Doped carbon black catalyst supports: II. Magnetic, Mössbauer, and catalytic studies of iron/carbon systems

Abstract In continuation of our earlier investigation of carbon-supported Fe catalysts, a systematic study of diamagnetic susceptibility and ESR spectroscopy was carried out on “as-received”, graphitized, and borondoped carbon blacks. This characterization showed the Fermi level ( E F ) of the graphitic carbon decreased with boron doping. These carbon supports were used for dispersing small Fe crystallites, which were further characterized by appropriate in situ magnetization measurements and Mossbauer Spectroscopy. Observations showed that all Fe C catalysts were superparamagnetic yielding particle diameters in the range of 3.5–5.5 nm. From the reaction rates obtained for CO hydrogenation over these catalysts, activation energies, product distributions, and turnover frequencies were computed. These results were compared with Fe Al 2 O 3 and Fe SiO 2 catalysts. The iron dispersed on boronated carbons showed a small increase in turnover frequency for CO hydrogenation as compared with Fe dispersed on undoped carbons. A seven-fold change in the E F level of the carbon supports produced only a twofold change in activity, and consequently a strong interaction between the iron and carbon could not be confirmed.