HYDROGEN CARRIER COMPOUNDS

Abstract

The present invention relates to siloxane hydrogen carrier compounds and to a method for producing hydrogen from said siloxane hydrogen carrier compounds.

Claims

1. A liquid siloxane hydrogen carrier compound exhibiting a cyclic chemical structure and comprising one or more units of formula (I): ##STR00008## wherein n is an integer representing the number of repeating units with n being superior or equal to 2.

2. (canceled)

3. The liquid cyclic siloxane hydrogen carrier compound according to claim 1 wherein n is an integer superior or equal to 3 and inferior or equal to 500.

4. The liquid cyclic siloxane hydrogen carrier compound according to claim 1 wherein n is an integer superior or equal to 4 and inferior or equal to 32.

5. The liquid cyclic siloxane hydrogen carrier compound according to claim 1 selected amongst Tri(bis(hydro)cyclosiloxane), Tetra(bis(hydro)cyclosiloxane), Penta(bis(hydro)cyclosiloxane), Hexa(bis(hydro)cyclosiloxane), Hepta(bis(hydro)cyclosiloxane), Octa(bis(hydro)cyclosiloxane), Nona(bis(hydro)cyclosiloxane), Deca(bis(hydro)cyclosiloxane), Undeca(bis(hydro)cyclosiloxane), Duodeca(bis(hydro)cyclosiloxane), Trideca(bis(hydro)cyclosiloxane), Tetradeca(bis(hydro)cyclosiloxane), Pendeca(bis(hydro)cyclosiloxane), Hexadeca(bis(hydro)cyclosiloxane), Heptadeca(bis(hydro)cyclosiloxane), and/or or mixture of two or more thereof.

6. The liquid cyclic siloxane hydrogen carrier compound according to claim 1, wherein the liquid siloxane hydrogen carrier compound has a dynamic viscosity between 0.1 and 10000 mPa.Math.s at a temperature of 20° C. and a pressure of 1.01325×10.sup.5 Pa.

7. The liquid cyclic siloxane hydrogen carrier compound according to claim 6 wherein the liquid siloxane hydrogen carrier compound has a dynamic viscosity between 0.2 and 50 mPa.Math.s.

8. The liquid cyclic siloxane hydrogen carrier compound according to claim 1 wherein the liquid siloxane hydrogen carrier compound has a molecular weight from 130 to 800 g/mol.

9. The liquid cyclic siloxane hydrogen carrier compound according to claim 1, wherein the siloxane hydrogen carrier compounds present a refractive index between 1 and 2 at a temperature of 20° C. and at a wavelength of 589 nm.

10. A mixture of a liquid cyclic siloxane hydrogen carrier compound according to claim 1 together with a liquid siloxane hydrogen carrier compound exhibiting a linear chemical structure and comprising one or more units of formula (I): ##STR00009## wherein n is an integer representing the number of repeating units.

11. A method for the production of hydrogen by hydrolytic oxidation of a siloxane hydrogen carrier compound according to claim 1 in the presence of water.

12. A method for the production of hydrogen by hydrolytic oxidation of a siloxane hydrogen carrier compound according to claim 1 in the presence of water wherein the water/[SiOH.sub.2] unit molar ratio is superior or equal to 0.1.

13. A method for the production of hydrogen by hydrolytic oxidation of a siloxane hydrogen carrier compound according to claim 1 in the presence of water and in the presence of at least one hydrogen release initiator, wherein the hydrogen release initiator/[SiOH.sub.2] unit molar ratio is superior to 0.01.

14. A method for the production of a liquid siloxane hydrogen carrier compound according to claim 1 from reaction routes X, Y, or Z comprising the following steps: providing silica compound and/or silicate compound and for reaction route X, subjecting the silica compound and/or silicate compound to a halogenation step to produce silicon tetrahalide, subjecting the silicon tetrahalide to a reduction step to produce halosilane, and subjecting the halosilane to a hydrolysis step to produce a liquid siloxane hydrogen carrier compound; for reaction route Y, subjecting the silica compound and/or silicate compound to a reduction step to produce silicon, subjecting silicon to a hydrohalogenation step to produce halosilane, and subjecting the halosilane to a hydrolysis step to produce a liquid siloxane hydrogen carrier compound; for reaction route Z, subjecting the silica compound and/or silicate compound to a halogenation step to produce silicon tetrahalide, subjecting the silicon tetrahalide to a reduction step to produce silicon, subjecting silicon to a hydrohalogenation step to produce halosilane, and subjecting the halosilane to a hydrolysis step to produce a liquid siloxane hydrogen carrier compound.

15. A method for the regeneration of a liquid siloxane hydrogen carrier compound wherein a liquid siloxane hydrogen carrier compound according to claim 1 is subjected to hydrolytic oxidation for the production of hydrogen and silica and/or silicate compound (B) followed by reaction routes X, Y, or Z according to claim 14 to produce a liquid siloxane hydrogen carrier compound.

