Porous composite and use thereof for gas storage

Abstract

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

Claims

1. A porous composite for gas storage, comprising: a porous matrix comprising pores having a diameter of less than 10 nm, and an organic compound, said porous composite being characterized in that said organic compound is contained within said pores of diameter less than 10 nm.

2. The porous composite according to claim 1, such that the pores of the porous matrix of diameter less than 10 nm represent at least 30%, preferably at least 50% of the micro-/mesoporous volume of the porous matrix.

3. The porous composite according to claim 1, such that the organic compound is chosen from among compounds able to form intermolecular hydrogen bonds.

4. The porous composite according to claim 1, such that said organic compound is chosen from among the following compounds: polyphenols, polythiols, ureas, thioureas and calixarenes.

5. The porous composite according to claim 1, such that said organic compound is chosen from among hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene.

6. The porous composite according to claim 1, such that said organic compound is contained in crystalline, semi-crystalline and/or amorphous form within the pores.

7. The porous composite according to claim 1, such that the porous matrix is chosen from among organic or mineral micro-and/or mesoporous substrates such as silica, carbon, alumina, aluminosilicates, activated carbons, molecular sieves, zeolites, Metal Organic Frameworks (MOFs), Hofman clathrates and polymers.

8. The porous composite according to claim 1, such that the porous matrix is chosen from among mesoporous MCM-41 and SBA-15 silicas, aluminosilicates, carbon xerogels, activated carbons and porous polymers.

9. The porous composite according to claim 1, such that the organic compound occupies at least 25%, preferably at least 40% of the micro-and mesoporous volume of the porous matrix.

10. A dry process for preparing a porous composite according to claim 1, comprising the adsorption/condensation of said organic compound in gaseous phase within the pores of said porous matrix.

11. The process according to claim 10 comprising the prior sublimation step of said organic compound, from the solid phase to the gas phase.

12. A gas storage method, comprising: contacting the porous composite according to claim 1 with the gas to be stored, or a mixture comprising said gas; applying one or more successive temperature cycles.

13. The method according to claim 12, such that the gas is dihydrogen.

14. A gas storage device comprising the porous composite according to claim 1, and additionally comprising a gas, said gas being stored within the pores comprising the organic material.

Description

FIGURES

[0071] FIG. 1 gives a schematic of the impregnation device.

[0072] FIG. 2 gives the results obtained after impregnation of different porous matrices with hydroquinone (HQ). (A): Impact of impregnation time on weight percentage (%) of impregnated HQ for 3 carbon matrices (1 fibrous matrix named tissue and 2 activated carbons), 3 mesoporous matrices in silica and a porous polymer. (B): TGA/DSC analysis showing that HQ is contained inside the pores of MCM-41 silica (peak offset compared with solid HQ). (C): Analysis of pore volume by argon porosimetry at 87 K, before (grey curve) and after impregnation with HQ (impregnation time: 8h) (black curve): 80% of the pore volume is occupied by HQ. (D): Pore size distribution by argon porosimetry at 87K before (grey curve) and after impregnation with HQ (black curve).

[0073] FIG. 3 illustrates the trend in weight percentage of captured H.sub.2 (per total weight of material) as a function of temperature cycles varying between 0 and 100 C. for MCM-41 impregnated with HQ (with an impregnation time of 8 h) (P=20 bar).

[0074] FIG. 4 gives the weight percentage of captured H.sub.2 (per total weight of material) as a function of temperature cycles varying between 0 and 100 C. for beads of porous polymer (with an impregnation time of 14 h) impregnated with HQ (P=20 bar).

[0075] FIG. 5 gives the comparison of variation in the quantity of stored hydrogen per weight of total sample (matrix+HQ) as a function of the number of cycles at 0 C., between the MCM41 substrate and comparative SF300A substrate.

[0076] FIG. 6 gives the comparison of variation in the quantity of stored hydrogen, per weight of HQ impregnated in the matrices, for the MCM41 substrate and comparative substrate SF300A.

[0077] FIG. 7 gives the curve obtained by TGA showing the variation in mass of the porous substrate alone (MCM41) and of the substrate after impregnation with calix[4]arene.

[0078] FIG. 8 gives the curves of accumulated volumes obtained by argon porosimetry at 87 K (IQ-Quantachrome-Anton Paar) for the matrix (PSP) before impregnation with urea and after impregnation (weight percentage of impregnation 13%).

