Photocatalyst and process for purifying gas effluent by photocatalytic oxidation

• US 20060011945A1
• Filed: 10/28/2002
• Published: 01/19/2006
• Est. Priority Date: 10/29/2001
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Sicat, Universite Louis Pasteur De Strasbourg
• Original Assignee: Centre National De La Recherche Scientifique, Sicat, Universite Louis Pasteur De Strasbourg
• Inventors: Pham-Huu, Cuong, Pham-Huu, Charlotte, Spitzer-Keller, Valerie, Ledoux, Marc J., Garin, Francois, Bernhardt, Pierre
• Granted Patent: US 7,435,702 B2
• Time in Patent Office: Days
• US Class Current: 257/200
• CPC Class Codes: A61L 9/205 using a photocatalyst or photosensitiser
• CPC Class Codes: B01D 2255/20707 Titanium
• CPC Class Codes: B01D 2255/20776 Tungsten
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 2257/708 Volatile organic compounds V.O.C.'s
• CPC Class Codes: B01D 2257/91 Bacteria; Microorganisms
• CPC Class Codes: B01D 53/8668 Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
• CPC Class Codes: B01J 23/30 Tungsten
• CPC Class Codes: B01J 27/224 Silicon carbide
• CPC Class Codes: B01J 35/0006 Catalysts containing parts with different compositions
• CPC Class Codes: B01J 35/002 Catalysts characterised by their physical properties
• CPC Class Codes: B01J 35/19 Catalysts containing parts with different compositions
• CPC Class Codes: B01J 35/30 characterised by their physical properties

Abstract

The photocatalyst based on a composite WO₃—SiC/TiO₂ semiconductor and subjected to radiation whose wavelength is at least partly less than 400 nm gives photocatalytic oxidation of volatile organic compounds and leads to their total mineralisation into CO₂ and H₂O. The process for the photocatalytic purification of industrial, agricultural or domestic gaseous effluent may be conducted at room pressure and temperature. Its conversion rate is high and stable.

Claims

1. Photocatalyst containing at least two coupled semiconductor compounds, characterized in that one of said semiconductors is titanium dioxide TiO₂, and the other is silicon carbide, SiC, and in that it also contains tungsten trioxide, WO₃.

2. Photocatalyst according to claim 1, characterized in that it contains between 10 and 60%, preferably between 15 and 25% SiC (weight percentages).

3. Photocatalyst according to either of claims 1 or 2, characterized in that it contains a quantity of WO₃ corresponding to 10 to 50% of a theoretical monolayer relative to the BET specific surface area of TiO₂ particles.

4. Photocatalyst according to any of claims 1 to 3, characterized in that it contains TiO₂ having a BET specific surface area of between 40 and 60 m²/g, and in that it contains between 1 and 5%, preferably between 1.5 and 4% WO₃ (weight percentages).

5. Photocatalyst according to any of claims 1 to 4, characterized in that it contains SiC having a BET specific area of between 1 and 600 m²/g, preferably between 10 and 100 m²/g.

10. Use of a photocatalyst according to any of claims 1 to 5, in a process for purifying effluent containing volatile organic compounds by photocatalytic oxidation, said process comprising:

a) adding the effluent to a reactor containing said photocatalyst,

b) irradiating the photocatalyst with radiation of which at least part of the light power is emitted along a wavelength of less than 400 nm and preferably less than 360 nm, so that at least part of the volatile organic compounds contained in said effluent is decomposed by oxidation;

c) evacuating the gaseous reaction mixture from the reactor.

11. Use of a photocatalyst according to any of claims 1 to 5 in a process for inactivating microorganisms contained in a gaseous flow by photocatalytic oxidation, said process comprising:

a) adding a gaseous flow to a reactor containing said photocatalyst,

b) irradiating the photocatalyst by radiation of which at least part of the light power is emitted along a wavelength of less than 400 nm and preferably less than 360 nm, so that at least part of the microorganisms contained in said gas flow are decomposed by oxidation,

d) evacuating the gas flow from the reactor.

12. Use according to either of claims 10 or 11, characterized in that said process is conducted at a temperature of between 15 and 30°

C.

13. Use according to any of claims 10 to 12, characterized in that said process is conducted at atmospheric pressure.

14. Use according to any of claims 10 to 13, characterized in that said light power is derived at least in part from sun radiation.

6. Process for preparing a mixed WO₃—

SiC/TiO₂ photocatalyst, comprising at least a first step during which the TiO₂ and SiC are simultaneously deposited on a carrier, and a second step during which the SiC/TiO₂ deposit is impregnated with a solution containing at least one WO₃ precursor.

7. Process according to claim 6, characterized in that during the first step a first suspension is prepared from TiO₂ powder and a second suspension from SiC powder, the two suspensions are mixed, poured onto a carrier and the solvent is evaporated.

8. Process according to either of claims 6 and 7, characterized in that the WO₃ precursor solution is an aqueous solution of (NH₄)₁₀W₁₂O₄₁.5H₂O.

9. Process according to any of claims 6 to 8, characterized in that it also comprises a third step, during which calcination is conducted at a temperature of preferably between 300 and 500°

C.