Potassium modified iron-based oxygen carrier boosted chemical looping hydrogen generation using biomass pyrolysis volatiles as feedstock

Chemical looping hydrogen generation (CLHG) using biomass pyrolysis volatiles matters (VMs) offers a promising hydrogen production method that utilizes highly reactive feedstocks and avoids ash-oxygen carrier separation. However, application is hindered by inefficient tar conversion and oxygen carrier (OC) deactivation from carbon deposition. This study examines potassium modification to enhance Fe-based OC performance in CLHG with VMs. The results show that the K-modified OCs significantly improve H 2 yield, with 10 wt % KNO 3 loading amount providing the most economical H 2 production. Potassium modification can promote steam cracking, increasing H 2 generation rate and reducing carbon deposition by ∼76 %, achieving over 99 % H 2 purity. Optimizing the oxygen-to-fuel ratio ( φ = 2) and raising temperature foster the active hydrogen-producing phase. After five redox cycles, K-modified OCs maintains over 94 % of its initial H 2 yield, demonstrating excellent redox reactivity, carbon deposition resistance, and cyclic stability for efficient biomass-based CLHG process.