It is well established that the activity and selectivity of Co-based catalysts for Fischer-Tropsch synthesis are affected by metal oxide promoters, such as TiOx, MnOx, and ZrOx. This study was carried out with the aim of establishing the manner in which the promoter interacts with SiO2 supported Co and the influence of the promoter on the extent of Co reduction, the activity for CO consumption, and the distribution of products formed. High resolution STEM images and elemental maps obtained by energy dispersion spectroscopy (EDS) were acquired to identify the correlation of the promoter oxide with the Co nanoparticles. These efforts were complemented by XANES analyses of the Co and promoter elements in order to establish their oxidation states. Additional evidence for the effects of the promoter was obtained from IR and adsorption studies. These results show that the in the case of MnOx, Mn tends to be closely associated with the Co, but in the case of ZrOx, Zr is more highly dispersed over the support. Both promoters suppress the formation of CH4 and enhance the formation of C5+ products, with ZrOx being more effective than MnOx at the same level of promotion. The kinetics of CO hydrogenation are also affected by the promoter. For both promoters, the promoter appears to increase the adsorption of CO relative to H2.

Effects of metal oxide promoters on the activity, kinetics, and selectivity of co-based Fischer-Tropsch catalysts

249th National Meeting (2015)

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