Cobalt particle size effects in Fischer–Tropsch synthesis: structural and in situ spectroscopic characterisation on reverse micelle-synthesised Co/ITQ-2 model catalysts

A Highly Active and Selective Manganese Oxide Promoted Cobalt-on-Silica Fischer–Tropsch Catalyst

“…For the Co/Pt/SiO 2 catalyst relatively low C 5? -selectivities were found, although higher values (up to 48 wt%) were obtained at higher ([450 8C) reduction temperatures possibly related to the presence of larger Co particles [2][3][4].…”

“…Moreover, next to the peak at 2,057 cm -1 , a second distinct peak of linearly bonded CO is observed at around 2,012 cm -1 region. Whereas the first peak (2,057 cm -1 ) is ascribed to CO adsorption on fcc cobalt [37], the latter peak has been attributed to the linear adsorption of CO on low-index surface crystallographic planes or corners and steps sites with coordinatively unsaturated sites [4,38,39]. This indicates that MnOpromoted catalysts exhibit a different cobalt surface structure as compared to unpromoted catalysts.…”

“…From this back-switch, the residence times of CO and CH x were calculated. In this case the CH x intermediates represent the surface species which eventually produce CH 4 . A detailed description of the transient analyses has been published elsewhere [30].…”

“…-selectivity of the MnO promoted catalysts and the air-calcined Co/Pt/SiO 2 catalysts, the CH x coverage (H 2 /CO = 10, 210°C, 1.85 bar) was plotted versus the CH 4 and C 5? -selectivities both determined via GC analyses (H 2 /CO = 2, 220°C, 1 bar) in Fig.…”

“…[1][2][3][4] A recent example of improving the catalytic activity using this methodology is provided in a previous contribution from our laboratory, where a cobalt-on-silica catalyst was synthesized by an impregnation and drying step, followed by calcination of cobalt nitrate precursor in a flow of NO/He [5,6]. This method yielded a surfaceweighted cobalt particle size of *5 nm with a narrow particle size distribution.…”