expenditure of energy for its release; And

- it is possible to obtain said siloxane hydrogen-carrying compounds without significant carbon emissions, preferably without carbon emissions, with energy conservation and reuse of by-products formed during hydrogen production.

The term "hydrogen carrier compound" can be understood to mean a chemical compound capable of storing hydrogen, carrying hydrogen, and releasing hydrogen on demand; a feature of the hydrogen carrier compounds of the present invention is that they can store/transport/release hydrogen without the need for an energy supply (eg, heat, electricity, etc.).

Method for obtaining liquid siloxane compounds-carriers of hydrogen

The present invention relates to a process for preparing liquid siloxane hydrogen carrier compounds from a silica-based compound and/or a silicate-based compound without the need for a carbonaceous reactant and/or without significant carbon emissions, preferably without carbon emissions.

Although the silica and/or silicate-based compound (B) defined below in the present invention is the preferred source for the starting material for the method for producing liquid hydrogen-carrying siloxane compounds of the present invention as the source for the starting material, for the process for preparing liquid hydrogen-carrying siloxane compounds, minerals containing silica and/or other silicates, such as, for example, zircon, jade, mica, quartz, cristobalite, sand, and the like, can be advantageously used. For the purposes of the present invention and the appended claims, it is preferable if the silica and/or silicate-based compound (B) is a silica-based compound and/or a silicate-based compound obtained by hydrolytic oxidation of a hydrogen carrier siloxane compound(s).

Method for Regeneration of Hydrogen Carrier Siloxane Compounds The present invention also relates to a method for regenerating liquid hydrogen carrier siloxane compounds, said method comprising a step of hydrolytically oxidizing hydrogen carrier siloxane compounds to produce hydrogen and a silica and/or silicate-based compound (B), and the step of converting said silica and/or silicate-based compound (B) into liquid hydrogen-carrying siloxane compounds, said process does not require the use of a carbonaceous reagent and/or proceeds without significant carbon emissions, preferably without carbon emissions.

The preparation and recovery of the liquid siloxane hydrogen carrier compounds of the present invention are further detailed and explained in the description below. The successful development of suitable processes that do not require the use of a carbonaceous reactant and/or proceed without significant carbon emissions, preferably without carbon emissions, represents an important advance in the field of hydrogen energy, hydrogen transport and the use of hydrogen in the automotive industry.

Siloxane Hydrogen Carrier Compounds

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds are selected from the following compounds.

In one embodiment, the present invention also relates to liquid siloxane hydrogen carrier compounds containing one or more units of formula (I):

wherein n is an integer (means the number of repeat units) greater than or equal to 1, preferably greater than or equal to 2, such as greater than or equal to 3, or even greater than or equal to 4. In one embodiment of the present invention, n is less than or equal to 500, such as , less than or equal to 50.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a cyclic or linear chemical structure. Such compounds have significant advantages over their poly(hydromethyl)siloxane counterparts (ROMe _n H _n Si _n O _n R'). For example, poly(bis(hydro))siloxane can release more than twice as much hydrogen gas as poly(hydromethyl)siloxane (exactly 2.61 times more for the same mass). In addition, poly(bis(hydro))siloxane compounds can be recycled with no carbon emissions (when used in the processes of hydrogen production and production/regeneration of siloxanes proposed in the present invention), unlike analogues containing carbon fragments in their main chains.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compound of formula (I) is a linear compound, for example, a linear compound of formula ROH _2n Si _n O _n R', wherein n is an integer greater than or equal to 1, preferably greater than or equal to 2, for example, greater than or equal to 3 or even greater than or equal to 4, R and R' can preferably be selected from among the following: Me, Et, Pr, iPr, Bu, tBu, Ph and/or SiR'' ₃ where R '' is selected from among the following: H, Me, Et, Pr, iPr, Bu, tBu and/or Ph. In one embodiment of the present invention, n is less than or equal to 500, such as less than or equal to 50.

In a preferred embodiment of the present invention, the liquid siloxane hydrogen carrier compound of formula (I) is a linear compound, for example a linear compound of the formula ROH _2n Si _n O _n R', wherein n is an integer greater than or equal to 1, preferably greater than or equal to 2, for example, greater than or equal to 3 or even greater than or equal to 4, where the radicals R and R' do not contain carbon; preferably, if R and R' are selected from among the radicals defined in the previous paragraph, where the radicals R and R' do not contain carbon; most preferably R and R' are SiH ₃ . In one embodiment of the present invention, n is less than or equal to 500, such as less than or equal to 50.

In the case of linear siloxane hydrogen carrier compounds, compounds containing a carbon-free radical at the end of the chain (eg SiH ₃ ) are chosen because this provides numerous advantages (compared to other compounds containing carbon-containing radicals at the end of the chain, such as, for example, , SiMe ₃ ):

- lower molecular weight, providing a higher mass efficiency of the siloxane compound, this means a higher ratio of the mass of hydrogen contained in the compound to the total molecular weight of the compound,

- direct and carbon-free reuse of compounds containing SiH ₃ at the end of the chain, in contrast to compounds containing at the end of the chain, for example, SiMe ₃ , since H ₃ SiCl is a by-product formed during the regeneration process ( see step 4), which is therefore valuable and does not require the addition of an external starting material for its regeneration.

In a preferred embodiment of the present invention, the liquid siloxane hydrogen carrier compounds do not contain carbon atoms. However, for the purposes of the present invention and the appended claims, and in order to avoid unduly limiting the scope of the present invention, the inventors of the present invention use the expression "without significant carbon emissions" to allow for some carbon emissions; for example, the hydrogen carrier siloxane compounds of the present invention may contain carbon, provided that the corresponding carbon content of said hydrogen carrier siloxane compounds is less than 25 wt. %. Said carbon content can be calculated by determining the ratio of the molecular weight (expressed in g/mol) of all carbon atoms contained in the hydrogen carrier siloxane compound to the total molecular weight (expressed in g/mol) of the hydrogen carrier siloxane compound. In one embodiment of the present invention, the carbon content is less than 10 wt. %, preferably less than 5 wt. %, for example, less than 2 wt. % or even more preferably if it is equal to 0 wt. %.

In a preferred embodiment of the present invention:

- if the liquid siloxane hydrogen carriers do not contain carbon, then there are no carbon emissions, and

- if the siloxane hydrogen carrier compounds contain carbon, then the corresponding carbon emissions will be less than 0.924 kg of CO ₂ in terms of 1 kg of produced and/or regenerated siloxane hydrogen carrier compound, preferably less than 0.462, more preferably less than 0.231, for example, less than 0 .1 or even less than 0.05 kg CO ₂ .

In a preferred embodiment of the present invention, the liquid siloxane hydrogen carrier compound of formula (I) is a cyclic compound, for example a cyclic compound of the formula H _2n Si _n O _n , wherein n is an integer greater than or equal to 2, such as greater than or equal to 3 or even greater than or equal to 4. In one embodiment of the present invention, n is less than or equal to 500, such as less than or equal to 32, such as less than or equal to 17.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds comprise one of the siloxane hydrogen carrier compounds of formula (I) defined above.

In another embodiment of the present invention, the liquid siloxane hydrogen carrier compounds comprise a mixture of two or more of any of the above-defined siloxane hydrogen carrier compounds of formula (I).

In this embodiment, using a "mixture", if the linear siloxane hydrogen carrier compounds of formula (I) are the substances contained in the largest amount, based on the weight of the mixture (i.e., their content is more than 50 wt.%), then it is preferable to limit the amount of cyclic siloxane hydrogen carrier compounds of formula (I) in the mixture to less than 20 wt. %, for example, less than 10 wt. %; in one embodiment, preferably, if the specified mixture may contain more than 0.01 wt. % or even more than 0.1 wt. % cyclic siloxane hydrogen carrier compounds of formula (I).

