107 results
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2. Mn doped CoFe layered double hydroxides lead to d-d orbital repulsion toward advanced electrocatalysts for oxygen evolution reaction.
- Author
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Yang, Yibin, Gao, Di, Ou, Yingqing, Yang, Yang, Xiao, Peng, and Zhang, Yunhuai
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OXYGEN evolution reactions , *LAYERED double hydroxides , *HYDROGEN evolution reactions , *ELECTROCATALYSTS , *CARBON dioxide , *CARBON paper - Abstract
Currently, developing highly active and low-cost electrocatalytic materials for oxygen evolution reaction (OER) is an enormously grand challenge. Herein, we developed a novel and highly active Mn doped Co 2 Fe layer double hydroxide (LDH) electrocatalyst for OER. We discovered that these electrocatalytic materials can be directly grown on carbon papers to construct high-specific-surface-area electrode, which shows the lowest overpotential of 266 mV at 10 mA cm−2. Furthermore, after introducing Mn element, DFT + U calculation found that the ∗OOH of Fe-site on Co 2 Fe 0.67 Mn 0.33 LDH could draw more electrons than Co 2 Fe LDH due to the electronegativity differences between Fe-site on Co 2 Fe 0.67 Mn 0.33 LDH and Fe-site on Co 2 Fe LDH, which is reason that the energy level of Fe 3d (e g) was obviously downshifted by d-d repulsion of Mn 3d and Fe 3d in the neighboring sites of Co 2 Fe 0.67 Mn 0.33 LDH after doped Mn element, which leads to reduce charge-transfer energy from O 2p to Fe 3d (e g) to promote oxygen evolution processes for OER. Meanwhile, the band gap is also decreased after doped Mn element in Co 2 Fe LDH due to the downshifted e g orbital energy of Fe 3d. This study gives a general avenue to design and developing efficiently active LDH electrocatalysts for OER in the future. • Both bimetallic CoFe LDH and Mn doped CoFe LDHs directly grown on carbon paper are successfully synthesized. • The Co 2 Fe 0.67 Mn 0.33 LDH@NFs exhibits a small overpotential of 236 mV at 10 mA cm−1 for OER. • DFT + U studies reveal that the observed superb OER activity could be attributed to d-d repulsion of Mn 3d and Fe 3d. [ABSTRACT FROM AUTHOR]
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- 2024
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3. Modulating composition and electronic structure enhance the catalytic performance of Co2MO4 (M=Fe, Ni, Cu) for NaBH4 hydrolysis.
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Wu, Longxiang, Yang, Mao, Liu, Yonghui, Wu, Yucheng, Huang, Duohui, Juxiang Shao, and Wang, Xiaolian
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ELECTRONIC structure , *CATALYTIC hydrolysis , *HYDROLYSIS , *VALENCE bands , *DENSITY functional theory , *CARBON dioxide - Abstract
The synergistic effect between metals is of great significance for improving the performance of materials, but the mechanism of synergistic catalytic of bimetallic has rarely been reported in the hydrolysis of sodium borohydride (NaBH 4 , SB). In this paper, a flower shaped Co 2 FeO 4 catalyst with high catalytic performance was selected from a series of Co x M 3-x O 4 (M = Fe, Ni, Cu) catalysts by controlling the composition. Based on the results of XPS characterization and density functional theory (DFT) calculation, the influence of component control on catalytic performance was discussed and explained from the perspective of electronic structure, and the "valence band center" and "D-band center" descriptors were introduced into the SB hydrolysis reaction. The simulation analysis results showed that the synergistic effect between Co–Fe elements resulted in the smallest center shift of the D band, the smallest binding energy of the hydrolysis reaction, and the best promoting effect on the electronic structure, manifested as the best catalytic performance. The calculation results were consistent with the XPS characterization results and the experimental results of hydrolysis performance testing, revealing the principle of bimetallic synergistic effect on catalytic performance. The synergistic effect between metals is of great significance for improving the performance of materials, but the mechanism of synergistic catalytic of bimetallic has rarely been reported in the hydrolysis of sodium borohydride (NaBH 4 , SB). In this paper, a flower shaped Co 2 FeO 4 catalyst with high catalytic performance was selected from a series of Co x M 3-x O 4 (M = Fe, Ni, Cu) catalysts by controlling the composition. Based on the results of XPS characterization and density functional theory (DFT) calculation, the influence of component control on catalytic performance was discussed and explained from the perspective of electronic structure, and the "valence band center" and "D-band center" descriptors were introduced into the SB hydrolysis reaction. The simulation analysis results showed that the synergistic effect between Co–Fe elements resulted in the smallest center shift of the D band, the smallest binding energy of the hydrolysis reaction, and the best promoting effect on the electronic structure, manifested as the best catalytic performance. The calculation results were consistent with the XPS characterization results and the experimental results of hydrolysis performance testing, revealing the principle of bimetallic synergistic effect on catalytic performance. [Display omitted] • Flower-like Co 2 FeO 4 showed the best catalytic performance. • The "D-band center" and "valence -band center" of Co 2 MO 4 were studied. • Composition and electronic control improve the catalytic performance of Co 2 MO 4. • The adsorption configuration of H 2 O on the Co 2 MO 4 (311) surface was studied. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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4. Carbon dioxide hydrogenation for sustainable energy storage.
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Boretti, Alberto
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CLEAN energy , *CARBON sequestration , *GASOLINE , *ENERGY storage , *CARBON dioxide , *GREEN diesel fuels , *METHYL ether , *METHANOL as fuel - Abstract
This paper explores green hydrogen-based carbon dioxide (CO 2) hydrogenation for the production of oxygenates, presenting it as a pivotal strategy for mitigating carbon emissions and advancing sustainable energy solutions. The conversion of CO 2 into oxygenates through hydrogenation emerges as a promising avenue, particularly in the context of transportation applications where the storage of hydrogen poses challenges. The substitution of fossil diesel and gasoline fuels with green hydrogen-derived dimethyl ether, or methanol/ethanol, is advantageous from a life cycle analysis (LCA) CO 2 emission perspective even without the capture of the CO 2. However, the greatest sustainability appeal is contingent on the crucial aspect of capturing CO 2 when utilizing these fuels, which is an aspect currently absent in the literature. This narrative review comprehensively explores catalytic processes, mechanisms, sustainability perspectives, and the current state of research in this evolving area. It encompasses both the production of oxygenates through CO 2 hydrogenation and the subsequent utilization of these oxygenates in fuel cells or combustion systems, emphasizing the integration of CO 2 capture technologies. The paper contributes to the discourse surrounding the environmental and technological dimensions of energy storage ecosystems, providing a holistic view of their potential to foster sustainable energy solutions. [ABSTRACT FROM AUTHOR]
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- 2024
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5. Effects of H2 blended ratio and N2/CO2 dilution fraction on the deflagration shock wave of H2NG in slender closed pipelines.
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Liu, Qiqi, Liu, Luoqian, Liu, Zhenyi, Peng, Shiyao, Liu, Chuang, Zhang, Hanwen, Liu, Changqi, Li, Pengliang, and Fan, Tao
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SHOCK waves , *NATURAL gas laws , *DILUTION , *THEORY of wave motion , *CARBON dioxide , *NATURAL gas - Abstract
To reveal the deflagration hazard and propagation law of hydrogen-enriched natural gas (H 2 NG) in closed spaces, this paper studied the deflagration characteristic parameters under different H 2 blended ratio (λ) and inert gas dilution fraction (X dilution) in slender closed pipelines with steel circular hole obstacles. The results indicate that the positive feedback mechanism's sustained effect, failure, and re-action leads to a "three-zone" distribution of H 2 NG explosion overpressure along the pipeline, namely the acceleration, attenuation, and rebound zones. The maximum explosion overpressure (P max), maximum pressure rise rate ((dP/dt) max), and peak shock wave propagation velocity (V p) all increase with the increase of λ. The rise of λ has the most significant enhancement effect on (dP/dt) max , while the enhancement effect on V p is the smallest. This is because the main reasons affecting their increase are different. P max , (dP/dt) max , and V p exhibit exponential decay with increased N 2 and CO 2. However, CO 2 has a more significant inhibitory effect on the H 2 NG deflagration process. When X CO2 = 25% and X CO2 = 30%, the deflagration process of H 2 NG with λ = 20% and λ = 80% can be inhibited entirely, respectively, which has important guiding significance for the safe application of H 2 NG. • The evolution law of deflagration shock waves in slender closed pipelines by H 2 NG was researched. • Effects of H 2 blended ratio and N 2 /CO 2 dilution fraction on H 2 NG deflagration characteristics were revealed. • The effects of N 2 /CO 2 dilution fraction on the P max , (dP/dt) max , and V p were predicted by an exponential model. [ABSTRACT FROM AUTHOR]
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- 2024
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6. Towards chemical equilibrium in thermochemical water splitting. Part 2: Re-oxidation.
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de la Calle, Alberto, Ermanoski, Ivan, Miller, James E., and Stechel, Ellen B.
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CHEMICAL equilibrium , *CERIUM oxides , *CARBON dioxide , *HYDROLOGIC cycle , *NOBLE gases , *REMANUFACTURING , *OXIDATION - Abstract
Chemical equilibrium represents the highest efficiency achievable by a thermochemical cycle under specific operational conditions. This study delves into two-step thermochemical water splitting cycles, which dissociate water into hydrogen (H 2) and oxygen (O 2) via sequential thermal reduction and re-oxidation processes. Building on the thermal reduction analysis presented in Part 1, this paper zeroes in on the re-oxidation reaction within the optimal reactor framework – the counter-current reactor. It elucidates the equilibrium pathway, delineating the progression of chemical equilibrium at each incremental stage of re-oxidation. Using ceria (CeO 2) as a model redox-active metal oxide, the investigation analyzes the influence of operational parameters on the re-oxidation reaction. Findings reveal the theoretical feasibility of maintaining near constant temperature (±2.5 °C) during re-oxidation, achieving a total extent of reduction of 0.038 and a hydrogen conversion yield of 32%. While near adiabatic operation is also achievable, practicality is constrained by a maximum total extent of reduction of 6.5·10−3. The study also explores the economic implications of thermochemical water splitting, particularly focusing on the steam-to-hydrogen output ratio. It highlights the severe economic hurdles associated with hydrogen yields below approximately 1%. Furthermore, the investigation reveals that the addition of inert gas to the re-oxidation step offers no significant advantages. Concluding the analysis, a comparative assessment exposes negligible differences in outcomes when substituting carbon dioxide (CO 2) for water (H 2 O) as the oxidant in low-temperature scenarios (800 °C). This comprehensive study not only advances the understanding of re-oxidation dynamics in thermochemical water splitting but also informs practical and economic considerations crucial for the advancement of this technology. • Reversible/equilibrium re-oxidation pathway defined for water splitting cycles. • Reversible quasi-constant temperature and quasi-adiabatic re-oxidation is feasible. • Limited impact of gas purity on re-oxidation at fixed flow/minimum temperature. • Inert gas addition offers no thermodynamic advantage in re-oxidation. • Low re-oxidation temperatures expand the solution space for high cycle efficiency. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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7. Effects of H2/CO ratio and CO2 dilution on the explosion behavior and flame evolution of syngas/air mixtures.
