CO hydrogenation over well-dispersed carbon-supported iron catalysts

Abstract

It became apparent that carbon-supported iron systems were quite interesting and a broader base was required for comparison, so catalysts composed of iron dispersed on graphitized carbon, carbon blacks, and activated carbons were prepared. In contradiction to earlier studies of Fe/carbon CO hydrogenation catalysts, these carbon-supported iron samples were very active, and they typically had higher activities and olefin/paraffin ratios than unpromoted Fe/Al/sub 2/O/sub 3/ catalysts. In addition, an aqueous impregnation technique was developed which allowed the preparation of very highly dispersed iron on certain carbons. These iron/carbon catalysts could be placed in two general groups: one with high dispersion (HD) and one with low dispersion (LD). These reduced catalysts exhibited extremely interesting chemisorption behavior at 300 K - hydrogen chemisorption either did not occur or was very low while CO chemisorption always occurred, with very large CO uptakes existing in some cases indicating the presence of very small iron particles (i.e., high dispersions). In addition to these chemisorption properties, significant differences existed in catalytic behavior which could be correlated with the crystallite size of the iron. This note describes these variations in catalytic properties.