This work addresses the stability of different Ru-based dual function materials (DFM, x% Ru, 6.1% “Na₂O”/Al₂O₃) during cycles of CO₂ capture from simulated power plant effluent (320 °C; 7.5% CO₂, 15% steam, 4.5% O₂, balance N₂ (v/v)) and subsequent catalytic methanation. Aging studies are carried out to simulate natural gas combustion flue gas on DFM granules, tablets, and ring tablets prepared by sequentially impregnating Ru and Na₂O. Stability increases with Ru loading; however, 0.5% Ru DFMs demonstrate a small but steady loss of CH₄ produced per cycle consistent with deactivation of the Ru component likely due to exposure to high levels of O₂ and steam in the flue gas. CO chemisorption, in-situ FT-IR, and transient microreactor studies all verify that there is loss in Ru active surface area, possibly due to sintering, which consequently results in lower methanating ability.