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 sols 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.
Claims25
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 and recovering and washing said precipitated hydrous titanium dioxide with deionized water;
- (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. in a hydrothermal reaction zone 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:
- providing a solution comprising a titanium containing compound;
- (ii) precipitating hydrous titanium dioxide from said solution of a titanium containing compound and recovering and washing said precipitated hydrous titanium dioxide with deionized water;
- (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. in a hydrothermal reaction zone 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).
A stable, transparent sol comprising from about 1 to about 10% by weight photocatalytic titanium dioxide particles having an average crystallite size between about 1 nm and about 10 nm, the majority of said crystallites being in the anatase form, wherein said sol is both stable and transparent at acidic, neutral, and basic pH.
Dependencies are inferred from the claim text.