Effect of na addition on iron-based catalyst for fischer-tropsch synthesis

A series of Fe-based catalysts for Fischer-Tropsch synthesis (FTS) were prepared by impregnation of the FeCuK/SiO2 precursor with different amounts of sodium acetate. The catalysts were characterized by atomic emission spectroscopy, N-2 adsorption, temperature-programmed reduction, and Mossbauer effect spectroscopy. The catalytic performance for FTS was investigated in a continuous stirred tank slurry reactor under reaction conditions of H-2/CO = 0. 67, WHSV = 2 000 h(-1), 1. 5 MPa, and 250 degrees C. A low level of Na loading increases the surface area of the catalyst and enhances the dispersion of iron species in the catalyst, but excessive addition of Na decreases the surface area. Incorporation of Na in the catalyst inhibits the first step reduction in H-2 and promotes carburization in CO or syngas. The catalysts with different Na loadings display various FTS activity and are deactivated after 500 h on stream to some extent. Moreover, the reaction results indicate that the addition of Na slightly affects water-gas shift activity, suppresses methane selectivity, and promotes light alkene selectivity.