Catalysis of the graphite-CO 2 reaction by iron from in-situ reduction of wüstite over the range 870-1100°C

Abstract

Experimental results are reported on the catalytic enhancement of the Boudouard reaction by iron produced in situ from wüstite in the temperature range 870-1100°C. Experiments were carried out under a carbon dioxide atmosphere and the isothermal weight loss of the samples was determined as a function of time. The experimental data were interpreted by recourse to a grain model with the incorporation of Roberts and Satterfield's effectiveness factor. Single porous disks made of carbon (graphite)-wüstite mixtures were employed in a thermogravimetric arrangement. The effects of temperature, reactant gas flow rate and fraction of wüstite in the pellet on the rate constant for the chemical reaction, which is described according to Langmuir-Hinshelwood kinetics, were determined. It was found that iron freshly reduced from wüstite acted as a fairly strong catalyst for the solution loss reaction, especially at lower temperatures. The catalytic effect of iron was observed to depend markedly on its history and the method of sample preparation. The presence of iron as a catalyst reduces the apparent activation energy to 24.0-34.0 kcal/mole, by comparison with 82.0 kcal/mole for the uncatalysed Boudouard reaction.