ENERGY & FUELS
·
2020
·
IF 3.421
Shiwei Ma,Shiyi Chen,Huijun Ge,Tao Song,Ping Lu,Wenguo Xiang
CeO2 is a typical fluorite oxide with desirable lattice oxygen conductivity and can be applied as an active support for the Fe-based oxygen carrier in chemical looping hydrogen generation (CLHG). However, Fe2O3/CeO2 always suffers from low thermal stability and sintering. Doping foreign cations could be a proper way to improve its reactivity and cyclic stability. In this work, Zr4+ and Sm3+, with a smaller ionic radius and lower valence than Ce4+, respectively, were doped into Fe2O3/CeO2 using the co-precipitation method, and the doping effects on the reactivity and redox stability of Fe2O3/CeO2 in CLHG were investigated. Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 provided the best redox reactivity, and the purity of generated hydrogen for all oxygen carriers reached nearly 100% (the detection limit of CO/CO2 was 0.01% in volume). The reactivity followed the sequence Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 > Fe2O3/Ce0.8Sm0.2O1.9 > Fe2O3/Ce0.75Zr0.25O2 > Fe2O3/CeO2. However, the concentration of oxygen vacancy was ranked as Fe2O3/Ce0.8Sm0.2O1.9 > Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 > Fe2O3/Ce0.75Zr0.25O2 > Fe2O3/CeO2. The Zr doping boosted the reactivity of Fe2O3/CeO2 mainly by enhancing its sintering resistance, whereas the Sm doping achieved it mainly by promoting the oxygen conductivity, whose ability to improve the thermal stability of Fe2O3/CeO2 was rather limited. Both Zr and Sm doping could suppress the outward migration of Fe cations in the particles, resulting in higher sintering resistance. Furthermore, Zr and Sm could dissolve into CeO2 for prepared Fe2O3/Ce0.6Sm0.15Zr0.25O1.925; however, the bleeding out of both dopants was observed with Sm0.5Zr0.5O1.75 formation, which could be detrimental to the redox stability of the oxygen carrier.
研究领域:
材料科学
·
能源工程
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Yusan Turap,Zhe Zhang,Yongkang Wang,Yidi Wang,Zhentong Wang,Wei Wang
Chemical looping hydrogen production process is a promising technology for producing low-carbon hydrogen from various fossil and biogenic energy sources. However, the typical contaminant in feedstock, hydrogen sulfide, has a potential influence on the process. Herein, this study investigated the influence of hydrogen sulfide on the chemical looping hydrogen production process. Results show that the presence of hydrogen sulfide in the fuel reduces the reaction performance of the oxygen carrier because sulfur is deposited in the oxygen carrier during the reduction stage to produce iron sulfide species (FeS 2 , Fe 7 S 8 and FeS). Then the iron sulfide is converted to hydrogen sulfide and sulfur dioxide during the hydrogen production and air oxidation stage, respectively. H 2 production temperature is an important factor in controlling the production of hydrogen sulfide, which will not be produced at temperature below 710 °C. In addition, the air oxidation regeneration step ensures that sulfur does not accumulate in the oxygen carrier, thus improving the cycle stability of the oxygen carrier.
研究领域:
能源科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2020
·
IF 10.652
Dewang Zeng,Fengwen Kang,Yu Qiu,Dongxu Cui,Min Li,Li Ma,Shuai Zhang,Rui Xiao
Supporting materials are often employed to enhance the stability of iron oxides oxygen carriers, but the reactivity is compromised for the dilution of the active phase. Here, we report several iron oxides supported by ionic conducting gadolinium-doped cerium oxides (GDC) for efficient chemical looping hydrogen production. The results show that GDC support can simultaneously improve redox stability and activity. Specifically, the produced Fe 2 O 3 /Gd 0.3 Ce 0.7 O 3−δ exhibits a high hydrogen production rate of ~0.71 mmol·g −1 ·min −1 and hydrogen yield of ~10 mmol·g −1 with negligible decay through 20 redox cycle. When using methane as the reducing agent, Fe 2 O 3 /Gd 0.3 Ce 0.7 O 3−δ shows high methane conversion of 75.67% and much lower carbon deposition than Fe 2 O 3 . The high performance is attributed to the improved oxide ion-conductivity through the oxygen carrier, which is further verified as the ability of the GDC support to accelerate the oxygen diffusion in the bulk. The explored support effects in this work can be extended to design oxygen carrier materials with both high activity and stability.
研究领域:
材料科学
·
能源化学
·
催化化学
·
无机化学
·
清洁能源技术
✓ 已验证
DOI
高影响因子
RENEWABLE ENERGY
·
2024
·
IF 9
Zhentong Wang,Zhe Zhang,Huan Li,Jianguo Liu
Biomass-derived gas chemical looping hydrogen production (CLHP) highlights its potential to produce high-purity hydrogen with recycling waste bioenergy. Investigations on the kinetics characteristics of stepwise reduction and steam/air oxidation are conducted on a thermogravimetric analyzer (TGA) with a bubbler. The research decouples Fe 2 O 3 -Fe 3 O 4 , Fe 3 O 4 -FeO, and FeO-Fe reduction stages by adjusting the partial pressures of CO/CO 2 . Kinetic equations of stepwise reduction correlating to the reaction temperature and gas concentration are established, with activation energies for the three stages of 9.99 kJ/mol, 82.10 kJ/mol, and 149.32 kJ/mol, respectively. Evolutionary calculations of kinetic models confirms that the Fe 2 O 3 reduction follows a topological chemical reaction pathway. The gas-solid dynamic response characteristics during the reduction process can be qualitatively and quantitatively analyzed, showing regions of Fe, FeO-Fe mixed zone, FeO, Fe 3 O 4 -FeO mixed zone, Fe 3 O 4 , Fe 2 O 3 -Fe 3 O 4 mixed zone, and Fe 2 O 3 distributed alternately along the bed axis. Increasing the oxidation temperature significantly enhance the reaction kinetics of hydrogen production more than reducing the reduction temperature during the steam oxidation process. Above 800 °C, the reaction kinetics of the air combustion stage (Fe 3 O 4 -Fe 2 O 3 ) is not affected by raising temperatures. Overall, this study linked the kinetic mechanism and gas-solid reaction characteristics of reactor beds.
