Porous composite material and its use for gas storage

Abstract

This application relates to the storage of gases using a porous composite material based on a porous matrix and an organic compound confined in solid form within the pores of the matrix having a diameter of less than 10 nm.

Description

Technical Field

[0001] The present disclosure relates to the field of energy storage, particularly to the storage of gases such as dihydrogen (H2).

Background Art

[0002] Hydrogen is at the core of the future environmental transition and is expected to be one of the future fuels. Political leaders and major energy-related companies have taken a strong stance in this regard. For the large-scale development of this form of energy, the means for storing H2 in the hydrogen energy chain is a major obstacle.

[0003] There are various types of hydrogen storage, such as conventional tanks (in gas or liquid form) and solid forms (adsorption, absorption, or capture forms), etc. Currently, none of these technologies provide sufficient satisfaction for fixed or mobile storage, regardless of reasons such as insufficient performance, safety, social acceptability, or profitability.

[0004] Currently, storage in solid form is obtained either by adsorption into a porous matrix (however, it has been found that the storage capacity is only favorable at very low temperatures, particularly cryogenic temperatures (77K)), or by absorption into metals or complex hydrides. Some of these have favorable storage volume densities (higher than that of liquid hydrogen), but even when the associated pressure is moderate, the use of these types of materials faces two major drawbacks: the reaction rates of hydride formation and dehydrogenation are slow, and the dehydrogenation temperatures are high (above 300°C and above 480°C for MgH2 and LiBH4, respectively).

[0005] FR3000907 describes a reaction medium comprising a porous substrate on which an organic compound in solid form capable of forming a gas clathrate is deposited, the porous substrate having pores sized from 10 nm to 150 nm, preferably from 30 nm to 120 nm. After impregnation via a liquid process, the organic compound in solid form is deposited on the surface of the substrate and / or within the pores of the substrate. The gas can be trapped by the organic compound in the form of a clathrate.

[0006] This technique has the drawback of using solvents that require the steps of dissolution, filtration and drying.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, there is still a need to provide a technique for storing dihydrogen that has a desired storage capacity and enables the storage and release of gas under less demanding conditions.

Means for Solving the Problems

[0009] These objects are particularly achieved by the present invention.

[0010] Therefore, the present invention relates to a porous composite material for storing a gas, comprising: - a porous matrix having pores with a diameter of less than 10 nm, and - an organic compound wherein the organic compound is contained within the pores having a diameter of less than 10 nm.

[0011] In the context of the present invention, the term "composite material" means a system composed of at least two materials, namely a porous matrix and an organic compound.

[0012] The term "porous matrix" means a solid material having pores in which an organic compound can be deposited.

[0013] The porous matrix suitable for the present invention is one that can be used, in particular, in industrial processes for the storage and use of stored gases, and one that does not deteriorate under the temperature and / or pressure conditions applied to these processes.

[0014] Advantageously, the porous matrix is selected from organic or inorganic micro- and / or mesoporous substrates, in particular those capable of forming inclusion compounds, more specifically silica, carbon, alumina, aluminosilicate, activated carbon, molecular sieves, zeolites, metal-organic frameworks (MOF), Hofmann clathrates, and polymers.

[0015] "Inclusion compound" means a supramolecular structure in which one of the components (host molecule) forms a cavity in which the molecular entity of the second chemical species (guest molecule) is stabilized. This concept includes solids (crystalline or amorphous) having a network with intervals (in the form of tunnels and channels of various shapes) capable of confining the included species. The stabilization of guest molecules within the network formed by the host molecule is generally ensured by non-covalent bonds, such as van der Waals forces. When the intervals formed within the host network are surrounded on all sides so that the included species are "trapped" like in a cage, the inclusion compound can be called a "clathrate" or "cage compound". The concept of inclusion compound as defined also includes "inclusion complex"-type structures where the relevant interactions for stabilizing guest molecules within the host network can be stronger than van der Waals bonds (e.g., hydrogen bonds).

