| abstract |
In a process for the preparation of terephthalic acid wherein a p-substituted aromatic compound, e.g. an aromatic hydrocarbon is catalytically oxidized with gaseous molecular oxygen in the presence of aliphatic carboxylic acid, e.g. acetic acid, as a solvent and in the co-existence of an oxidation catalyst, e.g. cobalt, manganese, chromium, nickel, cerium and lead, and bromine or a bromine compound, after the completion of oxidation reaction, the reaction mixture is further catalytically oxidized with gaseous molecular oxygen at a temperature of 200 DEG to 300 DEG C. which is higher than the previous oxidation temperature. In an example, paraxylene, commercial acetic acid, cobalt acetate, manganese acetate and ammonium bromide are charged into a titanium-lined autoclave and heated at 210 DEG to 215 DEG C., and the pressure was maintained at 27 kg./cm.2 (gauge) by the introduction of air at the rate of 1001./hr. Then the reaction mixture was heated to 250 DEG C. and the pressure was elevated to 35 kg./cm.2 (gauge) by supplying further air introduced at the rate of 1001./hr. which was stopped after an hour and the autoclave cooled to a room temperature and terephthalic acid was separated from the reaction mixture. |