Effect of the support on cobalt carbide catalysts for sustainable production of olefins from syngas
ABSTRACT Co 2 C-based catalysts with SiO 2 , γ-Al 2 O 3 , and carbon nanotubes (CNTs) as support materials were prepared and evaluated for the Fischer-Tropsch to olefin (FTO) reaction. The combination of catalytic performance and structure characterization indicates that the cobalt-support interaction has a great influence on the Co 2 C morphology and catalytic performance. The CNT support facilitates the formation of a CoMn composite oxide during calcination , and Co 2 C nanoprisms were observed in the spent catalysts, resulting in a product distribution that greatly deviates from the classical Anderson-Schulz-Flory (ASF) distribution, where only 2.4 C% methane was generated. The Co 3 O 4 phase for SiO 2 - and γ-Al 2 O 3 -supported catalysts was observed in the calcined sample. After reduction, CoO, MnO, and low-valence CoMn composite oxide were generated in the γ-Al 2 O 3 -supported sample, and both Co 2 C nanospheres and nanoprisms were identified in the corresponding spent catalyst. However, only separated phases of CoO and MnO were found in the reduced sample supported by SiO 2 , and Co 2 C nanospheres were detected in the spent catalyst without the evidence of any Co 2 C nanoprisms. The Co 2 C nanospheres led to a relatively high methane selectivity of 5.8 C% and 12.0 C% of the γ-Al 2 O 3 - and SiO 2 -supported catalysts, respectively. These results suggest that a relatively weak cobalt-support interaction is necessary for the formation of the CoMn composite oxide during calcination, which benefits the formation of Co 2 C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas.
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