Effect of A12O3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduc-tion/desorption (TPR/TPD) and Mossbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 °C, 1.5 MPa, 1000 h−1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.