Density Functional Calculations to Study the Mechanism of the Fischer–Tropsch Reaction on Fe(111) and W(111) Surfaces

CO Dissociation at Vacancy Sites on Hägg Iron Carbide: Direct Versus Hydrogen-Assisted Routes Investigated with DFT

“…It was concluded that both the direct and H-assisted path via HCO formation could contribute depending on the reaction conditions. On Fe(111), the direct formation of COH was calculated to have a prohibitively high activation energy of 2.46 eV, while both direct and H-assisted CO dissociation via formation of HCO had similar lower overall energy barriers [42]. This latter result was borne out in a separate study on Fe(111) at higher hydrogen coverages [43].…”

“…This latter result was borne out in a separate study on Fe(111) at higher hydrogen coverages [43]. Subsequent hydrogenation of formyl to form CH 2 O or HCOH was also calculated [42]; both reactions were concluded to be thermodynamically and kinetically less favourable than dissociation of HCO to form CH and O on the Fe(111) surface. Ojeda et al studied CO activation on Fe(110) at elevated CO coverage using DFT in combination with kinetic measurements on an Fe catalyst [20,44].…”

“…Ojeda et al studied CO activation on Fe(110) at elevated CO coverage using DFT in combination with kinetic measurements on an Fe catalyst [20,44]. It was concluded that both direct and H-assisted paths are active in Fe-FT synthesis, the latter being the dominant route and involving formation of HCO and HCOH intermediates [20], in contrast to conclusions drawn on Fe(111) [42]. Coadsorbed CO was found to significantly alter the stability of intermediates adsorbed on the surface.…”

Characterization of Modified Fischer–Tropsch Catalysts Promoted with Alkaline Metals for Higher Alcohol Synthesis

“…The highest selectivity towards hydrocarbons corresponds to CuCoCrZnLi at 300°C and to CuCoCrLi at 350°C. Sodium as promoter may contribute to the growth of saturated chain and also activate oxygen elimination via H 2 O followed oxygenates products [1][2][3][4][5][6][7]. This is confirmed by the low yields of CO 2 and the high amounts of methanol obtained at 300°C over CuCoCrNa and at 350°C over CuCoCrZnNa.…”

“…The excess of oxygen is removes from the catalyst surface via CO 2 or H 2 O [1][2][3][4][5][6][7]. This mechanism works well within a narrow temperature range, 500-700K, producing low-molecular-weight hydrocarbons and small amounts of high-molecular-weight hydrocarbons as well as oxygenates [3].…”