Nanostructured carbon materials for adsorption of methane and other gases

• US 9,067,848 B2
• Filed: 10/10/2013
• Issued: 06/30/2015
• Est. Priority Date: 10/19/2012
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Ahn, Channing, Stadie, Nicholas P., Fultz, Brent T, Murialdo, Maxwell
• Primary Examiner(s): LAWRENCE JR, FRANK M
• Application Number:
  US14/050,755
• Publication Number:
  US 20140113811A1
• Time in Patent Office: 628 Days
• Field of Search: 95/90, 951/16, 951/43, 959/00, 959/03, 961/08, 502/400, 502/416, 502/439
• US Class Current: 1/1
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/31 Pore size distribution
• CPC Class Codes: B01D 2257/7025 Methane
• CPC Class Codes: B01D 2259/4525 for storage and dispensing systems
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01J 20/00 Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
• CPC Class Codes: B01J 20/02 comprising inorganic material
• CPC Class Codes: B01J 20/103 comprising silica
• CPC Class Codes: B01J 20/186 Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: B01J 20/205 Carbon nanostructures, e.g. nanotubes, nanohorns, nanocones, nanoballs carbon nanotubes per se C01B32/15
• CPC Class Codes: B01J 20/28057 Surface area, e.g. B.E.T specific surface area
• CPC Class Codes: B01J 20/2809 Monomodal or narrow distribution, uniform pores
• CPC Class Codes: B01J 20/3057 Use of a templating or imprinting material molecularly imprinted polymers B01J20/268; filling pores of a substrate or matrix followed by the removal of the substrate or matrix
• CPC Class Codes: C07C 17/389 by adsorption on solids
• CPC Class Codes: C07C 29/76 by physical treatment
• CPC Class Codes: C07C 51/42 Separation; Purification; Stabilisation; Use of additives
• CPC Class Codes: C07C 9/04 Methane production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06
• CPC Class Codes: C10L 2230/14 for improving storage or transport of the fuel
• CPC Class Codes: C10L 2270/10 for transport, e.g. in pipelines as a gas hydrate slurry
• CPC Class Codes: C10L 3/06 : Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04 liquefying by pressure and cold treatment F25J
• CPC Class Codes: Y02C 20/10 : of nitrous oxide (N2O)
• CPC Class Codes: Y02C 20/20 : of methane
• CPC Class Codes: Y02C 20/40 : of CO2

Abstract

Provided are methods for storing gases on porous adsorbents, methods for optimizing the storage of gases on porous adsorbents, methods of making porous adsorbents, and methods of gas storage of optimized compositions, as in systems containing porous adsorbents and gas adsorbed on the surface of the porous adsorbent. The disclosed methods and systems feature a constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas onto the exposed surface of a porous adsorbent. Adsorbents with a porous geometry and surface dimensions suited to a particular adsorbate are exposed to the gas at elevated pressures in the specific regime where n/V (density) is larger than predicted by the ideal gas law by more than several percent.

Claims

1. A method for storing a gas on a porous adsorbent, the method comprising the steps of:

selecting said porous adsorbent having a first chemical composition;

determining a first pore size distribution for the porous adsorbent having the first chemical composition, wherein the first pore size distribution provides a constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas on an exposed surface of the porous adsorbent;

providing the porous adsorbent having a first plurality of ordered pore structures characterized by the first pore size distribution; and

contacting the porous adsorbent with the gas at a pressure sufficient to achieve adsorption of the gas on the porous adsorbent characterized by the constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas, thereby storing the gas on the porous adsorbent.

2. The method of claim 1, wherein the first pore size distribution provides the isosteric enthalpy of adsorption that increases as a function of uptake of the gas by at least 0.01 kJ mol⁻

1/mmol g<sup>−

1</sup>.

3. The method of claim 1, wherein the step of determining the first pore size distribution comprises steps of:

providing the porous adsorbent;

contacting the porous adsorbent with the gas at a pressure sufficient to achieve adsorption of the gas onto the exposed surface of the porous adsorbent; and

measuring the isosteric enthalpy of adsorption of the gas as a function of uptake of the gas by the porous adsorbent to establish that the first pore size distribution provides the constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas on the exposed surface of the porous adsorbent.

4. The method of claim 3, further comprising a step of determining a slope of the isosteric enthalpy of adsorption of the gas as a function of uptake of the gas by the porous adsorbent or further comprising a step of computing an isosteric enthalpy of adsorption of the gas as a function of uptake of the gas by the porous adsorbent by fitting or regression analysis of gas uptake data or further comprising a step of generating a plot of the isosteric enthalpy of adsorption of the gas as a function of uptake of the gas by the porous adsorbent.

