Ru promoted cobalt catalyst on γ-Al2O3 support: Influence of pre-synthesized nanoparticles on Fischer–Tropsch reaction

Effects of Ru promoted cobalt oxide nanoparticles on γ-Al2O3 supported catalysts were studied for Fischer–Tropsch reaction. Homogeneously sized cobalt oxide nanoparticles with the different amount of ruthenium promoter were prepared by solvothermal method using oleic acid as capping agent. Pre-synthesized CoRuOx nanoparticles were then impregnated on γ-Al2O3 support to prepare 5CoxRu/100Al2O3 catalysts (5CoxRuAl), with the amount of ruthenium x = 0 to 0.1. The catalysts were characterized by XRD, TEM, TPR, EDX, H2 chemisorption and O2 titration methods and compared with the catalyst prepared by conventional impregnation method, i.e. i-5Co0.05RuAl. Interestingly, catalysts prepared by nanoparticle impregnation method showed higher H2 uptake and better reducibility with the concomitant increase in the activity due to the homogeneous dispersion of the Ru promoter across entire the nanoparticles as compared to the catalyst prepared by conventional impregnation method. The intimate contact between cobalt and ruthenium enhanced the site density of cobalt which was responsible for the promotional results in the case of 5CoxRuAl catalysts.

H2-TPR profiles of 5CoxRuAl catalysts show the decrease in the reduction temperature with the increase in the Ru content from 0 to 0.05%. Further increase in the promoter concentration resulted in the segregation of Ru and 5Co0.1RuAl catalyst shows no effect of promoter. 5Co0.05RuAl catalyst shows much lower reduction temperature as compared to conventionally prepared i-5Co0.05RuAl catalyst, even though the amounts of cobalt and ruthenium are the same. This is due to the pre-synthesis of CoRuOx nanoparticles in the case of former catalyst which enhances the bimetallic interaction of Co and Ru and resultant FT activity.Figure optionsDownload high-quality image (114 K)Download as PowerPoint slideHighlights
► Controlled size CoRuOx nanoparticles were embedded on γ-Al2O3.
► Intimate contact between Ru and Co increased by pre-synthesis of nanoparticles.
► 5CoxRuAl catalysts show superior activity in Fischer–Tropsch reaction.
► Conventional catalyst with equal amount of Co and Ru show comparatively poor result.
► Increased interaction of Ru and Co in 5CoxRuAl enhances catalyst activity.