Abstract: Method of hardening powdered titania (titanium dioxide) so as to make it attrition-resistant and to enhance its properties as a catalyst carrier. The method involves thoroughly dispersing powdered titanium dioxide in water, removing the excess water, drying and then calcining the product at a temperature between 650.degree.C and 900.degree.C. Preferably a large excess of water is used, at least 37% to effect dispersion; and dispersion may be aided by use of a surfactant, a water soluble organic compound or a highly polar inorganic compound. The excess water may be removed by filtration or the use of flocculants.The resultant powdered material is particularly useful as a carrier for oxidising ortho-xylene to phthalic anhydride.