Fe-MOF-derived highly active catalysts for carbon dioxide hydrogenation to valuable hydrocarbons

- Fe-MOF-derived catalysts were prepared by one-step pyrolyzing Fe-MIL-88B.
- Iron species could variously transform under the reaction conditions, resulting in different catalytic performances.
- Fe-MOF-derived catalysts exhibited high selectivity of C5+ hydrocarbons and the addition of K made the ratio of olefins to paraffins increase to 5.5.
- The presence of appropriate amount of Fe3O4 and χ-Fe5C2 was beneficial to the reaction. However, metallic iron and/or θ-Fe3C were less active.

Fe-based catalysts were acquired by one-step Fe-MIL-88B pyrolyzation and it showed high catalytic performance on hydrogenated conversion of carbon dioxide to valuable hydrocarbons. The iron compositions and catalytic performance of the catalysts were determined by pyrolysis temperatures according to XRD, SEM, TEM, N2-physisorption, Raman and evaluation results. Magnetite was obtained at 773 K while metallic iron was the main phase when the pyrolysis temperature increased to 973 K. Different catalytic performances over these catalysts were attributed to the transformation of iron species under the reaction conditions. Olefin-to-paraffin ratio (O/P) over pyrolyzed and K-doped catalysts was 1.3 and 5.5, respectively, and the two samples exhibited CO2 conversion with 46.0% and 43.1%, respectively. Higher catalytic performance was achieved when certain amount of Fe3O4 and χ-Fe5C2 existed in catalysts whereas metallic iron and/or θ-Fe3C had detrimental effects on lower conversion of CO2 and selectivity of valuable hydrocarbons.