▎ 摘　　要

One-step conversion of syngas (a mixture of CO and H-2) to C-2-C-4 light olefins (FTO) has attracted enormous attention in recent years because of the great improvement in process simplicity. However, on the documented FTO catalysts, the carbon efficiency is quite low (CO2 selectivity as high as similar to 50%) and hence the green-house gas emission is high. Herein, we report about the design of novel Mg and K dual-decorated iron catalysts supported on reduced graphene oxide (rGO) to address this issue. We identified that on a dual-decorated FeMgK2/rGO catalyst with the optimized amounts of Mg and K, not only the selectivity to light olefins amounted to 65.0%, but also the selectivity to CO2 was appreciably cut down to 40.8%. On the basis of systematic characterizations, we propose that the suppression of the formation of magnetite during FTO because of Mg decoration effectively inhibited the water-gas shift (WGS) reaction, one of the main reaction pathways for CO2 generation. Furthermore, successive decoration with only 0.50-2.0 wt% of K drastically boosted the iron time yield to hydrocarbons (FTY) to 1060-1706 mol gFe(-1) s(-1) and the iron time yield to light olefins (FTYole) to 521-1003 mu mol gFe(-1) s(-1). The new strategy of alkaline-earth metal-alkali metal dual decoration for the design of the iron-based catalysts may propel the development of a practical FTO process featuring high productivity and low CO2 emission. (C) 2016 Elsevier B.V. All rights reserved.