MULTI-LAYER CATALYST FOR PRODUCING PHTHALIC ANHYDRIDE

摘要

The invention relates to a catalyst for producing phthalic anhydride by the gas phase oxidation of o-xylol and/or naphthalene, said catalyst containing at least three catalyst layers with different compositions, which are designated in order, starting from the gas inlet side to the gas outlet side, as the first, second and third catalyst layers. Said catalyst layers respectively contain an active material containing Ti02 and the active material content reduces from the first catalyst layer facing the gas inlet side to the third catalyst layer facing the gas outlet side, with the proviso that (a) the first catalyst layer comprises an active material content of between approximately 7 and 12 wt. %, (b) the second catalyst layer comprises an active material content ranging between 6 and 11 wt. %, the active material content of the second catalyst layer being less than or equal to the active material content of the first catalyst layer and (c) the third catalyst layer comprises an active material content ranging between 5 and 10 wt. %, the active material content of the third catalyst layer being less than or equal to the active material content of the second catalyst layer. The invention also relates to a preferred method for producing a catalyst of this type and to the preferred use of the inventive titanium dioxide.