Catalytic Removal of Oxygen Impurities from Pressurized Oxy-Combustion Flue Gas for the Production of High-Purity Carbon Dioxide

Flue gas purification is important for pressurized oxy-combustion systems to produce pure carbon dioxide (CO₂) streams ready for storage or utilization. A catalytic approach to removing oxygen (O₂) impurities from pressurized oxy-combustion flue gas via reduction with methane (CH₄) was investigated in this work. Two types of catalysts were studied: palladium (Pd)-based catalysts supported on titania (TiO₂) prepared by incipient wetness impregnation and cobalt-manganese (CoMn) composite catalysts prepared by coprecipitation. The performance of the catalysts was evaluated in a high-pressure-high-temperature, fixed-bed reactor at a pressure of 15 bar and a gas hourly space velocity of 30 »000 h^-1(standard conditions), with a simulated feeding gas composed of 3 vol % O₂, 1.5 vol % CH₄, and CO₂as the balance gas. Among the Pd catalysts, 5% Pd/TiO₂achieved the maximum 86% O₂removal at ≥350 °C. The CoMn oxide catalysts displayed comparable or better activities for O₂reduction compared with the Pd catalysts. Among them, the Co₄₀Mn₁catalyst exhibited the best performance, able to reduce 99.9% of O₂impurities at ∼370 °C with negligible carbon monoxide (CO) formation (<10 ppmv). Both trivalent and divalent Co and Mn were detected on the catalyst surface, and the superior activity of Co₄₀Mn₁might be associated with the resultant disordered structure. The activity of the catalyst was not affected by the presence of a trace amount of nitric oxide (NO) gas contaminant. Results of this study provide the basis for scale-up studies in both the synthesis and performance of non-noble metal catalysts.