Effect of Pr Promotion on Co-Based Catalysts for Fischer–Tropsch Synthesis to Olefins

Fischer–Tropsch synthesis to olefins (FTO) from syngas with low CO2 selectivity achieves great attention but still remains challenging. Herein, Pr-promoted metallic Co catalysts were applied to the FTO reaction, and the promotional effect was investigated in detail. All Pr-promoted catalysts displayed higher olefin selectivity and lower methane selectivity compared with the unpromoted Co-based catalysts. Moreover, the CO2 selectivity was significantly suppressed, owing to the low intrinsic activity of metallic Co sites for the water–gas shift reaction (WGSR). The optimal Pr loading was found to be 10 wt %, which resulted in a high olefin selectivity of 44.1% and a low CO2 selectivity of 1.1%. The structural characterization revealed that the addition of Pr altered the electronic state of Co species, leading to enhanced CO adsorption and a low H/C ratio on the catalyst surface. Furthermore, secondary hydrogenation activity was also inhibited by adding the Pr promoter, which is favorable for olefin production.