The invention relates to a catalyst for gas-phase oxidations, comprising an inert substrate and a catalytically active mass applied thereon, said mass containing vanadium oxide and titanium dioxide. The titanium dioxide has a content of sulfur compounds, calculated as S, of less than 1000 ppm and a content of calcium compounds, calculated as Ca, of less than 150 ppm. The catalyst has a higher activity and/or selectivity and thus enables higher yields of the desired target product, e.g., phthalic anhydride. The invention also relates to a method for producing phthalic anhydride, wherein a gas flow that contains molecular oxygen and o-xylene, naphthalene, or mixtures thereof, is brought into contact with the catalyst.