Stable sub-micron titania sols
View Patent ↗The present invention is directed to compositions and processes for the production of stable, alkaline, high solids, low viscosity, low surface tension, low flammability, sub-micron titania sols that have minimal offensive odor and methods of their use. Compositions of the present invention include, for example, mixtures of strong and weak organic bases used as dispersants to stabilize the titania sols. The dispersant mixtures have been found to result in relatively high titania solids content, low surface tension, low viscosity suspensions that are low in flammability. Sols produced according to the present invention can be used, for example, in catalytic applications such as catalyst supports for diesel emission control, or in pollutant photocatalyst applications in which it is desirable to have the titania in sol form.
1. An aqueous titania sol, comprising:
a solids component having at least 50% by weight of anatase TiO 2 particles and less than 50% by weight of at least one inorganic oxide other than TiO 2 ; and
an aqueous mixture of a weak base having a pK a <10.5, and a strong base having a pK a >10.5; and
wherein the aqueous titania sol has a pH>10, and the anatase TiO 2 particles (i) comprise sizes<1 μm, and (ii) are present in the aqueous titania sol at a mass fraction and/or volume fraction>0.25.
2. The aqueous titania sol of claim 1 , wherein the at least one inorganic oxide other than TiO 2 is selected from the group consisting of oxides of silica, tungsta, alumina, ceria, copper, iron, manganese, vanadia, and combinations thereof.
3. The aqueous titania sol of claim 1 , wherein the anatase titania particles have a surface area in excess of 50 m 2 /g, and a pore volume in excess of 0.10 cm 3 /g.
4. The aqueous titania sol of claim 1 , wherein the weak base is an alkanolamine.
5. The titania sol of claim 1 , wherein the strong base is a quaternary alkylammonium hydroxide.
6. An aqueous titania sol, comprising:
a solids component having at least 50% by weight of anatase TiO 2 particles and less than 50% by weight of at least one inorganic oxide selected from the group consisting of oxides of silica, tungsta, alumina, ceria, copper, iron, manganese, vanadia, and combinations thereof; and
an aqueous mixture of at least a weak base having a pK a <10.5, and a strong base having a pK a >10.5; and
wherein the aqueous titania sol has a pH>10 and a viscosity<100 cp, and the anatase TiO 2 particles (i) comprise sizes<1 μm and (ii) are present in the aqueous sol at a mass fraction and/or volume fraction>0.25.
7. The aqueous titania sol of claim 6 , wherein the anatase titania particles have a surface area in excess of 50 m 2 /g, and have a pore volume in excess of 0.10 cm 3 /g.
8. The aqueous titania sol of claim 6 , wherein the weak base is an alkanolamine.
9. The titania sol of claim 6 , wherein the strong base is a quaternary alkylammonium hydroxide.
10. The aqueous titania sol of claim 6 having a surface tension<70 mN/m.
11. The aqueous titania sol of claim 6 having a flashpoint>100° C.
12. An aqueous titania sol, comprising:
a solids component having at least 50% by weight of anatase TiO 2 particles and less than 50% by weight of at least one inorganic oxide other than TiO 2 ; and
an aqueous mixture of an alkanolamine base having a pK a <10.5, and a quaternary alkylammonium hydroxide base having a pK a >10.5; and
wherein the aqueous titania sol has a pH>10, and the anatase TiO 2 particles (i) comprise sizes<1 μm and (ii) are present in the aqueous sol at a mass fraction and/or volume fraction>0.25.
13. The aqueous titania sol of claim 12 , wherein the at least one inorganic oxide other than TiO 2 is selected from the group consisting of oxides of silica, tungsta, alumina, ceria, copper, iron, manganese, vanadia, and combinations thereof.
14. The aqueous titania sol of claim 12 , wherein the anatase titania particles have a surface area in excess of 50 m 2 /g, and have a pore volume in excess of 0.10 cm 3 /g.
15. The aqueous titania sol of claim 12 having a viscosity<100 cp.
16. The aqueous titania sol of claim 12 having a surface tension<70 mN/m.
17. The aqueous titania sol of claim 12 having a flashpoint>100° C.