The deactivation of Co/SiO_2 catalyst for Fischer-Tropsch synthesis at different ratios of H_2 to CO

摘要

The deactivation of Co/SiO_2 catalyst for Fischer-Tropsch synthesis (FTS)at different H_2/CO ratios was investigated by XRD,FTIR,BET,XPS,TPR and H_2 chemisorption.It was found that the deactivation rate of the catalyst increased with the rise of the H_2/CO ratio.The generation of silicates and/or hydrosilicates species was evidenced by TPR and XPS,and their amounts were monotonously enhanced with increasing H_2/CO ratio,which suggested that the deactivation was caused by the transformation of metallic cobalt into inactive silicates and the high partial pressure of H_2 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 H_2/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.