| 摘要 |
1,247,981. Isophthalic and terephthalic acid. ATLANTIC RICHFIELD CO. 7 May, 1969 [9 May, 1968], No. 23349/69. Heading C2C. A two-stage method for the production of a high purity terephthalic and isophthalic acid from C 8 aromatic hydrocarbon feedstock containing a major amount of the desired isomer of xylene corresponding to the desired acid, comprises oxidizing a feed comprising an alkanoic acid containing 5 to 15 weight per cent of the desired xylene isomer to the corresponding toluic acid in a first oxidation stage with a gas containing free molecular oxygen, said feed containing above 0.05 moles cobalt per kilogram of feed as catalyst, 0À1 to 4 weight per cent water and less than 5 weight per cent orthophthalic acid, the first oxidation stage being maintained at a temperature of 210‹ to 300‹ F., a pressure of 50 to 1000 p.s.i.a. and an oxygen partial pressure of 5 to 500 p.s.i.a., the feed being oxidized in the first oxidation stage for a period sufficient to provide a first stage oxidation product wherein at least 50% of the xylene in the feed has been oxidized to the corresponding toluic acid, the cobalt catalyst within the first stage comprising 10 to 50% trivalent cobalt and the remainder bivalent cobalt, the said first-stage oxidation product containing less than 5 weight per cent orthophthalic acid and less than 5 weight per cent water, and then oxidizing the said first stage oxidation product with a gas-containing free molecular oxygen in a second stage in the presence of above 0.05 mole per kilogram first stage product of cobalt at least 30% of which is in trivalent form, and 0.05 to 0.5 moles of an alkanal corresponding to the alkanoic acid per mole of toluic acid in the first stage product at a temperature of 190‹ to 275‹ F., a pressure of 50 to 1000 p.s.i.a. and an oxygen partial pressure of 10 to 500 p.s.i.a. for a period cf time sufficient to obtain a secondstage oxidation product representing at least 70% conversion of the xylene in the feed to the corresponding benzene dicarboxylic acid. |
