Catalytic Oxygen Reduction for Deep O₂Removal from CO₂Streams

Streams of CO₂from various capture processes may contain several impurities of which O₂is often overlooked as a problematic impurity. Because of its reactivity, the National Energy Technology Laboratory has recommended a stringent limit, less than 10 ppm, for the O₂level in treated CO₂products for safe transport, storage, and utilization. In this study, a variety of catalytic oxygen reduction approaches using commercial automotive exhaust emission catalysts are evaluated for O₂removal from CO₂streams using different reducing agents, including H₂, CO, CH₃OH, and CH₄. When the amount of reductant added into the feed is carefully controlled, H₂, CO, or CH₃OH can effectively remove O₂from 1.5% to below 10 ppm with a single-reactor design (>99.93% removal efficiency), while simultaneously meeting the impurity limits for other species. With CH₄as a reductant, it is challenging to simultaneously meet the the O₂and CO specifications in a single-reactor design because CH₄also reacts with CO₂to produce high levels of CO in the stream (at several hundred ppm). A dual-reactor design is developed to enable the use of CH₄, a readily available and low-cost reductant, for the purification of CO₂streams to meet the specifications for O₂and other impurities.