FIBER SORBENTS

• US 20100313755A1
• Filed: 10/13/2009
• Published: 12/16/2010
• Est. Priority Date: 06/11/2009
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Bhandari, Dhaval A., Koros, William John
• Granted Patent: US 8,377,172 B2
• Time in Patent Office: Days
• US Class Current: 95/135
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/106 Silica or silicates
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/112 Metals or metal compounds not provided for in B01D2253/104 or B01D2253/106
• CPC Class Codes: B01D 2253/202 Polymeric adsorbents
• CPC Class Codes: B01D 2253/304 Linear dimensions, e.g. particle shape, diameter
• CPC Class Codes: B01D 2257/30 Sulfur compounds
• CPC Class Codes: B01D 2257/708 Volatile organic compounds V.O.C.'s
• CPC Class Codes: B01D 2258/06 Polluted air
• 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 53/04 with stationary adsorbents B01D53/025 takes precedence
• CPC Class Codes: B01J 20/08 comprising aluminium oxide or hydroxide; comprising bauxite
• CPC Class Codes: B01J 20/10 comprising silica or silicate
• CPC Class Codes: B01J 20/18 Synthetic zeolitic molecular sieves
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: B01J 20/261 obtained by reactions only involving carbon to carbon unsaturated bonds macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds per se C08F
• CPC Class Codes: B01J 20/262 obtained otherwise than by reactions only involving carbon to carbon unsaturated bonds, e.g. obtained by polycondensation macromolecular compounds obtained otherwise than by reactions only involving unsaturated carbon-to-carbon bonds per se C08G
• CPC Class Codes: B01J 20/28011 Other properties, e.g. density, crush strength
• CPC Class Codes: B01J 20/28023 Fibres or filaments fibres or filaments in the form of membranes B01J20/28038; B01J20/28007 takes precedence
• CPC Class Codes: B01J 20/28061 : being in the range 100-500 m2/g
• CPC Class Codes: B01J 20/3268 : Macromolecular compounds
• CPC Class Codes: B01J 20/327 : Polymers obtained by reactions involving only carbon to carbon unsaturated bonds
• CPC Class Codes: B01J 20/3272 : Polymers obtained by reactions otherwise than involving only carbon to carbon unsaturated bonds
• CPC Class Codes: B01J 20/3293 : Coatings on a core, the core being particle or fiber shaped, e.g. encapsulated particles, coated fibers
• CPC Class Codes: B01J 20/3408 : of aluminosilicate molecular sieves
• CPC Class Codes: B01J 20/3416 : of sorbents or filter aids comprising free carbon, e.g. activated carbon
• CPC Class Codes: B01J 20/3425 : of sorbents or filter aids comprising organic materials
• CPC Class Codes: B01J 20/3433 : of sorbents or filter aids other than those covered by B01J20/3408 - B01J20/3425
• CPC Class Codes: B01J 20/3458 : in the gas phase
• CPC Class Codes: B01J 20/3475 : in the liquid phase
• CPC Class Codes: B01J 2220/46 : Materials comprising a mixture of inorganic and organic materials materials coated or impregnated on a carrier B01J20/32
• CPC Class Codes: B29K 2027/08 : PVDC, i.e. polyvinylidene chloride
• CPC Class Codes: C10G 25/003 : Specific sorbent material, not covered by C10G25/02 or C10G25/03
• CPC Class Codes: D01D 5/247 : Discontinuous hollow structure or microporous structure
• CPC Class Codes: D01F 8/10 : with at least one other macromolecular compound obtained by reactions only involving carbon-to-carbon unsaturated bonds as constituent

Abstract

The present invention relates to new fibers, new processes of using said fibers, and new sheath dope compositions for multi-layer spinning processes. The fibers comprise a porous core and a sheath surrounding said porous core. The fibers may be useful in, for example, processes for removing low level contaminants like sulfur compounds from a gas stream like natural gas.

Claims

1. A fiber comprising a porous core and a sheath surrounding said porous core wherein the core comprises a sorbent and a polymer and wherein the sheath is characterized by a heat resistance of at least about 110°

C. and one or more of the following;

(1) a water vapor transmission rate (WVTR) of less than about 50 Barrer at 38°

C. and 90% relative humidity;

or

(2) an O₂ permeability of less than about 10 Barrer;

or

(3) an N₂ permeability of less than about 1 Barrer;

or

(4) a CO2 permeability of less than about 20 Barrer.

2. The fiber of claim 1 wherein the sheath has an average thickness of from about 0.1 to about 100 microns.

3. The fiber of claim 1 wherein the sheath comprises a polymer selected from the group consisting of polyethylene terephthalate, polyvinylidene chloride, polyimide, polyacrylonitrile, polyester urethane, neoprene, polyether amide block co-polymer and mixtures thereof.

4. The fiber of claim 1 wherein the sorbent has a selectivity for a compound comprising sulfur over methane of about 10 to about 70.