[0016] Preferably, the porous matrix can be selected from mesoporous silica MCM-41 and SBA-15, aluminosilicate, carbon xerogel, activated carbon, and porous polymer.

[0017] According to the IUPAC nomenclature, "mesoporous" refers to pores with diameters from 2 to 50 nm, and "microporous" refers to pores with diameters less than 2 nm.

[0018] The pore size can be measured by gas porosimetry using nitrogen or argon as probe molecules. In this technique, the adsorption isotherm of the probe molecule is measured at extremely low temperatures (generally 77 K for nitrogen and 87 K for argon) under pressures ranging from 10 -7 bar to 1 bar. To infer the pore volume and pore size distribution of the porous matrix from these isotherms, a thermodynamic model, preferably the density functional theory (DFT), is used.

[0019] In one embodiment, the matrix comprises a micro or mesopore volume, i.e., a volume defined by micropores and mesopores.

[0020] Thus, in one embodiment, the pores of the porous matrix with a diameter of less than 10 nm correspond to at least 30%, preferably at least 50%, of the micro / mesopore volume of the porous matrix. This percentage is determined experimentally by a combination of analyses performed by gas porosimetry (capable of characterizing pores with diameters less than 30 nm), mercury porosimetry (capable of characterizing pores with diameters from 30 nm to several hundred micrometers), and pycnometry (capable of evaluating the total pore volume).

[0021] Typically, particles of the porous matrix, such as beads, granules, pellets, or tissues, especially silica beads or pellets, or activated carbon granules, pellets, or tissues, are used. Preferably, microporous particles with characteristic sizes (diameter for spherical particles, cylinder height for pellets) ranging, for example, from 30 μm to 10 mm are selected.

[0022] In one embodiment, the porous matrix has a particularly high specific surface area of 200 m 2 / g to 3000 m 2 / g.

[0023] The organic compound is selected from among compounds capable of forming hydrogen bonds.

[0024] In one embodiment, the bonds may be qualified as "intermolecular" in that they are formed between an organic compound molecule and another molecule, typically between at least two molecules of the organic compound, or between a molecule of the organic compound and a molecule of the stored gas (e.g., hydrogen).

[0025] Accordingly, suitable organic compounds include one or more electronegative atoms having at least one lone pair (non-binding doublet), such as oxygen O, nitrogen N, fluorine F, chlorine Cl, bromine Br, iodine I.

[0026] In one embodiment, the organic compound may be selected particularly from polyphenols, polythiols, urea, thiourea, and calixarenes. In particular, the organic compound may be selected from the group formed by hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene, and combinations thereof.

[0027] Preferably, the organic compound is hydroquinone, urea, calix[4]arene.

[0028] In one embodiment, the organic compound is in a condensed form within the pores. In one embodiment, the organic compound may be in a crystalline, semi-crystalline, and / or amorphous form within the pores of the porous matrix.

[0029] In the present invention, the organic compound can be deposited in micropores, particularly pores having a diameter of less than 10 nm.

[0030] Preferably, the organic compound occupies most of the pores of the porous matrix, particularly the micropores and mesopores of the porous matrix. Thus, in one embodiment, the organic compound occupies at least 25%, preferably at least 40% of the micro- and mesoporous volume of the porous matrix.

[0031] In one embodiment, the organic compound may occupy the entire porous volume of the porous matrix.

[0032] The volume percentage of pores occupied by the organic compound can be determined by gas porosimetry.

[0033] A further subject of the present invention is a method via a dry method for preparing the porous composite material of the present invention, which includes the adsorption / condensation of the organic compound in the pores of the porous matrix following the diffusion of organic vapor in the pores of the porous matrix.

[0034] The method of the present invention is carried out "via a dry method", that is, without a solvent.

[0035] The term "adsorption / condensation" refers to the change in the state of the organic compound throughout the method.

