Development of Highly Selective Support for CO Hydrogenation to Light Olefins with Partially Passivated Iron Catalysts

Abstract

AbstractTo rule out disturbances from water‐soluble efficient promoters (e. g., K2O or combination of S/Na), a simplified iron/support catalyst system was employed to investigate novel supports for the catalytic conversion of syngas (CO+H2) to light olefins (FTO). A series of supports with nominal compositions of ZnAl2O4 ⋅ xAl2O3 (x=1, 2, 3) were prepared by coprecipitation and subsequent high temperature calcination at 1200 °C for 24 h to generate partially passivated ZnAl2O4 and Al2O3 phases, through which each formed component of a catalyst may minimize interactions among them and exhibit unique activity. Iron catalysts were prepared by incipient wetness of iron salts over these supports. At a total pressure of ca. 20 bar and a CO conversion of 35 %, a catalyst with a nominal composition of 15 %Fe/85 %(ZnAl2O4 ⋅ 3Al2O3) exhibits a surprising C2=‐C4= hydrocarbon distribution of 58 %, which reaches a huge increase by almost 100 % in comparison with iron catalysts over regular supports (e. g., carbon, gamma‐Al2O3, etc.). This catalyst demonstrates the 1200 °C passivated ZnAl2O4 ⋅ 3Al2O3 as probably the most selective support material for iron‐based FTO catalysts. At CO conversion of 35 %, the contents of ethylene in C2, propylene in C3, and butylene in C4 products achieve extraordinary values of 82 %, 92 %, and 91 %, respectively.