MnOx promotional effects on olefins synthesis directly from syngas over bimetallic Fe‐MnOx/SiO2 catalysts

The direct synthesis of lower olefins via the Fischer‐Tropsch reaction (FTO) has been performed over a series of Fe‐MnO x /SiO 2 catalysts. The addition of MnO x could improve the dispersion of iron species, and promote the reduction of iron oxide during the activation and subsequent carburization. Moreover, the results of characterization demonstrated that MnO x could enhance the surface basicity of the catalysts due to electronic effects and promote the formation of iron carbides. For the first time, the intrinsic power‐law kinetics for FTO was obtained for both Fe 20 /SiO 2 and Fe 20 ‐Mn 1 /SiO 2 catalysts. Kinetic parameters and structure characterizations indicated that MnO x could facilitate the CO dissociation on the catalyst surface, thus enhancing the adsorption strength and capacity of surface carbonaceous intermediates. The weak hydrogenation of carbonaceous species would boost the selectivities toward lower olefins. Finally, a plausible mechanism for FTO, involving the promotional effects of MnO x on Fe, has been proposed. © 2017 American Institute of Chemical Engineers AIChE J , 63: 4451–4464, 2017