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Su, Bin, Dong, Haowei, Luo, Zhenmin, Deng, Jun, Liao, Pengxiang, Cheng, Fangming, Wang, Tao, Liu, Litao, and Liu, Lu
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SYNTHESIS gas , *DILUTION , *FLAME stability , *FLAME , *CARBON dioxide , *EXPLOSIONS - Abstract
Syngas, which is used as both a fuel and a raw material, presents numerous safety risks during its utilization. In this paper, the effects of H 2 /CO ratio (R = 0%, 30%, 50%, 70% and 100%) and CO 2 dilution ([CO 2 ] = 0%–20%) on the explosion behaviors of syngas/air mixtures with different equivalence ratios (φ = 0.8, 1.0, 1.6, and 2.5) are examined via experiments and numerical calculations. The results show that the peaks of explosion pressure and OH* spectral intensity are significantly influenced by the H 2 percentage in the syngas. The introduction of CO 2 notably decreases these parameters in oxygen-rich and severe oxygen-poor states. Additionally, the flame propagation speed noticeably increases with increasing H 2 proportion in the syngas. The influence of CO 2 on the buoyancy instability of the spherical flame of syngas is considered negligible when compared to that of other combustible gases, such as CH 4. Nevertheless, the presence of CO 2 decreases the density ratio between the unburned gas and burned gas and increases the flame thickness of syngas/air mixtures. This trend reduces the cellular instability of the spherical flame, particularly in severe oxygen-poor states. Notably, there is a definite correlation between the formation of cellular flames and the rise rate of explosion pressure. The cellular structure on the flame surface becomes more pronounced when the rise rate of explosion pressure increases. Conversely, it develops later or is noticeably inhibited. Furthermore, the main reaction pathways are H 2 → ∙OH → H 2 O 2 → H 2 O and H 2 → ∙OH → CO → CO 2 during the syngas explosion process. ∙OH is critical in the entire chain reaction because it promotes the conversion of H 2 to H 2 O and acts as a vital connection between the reactants H 2 and CO in the explosion process. • The P max and I max were investigated with H 2 addition and CO 2 dilution. • The cellular instability of the spherical flame was analyzed. • The interaction of flame development and explosion pressure was revealed. • The main reaction pathways during the syngas explosion process were examined. [ABSTRACT FROM AUTHOR]
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- 2024
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8. Life cycle assessments use in hydrogen-related policies: The case for a harmonized methodology addressing multifunctionality.
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Arrigoni, Alessandro, Hurtig, Oliver, Buffi, Marco, Eynard, Umberto, Andreasi Bassi, Susanna, Scarlat, Nicolae, and Dolci, Francesco
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PRODUCT life cycle assessment , *GREENHOUSE gases , *INCENTIVE (Psychology) , *CARBON dioxide , *GREENHOUSE gas mitigation - Abstract
Legislation regulating the sustainability requirements for hydrogen technologies relies more and more on life cycle assessments (LCAs). Due to different scopes and development processes, different pieces of EU legislation refer to different LCA methodologies, with differences in the way multifunctional processes (i.e., co-productions, recycling, and energy recovery) are treated. These inconsistencies arise because incentive mechanisms are not standardized across sectors, even though the end product, hydrogen, remains the same. The goal of this paper is to compare the life-cycle greenhouse gas (GHG) emissions of hydrogen from four production pathways depending on the multifunctional approach prescribed by the different EU policies (e.g., using substitution or allocation). The study reveals a large variation in the LCA results. For instance, the life-cycle GHG emissions of hydrogen co-produced with methanol is found to vary from 1 kg CO 2 -equivalent/kg H 2 (when mass allocation is considered) to 11 kg CO 2 -equivalent/kg H 2 (when economic allocation is used). These inconsistencies could affect the market (e.g., hydrogen from a certain pathway could be considered sustainable or unsustainable depending on the approach) and the environment (e.g., pathways that do not lead to a global emission reduction could be promoted). To mitigate these potential negative effects, we urge for harmonized and strict guidelines to assess the life-cycle GHG emissions of hydrogen technologies in an EU policy context. Harmonization should cover international policies too, to avoid the same risks when hydrogen will be traded based on its GHG emissions. The appropriate methodological approach for each production pathway should be chosen by policymakers in collaboration with the LCA community and stakeholders from the industry based on the potential market and environmental consequences of such choice. • LCA methodologies for hydrogen-related policies are currently not fully harmonized. • Four hydrogen production pathways involving multifunctionality were analysed. • GHG emissions of hydrogen vary significantly with the LCA methodology adopted. • Inconsistencies can lead to market distortions, inefficiencies, and confusion. • There is an urgent need for harmonized and strict LCA guidelines for H2 production. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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9. Mo-based bimetallic oxide catalysts for the reverse water gas shift reaction.
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Dai, Hui, Deng, Xiaobing, Zhang, Anhang, Zhu, Yongqing, Xiao, Xin, Wang, Yan, and Zhou, Changjian
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WATER gas shift reactions , *BIMETALLIC catalysts , *CERIUM oxides , *WATER-gas , *CARBON dioxide - Abstract
The reverse water gas shift (RWGS) is of great significance to the resource utilization of CO 2. In this paper, based on the features of MoO 3 , the Mo-based catalysts doped with Ga, Ti and Ce were prepared, and the effects of oxygen vacancies and basic sites on the RWGS reaction were studied. When the volume ratio of H 2 and CO 2 is 1 : 1, the yield of CO can reach 26.66%. Because it exposes higher concentration of Ce sites and moderate alkaline active sites on the surface. When the proportion of H 2 in the reaction gas increases, the highest yield of CO can reach 54.53%, which is mainly attributed to a large number of oxygen vacancies on the surface of MoTi. This study can be used as a reference for the design of catalysts for RWGS reaction under different reaction conditions. A series of Mo-based catalysts were prepared, and the significance of oxygen vacancies and surface basic sites in RWGS reaction was explored, and a reference was provided for the study of similar catalytic materials under different reaction gas ratios. [Display omitted] • MoO 3 by doping transition metal has a good application prospect in RWGS reaction. • The yield of MoTi and MoCe is close to equilibrium in RWGS reaction. • High CO 2 concentration is good for MoTi with higher density oxygen vacancies. • High H 2 concentration is good for MoCe with higher density surface basic sites. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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10. Transition metal dichalcogenides-based catalysts for CO2 conversion: An updated review.
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Khaidar, Dalilah Mohmad, Isahak, Wan Nor Roslam Wan, Ramli, Zatil Amali Che, and Ahmad, Khairul Naim
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TRANSITION metal catalysts , *NATURAL gas , *GREENHOUSE effect , *CARBON dioxide , *FOSSIL fuels , *COALBED methane , *PETROLEUM , *FORMIC acid - Abstract
The rapid depletion of fossil fuels has become the worst scenario as most of the energy needed still depends on the use of fossil energy, oil, natural gas, and coal. The combustion of crude oil and coal has contributed to the major anthropogenic carbon dioxide (CO 2) gas in the atmosphere and has worsened climate change and global warming. Therefore, the abundant CO 2 in the surrounding has opened the door to many studies to convert CO 2 into the next generation of fuels and indirectly reduce the greenhouse effect. Transition metal dichalcogenides (TMDs) nanomaterials have appeared as a practical and reliable catalyst for CO 2 conversion to sustainable fuels under normal atmospheric conditions. Having fascinating electronic and catalytic properties, these earth-abundant element-based materials are being explored and developed for real-world application. This paper reviews the recent insight into the synthesis, properties and application of TMDs as catalysts in electrocatalysis, photocatalysis and thermal catalysis for CO 2 reduction and conversion. The role of type of sulfide (S), selenide (Se) and telluride (Te)-based TMDs in the production of various valuable products such as formate (HCO 2 −), formic acid (CH 2 O 2), methanol (CH 3 OH), and ethanol (CH 3 CH 2 OH), amongst others, will be discussed in detail. The possible reaction pathways and mechanisms and the relationship between tailoring the catalysts properties and CO 2 activation towards high CO 2 reduction and conversion efficiency will also be evaluated. • TMD catalysts have demonstrated promising performance in converting CO 2. • TMD catalyst can be used for electro-, photo- and thermal-catalytic CO 2 conversion. • The synthesis and characterization methods of TMD catalysts has been reviewed. • The different types of TMD catalysts and their potential have been investigated. • The mechanisms of all catalytic reactions have been examined. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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11. A systematic review of CO2 injection for enhanced oil recovery and carbon storage in shale reservoirs.
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Wang, Lu, Zhang, Yifan, Zou, Rui, Zou, Run, Huang, Liang, Liu, Yisheng, Meng, Zhan, Wang, Zhilin, and Lei, Hao
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ENHANCED oil recovery , *SHALE , *SHALE oils , *PROPERTIES of fluids , *CARBON dioxide - Abstract
Global shale oil is abundant in geological reserves, but there are widespread problems of difficult exploitation and unsatisfactory oil recovery. CO 2 injection in shale reservoirs can achieve effective exploitation of shale reservoirs and alleviate the current energy shortage. In this paper, investigations on shale oil in recent years were summarized and analyzed. Firstly, the reservoir characteristics and fluid properties of several shale reservoirs and their effects on CO 2 -enhanced oil recovery (CO 2 -EOR) were analyzed, including porosity, permeability, mineral composition, pore structure, geomechanical characteristics and organic matter properties of shale reservoirs, as well as the density, viscosity, gas-oil ratio and composition of shale oil. Subsequently, multiple mechanisms of CO 2 -EOR in shale reservoirs were revealed, including swelling, diffusion, viscosity reduction, extraction, miscibility, and competitive adsorption. The effects of temperature, pressure, CO 2 injection amount, oil composition and reservoir heterogeneity on different mechanisms were analyzed. The effects of nanopore confinement and CO 2 injection on the fluid phase were also analyzed. Then, the CO 2 storage forms of structural space, bound space, dissolution, and mineralization were introduced. And the effects of temperature, pressure, reservoir heterogeneity and formation water salinity on various forms of CO 2 storage were summarized. Furthermore, the research methods of CO 2 injection technique through molecular simulation, physical simulation, mathematical model, and reservoir numerical simulation were introduced. Finally, the reasonable prospect of CO 2 injection technique for shale oil reservoirs was proposed based on the current technical problems. The purpose of this paper is to provide a theoretical basis for EOR and carbon geological storage of shale reservoirs by using the CO 2 injection technique. [Display omitted] • Reservoir and fluid properties of major shale oil reservoirs were summarized. • EOR mechanisms of CO2 injection in shale reservoirs were reviewed systematically. • Research methods of CO2 injection techniques in shale reservoirs were introduced. • Future perspectives of CO 2 injection techniques in shale reservoirs were analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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12. Tuning of physicochemical and electronic characteristics of Cu-doped NiCo2O4 ternary inverse spinel oxides for effective electrocatalytic hydrogen evolution reaction.
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Nair, Durga S., Anil, Anaswara, Elias, Liju, Satyanarayana, N., Holla, Harish Kumar, and Shibli, S.M.A.
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HYDROGEN evolution reactions , *TRANSITION metal oxides , *SPINEL , *METALLIC oxides , *COPPER , *CARBON dioxide , *OXIDES - Abstract
The paper reports the development of Cu-doped NiCo 2 O 4 ternary inverse spinel oxides through microwave-assisted hydrothermal method as effective catalysts for alkaline hydrogen evolution reaction (HER). The effective and controlled doping of Cu to NiCo 2 O 4 lattice by the partial replacement of Ni2+/Ni3+ with Cu+/Cu2+ results in the fine-tuning of structural, morphological, and electronic characteristics, favourable for electrocatalytic HER. The study effectively correlates the influence of variation in the percentages of Cu-doping on the material properties and thereby the electrocatalytic characteristics. The experimental results indicate that Cu 0.10 Ni 0.90 Co 2 O 4 electrode having optimum Cu-doping (10%) as the best electrocatalyst with the lowest onset potential for hydrogen evolution (242.7 mV) and reduced overpotential (72.5 mV) values by following a Volmer – Heyrovsky mechanism during HER. The improvement in HER performance after Cu-doping is due to the generation of greater number of active sites and reduction in electronic band gap. The present work advantageously utilises the scope of microwave-assisted transition metal doping strategy to fine tune the physicochemical and electronic characteristics, favourable for electrocatalytic HER, and this may pave a new way for tuning the electrochemical properties of metal oxides for various applications. • Microwave-assisted hydrothermal synthesis is used effectively to develop Cu-doped NiCo 2 O 4. • Cu-doping to NiCo 2 O 4 lattice creates more oxygen vacancies and improves electronic conductivity. • Cu 0.10 Ni 0.90 Co 2 O 4 with 10% Cu-doping exhibits promising electrocatalytic activity towards HER. • Cu-doped NiCo 2 O 4 follows Volmer – Heyrovsky mechanism during alkaline HER. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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13. Research progress of bimetallic catalysts for CO2 hydrogenation to methane.
