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

An, Yunlei, Zhao, Yonghui, Yu, Fei, Lin, Tiejun, Lu, Yongwu, Li, Shenggang, Li, Zhengjia, Dai, Yuanyuan, Wang, Xinxing, Wang, Hui, Zhong, Liangshu, Sun, Yuhan
Journal of catalysis 2018 v.366 pp. 289-299
activation energy, alkenes, catalysts, catalytic activity, density functional theory, hydrogen, nanoprisms, nanospheres, synthesis gas
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% H₂-300 °C and 10% H₂-250 °C, Co₂C nanoprisms were formed after reaching the steady state. However, for the catalysts reduced by CO-300 °C and 10% H₂-400 °C, Co₂C nanospheres were found instead. Both Co₂C nanoprisms and nanospheres were present for the spent sample reduced by 10% H₂-350 °C. Kinetic study found Co₂C nanospheres to possess higher activation energy, and are more sensitive to hydrogen than Co₂C nanoprisms. Density functional theory (DFT) calculations were also performed to clarify the structure-performance relationship of Co₂C nanostructures for syngas conversion.