Solid sorbents for removal of carbon dioxide from gas streams at low temperatures

• US 6,908,497 B1
• Filed: 04/23/2003
• Issued: 06/21/2005
• Est. Priority Date: 04/23/2003
• Status: Active Grant

• Current Assignee: US Department of Energy (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Department Of Energy
• Inventors: Sirwardane, Ranjani V.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US10/420,713
• Time in Patent Office: 790 Days
• Field of Search: 951/36, 951/39, 951/48, 959/00, 961/08, 961/53, 961/54, 423/203, 423228-230, 502/400, 502/405
• US Class Current: 95/136
• CPC Class Codes: B01D 2253/20 Organic adsorbents
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• 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: B01D 53/52 Hydrogen sulfide
• CPC Class Codes: B01D 53/526 Mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01J 20/12 Naturally occurring clays or bleaching earth
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: B01J 20/3204 Inorganic carriers, supports or substrates
• CPC Class Codes: B01J 20/3248 the functional group or the linking, spacer or anchoring group as a whole comprising at least one type of heteroatom selected from a nitrogen, oxygen or sulfur, these atoms not being part of the carrier as such
• CPC Class Codes: B01J 20/3251 comprising at least two different types of heteroatoms selected from nitrogen, oxygen or sulphur
• CPC Class Codes: B01J 20/3253 comprising a cyclic structure not containing any of the heteroatoms nitrogen, oxygen or sulfur, e.g. aromatic structures
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

New low-cost CO₂ sorbents are provided that can be used in large-scale gas-solid processes. A new method is provided for making these sorbents that involves treating substrates with an amine and/or an ether so that the amine and/or ether comprise at least 50 wt. percent of the sorbent. The sorbent acts by capturing compounds contained in gaseous fluids via chemisorption and/or physisorption between the unit layers of the substrate'"'"'s lattice where the polar amine liquids and solids and/or polar ether liquids and solids are located. The method eliminates the need for high surface area supports and polymeric materials for the preparation of CO₂ capture systems, and provides sorbents with absorption capabilities that are independent of the sorbents'"'"' surface areas. The sorbents can be regenerated by heating at temperatures in excess of 35° C.

Claims

1. A method for removing compounds from a fluid, the method comprising contacting the fluid with a polar nucleophilic moiety located on inside surfaces and outside surfaces of a clay substrate having a surface area of 0.72 to 26 m²/g, whereby the moiety attracts the compounds.

2. The method as recited in claim 1 wherein the compound is a gas at ambient temperature, the gas selected from the group consisting of carbon dioxide, hydrogen sulfide, and combinations thereof.

3. The method as recited in claim 1 wherein the compounds are removed at a temperature of between 25°

C. and 50°

C.

4. The method as recited in claim 1 wherein the moiety attracts the compounds via chemisorption or physisorption.

5. The method as recited in claim 1 wherein the polar nucleophilic moiety is regenerated in situ by heating the substrate to temperatures ranging from between 35°

C. to 100°

C. in an inert atmosphere.

6. A sorbent comprising:

a) a clay substrate having a surface area of 0.72 to 26 m²/g with external surfaces and internal surfaces in fluid communication with the environment; and

b) polar nucleophilic moieties covering said surfaces to allow interaction of the moieties with compounds in the environment.

7. The sorbent as recited in claim 6 wherein the moieties are present in a moiety-to-substrate weight ratio ranging from 1:

9 to 3;

2.

8. The sorbent as recited in claim 6 wherein the substrate has a layered structure capable of expanding to form passages to contain said moiety.

9. The sorbent as recited in claim 6 further comprising inert materials to enhance porosity of the substrate.

10. The sorbent as recited in claim 6 wherein the clay substrate is selected from the group consisting of bentonite, ball clay, fuller'"'"'s earth, kaolin, attapulgite, hectorite, meerschaum, palygorskite, saponite, sepiolite, common clay, and combinations thereof.

11. The sorbent as recited in claim 6 wherein the moieties are homogeneuosly dispersed thoroughout the substrate.

12. The sorbent as recited in claim 6 wherein the external surfaces are in fluid communication with the internal surfaces.

13. A process for producing enriched sorbents, the process comprising:

a) supplying a clay substrate having a surface area of 0.72 to 26 m²/g and having repeating strata and interstices between the strata, whereby the interstices define conduits which are in fluid communication with the atmosphere surrounding the substrate;

b) causing the interstices to expand;

c) coating the strata with a polar nucleophilic moiety; and

d) drying the coated strata.

14. The process as recited in claim 13 wherein the polar nucleophilic moiety is an amine selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, an aromatic amine, or a cyclic amine.

15. The process as recited in claim 13 wherein the polar nucleophilic moiety is a substituted amine containing one or more moieties selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, allyl, vinyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, and combinations thereof.

16. The process as recited in claim 13 wherein the polar nucleophilic moiety is an ether containing one or more moieties selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, allyl, vinyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, ethylene glycol, polyethylene glycol, and combinations thereof.

17. The process as recited in claim 13 wherein the process is conducted at temperatures below 80°

C.

18. The process as recited in claim 13 wherein the moiety facilitates sequestration of carbon dioxide.

19. The process as recited in claim 18 wherein the sequestration occurs on the exterior and in the interior of the substrate.

20. The process as recited in claim 13 wherein the absorption properties of sorbent produced are independent of the volume of the sorbent.