Patent GB-793192-A (GB)
Title: Improvements in or relating to the oxidative treatment of organic substances
IPC: C07B35/04
Filed: 1955-01-14
Abstract: Organic substances are oxidized to carboxylic acids by a process wherein the organic substance is treated with nitric acid in a vertical reaction tube supplied from below, through which the reaction mixture is continuously passed at elevated temperature and, if required, under increased pressure, characterized in that, in oxidizing in the presence of oxidation gases such as air, oxygen or other molecular oxygen-containing gases supplied concurrently, the starting materials are introduced continuously into the tube together with the gases supplied from below, the reaction products, including gases and vapours, evolved during the reaction, are withdrawn from the upper end of the tube through a downwardly directed cooler and nitric acid is recovered from the oxidized solution (see Group III). Specified substances which may be oxidized include toluene, xylenes and p-cymene.  In examples: (1) hard coal is oxidized to give a mixture of succinic, glutaric and adipic acids and benzene carboxylic acids containing 2-6 carboxyl groups; (2) p-tolualdehyde is oxidized to p-toluic and terephthalic acids; (3) p-toluic acid or p-xylene is oxidized to terephthalic acid; (4) cyclohexane or cyclohexanol or a mixture of cyclohexanol and cyclohexanone is oxidized to adipic acid, succinic and glutaric acids also being obtained in the oxidation of cyclohexane.  Specification 795,816 is referred to.ALSO:<PICT:0793192/III/1> Organic substances are oxidized to carboxylic acids (see Group IV (b)) by a process wherein the organic substance is treated with nitric acid in a vertical reaction tube supplied from below, through which the reaction mixture is continuously passed at elevated temperature and, if required, under increased pressure, characterized in that, in oxidizing in the presence of oxidation gases such as air, oxygen or other molecular oxygen-containing gases supplied concurrently, the starting materials are introduced continuously into the tube together with the gases supplied from below, the reaction products, including gases and vapours evolved during the reaction, are withdrawn from the upper end of the tube through a downwardly directed cooler and nitric acid is recovered from the oxidized solution.  The nitrous gases formed during the oxidation, are converted to nitric acid by the oxygen present, during the cooling.  The nitric acid is separated from the reaction product by, for example, decantation or distillation.  The oxygen is introduced into the reaction mixture in a state of fine subdivision, to avoid mixing and to increase the reaction rate.  As shown, an apparatus suitable for carrying out the process of the invention comprises a vertical oxidation tube 1 with heating and cooling units 4 and an inlet 2 for the organic substance and nitric acid.  The oxygen enters through a frit or screen 3, the pressure being regulated by outlet valve 10. The reaction mixture passes from the top of the reactor downwardly through cooler 8 into the receiver 9.  In examples, various organic substances such as coal, p-tolualdehyde, p-cymene and cyclohexane are oxidized in the apparatus described above to the corresponding acids.  Specification 795,816 is referred to.