Hydrogenation of carbon monoxide over iron catalysts on different supports

Abstract

The catalytic and physical properties of a series of iron catalysts supported on Al 2O 3, MgO, TiO 2, NaY and NaZSM-5 were studied. The catalysts were characterized by hydrogen and carbon monoxide chemisorption and by X-ray diffraction measurements. Kinetic measurements were made in a high-pressure microreactor. Carbon deposition during carbon monoxide hydrogenation was studied gravimetrically under high-pressure conditions. The different characterization techniques gave relatively large differences in the apparent metal dispersions. The turnover frequencies (based on carbon monoxide chemisorption) increased in the order Fe/TiO 2<Fe/MgO<Fe/NaZSM-5<Fe/Al 2O 3<Fe+K/Al 2O 3<Fe/NaY for catalysts containing 8–12 wt.-% Fe. The observed catalytic activities were all within the same order of magnitude. The variations in selectivity could be interpreted in terms of the basicity of promoters and supports. The carbon formation on the catalysts during carbon monoxide hydrogenation was characterized by an initial period of very rapid carbon formation, followed by a period of significantly slower carbon formation. The carbon formation on Fe/TiO 2 and Fe/MgO was different from that observed on the other catalysts.