In this embodiment, using a "mixture", if the cyclic siloxane hydrogen carrier compounds of formula (I) are the substances contained in the largest amount, based on the weight of the mixture (i.e., their content is more than 50 wt.%), then it is preferable to limit the amount of linear siloxane hydrogen carrier compounds of formula (I) in the mixture to less than 20 wt. %, for example, less than 10 wt. %; preferably, if the specified mixture may contain 0.01 wt. % or even 0.1 wt. % linear siloxane hydrogen carrier compounds of formula (I).

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a dynamic viscosity at a temperature of 20° C. and a pressure of 1.01325×10 ⁵ Pa, from 0.1 to 10,000 mPa.s. In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a dynamic viscosity at a temperature of 20° C. and a pressure of 1.01325×10 ⁵ Pa, equal to 0.2 to 50 mPa.s. The dynamic viscosity of the hydrogen-carrying siloxane compounds of formula (I) at a temperature of 20° C. and a pressure of 1.01325×10 ⁵ Pa can be determined according to any suitable technique; for example, it can be defined according to the ISO 1628-1 standard.

In one embodiment of the present invention, the molecular weight of the liquid cyclic siloxane hydrogen carrier compounds of formula (I) may range from 130 to 800 g/mol. The molecular weight of the hydrogen-carrying siloxane compounds of formula (I) can be determined according to any suitable technique; for example, it can be determined using GC-MS (gas chromatography - mass spectrometry), for example, by analysis using GC-MS, carried out using the instrument Agilent GC/MSD 5975C.

In one embodiment of the present invention, the number average molecular weight (M _n ) and/or molecular weight distribution (D) of the liquid linear siloxane hydrogen carrier compounds of formula (I) may range from 64 to 30,000 g/mol and from 1.1 up to 50 respectively. The number average molecular weight and molecular weight distribution of the linear siloxane hydrogen carrier compounds of formula (I) can be determined according to any suitable technique; for example, they can be defined according to the ISO 16014 standard.

In one embodiment of the present invention, liquid cyclic siloxane hydrogen carrier compounds of formula (I) have a characteristic strong and narrow absorption band in the range of 800 to 1000 cm ^-1 corresponding to SiH units, as determined by FTIR analysis. ₂ . In one embodiment of the present invention, the cyclic siloxane hydrogen carrier compounds of formula (I) have a characteristic intense and narrow absorption band in the range of 850 to 950 cm ^-1 .

In one embodiment of the present invention, according to analysis using ¹ H NMR (nuclear magnetic resonance) conducted in CDCl ₃ at 25°C, liquid cyclic siloxane hydrogen carrier compounds of formula (I) have a characteristic resonance signal in the range of 4.5 up to 4.9 ppm corresponding to the SiH ₂ O units, as shown in FIG. 4. ¹ H NMR analysis can be performed using any suitable spectrometer, such as a Bruker spectrometer, 400 MHz.

In one embodiment of the present invention, according to analysis using ²⁹ Si NMR conducted in CDCl ₃ at 25°C, liquid cyclic siloxane hydrogen carrier compounds of formula (I) have a characteristic resonance signal in the range from -45 to -50 ppm./ ppm, corresponding to the units of SiH ₂ O, as shown in Fig. 5. ²⁹ Si NMR analysis can be performed using any suitable spectrometer, such as a Bruker spectrometer, 400 MHz.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a refractive index at a temperature of 20° C. and a wavelength of 589 nm of 1 to 2. In one embodiment of the present invention, the liquid siloxane compounds -hydrogen carriers of formula (I) have a refractive index at a temperature of 20° C. and a wavelength of 589 nm of 1.2 to 1.5. The refractive index of the hydrogen-carrying siloxane compounds of formula (I) can be determined according to any suitable technique; for example, it can be determined according to ASTM D1218.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a boiling point at a pressure equal to 1.01325×10 ⁵ Pa, equal to from 30 to 500°C, for example, from 50 to 500°C, for example, boiling point of 50 to 150°C. The boiling point of the liquid siloxane hydrogen carrier compounds of formula (I) can be determined according to any suitable technique; for example, it can be defined according to the ISO 918 standard.

In one embodiment of the present invention, the liquid siloxane hydrogen carrier compounds of formula (I) have a flash point of 50 to 500°C. The flash point of the hydrogen-carrying siloxane compounds of formula (I) can be determined according to any suitable technique; for example, it can be defined according to the ISO 3679 standard.

In one embodiment of the present invention, the liquid hydrogen carrier siloxane compounds of formula (I) are selected from among the cyclic siloxane compounds represented by the formula

wherein n is an integer (means the number of repeat units) greater than or equal to 1, preferably greater than or equal to 2, such as greater than or equal to 3, or even greater than or equal to 4. In one embodiment of the present invention, n is less than or equal to 500, such as , less than or equal to 32, for example, less than or equal to 17. In one embodiment of the present invention, the liquid hydrogen-carrying siloxane compounds comprise any mixture of two or more of said liquid cyclic siloxane compounds.

In one embodiment of the present invention, the liquid hydrogen carrier siloxane compounds of formula (I) are selected from linear siloxane compounds having the formula

in which n is an integer greater than or equal to 1, preferably greater than or equal to 2, such as greater than or equal to 3, or even greater than or equal to 4. In one embodiment of the present invention, n is less than or equal to 500, such as less than or equal to 50. In one embodiment of the present invention, the liquid hydrogen-carrying siloxane compounds comprise any mixture of two or more of said liquid linear siloxane compounds.

In accordance with the present invention, the siloxane hydrogen carrier compounds of formula (I) are liquid (at normal temperature and pressure (NTP); for example, at a temperature of 20° C. and an absolute pressure of 1.01325×10 ⁵ Pa.

The present invention also relates to hydrogen carrier compounds comprising a mixture of siloxane hydrogen carrier compounds of formula (I) and water. For the method for producing hydrogen, proposed in the present invention, the specified water is considered a reagent. Preferably, the water may be selected from a number of different sources such as, for example, fresh water, running water, tap water, salt water, deionized water and/or distilled water.

In one embodiment of the present invention, said mixture of siloxanes and water is characterized by a water/[SiOH ₂ ] molar ratio greater than or equal to 0.1. In one embodiment of the present invention, said mixture of siloxanes and water is characterized by a molar ratio of water/units [SiOH ₂ ], which is from 2 to 10, for example, from 2 to 2.5. So, for example, in the case of polyhydrosiloxane "PGS", the corresponding mixture of water/PGS will be characterized by the value of the molar ratio, calculated as the ratio H ₂ O/PGS=(m _H2O /M _H2O )/(m _PGS /M _SiH2O )=(m _H2O / 18)/(m _PGS /46.11).

The present invention also relates to hydrogen carrier compounds comprising a mixture of siloxane hydrogen carrier compounds of formula (I) and at least one hydrogen evolution initiator, and water. For the hydrogen production process of the present invention, said hydrogen evolution initiator is considered a reactant. The type of hydrogen evolution initiator that can be used in accordance with the present invention is not limited as long as it promotes hydrolytic oxidation of the hydrogen-carrying siloxane compounds of formula (I); and thus the reaction of the siloxane leading to the corresponding evolution of hydrogen. Thus, for example, any compound that promotes the hydrolytic oxidation of the siloxane can be successfully used as the hydrogen evolution initiator.