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Wei, Chaojie, Ding, Honglei, Zhang, Ziyi, Lin, Feng, Xu, Yifeng, and Pan, Weiguo
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BIMETALLIC catalysts , *CARBON emissions , *CARBON dioxide , *GREENHOUSE effect , *CATALYTIC activity , *ACTIVATION energy - Abstract
It is well known that solving the greenhouse effect caused by increasing CO 2 emissions is urgent, and CO 2 methanation reaction is a popular research area as one of the effective ways. However, there are great obstacles and challenges to develop catalysts with higher stability and catalytic activity. In order to reduce the activation energy required for methanation reactions, it is expected to introduce another metal into monometallic catalysts to form bimetallic catalysts through the synergistic effect between the bimetallic phases. This paper reviews the advantages of metal-phase combinations for bimetallic catalysts applied to CO 2 methanation. The main synthetic methods used to prepare bimetallic catalysts in recent years are discussed. The effects of bimetallic phase synergy, bimetallic phase structure, metal particle size and dispersion, metal component ratio, and carrier effect on catalyst performance are analyzed. Finally, the challenges and application prospects of bimetallic catalysts for CO 2 methanation are presented. • Hydrogenation mechanisms for combinations of combination of dual active components are analyzed. • The preparation method and auxiliary preparation technology of bimetallic catalyst are discussed. • The synergistic effect between the two metal phases should sometimes be enhanced and sometimes suppressed. • The structure between the two metal phases improves the efficiency of the catalysts. • Different catalyst particle sizes affect product generation in CO2 hydrogenation reactions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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14. Review of electrocatalytic reduction of CO2 on carbon supported films.
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Yuda, Afdhal, Ebrahimi, Parisa, Selvaraj, Josephine, Kumar, Anand, and Subramanian, Vaidyanathan (Ravi)
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CARBON films , *CARBON-based materials , *TRANSITION metal oxides , *BIMETALLIC catalysts , *CARBON dioxide , *CARBON dioxide reduction , *ELECTROLYTIC reduction , *SOLVENTS , *ATMOSPHERIC carbon dioxide - Abstract
Carbon capture and conversion are becoming increasingly important as atmospheric CO 2 concentrations rise and their adverse effects become increasingly evident. CO 2 conversion/utilization-related research has gained renewed interest on a variety of platforms, including thermal, solar, biological, photochemical, and electrochemical conversions. Electrochemical routes, using suitable catalysts, are potentially suitable for commercial purposes owing to ease of integration with solvent-based carbon capture processes. This paper summarizes and evaluates the studies conducted within the past decade regarding the feasibility of carbon-based supports utilized in electrocatalytic carbon dioxide reduction. CO 2 conversion has been reviewed in a number of reports, focusing on specific sections, such as metallic/bimetallic catalysts, CO 2 solubility, and the fabrication of electrodes and electrochemical cells. The number of publications addressing various carbon-based electrocatalysts is increasing, but these materials have not yet been reviewed. Herein, we are focused on three types of electrocatalyst materials: metals, metal-oxides, non-oxides, and combinations thereof with carbon. The scope of this study includes the following: i) carbon-based materials and how they are characterized by distinctive properties, ii) electrocatalytic CO 2 conversion techniques, and iii) research cases for carbon allotrope-supported composites used in CO 2 reduction. The advancement in analytical tools that provide insight into liquid-phase reactions will benefit the development of catalysts and electrodes that will be effective in converting CO 2 into the desired products. Such developments will also be applicable to other systems involving liquid electrolytes or solvents for performing reactions on catalyst surfaces. • A comprehensive review of carbon-based electrocatalysts for CO 2 conversion. • High conductivity of carbon-based materials is suited for superior charge transfer. • Their large surface areas helps in dispersing and stabilizing active sites. • Transition metal oxides provide a large distribution of products in CO 2 reduction. • Catalysts composition and structure govern CO 2 activity and product distribution. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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15. Parametric analysis of a modified ammonia-hydrogen-electricity cogeneration system.
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Kang, Zongyao, Liu, Bin, She, Xiaohui, Liu, Wei, Huang, Jingzhong, and Wang, Kaihui
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BRAYTON cycle , *COGENERATION of electric power & heat , *HYDROGEN production , *ENERGY consumption , *RANKINE cycle , *CARBON dioxide , *HYDROGEN storage , *NUCLEAR energy - Abstract
In this paper, a novel ammonia-hydrogen-electricity cogeneration system is developed. To mitigate the cost associated with hydrogen storage and transportation in later stages, the proposal is to utilize high-temperature ammonia production instead of conventional hydrogen production. A comparative analysis between ammonia and transportation for hydrogen is conducted to assess cost efficiencies. To improve the system efficiency, a supercritical CO 2 Brayton cycle is applied as the power generation cycle. This choice exhibits superior parameter compatibility with the system compared to the Rankine cycle. The study scrutinizes the impacts of different energy utilization sequences and varying process parameters of the power generation cycle on the system's performance to ascertain the most optimal configuration. The results indicate that the Brayton cycle is more suitable for integration with the nuclear-IS thermochemical hydrogen production system, significantly enhancing the power generation capacity of the ammonia-hydrogen-electricity cogeneration system. These improvements result in 18.8 % increase in power generation efficiency and a 9.3 % boost in overall energy efficiency of the system. Subsequent to this enhancement, the system attains an impressive energy efficiency of 47.0 % along with a system exergy efficiency of 63.4 %. This study introduces an innovative approach for optimizing and enhancing the energy efficiency of a cogeneration system by employing nuclear energy as a high-temperature heat source for hydrogen (ammonia) production. • A novel ammonia-hydrogen-electric cogeneration system is developed. • The system bolsters efficiency by 9.3 % through a synergistic Brayton cycle coupling. • Conducted an assessment and comparison of the transportation and storage expenses associated with hydrogen and ammonia. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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16. Machine learning analysis of catalytic CO2 methanation.
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Yılmaz, Beyza, Oral, Burcu, and Yıldırım, Ramazan
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MACHINE learning , *METHANATION , *STANDARD deviations , *RANDOM forest algorithms , *CARBON dioxide , *DESCRIPTOR systems , *BIOMASS conversion - Abstract
In this work, a detailed dataset containing 4051 data points gathered from 527 distinct experiments in 100 published articles for catalytic CO 2 methanation was analyzed using machine learning methods. A pre-analysis of the database was performed using simple descriptive statistics while a random forest (RF) model was developed to predict CO 2 conversion as the function of 23 descriptors including catalyst properties, preparation methods, and reaction conditions. Boruta analysis was also performed to identify the significant variables. The random forest model was found to be quite successful in predicting CO 2 conversion with the training and testing root mean square error (RMSE) of 6.4 and 12.7 respectively; R2 was 0.97 for training while it was 0.85 for testing. The success of the model was also verified by computing CO 2 conversion profiles for individual experiments in test data and comparing them with those reported in the related papers. [Display omitted] • Catalytic CO 2 methanation was studied using machine learning. • Dataset contained 4051 data points from 100 published paper. • Simple descriptive statistics and random forest (RF) were used as tools. • RF successfully predicted CO 2 conversion profiles for the test cases. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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17. A parametric study on hydrogen production by fluidized bed co-gasification of biomass and waste plastics.
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Erdem, Kaan, Gündüz Han, Duygu, and Midilli, Adnan
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PLASTIC scrap , *BIOMASS gasification , *HYDROGEN production , *COAL gasification , *HIGH density polyethylene , *BIOMASS , *CARBON dioxide - Abstract
This paper presents a parametric study on hydrogen production potential from biomass and waste plastics via fluidized bed co-gasification technique by using different gasifying agents such as steam, air and CO 2. In this regard, a new Aspen Plus model representing this process was developed. For this purpose, first, a comparative feedstock selection between several materials was performed, ultimately identifying the cotton husk (CH) and high-density polyethylene (HDPE) mixture as the most promising choice. Secondly, the study focused on steam co-gasification of CH with HDPE to assess the impact of various factors, including plastic content in feedstock, temperature, steam to feedstock ratio (S/F), and the introduction of gasifying agents, namely air and CO 2, next to steam. The analysis mainly examined the influence of these parameters on the composition of syngas, calorific value, and the hydrogen production. Accordingly, it was determined that an increase in plastic content and S/F ratio resulted in higher hydrogen concentration in the syngas, and the maximum quantity of H 2 with 1189.3 Nm3/ton feed was produced at 900 °C. In addition, co-utilization of air or CO 2 with steam as a gasifying agent deteriorated the system performance regarding H 2 yield. Thus, it is expected that the model developed will contribute to the researchers, investors, engineers and policy maker working on the gasification technology for hydrogen production. [Display omitted] • Possible mixtures of various biomass and plastics for co-gasification was compared. • H 2 production from cotton husk and HDPE co-gasification showed promising results. • Use of steam, steam & air and steam & CO 2 as gasification agent was studied. • Co-gasification of mixtures with more plastic content yielded greater hydrogen. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
18. Highly stable hierarchical core-shell structure CuMn0.5Co2O4@CC with self-regulating electronic and conductivity for its improved OER performance.
- Author
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He, Xuanmeng, Jing, Yunxiang, Wang, Louqian, Zhang, Zeqin, Liu, Hui, and Wang, Xinzhen
- Subjects
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HYDROGEN evolution reactions , *OXYGEN evolution reactions , *CARBON dioxide , *ELECTRONIC structure , *ELECTRIC conductivity , *STRUCTURAL stability , *METALLIC composites - Abstract
Improving the catalytic activity and long-term stability of catalysts have always been the goal of its application. The structure stability and good electrical conductivity of catalysts are the key to OER performance, which have been challenge for application of catalysts. In the paper, we designed an in-situ growth of hierarchical core-shell structure CuMn 0.5 Co 2 O 4 @CC with superior conductivity directly as the catalytic electrode for improved OER performance. The well-standing CuMn 0.5 Co 2 O 4 nanoneedles with mesoporous structure entirely encapsulated on the carbon fibers, exposing a large special surface area and structural stability, while carbon fibers improved its electrical conductivity. Meanwhile, the richer oxygen vacancies and self-regulating electronic structure by the diversification of the metal oxidation state in the catalyst would promote the OER activity and stability. Benefitting from these merits, the requiring overpotential of CuMn 0.5 Co 2 O 4 @CC was 189 mV at the current density of 10 mA cm−2 and the Tafel slop value was 64.1 mV⋅dec−1, which was lower than that of CuMn 0.5 Co 2 O 4 //CC (η 10 = 337 mV and Tafel slop value of 113.9 mV⋅dec−1). In addition, the CuMn 0.5 Co 2 O 4 @CC had a competitive stability of with the current retention rate of 95.3 % after 1000 cycles. The present work provide a useful attempt to construct highly catalytic active and durably stable metal oxide composite catalysts. The synthesized CuMn 0.5 Co 2 O 4 @CC electrode exhibited the excellent OER activity (η 10 = 189 mV and Tafel slope of 64.1 mV⋅dec−1) and higher stability (the current retention rate of 95.3 % after 1000 cycles), which was attributed to the excellent conductivity of carbon fiber, the large surface area of active ingredients, and the regulated electronic structure with adjacent elements. [Display omitted] • The large special surface area and coupled with high structural stability for CuMn 0.5 Co 2 O 4 @CC catalyst. • The richer oxygen vacancies and self-regulating electronic structure promote the OER performance. • The improving OER activity and stability was attributed to the synergetic coupling effect between CC and CuMn 0.5 Co 2 O 4. • A lower overpotential of 189 mV, Tafel slop of 64.1 mV⋅dec−1, and the current density retention of 95.3 % were obtained. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
19. NO emission characteristics for the HTC and MILD combustion regimes with N2, N2/CO2 and CO2 diluents: effect of H2 addition to CH4.
