Effect of manganese incorporation manner on an iron-based catalyst for Fischer-Tropsch synthesis

A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basicity of an iron-based Fischer-Tropsch synthesis (FTS) catalyst. The catalyst samples were characterized by N-2 physisorption, X-ray photoelectron spectroscopy (XPS), H-2 (or CO) temperature-programmed reduction (TPR), CO2 temperature-programmed desorption (TPD), and Mossbauer spectroscopy. The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that the manganese promoter incorporated by using the coprecipitation method could improve the dispersion of iron oxide, and decrease the size of the iron oxide crystallite. The manganese incorporated with the impregnation method is enriched on the catalyst's surface. The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H-2, CO, and syngas because of the excessive enrichment of manganese on the catalyst surface. The catalyst added manganese using the coprecipitation method has the highest CO conversion (51.9%) and the lowest selectivity for heavy hydrocarbons (C12+).