Selective cycloalkylation of naphthalene on zeolites

Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...

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585400, 585430, 585446, C07C 200, C07C 264

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052929787

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BRIEF SUMMARY
The present invention relates to a method for the selective cycloalkylation of naphthalene using zeolites as catalyst. The invention concerns, in particular, a method of preparing monocycloalkylated aromatic compounds and a method of preparing dicycloalkylated aromatic compounds. The mono-and dicyclo-alkylated aromatic compounds are used in numerous fields, and it is important to prepare them selectively. Methods for the preparation of cycloalkylated aromatic compounds are known in the literature.
The production of aromatic compounds containing cycloalkyl groups using aluminum halides is known, for instance a synthesis of mono- or dicyclo-hexyl naphthalenes are with AlCl.sub.3, such reactions being described in particular in the following publications:
D. Bodroux, Annales de Chimie 1929, (10) 11, 535;
Charles C. Price, J. Am. Chem. Soc., 1943, 65, 439;
E. S. Pokrovskaya, J. Gen. Chem (USSR), 1939, 9, 1953.
This method leads to a low yield and an absence of selectivity and, furthermore, it is not economical.
The patents or patent applications DE-C-638 756, DE-A-2 208 363, U.S. Pat. No. 2,229,018, and U.S. Pat. No. 3,786,106 describe the alkylation of aromatic compounds by olefins, for instance cyclic olefins, in the presence of catalysts which are clays, for instance montmorillonite, kaolin, hydrosilicates, and bleaching earths. These methods are not selective.
U.S. Pat. No. 2,904,607, U.S. Pat. No. 3,641,177, U.S. Pat. No. 4,393,262, DE-A 3 334 084, EP-A-280 055, and J. Catal. 1986, 101, p. 273 describe the alkylation of aromatic products using zeolites as catalysts with linear alkylation agents such as, for instance, olefins having 2 to 4 carbon atoms, or methanol. These documents do not describe the alkylation of aromatic products with cyclic alkyl groups.
Patent Application DE-A-1 934 426 describes the continuous method of preparing alkylated aromatic compounds. This document cites numerous catalysts of zeolite type, for instance nature zeolites such as gmelinite, dachiardite, faujasite, heulandite and mordenite, or synthetic zeolites such as the omega, L and Y zeolites. This document also cites numerous aromatic compounds and a large variety of alkylation agents. This method is carried out in two steps. In the first step, the alkylation is effected with an alkylation agent in the presence of zeolites suspended in the liquid medium. The alkylation is not selective and a mixture of mono and polyalkyl aromatics is obtained. In order to remedy this lack of selectivity, the reaction mixture coming from the first step is contacted in a second step with a zeolite, without there being a suspension and without alkylating agent, so as to effect a transalkylation. Despite this second step, the overall selectivity at the end of these two steps remains low.
The object of the present invention is to provide a method for the cycloalkylation of naphthalene with an alkylating agent, using at least one zeolite as catalyst, the method being characterized surprisingly by both a high rate of conversion and a substantial selectivity, while using a larger ratio of alkylating agent to aromatic compound than used in general in the prior art. This method is characterized by the following points:
a) as catalyst, there is used at least one zeolite of faujasite structure having pore openings larger than 6.7 .ANG., the silica/alumina ratio of this zeolite being greater than 2.5 and its residual content of alkaline ion(s) being less than 3%;
b) the reaction is carried out batchwise in heterogenous liquid/solid phase at a temperature between 20.degree. C. and 250.degree. under a pressure of at most 30 bars, the zeolite or zeolites being suspended in the reaction medium;
c) the molar ratio of alkylating agent to naphthalene is at least equal to 1.
The cycloalkyls fixed by reaction on the naphthalene are for instance cyclopentyl or cyclohexyl, these alkyls possibly having substituents. The alkylation reagents must have at least one double bond or a reactive group, for instance a halogen or an OH group, such reagents being, for instance

REFERENCES:
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patent: 2904607 (1959-09-01), Mattox et al.
patent: 3513108 (1970-05-01), Kerr
patent: 3515680 (1970-06-01), Flank
patent: 3641177 (1972-02-01), Eberly, Jr. et al.
patent: 3773652 (1973-11-01), Dille et al.
patent: 3786106 (1974-01-01), Zuech et al.
patent: 5118896 (1992-06-01), Steigelmann et al.
Chemical Abstracts, vol. 94, No. 3, Jan. 19, 1981, p. 403, 15325z.

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