This work presents a method to prepare composites based on polyaniline (Pani) and styrene-divinylbenzene copolymers (SD) by in situ polymerization of aniline using benzoyl peroxide as oxidant agent. The composites were obtained from copolymers with two degrees of porosities which have higher and lower surface areas. Emeraldine Pani was prepared using hydrochloric acid as dopant. One cycle or four cycles of aniline polymerization were performed. The copolymers and their respective composites characterizations were performed by infrared spectroscopy, thermogravimetric analysis, physical nitrogen adsorption-desorption measurements, morphology analysis, elemental analysis and determination of Bronsted acid sites. The Pani was distributed overall porous SD copolymer producing composites with high surface area. Then, they were evaluated as catalysts for esterification reaction of a fat acid. It was found that that composites prepared with four cycles of in situ polymerization presented best catalytic activity than one cycle composites. (C) 2013 Elsevier Ltd. All rights reserved.