Photocatalytic oxidation of organics using a porous titanium dioxide membrane and an efficient oxidant

• US 6,136,186 A
• Filed: 07/14/1998
• Issued: 10/24/2000
• Est. Priority Date: 01/31/1997
• Status: Expired due to Fees

• Current Assignee: Lynntech Power Systems Limited
• Original Assignee: Lynntech Incorporated
• Inventors: Salinas, Carlos, Murphy, Oliver J., Gonzalez-Martin, Anuncia
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): PRINCE JR, FREDDIE GARY
• Application Number:
  US09/115,358
• Time in Patent Office: 833 Days
• Field of Search: 210/748, 210/749, 210/758-760, 210/763, 210/198.1, 210/205, 210/209, 210/195.1, 210/201, 210/908, 422/24, 422/186, 422/186.3, 204/157.15, 204/152.3
• US Class Current: 210/198.1
• CPC Class Codes: B01D 2251/104 Ozone
• CPC Class Codes: B01D 2251/106 Peroxides
• CPC Class Codes: B01D 2255/20707 Titanium
• CPC Class Codes: B01D 53/864 Removing carbon monoxide or hydrocarbons
• CPC Class Codes: B01D 53/8668 Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
• CPC Class Codes: B01J 19/123 Ultraviolet light
• CPC Class Codes: B01J 19/127 Sunlight; Visible light
• CPC Class Codes: B01J 19/2415 Tubular reactors
• CPC Class Codes: B01J 19/2475 Membrane reactors
• CPC Class Codes: B01J 2219/00067 Liquid level measurement
• CPC Class Codes: B01J 2219/00144 Sunlight; Visible light
• CPC Class Codes: B01J 2219/00162 controlling the pressure
• CPC Class Codes: B01J 2219/00164 controlling the flow
• CPC Class Codes: B01J 2219/0883 Gas-gas
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 8/009 Membranes, e.g. feeding or removing reactants or products to or from the catalyst bed through a membrane
• CPC Class Codes: C01B 3/38 using catalysts
• CPC Class Codes: C02F 1/325 Irradiation devices or lamp constructions
• CPC Class Codes: C02F 1/4672 by electrooxydation
• CPC Class Codes: C02F 1/722 : Oxidation by peroxides
• CPC Class Codes: C02F 1/725 : by catalytic oxidation
• CPC Class Codes: C02F 1/78 : with ozone C02F1/4672 takes precedence
• CPC Class Codes: C02F 2101/303 : Complexing agents
• CPC Class Codes: C02F 2101/322 : Volatile compounds, e.g. benzene
• CPC Class Codes: C02F 2101/363 : PCB's; PCP's
• CPC Class Codes: C02F 2201/009 : Apparatus with independent power supply, e.g. solar cells, windpower, fuel cells for electrolysis apparatus C02F2201/46165
• CPC Class Codes: C02F 2201/3223 : Single elongated lamp located on the central axis of a turbular reactor
• CPC Class Codes: C02F 2201/328 : Having flow diverters (baffles)
• CPC Class Codes: C02F 2305/10 : Photocatalysts
• CPC Class Codes: Y02A 20/212 : Solar-powered wastewater sewage treatment, e.g. spray evaporation
• CPC Class Codes: Y02P 20/52 : using catalysts, e.g. selective catalysts
• CPC Class Codes: Y02W 10/37 : using solar energy
• CPC Class Codes: Y10S 210/908 : Organic

Abstract

A method and apparatus for mineralizing organic contaminants in water or air provides photochemical oxidation in a two-phase or three-phase boundary system formed in the pores of a TiO₂ membrane in a photocatalytic reactor. In the three-phase system, gaseous (liquid) oxidant, liquid (gaseous) contaminant, and solid semiconductor photocatalyst meet and engage in an efficient oxidation reaction. The porous membrane has pores which have a region wherein the meniscus of the liquid varies from the molecular diameter of water to that of a capillary tube resulting in a diffusion layer that is several orders of magnitude smaller than the closest known reactors. The photocatalytic reactor operates effectively at ambient temperature and low pressures. A packed-bed photoreactor using photocatalyst coated particles is also provided.

