In this work, a systematic study of the acid extraction of the surfactant present in MCM-41 mesoporous materials was carried out. Two organic solvent/acid mixtures were used at various temperatures and for different periods of time. Propylthiol groups were subsequently grafted onto the surface by reacting the mesoporous silica with 3-mercaptopropyltrimethoxysilane. The resulting organic matter loading is compared with the one yielded by grafting of calcined samples. Acid catalysts were obtained by oxidation of the -SH groups to the -SO3H form. The catalysts were tested for alkylation of benzene with 1-dodecene. These materials were characterized by means of XRD, themogravimetric analysis, N-2 adsorption-desorption isotherms, organic elemental analysis and acid titration. The acid extraction of the surfactant allowed the preparation of catalysts with a high concentration of active centers. (c) 2005 Elsevier B.V. All rights reserved.