Alkylation of aniline with α-methylstyrene and separation of close boiling aromatic amines through reaction with α-methylstyrene, using acid-treated clay catalysts

Abstract

Alkylation of aniline with α-methylstyrene was carried out using acid-treated clay catalyst, Engelhard F-24, to produce mixture of mono- and dialkylated aniline. Alkylation occurred at the ortho- and para-positions of aniline and there was no N-alkylation. Mono and dialkylated anilines were separated from the reaction mixture and characterized by ¹H NMR. Reaction conditions to obtain high selectivity of the dialkylated product were studied. The extent of reusability of the acid-treated clay catalyst was also checked. Separation of close boiling compounds by physical methods like distillation is difficult. ortho-Toluidine/para-toluidine/meta-toluidine and ortho-cumidine/para-cumidine are close boiling aromatic amines of industrial importance. For the separation of these compounds, various techniques such as dissociation extraction, use of different adsorbents have been attempted by earlier researchers. In the present work, an alternative strategy was developed for the separation of ortho-toluidine/para-toluidine, meta-toluidine/para-toluidine and ortho-cumidine/para-cumidine through selective alkylation with α-methylstyrene followed by dealkylation of alkylated product(s). The alkylation/dealkylation reactions were catalyzed by acid-treated clay catalyst Engelhard F-24.