High-yield pentanes-plus production via hydrogenation of carbon dioxide: Revealing new roles of zirconia as promoter of iron catalyst with long-term stability

The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO₂ to C₅₊ hydrocarbons. However, the roles of metal oxide promoter for Fe catalysts, particularly ZrO₂, have rarely been investigated. To plug this knowledge gap, a new Fe catalyst promoted with Na and partially reduced ZrO_x (Na-FeZrO_x-9) was developed in this study; the catalyst helped produce C₅₊ hydrocarbons in remarkably high yield (26.3% at 360 °C). In contrast to ZrO_x-free Fe-oxide, Na-FeZrO_x-9 exhibited long-term stability for CO₂ hydrogenation (750 h on-stream). The findings revealed multiple roles of ZrO_x. Notably, ZrO_x decorated the Fe-oxide particles after calcination, thereby suppressing excess particle aggregation during the reaction, and acted as a “coke remover” to eliminate the carbon deposited on the catalyst surface. Additionally, oxygen vacancy (O_v) sites in ZrO_x and electron transfer from ZrO_x to Fe sites facilitated the adsorption of CO₂ at the Zr-Fe interface.