[0079] FIG. 9 illustrates the H.sub.2 storage capacity of the matrix PSP impregnated with 13% urea over temperature cycles of 0-100 C. per gram of composite.

[0080] FIG. 10 illustrates the H.sub.2 storage capacity of MCM41 impregnated with 18% calix[4]arene over the temperature cycles, compared with the composite MCM41+HQ.

EXAMPLES

Preparation of the Porous Composite

[0081] The protocol is illustrated in FIG. 1: [0082] 1Between 1 and 5 g of solid organic compound (hydroquinone, HQ) is placed in a crucible above which there is positioned another crucible containing the porous matrix to be impregnated (between 200 and 1000 mg) previously purified in a low vacuum at an adapted temperature (200 C. for carbons, 300 C. for silicas and 120 C. for the polymer) according to material. [0083] 2The two crucibles are separated by a Durapore filter of porosity 0.45 m. [0084] 3The assembly is placed in a vacuum oven at 120 C. for a time of between 1 and 64 hours so that the HQ is sublimated and is adsorbed in crystalline, semi-crystalline and/or amorphous form inside the pores of the upper-positioned matrix. The impact of impregnation time is analysed. [0085] 4The system is then cooled (controlled temperature ramp) and returned to atmospheric pressure.

Impregnation Results:

[0086] The protocol was tested on carbon and silica micro/mesoporous adsorbents: [0087] 1: Tissue [0088] 2: G-Bac [0089] 3: F400 [0090] 4: Porous polymer [0091] 5: MCM-41 [0092] 6: SBA-15 [0093] 7: SiAl

[0094] Tissue (PICA woven activated carbon by PICY Company, Levallois, FRANCE), G-bac (by Kureha) and F400 (Filtrasorb400 by Calgon Carbon Corporation) are carbon matrices. MCM-41, SBA-15 and SiAl are silica matrices referenced under these names.

[0095] The porous polymer is Optipore by Dow Chemicals (recently referenced by Dupont).

[0096] The organic product used is hydroquinone (purity >99.5%, supplied by Acros Organics). The maximum impregnation rates are reached after a few hours and are between 12 and 38 weight % depending on substrate. FIG. 2A illustrates the results obtained for the different above-identified matrices 1-7.

[0097] SEM, TGA/DSC analyses, and characterizations by gas porosimetry showed that the HQ was well impregnated within the porosity (cf. FIG. 2).

H.SUB.2 .Capture Tests

[0098] H.sub.2 capture tests were performed via gravimetric technique using a magnetic suspension balance (Rubotherm). [0099] The impact of temperature and pressure was analysed. An exhaustive study of the hybrid MCM-41/HQ material gave the following results: [0100] a first rise in temperature is needed to activate the system, 80 C. for MCM-41, [0101] successive temperature cycles, (from 0 C. as minimum temperature to 100 C. as maximum temperature for the example given in FIG. 3 i.e. MCM-41/HQ, first allow capture/release of H.sub.2 and secondly allow a maximum capture rate to be reached after about ten cycles; [0102] the compound remains stable at ambient pressure for a least 48 h; [0103] for the MCM-41/HQ system, the weight percentage of H.sub.2 obtained at atmospheric pressure and at 25 C. (FIG. 3) is about 1.2% per total weight of impregnated material i.e. 5.7% per weight of HQ. [0104] Capture tests on a very different porous matrix (polystyrene porous polymer, Optipore by Dow Chemicals) gave very similar results (FIG. 4), which appears to show a large variability in the nanoporous matrices (in terms of chemical type and pore size) able to be used.

Comparison With Existing Solid H.SUB.2 .Storages:

[0105] The H.sub.2 capture rate obtained, per weight of composite (1.2%) or per weight of HQ (5.7%) lies within the average for existing methods, with reference to the classification of different existing solid storages reported by Gupta et al., Energy Storage Materials, vol. 41, p. 69-107, October 2021.

[0106] Nonetheless, the system of the invention has the considerable advantage of operating at ambient temperature and at moderate temperatures (1 bar, 25 C.), together with lower cost and better stability compared with hydrides in particular.

