Solid sorbents for in-situ CO2 removal during sorption-enhanced steam reforming process: A review

Integrating in-situ CO2 removal at high temperature by solid sorbents during sorption-enhanced steam reforming process for high-purity hydrogen production has been considered to change the normal equilibrium limits of shift reactions and increase hydrocarbon conversion as well as reduce CO2 emissions. However, a difficulty by integrating these reaction steps in a single and integrated process involves selecting suitable sorbents and reaction conditions under which all of the processes can be carried out. Due to the difficulty in application of solid sorbents in SERP, the improvement of their performance is crucial to make the process important for industrial applications. This study discussed the performances of CaO, MgO, hydrotalcite and Li2ZrO3 based sorbents during sorption-enhanced steam reforming for high-purity hydrogen production, while different methods for enhancing these sorbents activities were summarized. The factors of reaction conditions such as temperature, pressure, the amount of water vapor etc. and related reaction mechanisms using these solid sorbents are identified. CaO has shown its potentials with its lost cost and high capacities. Nevertheless, the deactivation of CaO during multi-cycles carbonation-regeneration is challenging for continuous long-term operating conditions for hydrogen production from catalytic steam reforming. The potential and development of the multifunctional sorbent-catalyst materials having a dual function of catalytic steam reforming and in-situ CO2 removal were discussed.