In one embodiment of the present invention, the hydrogen evolution initiator is selected from the group consisting of one or more of the compounds listed below:

- inorganic base; for example, the inorganic base may be an alkali or alkaline earth metal hydroxide such as potassium hydroxide or sodium hydroxide, sodium hydroxide is particularly preferred;

- a compound capable of releasing a nucleophilic reagent allowing hydrolytic oxidation of a siloxane hydrogen carrier compound, such as, for example, a compound of the formula RR'R''R'''ZY, in which Z is N or P, Y is OH, F, Cl or Br, and R, R', R'' and R''' may preferably be selected from the group comprising C ₁ -C ₁₅ -alkyl or C ₆ -C ₁₀ -aryl, where R, R', R'', R''' are the same or different;

a homogeneous organometallic catalyst capable of promoting the hydrolytic oxidation of the siloxane hydrogen carrier compound, such as, for example, organometallic complexes based on iron, ruthenium, rhenium, rhodium, copper, chromium, iridium, zinc and/or tungsten, and the like; And

- a heterogeneous catalyst capable of promoting the hydrolytic oxidation of a siloxane hydrogen carrier compound, such as, for example, metal nanoparticles, [M/AlO(OH), M=Pd, Au, Rh, Ru and Cu], Pd/C and/or any of the above metals, preferably supported on an inorganic substrate.

In one embodiment of the present invention, the hydrogen evolution initiator is selected from carbon-free hydrogen evolution initiators, for example, it is sodium hydroxide.

The present invention also relates to hydrogen carrier compounds comprising a mixture of siloxane hydrogen carrier compounds of formula (I), water, a hydrogen evolution initiator as defined above, and catalyst C. For the hydrogen production process of the present invention, said catalyst C is considered a reactant . The type of catalyst C that can be used in accordance with the present invention is not limited as long as it improves the hydrolytic oxidation kinetics of the hydrogen-carrying siloxane compounds of formula (I) (i.e., increases the rate at which hydrogen evolution occurs); and thus the reaction of the mixture of water/siloxane/hydrogen evolution initiator/catalyst C resulting in a corresponding evolution of hydrogen. Thus, for example, any compound that significantly improves the kinetics of the hydrolytic oxidation of the siloxane can be advantageously used as catalyst C.

In one embodiment of the present invention, Catalyst C is selected from the group consisting of one or more of the following compounds:

a phosphorus-based catalyst (for example, a polymer-supported catalyst containing one or more phosphorus-containing groups);

- an amine-based catalyst (for example, a polymer-supported catalyst containing one or more amino groups) or an ammonium salt, for example, RR'R''R'''NOH, where R, R', R'', R''' denote C ₁ -C ₁₅ -alkyl or C ₆ -C ₁₀ -aryl and R, R', R'', R''' are the same or different;

- catalyst-source of fluoride ions (for example, tetrabutylammonium fluoride); And

- hexamethylphosphoramide ("HMPA").

In one embodiment of the present invention, none of the above Catalysts C individually is used in the hydrogen production process.

In one embodiment of the present invention, said mixture of siloxanes, water and hydrogen evolution initiator, and optional catalyst C has a hydrogen evolution initiator/[SiOH ₂ ] molar ratio greater than or equal to 0.01. In one embodiment of the present invention, said mixture of siloxanes, water, and hydrogen evolution initiator has a hydrogen evolution initiator/[SiOH ₂ ] molar ratio that is from 0.05 to 3, for example, from 0.05 to 0.35.

In one embodiment of the present invention, said mixture of siloxanes, water, hydrogen evolution initiator and catalyst C is characterized by a molar ratio of catalyst/(monomer units [SiOH ₂ ] contained in compound (I)), which is in the range from 0.01 to 0, 5. Preferably, the molar ratio of catalyst C/(monomer units [SiOH ₂ ] contained in the compound (I)) is in the range of 0.02 to 0.1. More preferably, if the molar ratio of the catalyst C/(monomer units [SiOH ₂ ] contained in the compound (I)) is less than 0.05, for example, 0.04.

When performing the above calculations of the ratios of the number of moles of initiator and catalyst C to the number of moles of [SiOH ₂ ] units, if the compound simultaneously meets the definition of hydrogen evolution initiator and the definition of catalyst C, then its full amount is used to calculate both ratios.

Getting hydrogen

The present invention also relates to a process for producing hydrogen by hydrolytic oxidation of siloxanes in the presence of water, where the siloxanes are liquid siloxane hydrogen carrier compounds containing one or more units of formula (I):

wherein n is an integer (means the number of repeat units) greater than or equal to 1, preferably greater than or equal to 2, such as greater than or equal to 3, or even greater than or equal to 4. In one embodiment of the present invention, n is less than or equal to 500, such as , less than or equal to 50.

In one embodiment of the present invention, the hydrogen carrier siloxane compounds of formula (I) are selected from among the liquid siloxanes already defined above in the present invention.

In one embodiment of the present invention, the hydrogen production process is characterized in that the molar ratio of water/[SiOH ₂ ] units is greater than or equal to 0.1. In one embodiment of the present invention, said mixture of siloxanes and water is characterized by a molar ratio of water/units [SiOH ₂ ], which is from 2 to 10, for example, from 2 to 2.5.

In one embodiment of the present invention, the hydrogen production process is characterized by the presence of at least one hydrogen evolution initiator during the hydrolytic oxidation of siloxanes in the presence of water. The type of hydrogen evolution initiator that can be used in accordance with the present invention is not limited as long as it promotes hydrolytic oxidation of the hydrogen-carrying siloxane compounds of formula (I); and thus reactions in the water/siloxane mixture leading to the corresponding evolution of hydrogen. Thus, for example, any compound that promotes the hydrolytic oxidation of the siloxane can be successfully used as the hydrogen evolution initiator; suitable hydrogen evolution initiators are already defined above in the present invention. In one embodiment of the present invention, said mixture of siloxanes, water and hydrogen evolution initiator, and optional catalyst C has a hydrogen evolution initiator/[SiOH ₂ ] molar ratio greater than or equal to 0.01. In one embodiment of the present invention, said mixture of siloxanes, water, and hydrogen evolution initiator has a hydrogen evolution initiator/[SiOH ₂ ] molar ratio that is from 0.05 to 3, for example, from 0.05 to 0.35.

In one embodiment of the present invention, the hydrogen production process is characterized by the presence of a mixture of siloxane hydrogen carrier compounds of formula (I), water, a hydrogen evolution initiator as defined above, and catalyst C. The type of catalyst C that can be used in accordance with the present invention does not limitations are imposed provided that it improves the hydrolytic oxidation kinetics of the hydrogen-carrying siloxane compounds of formula (I) (ie, increases the rate at which hydrogen evolution occurs); and thus reactions in a mixture of water/siloxane/hydrogen evolution initiator/catalyst C resulting in a corresponding evolution of hydrogen. Thus, for example, as Catalyst C, any compound that substantially improves the hydrolytic oxidation kinetics of the siloxane can be advantageously used; suitable catalysts C are already defined above in the present invention. In one embodiment of the present invention, said mixture of siloxanes, water, hydrogen evolution initiator and catalyst C is characterized by a molar ratio of catalyst/(monomer units [SiOH ₂ ] contained in compound (I)), which is in the range from 0.01 to 0, 5. Preferably, if the molar ratio of the catalyst C/(monomer units [SiOH ₂ ] contained in the compound (I)), is in the range from 0.02 to 0.1. More preferably, if the molar ratio of the catalyst C/(monomer units [SiOH ₂ ] contained in the compound (I)) is less than 0.05, for example, 0.04.

