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Abstract: The effect of noble metal promoters (atomic ratio of promoter to Co=1/170) on the activity and selectivity of a 25%Co/Al2O3 catalyst was studied at a similar CO conversion level of 50% at 493K, 2.2MPa and H2/CO=2.1 using a 1-L continuously stirred tank reactor (CSTR). The results show that all promoted catalysts exhibited markedly higher initial CO conversion rates on a per gram catalyst basis than the unpromoted one, which was ascribed to increased Co site density when the promoters were present. This is because the Re, Ru, Pt and unpromoted Co catalysts give essentially the same initial Co TOF values of 0.092–0.105s−1 (based on hydrogen-chemisorption). However, the initial Co TOF value for the Pd-Co catalyst was about 40% lower, which might be caused by Pd atoms segregating on the Co surface and partially blocking Co sites. At 50% CO conversion, Re and Ru promoters decreased CH4 selectivity and increased C5+ selectivity by nearly the same extent, whereas the opposite effect was observed for Pd and Pt promoters. The Re and Ru promoters had less of an impact on C2–C4 olefin selectivity (7.5–60%), but suppressed the secondary reaction of 1-C4 olefin (from 14.3 to 9%) compared to the unpromoted one; however, the addition of Pd and Pt promoters resulted in lower olefin selectivity (4.4–55%) but higher 2-C4 olefin selectivity (14.3 to 27–31%). Pt promotion had a negligible effect on C4 olefin isomerization. The selectivity results were reproducible. Both Pt and Pd promoters slightly increased WGS activity, whereas Re and Ru promoters had a negligible effect. The Pd and Pt promoters were observed to slightly enhance oxygenate formation, while Re and Ru slightly decreased it. [Copyright &y& Elsevier]

Activity and selectivity of H2, CO, syngas pretreated and non-pretreated Ruhrchemie catalyst (100 Fe/5 Cu/4.2 K/25 SiO2 on mass basis) used for the Fischer–Tropsch synthesis (FTS) were studied in a stirred tank slurry reactor (STSR). Catalyst activity was the highest after the CO and H2 pretreatments, whereas the non-pretreated catalyst was the least active. Methane selectivities on the CO, syngas reduced and unreduced catalysts were similar (3.9–4.3 wt.%), and lower than that on the H2 reduced catalyst (5.3%). Liquid plus wax (C5+ hydrocarbons) selectivity was high in all four tests (∼80%). The H2 reduced catalyst produced less olefins and had the highest 2-olefin selectivity, whereas the non-pretreated and CO pretreated catalysts had the highest olefin content and the lowest 2-olefin selectivity. Attrition strength of the Ruhrchemie catalyst after 429 h of FTS was found to be adequate under severe hydrodynamic conditions encountered in the STSR. Reduction in the volume moment diameter was 14.3%, whereas, increase in fraction of particles smaller than 10 μm was only 2.6%. [Copyright &y& Elsevier]