Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1997-01-09
1998-10-06
Reamer, James H.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568322, 549436, C07C 4545
Patent
active
058178783
DESCRIPTION:
BRIEF SUMMARY
This application is A371 of PCT/FR 96/00717.
The present invention concerns a process for the acylation of an aromatic ether.
Preferably, the invention relates to a process for the acylation of an unsubstituted aromatic ether, more particularly anisole.
The invention is applicable to the preparation of alkoxyaromatic alkylketones.
Conventional processes for the acylation of aromatic compounds, in particular the ethers of phenols, consist of carrying out a Friedel-Crafts acylation reaction.
The aromatic compound is reacted with an acylation agent in the presence of a catalyst which is generally aluminium chloride. Papers Inst. Phys. Chem. Res. 18, pp 51-60 (1932)! which describes the preparation of methoxyacetophenones by the reaction of an aromatic compound carrying 1 to 3 methoxy groups with acetyl chloride in the presence of aluminium chloride.
The use of aluminium chloride, however, has a number of disadvantages. Aluminium chloride is corrosive and an irritant. Further, a large quantity of aluminium chloride must be used, at least equal to the stoichiometric quantity, because of complexation with the ketone formed. As a result, the aluminium chloride is not a true catalyst.
At the end of the reaction, the aluminium chloride must be eliminated from the reaction medium by carrying out acidic or basic hydrolysis.
Hydrolysis implies the addition of water to the reaction medium, considerably complicating the process since the metal cation, and more particularly the aluminium cation, forms aluminium polyoxo- and/or polyhydroxo complexes of milky consistency, which are difficult to separate. This necessitates a long, expensive treatment following hydrolysis comprising extraction of the organic phase, separation of the aqueous and organic phases, and even drying of the latter. Separation of aluminium chloride is thus lengthy and expensive.
Further, there are problems with aqueous saline effluents which must then be neutralised and which necessitate an additional operation.
Still further, the aluminium chloride cannot be recycled as it has been hydrolysed.
In order to overcome this disadvantage, it has been suggested that the reaction be carried out in the presence of heterogeneous catalysts.
Thus for about a decade, zeolites have been recommended for use as acylation catalysts.
Prins et al. described the acetylation of anisole by acetic anhydride presence of zeolites such as .beta. zeolite or USY zeolite. It should be noted that .beta. zeolites produced more interesting results as regards both the degree of conversion and the reaction yield.
However, the catalyst performances described were not satisfactory. The use of that catalyst on an industrial scale causes problems since the productivity of the catalyst is insufficient necessitating a very large reactor.
An object of the present invention is to provide a process which can overcome the above disadvantages.
We have now discovered, and this constitutes an object of the present invention, a process for the acylation of an aromatic ether which consists of reacting the ether with an acylation agent in the presence of a zeolitic catalyst, the process being characterized in that the acylation reaction is carried out in the presence of an effective quantity of a catalyst comprising a beta zeolite with an atomic ratio denoted "global Si/Me.sup.1 " between the number of atoms of the element silicon and the number of atoms of every trivalent element Me.sup.1 contained in the zeolite of no less than 15, preferably in the range 15 to 55, and more preferably in the range 18 to 35.
The term Me.sup.1 denotes any element with a degree of oxidation of +3, in particular aluminium, gallium, iron, boron and mixtures thereof, preferably aluminium.
The "global Si/Me.sup.1 " atomic ratio of the zeolite is primarily determined by X ray fluorescence.
The catalyst used in the process of the invention comprises an active phase which is a beta (.beta.) zeolite of structural type BEA which has certain well defined characteristics. It has a low concentration of element Me.sup.t, which i
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Benazzi Eric
Gilbert Laurent
Marcilly Christian
Spagnol Michel
Carleton Katherine L.
Reamer James H.
Rhone-Poulenc Chimie
Seugnet Jean-Louis
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