- Author
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Fordoei, Esmaeil Ebrahimi and Boyaghchi, Fateme Ahmadi
- Subjects
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COMBUSTION , *METHANE , *CARBON dioxide , *NITROGEN , *NUMERICAL calculations - Abstract
In this paper, the effect of H 2 addition to CH 4 on the NO emission of oxy-fuel, oxygen-enriched, and air-fuel MILD combustion is studied by numerical and chemical calculations. In the CFD section, the University of Lisbon MILD furnace is modeled. The results show that H 2 added to CH 4 is associated with a higher NO emission in the same oxidant composition. It is due to higher NO formation by NNH and thermal mechanisms. It can be found that by transformation from air-fuel to oxy-fuel MILD regimes, NO emission is reduced significantly. Moreover, the addition of H 2 prevents flame extinction that often occurs under MILD conditions when CO 2 replaces N 2. Reaction pathway analysis displays that dominant routes of NO emission in the H 2 -lean are N 2 O-intermediate for the air-fuel and oxygen-enriched conditions and NNH for the oxy-fuel MILD regime. In the H 2 -rich condition, the NNH mechanism plays the most important role in the NO production. • X H2,cr is known that in the higher values of it, NO emission increases dramatically. • H 2 added to CH 4 prevents flame extinction due to the replacement of CO 2 with N 2. • Change of diluent form N 2 to CO 2 reduces significantly NO emission under MILD regime. • H 2 -lean shows N 2 O-intermediate as main NO mechanism of air-fuel and oxygen-enriched. • NNH is the main route in the NO emission of CH 4 /H 2 -rich MILD regime. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
20. Enhanced CO2 hydrogenation to light hydrocarbons on Ni-based catalyst by DBD plasma.
- Author
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Ullah, Niamat, Su, Meng, Yang, Yuwang, and Li, Zhenhua
- Subjects
- *
METHANATION , *HYDROGENATION , *CARBON dioxide , *EMISSION spectroscopy , *NONEQUILIBRIUM plasmas , *CATALYSTS , *THERMAL plasmas - Abstract
The high thermal stability of CO 2 makes its conversion low in conventional thermal catalysis. Comparatively, non-equilibrium plasma technique provides an efficient way for CO 2 hydrogenation under mild reaction conditions. Introducing effective catalysts to the dielectric barrier discharge (DBD) plasma reactor may further improve CO 2 hydrogenation performance. In this way, the interaction between plasma and catalysts is important to contribute CO 2 hydrogenation performance. Considering Ni-based catalyst is active for CO 2 hydrogenation, we used three different kinds of carrier materials including CeO 2 , γ-Al 2 O 3 and ZSM-5 as supports to prepare nickel-based catalysts by incipient impregnation in this paper. The supported Ni catalysts were tested for the plasma-induced CO 2 hydrogenation to CH 4 and C 2+ hydrocarbons in the DBD-plasma reactor. It was found that the 15Ni/CeO 2 catalyst achieved the best CO 2 conversion of 85.7% and nearly 100% CH 4 selectivity at 300 °C due to its high reducibility and CO 2 chemisorption capacity. In addition, a significant synergistic effect was found between DBD plasma and catalyst. The performance of plasma-catalysis was considerably better than that of thermal catalysis plus pure plasma reaction, and the synergistic effects were enhanced with increase of reaction temperature. Moreover, the mechanism of the synergistic effect was proposed by analyzing the optical emission spectroscopy (OES) of DBD plasma, which provides a theoretical basis for further optimizing and application of plasma-catalysis for CO 2 hydrogenation reaction. [Display omitted] • CO 2 hydrogenation to CH 4 and C 2+ hydrocarbons was enhanced by plasma-catalysis. • The 15Ni/CeO 2 showed better activity due to better reducibility and CO 2 chemisorption ability. • A synergistic effect between plasma and catalyst was enhanced with increase in reaction temperature. • The synergistic mechanism between plasma and catalysts was proposed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. Promotion effect of different lanthanide doping on Co/Al2O3 catalyst for dry reforming of methane.
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Liang, Zhoujie, Zhang, Yu, Zhang, Guojie, Liu, Jun, Cai, Yajing, Wang, Ying, Zhao, Yuqiong, Li, Guoqiang, and Bei, Kunlun
- Subjects
- *
STEAM reforming , *RARE earth oxides , *RARE earth metals , *CARBON dioxide adsorption , *COBALT catalysts , *CATALYSIS , *METALLIC oxides - Abstract
In this paper, a series of cobalt catalysts modified by different lanthanide metals were synthesized via co-impregnation method using inexpensive industrial-grade alumina as a support for dry reforming of methane. The effect of lanthanide metals as accelerators of cobalt-based catalysts on catalytic performance and anti-coking properties was mainly investigated. The textural relationships between the catalytic performance and physicochemical properties of cobalt-based catalysts doped with different lanthanide metals were further investigated. Different characterization techniques demonstrate the positive effect of lanthanide metals on the physicochemical properties of catalysts. The results show that the electron transfer between cobalt species and lanthanide metal oxides is significantly enhanced due to the introduction of lanthanide elements. The process generates more active sites, which is favorable for the adsorption and activation of methane. In addition, the abundant medium basic sites and oxygen vacancies on the surface of cobalt-based catalysts with the effect of lanthanides promoted the adsorption and activation of carbon dioxide and the gasification of carbon accumulation, which greatly improved the anti-carbon accumulation performance of the catalysts. Therefore, the prepared cobalt-lanthanum-based catalysts showed the best catalytic effect and have great potential for application. • The introduction of lanthanides enhances the electron transfer ability of Co species. • The introduction of lanthanides enhanced the anti-coking performance of the catalyst. • The introduced lanthanides provide abundant active sites for the activation of CH 4 and CO 2. • It provides an efficient and economical strategy for the industrial application of dry methane reforming. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
22. EDTA impregnation assisted synthesis of nickel nanoparticles embedded in activated carbon and its application for dry reforming of methane.
- Author
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Qin, Linbo, Hu, Ziqin, Hu, Mufang, Zhao, Bo, Kong, Lingtian, Chen, Wangsheng, and Han, Jun
- Subjects
- *
ACTIVATED carbon , *METHANE , *ETHYLENEDIAMINETETRAACETIC acid , *NICKEL catalysts , *STEAM reforming , *CARBON dioxide - Abstract
In this paper, the catalysts with nanoscale nickel particles embedded in activated carbon were synthesized by Ethylenediaminetetraacetic acid (EDTA) assisted impregnation method. The experimental results revealed that EDTA addition could promote Ni particle dispersion and decrease Ni particle size. Ni particle size was significantly decreased from 18.23 to 4.57 nm when Ni/EDTA ratio was increased from 1:0 to 1:3. Catalytic performance of Ni 15 -AC-E 3 demonstrated that CH 4 and CO 2 conversion rate under 850 °C were 90.05% and 96.28%, which were decreased by 1.08% and 1.27% after 72 h dry reforming methane (DRM) reaction. Moreover, the characteristic of the used catalyst showed that Ni particle size was only increased from 4.57 to 5.94 nm after the stability test, and NiO was not appeared. Meanwhile, the deposited carbon in the used catalyst was 5.02%. The above results meant that the catalyst prepared by EDTA assisted impregnation method had the ability of suppressing carbon deposition, Ni particle sintering and oxidation during DRM reaction. • EDTA addition could promote Ni particle dispersion and decrease Ni particles size. • The average Ni particle diameter in Ni 15 -AC-E 3 was only 4.57 nm. • CH 4 and CO 2 conversion rate over Ni 15 -AC-E 3 under 850 °C were 90.05% and 96.28%. • CH 4 and CO 2 conversion rate were only decreased by 1.08% and 1.27% after 72 h reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
23. Performance and durability of metal-supported solid oxide electrolysis cells at intermediate temperatures.
- Author
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Wang, Zhongxu, Wang, Yue, Li, Naizhi, Tong, Yongcheng, Teng, Yue, Wang, Di, Chen, Chusheng, and Zhan, Zhongliang
- Subjects
- *
HIGH temperature electrolysis , *ELECTROLYSIS , *CARBON dioxide , *METALLIC oxides , *OHMIC resistance , *WIND power , *STAINLESS steel , *STAINLESS steel corrosion - Abstract
Metal-supported solid oxide electrolysis cells (MS-SOECs) operating at 600–700 °C are attractive for storage of intermittent renewable electricity from solar and wind energy due to their advantages of easy sealing and fast startup. This paper reports on the fabrication of MS-SOECs consisting of dense scandium stabilized zirconia (SSZ) electrolytes, Ce 0.8 Sm 0.2 O 2−δ (SDC)/Ni impregnated 430L/SSZ cathodes and SmBa 0.5 Sr 0.5 Co 2 O 5+δ (SBSCO) impregnated SSZ anodes supported on porous 430L alloys. Such cells demonstrated excellent electrolysis performance with current densities at 650 °C as high as 0.73 A⋅cm−2 at 1.3 V in 50% H 2 O-50% H 2 and 0.95 A⋅cm−2 at 1.5 V in 90% CO 2 -10% CO. Electrochemical impedance measurements indicated that the cell performance was largely limited by the ohmic losses for steam electrolysis and by the cathodic reduction reactions for CO 2 electrolysis, especially at reduced temperatures. Pronounced degradation was observed for both steam and CO 2 electrolysis over the preliminary 90-h stability measurements at 600 °C. SEM examination and EDS mapping of measured cells showed significant aggregation and coarsening of impregnated Ni particles, resulting in smaller activities for H 2 O and CO 2 reduction reactions. As evidenced by the almost unaltered ohmic resistances over the measurement durations, the 430L stainless steel substrates demonstrate excellent resistances against corrosions from H 2 O and CO 2 and thus show great promise for applications in reduced-temperature MS-SOECs. • 430L stainless steel is applied as the support of SOECs. • Ce 0.8 Sm 0.2 O 1.9 /Ni and SmBa 0.5 Sr 0.5 Co 2 O 5+δ are impregnated into the scaffolds. • The MS-SOECs show excellent performance at intermediate temperatures of 600–700 °C. • Coarsening of impregnated Ni particles is the main reason for degradation. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
24. The upper thermal efficiency and life-cycle environmental assessment of nuclear-based hydrogen production via splitting H2S and CO2.
