Photocatalyst, process for producing the same and photocatalyst coating composition comprising the same

• US 6,730,630 B2
• Filed: 10/18/2001
• Issued: 05/04/2004
• Est. Priority Date: 10/20/2000
• Status: Expired due to Fees

• Current Assignee: Sumitomo Chemical Company Limited
• Original Assignee: Sumitomo Chemical Company Limited
• Inventors: Ando, Hiroyuki, Okusako, Kensen
• Primary Examiner(s): Bell, Mark L.
• Assistant Examiner(s): Hailey, Patricia L
• Application Number:
  US09/978,800
• Publication Number:
  US 20020077251A1
• Time in Patent Office: 929 Days
• Field of Search: 502/350, 502/308, 502/309, 502/351, 428/403, 423/610
• US Class Current: 502/350
• CPC Class Codes: B01J 21/06 Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 21/063 Titanium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 23/06 of zinc, cadmium or mercury
• CPC Class Codes: B01J 23/10 of rare earths
• CPC Class Codes: B01J 23/20 Vanadium, niobium or tantalum
• CPC Class Codes: B01J 23/30 Tungsten
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 35/40 characterised by dimensions, e.g. grain size in a colloidal state B01J35/23; crystallite size B01J35/77
• CPC Class Codes: B01J 35/60 characterised by their surface properties or porosity
• CPC Class Codes: B01J 35/613 10-100 m2/g
• CPC Class Codes: B01J 35/615 100-500 m2/g
• CPC Class Codes: B01J 37/10 in the presence of water, e.g. steam
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/047 Titanium dioxide
• CPC Class Codes: C01G 33/00 Compounds of niobium
• CPC Class Codes: C01G 41/02 Oxides; Hydroxides
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/84 by UV- or VIS- data
• CPC Class Codes: C01P 2002/85 by XPS, EDX or EDAX data
• CPC Class Codes: C01P 2004/64 : Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/84 : one phase coated with the other
• CPC Class Codes: C01P 2006/12 : Surface area
• CPC Class Codes: Y10T 428/2991 : Coated

Abstract

A photocatalyst is provided, which comprises a titanium oxide and a metal-containing compound other than titanium oxide on the surface of the titanium oxide, wherein the metal-containing compound is a metal oxide having an acid site and the photocatalyst has a BET specific surface area of about 55 m²/g or larger, or wherein the metal-containing compound is a basic metal-containing compound and the photocatalyst has an anatase-crystalline structure and an anatase-crystalline size of about 10 nm or larger. The photocatalyst shows sufficiently high photocatalytic activities by irradiation of visible light.

Claims

1. A photocatalyst comprising a titanium oxide and a metal-containing compound other than titanium oxide on the surface of the titanium oxide, wherein the metal-containing compound is a metal oxide having an acid site and the photocatalyst has a BET specific surface area of about 55 m²/g or larger, or wherein the metal-containing compound is a basic metal-containing compound and the photocatalyst has an anatase-crystalline structure and an anatase-crystalline size of about 10 nm or larger;

and

wherein the photocatalyst has index X of about 0.2 or more, index X being calculated by equation (I);

2. The photocatalyst according to claim 1, wherein the photocatalyst contains the metal-containing compound in an amount of about 0.05% by mol in terms of the metal element of the compound, based on titanium in the photocatalyst.

3. The photocatalyst according to claim 1, wherein the metal-containing compound is a metal oxide having an acid site and the photocatalyst has a BET specific surface area of about 55 m²/g or larger.

4. The photocatalyst according to claim 3, wherein the photocatalyst has a BET specific surface area of about 300 m²/g or smaller.

5. The photocatalyst according to claim 3 or 4, wherein the photocatalyst has index Y of about 0.05 or more, index Y being calculated by equation (II):

6. The photocatalyst according to claim 1, wherein the metal-containing compound is a basic metal-containing compound and the photocatalyst has an anatase-crystalline structure and an anatase-crystalline size of about 10 nm or larger.

7. The photocatalyst according to claim 6, wherein the basic metal-containing compound is at least one member selected from the group consisting of oxides, hydrides and carbonates, of alkali metal, alkaline-earth metal, rare earth element or zinc.

