Highly dispersed nickel catalyst promoted by precious metals for CO selective methanation

For CO selective methanation, highly dispersed Ni-MgO/γ-Al₂O₃ catalysts have been prepared by the deposition-precipitation method. To enhance their low-temperature activity and selectivity to CO, four precious metals (Ru, Rh, Pt and Ir) to be impregnated onto the Ni-MgO/γ-Al₂O₃ catalysts have been chosen based on their physicochemical properties, e.g. H₂-spillover and CO/CO₂ affinities. Each precious metal (1 wt. %) has been added by the incipient wetness method and the catalytic performance tests have been carried out in a micro fixed-bed reactor. The gas hourly space velocity is 2400/h and the feed gas consists of 1 vol. % CO, 20 vol. % CO₂, 57 vol. % H₂, 15 vol. % steam and N₂ balance. All the prepared catalysts have been characterized by BET, XRD, TPR, H₂/CO-chemisorption and CO/CO₂-TPD so the relationships between the catalytic performance and the promotion effects by the noble metal addition have been investigated. The experimental data reveals that the Ir-doped Ni catalyst shows the best performance (CO concentration < 10 ppm within 190-230 °C) due to enhanced reducibility and strong CO affinity.