GB814733A - Process for oxidizing aromatic compounds containing alkyl side chains - Google Patents

Abstract

<PICT:0814733/III/1> An apparatus for oxidizing alkyl-substituted aromatic compounds (see Group IV (b)) with nitric acid and optionally oxygen, at elevated temperature and pressure, the heat of reaction being absorbed in evaporating water which is approximately at the reaction temperature and the steam produced being removed rapidly, is described by reference to the accompanying Figure. Nitric acid is pumped at 4 into the top of the connected pressure tubes 1, 2 and 3 and the aromatic compound is pumped in between the upper and middle tubes. Waste gas escapes at the top of the apparatus through a reflux condenser and a pressure regulator 9. The product is withdrawn at 11 after passing through condenser 10. Air or an inert gas may be blown in at 26. The heating jackets of the pressure tubes contain an equilibrium mixture of water and steam at constant temperature, the heating water being brought to the reaction temperature by, for example, electrical or steam heating. The upper ends of the heating jackets are connected together and to the upper part of boiler 17. From the bottom of the boiler the condensed water is led to the lower ends of the heating jackets. The boiler is provided with a condenser 24 where steam is condensed thus controlling the pressure and the temperature.ALSO:Aromatic compounds containing one or more alkyl side chains are oxidized, by means of nitric acid and optionally oxygen at raised temperature and superatmospheric pressure, to oxidize the alkyl side chains and give carboxylic acids in a process wherein the heat generated by the reaction is absorbed in evaporating water which is approximately at the reaction temperature and the steam produced is removed rapidly (see Group III). Specified aromatic compounds are toluene, chloro-, bromo- and nitro-toluenes, xylenes, chloro-, bromo- and nitro-xylenes, cresols, xylenols, thymol, toluene and pseudocumene sulphonic acids, mesitylene, pseudocumene, methyl-ethyl-benzenes, ethyl- and propyl-benzenes, cumene, cymenes and methyl-benzoic acids. When oxygen is used in the oxidation it may be used alone or admixed with inert gases such as nitrogen, carbon dioxide, helium, neon or argon, air being preferred. In examples: (1) orthochlorotoluene is oxidized to ortho-chlorobenzoic acid with nitric acid and air and the procedure compared with other known methods; (2) crude p-cymene is oxidized with nitric acid and air in the presence of manganese sulphate to terephthalic acid.