Syngas to olefins with low CO2 formation by tuning the structure of FeCx-MgO-Al2O3 catalysts

• A semi-quantitation method was applied for the measurement of the competition of CO reactivity against H 2 . • Compromise of chain growth ability (α) and O/P maximizes lower olefin selectivity. • CO 2 emission was reduced by mediating the primary and secondary CO 2 formation paths. Selectivity to olefins and CO 2 is a pivotal factor reflecting economic and environmental efficiency of the syngas to olefins process (STO). Herein we demonstrate the intrinsic nature of the catalyst supports in STO. FeMgAl catalysts with controlled Mg/Al ratio derived from layered double hydroxides (LDHs) were prepared by a co-precipitation method. A series of in/ex situ spectroscopy (FTIR, AP-XPS, TP, PE and MES) were applied to reveal Mg/Al ratio affecting the adsorption/reactivity of CO and H 2 , the proportion of iron carbides (FeC x ) and iron oxides (FeO x ) was relating to the selectivity to lower olefins and CO 2 . The MgAl oxide supported Fe catalysts can balance (i) carbon chain growth probability vs. O/P and (ii) primary/secondary CO 2 formation paths, to suppress the selectivity of CO 2 to 28.2% with a C 2 -C 4 olefin selectivity of 56.2%.