Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1986-01-06
1987-11-03
Moyer, Donald B.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
570190, 585469, C07C 4100
Patent
active
047044810
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the desulphurisation of benzylic and aromatic mercaptans. More specially, this invention relates to the desulphurisation of benzylic and aromatic mercaptans in the presence of an aqueous hydrocarbon solvent and a cobalt carbonyl catalyst.
Because of the long-term potential availability of carbon monoxide, a vast amount of research has been directed in recent times towards its utilisation in chemicals syntheses. This concentration of effort has led to commercial processes for the production of acetic acid by the reaction of methanol and carbon monoxide, and to another process whereby acetic anhydride is produced by the reaction of methyl acetate and carbon monoxide. Many other materials, for example alkyl halides, are reported to react with carbon monoxide but the development of commercial processes based on these reactions is still in the formative stages.
Our European patent application No. 84308313.0 describes a process for the production of an ester having the formula RCOOR.sup.1 by reacting at elevated temperature a mercaptan of formula RSH where R is a benzylic or aromatic moiety with carbon monoxide and an aqueous alcohol of formula R.sup.1 OH in the presence as catalyst of a cobalt carbonyl.
We have now found that benzylic and aromatic mercaptans can be desulphurised by contacting the mercaptans with carbon monoxide at elevated temperature in the presence of an aqueous hydrocarbon solvent and a cobalt carbonyl catalyst.
Accordingly, the present invention provides a process for the desulphurisation of a mercaptan of the formula RSH wherein R is a benzylic or aromatic moiety which process comprises contacting the mercaptan with carbon monoxide at elevated temperature in the presence of an aqueous hydrocarbon solvent and as catalyst a cobalt carbonyl catalyst.
Within the context of the present application the term desulphurisation means the removal of sulphur to form the corresponding hydrocarbon. Thus application of the process of the invention to a p-methylbenzyl mercaptan results in the formation of p-xylene and from m-toluenethiol there is formed toluene.
In the formula RSH, R is either a benzylic or an aromatic moiety. The benzylic moiety is of general formula: ##STR1## and may be substituted in the benzene nucleus portion thereof by, for example, hydrocarbyl groups such as by alkyl groups or by functional groups such as halide or alkoxy groups. Examples of benzylic mercaptans include but are not limited to p-methylbenzyl mercaptan, o-methylbenzyl mercaptan, p-methylbenzyl mercaptan, p-chlorobenzyl mercaptan, 2,4-dichlorobenzyl mercaptan and the like.
The aromatic moiety may be either substituted or unsubstituted and includes aryl, arylene and multiply substituted moieties. The substituted aromatic moiety may be substituted with, for example, alkyl, alkenyl or halide groups. Examples of aromatic mercaptans include but are not limited to m-toluenethiol, p-bromothiophenol, 2-naphthene thiol, phenylthiol and the like. Mixtures of aromatic mercaptans and benzylic mercaptans can be desulphurised by the process of the present invention.
Carbon monoxide may be obtained from a wide variety of carbonaceous sources using well-established conversion technology. The carbon monoxide may be pure or may contain such impurities as carbon dioxide, nitrogen or hydrogen. The carbon monoxide pressure may suitably be the autogenous pressure at the reaction temperature employed. Alternatively, carbon monoxide pressures in excess of the autogenous pressure, for example from 2 to 250 psig above the autogenous pressure, may suitably be employed.
As the hydrocarbon solvent, either an aromatic or an aliphatic liquid hydrocarbon may be used. The aromatic hydrocarbon may be substituted with, for example, alkyl or halide groups. The aliphatic hydrocarbons may suitably be a paraffin which may be linear, branched or cyclic. Suitable hydrocarbon solvents include benzene, toluene, xylene, hexane and cyclohexane. A preferred solvent is benzene. The amount of water employed may suitably
REFERENCES:
Shim, Tetrahedron Letters, vol. 26, No. 16 (1985) 1935-1938.
Alper Howard
Smith David J. H.
Boska Joseph A.
Moyer Donald B.
The British Petroleum Company p.l.c.
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