Deactivation of Cobalt-Based Catalysts for Fischer-Tropsch Synthesis

Stability tests of Co/SiO2,Co/Ru/SiO2,and hydrophobically-organically modified Co/Ru/SiO2 (Co/Ru/SiO2-S) for Fischer-Tropsch synthesis were carried out. As the time on stream went on,CO conversion decreased in all the cases. The growth of cobalt crystallite and the formation of cobalt silicates species were the reasons for Co/SiO2 deactivation,while the deactivation of Co/Ru/SiO2 and Co/Ru/SiO2-S was only attributed to the growth of cobalt crystallite. The stability of the catalysts was in order of Co/Ru/SiO2-S Co/SiO2 Co/Ru/SiO2. Compared with Co/SiO2,the faster deactivation rate for Co/Ru/SiO2 was ascribed to the agglomeration of smaller metal clusters,which were more unstable than the larger metal clusters and therefore more susceptible to sintering processes. Co/Ru/SiO2-S showed the best stability because of no formation of cobalt silicates species and the slow growth of cobalt crystallite.