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Summary: In the chemical looping hydrogen generation process, CoFe2O4 is regarded as one of the most excellent candidates for oxygen carriers (OCs). In this paper, the synergistic effect of Cu and Ce added to CoFe2O4 was studied. The doping of Cu and Ce improved the reactivity of CoFe2O4 with methane, and also increased the hydrogen yield and purity. The results indicated that the introduction of Cu and Ce facilitated the deep reduction of CoFe2O4, which was ascribed to the enhanced migration capacity of lattice oxygen. In addition, the addition of Cu inhibited the decomposition of CH4 and alleviated carbon deposition. The Cu4Ce4‐CoFe had a suitable Cu/Ce mass ratio, which was more conducive to the formation of excellent synergistic effect to enhance hydrogen production and weaken carbon deposition. The Cu4Ce4‐CoFe exhibited outstanding H2 yield (15.42 mmol·g−1) and H2 purity (99.13%). In addition, the reactivity of OC decreased to some extent with the cyclic experiment when the Cu4Ce4‐CoFe was used, the H2 yield decreased from ∼15.21 to ∼10.86 mmol·g−1 over 10 experimental cycles. In conclusion, Cu and Ce co‐doping is an effective strategy to obtain OCs with preeminent hydrogen production performance and anti‐carbon deposition performance. [ABSTRACT FROM AUTHOR]

Summary: Chemical looping hydrogen production is a kind of hydrogen production technology with great potential. NiFe2O4 is one of the oxygen carriers with the best comprehensive hydrogen production performance, but the oxygen carrier still has the disadvantages of low hydrogen production and poor reaction stability. In this paper, a small amount of Ce was doped in the oxygen carrier to improve the hydrogen production efficiency. And the reaction stability of the oxygen carrier was improved by loading an inert carrier. The experimental results showed that the 6 wt% Ce‐NiFe2O4 oxygen carrier had the highest H2 yield, and the hydrogen yield per unit mass of oxygen carrier was increased from 194 to 367 mL/g. Thermodynamic simulation and characterization results showed that the doping of Ce could enhance the oxygen release capacity and hydrogen production capacity. In the cyclic experiment, due to the damage of the oxygen carrier spinel structure and the sintering of oxygen carrier particles, the reaction activity of the 6 wt% Ce‐NiFe2O4 oxygen carrier gradually reduced and the hydrogen production in the steam reactor decreased significantly after 15 cycles. After the loading of Al2O3 inert support on the 6 wt% Ce‐NiFe2O4 oxygen carrier, the hydrogen production was greatly improved and remained stable after 15 cycles. The modification of the oxygen carrier could not only increase the hydrogen production but also the economic efficiency for the reduced amount of Ce and Ni. [ABSTRACT FROM AUTHOR]

3% Fe/Al 2 O 3 and 3% Fe/Al 2 O 3 @SiO 2 were prepared to investigate the performance in simultaneous removal of NO x and SO 2 using vaporized H 2 O 2 . Certain paraments were changed to explore the activity of catalysts, including temperature, H 2 O 2 concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al 2 O 3 @SiO 2 . Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al 2 O 3 , 3% Fe/Al 2 O 3 @SiO 2 exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO 2 and 93.76% for NO x . Moreover, 3% Fe/Al 2 O 3 @SiO 2 kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO 2 , which could improve the activity of catalyst at high temperature and high SO 2 concentration. Besides, the mechanism of SO 2 molecules on simultaneous removal was investigated. On one hand, a part of H 2 O 2 was consumed by SO 2 molecules without catalyst, which resulted in the drop of NO x removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO 2 over the catalyst. On the other hand, the presence of SO 2 was beneficial for NO x removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO 2 by NaOH solution., (Copyright © 2021 Elsevier Ltd. All rights reserved.)