CATALYST SYSTEM FOR OXIDIZING O-XYLOL AND/OR NAPHTHALENE INTO PHTHALIC ANHYDRIDE

摘要

The invention relates to a catalyst system for oxidizing o-xylol and/or naphthalene into phthalic anhydride (PA), which catalyst system comprises a plurality of catalyst layers arranged one after the other in the reaction tube, for the production of which catalyst system an antimony trioxide was used, which contains an appreciable fraction of senarmontite, some of the primary crystallites of which have a size of less than 200 nm. The present invention further relates to a method for gas-phase oxidation, wherein a gas flow, which comprises at least one hydrocarbon and molecular oxygen, is conducted through a catalyst system, which comprises a plurality of catalyst layers arranged one after the other in the reaction tube and for the production of which an antimony trioxide was used, which contains an appreciable fraction of senarmontite, some of the primary crystallites of which have a size of less than 200 nm.