The present invention relates to a catalyst, in particular for the
preparation of phthalic anhydride by gas phase oxidation of o-xylene
and/or naphthalene, having an inert support and at least one layer which
has been applied thereto and has a catalytically active composition
comprising TiO.sub.2, characterized in that at least a portion of the
TiO.sub.2 used has the following properties: (a) the BET surface area is
more than 15 m.sup.2/g, (b) the primary crystal size is more than 210
angstrom. Also described is a preferred process for preparing such a
catalyst, and the preferred use of the titanium dioxide used in
accordance with the invention.