5. The method of claim 3, wherein the step of measuring the isosteric enthalpy of adsorption comprises measuring a plurality of gas adsorption isotherms for a plurality of selected temperatures or comprises steps of adsorbing a known uptake amount of the gas on the exposed surface of the adsorbent material and measuring a heat quantity released by the known uptake amount of the gas upon adsorption or comprises measuring a temperature change of the porous adsorbent upon adsorption of a known uptake amount of the gas.

6. The method of claim 5, wherein each gas adsorption isotherm is measured by exposing the porous adsorbent to a plurality of pressures and measuring an amount of uptake of the gas by the porous adsorbent after the porous adsorbent is allowed to come to thermal equilibrium to a selected temperature for each of the plurality of pressures.

7. The method of claim 6, wherein the isosteric enthalpy of adsorption is computed using the equation

8. The method of claim 1, further comprising a step of empirically characterizing isosteric enthalpy of adsorption values for a range of pore size distributions for the porous adsorbent or further comprising a step of empirically characterizing isosteric enthalpy of adsorption values for a range of porous adsorbents having different chemical compositions.

9. The method of claim 1, wherein the step of determining the first pore size distribution comprises calculating a density functional theory model of the porous adsorbent for a number of candidate pore size distributions or calculating a Lennard-Jones potential for a system comprising the porous adsorbent and the gas;

or wherein the step of determining the first pore size distribution comprises using an empirical method selected from the group consisting of MP (micropore) method, α

_s-method, DR (Dubinin-Radushkevich) method, DA (Dubinin-Astakhov) method, Dubinin-Stoekli method, Horvah-Kawazoe method, BJH method and Nguyen-DO (ND) method and any combination thereof.

10. The method of claim 1, wherein the gas comprises one or more of:

H₂O, H₂, CH₄, C₂H₄, C₂H₂, C₃H₈, C₃H₆, C₄H₁₀, C₅H₁₂, C₅H₁₀, C₆H₁₄, C₆H₁₂, C₆H₆, CH₃OH, C₂H₅OH, C₃H₇OH, CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄, HCl, HF, BH₃, B₂H₆, BF₃, BCI₃, HCOOH, O₂, O₃, HOOH, H₂S, any deuterated form of these, any partially deuterated form of these, CO₂, CO, N₂, CN, N₂O, Xe, Kr, SiH₄, CF₄, CCl₄, SF₆, Si F₄, CS₂, natural gas and any combination of these.

11. The method of claim 1, wherein the gas comprises a first gas and one or more additive gases and wherein adsorption of the one or more additive gases onto the exposed surface of the porous adsorbent provides the constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas.

12. The method of claim 11, wherein the first gas comprises methane and the one or more additive gases are selected from the group consisting of C₂H₆, C₂H₄, C₂H₂, C₃H₈, C₃H₆, C₄H₁₀, C₅H₁₂, C₅H₁₀, C₆H₁₄, C₆H₁₂, C₆H₆, CO, CO₂, H₂O, H₂, Xe, Kr, B₂H₆, SiH₄, CF₄, CCl₄, SF₆, SiF₄ and CS₂.

13. The method of claim 1, wherein the contacting step comprises contacting the exposed surface of the porous adsorbent to the gas at a temperature within the range of −

169°

C. to 125°

C.;

or wherein the contacting step comprises contacting the exposed surface of the porous adsorbent to the gas at a temperature greater than a critical temperature of the gas, at a pressure greater than the critical pressure of the gas or at both a temperature greater than a critical temperature of the gas and a pressure greater than the critical pressure of the gas;

or wherein the contacting step comprises contacting the exposed surface of the porous adsorbent to the gas at a pressure greater than atmospheric pressure;

or wherein the contacting step comprises contacting the exposed surface of the porous adsorbent to the gas at a pressure greater than or equal to 1 MPa.

14. The method of claim 1, wherein the porous adsorbent has the first chemical composition comprising elements selected from the group consisting of hydrogen, beryllium, boron, carbon, nitrogen, oxygen, a halogen, an alkali metal, an alkaline earth element, a noble metal and any combination of these.

15. The method of claim 1, wherein the first chemical composition comprises a carbonaceous material.

16. The method of claim 1, wherein the first chemical composition comprises graphitic carbon, graphene, HOPG, amorphous carbon, carbon black, coke, carbon nanotubes, fullerenes, activated carbon, superactivated carbon, carbon aerogel, template carbon, intercalated graphite, sp²-hybridized carbon, zeolite templated carbon, porous aluminosilicate-templated carbon, mesoporous silica-templated carbon or any combinations of these.

