Carbon-encapsulated metallic Co nanoparticles for Fischer-Tropsch to olefins with low CO2 selectivity

Tuning Fischer-Tropsch synthesis products of metallic Co-based catalysts from paraffins to value-added olefins chemicals attracts great attention but remains challenging. Herein, we succeed in designing the carbon layers confined cobalt metal core-shell nanocatalyst (Co@C) via a reduction-carburization-pyrolysis (RCP) pretreatment of Co/SiO 2 , which exhibits highly efficient for Fischer-Tropsch to olefins (FTO) with negligible Water-Gas-Shift activity. At 250 °C and 5 bar, 56.4 % of olefins selectivity and limited CO 2 selectivity (5.8 %) are achieved for Mn-promoted Co@C nanocatalyst with at least 200 h of stability running. The electronic effect of carbon layers and Mn promoter as well as the confinement structure tailor the local chemical environment and weaken the hydrogenation ability of Co metal sites, thus improving the selectivity toward olefins while largely reducing the formation of CH 4 and CO 2 . This work develops an effective strategy for the rational design of highly active and stable metallic Co-based FTO catalysts with high carbon efficiency. • Carbon layers encapsulating Co metallic nanoparticles (Co@C) was successfully designed. • Reduction-carburization-pyrolysis (RCP) strategy was effective in fabricating Co@C structure. • Co@C nanocatalyst was favorable for olefins production instead of paraffins during FTS process. • Features of negligible WGSR activity and high carbon efficiency were observed for Co@C nanocatalyst. • Both electronic effect of carbon layers and Mn promoter could weaken hydrogenation ability of Co metal.