Morphology control of Co2C nanostructures via the reduction process for direct production of lower olefins from syngas.

Graphical abstract Morphology control of Co 2 C nanostructures via reduction process was developed for direct production of lower olefins from syngas. The structure-performance of the as-obtained Co 2 C nanoprisms and nanospheres were investigated based on kinetic study and DFT calculations. Highlights • Morphology control of Co 2 C nanostructures via reduction process was developed. • Co 2 C nanoprisms or nanospheres can be obtained by controlling the reduction process. • The structure-performance of the as-obtained Co 2 C nanoprisms and nanospheres was investigated. • Co 2 C nanoprisms possessed higher activity and lower methane selectivity than Co 2 C nanospheres. • The product distribution of Co 2 C nanoprisms deviated from the ASF law. Abstract Fischer-Tropsch to olefins (FTO) is recognized as a surface-catalyzed structure-sensitive reaction, and the catalytic performance is strongly influenced by the morphology and exposed facets of the active phase. Here we report the effect of the reduction process on the morphology of the active phase and the catalytic performance for FTO over the CoMn catalyst. For the catalysts reduced by 10% CO-300 °C, 10% H 2 -300 °C and 10% H 2 -250 °C, Co 2 C nanoprisms were formed after reaching the steady state. However, for the catalysts reduced by CO-300 °C and 10% H 2 -400 °C, Co 2 C nanospheres were found instead. Both Co 2 C nanoprisms and nanospheres were present for the spent sample reduced by 10% H 2 -350 °C. Kinetic study found Co 2 C nanospheres to possess higher activation energy, and are more sensitive to hydrogen than Co 2 C nanoprisms. Density functional theory (DFT) calculations were also performed to clarify the structure-performance relationship of Co 2 C nanostructures for syngas conversion. [ABSTRACT FROM AUTHOR]