Factors influencing the activity of Co/Ca/TiO2 catalyst for Fischer–Tropsch synthesis

• The activity of Co/Ca/TiO2 catalyst depended on the crystal phase of TiO2, the reduction degree of Co and the surface area of Co metal.
• The catalyst prepared from rutile TiO2 was more active than that prepared from anatase TiO2.
• Co/Ca/TiO2 with the moderate reduction degree of Co (ca. 60%) and the high surface area of Co metal showed the high catalytic activity.

A series of Co/Ca/TiO2 catalysts with different reduction degree of Co and dispersion of Co metal were prepared by varying the temperature of hydrogen reduction pretreatment, the types of Co precursor and TiO2 support, and the Co-loading method. The activity of Co/Ca/TiO2 catalysts for Fischer–Tropsch (FT) synthesis largely depended on the crystal phase of TiO2 support, the reduction degree of Co and the surface area of Co metal. Rutile TiO2 was more effective than anatase TiO2 as the support TiO2 material. The optimum reduction degree of Co was around 60% and the excess reduction decreased the activity. The reaction rate for FT synthesis linearly increased with increasing the surface area of Co metal. The highest activity was obtained over the catalyst prepared from rutile TiO2 and Co(NO3)2·6H2O by the impregnation method, followed by the hydrogen reduction at 300 °C. The space time yield (STY) of C5+ products over the best Co/Ca/TiO2 catalyst was 1.3 and 3.5 times higher than those over Co/γ-Al2O3 and Co/SiO2, respectively, as the representative catalysts for FT synthesis.

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