研究领域:
能源科学
·
化学工程
✓ 已验证
DOI
高影响因子
ENERGY & FUELS
·
2015
·
IF 2.79
Shangzhe Sun,Ming Zhao,Liang Cai,Shuai Zhang,Dewang Zeng,Rui Xiao
The iron-based oxygen carrier with high oxygen transfer capacity has always been the key point in the chemical looping hydrogen generation (CLHG) process. In this study, CeO2-modified iron-based oxygen carriers with the porous reticular structure were prepared by the sol–gel method. Samples were tested in a thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor, respectively, to evaluate their capacities of hydrogen production and the resistance to carbon deposition or Fe3C formation. The effects of preparation conditions (CeO2 loading and [C6H8O7·H2O]/[PEG400] molar ratio) and experimental conditions (reducing atmosphere and temperature) on the physicochemical properties of CeO2-modified iron-based oxygen carriers were investigated. The initial screening test in TGA was done to select the samples with excellent reducibility and strong resistance to carbon deposition or Fe3C formation. Subsequent tests in the fixed-bed reactor were conducted to evaluate the redox characteristics and cyclic performance of the selected CeO2-modified samples. The results confirmed that iron-based oxygen carriers modified by CeO2 could effectively inhibit carbon deposition or Fe3C formation and the oxygen carrier prepared under the preparation conditions of Fe2O3/CeO2/Al2O3 = 65/5/30 and C6H8O7·H2O/PEG400 = 3 stood out from all the candidates by virtue of its high hydrogen production efficiency and the excellent recycle ability in the CLHG process. The oxygen carriers at the optimal reducing atmosphere (CO/H2/N2 = 40/30/30 and the steam oxidation reaction at 900 °C) showed the best performance with the highest hydrogen yield.
研究领域:
能源材料
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Liang Chen,Dongmei Luo,Zhenghao Wang,Kejing Wu,Lei Song,Hongjiao Li,Shan Zhong,Siyang Tang,Bin Liang
Chemical looping hydrogen generation (CLHG) offers a promising solution for producing H 2 from industrial off-gas, such as blast furnace gas. However, increasing H 2 production capacity of the oxygen carrier (OC) at moderate temperature remains a significant challenge. In this study, a novel Cu-Fe-based OC is tailored for moderate-temperature CLHG from blast furnace gas. The results demonstrates that the tailored OC exhibits a superior H 2 production capacity of 12.99 mmol·g −1 at 550 °C, which is 6.5 times higher than that of Fe 2 O 3 at the same temperature. The addition of Cu leads to the formation of oxygen defects, which facilitate the migration of lattice oxygen, thereby the activity of the OC is enhanced. Furthermore, cyclical experiments demonstrates that O 2 -assisted regeneration strategy can effectively suppress the segregation of Cu during the cycling process, and the tailored OC shows good stability during 10 redox cycles. No additional separation process was required and the purity of the hydrogen was higher than 99%. The findings here open a new avenue for efficient CLHG from industrial off-gas at moderate operation temperature.
研究领域:
能源化学
·
材料科学
·
化学工程
·
工业气体利用
·
氢能技术
✓ 已验证
DOI
高影响因子
ENERGY & FUELS
·
2017
·
IF 3.091
Shiwei Ma,Shiyi Chen,Ahsanullah Soomro,Wenguo Xiang
Fe2O3 is an excellent active metal oxide for chemical looping hydrogen generation (CLHG) with high conversion of CO to CO2 in the reduction stage, and high H2 mole fractions in the subsequent steam oxidation stage, especially for its low cost and abundance in nature. However, supports are generally used to improve its reactivity and stability and to eliminate its carbon deposition. In this paper, Fe-based oxygen carriers are prepared by a coprecipitation method with three supports, i.e., CeO2, ZrO2, and Al2O3. The reactivity, carbon deposition, redox stability, and sintering characteristics of the oxygen carriers are analyzed to investigate the effects of supports as well as the fundamental mechanism. The results show that the properties of the oxygen carriers highly rely on the support and its interaction with iron oxide. The oxygen carrier supported on Al2O3 exhibits poor reactivity and stability, and the oxygen carrier supported on ZrO2 leads to much carbon deposition, decreasing H2 purity, despite its high reactivity and stability. Nevertheless, the oxygen carrier supported on CeO2 demonstrates good reactivity and stability with no carbon deposition observed, and the reducible support CeO2 counteracts the negative effect originating from sintering and guarantees the reactivity and stability of Fe2O3/CeO2 due to its oxygen mobility property and the oxygen mobility enhancement originating from the formation of Fe–Ce solid solution and perovskite-type CeFeO3. Overall, the reducible CeO2 is a potential support to improve the redox characteristics of iron oxygen carrier in CLHG, and the Fe2O3/CeO2 exhibits the highest reactivity at 850 °C. In addition, all three oxygen carriers are characterized by scanning electron microscopy images, energy dispersive X-ray spectrometer analysis, and X-ray diffraction patterns before and after the redox cycles.
研究领域:
能源技术
·
材料科学
·
化学工程
·
环境科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）