- Author
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Liu, Hong, Zhou, Zuoyong, Lv, Wendong, Ye, Haotian, and Dong, Hongguang
- Subjects
- *
THERMAL efficiency , *PRODUCT life cycle assessment , *CARBON emissions , *INTERSTITIAL hydrogen generation , *NUCLEAR energy , *CARBON dioxide , *HYDROGEN as fuel , *HYDROGEN production - Abstract
It is proposed to develop a novel thermochemical cycle using nuclear energy to decompose H 2 S and CO 2 , thus producing H 2 and CO from acidic gas in petrochemical or coal chemical industries, reducing CO 2 emissions and promoting sustainable energy development. The upper limits and significant energy-consuming steps were determined based on two chemical routes of the thermochemical cycle systems 1 and 2. When the enthalpy of the H 2 S oxidation reaction served as part of the circulating energy input, the values for system 1 and system 2 were 38.7% and 34.3%, respectively. However, if only external energy is considered to satisfy the heat and work required to run the reaction and pump, the thermal efficiency rises to 58.4% and 61.2%, respectively. The life cycle assessment (LCA) was used to investigate the environmental effect of the hydrogen generation process base on the upper thermal efficiency in this study, and the results of the LCA are stated in terms of global warming potential (GWP) and acidification potential (AP). The GWP of systems 1 and 2 was calculated as 2.59 kg CO 2 -eq/kg H 2 , 2.54 kg CO 2 -eq/kg H 2 , The AP of systems 1 and 2 was calculated as 7.48 g SO 2 -eq/kg H 2 and 9.08 g SO 2 -eq/kg H 2 , respectively. This paper assesses the environmental effect of two different hydrogen systems used in manufacturing various subsystems in GWP and AP, and compares them to the life cycle of other hydrogen production pathways. • A novel thermochemical cycle using nuclear energy to split H 2 S-CO 2 is proposed. • Energy-consuming steps and the upper thermal efficiency were determined. • The upper thermal efficiency has been developed to assess environmental impacts. • The LCA integrated China's HTR-PM with the innovative H 2 S-CO 2 process. • GWP and AP in the H 2 S-CO 2 system are compared to other hydrogen methods. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. Experimental research on a blended hydrogen-fuel engine.
- Author
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Zhunqing, Hu, Nannan, Sun, Yi, Jia, and Xin, Zhang
- Subjects
- *
HYDROGEN as fuel , *ENGINE cylinders , *GAS as fuel , *INTERNAL combustion engines , *ENGINES , *CARBON dioxide - Abstract
An experimental study on the performance of a single cylinder engine fueled with hydrogen/gas fule blends was carried out. The performance of engine with different fuel components under the load characteristics of the engine was analyzed. The experimental results showed that with the increase of hydrogen blending ratio, the combustion speed was accelerated, and the maximum torque and maximum pressure in the cylinder were increased; The maximum torque of blended fuel with 40% CO 2 was 68.3% of that without CO 2 ; The maximum pressure in cylinder of blended fuel with 40% H 2 was 1.6 times higher than that without hydrogen; When the proportion of hydrogen was more than 30%, the torque decreased; When the mixture was blended with 30% N 2 , the engine torque reached the maximum at the hydrogen ratio of 15%; With the increase of hydrogen blending ratio, the emission of CO increased and the emission of HC and NOx decreased; When the hydrogen blending ratio remained unchanged, the CO emission was the largest at medium load, the HC emission was the largest at small load, and the NOx emission was the largest at high load; When the mixture was blended with 15% H 2 , with the increase of the proportion of nitrogen, emission of CO decreased, emissions of HC and NOx increased. The research of this paper provided an experimental basis for the design and development of gas fuel engines. • The maximum torque and the maximum pressure in the cylinder increase with the increase of H 2 ratio in mixture. • When the throttle opening is fixed,the engine torque of mixture blended with 15% H 2 is the maximum. • Engine power is affected by both the combustion speed and the calorific value of the mixture. • With the increase of hydrogen blending ratio, CO increases and HC and NOx decreases. • Remain H 2 unchanged, with the increase of N 2 , CO decreases, HC and NOx increase. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
26. Direct formation of dendritic Ag catalyst on a gas diffusion layer for electrochemical CO2 reduction to CO and H2.
- Author
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Ham, Yu Seok, Kim, Myung Jun, Lim, Taeho, Kim, Dong-Kwon, Kim, Soo-Kil, and Kim, Jae Jeong
- Subjects
- *
SILVER catalysts , *ELECTROCHEMICAL analysis , *CARBON dioxide , *CARBON paper , *ELECTROPLATING , *POLYETHYLENE glycol - Abstract
Dendritic Ag (a CO 2 -to-CO reduction catalyst) has been synthesized on carbon paper (CP) using pulse electrodeposition to fabricate a gas diffusion electrode. A combination of sonication and pulse deposition facilitated mass transfer of Ag ions to the CP, enlarging the catalyst active surface area without significantly changing the Ag crystalline structure. The current density of CO 2 reduction was proportional to the surface area of dendritic Ag. Further improvements in performance were achieved by adding polyethylene glycol to the CO 2 reduction cell catholyte that removed the CO gas bubbles produced at the electrode surface. The fabrication methods presented herein suggest an effective gas diffusion electrode for application in the membrane-electrode-assembly-type single cell for electrochemical CO 2 reduction. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
27. Effects of CO2 addition on deflagration characteristics of syngas-air premixed mixtures in T-pipeline.
- Author
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Wei, Shengnan, Deng, Haoxin, Xu, Zhuangzhuang, Yan, Mengmeng, Wen, Xiaoping, Wang, Fahui, and Chen, Guoyan
- Subjects
- *
CHEMICAL kinetics , *FLAME spread , *CARBON dioxide , *PRESSURE sensors , *FLAME - Abstract
With the industrial application of syngas, the explosion accident caused by it has gradually become a topic of concern for researchers. In this paper, the effects of CO 2 addition on the deflagration characteristics of syngas-air premixed mixtures were investigated through experiments and numerical simulations. Experiments were carried out inside a T-pipeline, using a high-speed camera and a pressure sensor to simultaneously record the flame evolution and pressure dynamics during deflagration. Simulations were calculated using the GRI 3.0 mechanism by Chemkin Premix Code. The results show that the addition of CO 2 has a certain inhibitory effect on the flame propagation, which can make the finger flame in the vertical pipe evolve into a "tulip" flame. And under the inhibition of CO 2 , the deflagration overpressure of the mixture is reduced, and the number of H, O, OH radicals is also greatly reduced, and the chemical reaction rate is correspondingly slowed down. [Display omitted] • The flame spreads symmetrically in the T-pipeline. • The addition of CO 2 can inhibit the flame propagation in the T-pipeline. • The more CO 2 added, the lower the T-pipeline explosion overpressure. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
28. Constructing rod-shaped Co2C/MoN as efficient bifunctional electrocatalyst towards overall urea-water electrolysis.
- Author
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Zhang, Lingye, Wang, Yingxi, Cao, Jie, Zhang, Rui, Wang, Feng, and Wu, Huimin
- Subjects
- *
FOAM , *OXYGEN evolution reactions , *HYDROGEN evolution reactions , *ELECTROLYSIS , *CARBON dioxide , *HYDROGEN production - Abstract
In this paper, Co 2 C/MoN/NF at different calcination temperatures (T = 500, 550, 600, 650, 700 °C) was prepared in situ on 3D foam nickel (NF) by hydrothermal treatment and high-temperature calcination. The experimental results show that the sample synthesized at 600 °C (Co 2 C/MoN-600/NF) has the best catalytic capacity and the maximum electrochemical active area. For the hydrogen evolution reaction (HER), the potential is only −176 mV at 100 mA cm−2, meanwhile, only 1.42 V is needed for urea oxidation reaction (UOR). Furthermore, a two-electrode electrolyze cell of Co 2 C/MoN-600/NF‖Co 2 C/MoN-600/NF was constructed. And the voltage required for overall urea splitting (OUS) is 1.507 V at 50 mA cm−2, which is 171 mV lower than that of overall water splitting (OWS, 1.678 V). Moreover, the prepared catalyst not only can treat urea in wastewater but also catalyze the production of hydrogen. Therefore, it will be a promising green electrocatalyst. [Display omitted] • Co 2 C/MoN / NF was synthesized at different calcination temperatures for producing hydrogen energy. • Co 2 C/MoN / NF exhibited efficient bifunctional electrocatalyst towards HER and UOR. • Compared with pure water splitting, the efficiency of the catalyst is higher with the aid of urea. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
29. Glycine-assisted preparation of highly dispersed Ni/SiO2 catalyst for low-temperature dry reforming of methane.
- Author
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Yang, Jiliang, Lu, Xinkang, Han, Cui, Liu, Hui, Gong, Dandan, Mo, Liuye, Wei, Qinhong, Tao, Hengcong, Cui, Sha, and Wang, Luhui
- Subjects
- *
CATALYSTS , *METHANATION , *METHANE , *GLYCINE receptors , *CARBON dioxide , *LOW temperatures , *HIGH temperatures - Abstract
Ni-based catalysts have been widely studied in reforming methane with carbon dioxide. However, Ni-based catalysts tends to form carbon deposition at low temperatures (≤600 °C), compared with high temperatures. In this paper, a series of Ni/SiO 2 -XG catalysts were prepared by the glycine-assisted incipient wetness impregnation method, in which X means the molar ratio of glycine to nitrate. XRD, H 2 -TPR, TEM and XPS results confirmed that the addition of glycine can increase Ni dispersion and enhance the metal-support interaction. When X ≥ 0.3, these catalysts have strong metal-support interaction and small Ni particle size. The Ni/SiO 2 -0.7G catalyst has the best catalytic performance in dry reforming of methane (DRM) test at 600 °C, and its CH 4 conversion is 3.7 times that of Ni/SiO 2 -0G catalyst. After 20 h reaction under high GHSV (6 × 105 ml/g cat /h), the carbon deposition of Ni/SiO 2 -0.7G catalyst is obviously lower than that of Ni/SiO 2 -0G catalyst. Glycine-assisted impregnation method can enhance the metal-support interaction and decrease the metal particle size,which is a method to prepare highly dispersed and stable Ni-based catalyst. [Display omitted] • Highly dispersed Ni/SiO 2 -XG catalysts were prepared by glycine-assisted impregnation. • The Ni/SiO 2 -0.7G shows high activity and coke resistance during low-temperature DRM. • Excellent activity and coke resistance is due to the high Ni dispersion. • Highly dispersed Ni was stable due to the strong metal-support interaction. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
30. Comparative analyses of a novel solar tower assisted multi-generation system with re-compression CO2 power cycle, thermoelectric generator, and hydrogen production unit.
- Author
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Khanmohammadi, Shoaib, Kizilkan, Onder, and Musharavati, Farayi
- Subjects
- *
HYDROGEN production , *THERMOELECTRIC generators , *SUPERCRITICAL carbon dioxide , *INTERSTITIAL hydrogen generation , *REMANUFACTURING , *WASTE recycling , *SOLAR power plants , *CARBON dioxide - Abstract
In the present paper, a new energy generation system is suggested for multiple outputs, including a hydrogen generation unit. The plant is powered by a solar tower and involves six different subsystems; supercritical carbon dioxide (sCO 2) re-compression Brayton cycle, ammonia-water absorption refrigeration cycle, hydrogen generation, steam generation, drying process, and thermoelectric generator. The thermodynamic assessment of the multi-generation system is carried out for three different cities from Turkey, Iran, and Qatar. The energy and exergy efficiencies are calculated for base conditions to compare the different locations. The operating output parameters for the suggested system and simple re-compression Brayton system are compared. A parametric analysis is also done for investigating the influences of different system variables on plant performance. According to the results, Doha city is found to be more effective due to its geographical conditions. Moreover, based on the comparative study, the proposed cycles produce more power than the basic re-compression cycle with 64.59 kW, 47.33 kW, and 52.25 kW for Doha, Isparta, and Tehran, respectively. Additionally, the analyses revealed that in the term of energy efficiency, the suggested system has 32.29%, 32.28%, and 32.29% better performance than the simple cycle, and in terms of exergy efficiency, it has 4%, 4.8%, and 5% better performance than the simple cycle in Doha, Isparta, and Tehran, respectively. • A new integrated energy system with maximum waste recovery introduced. • Three different cities in Turkey, Iran and Qatar were select for system analysis. • The average annual rate of hydrogen production for Doha is 6.48 kg/h. • Suggested system in Isparta has 2070 kW more exergy destruction than basic system. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
31. Supercritical water gasification of oil-containing wastewater with a homogeneous catalyst: Detailed reaction kinetic study.
