CO 2 hydrogenation to C 5+ hydrocarbons over K‐promoted Fe/CNT catalyst: Effect of potassium on structure–activity relationship

Developing efficient catalysts for direct CO 2 hydrogenation to fuel hydrocarbons is of great significance for the effective utilization of CO 2 , and C 5+ selectivity is one critical indicator for the process economics. In this work, a series of K‐promoted Fe/CNT catalysts were prepared by the co‐impregnation method, and their catalytic performance for CO 2 hydrogenation was studied in a slurry‐bed reactor. As a result, CO 2 conversion and C 5+ selectivity showed positive correlation with the increase of K/Fe ratio from 0 to 0.3, but further increase of K/Fe ratio above 0.3 slightly affected its. The catalyst with a K/Fe molar ratio of 0.3 achieved the best performance with CO 2 conversion of 23.7% and C 5+ selectivity of 56%. In addition, the structure–activity relationship of the catalyst was discussed based on various characterization results. K‐modified catalysts presented a higher specific surface area and stronger CO 2 chemisorption, which helped to improve CO 2 conversion and C 5+ selectivity. However, excessive potassium loading caused a loss of specific surface area, reduction degree, and graphitization degree of the catalyst, which inhibited the CO 2 chemisorption and the formation of C 5+ hydrocarbons.