PROCESS FOR PRODUCING AND REGENERATING HYDROGEN CARRIER COMPOUNDS

Abstract

The present invention relates to a process for producing and for regenerating siloxane hydrogen carrier compounds.

Claims

1. Process for the production of a liquid siloxane hydrogen carrier compound consisting in reaction routes X, Y, or Z comprising the following consecutive 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.

2. Process for the regeneration of a liquid siloxane hydrogen carrier compound wherein a liquid siloxane hydrogen carrier compound 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 1 to produce a liquid siloxane hydrogen carrier compound.

3. Process for the regeneration of a liquid siloxane hydrogen carrier compound according to claim 2 wherein the regenerated siloxane hydrogen carrier compound is chemically identical to the siloxane hydrogen carrier compound subjected to hydrolytic oxidation.

4. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims without requiring carbon containing reactant and/or without carbon emissions when the siloxane hydrogen carrier compound is carbon free and/or with carbon emissions lower than 0.924 kg of CO2 per kg of produced siloxane hydrogen carrier compound when the siloxane hydrogen carrier compound contains carbon.

5. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 4 wherein the carbon emissions are lower than 0.462 kg of CO.sub.2, more preferably lower than 0.231 kg of CO.sub.2, for example less than 0.1 kg of CO.sub.2 or even less than 0.05 kg of CO.sub.2 per kg of produced/regenerated siloxane hydrogen carrier compound when the siloxane hydrogen carrier compounds contain carbon.

6. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of claims 1 to 4 wherein the siloxane hydrogen carrier compound does not contain carbon.

7. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 6 wherein process reactants don't contain carbon.

8. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein hydrogen halide is used for the halogenation of the silica and/or silicate compound of reaction routes X and Z to produce silicon tetrahalide.

9. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 8 wherein the hydrogen halide is hydrogen fluoride and the silicon tetrahalide is silicon tetrafluoride.

10. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein the reduction of the silica compound and/or silicate compound of reaction route Y is a one-step reduction in the presence of hydrogen to produce silicon; or a two-step reduction comprising the reduction of the silica compound and/or silicate compound in the presence of silicon to produce SiO and the reduction of the SiO in the presence of hydrogen to produce silicon.

11. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 10 wherein the reduction of the silica compound and/or silicate compound of reaction route Y is the one-step reduction in the presence of hydrogen to produce silicon which is performed in a plasma without carbon emissions.

12. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein the reduction of the silicon tetrahalide of reaction route Z is a reduction in the presence of hydrogen to produce silicon; or a reduction in the presence of a metallic reductant to produce silicon.

13. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein hydrogen is used for the reduction of the silicon tetrahalide of reaction route X to produce halosilane.

14. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 13 wherein the silicon tetrahalide is silicon tetrafluoride and the halosilane is difluorosilane (H.sub.2SiF.sub.2).

15. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein hydrogen halide is used for the hydrohalogenation of silicon of reaction routes Y and Z to produce halosilane.

16. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 15 wherein the hydrogen halide is hydrogen chloride and the halosilane is dichlorosilane (H.sub.2SiCl.sub.2).

17. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein water is used for the hydrolysis of the halosilane of reaction routes X, Y and Z to produce a liquid siloxane hydrogen carrier compound.

18. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of the preceding claims wherein the liquid siloxane hydrogen carrier compound has one or more units of formula (I): ##STR00005## wherein n is an integer which is superior or equal to one.

19. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 18 wherein the liquid siloxane hydrogen carrier compound is a linear compound of formula ROH.sub.2nSi.sub.nO.sub.nR with n being an integer superior or equal to 1, R and R are selected amongst Me, Et, Pr, .sup.iPr, Bu, .sup.tBu, Ph and/or SiR.sub.3 with R being selected amongst H, Me, Et, Pr, .sup.iPr, Bu, .sup.tBu, and/or Ph.

20. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 19 wherein n is superior or equal to 2, for example superior or equal to 3, or even superior or equal to four; n is inferior or equal to 500, for example inferior or equal to 50.

21. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to any of claims 19 and 20 wherein R and R don't contain carbon.

22. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 21 wherein R and R are SiH.sub.3.

23. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 18 wherein the liquid siloxane hydrogen carrier compound of formula (I) is a cyclic compound, for example a cyclic compound of formula H.sub.2Si.sub.nO.sub.n with n being an integer superior or equal to 2, for example superior or equal to 3, or even superior or equal to four.

24. Process for the production or regeneration of a liquid siloxane hydrogen carrier compound according to claim 23 wherein n is inferior or equal to 500, for example inferior or equal to 32, for example inferior or equal to 17.

25. Liquid siloxane hydrogen carrier compound obtained by production or regeneration process according to any of the preceding claims.

26. Method for the production of hydrogen by hydrolytic oxidation in the presence of water of the liquid siloxane hydrogen carrier compound siloxanes of claim 25.

27. Use of the liquid siloxane hydrogen carrier compound according to claim 25 for the storage and transport of hydrogen and/or energy.

28. Use of the liquid siloxane hydrogen carrier compound according to claim 27 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.

29. Carbon-free use of the liquid siloxane hydrogen carrier compound according to any of claims 27 and 28 in a carbon-free method according to claim 26 for the on-demand release of hydrogen.

Description

EXAMPLES

[0247] Liquid PHS (poly(dihydrosiloxane)) was prepared by controlled hydrolysis of dichlorosilane (H.sub.2SiC.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.3SiCl) as chain tenninating agent and obtained as colorless crystals. PHMS (poly(hydromethylsiloxane)) was obtained as a colorless liquid from commercial sources.

[0248] 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

[0249] 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.

[0250] Description of the Experimental Set-Up

[0251] 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.

[0252] 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

[0253] 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

[0254] 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

[0255] 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.