Effects of phosphorus and saccharide on size, shape, and reducibility of Fischer–Tropsch catalysts for slurry phase and fixed-bed reactions

Saccharide was incorporated into Co/Al2O3 by impregnating sucrose and a cobalt precursor on a phosphorus-treated γ-Al2O3 support (P-Al2O3), to control the catalyst size, shape, and reducibility. The effects of P-Al2O3 on the relationship between C5+ productivity, dispersion, and reducibility were investigated and compared with our previous work based on the high surface area γ-Al2O3. Powder X-ray diffraction results for Co/P-Al2O3 revealed that the addition of P increased the average size of the cobalt oxide crystals due to weakened interactions between the metal and the support, which led to the increased reducibility while compromising the dispersion. The extraordinarily enhanced hydrothermal stability of the catalysts was corroborated with the help of FT-IR analysis. Activity tests were conducted in a fixed-bed reactor as well as in a slurry phase reactor charged with Co/P-Al2O3 catalysts to investigate the reactor behavior. The addition of a saccharide, such as sucrose, efficiently increased the dispersion capability and regulated crystal shape to overcome the lowered dispersion caused by phosphorus treatment. The effect of sucrose on crystal size and shape of Co/P-Al2O3 was verified through TEM imaging and XRD analysis. The control of crystal size and shape was found to be crucial to attain maximum productivity, in addition to dispersion and reducibility.

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► Saccharide and phosphorus were incorporated into cobalt catalyst to control size, shape as well as reducibility.
► The extraordinarily enhanced hydrothermal stability as well as reducibility of P-treated catalyst was corroborated.
► Activity tests were conducted in a fixed-bed reactor as well as in a slurry phase reactor.