Chemical looping reforming of biomass based pyrolysis gas coupling with chemical looping hydrogen by using Fe/Ni/Al oxygen carriers derived from LDH precursors

Highlights: • Chemical looping coupling process were proposed to reform biomass based pyrolysis gas and achieve high purity hydrogen. • Reaction performance of Fe/Ni/Al mixed oxygen carriers derived from layered double hydroxide precursors was evaluated. • 98.26% CH₄ conversion, 71.92% CO₂ conversion and 96.56% H₂ purity were achieved. • High disperse Ni_0.6Fe_2.4Al_1.1O₄ was generated in the regeneration stage. -- Abstract: Chemical looping reforming (CLR) coupling with chemical looping hydrogen (CLH) was proposed to reform biomass based pyrolysis gas and achieve high purity H₂ by using Fe/Ni/Al oxygen carriers derived from layered double hydroxide (LDH) precursors. The crystal form, morphology and reactivity of oxygen carriers were characterized by various analysis methods. The chemical looping reaction process was investigated in a fixed bed reactor. The experimental results exhibited that Fe_0.99Ni_0.6Al_1.1O₄ high dispersed oxygen carrier was synthesized. Moderate lattice oxygen releasing rate 0.00175 wt%/s and escape ratio 95.14% were achieved by the mixed oxygen carrier with Fe/Ni ratio of 3/1. Ni had positive effect on lattice oxygen escape ratio of oxygen carrier while Fe contributed to improve the instantaneous lattice oxygen releasing rate. Furthermore, the CH₄/CO₂ in biomass based pyrolysis gas was eliminated via CLR process based on the metal catalytic effect of oxygen carrier. The highest CH₄ conversion 98.26% and CO₂ conversion 71.92% were obtained in CLR process accompanying with the reduction of Fe_0.99Ni_0.6Al_1.1O₄ to Fe/Ni alloy. Additionally, H₂ with 96.56% purity was achieved in CLH process with the conversion of Fe/Ni alloy to Fe₃O₄. The H₂ instantaneous generation rate increased sharply to the maximum value 34.70 ml/min and then declined gradually. Ni_0.6Fe_2.4Al_1.1O₄ new high dispersed compound was generated in the regeneration stage with similar structure to fresh sample and more active Fe species content. Though the particle size of oxygen carrier tended to decline after whole reaction process, the porous structure was still reserved.