Sorbent system and method for absorbing carbon dioxide (CO2) from the atmosphere of a closed habitable environment

• US 6,364,938 B1
• Filed: 08/17/2000
• Issued: 04/02/2002
• Est. Priority Date: 08/17/2000
• Status: Expired due to Term

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Birbara, Philip J., Michels, H. Harvey, Filburn, Thomas P., Nalette, Timothy A.
• Primary Examiner(s): SMITH, DUANE
• Application Number:
  US09/640,440
• Time in Patent Office: 593 Days
• Field of Search: 251/39, 259/00, 961/08, 961/53, 423/228
• US Class Current: 95/139
• CPC Class Codes: A62B 11/00 Devices for reconditioning breathing air in sealed rooms chemical purification, disinfection, or sterilisation of air A61L; in aircraft or submarines, insofar as they influence the construction of the vehicle or are influenced by its construction B63B, B64D, respectively; air-conditioning in general F24F
• CPC Class Codes: A62B 19/00 Cartridges with absorbing substances for respiratory apparatus carbon dioxide absorbing devices A61M16/22
• CPC Class Codes: B01D 2253/10 Inorganic adsorbents
• CPC Class Codes: B01D 2253/202 Polymeric adsorbents
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2259/40084 by exchanging used adsorbents with fresh adsorbents
• CPC Class Codes: B01D 2259/40096 by using electrical resistance heating
• CPC Class Codes: B01D 2259/4508 for cleaning air in buildings
• 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 53/62 Carbon oxides
• CPC Class Codes: B01J 20/26 Synthetic macromolecular compounds
• CPC Class Codes: B01J 20/264 derived from different types of monomers, e.g. linear or branched copolymers, block copolymers, graft copolymers
• CPC Class Codes: B01J 20/28026 Particles within, immobilised, dispersed, entrapped in or on a matrix, e.g. a resin
• 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

A regenerable high capacity carbon dioxide (CO₂) sorbent is operated to remove substantially all of the CO₂ present in either a dry, or a humid environment. The sorbent is an amine compound which is composed predominantly of secondary amine groups, and includes one or more functional nitrile groups. Primary and tertiary amine groups form a minor percent of the sorbent. The reaction product of tetraethylenepentamine (TEPA) and acrylonitrile (AN), which reaction product will be referred to hereinafter as “TEPAN” is a preferred sorbent. The addition of one or more nitrile functional groups to TEPA by reason of the reaction between AN and TEPA converts most of the primary amines in TEPA to secondary amines in TEPAN. We have discovered that the presence of predominantly secondary amines in the sorbent enhances the regenerable cyclic CO₂ absorption capacity of the sorbent by more than two and one-half times, as compared to a TEPA sorbent bed; and the use of TEPAN as the sorbent bed also significantly reduces amine volatility to low levels which are immeasurable. The sorbent bed of this invention is also easily regenerable.

Claims

1. A system for removing carbon dioxide (CO₂) from a breathable air stream, said comprising:

a) a CO₂ sorbent bed which contains a combination amine/nitrile CO₂ sorbent, wherein a major proportion of the amine constituent of the sorbent is formed from secondary amine groups, and wherein there is at least one functional nitrile group in the sorbent;

b) means for introducing the breathable air stream into said sorbent bed; and

c) means for removing said breathable air stream from said sorbent bed.

2. The system of claim 1 wherein said sorbent is a reaction product of tetraethylenepentamine and an acrylonitrile.

3. The system of claim 1 wherein said sorbent includes an amine constituent which is composed of at least 60% secondary amine groups, no more than 10% primary amine groups, and no more than 20% tertiary amine groups.

4. The system of claim 1 wherein there are a plurality of functional nitrile groups in said sorbent.

5. A method for removing carbon dioxide (CO₂) from a breathable air stream so as to produce a lower CO₂ level in said air stream, said method comprising:

a) providing an amine/nitrile CO₂ absorption bed containing predominantly secondary amine functional groups and at least one nitrile functional group; and

b) passing the air stream through the absorption bed.

6. The method of claim 5 wherein the absorption bed contains a reaction product (TEPAN) of tetraethylenepentamine (TEPA) and acrylonitrile (AN).

7. The method of claim 6 wherein one mole of TEPA and 2.3 moles of AN are reacted to form TEPAN, which is comprised predominantly of secondary amine functional groups and nitrile functional groups in a ratio of about 1.5 amine/2.0 nitrile.

8. A carbon dioxide sorption bed containing a sorbent which includes predominantly secondary amine functional groups and at least one nitrile functional group.

9. A carbon dioxide sorbent including predominantly secondary amine functional groups and at least one nitrile functional group.

10. Carbon dioxide (CO₂) sorbent resulting from a reaction of 1 mole of tetraethylenepentamine (TEPA) and 3 moles of an acrylonitrile (AN).