Industrial & Engineering Chemistry Research, Vol.59, No.33, 14598-14605, 2020
Effect of Rare-Earth Promoters on Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis
FeMn catalysts that were either unpromoted or promoted by five rare-earth metals (La, Ce, Nd, Sm, and Eu) for Fischer-Tropsch synthesis (FTS) were prepared by the coprecipitation method and characterized by XRD, N-2 adsorption, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, CO-temperature-programmed desorption (CO-TPD), H-2-TPD, CO2-TPD, and Mossbauer spectroscopy (MES). The results showed that all five rareearth metals could promote the performance of the catalysts, whereas the Nd promoter showed a unique promoting effect. The CO-TPD and MES results revealed that the sample FeMnNd had the highest CO chemisorption ability and formed the most Fe5C2, in the FTS reaction. Moreover, the sample FeMnNd achieved the strongest surface alkalinity and the weakest chemical adsorption of hydrogen, as confirmed by CO2-TPD and H-2-TPD, respectively. Based on the results of FTS performance, the FeMnNd catalyst exhibited the highest CO conversion of 74.9%, a C2-4 = selectivity of 36.0%, an 0/P ratio of 3.96, and the lowest C-5(+) selectivity of 34.3%.