According to Saib et al. [14], activity of the supported cobalt catalysts in the FischereTropsch synthesis seems to be a function of the metal dispersion and the extent of deactivation during the FischereTropsch synthesis while the C5þ-selectivity could be described using the reactant transport model proposed by Iglesia et al. [12] and is a function of conversion. Xiong et al. [15] studying the role of pore size in Co/SBA-15 catalysts also concluded that catalysts with larger pores led to larger cobalt cluster size,lower dispersion and higher reducibility and gave rise to morembridge type CO adsorbed on FTS. They also stated that catalysts with larger cobalt cluster size showed higher C5þ selectivity in the FTS. The reported results are very solid and clear evidences have been shown in all cases supporting the author claims. However, we believe that an additional factor i.e. shape selectivity also plays a
role.