The activity and selectivity of a 2

The activity and selectivity of a 2 wt% Ru supported on γ-Al2O3 egg-shell catalyst for CO methanationin CO2/H2 rich gases was investigated. A kinetic model based on a Langmuir-Hinshelwood approachfor both reactions was determined. The agreement with measurements in a fixed bed reactor is verysatisfactory. CO2 methanation is slow compared to CO methanation, at least at temperatures below 200 ◦C.CO2 is directly converted to methane; the indirect route via RWGS and CO methanation could be excludedby respective measurements and kinetic considerations. Pore diffusion may affect the CO conversionat high temperatures (>200 ◦C). The kinetic equations were applied to model an adiabatic fixed bedmethanation reactor suitable for a fuel cell for household appliances. The catalyst mass needed to reach aresidual CO content of 100 ppm for feed gas with 0.5% CO, 10% CO2, 10% H2O, and 79.5% H2 is about3 kg, which seems to a reasonable value. The H2 consumption is 20% higher compared to the ideal casewithout any conversion of CO2.