Method for producing phthalic anhydride

摘要

A process for preparing phthalic anhydride by gas-phase oxidation of xylene, naphthalene or mixtures thereof over two different fixed-bed catalysts arranged in zones in a shell-and-tube reactor which is thermostated by means of a heat transfer medium is carried out so that the maximum temperature in the second catalyst zone in the flow direction is at least 52° C. lower than the maximum temperature in the first catalyst zone. The process of the present invention makes it possible to prepare phthalic anhydride in high yields under conditions relevant to industrial practice.