Integrated two-stage catalytic–adsorptive system for efficient removal of O2, H2O, and tritium from molten salt reactor off-gas

This study describes a two-stage catalytic and adsorptive system for the integrated removal of oxygen (O2), water (H2O), and a tritium surrogate (H2) from a molten salt reactor (MSR) off-gas. The system utilizes a Cu-based catalyst in the initial stage to eliminate O2 and convert H2 to H2O, followed by a zeolite 13X adsorbent in the subsequent stage to adsorb H2O vapor. The performance of each component was optimized in a single-bed configuration. The Cu-based catalyst exhibited exceptional efficiencies for O2 removal and H₂ conversion, surpassing 99% at temperatures of ≥300 °C, with stable cycling performance at the optimal operating temperature of 350 °C. The zeolite 13X adsorbent displayed a high H2O vapor removal efficiency of >99% at 25 °C over a broad concentration range of 500–3000 ppm. The effectiveness of the complete two-stage system was confirmed using a mixed gas stream containing 500 ppm each of O2, H2O vapor, and H2. Operating sequentially, the catalytic stage at 350 °C and the adsorptive stage at 25 °C achieved an overall removal efficiency of >99% for all target species. These findings validate the two-stage strategy as a practical and highly efficient approach for comprehensive off-gas purification, thereby streamlining the system design for advanced MSRs.