[0036] Without wishing to be bound by any theory, the physical mechanism of the incorporation of the organic compound results from adsorption, particularly including the formation of hydrogen or van der Waals type bonds, specifically physical adsorption, and further chemical adsorption, and simultaneously from the condensation of the gas phase, which is hereinafter referred to as adsorption / condensation.

[0037] In one embodiment, the condensation of the organic product occurs within the pores of the porous matrix.

[0038] More specifically, the organic compound in gaseous form condenses when adsorbed into the pores of the matrix.

[0039] Therefore, in the composite material of the present invention, the organic compound confined in the pores is in a condensed form.

[0040] Here, the organic compound can be referred to as "impregnated", "condensed" or "confined" without distinction, and refers to a homogeneous or heterogeneous solid and / or liquid state.

[0041] In one embodiment, the organic compound in gaseous form can be obtained from its solid form via sublimation.

[0042] Therefore, in one embodiment, the method also includes a prior sublimation step of the organic compound from the solid phase to the gas phase. This sublimation step can typically be carried out under reduced pressure and heating, for example under vacuum and at a temperature of 50 to 250 °C.

[0043] In one embodiment, the confinement of hydroquinone can be carried out by evacuating under vacuum, especially at a temperature of 80 to 170 °C for its sublimation, and then returning to room temperature.

[0044] Therefore, the organic compound sublimated into the gaseous state enters the pores of the porous matrix and is adsorbed therein in a condensed / condensed form.

[0045] Therefore, the organic compound can be confined in the pores without decomposition or degradation after condensation.

[0046] The present invention also relates to a porous composite material obtainable by the method described above.

[0047] In the present invention, the composite material thus obtained has a specific aspect including a condensed organic compound confined in pores of the porous matrix with a diameter of less than 10 nm.

[0048] The porous composite material described above enables gas storage. Therefore, a further subject of the present invention is a gas storage method, - contacting the porous composite of the present invention with a gas to be stored or a mixture containing said gas; - applying one or more continuous temperature cycles; relates to a method comprising.

[0049] Typically, storage is obtained through gas capture by organic compounds trapped within the mesopores or micropores of the matrix. Retention following gas capture is generally obtained using weak bonds of the van der Waals type, for example, built between the atoms of the organic compound and the hydrogen atoms of the gas.

[0050] As used herein, the expression "temperature cycle" should be understood as a continuous progression from a temperature T1 to a temperature T2 such that T1 < T2.

[0051] In one embodiment, T1 can be selected from temperatures of 77 K or higher, and in particular can be 0 °C.

[0052] In one embodiment, T2 can be selected from temperatures below the desorption temperature of the condensed organic compound, and in particular from temperatures within the region of 100 °C.

[0053] The pressure applied to these cycles can be, for example, from 1 to 200 bar, preferably from 5 to 150 bar, and advantageously from 20 to 120 bar.

[0054] One or more cycles can be applied continuously. The number of cycles can vary depending on the type of matrix and organic compound. Generally, when the amount of organic compound incorporated reaches a plateau, a sufficient number of cycles are applied. This amount can be determined by the measured amount of adsorbed gas, using techniques such as weight or volume measurements.

[0055] Advantageously, the composite of the present invention enables the storage of dihydrogen.

[0056] A further subject of the invention relates to a system composed of a composite material incorporating a storage gas obtainable by the method of the invention.

[0057] Accordingly, the invention also relates to a gas storage device comprising the porous composite material of the invention and a gas, wherein the gas is stored in pores containing an organic material.

[0058] Advantageously, the storage is stable under standard temperature and pressure conditions, for example 25 °C / 1 bar or 0 °C / 1 bar (NTP).

[0059] A further subject of the invention relates to the use of this device, which comprises removing the gas from storage at ambient pressure and a temperature of less than 150 °C.

[0060] The removal of the gas from storage is obtained by releasing the gas. This step is carried out at a temperature depending on the type of organic compound. Typically, the gas release is carried out at a temperature below the desorption temperature of the condensed organic compound.

