Visible-light-responsive titanium oxide microparticle dispersion, and process for production thereof
Disclosed are: a visible-light-responsive titanium oxide microparticle dispersion comprising an aqueous dispersion medium and titanium oxide microparticles dispersed therein, and a peroxotitanium component, an iron component and/or a copper component and a tin component, wherein the content of the peroxotitanium component is 0.1 to 20 mass % relative to the titanium oxide content; and a process for producing a visible-light-responsive titanium oxide microparticle dispersion, comprising (1) producing peroxotitanic acid containing a tin compound from a raw material titanium compound, a tin compound and hydrogen peroxide, (2) heating an aqueous solution of peroxotitanic acid containing the tin compound to 80 to 250° C. under a high pressure to produce a titanium oxide microparticle dispersion containing a peroxotitanium component and a tin component, and (3) adding an iron compound and/or a copper compound to the titanium oxide microparticle dispersion to cause a reaction between the iron compound and/or the copper compound with the dispersion.
1. A process for producing a visible-light-responsive titanium oxide microparticle dispersion comprising the steps of:
(1) producing an aqueous solution of peroxotitanic acid containing a tin compound from a raw material titanium compound, a tin compound and a hydrogen peroxide;
(2) heating the aqueous solution of peroxotitanic acid containing the tin compound to 80 to 250° C. under a pressure of 0.01 to 4.5 MPa to produce a titanium oxide microparticle dispersion containing a peroxotitanium component and a tin component; and
(3) adding an iron compound and/or a copper compound to the titanium oxide microparticle dispersion to cause a reaction of the iron compound and/or the copper compound with the dispersion, so as to obtain the visible-light-responsive titanium oxide microparticle dispersion.
2. The process for producing a visible-light-responsive titanium oxide microparticle dispersion according to claim 1 , wherein the obtained visible-light-responsive titanium oxide microparticle dispersion comprises an aqueous dispersion solvent and titanium oxide microparticles dispersed in the aqueous dispersion solvent and further comprises a peroxotitanium component, a tin component, and an iron component and/or a copper component, wherein the content of the peroxotitanium component is 0.1 to 20 wt % based on titanium oxide.
3. The process for producing a visible-light-responsive titanium oxide microparticle dispersion according to claim 2 , wherein the content of the iron component in terms of metal iron is 0.01 to 5 wt % based on titanium oxide.
4. The process for producing a visible-light-responsive titanium oxide microparticle dispersion according to claim 2 , wherein the content of the copper component in terms of metal copper is 0.01 to 5 wt % based on titanium oxide.
5. The process for producing a visible-light-responsive titanium oxide microparticle dispersion according to claim 2 , wherein the content of the tin component in terms of molar ratio (Ti/Sn) between the tin component and titanium oxide is from 1 to 1000.
6. The process for producing a visible-light-responsive titanium oxide microparticle dispersion according to claim 2 , wherein the titanium oxide microparticles have a 50% cumulative distribution diameter (D 50 ) measured by a dynamic scattering method of not more than 50 nm.