The analysis of Lapszewicz data seems to suggest that this change of adsorption patterns is related to the particle size which in turn relates very well with pore diameter. Ernst et al. [10] studied the FT activity and selectivity of Co/SiO2 prepared by a solegel technique in acid and base media. It was found that the activity for FT increased with the specific surface area, and the selectivity for higher molecular weight hydrocarbon was favored when the pore diameter was lower than 4 nm. Khodakovet al.