| 摘要 |
Cyclic mononuclear compounds of aromatic nature, which contain oxidisable side chains, are oxidised to the corresponding carboxylic acids with nitric acid at elevated temperature and increased pressure, if desired in the presence of a catalyst or an oxygen-containing gas, in a vertical reactor through which the reactants flow upwarly. The process is characterized in that the compound to be oxidised, the nitric acid, and the diluent water for the nitric acid, if any, are premixed in a mixer at a temperature below the reaction temperature, and if desired emulsified, and the mixture is led into the bottom of the reactor at such a high speed that it does not separate before entering the reactor, and the flow speed is decreased upon entry to at least one third. The reaction product is withdrawn from the top of the reactor. By decreasing the speed of flow, a vortex is formed and the entering jet sucks hot reaction product to the point of entry of the premixed initial material. The process is carried out at 150-400 DEG C. and at 10-150 atmospheres pressure. The catalyst, if present, may be mercury nitrate, or a nitrate of chromium, iron, or nickel, or an oxide of vanadium, molybdenum, or tungsten, or ammonium vanadate. Nitric acid of 10-40% is preferably used for the oxidation. The compounds of aromatic nature to be oxidised may contain one or more oxidisable side-chain substituents and these may be alkyl groups, or partially oxidised groups containing hydroxy, aldehyde or ketonic groups. Halogen may be present in the side chains. The process may be applied to the oxidation of benzene derivatives, or heterocyclic compounds such as pyridine and thiophene derivatives. Many such compounds are specified representative of which are:- ethyl benzene, butyl benzenes, trimethyl benzenes, ethyl toluenes, trimethylethyl benzenes, dimethyl-sec. butyl benzenes, benzyl alcohol, benzaldehyde, toluyl carboxylic acids, acetophenone, xylylene chloride, nitrotoluenes, chlorotoluenes, bromotoluenes, nitroxylenes, a -, b -, and g -picolines, lutidines, collidines, and a -, and b -methyl thiophene. The temperature of the pre-mixing should be such that no reaction takes place and it should be at least 20 DEG C. below the reaction temperature. The mixed reactants are supplied to the reactor while maintaining turbulence. If desired, the temperature of the reaction zone may be regulated by blowing superheated steam into the reactor at the point of entry of the reaction mixture. The mixing apparatus may comprise a system of successive jet mixers or perforated screens. To facilitate the reaction of slowly reacting compounds, the reactor may be provided with a circulation tube. Examples describe the oxidation of p-di-isopropyl benzene and p-xylene to terephthalic acid; crude xylene to a mixture of phthalic acids; p-nitrotoluene to p-nitro-benzoic acid; g -picoline to isonicotinic acid; pseudo-cumene to trimellitic acid; durene to pyromellitic acid. Specifications 698,157, 793,192 and 820,308 are referred to. |