The present invention also relates to the use of selected siloxane hydrogen carrier compounds of formula (I) for the production of hydrogen.

There are no restrictions on the techniques that can be used in carrying out the method for producing hydrogen of the present invention, provided that no additional energy is required to separate hydrogen from a mixture of water/hydrogen carrier compounds of formula (I) and the requirements for production are satisfied. hydrogen.

In one embodiment of the present invention, the temperature during the process for producing hydrogen from siloxane hydrogen carrier compounds of formula (I) can vary over a wide range and preferably if it can be in the range from 0 to 200°C. More preferably, if the temperature is in the range from 15 to 30°C.

In one embodiment of the present invention, the pressure during the process for producing hydrogen from siloxane hydrogen carrier compounds of formula (I) can vary over a wide range and preferably if it can range from 1×10 ⁵ to 500×10 ⁵ Pa.

In one embodiment of the present invention, the process for producing hydrogen from siloxane hydrogen carrier compounds of formula (I) can be carried out in the presence of a solvent. The type of solvent that can be used in the hydrogen production process of the present invention is not limited as long as hydrogen production requirements for hydrogen production are satisfied in hydrogen recovery from hydrogen carrier compounds of formula (I). In one embodiment of the present invention, said solvent is selected from the group consisting of alcohol (eg, methanol), aqueous solvents, organic solvents, and/or a mixture of two or more of said solvents. For the method for producing hydrogen, proposed in the present invention, the specified solvent is considered a reagent.

In one embodiment of the present invention, a process for producing hydrogen from siloxane hydrogen carrier compounds of formula (I) comprises the steps of: a) reacting the siloxane hydrogen carrier compounds of formula (I) with Catalyst C to form a siloxane/catalyst mixture, and b) combining siloxane with an aqueous solution of a hydrogen evolution initiator in the presence of catalyst C to produce hydrogen. Steps a) and b) can be carried out sequentially or simultaneously.

In one embodiment of the present invention, the reaction mixture used in the process for producing hydrogen from hydrogen-carrying siloxane compounds of formula (I) is characterized in that

- siloxane hydrogen carrier compounds of the formula (I),

- corresponding by-products such as silicates,

- hydrogen,

- water,

- hydrogen evolution initiator(s), and

- an optional catalyst, and

- optional solvents,

are contained in an amount of at least 90 wt. %, based on the weight of said reaction mixture, preferably at least 95 wt. %, for example, not less than 99 wt. %.

In one embodiment, the present invention also relates to an apparatus for producing hydrogen in accordance with the method described above in the present invention, this apparatus includes a reaction chamber containing:

- an inlet for the reaction mixture, said mixture contains siloxane hydrogen carrier compounds of formula (I) and an optional solvent;

- outlet for hydrogen;

optionally a by-product collection device; And

optionally, a surface intended to be in contact with said mixture, which is coated with a polymer-supported catalyst as described above in the present invention.

Production of liquid siloxane and regeneration of liquid siloxane

As stated above in the present invention, the main objects of the present invention are to produce hydrogen carrier compounds and to regenerate hydrogen carrier compounds by reusing by-products from hydrogen production that are environmentally friendly and/or proceed without significant carbon emissions, preferably without carbon emissions. carbon.

Thus, the present invention relates to a process for producing liquid siloxane hydrogen carrier compounds from a silica-based compound and/or a silicate-based compound, preferably from a silica-based compound and/or silicate (B), without the need for a carbonaceous reagent and /or without significant carbon emissions, preferably without carbon emissions.

The present invention also relates to a method for regenerating a hydrogen carrier siloxane compound(s), said method comprising the step of hydrolytically oxidizing a hydrogen carrier siloxane compound(s) to produce hydrogen and a silica and/or silicate-based compound(s) (B), and the step of converting said silica and/or silicate-based compound(s) into hydrogen-carrying siloxane compounds, preferably the same hydrogen-carrying siloxane compound(s), said process does not require the use of a carbonaceous reagent and/or it proceeds without significant carbon emissions, preferably without carbon emissions.

In one embodiment, the present invention relates to a process for producing a liquid siloxane hydrogen carrier compound, comprising X, Y, or Z reaction pathways comprising the following sequential steps:

- obtaining a compound based on silicon dioxide and/or a compound based on silicate,

- in the case of reaction route X,

carrying out the step of halogenating the silica-based compound and/or the silicate-based compound to obtain a silicon tetrahalide, carrying out the step of reducing the silicon tetrahalide to obtain a halosilane, and

carrying out the step of hydrolysis of halosilane to obtain a liquid siloxane compound-carrier of hydrogen;

- in the case of reaction route Y,

carrying out the step of reducing the compound based on silicon dioxide and/or the compound based on silicate to obtain silicon,

carrying out the stage of silicon hydrohalogenation to obtain halosilane, and

carrying out the step of hydrolysis of halosilane to obtain a liquid siloxane compound-carrier of hydrogen;

- in the case of reaction route Z,

carrying out the step of halogenating the silica-based compound and/or the silicate-based compound to obtain silicon tetrahalide, carrying out the reduction step of silicon tetrahalide to obtain silicon,

carrying out the stage of silicon hydrohalogenation to obtain halosilane, and

carrying out the stage of hydrolysis of halosilane to obtain a liquid siloxane compound-carrier of hydrogen.

silicate/silica.

In one embodiment of the present invention, i. if a silicate is used as a raw material in the siloxane production/regeneration process, further processing (e.g., solvent evaporation, acid chemical treatment, pyrolysis) of the silicate can be preferably used to produce silicon dioxide (SiO ₂ ), the latter is used as a raw material in the siloxane production process .

In one embodiment of the present invention, the silica and/or silicate-based compound can be subjected to further mechanical processing, such as milling and/or sieving, prior to the reduction step using reaction route Y and/or prior to the halogenation step using reaction routes carrying out the reaction X and Z.

In one embodiment of the present invention relating to reaction route Y, the initial step of treating the silica-based compound and/or the silicate-based compound by carrying out the reduction step to obtain silicon can be carried out in one or two steps; for example, by a one-step reduction technique or by a two-stage reduction technique to obtain an intermediate SiO.

For the purposes of this specification and the appended claims, the following numbering is used for the individual reaction steps:

- in the case of reaction pathways X and Z,

halogenation of the silica and/or silicate-based compound to obtain silicon tetrahalide corresponds to step 2(a); any suitable source of halide can be used to carry out step 2(a), provided that it provides silicon tetrahalide;

- in the case of reaction route Y,

step 2(c) corresponds to a one-step reduction of the silica-based compound and/or the silicate-based compound to obtain silicon;

steps 2(b) and 3(c) correspond to a two-step reduction of the silica-based compound and/or the silicate-based compound to obtain silicon;

- in the case of reaction route Z,

стадия 3(а') и/или стадия 3(b) соответствует восстановлению тетрагалогенида кремния с получением кремния;

stage 3(a') and/or stage 3(b) corresponds to the reduction of silicon tetrahalide to obtain silicon;

- in the case of reaction route X,

stage 3(a) corresponds to the reduction of silicon tetrahalide to obtain halosilane;

- in the case of reaction pathways Y and Z,

stage 4 corresponds to the hydrohalogenation of silicon to obtain halosilane;

- in the case of reaction pathways X, Y and/or Z,

стадия 5 соответствует гидролизу галогенсилана с получением жидкого силоксанового соединения-носителя водорода.

step 5 corresponds to the hydrolysis of the halosilane to give a liquid siloxane hydrogen carrier compound.

