Chemical looping steam reforming of bio-oil is novel conversion technology utilizing waste energy, which is an advantage to reduce cost and improve environmental. However, complex reaction process between oxygen carrier and bio-oil constrain its development. In this study, perovskite based La 0.8 M 0.2 Ni 0.8 Fe 0.2 O 3 (M = Ca, Ce and Zr) were investigated as an oxygen carrier for chemical looping steam reforming of bio-oil model reaction. The perovskites were prepared via sol-gel method and the effect of doping for reforming of acetic acid as bio-oil model compound is also investigated. Among all the perovskite tested, Ce doped La 0.8 Ce 0.2 Ni 0.8 Fe 0.2 O 3 oxygen carrier gave superior and stable catalytic performance for 1440 min at 600 °C and steam/carbon mole ratio (S/C = 2). The fresh and spent oxygen carriers were characterized using XRD , H 2 -TPR, CO 2 -TPD, TG-DTG, Dielectric constant , Raman, XPS and XANES . Doping with base metal generally, improved coke resistance ability of the perovskite. CO 2 -TPD and XPS analysis reveal that the highest carbon resistance for La 0.8 Ce 0.2 Ni 0.8 Fe 0.2 O 3 perovskite is due to enhanced stronger surface basicity and oxygen adsorption. From DFT simulation and Dielectric constant results, the better activity for La 0.8 Ce 0.2 Ni 0.8 Fe 0.2 O 3 is attributed to its adsorption ability of reactants, oxygen and electron transfer from sub-surface to surface of the perovskite.
Kun Zhao,Xiaojie Fang,Chaoxian Cui,Shunshun Kang,Anqing Zheng,Zengli Zhao
Chemical looping steam reforming of methane (CL-SRM) is a novel process for the co-production of syngas and hydrogen without an additional purification process. However, the high activity of oxygen carriers is always accompanied by severe carbon deposition via the catalytic cracking of methane, which can result in the rapid deactivation of oxygen carriers and the production of low purity hydrogen. Herein, a series of novel composite oxide carriers of CeO 2 /La 0.9 Sr 0.1 Fe 1−x Ni x O 3 with varying doping ratios of Ni are developed to achieve selective and stable production of syngas and H 2 . The redox performance of CeO 2 /La 0.9 Sr 0.1 Fe 1−x Ni x O 3 was evaluated in a fixed bed reactor coupling with various analytical methods. It is found that the Ni doping ratio of 0.2 can significantly enhance the performance and stability of CeO 2 /La 0.9 Sr 0.1 Fe 1−x Ni x O 3. It is speculated that the proper doping ratio of Ni can simultaneously improve the surface lattice oxygen vacancies and the lattice oxygen migration rate. The CH 4 reforming over CeO 2 /La 0.9 Sr 0.1 Fe 0.8 Ni 0.2 O 3 displays a very stable performance while avoiding obvious carbon deposition within 20 min, in which, the CH 4 conversion, H 2 selectivity , and CO selectivity achieve 85%, 96%, and 88%, respectively. The yield of H 2 (>95% purity) reaches 23 mL/min in the subsequent steam oxidation of reduced CeO 2 /La 0.9 Sr 0.1 Fe 0.8 Ni 0.2 O 3 . Its lattice oxygen can be completely recovered by the final air oxygenation. The CeO 2 /La 0.9 Sr 0.1 Fe 0.8 Ni 0.2 O 3 exhibits high reactivity and stability in 10 redox cycles at 850 °C. These results demonstrate that the doping of Ni affords an efficient manner to regulate the lattice oxygen migration rate of perovskite oxides to match the surface reaction rate, thereby avoiding the deep reduction of surface metal ions within perovskite oxides and resulting carbon depositions during CL-SRM.
Mingkai Liu,Zihan Wan,Yunlian Liu,Qian Jia,Ruqi Zhang,Yang Li,Ying Pan,Hongguang Jin
Hydrogen production is crucial for supporting the energy transition and achieving carbon neutrality goals. However, conventional natural gas steam reforming suffers from high temperatures, which lead to substantial exergy losses, promote carbon deposition, and compromise operational stability. Here, a mid-temperature (500–600 °C) chemical looping steam reforming (CLSR) process is proposed for efficient natural gas conversion. Fe Ni oxygen carrier particles were developed by varying Fe/Al precursors, calcination temperatures, and powder sizes to achieve modulated physico-chemical properties. Systematic evaluation of chemical reactivity and physical indicators identified nm-Fe 2 O 3 -γ-Al 2 O 3 calcined at 1200 °C as the optimal formulation, combining high reactivity with a mechanical strength of 55.3 N. Reaction behavior was further investigated in a bench-scale packed-bed reactor with 100 g oxygen carrier loading. At 600 °C and a steam-to‑carbon ratio of 1.5, the optimized process achieved over 85 % natural gas conversion and nearly 100 % ethane conversion, yielding a hydrogen production of 25 mL g OC −1 and an H 2 /CO ratio of 1.8. In addition, long-term stability tests confirmed that the oxygen carriers retained their oxygen transfer capacity and microstructure after 1000 isothermal redox cycles, while cold attrition tests showed a mass loss of only 0.73 % over 2 h. Furthermore, in-situ DRIFTs and XRD provided clear mechanistic insights into the CLSR process over Fe Ni oxygen carriers, confirming the reaction pathway of natural gas activation and hydrogen production. Collectively, these findings highlight the promising performance of CLSR as an efficient route for low-carbon hydrogen production from natural gas.`.
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