Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1994-04-13
1995-12-05
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562409, C07C 5116
Patent
active
054731011
DESCRIPTION:
BRIEF SUMMARY
This Application is a 371 of PCT/GB92/01076 filed 16 Jun. 1992.
This invention concerns a process for the oxidation of alkylaromatic compounds using an oxidising system comprising cobalt salts and hydrogen peroxide.
The oxidation of alkylaromatic compounds using oxidising systems comprising cobalt salts is known in the art.
U.S. Pat. Nos. 3,665,030 and 3,969,405 disclose that alkylaromatic compounds may be oxidised to aromatic carboxylic acids using an oxidation system comprising a cobalt acetate catalyst, acid activator and molecular oxygen oxidant. The reaction is not commercially satisfactory for the preparation of carboxylic acids since the reaction times required to obtain high conversion rates are too long. Furthermore, the reaction tends not to be selective in the preparation of monocarboxylic acid aromatics from poly(alkyl)aromatics (see U.S. Pat. No. 3,665,030, particularly Example XXVI and Example XXXVII, and U.S. Pat. No. 3,969,405, particularly Examples XXXVII to XLIV).
U.S. Pat. Nos. 4,323,692 and 4,401,828 disclose that phenoxytoluenes may be oxidised to phenoxybenzoic acids in the presence of from 0.001 to 0.5 moles of a cobalt (II) salt catalyst per mole of phenoxytoluene, from 1 to 3 equivalents of bromide ion per mole of cobalt (II) salt, from 0.5 to 1 mole of hydrogen peroxide activator per mole of cobalt (II) salt and the introduction of gaseous oxygen oxidant.
U.S. Pat. No. 3,519,684 discloses a process for producing aromatic dicarboxylic acids from di(alkyl)aromatic compounds using an oxidising system comprising a cobalt salt catalyst, peracetic acid activator and the introduction of gaseous oxygen oxidant.
It is an object of the present invention to provide a process for the oxidation of alkylaromatic compounds, which process does not essentially require the introduction of gaseous oxygen.
It is a further object of the present invention to provide a process for the oxidation of alkylaromatic compounds which process may achieve high conversion and high yields of oxidised products by a one-pot reaction.
It is yet a further object of the present invention to provide a process for the selective oxidation of poly(alkyl)aromatic compounds to form aromatic carboxylic acid compounds, which process does not essentially require the introduction of gaseous oxygen as oxidant.
In accordance with the present invention, there is provided a process for oxidising an alkylaromatic compound, which process comprises reacting said alkylaromatic compound with an oxidising system comprising from at least 0.01 moles of cobalt (III) ions per mole of alkylaromatic compound, from at least 0.01 moles of bromide ions per mole of alkylaromatic compound, and from more than 0.5 mole, preferably more than 1 mole, of hydrogen peroxide per mole of alkylaromatic compound, in the presence of an appropriate protic solvent selected from the group consisting of the carboxylic acids having from one to five carbon atoms, said alkylaromatic compound having at least one alkyl substituent which is not tertiary at the carbon positioned alpha to the aromatic ring.
The preferred protic solvents are acetic acid, propionic acid and butyric acid, the most preferred being acetic acid. The protic solvent may be present in any reasonable amount but is preferably present in an amount of at least 3 times the weight of the alkylaromatic compound and preferably no more than 15 times, such as from 3 to 12 times, the weight of the alkylaromatic compound. When the alkylaromatic compound is a poly(alkyl) aromatic compound, the preferred amount of protic solvent used is from 4 to 10 times the weight of the poly(alkyl)aromatic compound. When the alkylaromatic compound is a mono-alkylaromatic compound, the preferred amount of protic solvent used is from 8 to 12 times the weight of the mono-alkylaromatic compound.
In the process of the present invention, the cobalt (III) ions are preferably sourced from an in-situ oxidation of cobalt (II) ions. The cobalt (II) ions may be sourced from any appropriate cobalt (II) salt, such as cobalt (II) acetate, c
REFERENCES:
patent: 3914295 (1975-10-01), Rosenthal et al.
patent: 4007256 (1977-02-01), Kim et al.
J. Dakka et al.; Mar. 29, 1988, p. 756; "Hydrobromic Acid Catalzed Oxidation of Benzyl Alcohols by Hydrogen Peroxide"; Bulletin De LaSociete Chimique De France, No. 4, 1988, Paris.
Jeff Martin
Johnstone Alexander
Rowbottom Kenneth T.
Sanderson William R.
Service Miranda
Killos Paul J.
Solvay Interox Limited
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