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 (O-2) 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 % O-2, 1.5 vol % CH4, and CO2 as the balance gas. Among the Pd catalysts, 5% Pd/TiO2 achieved the maximum 86% O-2 removal at >= 350 degrees C. The CoMn oxide catalysts displayed comparable or better activities for O-2 reduction compared with the Pd catalysts. Among them, the Co40Mn1 catalyst exhibited the best performance, able to reduce 99.9% of O-2 impurities at similar to 370 degrees 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 Co40Mn1 might 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.