Theoretical insights into formation of ethylene, propylene and butylene in Co2C (020) catalyzed FTO process.

• The mechanism of inhibiting the generation of methane and improving the selectivity of olefin on the Co(020) surface was found. • The paper investigates the reaction mechanism and elementary reaction kinetics of the cobalt carbide-catalysed FTO process by quantum mechanical methods. • The DFT study of Fischer–Tropsch synthesis of low carbon olefins on Co 2 C is limited to C 1 and C 2 species. In this paper, the generation mechanism of ethylene, propylene and butene will be further studied. Fischer–Tropsch Synthesis to lower olefins (FTO) is an important non-petroleum route to produce lower olefins. Nanoprisms Co 2 C has been discovered as a promising FTO catalyst possessing high selectivity to olefins and low CH 4 selectivity for its exposing (020) facet. Density Functional Theory (DFT) was used to understand the reason for inhibiting methane formation, the chain growth mechanism and dominant formation pathway of three main low olefins. The results show that the activation energy for CH 2 * to couple with CH* (0.51 eV) was much lower than that for further hydrogenation to form CH 3 * (0.66 eV), which was the key species to produce methane. Therefore, the mechanism inhibiting methane formation was Co 2 C(020) promoting CH 2 *-CH*coupling rather CH 2 * hydrogen. Moreover, it can be predict that the carbon chain would not grow too long, because the coupling activation energy for the C 1 -C 1 coupling, C 1 -C 2 coupling, C 1 -C 3 coupling were 0.51 eV, 0.54 eV and 0.69 eV, respectively. At last, it can be predicted that propylene was the easiest to produce, followed by ethylene and butylene, because their barrier energy were 1.58 eV, 1.64 eV and 2.12 eV, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]