Performance of Na-Ru/Al₂O₃ dual function material for integrated CO₂ capture and methanation with the presence of coal ashes

Integrated Capture and Methanation of CO2 (ICCM) with H-2 produced from renewable energy is a novel Powerto-Gas technology. The combination of ICCM with CO2 point source, such as coal-fired power plant, is anticipated, which greatly motivates the investigations into the influences of coal ash on the key performance of dual function material (DFM) used in ICCM process. Via the experimental study on the coal ash impacts, this work explored the adaptability of DFM and ICCM to coal-fired power plant. Na-Ru/Al2O3 DFM and two ashes collected from the electrical precipitators of supercritical coal-fired power plants were used for experiments. It showed that fly ashes contaminated CO2 adsorbents and active sites of DFMs, and caused successive drops in carbonates conversion and CH4 selectivity upon cyclic ICCM reactions. The CO2-TPD and H-2-TPSR tests revealed that the declined supply capability of hydrogen atoms by Ru sites, and the increased rate gap between CO formation and the following CO hydrogenation were responsible for the declined methanation ability of ash-contaminated DFMs. The roles of SiO2 and Fe2O3 phases in ashes were identified, indicating that SiO2 reacted with adsorbent components and masked Ru sites, and then induced DFM deactivation by affecting the transport processes of key reactants; Fe2O3 successively invaded both Ru sites and Na2CO3/gamma-Al2O3 interface, leading to successive losses in methanation ability and CO2 desorption capacity with cyclic ICCM reactions.