Preparation of anatase titanium dioxide
AssigneeTioxide Specialties Limited
InventorDominic G. Meina
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Abstract
a process for the preparation of anatase titanium dioxide having a high surface area and suitable as a catalyst support is described. The process involves forming an aqueous dispersion of titanium dioxide at a pH less than 3 and preferably less than 1 and depositing a first coating of a hydrous oxide of an element which acts as a rutilisation inhibitor and a second coating of a phosphate on the particles of titanium dioxide. The product of the process has a high surface area which is retained on heating for long periods at high temperature. A novel product is particulate anatase titanium dioxide which has been coated with a rutile inhibitor and a phosphate, has a specific surface area of at least 50 m.sup.2 /g and retains at least 80% of its surface area after heating at 800.degree. C. for 7 days.
Claims24
A process for preparing anatase titanium dioxide having a high surface area comprising the steps of:
- a) preparing hydrous titania in the anatase form by hydrolysis of a titanium compound selected from the group consisting of titanyl sulphate and titanium orthoesters,
- b) forming an aqueous dispersion of said hydrous titania in the anatase form at a Ph of not more than 3,
- c) adding to the dispersion a hydrolyzable water soluble salt of a rutile inhibitor,
- d) increasing the Ph of the dispersion to precipitate a first coating on the surface of said hydrous titania particles comprising the rutile inhibitor in the form of a hydrous oxide;
- and
- e) adding a water soluble phosphate to form a second coating on the said hydrous titania particles comprising a phosphate.
Particulate anatase titanium dioxide the particles of which have a first coating comprising a hydrous oxide of a rutile inhibitor and a second coating of a phosphate, the coated particles having a specific surface area as determined by BET nitrogen desorption measurement of at least 50 meters squared per gram, at least 80 per cent of said specific surface area being retained after heating the coated particles at 800.degree. C. for 7 days.
Dependencies are inferred from the claim text.