Titanium oxide photocatalyst, process for producing the same and application

• US 20050227008A1
• Filed: 03/20/2003
• Published: 10/13/2005
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: OSAKA Titanium Technologies Co., Ltd.
• Inventors: Yao, Tadashi, Watanabe, Munetoshi, Takahashi, Michiyasu, Ogasawara, Tadashi, Kajimura, Haruhiko, Masaki, Yasuhiro, Shimosaki, Shiji, Nishihara, Katsuhiro, Nagaoka, Sadanobu, Oda, Kouji, Okada, Katsumi
• Granted Patent: US 7,521,133 B2
• Time in Patent Office: Days
• US Class Current: 427/372.200
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 53/8609 Sulfur oxides
• CPC Class Codes: B01D 53/8612 Hydrogen sulfide
• CPC Class Codes: B01D 53/8628 Processes characterised by a specific catalyst
• CPC Class Codes: B01D 53/8634 Ammonia
• CPC Class Codes: B01D 53/8662 Organic halogen compounds
• CPC Class Codes: B01J 21/063 Titanium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 23/18 Arsenic, antimony or bismuth
• CPC Class Codes: B01J 27/132 with chromium, molybdenum, tungsten or polonium
• CPC Class Codes: B01J 27/135 with titanium, zirconium, hafnium, germanium, tin or lead
• CPC Class Codes: B01J 35/002 Catalysts characterised by their physical properties
• CPC Class Codes: B01J 35/004 Photocatalysts
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 37/0238 via the gaseous phase-sublimation
• CPC Class Codes: B01J 37/22 Halogenating

Abstract

Titanium oxide-based photocatalysts which contain a metal halide in titanium oxide and which are prepared from titanium oxide and/or its precursor, which may optionally be heat treated, by contact with a reactive gas containing a metal halide of the formula MX_n or MOX_n (wherein M=a metal, X=a halogen, and n=an integer) with heating stably develop a high photocatalytic activity with visible light irradiation. The photocatalysts may subsequently be stabilized by contact with water or by heat treatment, and/or promoted by contact with a heteropoly acid and/or an isopoly acid so as to include a metal complex in the titanium oxide. Photocatalysts prepared in this manner exhibit novel ESR features. The present invention also provides methods for preparing these photocatalysts, a photocatalyst dispersion and a photocatalytic coating fluid containing such a photocatalyst, and photocatalytic functional products and methods for their manufacture using the photocatalyst.

Claims

1. A titanium oxide-based photocatalyst which is characterized by containing an additional metal compound in titanium oxide and developing a photocatalytic activity by irradiation with visible light.

2. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the additional metal compound is at least one compound selected from a metal halide, a metal complex, a metal hydroxide, and a metal oxide.

3. A titanium oxide-based photocatalyst as set forth in claim 2 wherein the metal complex is one or both of a heteropoly acid and an isopoly acid.

4. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the content of the additional metal compound as a metal is at least 0.1 mass % and at most 300 mass % based on the titanium oxide.

6. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the metal is at least one selected from Ti, Si, V, Sn, Sb, W, Nb, Bi, P, Mo, Cs, Ge, As, and Ce.

7. A titanium oxide-based photocatalyst as set forth in claim 2 wherein the halide is a chloride.

11. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the titanium oxide has absorptivity for visible light.

12. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the titanium oxide has oxygen defects.

13. A titanium oxide-based photocatalyst as set forth in claim 1 wherein the primary crystal structure of the titanium oxide is anatase.

18. A photocatalytic functional product characterized by comprising a substrate having a titanium oxide-based photocatalyst as set forth in claim 1 deposited on a surface of the substrate.

19. A photocatalytic functional product characterized by comprising a substrate having a film which comprises a titanium oxide-based photocatalyst as set forth in claim 1 and a binder component formed on a surface of the substrate, the content of the photocatalyst in the film being 5-95 mass %.

20. A photocatalyst dispersion characterized by comprising a titanium oxide-based photocatalyst as set forth in claims 1 dispersed in a solvent.

21. A photocatalyst dispersion as set forth in claim 20 wherein the photocatalyst has an average particle diameter of at most 500 nm.

22. A photocatalytic coating fluid characterized by comprising a titanium oxide-based photocatalyst as set forth in claim 1 in a solvent.