Claims

1. An apparatus for oxidizing organic contaminants, comprising:

a substrate having a photocatalytic surface,

a fluid cell in communication with the photocatalytic surface of the substrate, the fluid cell comprising an ultraviolet transmission surface positioned to expose the photocatalytic surface to ultraviolet light, an oxidant inlet, a fluid inlet, and a fluid outlet, wherein the fluid cell is generally flat; and

an ultraviolet light source adjacent to the ultraviolet transmission surface.

2. The apparatus of claim 1, wherein the photocatalyst surface is a porous titanium dioxide surface.

3. The apparatus of claim 1, wherein the photocatalyst surface is a porous titanium dioxide based binary oxide surface.

4. The apparatus of claim 1, wherein the substrate comprises a photocatalyst supported on a plurality of particles.

5. The apparatus of claim 4, wherein the particles are made of glass, silica gel, silica beads, ceramics, metals or fiberglass.

6. The apparatus of claim 3, wherein the titanium dioxide based binary oxide is selected from TiO₂ /SiO₂, TiO₂ /ZrO₂, TiO₂ /SnO₂, TiO₂ /WO₃, TiO₂ /MoO₃, and mixtures thereof.

7. The apparatus of claim 1, wherein the fluid cell further comprises a flow field divider for directing the flow of a contaminant fluid in contact with the photocatalyst surface.

8. The apparatus of claim 1, wherein the fluid cell further comprises a plurality of serpentine dividers positioned in parallel.

9. The apparatus of claim 1, further comprising a plurality of fluid cells positioned in parallel, wherein the ultraviolet light source is positioned between each fluid cell.

10. The apparatus of claim 1, wherein the oxidant inlet is positioned adjacent to the fluid inlet.

11. The apparatus of claim 1, wherein the oxidant inlet comprises an oxidant transmission surface having pores extending therethrough.

12. The apparatus of claim 1, further comprising an oxidant source connected to the oxidant inlet, and an organic contaminant source connected to the fluid inlet.

13. The apparatus of claim 12, wherein the oxidant is selected from oxygen, ozone, hydrogen peroxide, or combinations thereof.

14. The apparatus of claim 11, wherein the oxidant transmission surface is connected to an oxidant source.

15. The apparatus of claim 1, wherein the ultraviolet source exposes the photocatalytic surface to ultraviolet light.

16. The apparatus of claim 12, wherein the oxidant source comprises an electrolytic cell which generates an oxygen stream comprising greater than about 10% by weight of ozone.

18. The apparatus of claim 15, wherein the ultraviolet source is an ultraviolet lamp.

19. The apparatus of claim 15, wherein the ultraviolet source is an ultraviolet lamp which includes the ultraviolet wavelength range of 200-400 nm.

20. The apparatus of claim 1, further comprising a metal catalyst disposed in the photocatalyst.

21. The apparatus of claim 20, wherein the metal catalyst is selected from is selected from Pt group metals, Au group metals, Ir, Ru, Sn, Os, Mo, Zr, Nb, Rh, Ag, Pd, Cu and mixtures thereof.

22. The apparatus of claim 20, wherein the photocatalyst comprises between about 0.01 wt % and about 5 wt % metal catalyst.

23. The apparatus of claim 20, wherein the metal catalyst is selected from platinum group metal oxides, gold group metal oxides, tin oxides, tungsten oxides, iridium oxides, rhodium oxides, ruthenium oxides and mixtures thereof.

43. The apparatus of claim 11, wherein the oxidant transmission surface is the substrate.

44. The apparatus of claim 12, wherein the oxidant is selected from ozone, hydrogen peroxide, and combinations thereof.

45. The apparatus of claim 12, wherein the oxidant is selected from ozone, hydrogen peroxide, and combinations thereof.

17. An apparatus for oxidizing organic contaminants, comprising:

a substrate having a photocatalytic surface,

a fluid cell in communication with the photocatalytic surface of the substrate, the fluid cell comprising an ultraviolet transmission surface positioned to expose the photocatalytic surface to ultraviolet light, an oxident inlet, a fluid inlet, and a fluid outlet, wherein the fluid cell is generally flat; and

an ultraviolet light source adjacent to the ultraviolet transmission surface, wherein the ultraviolet light source is solar light.

