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. A method of producing an aqueous ultrafine titania sol having (1) a pH >10, (2) a solids component having at least 50% by weight of anatase crystal form of TiO 2 particles and less than 50% by weight of at least one inorganic oxide other than TiO 2 , and (3) an aqueous component comprising a mixture of a weak base having a pKa <10.5 and a strong base having a pKa >10.5, wherein the anatase crystal form of TiO 2 particles are present in the aqueous titania sol at a mass fraction >0.25 and/or a volume fraction >0.25, comprising the step of processing the aqueous ultrafine titania sol via media milling until the anatase crystal form of TiO 2 particles therein have a particle size <1 μm.
2. The method of claim 1 , wherein 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 method of claim 1 , wherein the anatase crystal form of TiO 2 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 method of claim 1 , wherein the weak base is an alkanolamine.
5. The method of claim 1 , wherein the strong base is a quaternary alkylammonium hydroxide.
6. The method of claim 1 , wherein the aqueous ultrafine titania sol has a viscosity <100 cp.
7. The method of claim 1 , wherein the aqueous ultrafine titania sol has a surface tension <70 mN/m.
8. The method of claim 1 , wherein the aqueous ultrafine titania sol has a flashpoint >100° C.