Reverse Chemical Looping Hydrogen Production from Pine Biomass with Ca–Fe–Ni Composite Oxygen Carriers

Reverse chemical looping pyrolysis (RCLPy) utilizes a reduced oxygen carrier to extract oxygen from the biomass feedstock during the pyrolysis stage and transfer it for the subsequent gasification stage. This decoupled mechanism enables efficient in situ utilization of oxygen and hydrogen inherent in the biomass to produce a hydrogen-rich syngas. In this work, Ca–Fe–Ni composite oxygen carriers for RCLPy were synthesized and their impact on the hydrogen production was investigated and optimized. The results demonstrate that the reduced Ca–Fe–Ni oxygen carrier exhibited both excellent deoxygenation and catalytic cracking capability, significantly promoting the generation of hydrogen and CO. Specifically, the reduced CaFeNi15 oxygen carrier decreases the CO2 content in the pyrolysis gas from 40.4 vol.% without an oxygen carrier to 6.89 vol.% and with a hydrogen yield of 280.2 mL⸱g−1 biomass and has a total hydrogen production of 318 mL⸱g−1 biomass during the whole pyrolysis–gasification process. These findings underscore the advantages of the RCLPy process in utilizing inherent biomass hydrogen for high-purity syngas production. Future efforts should focus on developing oxygen carriers with enhanced long-term cyclic stability.