| 摘要 |
The process for making phthalic anhydride by catalytic gas phase oxidation of o-xylene or naphthalene includes feeding a gas containing oxygen and the reactant to a first reactor; operating the first reactor to oxidize the reactant and obtain an effluent gas including the reactant, phthalic anhydride and/or maleic anhydride; adding the reactant or a gas containing the reactant to the effluent so that a molar ratio of moles of free oxygen to a sum of moles of the organic compounds in the effluent is less than 7, preferably from 3 to 6; after that, feeding the effluent into a second reactor; and operating the fixed bed reactor to at least partially convert the reactant in the effluent to phthalic anhydride. In preferred embodiments the gas fed to the first reactor is controlled so that it is in the range of the lower inflammability limit and, after separating phthalic anhydride from the effluent, from 15 to 35% of the resulting waste gas is blended with fresh air, compressed to form a gas mixture and then recycled.
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