Synergistic promotions between high purity H2 production and CO2 capture via sorption enhanced chemical looping reforming

Abstract

Hydrogen energy, a promising clean source, holds potential to combat global warming. To achieve efficient and low-carbon H₂ production, we proposed an isothermal sorption-enhanced chemical looping reforming (SE-CLR) process to realize the high-purity hydrogen production and in-situ CO₂ capture at mild temperatures (550–650 °C). For practical application, the process is characterized to use Fe-Ni double metal oxide particles as steam methane reforming oxygen carriers, and K₂CO₃-promoted Li₄SiO₄ particles as CO₂ sorbent. The oxygen transfer capacity of metal oxide matintained high at 57.4%, and the K-Li₄SiO₄ absorbents remained at 22.5% CO₂ absorption capacity over 200 isothermal absorption-regeneration cycles. Conducting a synergistic conversion mechanism within double metal oxides and absorbents, and adjusting the absorbent-to-metal oxide mass ratio to 7:4, enhanced hydrogen purity to 92% and CO₂ uptake to 95%. Furthermore, in-situ CO₂ removal in CLR processes achieved methane conversion and H₂ production rates equivalent to conventional CLR processes under the same reaction conditions, but at temperatures ∼60 °C lower. The effects of the reaction temperature, pressure, steam-to-methane and methane-to-solid ratios on SE-CLR performance were studied systematically. Finally, stable hydrogen production with a purity of 91%–89% and CO₂ uptake of 94%–91% were obtained over 25 CLR cycles, with minimal changes in mechanical strength of particles.