[0061] Advantageously, in the case of hydrogen, the removal of dihydrogen from storage can be carried out at ambient pressure and a temperature of 150 °C or less, particularly less than 100 °C.

[0062] A further subject of the invention is the use of the porous composite material of the invention for storing a gas, particularly dihydrogen.

[0063] The storage of gas in the porous composite material of the invention has the advantage of being reversible. When the gas is removed from storage, the organic compound remains trapped in the pores and can be reused to capture the gas in the same manner as the previous capture reaction. In particular, the capture reaction of dihydrogen is reproducible in terms of the amount of gas captured. Accordingly, the composite material of the invention can be reused once the gas has been desorbed.

[0064] A further subject of the present invention relates to the use of the storage device of the present invention for the purpose of using the gas stored therein. Thus, in the present invention, the use includes the step of releasing the gas. Typically, the release from storage can be carried out at a temperature below the above-mentioned temperature T2. In the case of hydroquinone, the release from storage can be carried out at a temperature below 150 ° C, particularly below 100 ° C.

[0065] The present invention will be better understood by reading the following description which is shown by way of example only and referring to the accompanying drawings.

Brief Description of the Drawings

[0066]

Figure 1

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Figure 10

Mode for Carrying Out the Invention

[0067] [Examples] Preparation of Porous Composite Material The protocol is shown in Figure 1: 1 - Place 1 to 5 g of a solid organic compound (hydroquinone, HQ) into a flask above which another flask containing a porous matrix (200 to 1000 mg) to be impregnated, pre-purified under low vacuum at a temperature adapted according to the material (200 °C for carbon, 300 °C for silica, and 120 °C for polymer). 2 - Isolate the two flasks with a Durapore filter with a pore size of 0.45 μm. 3 - Place the assembly in a vacuum oven at 120 °C for a period of 1 to 64 hours so that the HQ sublimates and is adsorbed in crystalline, semi-crystalline and / or amorphous form within the pores of the matrix positioned above. Analyze the influence of the impregnation time. 4 - Then cool the system (controlled temperature gradient) and return to atmospheric pressure.

[0068] Impregnation results: The protocol was tested on the following carbon and silica micro / mesoporous adsorbents: 1: Tissue 2: G-Bac 3: F400 4: Porous polymer 5: MCM-41 6: SBA-15 7: Si-Al

[0069] Tissue (PICA woven activated carbon by PICY Company, Levallois, FRANCE), G-bac (by Kureha (registered trademark)), and F400 (Filtrasorb (registered trademark) 400 by Calgon Carbon Corporation) are carbon matrices. MCM-41, SBA-15, and Si-Al are silica matrices called by these names. The porous polymer is Optipore by Dow Chemicals (recently called Dupont). The organic product used is hydroquinone (purity > 99.5%, supplied by Acros Organics). The maximum impregnation rate is reached after several hours and is 12 to 38 mass% depending on the substrate. Figure 2A shows the results obtained for the different matrices 1 to 7 identified above.

[0070] Characterization by SEM, TGA / DSC analysis, and gas porosimetry showed that HQ was well impregnated in the pores (see Figure 2).

[0071] H2 Capture Test The H2 capture test was performed via a gravimetric technique using a magnetic suspension balance (Rubotherm).

[0072] The effects of temperature and pressure were analyzed. A thorough study of the hybrid MCM-41 / HQ material yielded the following results: - An initial temperature increase is required to "activate" the system, which is 80 °C for MCM-41. - Continuous temperature cycles (the example shown in Figure 3, i.e., for MCM-41 / HQ, from a minimum temperature of 0 °C to a maximum temperature of 100 °C) first enable the capture / release of H2 and then enable the attainment of the maximum capture rate after about 10 cycles. - The compound remains stable under ambient pressure for at least 48 hours. - For the MCM-41 / HQ system, the mass percentage of H2 obtained at atmospheric pressure and 25 °C (Figure 3) is about 1.2% per total mass of the impregnated material, i.e., 5.7% per mass of HQ.