24. A reactor for oxidizing organic contaminants comprising:

a porous substrate having a photocatalyst disposed on one surface and pores extending therethrough;

a fluid cell adjacent the photocatalyst surface, the fluid cell comprising a fluid inlet, a fluid outlet, and a ultraviolet transmission surface positioned to expose the porous photocatalyst surface;

an oxidant cell adjacent a second, opposed surface of the porous substrate, the oxidant cell comprising an oxidant inlet;

a second porous substrate having a photocatalyst disposed on one surface, an opposing surface and pores extending therethrough; and

a second fluid cell adjacent to the photocatalyst surface of the second porous substrate, the fluid cell comprising a fluid inlet, a fluid outlet, and a ultraviolet transmission surface positioned to expose the porous photocatalyst surface;

wherein the oxidant cell is adjacent to the opposing surface of the second porous substrate.

25. The apparatus of claim 24, further comprising a plurality of reactors.

26. The apparatus of claim 25, wherein the reactors are positioned in parallel so that the ultraviolet transmission surface of one reactor faces the ultraviolet transmission surface of an adjacent reactor.

27. The apparatus of claim 24, wherein the first and second photocatalyst surfaces comprise titanium dioxide.

28. The apparatus of claim 27, wherein the photocatalyst surfaces comprise a titanium dioxide based binary oxide.

29. The apparatus of claim 28, wherein the titanium dioxide based binary oxide is selected from TiO₂ /SiO₂, TiO₂ /ZrO₂, TiO₂ /SnO₂, TiO₂ /WO₃, TiO₂ /MoO₃, or mixtures thereof.

30. The apparatus of claim 24, further comprising an oxidant source connected to the oxidant inlet, and an organic contaminant source connected to the fluid inlet.

31. The apparatus of claim 30, wherein the oxidant source is selected from oxygen, ozone, hydrogen peroxide, or combinations thereof.

32. The apparatus of claim 29, further comprising an ultraviolet source which exposes the photocatalyst surface to ultraviolet light.

33. The apparatus of claim 30, wherein the oxidant source comprises an electrolytic cell which generates an oxygen stream comprising greater than about 10% by weight of ozone.

34. The apparatus of claim 32, wherein the ultraviolet source is solar light.

35. The apparatus of claim 32, wherein the ultraviolet source is an ultraviolet lamp.

36. The apparatus of claim 31, wherein the ultraviolet source is an ultraviolet lamp which includes the ultraviolet wavelength range of 200-400 nm.

37. The apparatus of claim 24, wherein the fluid inlet directs the organic contaminant toward the photocatalyst surface.

38. The apparatus of claim 24, further comprising a metal catalyst disposed in the photocatalyst.

39. The apparatus of claim 38, wherein the metal catalyst is selected from Pt group metals, Au group metals, Ir, Ru, Sn, Os, Mo, Zr, Nb, Rh, Cu and mixtures thereof.

40. The apparatus of claim 38, wherein the metal catalyst is selected from, Pt--Sn, Pt--Mo, Pt--Ru, Ni--Zr, Pt--Rh, Pt--Ir, Pt--Ru--W, Pt--Ru--Os, Pt--Ru--Sn, Pt--Ni--Ti, Pt--Ni--Zr, Pt--Ni--Nb, Pt--Ni--Ta and mixtures thereof.

41. The apparatus of claim 38, wherein the photocatalyst comprises between about 0.01 wt % and about 5 wt % metal catalyst.

42. The apparatus of claim 38, wherein thc metal catalyst is selected from platinum group metal oxides, gold group metal oxides, tin oxides, tungsten oxides, iridium oxides, rhodium oxides, ruthenium oxides and mixtures thereof.

46. The apparatus of claim 30, wherein the oxidant is selected from ozone, hydrogen peroxide, and combinations thereof.