The preparation, characterization, and performance of catalysts based on AlCl3 and different silica for the tetrahydropyranylation of thymol are reported. These catalysts were obtained by two procedures: incipient wetness impregnation and functionalization; in addition, the reaction was tested at 20 degrees C, using toluene as solvent. Thymol is a natural product of the terpene family and is currently used as disinfectant. All silica-supported aluminum chlorides showed catalytic activity and, under these conditions, secondary products were not obtained. From the point of view of conversion and reuse, the best catalysts were SiO2(AR106)-I and SiO2(SG)-F. For the former catalyst, the conversion in its third reuse was 83%, while Sio(2)(SG)-F presented a conversion of 95% in its second reuse. The catalytic system represents a clean way to obtain the tetrahydropyranylation of phenol using AlCl3 because the catalyst can be recycled. (C) 2008 Elsevier B.V. All rights reserved.