| 摘要 |
The invention relates to a catalyst for the catalytic gas phase oxidation of aromatic hydrocarbons to form aldehydes, carboxylic acids and/or carboxylic acid anydrides, in particular phthalic acid anhydride, comprising a plurality of different catalyst layers, wherein the catalyst comprises a hot spot catalyst layer in which the greatest local temperature maximum occurs, relative to the entire catalyst, at least one catalyst layer placed prior to the hot spot catalyst layer, and preferably at least one catalyst layer placed after the hot spot catalyst layer. According to the invention, in the case of antimony and/or bismuth and/or niobium in the catalytically active material of the hot spot catalyst layer the amount of at least one of said elements in the catalytically active material of at least one catalyst layer placed before is reduced compared to the amount of the same element in the catalytically active material of the hot spot catalyst layer by a pre-determined value. |