- Author
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Xu, Jialing, Cheng, Zening, Ren, Changsheng, Yi, Lei, Wei, Wenwen, Jin, Hui, and Guo, Liejin
- Subjects
- *
SUPERCRITICAL water , *WATER-gas , *SEWAGE , *WASTEWATER treatment , *HYDROGEN production , *CATALYSTS , *CARBON dioxide - Abstract
Supercritical water gasification (SCWG) is a promising technology for oil-containing wastewater treatment. This paper aims to establish a reaction kinetic model to provide better guidance for optimal industrial reactor design. The model is developed based on the experimental results obtained from K 2 CO 3 -catalyzed SCWG of diesel (the model compound of oil containment in wastewater) at various conditions of 500–650 °C and 15.23–64.45 s. Then the model validation by using the experimental data from other conditions. The validation results showed that the kinetic model can predict the gas concentration with an acceptable deviation. Afterward, the indicators of carbon gasification efficiency and gas yield versus residence time are predicted. The results show that the required residence time for the complete gasification is varied from 214.2 to 2150.8 s when the temperature changes from 500 to 650 °C. Moreover, the reaction rate analysis result indicates that the two reactions contributed most to the hydrogen production are the forward water-gas shift and the reverse CO methanation reaction. Additionally, the sensitivity analysis result reveals that the hydrolysis reaction of diesel has a significant influence at the initial stage, while the CO and CO 2 methane reactions play a vital role at the late stage for gas production. [Display omitted] • A kinetic model with 13 reactions of SCWG of oil-containing wastewater is developed. • Residence time of 239.2 s for complete gasification under 650 °C is predicted. • Reaction rates for gases production and consumption are analyzed. • The hydrolysis reaction of diesel has a significant influence at the initial stage. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
32. Different performance and mechanisms of CO2 electrolysis with CO and H2 as protective gases in solid oxide electrolysis cell.
- Author
-
Liang, Jingjing and Han, Minfang
- Subjects
- *
ELECTROLYSIS , *ELECTROLYTIC reduction , *CARBON dioxide , *CARBON offsetting , *GASES , *YTTRIA stabilized zirconium oxide - Abstract
The significance of converting CO 2 into valuable feedstock is highly emphasized with the carbon neutrality vision. Generally, CO and H 2 are usually applied as the protective gases during CO 2 electrolysis in nickel based Solid Oxide Electrolysis Cell (SOEC). In this paper, the effects of H 2 and CO as protective gases on the performance of a Ni-YSZ (yttria stabilization zirconia) based SOEC are studied. The electrode processes of the cell are investigated by the electrochemical impedance spectroscopy (EIS) and calculated distribution of relaxation times (DRT) results. The results show that CO makes little difference on the performance of the cell while the cell shows a superior performance with H 2 as protective gas, indicating different mechanisms behind. The distinct discrepancies in characteristic frequency ranges of electrode processes with the CO 2 –CO and CO 2 –H 2 mixtures show that the replacement of CO by H 2 changes the reduction pathway of CO 2 from electrochemical reduction to thermochemical reduction, and only steam is electrolyzed. However, the direct injection of steam deteriorates slightly the performance of SOEC. The effect of reverse water gas shift (RWGS) reaction on the electrochemical performance of SOEC is explored and its effect of delaying the concentration polarization and extending the limiting current density is confirmed. Furthermore, the unique pattern of flattened j-V curve at high applied current of CO 2 electrolysis is repeatedly emphasized. • The performance of SOEC with H 2 as protective gas was superior compared to that with CO. • The existence of H 2 changed the reduction pathway of CO 2 from electrochemical reduction to thermochemical one. • The effect of RWGS reaction of extending the limiting current density was proved. • The unique pattern of flattened j-V curve at higher applied current of exclusive CO 2 electrolysis was emphasized. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
33. NO mechanisms of syngas MILD combustion diluted with N2, CO2, and H2O.
- Author
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Shi, Guodong, Li, Pengfei, Hu, Fan, and Liu, Zhaohui
- Subjects
- *
COMBUSTION , *ATMOSPHERIC pressure , *STRAIN rate , *CARBON dioxide , *NITROGEN , *SYNTHESIS gas , *GAMMA ray bursts - Abstract
The NO mechanism under the moderate or intense low-oxygen dilution (MILD) combustion of syngas has not been systematically examined. This paper investigates the NO mechanism in the syngas MILD regime under the dilution of N 2 , CO 2 , and H 2 O through counterflow combustion simulation. The syngas reaction mechanism and the counterflow combustion simulation are comprehensively validated under different CO/H 2 ratios and strain rates. The effects of oxygen volume fraction, CO/H 2 ratio, pressure, strain rate, and dilution atmosphere are systematically investigated. For all the MILD cases, the contribution of the prompt and NO-reburning routes to the overall NO emission is less than 0.1% due to the lack of CH 4 in fuel. At atmospheric pressure, the thermal route only accounts for less than 20% of the total NO emission because of the low reaction temperature. Moreover, at atmospheric pressure, the contribution of the NNH route to NO emission is always larger than 55% in the N 2 atmosphere. The N 2 O-intermediate route is enhanced in CO 2 and H 2 O atmospheres due to the increased third-body effects of CO 2 and H 2 O through the reaction N 2 + O (+M) ↔ N 2 O (+M). Especially in the H 2 O atmosphere, the N 2 O-intermediate route contributes to 60% NO at most. NO production is reduced with increasing CO/H 2 ratio or pressure, mainly due to decreased NO formation from the NNH route. Importantly, a high reaction temperature and low NO emission are simultaneously achieved at high pressure. To minimize NO emission, the reactions should be operated at high values of CO/H 2 ratios (i.e., >4) and pressures (e.g., P > 10 atm), low oxygen volume fractions (e.g., X O2 < 15%), and using H 2 O as a diluent. This study provides a new fundamental understanding of the NO mechanism of syngas MILD combustion in N 2 , CO 2 , and H 2 O atmospheres. • The NNH route dominates NO formation in N 2 atmosphere under atmospheric pressure. • The N 2 O-intermediate route is enhanced in CO 2 and H 2 O atmospheres. • Increasing CO/H 2 ratio reduces NO formation from NNH and N 2 O-intermediate routes. • High pressure increases the combustion temperature while inhibits the NO formation. • The prompt and NO-reburning routes are negligible due to the absence of CH 4. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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34. Validation challenges in solid oxide electrolysis cell modeling fueled by low Steam/CO2 ratio.
- Author
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Kazempoor, P., Asadi, J., and Braun, R.J.
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WATER gas shift reactions , *ELECTROLYTIC reduction , *ELECTROLYSIS , *CARBON dioxide , *STEAM flow , *FUEL cells , *WATER supply - Abstract
This study addresses some of the challenges in the modeling of solid oxide electrolysis cells (SOECs), particularly for feed gases containing low inlet steam-to-CO 2 concentration ratios. The common approach used for SOEC modeling is to neglect the CO 2 electrochemical reduction reaction. A comprehensive model validation versus experimental results presented by the Idaho National Laboratory (INL) is performed in this paper. Our validation results under various operating conditions show that the model deviation with experimental data increases above certain current densities, e.g., 1200 Am−2. It can also be seen that the electrochemical reaction involving CO 2 can only be neglected when the steam flow supplied to the cell is high enough to support the water-gas shift reaction. Suppose the concentration of inlet water supply is not enough to support the reverse water gas shift reaction. In that case, the electrochemical reduction of CO 2 has to be considered to avoid model-predictive results that are far from available experimental observations. • Solid oxide electrolysis cells modeling Challenges at low inlet steam-to-CO 2 concentration ratios are presented. • CO 2 Electrochemical reaction is negligible when the inlet steam flow is high to support the water-gas shift reaction. • Numerical results can be far from experimental depending on the fuel composition and inlet steam into a cell. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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35. Highly dispersed mesoporous Cu/γ-Al2O3 catalyst for RWGS reaction.
- Author
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Ai, Xin, Xie, Hongmei, Chen, Shengming, Zhang, Guizhi, Xu, Benjing, and Zhou, Guilin
- Subjects
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CATALYSTS , *WATER gas shift reactions , *PORE size distribution , *CARBON dioxide , *CARBON emissions , *GRINDING & polishing , *FOSSIL fuels - Abstract
The extensive use of fossil energy leads to the wanton emission of CO 2 and serious environmental problems. The resource utilization of CO 2 is an effective way to solve this problem. The key of CO 2 resource utilization is the design and preparation of high active CO 2 hydrogenation catalyst. In this paper, supported Cu/γ-Al 2 O 3 catalysts were prepared by wet impregnation and grinding methods, respectively. The physicochemical properties of the prepared Cu/γ-Al 2 O 3 catalysts were characterized by XRD, BET, CO 2 -TPD and Quasi in-situ XPS, and the reducibility of the precursors was studied by H 2 -TPR. The results show that Cu content directly affects the Cu0 species crystallinity and even affects the adsorption and activation of CO 2 molecules for the Cu/γ-Al 2 O 3 catalyst. The dispersion of Cu0 species in the prepared Cu/γ-Al 2 O 3 catalysts can be further improved by grinding method. The CO 2 reaction rate on the Cu/γ-Al 2 O 3 catalyst prepared by grinding method can be significantly increased to 2.12 × 10−5 mol/g cat /s at 400 °C. The supported Cu/γ-Al 2 O 3 catalysts can be prepared by the wet impregnation and grinding method. The highly dispersed Cu0 species are the active component for CO 2 RWGS reaction. The Cu content and preparation method can change the specific surface area, pore size distribution of the Cu/γ-Al 2 O 3 catalysts and reducibility of the CuO/γ-Al 2 O 3 precursors, which directly affects the Cu0 species dispersion and crystallinity on the Cu/γ-Al 2 O 3 catalyst. The dispersion of Cu0 species in the prepared Cu/γ-Al 2 O 3 catalysts can be further improved by grinding method, which is conducive to the formation of active sites for CO 2 hydrogenation. The Cu/γ-Al 2 O 3 catalyst prepared by grinding method has large specific surface area and suitable CO 2 adsorption capacity, which can prominently improve the CO 2 hydrogenation performances. [Display omitted] • Cu content can regulate the dispersion and crystallinity of Cu0 species. • Grinding method can enhance the surface Cu0 species content and dispersion. • Cu0 species with low crystallinity can promote the exposure of CO 2 hydrogenation active sites. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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36. Technical, economic, and environmental analyses of the modernization of a chamber furnace operating on natural gas or hydrogen.
