MANUFACTURE OF TEREPHTHALIC ACID

摘要

Disclosed is a process for the continuous production of terephthalic acid from p-xylene, comprising the steps of oxidizing p-xylene in a first oxidation zone in the presence of not more than about 10 weight % of water and a cobalt/manganese catalyst up to a conversion of about 15% terephthalic acid; oxidizing the partially-oxidized compounds in a second oxidation zone in the presence of an additional amount of water up to about 20 to 70% by weight and in the presence of an additional amount of the catalyst up to a conversion of about 50% by weight terephthalic acid; stripping p-xylene vapors from the second oxidation zone; separating crystals of crude terephthalic acid from the effluent from the second oxidation zone from the soluble components of the effluent; countercurrently washing the separated crystals with fresh water to produce a slurry; recycling a part of soluble components to the second oxidation zone, and another part of the first oxidation zone to provide the latter with heavy metal catalyst; and recovering purified terephthalic acid by recyrstallizing the crystals contained in the slurry.