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Alkali Metal CO2 Sorbents and the Resulting Metal Carbonates: Potential for Process Intensification of Sorption-Enhanced Steam Reforming

Memon, Muhammad Zaki, Zhao, Xiao, Sikarwar, Vineet Singh, Vuppaladadiyam, Arun K., Milne, Steven J., Brown, Andy P., Li, Jinhui, Zhao, Ming
Environmental Science & Technology 2017 v.51 no.1 pp. 12-27
biomass, carbon dioxide, carbonates, catalysts, catalytic activity, ceramics, cost effectiveness, cracking, economic feasibility, energy, ethanol, feedstocks, flue gas, hydrogen, hydrogen production, methane, methodology, powders, power plants, sorbents, steam, temperature
Sorption-enhanced steam reforming (SESR) is an energy and cost efficient approach to produce hydrogen with high purity. SESR makes it economically feasible to use a wide range of feedstocks for hydrogen production such as methane, ethanol, and biomass. Selection of catalysts and sorbents plays a vital role in SESR. This article reviews the recent research aimed at process intensification by the integration of catalysis and chemisorption functions into a single material. Alkali metal ceramic powders, including Li₂ZrO₃, Li₄SiO₄ and Na₂ZrO₃ display characteristics suitable for capturing CO₂ at low concentrations (<15% CO₂) and high temperatures (>500 °C), and thus are applicable to precombustion technologies such as SESR, as well as postcombustion capture of CO₂ from flue gases. This paper reviews the progress made in improving the operational performance of alkali metal ceramics under conditions that simulate power plant and SESR operation, by adopting new methods of sorbent synthesis and doping with additional elements. The paper also discusses the role of carbonates formed after in situ CO₂ chemisorption during a steam reforming process in respect of catalysts for tar cracking.