- Author
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Gołdasz, Andrzej, Matuszewska, Dominika, and Olczak, Piotr
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CARBON emissions , *NATURAL gas , *FURNACES , *NET present value , *HYDROGEN , *COMBUSTION gases , *ENERGY consumption , *HYDROGEN as fuel - Abstract
The paper presents a technical, economic and environmental analyses of a chamber furnace used to heat the charge before forging. The energy efficiency of the furnace before the modernization was 18%, after the modernization it was 31% (partial modernization due to large financial outlays). Other variants were also analysed: complete modernization, the variant of furnace modernization with 30% hydrogen content in the gas and the variant with 100% hydrogen as fuel. The analyses showed that with the current gas price (0.025 EUR/kWh) and the price of emission allowances (nearly 60 EUR/MgCO 2) and 100 cycles/year, the difference in Net Present Value (NPV) before base variant and partial modernization is around 900,000 EUR and before base variant and full modernization is 1,200,000 EUR. The introduction of the gas and 30% of hydrogen co-combustion option versus the base scenario option for 150 cycles per year results in a NPV difference of at least 2 million EUR. The option of 100% hydrogen as a fuel is the most advantageous from the point of view of reducing CO 2 emissions - it is largely influenced by the rising prices of CO 2 emission allowances. • Effects of the modernization of a chamber furnace. • Net Present Value and CO 2 emission reductions during the lifetime of a chamber furnace are calculated. • The study provides maps to compare the economic efficiency (natural gas, hydrogen, and mix). [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
37. Development of an SFMM/CGO composite electrode with stable electrochemical performance at different oxygen partial pressures.
- Author
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Alizad Farzin, Yousef, Babaei, Alireza, Løye Skafte, Theis, Stamate, Eugen, Ataie, Abolghasem, and Jensen, Søren Højgaard
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- *
PARTIAL pressure , *ELECTROCHEMICAL electrodes , *CONDUCTIVITY of electrolytes , *IONIC conductivity , *CARBON dioxide , *COMPOSITE construction - Abstract
This paper carefully evaluates the electrocatalytic activity of Sr 2 FeMo 0.5 Mn 0.5 O 6 (SFMM) double perovskite as a candidate to substitute the state-of-the-art Ni/YSZ fuel electrode. The electrochemical performance of a 40% SFMM/CGO composite electrode was studied in CO/CO 2 and H 2 with different oxygen partial pressure. Two different cell configurations are prepared at a relatively low temperature of 800 °C to increase the electrochemically active surface area. The cell was supported with a 150 μm 10Sc1CeSZ electrolyte in the first configuration. The cell in the second configuration was made by applying a 400 nm thin 8YSZ layer on 150 μm CGO electrolyte to improve the electrolyte ionic conductivity. Improving catalytic activity with increasing oxygen partial pressure is a key characteristic of the developed electrode. The polarization resistance of about 0.34 and 0.56 Ω cm2 at 750 °C in 3%H 2 O + H 2 and 60% CO/CO 2 makes this electrode a promising candidate for SOCs application. • A crack-free SFMM/CGO composite fuel electrode prepared at 800 °C without the formation of the SrZrO 3 insulator phase. • The SFMM double perovskite shows a stable structure at high oxygen partial pressure. • The electrochemical behavior obtained in CO/CO 2 and H 2 with 3–20 vol% H 2 O. • The relatively small polarization resistance makes it a candidate for substitution of the state-of-art Ni/YSZ electrode. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
38. Modelling the performance of an SOEC by optimization of neural network with MPSO algorithm.
- Author
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Han, Jing, Wang, Xi, Yan, Limei, and Dahlak, Aida
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HYDROGEN economy , *PARTICLE swarm optimization , *GAS mixtures , *CARBON dioxide , *ENERGY consumption , *HYDROGEN as fuel - Abstract
This paper studies the Solid Oxide Electrolyzer Cell as a promising system in the sustainable development for the hydrogen economy and energy systems as a robust system. The Solid Oxide Electrolyzer Cell converts the steam and carbon-dioxide directly to functional fuels through consumption of the additional electrical power of green power sources or off-peak network powers. The present paper evaluates the static efficiency of the SOEC under four various gas mixtures. Modeling of this system is performed using Elman neural network (ENN) and modified particle swarm optimization (MPSO) algorithm. The MPSO algorithm is utilized to determine the optimal values for ENN adjustable parameters. It's known from the empirical results that the steam and carbon-dioxide concentrations can affect the SOEC efficiency. The operational potential and volume share of the hydrogen, carbon dioxide and steam are considered as the system inputs, and efficiency (current) is remarked as its output. The correlation factors of the achieved model are greater than 0.999, and its MSE (mean squared error) is lower than 0.017. It reveals that the forecasted values are almost equal to the empirical data. Subsequently, the efficiency of the SOEC is studied using the achieved model of the MPSO-based ENN in various feedstock concentrations. Thus, this dataset that is used for ENN model can be desirable for different applications of fast-modeling in a standalone group. It as well can be useful for cost, computing-time, and computing burden reduction in a model construction in the efficiency analyzing and system-level designing processes. • The static model of a SOEC is identified in this paper. • Elman neural network is applied in this paper as a novel method in the modeling process. • MPSO algorithm is used to increase the accuracy of the obtained model. • Static efficiency of the SOEC is evaluated for various gas mixtures. • The obtained results demonstrated the high precision of the proposed model. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. Gasification of horse dung in supercritical water.
- Author
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Xie, Yi, Zheng, Xinliang, and Gao, Weijun
- Subjects
- *
MANURES , *SUPERCRITICAL water , *HORSES , *CATALYSIS , *CATALYTIC activity , *CARBON dioxide - Abstract
Horse dung naturally contains phosphorus and nitrogen which affect the environment negatively, if the nutrients are not recovered and utilized. In this paper, the influence of alkali on the gasification of horse dung at 560 °C, 25 MPa was investigated. The results show that LiOH addition increased H 2 fraction and the gas yield. The precipitated alkali in the reactor still showed high catalytic effect on the subsequent gasification of horse dung without further adding the alkali. A novel 4-lump kinetic model for horse dung in SCWG including feedstock, CH 4 , CO, and CO 2 lumps is proposed. • Supercritical water gasification is applied to treat horse dung. • The catalytic activity was slightly reduced owning to the transformation of LiOH to Li 2 CO 3 and LiHCO 3. • The catalytic action of LiOH is studied. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
40. Highly efficient photocatalytic conversion of gas phase CO2 by TiO2 nanotube array sensitized with CdS/ZnS quantum dots under visible light.
- Author
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Cheng, Min, Bai, Shuxia, Xia, Yanze, Zhu, Xun, Chen, Rong, and Liao, Qiang
- Subjects
- *
QUANTUM dots , *VISIBLE spectra , *FIELD emission electron microscopes , *CATALYSTS , *CARBON dioxide , *TRANSMISSION electron microscopes , *ELECTRON-hole recombination - Abstract
With the massive consumption of fossil fuels, energy crisis and effectively reducing CO 2 to curb global warming have become urgent and severe problems in the world. Photocatalytic conversion of CO 2 technology which can convert CO 2 into combustible compounds by using solar energy can solve both of the problems mentioned above. However, the photocatalytic conversion of CO 2 exhibits too low efficiency, especially under visible light. So, in order to improve the photocatalytic efficiency, the composite photocatalysts of TiO 2 nanotube array (TNTA) sensitized by CdS/ZnS quantum dots (QDs) were successfully prepared by anodization method and successive ionic layer adsorption and reaction (SILAR) method in this work. And the composite photocatalysts exhibited a high performance for photocatalytic conversion of gas-phase CO 2 to methanol under visible light. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and X-ray photoelectric spectroscopy (XPS) were employed to characterize the ingredients and morphologies of the synthesized photocatalysts. And, UV–vis diffuse reflectance spectra (UV–Vis DRS) revealed that CdS/ZnS QDs enhanced the photo-absorption of composite photocatalyst in the visible light region. The main product methanol yield of CdS/ZnS-TNTA under visible light was 2.73 times that of bare TNTA when TNTA was treated by 10 SILAR cycles. Meanwhile, the product yield first increased before decreasing with the increase of the CO 2 flow rate. And the greatest product yield reached up to 255.49 nmol/(cm2-cat·h) with the increase of light intensity. The reaction mechanism was discussed in this paper. This high performance for photocatalytic reduction of CO 2 was primarily attributed to the CdS/ZnS QDs sensitization, which widens the response wavelength range of the catalyst to include visible light and partly inhibits the recombination of electron-hole pairs. [Display omitted] • TiO 2 nanotube array sensitized by CdS/ZnS was used for photoreduction of CO 2. • The best methanol yield reached 255.49 nmol/(cm2 cat ·h) under visible light. • Effects of CdS/ZnS contents, flow rates and light intensities were investigated. • The yield of CdS/ZnS-TNTA was 2.73 times that of bare TNTA. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
41. A review of the effects of hydrogen, carbon dioxide, and water vapor addition on soot formation in hydrocarbon flames.
- Author
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Wang, Yang, Gu, Mingyan, Zhu, Yuhan, Cao, Ling, Zhu, Bencheng, Wu, Jiajia, Lin, Yuyu, and Huang, Xiangyong
- Subjects
- *
SOOT , *WATER vapor , *CARBON dioxide , *FLAME , *FOSSIL fuels , *HYDROGEN flames - Abstract
Addition of reactive or inert substances is one of the most effective and practical ways to control soot formation in combustion of hydrocarbon fuels. In this paper, the research progress on the effects of hydrogen, carbon dioxide, and water vapor addition on soot formation in hydrocarbon flames in the last few decades is systematically summarized. The summary shows that the number of studies on the effects of these three common diluents has increased dramatically in the last five years. Although the overall effects of all these three common diluents suppress soot formation, there is inconsistency with regard to the role of their chemical effects. The chemical effect of hydrogen (CE-H 2) mainly acts on the soot nucleation process, followed by the soot surface growth and finally the soot oxidation process. CE-H 2 seems significantly affected by the fuel type, oxygen concentration, and the ambient pressure. The chemical effect of carbon dioxide (CE-CO 2) affects soot formation indirectly mainly through the reaction CO + OH ↔ CO 2 + H. Some studies believe that CE-CO 2 suppresses soot production by increasing the hydroxyl radical (OH) concentration, while other studies believe that it is primarily attributed to the decrease of the hydrogen radical (H) concentration. The reaction H 2 O + H ↔ H 2 + OH plays a vital role in the chemical effect of water vapor (CE-H 2 O) addition on inhibiting soot formation. Most studies support the view that the chemical effect of water vapor mainly increases the OH concentration and suppresses soot formation by weakening the soot nucleation process. Moreover, we believe that reaction H 2 O + O ↔ OH + OH and phenylacetylene also play an essential effect on the CE-H 2 O. • A review of the effect of H 2 addition on soot formation in hydrocarbon flames. • A review of the effect of CO 2 addition on soot formation in hydrocarbon flames. • A review of the effect of H 2 O addition on soot formation in hydrocarbon flames. • Reaction H 2 O + O ↔ OH + OH and the CH 2 play an essential effect on the CE-H 2 O. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
42. Performance assessment of thermochemical CO2/H2O splitting in moving bed and fluidized bed reactors.
- Author
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Farooqui, Azharuddin, Angal, Prudwee, Shamim, Tariq, Santarelli, Massimo, and Mahinpey, Nader
- Subjects
- *
FLUIDIZED bed reactors , *MOVING bed reactors , *FLUIDIZED-bed combustion , *CARBON dioxide - Abstract
In this paper, we present the assessment of moving bed reactors and fluidized bed reactors operating in different fluidizing regimes for solar thermochemical redox cycles (STRC) for syngas production. The reduction reactor with a moving bed (MB RED) while the oxidation reactor (OXI) is either a moving bed reactor (MB OXI) or bubbling bed (BB OXI) yields higher performance. It was observed that only water splitting is suitable at 1400 °C and 10−3 bar reduction conditions. The higher reduction temperature and pressure improved the efficiency of the CO 2 /H 2 O splitting unit. The requirement of the H 2 /CO ratio drives the gas feed (CO 2 /H 2 O) into OXI. To achieve an H 2 /CO ratio of 1, MB OXI and BB OXI require an equimolar mixture of CO 2 and H 2 O at 1600 °C. However, to achieve a similar H 2 /CO ratio at a lower temperature of 1500 °C, the gas feed of the CO 2 /H 2 O ratio required is 3. A similar H 2 /CO ratio is achieved for OXI operating in a turbulent and fast fluidizing, but the selectivity is lower due to lower reaction rates. OXI as a transport bed is least suited based on solid conversion (X OXI), H 2 /CO, or efficiency. The results are useful in designing the redox reactors for syngas. • Moving bed and fluidized bed regimes are investigated for CO 2 /H 2 O splitting. • Bubbling regimes yield similar selectivity of moving bed but require 4 reactors. • CO 2 /H 2 O: 0.75/0.25 is suitable for the H 2 /CO ratio ~1.0 for 1600 °C and 10-7 bar. • For T RED and P RED of 1400 °C and 10-3 bar the only H 2 O splitting is suitable. • The CL efficiency was highest for moving bed reactors for reduction and oxidation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
43. Enhanced activity of Co catalysts supported on tungsten carbide-activated carbon for CO2 reforming of CH4 to produce syngas.
