Transparent, stable titanium dioxide sols
AssigneeMillennium Inorganic Chemicals, Inc.
InventorsGuoyi Fu, Billiejo M. Monk, Robert McIntyre
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Abstract
A method of preparing stable, transparent photocatalytic titanium dioxide sots is disclosed which involves thermal treatment of a suspension of amorphous titanium dioxide in the presence of certain alpha-hydroxy acids. The sots comprise titanium dioxide particles in the anatase form having a crystallite size less than about 10 nm and exhibit excellent stability and transparency at basic, neutral, and acid pH.
Claims22
A method for preparing a stable, transparent photocatalytic titanium dioxide sol, comprising:
- (i) providing a solution comprising a titanium containing compound;
- (ii) precipitating hydrous titanium dioxide from said solution of a titanium containing compound;
- (iii) forming an aqueous dispersion of said precipitated hydrous titanium dioxide;
- and
- (iv) mixing said aqueous dispersion in the presence of one or more alpha-hydroxy carboxylic acids at a temperature between about 70° C. and about 150° C. for a period of time between about three hours and about 3 days;
- with the proviso that said one or more alpha-hydroxy carboxylic acids are essentially free of glycolic acid;
- thereby providing a sol of titanium dioxide which is stable and transparent at every pH throughout the pH range of 2 to 12;
- said sol comprising crystallites of titanium dioxide having an average particle size of less than about 10 nm, the majority of said crystallites being in anatase form.
A method for preparing a stable, transparent photocatalytic titanium dioxide sol, comprising:
- (i) providing a solution comprising a titanium containing compound;
- (ii) precipitating hydrous titanium dioxide from said solution of a titanium containing compound;
- (iii) forming an aqueous dispersion of said precipitated hydrous titanium dioxide;
- (iv) mixing said aqueous dispersion in the presence of one or more alpha-hydroxy carboxylic acids at a temperature between about 70° C. and about 150° C. for a period of time between about three hours and about 3 days;
- thereby providing a sol of titanium dioxide which is stable and transparent at every pH throughout the pH range of 2 to 12;
- said sol comprising crystallites of titanium dioxide having an average particle size of less than about 10 nm, the majority of said crystallites being in anatase form;
- with the proviso that step (iv) is carried out without an intervening neutralization step between steps (iii) and (iv).
Dependencies are inferred from the claim text.