The present invention relates to a catalyst for preparing carboxylic acids and/or carboxylic anhydrides, which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight. The present invention further relates to a process for gas-phase oxidation in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight.