Catalytic conversion of syngas to olefins over Mn–Fe catalysts

A series of MnO2–Fe2O3 with various contents of Mn (0–40% atomic ratio) was synthesized by the co-precipitation method. XRD patterns indicate that the sharp and intense peaks are related to the excellent crystal quality of α-Fe2O3 nanostructures. HR-TEM images showed that α-Fe2O3 and MnO2, were partly in close contact and the lattice fringes exhibit the typical distances, i.e., α-Fe2O3 (104) (2.7 Å) and MnO2 (310) (3.1 Å). X-ray photoelectron spectroscopy (XPS) results of the Fe 2p core-level binding energy spectrum of the α-Fe2O3 and Mn 2p, indicated the presence of Fe3+ and Mn4+. The direct synthesis of olefins from syngas was carried out over the MnO2–Fe2O3 catalysts under pressurized fixed-bed continuous flow conditions. The results showed that Mn–Fe catalyst had high catalytic activity and high olefins selectivity without the addition of any promoters at low pressure. It was found that the catalyst containing 20 at% Mn–Fe was an optimal catalyst for the conversion of synthesis gas to hydrocarbons especially light olefins. The maximum CO conversion rate was 15%, and the yield of olefins (totally about 23.77%) with a predominance of CH4 (12.24%), and C2H6 (2.80%) components. Mn–Fe catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to olefins.