8. The photocatalyst according to claim 6 or 7, wherein the photocatalyst has index Z of about 0.8 and more, which is calculated by equation (III):

 

Z=F/E 

 

(III)

wherein E represents a BET specific surface area (m²/g) of the photocatalyst and F represents a CO₂ adsorption amount (μ

mol/g) of the photocatalyst.

9. A process for producing the photocatalyst as claimed in claims 1 or 2, which comprises the steps of allowing a titanium oxide to come in contact with a solution or slurry of a metal-containing compound other than titanium oxide and/or a solution or slurry of a compound which makes the metal-containing compound by heating;

and heating the resulting titanium oxide, to obtain a photocatalyst.

10. The process for producing a photocatalyst according to claim 9, wherein the titanium oxide has an anatase-crystalline structure.

11. The process for producing a photocatalyst according to claim 9, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

12. The process for producing a photocatalyst according to claim 9, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

13. The process for producing a photocatalyst according to claim 12, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

14. A process for producing the photocatalyst as claimed claims 1 or 2, which comprises the steps of putting in a sealed-container, a titanium oxide and at least one compound selected from the group consisting of metal-containing compound and a compound which makes the metal-containing compound by heating;

heating and evaporating the compound; and

allowing the compound to adhere to the surface of the titanium oxide, to obtain a photocatalyst.

15. The process for producing a photocatalyst according to claim 14, wherein the titanium oxide has an anatase-crystalline structure.

16. The process for producing a photocatalyst according to claim 14, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

17. The process for producing a photocatalyst according to claim 14, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

18. A process for producing the photocatalyst as claimed in claims 1 or 2, which comprises the steps of placing a metal-containing compound on a titanium oxide, and treating the resulting titanium oxide having the metal-containing compound thereon with steam or carbon dioxide gas, to obtain a photocatalyst.

19. The process for producing a photocatalyst according to claim 18, wherein the titanium oxide has an anatase-crystalline structure.

20. The process for producing a photocatalyst according to claim 18, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

21. A photocatalyst coating composition comprising the photocatalyst as claimed in claims 1 or 2, and a solvent.

22. A process for producing the photocatalyst as claimed in claim 1, which comprises the steps of allowing a titanium oxide to come in contact with a solution or slurry of a metal-containing compound other than titanium oxide and/or a solution or slurry of a compound which makes the metal-containing compound by heating;

and heating the resulting titanium oxide, to obtain a photocatalyst.

23. The process for producing a photocatalyst according to claim 22, wherein the titanium oxide has an anatase-crystalline structure.

24. The process for producing a photocatalyst according to claim 22, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

25. The process for producing a photocatalyst according to claim 22, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

26. A process for producing the photocatalyst as claimed in claim 1, which comprises the steps of putting in a sealed-container, a titanium oxide and at least one compound selected from the group consisting of metal-containing compound and a compound which makes the metal-containing compound by heating;

heating and evaporating the compound; and

allowing the compound to adhere to the surface of the titanium oxide, to obtain a photocatalyst.

27. The process for producing a photocatalyst according to claim 26, wherein the titanium oxide has an anatase-crystalline structure.

28. The process for producing a photocatalyst according to claim 26, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

29. The process for producing a photocatalyst according to claim 26, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

30. A process for producing the photocatalyst as claimed in claim 1, which comprises the steps of placing a metal-containing compound on a titanium oxide, and treating the resulting titanium oxide having the metal-containing compound thereon with steam or carbon dioxide gas, to obtain a photocatalyst.

31. The process for producing a photocatalyst according to claim 30, wherein the titanium oxide has an anatase-crystalline structure.

32. The process for producing a photocatalyst according to claim 30, wherein the titanium oxide is obtained by a process comprising the steps of reacting a titanium compound with a base to obtain a reaction product at a temperature of about 60°

C. or lower; and

calcining the reaction product to obtain a titanium oxide.

33. The process for producing a photocatalyst according to claim 30, wherein the titanium oxide is obtained by a process comprising the steps of calcining titanium oxysulfate in the presence of oxygen.

34. A photocatalyst coating composition comprising the photocatalyst as claimed in claim 1 and a solvent.