Regulating iron species compositions by Fe-Al interaction in CO2 hydrogenation

Abstract

Different iron species exhibit distinct activity and selectivity in CO2 hydrogenation reaction. Herein, by controlling calcination temperature, Fe-Al interaction in Na promoted Fe-Al catalysts has been regulated, which further leads to various compositions of iron oxide (FeOx) and iron carbides (Fe7C3 and Fe5C2) after CO activation and CO2 hydrogenation reaction. The phase compositions and structures of Fe-Al catalysts are carefully distinguished by multiple characterizations, including XRD, XPS, MES and TEM, and the reactivity of different phases is studied with the combination of experiments (kinetics, TP and in situ DRIFTS) and Density Functional Theory (DFT) calculations. Our FeAl350 with the highest FeCx content shows the highest CO2 conversion of 48.2% and the lowest CO selectivity of 10.1%, and FeAl900 with the highest Fe5C2 / FeCx ratio presents the highest C5+ selectivity of 44.6%. Finally, a correlation between different compositions of iron species with the activity and selectivity of Fe-based for CO2 hydrogenation to olefins was established.