Selective and Stable In-Promoted Fe Catalyst for Syngas Conversion to Light Olefins

A selective and stable alumina-supported In-promoted Fe catalyst (10 mol % In based on Fe) was discovered for converting syngas (2:1 H-2/CO ratio) to olefins with high selectivity (45% with CO2 included) and a remarkable stability (72 h run) at a CO conversion of 10% at 400 degrees C and 5 bar. The X-ray photoelectron spectroscopy results indicated that incorporating In into Fe catalysts changed the chemical bonding state of Fe and Fe/In composition near the surface layers, which affected the catalytic reactivity. Steady-state isotopic transient kinetic analysis showed that more stable CHx fragments are present on the catalyst surface when incorporating In into Fe, which can promote C-C coupling reaction toward olefins. Our study demonstrates that introducing In into Fe catalysts on Al2O3 support can lower CO activation abilities. It has more impacts on lowering hydrogenation activity, which permits more C-C couplings and like of "ene" hydrogenation. Moreover, weakening CO adsorption both in terms of sites and strength encouraged CO toward hydrocarbons rather than CO2.