For illustration, but not limitation, FIG. 1 describes in detail an example of a process for producing a siloxane, and FIG. 2 shows examples of individual process steps;

- Fig. 2, step 3(b): if Na is used as a reducing agent (step 3(b)), then the resulting 4 eq. NaF is reused and 4 eq. Na and 4 eq. HF in a manner not disclosed in the present invention.

- Fig. 2, step 3(c): if SiO is reduced using hydrogen (step 3(c)), then 2 eq. Si. 1 eq. The latter can be successfully redirected to step 2(b) to avoid any addition of Si during the process, and another 1 eq. The ("excess" amount) is successfully consumed in the next step 4 of the process.

- Fig. 2: step 4 of the production method is a multi-step procedure, which is not fully disclosed in the present invention.

In one embodiment, the present invention relates to a method for regenerating a liquid hydrogen carrier siloxane compound(s), comprising hydrolytically oxidizing a hydrogen carrier siloxane compound(s) to produce hydrogen and a silica and/or silicate (B) compound, followed by carrying out the reaction along the path X, Y or Z, which includes the following successive stages:

- in the case of reaction route X,

carrying out the step of halogenating the silica-based compound and/or the silicate-based compound (B) to obtain a tetrahalide, carrying out the step of reducing the silicon tetrahalide to obtain a halosilane, and

carrying out the stage of hydrolysis of halosilane to obtain a liquid siloxane compound (compounds) carrier of hydrogen, preferably the same liquid siloxane compound (compounds) carrier of hydrogen;

- in the case of reaction route Y,

carrying out the step of reducing the silica-based compound and/or the silicate-based compound (B) to obtain silicon,

carrying out the stage of silicon hydrohalogenation to obtain halosilane, and

carrying out the stage of hydrolysis of halosilane to obtain a liquid siloxane compound (compounds) carrier of hydrogen, preferably the same liquid siloxane compound (compounds) carrier of hydrogen;

- in the case of reaction route Z,

carrying out the step of halogenating the silica-based compound and/or the silicate-based compound (B) to obtain silicon tetrahalide,

carrying out the stage of reduction of silicon tetrahalide to obtain silicon,

carrying out the stage of silicon hydrohalogenation to obtain halosilane, and

carrying out the stage of hydrolysis of halosilane to obtain a liquid siloxane compound (compounds) carrier of hydrogen, preferably the same liquid siloxane compound (compounds) carrier of hydrogen.

For illustration, but not limitation, FIG. 3 describes in detail an example of a regeneration method that is carried out starting with the use of a siloxane hydrogen carrier compound, tri(bis(hydro)cyclosiloxane) (containing 3 repeating units, "D3");

- Fig. 3, stage 3(b): if Na is used as a reducing agent, then the resulting 4 eq. NaF is reused and 4 eq. Na and 4 eq. HF in a manner not disclosed in the present invention.

- Fig. 3, step 3(c): if SiO is reduced using hydrogen (step 3(c)), then 2 eq. Si. 1 eq. The latter is redirected to step 2(b) to avoid adding Si during the process, and another 1 eq. The ("excess" amount) is successfully consumed in the next step 4 of the process.

Said regenerated siloxane hydrogen carrier compounds can be advantageously used in the hydrogen production process of the present invention, allowing the cycle to be restarted.

A significant advantage provided by the polyhydrosiloxane compounds of the present invention used as hydrogen-based energy carriers (as opposed to PGMS and TMDS (tetramethyldisiloxane) due to the presence of a non-hydrolyzable methyl moiety associated with the central silicon atom) is that their complete hydrolysis during the process of hydrogen evolution leads to the formation of only compounds (compounds) based on silicon dioxide/silicate (B); said silica/silicate-based compound(s) (B) is the direct starting material for an environmentally friendly and/or carbon-free (preferably no-carbon) process, the detailed and atom-economical regeneration process ensures the recovery of the exact amount original liquid fuel.

Step 2(a) - halogenation of silica/silicate products (reaction X or Z routes)

In one embodiment, the present invention describes a procedure for halogenating a silica/silicate compound (B) with a halide source to produce silicon tetrahalide. Any source of halide can be used with success. The preferred halide source is hydrogen halide; said hydrogen halide may advantageously be an aqueous solution or gas, for example hydrogen fluoride (HF). For example, if hydrogen fluoride is used to carry out the halogenation step, silicon tetrafluoride and water are formed as a by-product; the water can be collected to be reused in the next process step, or electrolyzed to produce hydrogen and oxygen gases, the former being directly consumed in the next process step, for example.

Step 2(b) - Reduction of Silica/Silicate Type Products to SiO (Reaction Path Y - First Step of Two-Step Reduction)

In one embodiment, the present invention describes a method for reducing a compound based on silicon dioxide/silicate (B) in the presence of elemental silicon to obtain SiO. Any source of elemental silicon can be used with success. The preferred source of elemental silicon is metallurgical silicon. Since elemental silicon is used in the recovery step, 2 eq. SiO in terms of 1 equiv. converted silicate; the SiO formed is, for example, directly consumed in step 3(c) of the process.

An example of a method for producing Si from a silica/silicate-based compound (B), referred to in this case as silicon dioxide (SiO ₂ ), which includes a combination of steps 2(b) and 3(c), is shown in FIG. 1.

Step 2(c) - Reduction of Silica/Silicate Products to Si (Reaction Path Y - One-Step Reduction)

In one embodiment, the present invention describes a method for reducing a compound based on silicon dioxide/silicate (B) in the presence of hydrogen gas to obtain elemental silicon. The resulting elemental silicon may be metallurgical or photovoltaic. In addition to hydrogen, other gas(es) may optionally be used, for example an inert gas such as argon or nitrogen. Since the reduction reaction of silica/silicate compounds with hydrogen is endothermic, a heat source is needed; any heat source can be selected, such as arc technology, induction heating, microwave radiation, directly heated thermionic cathode, plasma technology. Especially preferred is the use of plasma; for example, an appropriate plasma technology may advantageously include a plasma torch to form a plasma jet. The plasma jet is preferably formed from hydrogen gas with or without the addition of additional gas(es) (such as, for example, argon) passing through the electrodes. Silicon can be introduced into a hydrogen-containing plasma jet under vacuum and then reacted in the gas phase at a temperature of 2000 to 20000°K to produce silicon and water. The silicon is then condensed and recovered as a solid.

During the reduction reaction of compounds based on silicon dioxide/silicate with hydrogen gas, water is formed as a by-product. The resulting water can be advantageously used as a chemical reactant and/or as a heat source for other purposes and/or it can be converted in an electrolyzer to produce hydrogen gas and/or can be used to run a steam turbine to generate electricity.

Stage 3(a) and 3(a') - reduction of silicon tetrahalide

In one embodiment, the present invention describes a method for the reduction of silicon tetrahalide with hydrogen gas (for example, hydrogen formed during the electrolysis of water collected during the previous stage; or hydrogen recovered in another stage of the method; or hydrogen inevitably obtained and collected during the implementation of another method) to obtain elemental silicon [stage 3(a')] and/or halosilane(s) [stage 3(a)], for example silane (SiH ₄ ), monohalosilane (H ₃ SiX) and/or dihalosilane (H ₂ SiX ₂ ), and/or trihalosilane (HSiX ₃ ), and/or tetrahalosilane (SiX ₄ ). In the case where silicon tetrafluoride (SiF ₄ ) is used as the source of silicon tetrahalide, carrying out the reduction step using hydrogen gas can produce elemental silicon and release hydrogen fluoride (HF) as a by-product [Step 3(a')] . Partial reduction may also occur, resulting in the formation of monofluorosilane and/or difluorosilane and/or trifluorosilane and/or tetrafluorosilane and the evolution of hydrogen fluoride (HF) as a by-product [step 3(a)]. Said HF formed can be advantageously re-added during the above halogenation step [step 2(a)], which provides an equilibrium material balance for steps (2) and (3) of the production/regeneration process.

