| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing an acid anhydride by which the yield can be improved when producing the acid anhydride by catalytically oxidizing an aromatic compound in vapor phase, and the reduction of the construction cost and the facilitation of the introduction to an existing plant are performed because a catalyst for treating by-products can be easily installed. SOLUTION: This method for producing the acid anhydride comprises a step for carrying out a catalytic vapor-phase oxidation of a feedstock including the aromatic compound by a reactor consisting essentially of a multi-pipe type fixed bed reactor. The reactor consisting essentially of the multi-pipe type fixed bed reactor is temperature-controlled, and has the first catalyst layer at which >=90% of the feedstock is consumed, and the second catalyst layer present at the downstream of the first catalyst layer. The temperature of the gas introduced to the second catalyst layer has a temperature not less than 95% of the control temperature at the first catalyst layer, and the activity of the packed catalyst is smaller than that of the catalyst at the aftermost part of the first catalyst layer.
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