17. The method of claim 1, wherein the porous adsorbent comprises a microporous material or a mesoporous material.

18. The method of claim 1, wherein the first pore size distribution comprises a unimodal distribution with a mean pore cross sectional dimension selected from the range of 0.4 nm to 2.6 nm or wherein the first pore size distribution comprises a unimodal distribution with a pore cross sectional dimension standard deviation less than 0.5 nm.

19. The method of claim 1, wherein the first pore size distribution comprises a mean inter pore spacing dimension selected from the range of 1 nm to 5 nm or wherein the first pore size distribution comprises an inter pore spacing dimension standard deviation less than 0.5 nm.

20. The method of claim 1, wherein the porous adsorbent has a specific surface area selected from the range of 100 m² g⁻

1 to 6000 m² g<sup>−

1</sup>.

21. The method of claim 1, wherein the pore structures of the porous adsorbent are provided in an ordered network, wherein the ordered network is a connected or unconnected lattice comprising channels in one or more of the following patterns:

1D (unconnected), 2D simple square, 2D hexagonal, 2D other, 3D simple cubic, 3D hexagonal, 3D other, a connected or unconnected lattice of slits in one or more patterns selected from the group consisting of 2D (unconnected) and 3D regularly connected slits.

22. The method of claim 1, wherein the first chemical composition comprises a zeolite-templated carbon, wherein the gas comprises methane and wherein the first pore size distribution comprises a mean pore cross sectional selected from the range of 0.8 nm to 1.4 nm and a pore cross sectional dimension standard deviation less than 0.3 nm.

23. The method of claim 1, wherein at least a portion of the pore structures confine gas adsorbed onto the exposed surface of the porous adsorbent in two dimensions or wherein at least a portion of the pore structures confine gas adsorbed onto the exposed surface of the porous adsorbent in three dimensions;

and wherein at least a portion the pore structures comprise a channel structure or wherein at least a portion the pore structures comprise, at least in part, a box structure, a cage structure or a perforated spherical structure.

24. The method of claim 1, wherein the constant or increasing isosteric enthalpy of adsorption varies between 2 kJ mol⁻

1 and 48 kJ mol<sup>−

1</sup>, or wherein the isosteric enthalpy exhibits an increase amount between 0.2 kJ mol<sup>−

1</sup> and 6 kJ mol<sup>−

1</sup>.

25. The method of claim 1, wherein the constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas occurs at a fractional coverage of the exposed surface selected from the range of 10% to 50% or from the range of 0% to 60% or wherein the constant or increasing isosteric enthalpy of adsorption as a function of uptake occurs for pressures of the gas selected from the range of 0.01 MPa to 10 MPa or wherein the constant or increasing isosteric enthalpy of adsorption as a function of uptake occurs for temperatures of the gas selected from the range of −

70°

C. to 0°

C. or selected from the range of −

50°

C. to 25°

C.

26. The method of claim 1, wherein the constant or increasing isosteric enthalpy of adsorption provides for reversible uptake or release of the gas adsorbed onto the exposed surface as the pressure is varied.

27. The method of claim 1, wherein the gas is adsorbed onto the exposed surface to an absolute uptake amount or excess uptake amount selected from the range of 0.5 mmol g⁻

1 to 50 mmol g<sup>−

1</sup>.

28. The method of claim 1, wherein a deliverable gravimetric gas capacity of the porous adsorbent is selected from the range of 5 to 50 weight percent or selected from the range of 1 to 20 weight percent.

29. A method of making a porous adsorbent having a first chemical composition, the method comprising:

determining a first pore size distribution for the porous adsorbent, wherein the first pore size distribution provides a constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas on an exposed surface of the porous adsorbent;

providing a porous template material comprising a first plurality of ordered pore structures having a second pore size distribution;

exposing the porous template material to a first chemical composition precursor to create a porous template material and first chemical composition precursor mixture;

converting the first chemical composition precursor to the first chemical composition, thereby creating a porous template material and first chemical composition mixture; and

removing the porous template material from the porous template material and first chemical composition mixture, thereby creating the porous adsorbent.

30. A stored gas composition comprising a porous adsorbent and a gas adsorbed on an exposed surface of the porous adsorbent, wherein the porous adsorbent has a first chemical composition and a first plurality of ordered pore structures characterized by a first pore size distribution, wherein the first pore size distribution provides a constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas on the exposed surface of the porous adsorbent for a pressure of the gas exposed to the porous adsorbent selected from the range of 1 MPa to 12 MPa and at a temperature the range of −

169°

C. to 125°

C.;

wherein the gas is adsorbed on the exposed surface of the porous adsorbent to an absolute uptake amount selected from the range of 0.5 mmol g<sup>−

1</sup> to 50 mmol g<sup>−

1</sup>.