Promotion effect of single or mixed rare earths on cobalt-based catalysts for Fischer–Tropsch synthesis

A series of Co/γ-Al2O3 catalysts promoted with single or mixed rare earths were synthesized by impregnation method, and characterized via XRD, TPR, TPD, O2 titration and N2 adsorption–desorption techniques. The results showed that lanthanum, cerium, praseodymium and samarium played positive role on decreasing the production rate of methane, carbon dioxide, C2–C4 products and increasing C5+ selectivity, but neodymium had an opposite effect on the Co/γ-Al2O3 catalysts. In addition, the promotion with appropriate mixed rare earths was favorable for generating long-chain hydrocarbons over the Co/γ-Al2O3 catalyst, and the catalyst promoted with the Nd-removed mixed rare earths presented best catalytic performance.

As shown in the spectra of the catalysts promoted with the MRE oxides, the intensity of ceria diffraction peaks increased with the increase of the MRE oxides content. Compared with the spectra of the catalysts promoted with single rare earth oxide, the spectra of the catalysts promoted with MRE oxides also exhibited only the diffraction peaks of ceria. The reason was that other rare earth oxides had low content and were homogeneously dispersed on the γ-Al2O3 in amorphous phase.Figure optionsDownload as PowerPoint slideHighlights
► Single or mixed rare earths as Co/γ-Al2O3 catalyst promoters.
► Catalysts for Fischer-Tropsch synthesis.
► It is easily separable and reusable.
► Catalysts promoted with single La, Ce, Pr and Sm decreased generation rate of CH4 and CO2.
► Catalysts promoted with single La, Ce, Pr and Sm increased C5+ selectivity.
► Promotion with appropriate mixed rare earths was favorable for generating long-chain hydrocarbons.