Kinetics of CO2 methanation using a Fe-bearing blast furnace sludge as catalytic precursor

The catalytic activity of a blast furnace sludge (BFS) with important Fe content, was experimentally evaluated in the methanation of CO2. The effect of temperature (265-320 degrees C), total pressure (1-5 bar), partial pressures of H2 (12-30 kPa), CO2 (0.5-3.0 kPa) and H2/CO2 ratio (4-25) on CO2 conversion and selectivity towards CH4 and CO were studied. The experimental assays were carried out in a laboratory differential reactor. The favorable effect of temperature, total pressure and H2/CO2 ratio on methane formation was demonstrated. In addition, the catalyst exhibited a stable activity during prolonged reaction times, a valuable characteristic for its industrial application. The reaction mechanism of CO2 hydrogenation using this BFS-catalyst was studied under a strict kinetic regime. Different reaction paths were considered, from which kinetic expressions were derived using the Langmuir-Hinshelwood methodology and the Levenberg-Marquardt algorithm. The latter, for evaluation of the resulting kinetic/adsorption parameters. By applying the corrected Akaike information criterion (AICc), the rate controlling step was established. This corresponds to the hydrogenation of adsorbed CH, with surface CO as the main intermediary of methane formation. From the experimental data, an activation energy of 86.5 kJ/mol was calculated. This article can be considered as a first step for future processes of scaling and optimization of CO2 methanation using a waste from the steel production industry.

Automated summary

The catalytic activity of blast furnace sludge (BFS) in the methanation of CO2 was evaluated, and the effects of temperature, total pressure, partial pressures of H2 and CO2, and H2/CO2 ratio on CO2 conversion and selectivity were studied. The results showed that temperature, total pressure, and H2/CO2 ratio had a favorable effect on methane formation. The catalyst also exhibited stable activity and a potential for industrial application. The reaction mechanism and kinetic parameters of CO2 hydrogenation were investigated, and the rate controlling step and activation energy were determined.