The application of silica-alumina catalysts to a Friedel-Crafts type reaction

Abstract

The development of the Friedel-Crafts reaction using anhydrous aluminum chloride in the condensation or aromatic hydrocarbons and alkyl or acyl halides has resulted in many new and diversified applications of this reaction, such as the preparation of hydrocarbons, keto acids, acids, ketones, and phenols. Halides of iron, tin, phosphorus, zinc, and other metals, and acids such as phosphoric, sulfuric, and anhydrous hydrofluoric have been found to catalyze a large number of reactions of this type. These same catalysts now find a wide commercial application in the alkylation of paraffins and naphthenes, and other types of reactions, such as isomerization, transfer of radicals, and cracking of petroleum.

Although the Friedel-Crafts synthesis is very widely used in organic syntheses because of its high efficiency, very little work has been done toward developing a more economical catalyst. The anhydrous aluminum chloride generally used is wholly or partially consumed in a large number of the reactions, in addition to presenting a difficult corrosion problem.

Some work has recently been done by Sachanen and Caesar⁽²⁵⁾ on the catalytic effect of activated clays and the type of silica-alumina catalysts used in the cracking of petroleum, when used in a Friedel-Crafts type reaction. The limited amount of work which has been done so far indicates that it might be economical to use a synthetic silica-alumina type catalyst to replace the anhydrous aluminum chloride in reactions of this type, because it could be used for some time without replacement.

The object of this investigation was to determine the feasibility of using different synthetic silica-alumina type catalysts in the condensation of benzene with acetic anhydride to produce acetophenone.