5. The fiber of claim 1 wherein the sorbent has a surface area of at least 200 m²/g.

6. The fiber of claim 1 wherein the sorbent is selected from the group consisting of molecular sieve zeolites, MFI zeolites, activated carbon, activated alumina, silicates, amine-grafted silica, silico-aluminophosphates, aluminosilicates, aluminophosphates, metal oxides, and mixtures thereof.

7. The fiber of claim 6 wherein the zeolite is selected from the group consisting of zeolite 4A, 5A, Bx, NaX, NaY, faujasite, beta, mordenite, ZSM-5, ion exchanged zeolites, and mixtures thereof.

8. The fiber of claim 1 wherein the sorbent comprises at least 70% by weight of the fiber based on total dry fiber weight.

9. The fiber of claim 1 wherein the polymer is selected from the group consisting of a cellulose acetate, polyvinylpyrrolidone, polysulfone, epichlorohydrin, a polyether amide block co-polymer, polyimides, polyolefins, polypropylene, polyethylene, polyamides, poly(tetrafluoroethene), polyvinylidene chloride, polystyrene, polyisobutylene, polybutadiene, polyurethanes, elastomers, and copolymers and mixtures thereof.

10. The fiber of claim 1 wherein the sorbent is NaY, the polymer is cellulose acetate, the sheath comprises polyvinylidene chloride;

wherein the sorbent comprises at least 70% by weight of the fiber based on total dry weight; and

wherein the N₂ permeance is less than 5 (GPU) at 30 psig.

11. The fiber of claim 1 wherein said fiber further comprises a lumen adjacent to the porous core.

12. In a multi-layer spinning process for making a sheath on a fiber comprising spinning a sheath dope with a core dope to form a fiber comprising a porous core and a sheath surrounding said porous core wherein the improvement comprises employing a sheath dope composition which comprises a polyvinylidene chloride and a solvent comprising a dipolar aprotic solvent wherein the polyvinylidene chloride comprises at least about 15 weight percent based on the total weight of the composition.

13. The process of claim 12 wherein the dipolar aprotic solvent is selected from the group consisting of N-methylpyrrolidone, dimethylformamide, dimethyl acetamide, DMSO, tetrahydrofuran, toluene, and mixtures thereof.

14. The process of claim 12 wherein said sheath dope composition comprises from about 15 to about 60 weight percent polyvinylidene chloride and from about 40 to about 70 percent by weight N-methylpyrrolidone based on the total weight of the composition.

15. The process of claim 14 wherein said sheath dope composition further comprises tetrahydrofuran, acetone, n-heptane, or a mixture thereof.

16. The process of claim 12 wherein said sheath dope composition comprises (a) from about 0 to about 2 weight percent of water based on the total weight of the composition or (b) from about 1 to about 5 wt % of ethanol, acetic acid, propionic acid or mixture thereof based on the total weight of the composition.

17. The composition of claim 12 wherein said sheath dope composition comprises less than about 1 weight percent of water based on the total weight of the composition.

18. A process for reducing the amount of one or more low level contaminants of a gas stream comprising:

(a) contacting the gas stream comprising an initial concentration of one or more low level contaminants with one or more fibers which comprises a porous core and a sheath surrounding said porous core wherein the core comprises a sorbent and a polymer and wherein the sheath is characterized by a heat resistance of at least about 110°

C. and one or more of the following;

(1) a water vapor transmission rate (WVTR) of less than about 50 Barrer at 38°

C. and 90% relative humidity;

or

(2) an O₂ permeability of less than about 10 Barrer;

or

(3) an N₂ permeability of less than about 1 Barrer;

or

(4) a CO2 permeability of less than about 20 Barrer;

wherein said contacting is conducted in a manner such that the initial concentration of one or more low level contaminants in the gas stream is reduced by sorption of said one or more low level contaminants on said sorbent; and

then

(b) regenerating one or more fibers by passing a regenerating fluid which has a temperature of at least about 50°

C. over the sheath layer of said fiber in a manner such that the fluid does not substantially contact the porous core.

19. The process of claim 18 wherein the gas stream comprises natural gas, a petrochemical stream, city gas, diesel fuel, gasoline, LPG, jet fuel, a reformate gas, naptha and mixtures thereof;

wherein a low level contaminant comprises one or more compounds comprising sulfur;

and wherein steps (a) and (b) are repeated at least two or more times.

20. The process of claim 19 wherein the initial concentration of the compounds comprising sulfur is from about 5 to about 1000 ppm and wherein said contacting reduces the initial concentration of the compound comprising sulfur to a concentration of less than about 1 ppm.

21. The process of claim 18 which further comprises employing the gas stream with the reduced amount of low level contaminates as a fuel.

22. The process of claim 18 wherein the regenerating fluid which has a temperature of at least about 50°

C. comprises steam, hot water, a gas, or a mixture thereof.

23. The process of claim 18 which further comprises recovering at least a portion of the initial concentration of one or more low level contaminants.

24. The process of claim 18 wherein the one or more fibers are substantially aligned within a compartment comprising a gas stream inlet and outlet and a regenerating fluid inlet and outlet.

25. The process of claim 18 wherein a majority of the one or more of the fibers further comprises a lumen adjacent to the porous core.