Role of supports in cobalt-based catalysts for Fischer-Tropsch synthesis of heavy hydrocarbons

The cobalt-based catalysts for F-T synthesis of heavy hydrocarbons were tested in a down-flow fixed-bed reactor and characterized by using BET, TPR, H-2-TPD, NH3-TPD, XRD, and XPS. The results indicated that the activity and selectivity of the catalysts were influenced by the type and the surface properties of the supports and the reaction conditions. There were different product distributions over the catalysts with different supports. The heavy hydrocarbons over Co/ZrO2, were amassed between C-10 and C-25. The C5+ products over Co/SiO2 collected in C(9)similar toC(18). However, the heavy hydrocarbons over Co/Al2O3 centered in C(6)similar toC(13). It was found that the acidity affected the active phase dispersion from the NH3-TPD and XRD results. The TPR profiles showed that there was the interaction between cobalt and,support and the Co/Al2O3 catalyst had the lowest reduction degree. The support effect on the catalytic reaction had a direct influence on the product distribution and chain growing probability. It was evident that the supports also affected the surface concentration of active components. However, the surface concentration of cobalt oxides did not increase with the rise of the support surface area and had no linear relationship with the catalytic activity.