C2 Oxygenate Synthesis via Fischer–Tropsch Synthesis on Co2C and Co/Co2C Interface Catalysts: How To Control the Catalyst Crystal Facet for Optimal Selectivity

Abstract

Density functional theory (DFT) analysis is used to shed light on the intricate effects of the Co2C and Co/Co2C catalyst crystal facets on the selectivity of the C2 oxygenate and hydrocarbon formation in Fischer–Tropsch synthesis. Three representative low-index Co2C (101), (110), and (111) surfaces, varying in surface energy from low and medium to high, are model examples of different Co2C exposed crystal facets. Since CHx (x = 1–3), CO, and H species are the key intermediates critical to the C2 oxygenate selectivity, all Fischer–Tropsch reactions related to CHx (x = 1–3) species, including CO insertion into CHx (x = 1–3) and CHx + CHy (x, y = 1–3) coupling to form C2 species (C2Hx and C2HxO), as well as the hydrogenation and dissociation of CHx (x = 1–3) to form C1 species (CH4 and C), are used as examples examined at a typical FTS temperature of 493 K. On Co2C (101) and (110) surfaces, CH and CH2 species are dominant form of the CHx species, CH self-coupling to C2H2 and CH coupling with CH2 to CH2CH is ...