The deactivation of Co/SiO2 catalyst for Fischer–Tropsch synthesis at different ratios of H2 to CO

The deactivation of Co/SiO2 catalyst for Fischer–Tropsch synthesis (FTS) at different H2 / CO ratios was investigated by XRD, FTIR, BET, XPS, TPR and H2 chemisorption. It was found that the deactivation rate of the catalyst increased with the rise of the H2 / CO ratio. The generation of silicates and/or hydrosilicates species was evidenced by TPR and XPS, and their amounts were monotonously enhanced with increasing H2 / CO ratio, which suggested that the deactivation was caused by the transformation of metallic cobalt into inactive silicates and the high partial pressure of H2 facilitated the formation of the silicates. Moreover, the percentage loss of the surface cobalt was larger than that of bulk cobalt, suggesting that the cobalt silicates and/or hydrosilicates species were formed mainly on the surface of the catalyst or in the small crystallites. For the catalyst run at H2 / CO ratio of 1, it was observed that the sintering also contributed to the catalyst deactivation, but it was a less important factor for the deactivation.