Bio-oil chemical looping reforming coupled with water splitting for hydrogen and syngas coproduction: Effect of supports on the performance of Ni-Fe bimetallic oxygen carriers

Highlights: • F/O of 0.3 at 900 °C is suitable for CLRWS using Aspen Plus simulation. • NiO in OCs enhanced bio-oil reforming but aggravated carbon deposition. • NFL is excellent for syngas production but cycle performance unstable. • NFZ has the highest R_OC and lowest carbon deposition but readily sintering. • NFC is a promising OC, maintained high hydrogen yield and purity. In this study, chemical looping reforming coupled with water splitting (CLRWS) process for coproduction of syngas and hydrogen using bio-oil model compound as fuel was investigated. The process simulation results indicated that the mass ratio of fuel to Fe₂O₃ (F/O) of 0.3 at 900 °C was suitable for syngas and hydrogen coproduction. Under these conditions, the CLRWS experiments were conducted in the fixed bed reactor using Ni-Fe bimetallic oxygen carriers (OCs). The Ni-Fe bimetallic oxygen carrier contained 5 wt% of NiO, 60 wt% of Fe₂O₃ and 35 wt% of support. Six metal oxides, Al₂O₃, CeO₂, La₂O₃, MgO, TiO₂ and ZrO₂, were used as supports, and corresponding OCs were termed as NFA, NFC, NFL, NFM, NFT and NFZ, respectively. The interaction between different components had significant influence on coproduction of syngas and hydrogen. The formation NiAl₂O₄, FeAl₂O₄, MgFe₂O₄, and Fe₂TiO₅ were unreadily reduced and unfavorable for the high purity hydrogen production in SR. The NFL, NFZ and NFC presented the better performance than the NFA, NFM and NFT. The catalytic reforming reactions were enhanced significantly by introducing NiO and the supports, while the presence of Ni readily produced higher carbon deposition, which could be alleviated by the addition of steam in FR. The hydrogen purity of all OCs increased to more than 95% in the SR with S/C = 1.4. The top two hydrogen purity in SR for NFZ and NFC were 99.73% and 99.66%, the corresponding hydrogen yield were 1.132 Nm³/kg and 1.165 Nm³/kg, respectively. The NFL exhibited excellent catalytic performance and benefited to produce syngas. The NFZ had the highest oxygen transfer capacity and the lowest carbon deposition. The cyclic stability of NFL and NFZ decreased with the increasing of number of cycles. The NFC is a promising OC in the CLRWS process with the presence of steam, maintained high hydrogen purity and good stability performance in the multiple cycle tests.