23. A photocatalytic coating fluid characterized by comprising a titanium oxide-based photocatalyst as set forth in claim 1 and a binder in a solvent, the content of the titanium oxide-based photocatalyst being in the range of 5-95 mass % based on the total nonvolatile content in the fluid.

24. A photocatalytic coating fluid characterized in that it is prepared using a photocatalyst disperison as set forth in claim 21.

25. A method for the manufacture of a photocatalytic functional product characterized by applying a coating fluid as set forth in claim 22 to a surface of a substrate.

26. A method for the preparation of a photocatalytic coating fluid characterized by mixing a binder with a photocatalyst dispersion as set forth in claim 21.

5. A titanium oxide-based photocatalyst which is characterized by containing a metal halide in titanium oxide and having a thermal desorption spectrum in which a peak of a molecular ion or a fragment ion of a halogen-containing substance appears at a temperature of 623 K or higher.

8. A titanium oxide-based photocatalyst developing a photocatalytic activity by irradiation with visible light, which is characterized by having an ESR spectrum measured at a temperature of at least 5 K in which a peak is observed in the range in which the g value is 1.950-2.030 when irradiated with visible light, that peak not being substantially observed in the dark.

10. A titanium oxide-based photocatalyst as set forth in claim 8 which has an ESR spectrum measured at a temperature lower than 77 K in which a peak appears in the range in which the g value is 1.986-1.994.

9. A titanium oxide-based photocatalyst developing a photocatalytic activity by irradiation with visible light, which is characterized by having an ESR spectrum measured at room temperature in a substantially oxygen-free atmosphere in which the highest peak observed in the range in which the g value is 1.950-2.030 when irradiated with visible light has a peak intensity with a half life of at least 3 minutes after the irradiation with visible light is stopped.

14. A method for the preparation of a titanium oxide-based photocatalyst characterized in that titanium oxide and/or its precursor is brought into contact with a reactive medium containing a metal halide of the formula MX_n or MOX_n (wherein M=a metal, X=a halogen, and n=an integer).

15. A method for the preparation of a titanium oxide-based photocatalyst as set forth in claim 14 which further includes subjecting the titanium oxide and/or its precursor to contact with water and/or heat treatment after the contact with the reactive medium.

16. A method for the preparation of a titanium oxide-based photocatalyst as set forth in claim 14 which further includes performing contact with a heteropoly acid and/or an isopoly acid after the contact with the reactive gas, or after subsequent contact with water and/or heat treatment.

17. A titanium oxide-based photocatalyst prepared by a method as set forth in claim 14.

30. A method as set forth in claim 15 wherein the heat treatment is carried out in a temperature range of 373-873 K.

31. A method as set forth in claim 14 wherein the metal halide is at least one compound selected from TiCl4, VOCl₃, SnCl₄, SbCl₅, SiCl₄, WCl₆, and BiCl₃.

32. A method as set forth in claim 31 wherein the metal halide is TiCl₄.

33. A method as set forth in claim 14 which further includes subjecting the titanium oxide and/or its precursor or the substrate to heat treatment in a temperature range of 323-823 K or to wet processing prior to the contact with the reactive gas.

34. A method as set forth in claim 14 wherein the contact with the reactive gas is performed in a temperature range of 323-873 K.

35. A method as set forth in claim 14 wherein the reactive medium is gaseous and its base gas is a nonoxidizing gas.

36. A method as set forth in claim 35 wherein the base gas comprises hydrogen and/or nitrogen.

37. A method as set forth in claim 14 wherein the titanium oxide and/or its precursor is prepared via a step of neutralizing at least one compound selected from titanium tetrachloride, titanium sulfate, and titanyl sulfate with a nitrogen-containing base.

27. A method for the manufacture of a photocatalytic functional product characterized by depositing titanium oxide and/or its precursor on a surface of a substrate followed by bringing the surface into contact with a reactive medium containing a metal halide of the formula MX_n or MOX_n (wherein M=a metal, X=a halogen, and n=an integer).

28. A method as set forth in claim 27 which further includes subjecting the surface of the substrate to contact with water and/or heat treatment after the contact with the reactive medium.

29. A method as set forth in claim 27 which further includes bringing the surface of the substrate into contact with a heteropoly acid and/or an isopoly acid after the contact with the reactive gas, or after subsequent contact with water and/or heat treatment.