High-efficiency catalytic reduction of residual oxygen for purification of carbon dioxide streams from high-pressure oxy-combustion systems

Abstract

Pressurized oxy-combustion is a promising technology for carbon capture, utilization, and storage. For the captured CO₂ to be used for enhanced oil recovery or stored in geological formations, flue gas impurities, including residual O₂ in the CO₂ stream, must be purified to meet the purity specifications. A catalytic approach to reducing residual O₂ with CH₄ was investigated in this study. Five CoMn- and Cu-based catalysts were synthesized or acquired, and a reverse-flow fixed-bed reactor was used to assess their performance for O₂ removal from a simulated oxy-combustion flue gas at 15 bar. The impacts of the operating parameters on O₂ removal, such as temperature, gas hourly space velocity, O₂/CH₄ ratio, and gas pressure, were investigated. Among the tested catalysts, the two CoMn catalysts were superior in both activity and selectivity, with the reaction lighting off at about 350 °C and achieving 99% O₂ removal at about 500 °C. The kinetics of the catalytic reaction is discussed, and the Mars–van Krevelen redox mechanism is deemed valid for describing the reaction pathway for the top-performing CoMn catalysts. The catalytic reaction was determined to be first order in CH₄ and zero order in O₂ under the test conditions.