Microfibrous entrapment of small reactive particulates and fibers for high contacting efficiency removal of contaminants from gaseous or liquid streams

• US 20050169820A1
• Filed: 08/26/2004
• Published: 08/04/2005
• Est. Priority Date: 08/26/2003
• Status: Active Grant

• Current Assignee: Auburn University
• Original Assignee: Auburn University
• Inventors: Lu, Yong, Chen, Laiyuan, Cahela, Don, Tatarchuk, Bruce J., Luna, Eric, Chang, Bong Kyu
• Granted Patent: US 7,501,012 B2
• Time in Patent Office: Days
• US Class Current: 422/177
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/502 Carbon monoxide
• CPC Class Codes: B01D 2258/0208 from fuel cells
• CPC Class Codes: B01D 2258/0225 from chemical or biological warfare
• 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 53/8612 Hydrogen sulfide
• CPC Class Codes: B01D 53/864 Removing carbon monoxide or hydrocarbons
• CPC Class Codes: B01D 53/885 Devices in general for catalytic purification of waste gases
• CPC Class Codes: C01B 2203/042 Purification by adsorption on solids
• CPC Class Codes: C01B 2203/044 Selective oxidation of carbon monoxide
• CPC Class Codes: C01B 2203/047 the impurity being carbon monoxide
• CPC Class Codes: C01B 2203/0485 the impurity being a sulfur compound
• CPC Class Codes: C01B 2203/066 with fuel cells
• CPC Class Codes: C01B 3/508 by selective and reversible uptake by an appropriate medium, i.e. the uptake being based on physical or chemical sorption phenomena or on reversible chemical reactions the appropriate mediums per se C01B3/0005
• CPC Class Codes: C01B 3/583 the reaction being the selective oxidation of carbon monoxide
• CPC Class Codes: H01M 8/0668 Removal of carbon monoxide or carbon dioxide
• CPC Class Codes: H01M 8/0675 Removal of sulfur
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A microfibrous matrix with embedded supporting particulates/fibers and chemically reactive materials is provided as a filtration system for the removal of contaminants and other harmful agents from liquid and gaseous streams. Such filter may be used for example to protect the intolerant anodes and cathodes of fuel cells from damaging H₂S while simultaneously aiding the selective conversion of CO to CO₂ in fuel streams predominated by hydrogen. In general, the reactive materials utilized as well as the supporting matrix of fibers may be broadly selected to remove specific contaminants at specific reaction conditions inherent to the application. Such materials may include chemically reactive materials as high surface area carbons, zeolites, silicas, aluminas, inorganic metal oxides, polymer resins, ZnO, ZnO/Carbon, Pt/γ-Al₂O₃, PtCo/γ-Al₂O₃, ZnO/SiO₂ and various other catalysts, sorbents or reactants. In an alternative embodiment, entrapped sorbents and other reactants may be used to provide a highly efficient gas and/or liquid separation and purification methodology for gas masks, building filtration systems, and/or as polishing media located downstream of traditional packed bed filtration systems so as to achieve the high volume loading/capacity of the packed bed along with the overall contacting efficiency of the outlet polishing layer.

Claims

1. A filtration system comprising:

a) a matrix of microfibers;

b) support, adsorbent or reactive particulates and/or fibers entrapped within said matrix;

c) a pre-selected reactive material impregnated into said matrix and supported by said particulates and/or fibers; and

d) wherein said filtration system can remove contaminants from liquid or gaseous streams.

2. The filtration system of claim 1 wherein thin sheets of said matrix with said supporting particulates, reactants, adsorbents and/or fibers and said pre-selected reactive materials impregnated therein are chemically functionalized and then stacked in a pre-defined sequence so as to achieve staged chemical reactions and processes and wherein said thin sheets are less than a three millimeters in thickness.

3. The filtration system of claim 2 wherein said thin sheets provide high contacting efficiency and small critical bed depth such that said thin sheets may be made extremely thin and still achieve high levels of saturation, reaction and/or contaminant removal.

4. The filtration system of claim 3 wherein said adsorption and reaction levels are such that they may provide greater than a 5-log differential in concentration between inlet and outlet concentrations of said contaminants.

5. The filtration system of claim 3 wherein said thin sheets comprise a sorbent system of specified gas life capacity and volume, wherein the pressure drop through said bed depth decreases with the square of said bed depth'"'"'s cross-sectional area.

6. The filtration system of claim 4 wherein said thin sheets are sealed into a chemically protective hood for human use so as to permit small volume/mass packaging via folding into an easily carried package and wherein said hooded thin sheets are laminated with a thin sheet of HEPA filtration media so as to provide both particulate and gas removal/protection for the wearer.

7. The filtration system of claim 3 wherein said bed depth is comprised of an upstream packed bed of larger diameter reactive catalyst and sorbent particulates and a downstream polishing layer of smaller diameter microfibrous entrapped reactive catalyst and sorbent particulates so as to advantageously utilize the volume loading capacity of said packed bed and the overall contacting/removal efficiency of the exit polishing layer.

8. The filtration system of claim 2 wherein said reactive materials are a PROX CO catalyst, in particular PtCo/γ

-Al₂O₃.

9. The filtration system of claim 2 wherein said reactive materials include optimized multiple H₂S removal sorbents/reactants for both low and high temperature performance and regenerability.

10. The filtration system of claim 9 wherein said reactive materials comprising said optimized multiple H₂S removal sorbents/reactants include ZnO/Carbon and ZnO/SiO₂, respectively.

11. The filtration system of claims 6 or 7 or 8 or 9 wherein said reactive materials are layered to achieve pre-determined operations capabilities with regard to temperature, selectivity, and outlet gas performance/compositions.

12. The filtration system of claim 1 wherein loading of the reactive material within said matrix and the corresponding intra-layer void volume, the matrix thickness and its cross-sectional area are pre-selected to maximize the reaction rate per unit volume, the reaction rate per unit mass, and/or the reaction rate per unit pressure drop.

13. The filtration system of claim 1 wherein said microfibers of said matrix are metal fibers and wherein said microfibers impart high temperature operational characteristics, certain malleability and joining/bonding capabilities, and/or electrical conductivity and IR self-heating attributes to said filtration system.

14. The filtration system of claim 1 wherein said microfibers of said matrix are polymer, glass and/or ceramic fibers and wherein said microfibers impart specific corrosion/chemical resistance, thermal stability behavior, mechanical properties, specific cost factors, and overall density attributes to said filtration system.

15. The filtration system of claim 1 wherein said matrix is pleated or similarly structured so as to reduce the effective face velocity of incoming reactant streams, increase intralayer residence times, and reduce overall pressure drop.