Crisotila como suporte para acidos de Lewis na catalise de reações de Friedel-Crafts

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The catalytic alkylation of benzene with benzyl chrolide was studied using chrysotile as a support for Lewis acid. Two methods of immobilization were used: grinding the acid and the support together, and adsorption from an organic solution. Within the acids supported on chrysotile studied, FeCI3, CoCI2 and ZnCl2 have shown good catalytic activity, giving yelds with a rangeof 60 to 80% of isolated diphenylmethane, after 3 hours of reaction. The best yield was obtained with chrysotile-ZnCl2 in the proportion 0.3g Lewis acid per gram of chrysotile, imobilized by grinding. Atomic absorption analysis of the reactional mediurn confirms that there was no free zinc in solution, which suggests that the grinding is a reasonable method for immobilization. Studies on the effects of the temperature of calcination have shown that between 150 and 400°C there was no loss of activity of the catalyst chrysotile-ZnCl2. With chrysotile we have obtained similar yelds to those obtained with rnontmorillonite. On alkylation of acetylacetone with benzyl or cinnamyl choride, with supported ZnCI2 catalysis, we have obtained 40 and 10% yelds, respectively. Acylation of anisole with acetyl chloride gave less than 36% yeld, in the presence of either chrysotile or montmorillonite, giving para- and ortho- methoxyaceto - phenone in the proportion of 7:3. Using a supported Lewis acid as a catalyst for the Fries rearrangements of phenyl sorbate, sorbic acid, hydrolysis product of the ester was obtained. We conclude that the water of the catalyst was not entirely removed under thermal heating, giving hydrolysis of the initial ester product.

ASSUNTO(S)

reações quimicas crisotila alquilação

ACESSO AO ARTIGO

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