Stage 3(b) - reduction of silicon tetrahalide

In one embodiment, the present invention describes a method for the reduction of silicon tetrahalide with a metal reducing agent to obtain elemental silicon. Alkali metals, such as sodium, can advantageously be chosen as the metal reducing agent. Performing a reduction step using an alkali metal such as sodium can produce elemental silicon and release sodium fluoride (NaF), which can be successfully reused in a multi-step Na and HF recovery procedure. Said regenerated Na can be successfully reused as a reducing agent in step 3(b) of the present invention, this provides an equilibrium material balance. This regenerated HF can be successfully reused, for example, in step 2(a) of the process, this ensures an equilibrium material balance.

Stage 3(c) - reduction of SiO with gaseous hydrogen

In one embodiment, the present invention describes a method for reducing SiO with gaseous hydrogen to obtain elemental silicon. Part of the elemental silicon produced can be advantageously re-added in step 2(b) to avoid any addition of elemental silicon during the process, the other ("excess" amount) of elemental silicon obtained is directly consumed in the next hydrohalogenation step 4 of the process.

Stage 4 - hydrohalogenation of elemental silicon

In one embodiment, the present invention describes a method of hydrohalogenation of elemental silicon to obtain halosilanes, for example, monohalosilane (H ₃ SiX), dihalosilane (H ₂ SiX ₂ ), trihalosilane (HSiX ₃ ) and/or tetrahalosilane (SiX ₄ ), or mixtures of these compounds. (X stands for halide). Preferably, the elemental silicon used in the hydrohalogenation step is obtained in a previous process step. To carry out said hydrohalogenation of elemental silicon to produce dichlorosilane (H ₂ SiCl ₂ ) and/or trichlorosilane (HSiCl ₃ ) and/or tetrachlorosilane (SiCl ₄ ), the preferred hydrogen halide source is hydrogen chloride (HCl); said hydrogen chloride may suitably be an aqueous solution or a gas. In case hydrogen chloride is used, the process can be carried out so as to redistribute HSiCl ₃ , which is the main product of the silicon hydrochlorination reaction, by a catalyzed disproportionation reaction to obtain a mixture of H ₃ SiCl, H ₂ SiCl ₂ , HSiCl ₃ and SiCl ₄ . SiCl ₄ can be successfully reused by carrying out the reduction reaction with hydrogen gas in the presence of elemental silicon to obtain a mixture of H ₂ SiCl ₂ , HSiCl ₃ and SiCl ₄ . Preferably, the elemental silicon used in the SiCl ₄ reduction step is obtained in a previous process step. The hydrogen gas used in the SiCl ₄ reduction step can advantageously be a by-product obtained from another process step, for example from the elemental silicon hydrohalogenation step described above. By carrying out several successive separation and purification steps, pure H ₂ SiCl ₂ can be isolated, which can be directly consumed in the next step (5) of the process.

Stage 5 - controlled hydrolysis of halosilanes

In one embodiment, the present invention describes a method for controlled hydrolysis of halosilanes using water to produce/regenerate siloxane hydrogen carrier compounds. If H ₂ SiCl ₂ is used as a source of halosilane to carry out said controlled hydrolysis, HCl is formed as a by-product. The resulting HCl can be successfully re-added during step 4 of the process. If H ₂ SiF ₂ is used as a source of halosilane to carry out said controlled hydrolysis, HF is formed as a by-product. The resulting HF can be successfully re-added during step 2(a) of the process. Said hydrolysis can be advantageously carried out in the presence of a terminator, preferably a carbon-free terminator such as H ₃ SiCl and the like. Final processing steps such as washing steps with or without inorganic base water, degassing, drying steps, and the like can be successfully carried out.

In one embodiment of the present invention, the amount of energy required to carry out the entire process for producing a siloxane hydrogen carrier of formula (I) may be from 1 to 200 kWh /(kg of siloxane produced), for example, from 1 to 35 kWh /( kg of siloxane obtained).

In one embodiment of the present invention, the amount of energy required to carry out the entire process for producing a siloxane hydrogen carrier of formula (I) may be from 1 to 2000 kWh / (kg of H ₂ released), for example, from 1 to 400 kWh / (kg released H ₂ ).

In one embodiment of the present invention, the amount of energy required to carry out step 2(a) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg of SiF ₄ produced).

In one embodiment of the present invention, the temperature during the procedure for producing SiF ₄ in step 2(a) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits, and preferably can be in the range from 0 to 1000°C.

In one embodiment of the present invention, the pressure during the procedure for producing SiF ₄ in step 2(a) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa.

In one embodiment of the present invention, step 2(a) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the hydrogen fluoride (HP)/silicate-based compound (B) mixture has a molar ratio greater than or equal to 1. B In one embodiment of the present invention, said mixture of HF and silicate-based compound (B) has a molar ratio of HF/(B) which is between 4 and 100.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 2(a) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 2(b) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 50 kWh/(kg of SiO produced).

In one embodiment of the present invention, the temperature during the procedure for producing SiO in step 2(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary widely, and preferably can be in the range from 1000 to 2000°C.

In one embodiment of the present invention, the pressure during the procedure for producing SiO in step 2(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa. More preferably, if the pressure is in the range from 100 to 10000 Pa.

In one embodiment of the present invention, step 2(b) of the process for preparing a siloxane hydrogen carrier of formula (I) is characterized in that the silicate-based compound (B)/Si mixture has a molar ratio greater than or equal to 0.1. In one embodiment of the present invention, said mixture of compound based on silicate (B) and Si is characterized by a molar ratio of compound (B)/Si, which is from 0.5 to 1.5. Preferably, the molar ratio of the silicate-based compound (B)/Si is 1.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 2(b) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 2(c) of the method for producing/regenerating the hydrogen siloxane carrier of formula (I) may be from 1 to 50 kWh/(kg Si produced).

In one embodiment of the present invention, the temperature during the procedure for producing Si in step 2(c) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary widely, and preferably can be in the range from 30 to 6000°C.

In one embodiment of the present invention, the pressure during carrying out the procedure for obtaining Si in step 2(c) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits, and preferably can be in the range from 1 to 1.10 Pa. More preferably, if the pressure is in the range from 10 to 10,000 Pa.

In one embodiment of the present invention, step 2(c) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the H ₂ gas/silicate-based compound (B) mixture has a molar ratio greater than or equal to 0.1. In one embodiment of the present invention, said mixture of gaseous H ₂ and silicate-based compound (B) has a molar ratio of gaseous H ₂ /compound (B) which is from 2 to 100. Preferably, if it is from 2 to 20.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 2(c) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 3(a) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg H ₂ SiF ₂ produced).

In one embodiment of the present invention, the temperature during the procedure for producing H ₂ SiF ₂ in step 3(a) of the method for producing/regenerating the hydrogen siloxane carrier of formula (I) can vary within wide limits, and preferably can be in the range from 1000 to 2000°C.

In one embodiment of the present invention, the pressure during the procedure for producing H ₂ SiF ₂ in step 3(a) of the method for producing/regenerating a hydrogen siloxane carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa.

In one embodiment of the present invention, step 3(a) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the hydrogen gas (H ₂ )/SiF ₄ mixture has a molar ratio greater than or equal to 1. In one embodiment of the present of the invention, said mixture of H ₂ and SiF ₄ is characterized by a molar ratio of H ₂ /SiF ₄ , which ranges from 1 to 100.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 3(a) of the process for producing/regenerating the hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 3(a') of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg Si produced).

