Reduced cobalt phases of ZrO₂ and Ru/ZrO₂ promoted cobalt catalysts and product distributions from Fischer–Tropsch synthesis

Highlights: • Ru/ZrO₂, ZrO₂ promoted Co/SiO₂ for FTS were reduced by time resolved XANES. • Reduced catalysts resulted from XANES reduction showed the mixed phases of Co, CoO. • The highest percentages of CoO resulted from the high ZrO₂ promoted Co/SiO₂. • Product distributions of 1-alkenes, iso-alkanes indicated sites for FTS and the 2° reaction. • Alkene readsorption were high corresponding to the high CoO forming branched alkanes. - Abstract: Co/SiO₂ catalysts were promoted with 4% and 8% ZrO₂. Small amounts (0.07%) of Ru were impregnated onto 4%ZrO₂/Co/SiO₂. Catalysts resulting from time-resolved XANES reduction showed mixed phases of Co and CoO, with the highest percentages of Co resulting from Ru/4%ZrO₂/Co/SiO₂ and the highest percentages of CoO resulting from 8%ZrO₂/Co/SiO₂. Product distributions of n-alkanes, iso-alkanes and alkenes during Fischer–Tropsch Synthesis (FTS) were used to investigate the catalyst performance of 4%ZrO₂/Co/SiO₂ 8%ZrO₂/Co/SiO₂ and Ru/4%ZrO₂/Co/SiO₂. FTS steady state was studied by growth probabilities of n-alkane products. No 1-alkene was produced from Ru/4%ZrO₂/Co/SiO₂, indicating high availability of Fischer–Tropsch sites for long chain hydrocarbon growth, despite high methanation. Branched alkanes produced from the secondary reaction were related to the high CoO percentages on 8%ZrO₂/Co/SiO₂. Alkene readsorption sites were high, corresponding to the high CoO percentages, causing a high probability of forming branched alkane products