The effect of pretreatment on SiO2 for Co-based Fischer-Tropsch synthesis catalysts: a study of the reduction pathway.

The reduction pathway of Co catalysts supported on untreated SiO2 along with two pretreated SiO2 support materials was investigated. In situ XRD studies clearly showed the likely reduction pathways of the cobalt oxides on the untreated SiO2, ethylene glycol pretreated SiO2, and annealing pretreated SiO2 supports. Ethylene glycol pretreated SiO2-supported Co (Co/E–SiO2) catalyst showed smaller metal crystallites, highly dispersed Co and high Co(hcp)/Co(fcc) ratio because of the high percentage of non-H-bonded silanols; however, the high percentage of the non-H-bonded silanols created a strong Co-SiO2 interaction which caused a low degree of reduction of CoO resulting in lower FT activity. In contrast, the annealing pretreated SiO2-supported Co (Co/A–SiO2) catalyst did not significantly increase the percentage of non-H-bonded silanols and Co(hcp)/Co(fcc) ratio when compared with Co/E–SiO2, but it exhibited a better catalytic activity during FTS. [ABSTRACT FROM AUTHOR]