Disproportionation of Some Alkylbenzenes on Synthetic H-Type Zeolite Catalysts

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  • H型合成ゼオライト触媒によるアルキルベンゼン類の不均化反応

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Disproportionation reaction of toluene, cumene and n-propylbenzene on synthetic HX and HY zeolite catalysts was studied using a flow system over the temperature range from 200 to 500 C under atmospheric pressure.<BR>The H-type zeolite catalysts have shown an induction period for the activation of catalyst, which was influenced by the reaction temperature (Tables 3 and 4, Fig.3) as well as by the structure of alkyl substituents on the benzene ring but not by LHSV (Table 2, Figs.1 and 2). The induction period was concluded to result from the formation process of disproportionation intermediates. Since the relative rate of disproportionation reaction of substituted benzenes was the following order, isopropy1 &gt; n-propy1 &raquo; methyl, the reactivity of alkylbenzenes was much affected by the stability of carbonium ion intermediates.<BR>It was clarified that the disproportipnation of alkylbenzenes on the zeolite catalysts at relatively higher temperature proceeded not by the scission of alkylsubstituent cation from benzene ring but by the attack of &alpha; -phenylalkyl carbonium ion on the polarized part of another alkylbenzene, that is, via 1, 1-diphenylalkyl carbonium ion intermediate (Fig.4), as proposed by Pines and Streitwieser in the reaction at lower temperatures.

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  • NIPPON KAGAKU KAISHI

    NIPPON KAGAKU KAISHI 1974 (7), 1283-1288, 1974-07-10

    The Chemical Society of Japan

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