Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Patent
1994-05-19
1995-12-12
Achutamurthy, P.
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
585446, 585467, C07C 266
Patent
active
054751772
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for the manufacture of alkylated aromatic hydrocarbons. More particularly, it relates to The manufacture of alkylated aromatic hydrocarbons containing an alkyl chain comprising at least four carbon atoms by condensation of an aromatic hydrocarbon, substituted by a short-chain alkyl group containing 1 to 3 carbon atoms, with an olefin in the presence of a catalyst.
TECHNOLOGY REVIEW
Application FR-A-2,647,438 (INTEROX) discloses a process for the synthesis of alkylated aromatic hydrocarbons which consists in reacting an aromatic hydrocarbon, substituted by a short-chain alkyl group, with an olefin in the presence of a catalyst prepared in the reaction medium by mixing anhydrous alumina with an alkali metal or an alkali metal hydride. The alkali metal/alumina or alkali metal hydride/alumina ratio by weight is preferably between 0.02 and 0.5.
It has been surprisingly found that it was possible to greatly increase the productivity of the reaction if the alkali metal/alumina or alkali metal hydride/alumina ratio by weight was adjusted so that it lies in a range of higher values.
SUMMARY OF THE INVENTION
To this end, the invention relates to a process for the synthesis of alkylated aromatic hydrocarbons containing a saturated alkyl chain comprising at least four carbon atoms, according to which an aromatic hydrocarbon substituted by a saturated short-chain alkyl group containing one to three carbon atoms is reacted with an olefin in the presence of a catalyst which comprises at least one alkali metal or one alkali metal hydride impregnated on an alumina support, the catalyst being prepared in the reaction medium in the presence of the aromatic hydrocarbon containing a short alkyl chain by mixing anhydrous alumina with the alkali metal or with the alkali metal hydride; according to the invention, the ratio by weight of the alkali metal or of the alkali metal hydride to the alumina support is between 0.6 and 1.8.
DETAILED DESCRIPTION OF THE INVENTION
The invention is targeted at preparing aromatic hydrocarbons alkylated by a saturated, linear or branched alkyl chain comprising more than four and, preferably, not more than eight carbon atoms. It applies in particular to the preparation of benzene hydrocarbons alkylated by a saturated and branched alkyl chain comprising five carbon atoms. It is very particularly suited to the preparation of amylbenzenes such as, for example, tert-amylbenzene.
Alkylated aromatic hydrocarbon containing a short chain used as starting material according to the invention is understood to denote any aromatic hydrocarbon containing one or a number of aromatic rings containing five or six carbon atoms and at least one saturated alkyl side chain comprising one to three carbon atoms. Benzene hydrocarbons containing a single aromatic ring are preferred and very particularly toluene, dimethyl and trimethylbenzenes, ethylbenzene, ethyltoluenes, n-propylbenzene and cumene.
The olefin used as alkylating agent must contain a linear carbon chain comprising at least two and not more than five carbon atoms, at least two of them being bonded by an unsaturated olefin-type bond. Monoolefins which only have a single unsaturation are preferred. By way of examples, the following olefins can be used in the process according to the invention: ethylene, propylene, n-butenes, isobutene, butadiene, n-pentenes and methylbutenes.
The catalyst used in the process according to the invention must contain at least one alkali metal or one alkali metal hydride in addition to the alumina support. Any alkali metal may be suitable. Sodium or sodium hydride are, however, generally preferred due to their good activity and their ready availability. Sodium can be the only alkali metal present with the alumina support; such a catalyst has given excellent results.
A variant of the catalyst in accordance with the process according to the invention consists in using an alumina support and a mixture of alkali metals or of alkali metal hydrides in substantia
REFERENCES:
patent: 2758140 (1956-08-01), Ipatieff et al.
patent: 4962254 (1990-09-01), Fukao et al.
patent: 5288936 (1994-02-01), Ganhy et al.
Achutamurthy P.
Solvay Interox (Societe Anonyme)
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