In one embodiment of the present invention, the temperature during the procedure for producing Si in step 3(a') of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits, and preferably can be in the range from 30 to 6000°C.

In one embodiment of the present invention, the pressure during the Si production procedure in step 3(a') of the production/regeneration process of the hydrogen siloxane carrier of formula (I) can vary within wide limits, and preferably can range from 1 to 1.10 ⁷ Pa.

In one embodiment of the present invention, step 3(a') of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the hydrogen gas (H ₂ )/SiF ₄ mixture has a molar ratio greater than or equal to 2. In one embodiment, of the present invention, said mixture of H ₂ and SiF ₄ is characterized by a molar ratio of H ₂ /SiF ₄ , which is from 2 to 100.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 3(a) of the process for producing/regenerating the hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 3(b) of the process for producing/regenerating the hydrogen siloxane carrier of formula (I) may be from 1 to 50 kWh/(kg Si produced).

In one embodiment of the present invention, the temperature during the procedure for producing Si in step 3(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary widely, and preferably can be in the range from 100 to 1000°C.

In one embodiment of the present invention, the pressure during carrying out the procedure for obtaining Si in step 3(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa.

In one embodiment of the present invention, step 3(b) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the sodium (Na)/SiF ₄ mixture has a molar ratio greater than or equal to 1. In one embodiment of the present invention, said the mixture of Na and SiF ₄ is characterized by a Na/SiF ₄ molar ratio ranging from 4 to 100.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 3(b) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 3(c) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 50 kWh/(kg Si produced).

In one embodiment of the present invention, the temperature during the procedure for producing Si in step 3(c) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary widely, and preferably can be in the range from 500 to 2000°C.

In one embodiment of the present invention, the pressure during carrying out the procedure for obtaining Si in step 3(c) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa.

In one embodiment of the present invention, step 3(c) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the hydrogen gas (H ₂ )/SiO mixture has a molar ratio greater than or equal to 1. In one embodiment of the present invention said mixture of H ₂ and SiO has an H ₂ /SiO molar ratio of 5 to 10. In one embodiment of the present invention, said mixture of H ₂ and SiO has an H ₂ /SiO molar ratio of 6.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 3(c) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 4 of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg [H ₂ SiCl ₂ ] produced).

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 4 of the process for producing/regenerating the hydrogen siloxane carrier of formula (I) may be from 1 to 20.

The controlled hydrolysis of halosilanes carried out in step 5 according to the present invention can be well illustrated by step 5(a) or step 5(b) shown in FIG. 2.

In one embodiment of the present invention, the amount of energy required to carry out step 5(a) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg [H ₂ SiO] produced).

In one embodiment of the present invention, the temperature during the procedure for producing [H ₂ SiO] in step 5(a) of the method for producing/regenerating the hydrogen siloxane carrier of formula (I) can vary within wide limits, and preferably can be in the range from -50 to 100° C.

In one embodiment of the present invention, the pressure during the procedure for producing [H ₂ SiO] in step 5(a) of the method for producing/regenerating a hydrogen siloxane carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa .

In one embodiment of the present invention, step 5(a) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the water (H ₂ O)/H ₂ SiCl ₂ mixture has a molar ratio greater than or equal to 0.1. In one embodiment of the present invention, said mixture of H ₂ O and H ₂ SiCl ₂ is characterized by a molar ratio of H ₂ O/H ₂ SiCl ₂ , which is from 0.1 to 10,000.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 5(a) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

In one embodiment of the present invention, the amount of energy required to carry out step 5(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) may be from 1 to 50 kWh/(kg [H ₂ SiO] produced).

In one embodiment of the present invention, the temperature during the procedure for producing [H ₂ SiO] in step 5(b) of the method for producing/regenerating a hydrogen siloxane carrier of formula (I) can vary within wide limits, and preferably can be in the range from -50 to 100° C.

In one embodiment of the present invention, the pressure during the procedure for producing [H ₂ SiO] in step 5(b) of the method for producing/regenerating a siloxane hydrogen carrier of formula (I) can vary within wide limits and preferably can be in the range from 1 to 1.10 ⁷ Pa .

In one embodiment of the present invention, step 5(b) of the process for producing/regenerating a siloxane hydrogen carrier of formula (I) is characterized in that the water (H ₂ O)/H ₂ SiF ₂ mixture has a molar ratio greater than or equal to 0.1. In one embodiment of the present invention, said mixture of H ₂ O and H ₂ SiF ₂ is characterized by a molar ratio of H ₂ O/H ₂ SiF ₂ , which is from 0.1 to 10,000.

In one embodiment of the present invention, the number of separate operations (e.g., reaction, separation, purification, etc.) required in step 5(b) of the process for producing/regenerating a hydrogen siloxane carrier of formula (I) may be from 1 to 10.

The following terms and expressions included in the present invention are defined as follows:

Hydrogen carriers are solid or liquid materials which contain hydrogen atoms which, if necessary, are readily released as molecular dihydrogen (H ₂ ).

It should be apparent to those skilled in the art that the present invention allows numerous other specific forms of embodiments without deviating from the scope of the claimed invention. Accordingly, the embodiments of the present invention are to be considered as illustrative, however, they may be modified within the scope of the appended claims, and the present invention should not be limited to the above detailed descriptions.

Examples

Liquid PGS (poly(dihydrosiloxane)) was obtained by controlled hydrolysis of dichlorosilane (H ₂ SiCl ₂ ) and was obtained as a colorless liquid. Solid PGS was obtained by controlled hydrolysis of dichlorosilane (H ₂ SiCl ₂ ) in the presence of trimethylsilyl chloride (Me ₃ Si-Cl) used as a chain terminator and was obtained as colorless crystals. PGMS (poly(hydromethylsiloxane)) was obtained from commercial sources as a colorless liquid.

In FIG. 6 shows the results of hydrogen evolution experiments in which the volume of hydrogen gas evolved over time was determined using three different siloxane hydrogen carriers. The results are shown in the table below.

All three reactions proceeded in quantitative yield. Due to the chemical structure of each compound, the liquid poly(dihydrosiloxane) having a cyclic structure provided a significantly larger volume of hydrogen gas released. Solid poly(dihydrosiloxane), having a linear structure, had a lower efficiency due to the presence in its chain containing carbon end fragments -SiMe ₃ , which lead to a lower mass efficiency in the production of hydrogen. PGMS had an efficiency more than 2 times lower than liquid PGS, since it contains only one hydride hydrogen atom in each hydromethylsiloxane repeating unit.

Description of the experimental setup

A 60 ml PET (polyethylene terephthalate) preform was connected (by screwing) to a sealed ball-lock adapter containing a hydrogen outlet nozzle and an internal thread to which a stainless steel needle was screwed, equipped with a stainless steel valve, designed to supply reagents . An outlet nozzle for hydrogen gas was connected to a flowmeter to study the kinetics of hydrogen evolution. Hydrogen gas was collected in an inverted 2 L graduated graduated cylinder filled with water as an additional volume measurement. The flow of hydrogen gas released into the graduated cylinder was controlled by a needle valve.

Example 1

1.007 g (16.75 mmol, 1.0 eq.) of poly(hydromethylsiloxane) was placed in a 60 ml PET preform, and 2 ml of NaOH (20 wt.% in water) (12.2 mmol, 0.73 eq.). The valve was closed and 400 ml (>99% yield) of hydrogen gas was collected in a graduated cylinder over 20 seconds.

