Homogenous deposition-precipitation oil either it silica or carbon nanofiber (CNF) support of cobalt front basic Solution using ammonia evaporation was studied and compared with conventional deposition from all acidic solution Using Urea, hydrolysis. III the low-pH experiment, the interaction between precipitate and silica was too high; cobalt hydrosilicates were formed requiring a reduction temperature of 600 degrees C, resulting in low cobalt dispersion. Lower interaction in experiments performed in a basic environment yielded it well-dispersed Co3O4 phase oil silica, and after reduction ill only 500 degrees C, a catalyst with 13-nm cobalt particles was obtained. Oil CNF from an acidic solution, cobalt hydroxy carbonate precipitated and displayed it low interaction with the support resulting after reduction at 350 degrees C in a catalyst with 25-nm particles. From basic Solution we obtained high dispersion of cobalt oil the CNF, probably related to the greater ion adsorption. After drying, Co3O4 crystallites were obtained that, after reduction at 350 degrees C, resulted ill a catalyst With 8-nm Co particles. Samples prepared in the high-pH experiment had 2-4 times higher cobalt-specific activity in the Fischer-Tropsch reaction than their low-pH counterparts. CNF Support materials combined with the high-pH deposition-precipitation technique hold considerable potential for cobalt-based Fischer-Tropsch Catalysis. (c) 2005 Elsevier Inc. All rights reserved.