Fischer-Trospch to olefins over hydrophobic FeMnOx@SiO2 catalysts: The effect of SiO2 shell content

Abstract

Selective conversion of syngas to olefins has aroused extensive attention while some challenges still existed such as high CO2 selectivity. Herein, a series of hydrophobic FeMnOx@SiO2-y-(CH3)3 (y represents SiO2 weight percent of the catalyst) catalysts with various SiO2 shell content were synthesized for Fischer-Tropsch to olefins (FTO). During the activation process, high hydrophobic SiO2-coating content catalysts suppressed the reduction/carburization of iron species to iron carbide. During FTO reaction, iron carbide of low hydrophobic SiO2-coating content catalysts was re-oxidized while it was stabilized for high hydrophobic SiO2-coating content catalysts. The trade-off among CO2, CH4 selectivity and SiO2-coating content was reflected as an increasing trend relationship, while olefins selectivity exhibited a decreasing trend. Additionally, a desirable hydrophobic SiO2-coating (8.2 wt%) catalyst apparently suppressed CO2 formation (4.7 C%) with high olefins selectivity (54.6 C%) at CO conversion of 50.7%. This study provides an efficient approach to inhibit CO2 formation of Fe-based FTO catalyst.