Butylated hydroxy anisoles, are very valuable and dominant food anti-oxidants and they are produced by highly polluting Friedel-Crafts alkylation of 4-methoxyphenol using homogeneous acids or from hydroquinone in a two-step reaction using alkylation followed by etherification using dimethyl sulphate under alkaline conditions. The current paper reports the activities of Filtrol-24, K-10 montmorillonite clay, dodecatungstophosphoric acid (DTP) supported on K-10 clay, sulphated zirconia and cation exchange resin Deloxane ASP in the alkylation of 4-methoxyphenol with MTBE.The order of catalytic activity of the solid acid catalysts studies is:Filtrol-24 > DTP/K-10 > Deloxane ASP resin > K-10 Montmorillonite clay > S-ZrO2 Only two products 2-tert-butyl-4-methoxyphenol and 2,5-di-tert-butyl-4-methoxyphenol were formed with maximum selectivity to the monoalkylated product, both of which are used as anti-oxidants either as a mixture or alone. The effects of various parameters were studied to arrive at the reaction kinetics. The reaction is intrinsically kinetically controlled with an activation energy of 12.81 kcal/mol. (C) 2003 Elsevier B.V. All rights reserved.