Studies of the Fischer-Tropsch reaction on Co(0001)

Interactions of hydrogen with alkali promoted Ru/SiO₂ catalysts: A proton NMR study

“…For example, Hrbek (37) reported that the work function of a Ru(OOI) surface exhibited a minimum as a function of alkali coverage. Addition of hydrogen did not influence the work function of an alkali precovered Ru (001 ) surface (38) which was consistent with the results determined for hydrogen on a clean surface (39).…”

“…Ponec (30 and references therein) reported evidence supporting an ensemble requirement for CO dissociation on Ni and Ru after studies on corresponding Cu alloys of these metals. Studies on supported Ni, Co and Ru catalysts as well as the single crystal surfaces of these metals yielded contradictory results on the structure sensitivity of the Fischer Tropsch synthesis reaction (36)(37)(38)(39)(40). For example, Geerlings et al (39)(40) reported that longer chain hydrocarbon fragments are formed on a zig zag grooved Co(1120) surface whereas on stepped Co(1012) and close packed Co(OOOI) surfaces mainly CHx=i.3 species are observed.…”

CO adsorption on cobalt: Prediction of stable surface phases

“…Since FT synthesis is performed at a high pressure of about 20 bar and a rather low temperature of 220°C, the CO coverage under reaction conditions is high. The high CO coverage has a pronounced effect on the reaction kinetics and selectivity [14,15] and accounting for the CO coverage and surface structure under reaction conditions is crucial to understand and control catalyst activity and selectivity.The adsorption of CO on Co(0001) has been studied with a wide range of experimental techniques [1,8,[16][17][18][19]. For coverages up to 1/3 ML, an isosteric heat of adsorption of 128 kJ/mol has been measured.…”

“…The adsorption of CO on Co(0001) has been studied with a wide range of experimental techniques [1,8,[16][17][18][19]. For coverages up to 1/3 ML, an isosteric heat of adsorption of 128 kJ/mol has been measured.…”

“…Low energy electron diffraction (LEED) studies on Co(0001) show a well-ordered (M3 × M3)R30°structure with CO at top sites at 100 K and for an exposure of 1.2 L [8], at 160 K and for an exposure of 1.25 L [20], at 180 K and for an exposure of 1.25 L [21], and at 300 K and for a CO pressure of 7 × 10 −9 mbar [1]. Polarization modulation reflection-adsorption infrared spectroscopy (PM-RAIRS) [17] demonstrates that this structure persists for pressures up to 1 mbar at 300 K. Both PM-RAIRS and high-resolution electron energy loss spectroscopy (HREELS) show a single sharp IR peak near 2000 cm −1 , corresponding to CO at top sites [16,17]. When the CO exposure is increased to 2.2 L at 100 K [8], or to 3.5 L at 180 K [21], the LEED spectra show a transition to a (2M3 × 2M3)R30°structure with one atop CO molecule and six bridging CO molecules per unit cell, corresponding to a coverage of 7/12 ML.…”