[0073] Capture tests on very different porous matrices (polystyrene porous polymer, Optipore by Dow Chemicals) showed very similar results (Figure 4), which seems to indicate a wide variability of the nanoporous matrices that can be used (in terms of chemical species and pore size).

[0074] Comparison with existing solid H2 storage: The H2 capture rate obtained per mass of the composite (1.2%) or per mass of HQ (5.7%) is within the average for existing methods, referring to various existing solid storage classifications reported by Gupta et al., Energy Storage Materials, Volume 41, pages 69 - 107, October 2021.

[0075] Nevertheless, the system of the present invention has the significant advantage of operating at room temperature and moderate temperatures (1 bar, 25°C), with particularly lower cost and better stability compared to hydrides.

[0076] Comparative tests Tests were also conducted on porous particles of silica with a diameter of 200 to 500 microns, SiliaFlash SF300A (supplier Silicycle), the same particles as those used in the article by Coupan et al. (Chemical Engineering Journal 2017, 325, 35 - 48).

[0077] - Dry the SF300A particles at - 110°C for 24 hours (purification). Cool in a desiccator and then place in an oven at 35°C in a sealed container.

[0078] - Hydroquinone / ethanol impregnation solution: Place 7 g of hydroquinone in an Erlenmeyer flask. Adjust the total mass to 20 g with absolute ethanol. Seal the Erlenmeyer flask and place it under magnetic stirring, then heat in an oven at 35°C until the crystals are completely dissolved in the solvent (transparent solution).

[0079] - Place 3 grams of SF300A silica particles (kept at 35 °C) into a glass flask and cover with a sufficient amount of HQ / ethanol impregnation solution (35 °C) until all the particles are completely immersed. Shake the flask containing the silica particles and the impregnation solution by hand, seal it, and leave it standing in an oven at 35 °C for 24 hours.

[0080] - After a 24-hour contact time between the silica particles and the impregnation solution, filter the particles impregnated with the liquid on a Buchner filter connected to a vacuum flask, collect them with a crystallization device, and dry them in an oven at 35 °C for 24 hours.

[0081] The obtained SF300A / HQ composite material is in the form of a completely dry, uniform white powder (without black or gray particles, clusters, or plaques).

[0082] The impregnation rate of these composite materials measured by TGA is 32% by mass of HQ.

[0083] After drying, the composite material particles were sealed in a glass flask with a sealing plug in air at room temperature. They were stored in this flask until testing with a magnetic suspension balance.

[0084] The composite material was tested for hydrogen storage. It followed the same capture protocol, i.e., a temperature cycle from 0 to 100 °C at a pressure of 20 hydrogen bar. The results are shown in Figures 5 and 6, which show a comparison of the H2 capture cycles using MCM41+HQ that has an average pore size of 3 nm but a surface chemistry equivalent to that of SF300A.

[0085] In Figure 5, the amount of stored hydrogen per total mass of the sample (matrix + HQ) is plotted as a function of the number of cycles at 0 °C (for SF300A+HQ, the value is zero at 100 °C).

[0086] The storage amount of H2 in the MCM41+HQ sample is 10 times higher than that of SF300A after about 10 cycles.

[0087] In Figure 6, the storage amount is expressed per mass of HQ impregnated in the matrix. The storage amount is 7 times higher in MCM41+HQ.

[0088] These results indicate that when HQ is impregnated in pores of a micro size (less than 10 nm), the storage amount is much higher as a result of the confinement effect in pores of this size.

[0089] Impregnation and capture by calixarene By sublimation of CX4 at 300 °C for 72 hours under high vacuum, impregnation of the porous substrate MCM41 with calix[4]arene (CX4) was also carried out.

[0090] An impregnation mass percentage of 16% was obtained.