16. The method for the regeneration of a liquid siloxane hydrogen carrier compound according to claim 15 wherein the regenerated siloxane hydrogen carrier compound is chemically identical to the siloxane hydrogen carrier compound subjected to hydrolytic oxidation.

17. The method for the production of a liquid siloxane hydrogen carrier compound according to claim 14 wherein process reactants don't contain carbon.

18. A use of the liquid siloxane hydrogen carrier compound according to claim 1 for the storage and transport of hydrogen and/or energy.

19. The use of the liquid siloxane hydrogen carrier compound according to claim 18 wherein said hydrogen comes from a renewable energy production process and/or when said energy originates from renewable energy production process, off-peak electricity production, and/or waste heat recovery process.

20. A carbon-free use of the liquid siloxane hydrogen carrier compound according to claim 18 in a carbon-free method according to claim 11 for the on-demand release of hydrogen.

21. A mixture of two or more of any of the liquid siloxane hydrogen carrier compounds according to claim 5.

22. The method for the regeneration of a liquid siloxane hydrogen carrier compound according to claim 15 wherein process reactants don't contain carbon.

Description

EXAMPLES

[0276] Liquid PHS (poly(dihydrosiloxane)) was prepared by controlled hydrolysis of dichlorosilane (H.sub.2SiCl.sub.2) and obtained as a colorless liquid. Solid PHS was prepared by controlled hydrolysis of dichlorosilane (H.sub.2SiCl.sub.2) in the presence of trimethylsilyl chloride (Me.sub.3Si—Cl) as chain terminating agent and obtained as colorless crystals. PHMS (poly(hydromethylsiloxane)) was obtained as a colorless liquid from commercial sources.

[0277] FIG. 6 depicts hydrogen release experiments, with recording of the liberated volume of hydrogen gas over time, from three different siloxane hydrogen carriers. The following table summarizes the results.

TABLE-US-00001 Hydrogen Release Volume H.sub.2 Example carrier time (s) released (mL) 1 PHMS 20 400 2 Linear 95 750 solid PHS 3 Cyclic 50 1040 liquid PHS

[0278] All three reactions exhibit a quantitative yield. As a consequence of the chemical structure of each compound, the liquid poly(dihydrosiloxane) bearing a cyclic structure exhibits by far the highest volume of liberated hydrogen gas. Solid poly(dihydrosiloxane) presenting a linear structure demonstrates lower performances due to its carbon containing —SiMe.sub.3 chain terminations lowering its hydrogen weight gravimetric efficiency. PHMS shows more than a two-fold lower performance when compared to liquid PHS since it carries only one hydride per hydromethylsiloxane repeating unit.

[0279] Description of the Experimental Set-Up

[0280] A 60 mL PET preform was connected (by screwing) to a pressure tight ball lock coupler featuring an outlet nozzle for hydrogen gas evacuation and a female thread to which a stainless needle, equipped with a stainless stopcock, was crimped for reactants injection. The hydrogen gas outlet nozzle was connected to a flowmeter in order to monitor the kinetic of the hydrogen release. The hydrogen gas was collected in an inverted 2 L graduated measuring cylinder filled with water used as an additional volume measuring device. The flow of hydrogen gas released into the measuring cylinder was controlled by a needle valve.

Example 1

[0281] In a 60 mL PET preform was charged 1.007 g (16.75 mmol, 1.0 equiv.) of poly(hydromethylsiloxane) and 2 mL of NaOH (20 wt % in water) (12.2 mmol, 0.73 equiv.) was quickly added with a 5 mL syringe via the injection needle onto the reacting medium under vigorous stirring. The stopcock was closed and 400 mL (>99% yield) of hydrogen gas were collected in the measuring cylinder over a period of 20 seconds.

Example 2

[0282] In a 60 mL PET preform was charged 1.003 g (21.75 mmol, 1.0 equiv.) of linear solid poly(dihydrosiloxane) and 5 mL of NaOH (20 wt % in water) (30.5 mmol, 1.40 equiv.) was quickly added with a 5 mL syringe via the injection needle onto the reacting medium under vigorous stirring. The stopcock was closed and 750 mL (>99% yield) of hydrogen gas were collected in the measuring cylinder over a period of 95 seconds.

Example 3

[0283] In a 60 mL PET preform was charged 1.005 g (21.80 mmol, 1.0 equiv.) of cyclic liquid poly(dihydrosiloxane) and 5 mL of NaOH (20 wt % in water) (30.5 mmol, 1.40 equiv.) was quickly added with a 5 mL syringe via the injection needle onto the reacting medium under vigorous stirring. The stopcock was closed and 1040 mL (>99% yield) of hydrogen gas were collected in the measuring cylinder over a period of 50 seconds.