Understanding reaction-induced restructuring of well-defined FexOyCz compositions and its effect on CO2 hydrogenation

Herein, we provide fundamentals relevant for the development of Fe-based catalysts for CO2 hydrogenation to higher hydrocarbons. It was possible owing to preparation of well-defined FexOyCz compositions through controlled decomposition of iron oxalate, determination of their composition under CO2-FT reaction and catalytic tests in a broad range of CO2 conversion. Such steady-state composition changes along the catalyst bed. The changes and their strength depend on the initial phase composition. In addition to the reaction-induced catalyst restructuring, reaction pathways leading from CO2 to CO, CH4 and higher hydrocarbons were elucidated. A correlation between them and the steady-state composition was established and offers the possibility for tailored catalyst design and preparation. Our best performing promoter-free Fe-based catalyst shows the selectivity to CH4 below 10 %, while the selectivity to C2+-hydrocarbons is about 50 % at CO2 conversion of about 25 % and 300 degrees C. The olefin to paraffin ratio among C-2-C-4 hydrocarbons is 5.5.

Automated summary

This study provides fundamental knowledge for developing Fe-based catalysts for CO2 hydrogenation to higher hydrocarbons, with well-defined compositions prepared through controlled decomposition of iron oxalate. The research also elucidates the pathways from CO2 to CO, CH4, and higher hydrocarbons, establishing a correlation between reaction pathways and steady-state composition for tailored catalyst design and preparation. The best performing Fe-based catalyst achieves a selectivity to CH4 below 10%, with a selectivity to C2+-hydrocarbons around 50% at 25% CO2 conversion and 300 degrees C, with an olefin to paraffin ratio of 5.5 among C-2-C-4 hydrocarbons.