Example 2

1.003 g (21.75 mmol, 1.0 eq.) of linear solid poly(dihydrosiloxane) was placed in a 60 ml PET preform, and 5 ml of NaOH was rapidly added to the reaction medium with vigorous stirring using a 5 ml syringe through an injection needle. (20 wt% in water) (30.5 mmol, 1.40 eq.). The valve was closed and 750 ml (>99% yield) of hydrogen gas was collected in a graduated cylinder over 95 seconds.

Example 3

1.005 g (21.80 mmol, 1.0 eq.) of cyclic liquid poly(dihydrosiloxane) was placed in a 60 ml PET preform, and 5 ml of NaOH was rapidly added to the reaction medium with vigorous stirring using a 5 ml syringe through an injection needle. (20 wt% in water) (30.5 mmol, 1.40 eq.). The valve was closed and 1040 ml (>99% yield) of hydrogen gas was collected in a graduated cylinder over 50 seconds.

Claims (34)

1. A method for producing a liquid siloxane hydrogen carrier compound, comprising X, Y, or Z reaction paths, comprising the following steps: obtaining a silica-based compound and/or a silicate-based compound, and - in the case of reaction route X, carrying out the step of halogenating the silica-based compound and/or the silicate-based compound to obtain silicon tetrahalide; carrying out a step of reducing silicon tetrahalide to obtain a halosilane, and carrying out a step of hydrolyzing the halosilane to obtain a liquid siloxane hydrogen carrier compound; - in the case of reaction route Y, carrying out the step of reducing the silica-based compound and/or the silicate-based compound to obtain silicon to obtain silicon; carrying out a step of hydrohalogenating silicon to obtain a halosilane, and carrying out a step of hydrolyzing the halosilane to obtain a liquid siloxane hydrogen carrier compound; - in the case of reaction route Z, carrying out the step of halogenating the silica-based compound and/or the silicate-based compound to obtain silicon tetrahalide; carrying out the stage of reduction of silicon tetrahalide to obtain silicon; carrying out a step of hydrohalogenating silicon to obtain a halosilane; and carrying out a step of hydrolyzing the halosilane to obtain a liquid siloxane hydrogen carrier compound. 2. A method for regenerating a liquid siloxane hydrogen carrier compound, wherein the liquid siloxane hydrogen carrier compound is subjected to hydrolytic oxidation to produce hydrogen and a silica and/or silicate-based compound (B), followed by reacting along the route X, Y or Z according to claim 1 to obtain a liquid siloxane hydrogen carrier compound. 3. The method for regenerating the liquid hydrogen carrier siloxane compound according to claim 2, wherein the regenerated hydrogen carrier siloxane compound is chemically identical to the hydrogen carrier siloxane compound subjected to hydrolytic oxidation. 4. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of paragraphs. 1-3, in which the siloxane hydrogen carrier compound does not contain carbon. 5. A process for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 4, wherein the reagents used in the process do not contain carbon. 6. A process for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein hydrogen halide is used to halogenate the silica and/or silicate based compound in reaction paths X and Z to produce silicon tetrahalide. 7. The method for producing or regenerating the liquid siloxane hydrogen carrier compound according to claim 6, wherein the hydrogen halide is hydrogen fluoride and the silicon tetrahalide is silicon tetrafluoride. 8. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein the reduction of the silica-based compound and/or the silicate-based compound in the Y reaction path is a one-step reduction in the presence of hydrogen to produce silicon; or a two-step reduction comprising reducing the silica-based compound and/or the silicate-based compound in the presence of silicon to produce SiO, and reducing the SiO in the presence of hydrogen to produce silicon. 9. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 8, wherein the reduction of the silica-based compound and/or the silicate-based compound in the Y reaction path is a one-step reduction in the presence of hydrogen to produce silicon, which is carried out in plasma environment without carbon emissions. 10. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein the reduction of silicon tetrahalide in the Z reaction path is reduction in the presence of hydrogen to produce silicon; or reduction in the presence of a metal reducing agent to obtain silicon. 11. A process for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein hydrogen is used to reduce silicon tetrahalide in the reaction route X and halosilane is produced. 12. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 11, wherein the silicon tetrahalide is silicon tetrafluoride and the halosilane is difluorosilane (H ₂ SiF ₂ ). 13. A process for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein hydrogen halide is used to hydrohalogenate silicon in the Y and Z reaction pathways to produce halosilane. 14. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 13, wherein the hydrogen halide is hydrogen chloride and the halosilane is dichlorosilane (H ₂ SiCl ₂ ). 15. The process for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein water is used to hydrolyze the halosilane in reaction paths X, Y, and Z to obtain a liquid siloxane hydrogen carrier compound. 16. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of the preceding claims, wherein the liquid siloxane hydrogen carrier compound contains one or more units of formula (I):

where n is an integer greater than or equal to 1. 17. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 16, wherein the liquid siloxane hydrogen carrier compound is a linear compound of the formula ROH _2n Si _n O _n R', wherein n is an integer greater than or equal to 1, R and R' are selected from the following: Me, Et, Pr, iPr, Bu, tBu, Ph and/or SiR'' 3, where R" is selected from the following: H, Me, Et, Pr, iPr, Bu, tBu and/or Ph. 18. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 17, wherein n is greater than or equal to 2, such as greater than or equal to 3, or even greater than or equal to 4; n is less than or equal to 500, such as less than or equal to 50. 19. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any one of paragraphs. 17 and 18, in which R and R' do not contain carbon. 20. The process for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 19, wherein R and R' are SiH ₃ . 21. The method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 16, wherein the liquid siloxane hydrogen carrier compound of formula (I) is a cyclic compound, for example, a cyclic compound of the formula H _2n Si _n O _n , wherein n is an integer a number greater than or equal to 2, such as greater than or equal to 3 or even greater than or equal to 4. 22. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to claim 21, wherein n is less than or equal to 500, such as less than or equal to 32, such as less than or equal to 17. 23. A method for producing or regenerating a liquid siloxane hydrogen carrier compound according to any of the preceding claims, carried out without the need for a carbon-containing reagent and / or without carbon emissions, if the siloxane hydrogen carrier compound does not contain carbon, and / or carbon emissions are less than 0.924 kg CO2 in terms of 1 kg of the obtained siloxane hydrogen carrier compound, if the siloxane hydrogen carrier compound contains carbon. 24. The method for producing or regenerating the liquid siloxane hydrogen carrier compound according to claim 23, wherein the carbon emissions are less than 0.462 kg CO ₂ , more preferably less than 0.231 kg CO ₂ , for example, less than 0.1 kg _CO 2 or even less than 0.05 kg CO ₂ in terms of 1 kg produced/regenerated siloxane hydrogen carrier compound, if the siloxane hydrogen carrier compounds contain carbon. 25. Liquid siloxane connection-carrier of hydrogen obtained by the method of production or regeneration according to any one of paragraphs. 19-24. 26. A method for producing hydrogen by hydrolytic oxidation of a liquid siloxane hydrogen carrier compound according to claim 25 in the presence of water. 27. The use of a liquid siloxane hydrogen carrier compound according to claim 25 for storing and transporting hydrogen and/or energy. 28. The use of a liquid siloxane hydrogen carrier compound according to claim 27, wherein said hydrogen is produced in a renewable energy production process and/or where said energy is produced in a renewable energy production process, off-peak electricity generation and/or a waste gas heat recovery process. 29. Flowing in the absence of carbon, the use of a liquid siloxane hydrogen carrier compound according to any one of paragraphs. 27 and 28 in the carbon-free process of claim 26 to release hydrogen on demand.

Images