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

To 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+H-2) to light olefins (FTO). A series of supports with nominal compositions of ZnAl2O4 . xAl(2)O(3) (x=1, 2, 3) were prepared by coprecipitation and subsequent high temperature calcination at 1200 degrees 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 . 3Al(2)O(3)) exhibits a surprising C-2(=)-C-4(=) 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 degrees C passivated ZnAl2O4 . 3Al(2)O(3) as probably the most selective support material for iron-based FTO catalysts. At CO conversion of 35 %, the contents of ethylene in C-2, propylene in C-3, and butylene in C-4 products achieve extraordinary values of 82 %, 92 %, and 91 %, respectively.