Revisiting the Impact of CO2 on the Activity and Selectivity of Cobalt-Based Catalysts for Fischer–Tropsch Synthesis Under Industrial-Relevant Conditions

Understanding the impact of CO2 on cobalt-based Fischer–Tropsch synthesis catalysts is critical for optimizing system efficiency, particularly in scenarios employing solid oxide electrolysis cells for syngas production, given the inevitable incorporation of CO2 into syngas during the SOEC co-electrolysis process. In this study, we conducted comparative experiments using a Co-Re/γ-Al2O3 catalyst in a fixed-bed reactor under industrial conditions (2 MPa, 493 K, GHSV = 6000–8000 Ncm3/gcat/h), varying the feed gas compositions of H2, CO, CO2, and Ar. At an H2/CO ratio of 2, the addition of CO2 led to a progressive decline in catalyst performance, attributed to carbon deposition and cobalt carbide formation, as confirmed by Raman spectroscopy, XRD analyses, and TPH. Furthermore, DFT calculations combined with ab initio atomistic thermodynamics (AIAT) were performed to gain molecular insights into the loss of catalyst activity arising from multiple factors, including (sub)surface carbon derived from CO or CO2, polymeric carbon, and carbide formation.