Increased CO2 hydrogenation to liquid products using Promoted Iron Catalysts

The steady increase of carbon dioxide (CO₂) emissions into the atmosphere caused by human activities contributes to harmful global warming and climate change. The utilization of CO₂ as a feedstock for producing chemicals not only contributes to reducing global climate change caused by increasing CO₂ emissions, but also opens avenues for exploration of catalytic and industrial development opportunities. CO₂ hydrogenation to hydrocarbons is a modification of Fischer–Tropsch synthesis (FTS), where CO₂ is a reactant instead of carbon monoxide (CO). Hydrogenation of CO₂ is carried out with catalysts that have been demonstrated to be active for the FTS reaction. The effect of potassium (K), rubidium (Rb), and cesium (Cs) on the performance of precipitated iron-based catalysts was explored for carbon dioxide hydrogenation. Under similar reaction conditions, Cs and Rb promoted catalysts exhibited the highest initial CO₂ conversions to higher hydrocarbons. However, at steady state conversion, all three catalysts exhibited similar CO₂ conversions and selectivities. Results indicate a synergistic effect brought on by these promoters that, if balanced, could potentially yield superior CO₂ hydrogenation catalysts. With the aim of developing a better catalyst for CO₂ utilization, these iron catalysts initially reveal a turn in the right direction. However, the shortcomings indicate that carbon deposition could be the main problem. If coking could be mitigated, while still using the basicity strength of these alkali metal promoters, a much more effective, and cheaper, catalyst capable of converting CO­₂ to_­ higher hydrocarbons could be implemented.

Keywords: CO₂ hydrogenation; alkali promoter; iron-based catalysts; activity; product selectivity.