Comparative Test

[0107] Tests were also performed on porous particles of silica, SiliaFlash SF300A (supplier Silicycle) having a diameter of between 200 and 500 microns (same particles as those used in the article by Coupan et al. (Chemical Engineering Journal 2017, 325, 35-48). [0108] Drying of the SF300A particles (purification) for 24 h at 110 C. Cooling in a desiccator followed by placing in an oven in a closed container at 35 C. [0109] Hydroquinone/ethanol impregnation solution: 7 g of hydroquinone are placed in an Erlenmeyer. The total weight is adjusted to 20 g with absolute ethanol. The Erlenmeyer is closed, placed under magnetic stirring then heated in an oven at 35 C. until complete dissolution of the crystals in the solvent (clear solution). [0110] 3 grams of SF300A silica particles (held at 35 C.) are placed in a glass flask and covered with a sufficient quantity of HQ/ethanol impregnation solution (at 35 C.) until all the particles are fully immersed. The flask containing the silica particles and impregnation solution is shaken manually, sealed, and left in the oven at 35 C. for 24 h. [0111] after a contact time of 24 h between the silica particles and impregnation solution, the particles impregnated with liquid are filtered on a Bushner filter connected to a vacuum flask, recovered in a crystallizer, and oven dried at 35 C. for 24 h.

[0112] The resulting SF300A/HQ composites are in the form of a uniform white powder (no black or grey particles, no clusters, no plaques) perfectly dry.

[0113] The impregnation rate of these composites measured by TGA is 32 mass % of HQ.

[0114] After drying, the composite particles were packaged in a glass flask with sealed stopper, in air and at ambient temperature. They were kept in this flask until testing on the magnetic suspension balance.

[0115] The composite was tested for hydrogen storage. The same capture protocol was followed, namely temperature cycles between 0 C. and 100 C., at a pressure of 20 hydrogen bar. The results are given in FIGS. 5 and 6, giving a comparison of H.sub.2 capture cycles with MCM41+HQ, having a mean pore size of 3 nm but a surface chemistry comparable to that of SF300A.

[0116] In FIG. 5, the quantity of stored hydrogen per total weight of sample (matrix+HQ) is plotted as a function of the number of cycles at 0 C. (the quantities are zero at 100 C. for SF300A+HQ).

[0117] The stored quantities of H.sub.2 for the MCM41+HQ sample are ten times higher than those for SF300A after about ten cycles.

[0118] In FIG. 6, the stored quantities are expressed per weight of HQ impregnated in the matrices. They are 7 times higher in MCM41+HQ.

[0119] These results show that when HQ is impregnated in pores of small size (smaller than 10 nm), the stored quantities are much higher as a result of the confinement effect in pores of this size.

Impregnation and Capture With Calixarene

[0120] Impregnation was also carried out with calix[4]arene (CX4) in the porous substrate MCM41, by sublimation of CX4 at 300 C. under a high vacuum for 72 h.

[0121] An impregnation weight percentage of 16% was obtained.

[0122] The TGA results in FIG. 7 confirm the presence of CX4 in the nanoporosity. Pure (non-confined) CX4 has a melting point in the region of 310-315 C. (verified by TGA), while the main mass loss takes place after 420 C. This offset towards the higher temperatures indicates that the CX4 is present in the nanoporosity as shown for HQ in FIG. 2(B).

[0123] The hydrogen capture test was conducted with the MCM41 porous substrate impregnated with calix4arene at 18 weight %.

[0124] The hydrogen capture results for the first 3 cycles are given in FIG. 10.

[0125] In this Figure, the weight of captured hydrogen for the composites MCM41+HQ and MCM41+Calix4arene are compared.

[0126] The capacities are expressed per mass of crystals. For the first 3 cycles, the trend is effectively similar to that of HQ, namely an increase as a function of cycles.

Impregnation and Capture With Urea

[0127] Impregnation and pore occupation tests (pore diameter less than 10 nm) were also conducted with urea following the above protocol for HQ (FIG. 1) on a matrix PSP. An impregnation rate of 13% was obtained.

[0128] The results are given in FIG. 8 in which the boxed % corresponds to the percent volume, in pores of size less than 10 nm in the initial matrix, which was lost after impregnation, in other words which was filled with urea (here 20%).

[0129] Dihydrogen capture tests were also performed with the resulting composite: the results are given in FIG. 9.