Benzoic Acid → Phthalic Anhydride

Participants

Reaction Steps

3200 parts of a 22% solution of maleic acid which contains 4% of other acids such as phthalic acid, citraconic acid and benzoic acid is supplied per hour through a tubular heater which preheats to 100°C to a falling-film evaporator. This solution has been obtained by scrubbing offgas obtained in the manufacture of phthalic anhydride by catalytic oxidation of o-xylene with air at a temperature of 40°C. In the first evaporator the solution is concentrated at atmospheric pressure and at 120°C to a content of 40% of maleic acid. The aqueous condensate is returned to the offgas scrubber.

Provenance & Evidence