Aniline alkylation over solid acid catalysts

Alkyl anilines are useful intermediates. N-ethylaniline is an important dyestuff. N,N'-diethylaniline is used as a co-catalyst in polymerization reactions. It is also used as an inhibitor of acid corrosion in metallic vessels and as an antioxidant for lubricating oils. 2,6-diethylaniline is an important intermediate in the synthesis of weedicide, butachlor. Vapor phase aniline alkylation over several solid acid catalysts such as oxides, clays and zeolites and on their modified forms are discussed in detail. From the enormous information collected on the physico-chemical characteristics of the various solid acid catalysts and from the aniline activity studies, it has been observed that the structural features of the catalysts do play an important role in controlling conversion and selectivity. A reasonable acidity and activity relationship is established. A mechanism for aniline alkylation, with alcohol as alkylating agent, involving both the Bronsted and Lewis acid sites has been proposed. This review is based mainly on the work carried out in our laboratories as a part of envirocatalysis involving alkylation reactions over solid acids. (C) 2000 Elsevier Science B.V. All rights reserved.