Method for producing tungsten trioxide powder for photocatalyst, tungsten trioxide powder for photocatalyst, and photocatalyst product
View Patent ↗A method for producing a tungsten trioxide powder for a photocatalyst according to the present invention is characterized by comprising a sublimation step for obtaining a tungsten trioxide powder by subliming a tungsten metal powder or a tungsten compound powder by using inductively coupled plasma process in an oxygen atmosphere, and a heat treatment step for heat-treating the tungsten trioxide powder obtained in the sublimation step at 300° C. to 1000° C. for 10 minutes to 2 hours in an oxidizing atmosphere. A tungsten trioxide powder which is obtained by the method for producing a tungsten trioxide powder for a photocatalyst according to the present invention has excellent photocatalytic performance under visible light.
1. A method for producing a tungsten trioxide powder comprising:
subliming a tungsten metal powder or a tungsten compound powder by at least one of the following processes in an oxygen atmosphere to produce a tungsten oxide powder:
an inductively coupled plasma process,
an arc discharge process,
a laser process, and
an electron beam process; and
heat-treating the tungsten oxide powder at 300° C. to 1000° C. for 10 minutes to 2 hours in an oxidizing atmosphere to provide the tungsten trioxide powder.
2. The method according to claim 1 , wherein the tungsten metal powder or the tungsten compound powder has an average particle size of 0.1 μm to 100 μm.
3. The method according to claim 1 , wherein the sublimation in the oxygen atmosphere is achieved by an inductively coupled plasma process and the tungsten metal powder or the tungsten compound powder is blown into a plasma generated in the oxygen atmosphere together with a carrier gas.
4. The method according to claim 1 , wherein the sublimation in the oxygen atmosphere is achieved by an inductively coupled plasma process and a dispersion in which the tungsten metal powder or the tungsten compound powder is dispersed in a liquid dispersion medium having an oxygen atom in a molecule is blown into a plasma generated in the oxygen atmosphere.
5. The method according to claim 4 , wherein the liquid dispersion medium having an oxygen atom in a molecule comprises 51 vol % or more of at least one of water and alcohol.
6. A tungsten trioxide powder obtained by the method according to claim 1 , wherein the tungsten trioxide powder has a BET specific surface area of 8.2 m 2 /g to 820 m 2 /g and has at least two types of crystal structures selected from the group consisting of monoclinic, orthorhombic and triclinic.
7. The tungsten trioxide powder according to claim 6 , wherein the tungsten trioxide powder has a particle size distribution obtained by image analysis, (D90-D10)/D50, of 0.3 to 2.
8. The tungsten trioxide powder according to claim 6 , wherein the tungsten trioxide powder has has an average particle size converted from a BET specific surface area of 1 nm to 100 nm.
9. A composition comprising 90 mass % to 100 mass % of the tungsten trioxide powder according to claim 6 .
10. A photocatalyst product comprising a substrate and a photocatalyst covering layer formed on a surface of the substrate, wherein the photocatalyst covering layer is formed by binding the composition according to claim 9 with an inorganic or organic-inorganic complex binder.
11. The photocatalyst product according to claim 10 , wherein the photocatalyst covering layer has a thickness of 0.1 μm to 3 μm.
12. The photocatalyst product according to claim 10 , wherein the photocatalyst covering layer contains 10 vol % or more of the composition.
13. The photocatalyst product according to claim 10 , wherein the photocatalyst covering layer has a transmittance of 50% or more for light having a wavelength of 550 nm.
14. The method according to claim 1 , comprising subliming a tungsten metal powder.
15. The method according to claim 1 , comprising subliming a tungsten compound powder.
16. The method according to claim 1 , wherein the tungsten trioxide powder produced has a BET specific surface area of 8.2 m 2 /g to 820 m 2 /g and has at least two types of crystal structures selected from the group consisting of monoclinic, orthorhombic and triclinic.
17. The method according to claim 1 , wherein the tungsten trioxide powder produced has a particle size distribution obtained by image analysis, (D90-D10)/D50, of 0.3 to 2.
18. The method according to claim 1 , wherein the tungsten trioxide powder produced wherein the tungsten trioxide powder produced has an average particle size converted from a BET specific surface area of 1 nm to 100 nm.
19. The method according to claim 1 ,
wherein the tungsten trioxide powder produced has a BET specific surface area of 8.2 m 2 /g to 820 m 2 /g and has at least two types of crystal structures selected from the group consisting of monoclinic, orthorhombic and triclinic;
wherein the tungsten trioxide powder produced has a particle size distribution obtained by image analysis, (D90-D10)/D50, of 0.3 to 2; and
wherein the tungsten trioxide powder produced wherein the tungsten trioxide powder produced has an average particle size converted from a BET specific surface area of 1 nm to 100 nm.
20. A method for producing a tungsten trioxide powder comprising:
subliming a tungsten metal powder or a tungsten compound powder by an inductively coupled plasma process in an oxygen atmosphere wherein a dispersion in which the tungsten metal powder or the tungsten compound powder is dispersed in a liquid dispersion medium having an oxygen atom in a molecule is blown into a plasma generated in the oxygen atmosphere to produce a tungsten trioxide powder; and
heat-treating the tungsten trioxide powder at 300° C. to 1000° C. for 10 minutes to 2 hours in an oxidizing atmosphere,
wherein the liquid dispersion medium having an oxygen atom in a molecule comprises 51 vol % or more of at least one alcohol selected from the group consisting of methanol, ethanol, 1-propanol and 2-propanol.