[0091] The TGA results in Figure 7 support the presence of CX4 in the nanopores. Pure (unconfined) CX4 has a melting point in the region of 310 - 315 °C (verified by TGA), but a major mass loss occurs after 420 °C. This offset to a higher temperature indicates that CX4 is present in the nanopores, as shown for HQ in Figure 2(B).

[0092] A hydrogen capture test was conducted using an MCM41 porous substrate impregnated with 18 mass% of calix 4 arene.

[0093] The hydrogen capture results for the first 3 cycles are shown in Figure 10.

[0094] In this figure, the mass of captured hydrogen for the composites MCM41+HQ and MCM41+calix 4 arene is compared.

[0095] The capacity is expressed per mass of the crystal. For the first 3 cycles, the trend is virtually the same as that of HQ, i.e., it increases as a function of the cycle.

[0096] Impregnation and capture by urea For the matrix PSP, the impregnation with urea and the pore occupancy test (pore diameter less than 10 nm) were also carried out according to the above protocol for HQ (Figure 1).

[0097] An impregnation rate of 13% was obtained.

[0098] The results are shown in Figure 8. The % within the box corresponds to the percent volume in pores of size less than 10 nm in the initial matrix, which was lost after impregnation, i.e., it was filled with urea (here 20%).

[0099] The hydrogen capture test was also carried out using the obtained composite material. The results are shown in Figure 9.

Claims

1. A porous composite material for gas storage, comprising: - a porous matrix having pores with a diameter of less than 10 nm, and - an organic compound wherein the organic compound is contained within the pores having a diameter of less than 10 nm. A porous composite material characterized by this.

2. The porous composite material according to Claim 1, wherein the pores of the porous matrix having a diameter of less than 10 nm correspond to at least 30%, preferably at least 50%, of the micro / mesoporous volume of the porous matrix.

3. The porous composite material according to Claim 1 or 2, wherein the organic compound is selected from compounds capable of forming intermolecular hydrogen bonds.

4. The porous composite material according to any one of Claims 1 to 3, wherein the organic compound is selected from the following compounds: polyphenols, polythiols, urea, thiourea, and calixarenes.

5. The porous composite material according to any one of Claims 1 to 4, wherein the organic compound is selected from hydroquinone, resorcinol, fluorohydroquinone, 2,5-dihydroxyl-pyridine, catechol, urea, thiourea, and calix[4]arene.

6. The porous composite material according to any one of Claims 1 to 5, wherein the organic compound is contained within the pores in crystalline, semi-crystalline, and / or amorphous forms.

7. The porous composite material according to any one of Claims 1 to 6, wherein the porous matrix is selected from organic or inorganic micro- and / or mesoporous substrates such as silica, carbon, alumina, aluminosilicate, activated carbon, molecular sieves, zeolites, metal-organic frameworks (MOF), Hofmann clathrates, and polymers.

8. The porous composite material according to any one of Claims 1 to 7, wherein the porous matrix is selected from mesoporous MCM-41 and SBA-15 silica, aluminosilicate, carbon xerogel, activated carbon, and porous polymers.

9. The porous composite material according to any one of Claims 1 to 8, wherein the organic compound occupies at least 25%, preferably at least 40%, of the micro- and mesoporous volume of the porous matrix.

10. A dry method for preparing the porous composite material according to any one of Claims 1 to 9, the method comprising adsorption / condensation of the organic compound in the gas phase within the pores of the porous matrix.

11. The method according to claim 10, comprising a prior sublimation step of the organic compound from the solid phase to the gas phase. **Claim 12** A gas storage method, comprising: - contacting the porous composite material according to any one of claims 1 to 9 with the gas to be stored or a mixture containing the gas; - applying one or more continuous temperature cycles The method comprising. **Claim 13** The method according to claim 12, wherein the gas is dihydrogen. **Claim 14** A gas storage device comprising the porous composite material according to any one of claims 1 to 9 and further comprising a gas, wherein the gas is stored in pores containing an organic material.

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