Patent GB-840009-A (GB)
Title: Improvements in and relating to the oxidation of organic compounds
Inventor: WHITFIELD GORDON HOWARD
IPC: C07C51/265
Filed: 1957-08-02
Abstract: In a continuous or cyclic process for the oxidation of organic compounds in the liquid phase by means of an oxygen-containing gas, in the presence of a catalyst comprising a metal ion of variable valency and a halogen, preferably bromine, and in the presence of a solvent, the liquor which remains after the separation of the desired product from the oxidation products is distilled to recover oxidizable compounds and solvent, which are recycled to the oxidation process, while the distillation residues, containing compounds which adversely affect the oxidation, are discarded.  It is advantageous to employ a solvent in which the required product is only slightly soluble, for the product is then readily separated in solid form by filtration. Specified solvents are: acetic, propionic and benzoic acids, esters of these acids, benzene, and monoand di-chlorbenzenes. The process is suitable for the oxidation of the xylenes and di-isopropylbenzenes to the corresponding phthalic acids, the oxidation of p-toluic acid to terephthalic acid, the oxidation of methyl p-toluate to methyl hydrogen terephthalate, the oxidation of toluene, cumene, benzyl benzoate, benzyl alcohol, benzaldehyde, or acetophenone to yield benzoic acid, the oxidation of methyl naphthalenes to the naphthoic acids, the oxidation of the methyl pyridines to the corresponding pyridinic acids, and the oxidation of mesitylene to trimesic acid.  Aliphatic acids can also be made by the process, e.g. adipic acid by oxidation of cyclohexene, cyclohexane or cyclohexanone.  Methyl cyclohexene and methylcyclohexane yield, inter alia, glutaric and succinic acids; and pentane yields a mixture of butyric, propionic, acetic and formic acids.  Propionaldehyde, n-butyraldehyde and isobutyraldehyde yield propionic acid, butyric acid and isobutyric acid respectively. Betabeta1-dichloro-diethylether yields beta-chlorethyl chloracetate. Diethyl ether yields ethyl acetate and acetic acid. Other compounds which may be oxidized by the process are: p- and m-chlorotoluene, p- and m-toluene sulphonamides, p- and m-cresyl benzoates, p-toluene sulphonic acid, methyl p-toluene sulphonate, p-toluamide, chloro- and bromomethyl benzene chloro- and bromomethyl toluene.  The oxidation of para-nitrotoluene to para-nitrobenzoic acid is also referred to. In an example, o-xylene is dissolved in benzoic acid containing cobalt bromide and manganese bromide and is oxidized at 150 DEG  C. by passing oxygen through the mixture.  The apparatus is provided with a reflux condenser, and a decanter for the removal of water. After 20 hours, a small quantity of water is added to the reaction mixture, and it is stirred for 1 1/2 hours.  Phthalic acid is filtered off, and washed with ether.  The mother-liquor, after removal of the ether, is oxidized together with another portion of o-xylene and cobalt bromide; and thirteen further similar oxidations are effected.  On the 14th recycle with a further addition of o-xylene, no phthalic acid is produced, and the reaction product is black and tarry.  An aliquot of this tarry product is distilled yielding, besides low-boiling material and a pitchlike residue, a fraction boiling from 110 DEG /3 mm. to 122 DEG /1 mm.  This fraction, when oxidized with a further amount of o-xylene and cobalt bromide, gives a good yield of phthalic acid by hydrolysis. Specifications 804,612 and 807,091 are referred to.