- Author
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Li, Sheng, Zhang, Guojie, Wang, Jiming, Liu, Jun, and Lv, Yongkang
- Subjects
- *
CATALYST supports , *TUNGSTEN catalysts , *STEAM reforming , *ACTIVATED carbon , *SYNTHESIS gas , *CARBON dioxide , *FISCHER-Tropsch process , *CARBON - Abstract
Carbon materials are widely used as catalysts or supports due to their excellent properties. In this paper, the tungsten carbide-activated carbon (WC-AC) composite support was successfully prepared by in-situ carburizing on AC matrix, which is characterized by the covalent anchoring of WC on the AC support. The active metal Co was supported on WC-AC for dry reforming of methane (DRM). Samples were analyzed by N 2 physisorption measurements, XRD, XPS, H 2 -TPR, H 2 -TPD, CH 4 &CO 2 -TPSR, TG-DTG. The WC-AC stabilizes the disturbance of C in AC, alleviates the gasification effect of CO 2 and increases the active sites for CH 4 cracking. Moreover, WC provides a resistance-less bridge suitable for the Co3+ → Co2+, resulting in a high Co2+/Co3+ ratio on the catalyst surface. This enhances the interaction between the Co species and the WC-AC, thereby enhancing the CH 4 activation. In the process of WC-AC promoting Co3+→Co2+, the catalyst surface is accompanied by the generation of oxygen vacancies. This can enhance the dissociative adsorption of CO 2 on surface of the WC-cobalt oxide, and at the same time increase the relative proportion of adsorbed oxygen on the catalyst surface, thereby effectively inhibiting the formation of coke. However, the small amount of graphitic carbon generated due to the strong coupling of WC and Co is the main reason for deactivation of Co/WC-AC. [Display omitted] • WC-AC was prepared by in situ carburization of ammonium metatungstate on AC matrix. • WC-AC enhances the stability of C in the AC matrix and adds CH 4 active sites. • WC-AC favors the transformation of Co3+ to Co2+ to enhance CH 4 cracking. • Surface chemisorption oxygen can be enriched in Co/WC-AC to activate CO 2. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
44. Supercritical water gasification mechanism of polymer-containing oily sludge.
- Author
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Peng, Pai, Guo, Shenghui, Li, Linhu, Jin, Hui, Ge, Zhiwei, and Guo, Liejin
- Subjects
- *
SUPERCRITICAL water , *POLYCYCLIC aromatic hydrocarbons , *OFFSHORE oil & gas industry , *BATCH reactors , *ORGANIC compounds , *CARBON dioxide - Abstract
In the offshore petroleum industry, polymer-containing oily sludge (PCOS) hinders oil extraction and causes tremendous hazards to the marine ecological environment. In this paper, an effective pretreatment method is proposed to break the adhesive structure of PCOS, and the experiments of supercritical water gasification are carried out under the influencing factors including residence time (5–30 min) and temperature (400–750 °C) in batch reactors. The increase of time and temperature all show great promoting effects on gas production. Polycyclic aromatic hydrocarbons, including naphthalene and phenanthrene, are considered as the main obstacles for a complete gasification. Carbon gasification efficiency (CE) reaches maximum of 95.82% at 750 °C, 23 MPa for 30 min, while naphthalene makes up 70% of the organic compounds in residual liquid products. The highest hydrogen yield of 19.79 (mol H 2 /kg of PCOS) is observed in 750 °C for 25 min. A simplified reaction pathway is presented to describe the gaseous products (H 2 , CO, CO 2 , CH 4). Two intermediates are defined for describing the reaction process bases on the exhaustive study on organic matters in residual liquid products. The results show that the calculated data and the experimental data have a high degree of fit and tar formation reaction is finished within 10 min. [Display omitted] • Utilization of polymer-containing oily sludge via supercritical water gasification. • Optimal gasification condition is obtained. • Reaction mechanism of gasification is discussed. • Tar formation reaction can be finished within 10 min in quartz tubes. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
45. Syngas production from ethanol dry reforming using Cu-based perovskite catalysts promoted with rare earth metals.
- Author
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Ramkiran, Attili, Vo, Dai-Viet N., and Mahmud, Mohd Sabri
- Subjects
- *
STEAM reforming , *RARE earth metal catalysts , *ETHANOL , *SYNTHESIS gas , *CITRATES , *CARBON monoxide , *TUBULAR reactors , *CARBON dioxide - Abstract
This paper reports about the production of syngas from dry reforming of ethanol (EDR) upon LaCuO 3 and CeCuO 3 catalysts that were prepared by using citrate sol-gel method. EDRs were run with fresh catalyst at each varied variable and 42 L/g cat /h of feed in a tubular reactor under atmospheric pressure. At equal feed pressure of reactants, steady state CO 2 conversion increased exponentially from 700 to 800 °C while H 2 and CO yields were increasing differently in sigmoid trend rendering H 2 /CO ratios to drop linearly from 1.7 to 1.0. However, these reaction results except the latter are otherwise when ethanol-CO 2 ratio was increased (reducing CO 2 pressure) at 750 °C. A minimum H 2 /CO ratio was evidenced at the ethanol-CO 2 ratio of 1.48. LaCuO 3 catalyst was more superior in producing syngas owing to its relatively low reduction temperature, high surface area and crystallinity, many active sites, good surface morphology and many C –O, C –H and hydroxyl groups. • Characterization of LaCuO 3 and CeCuO 3 catalysts prepared by using the sol-gel method. • Yield of hydrogen and CO from catalytic ethanol dry reforming at different reaction temperatures and feed ratios. • The ratio of hydrogen to carbon monoxide as syngas product from the ethanol dry reforming reaction. • Relation between characterization results and the reaction results. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
46. Multi carrier energy systems and energy hubs: Comprehensive review, survey and recommendations.
- Author
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Aljabery, Ahmad Abdallah Mohammad, Mehrjerdi, Hasan, Mahdavi, Sajad, and Hemmati, Reza
- Subjects
- *
ENERGY storage , *POLLUTION , *CARBON dioxide , *MATHEMATICAL models , *COOLING , *HOT carriers , *NATURAL gas - Abstract
In this paper, the multi carrier energy (MCE) systems are reviewed from different point of views including mathematical models, integrated components and technologies, uncertainty management, planning objectives, environmental pollution, resilience, and robustness. The basic of MCE systems is formed by combination of cooling, heating and power (CCHP). The natural gas and electricity are the main inputs to MCE systems and the cooling, heating, and electricity are the common outputs. The regular energy converters in the MCE systems are combined heat and power (CHP), gas boiler, absorption-electrical chillers, power to gas (P2G) and fuel-cell. The generic energy storages are electrical, heating, cooling, hydrogen, carbon dioxide (CO 2) and hydro systems. • Reviewing the design methods and topologies of multi carrier energy systems. • Studying the mathematical models of multi carrier energy systems and energy hubs. • Aspects of energy hubs: pollution, cost, resilience, robustness, flexibility. • Studying the input-output energies in multi carrier energy systems. • Reviewing the energy converters and storage units in multi carrier energy systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
47. Coke resistance of Ni-based catalysts enhanced by cold plasma treatment for CH4–CO2 reforming: Review.
- Author
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Xu, Junqiang, Xia, Pan, Zhang, Qiang, Guo, Fang, Xia, Yong, and Tian, Huan
- Subjects
- *
LOW temperature plasmas , *CATALYSTS , *ATMOSPHERIC methane , *GREENHOUSE gases , *COAL carbonization , *CARBON dioxide , *TRAVERTINE , *NICKEL catalysts - Abstract
Carbon dioxide reforming of methane can reduce emissions of greenhouse gases, and has been extensively studied. The conventional Ni-based catalysts easily coke, sinter, and deactivate in the CRM reaction. The studies suggested that the cold plasma treatment can improve the structure of Ni-based catalysts, and so enhance coke resistance of the catalysts. The review summarized the effect of cold plasma treatment on the coke resistance of Ni-based catalysts for the CRM reaction. The main goal of the paper was to illuminate: the structure change of catalysts treated by cold plasma, such as crystal planes of Ni particles, the particles size of Ni, the Ni dispersion, the metal-support interaction, and CO 2 absorption capacity; the correlation between plasma treatment conditions (treatment way and parameters) and coke resistance of the catalyst treated by cold plasma; and the mechanism of plasma treatment to improve the coke resistance of the catalysts. • The plasma treatment enhances the coke resistance of Ni-based catalysts. • The correlation between the structure and coke resistance after plasma treatment. • The effect of plasma treatment ways and parameters on the coke resistance. • The mechanism of plasma treatment to improve the coke resistance of catalysts. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
48. A review of CO2 sorbents for promoting hydrogen production in the sorption-enhanced steam reforming process.
- Author
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Wang, Yinxiang, Memon, Muhammad Zaki, Seelro, Majid Ali, Fu, Weng, Gao, Yuan, Dong, Yingchao, and Ji, Guozhao
- Subjects
- *
HYDROGEN production , *STEAM reforming , *SORBENTS , *ALKALI metals , *SORPTION techniques , *CERAMIC metals , *CARBON dioxide , *CARBON dioxide adsorption - Abstract
Sorption-enhanced-steam-reforming (SESR) is a thermochemical conversion technology that produces a high-purity hydrogen stream by utilizing in-situ removal of CO 2 with a sorbent. In this paper, the advantages and disadvantages of CaO based sorbents, alkali-metal based sorbents (Na 2 ZrO 3 , Li 2 ZrO 3 and Li 4 SiO 4), hydrotalcite based sorbents, bifunctional materials and sorbents prepared from wastes are briefly discussed, and the techniques to improve the sorption properties of these CO 2 sorbents are summarized. In the process of hydrogen production by sorption-enhanced-steam-reforming, the selection of suitable high-temperature CO 2 sorbent is the key to produce high purity hydrogen. Furthermore, the hydrogen-production performance of the above-mentioned sorbents in the SESR process is investigated and summarized. Finally, a future perspective and some suggestions regarding these five types of sorbents are put forward. • Ca-sorbents are suitable to enhance H 2 in high temperature reforming at 550–800 °C. • Alkali metal ceramics are generally used for H 2 yield between 550 and 600 °C. • The application of HTlc is limited to reforming reactions below 500 °C. • Bi-functional materials are used in SESR due of reduced mass transfer resistance. • Using waste to prepare CO 2 sorbents is a promising direction for future research. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
49. A framework for assessing economics of blue hydrogen production from steam methane reforming using carbon capture storage & utilisation.
- Author
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Ali Khan, Muhammad Haider, Daiyan, Rahman, Neal, Peter, Haque, Nawshad, MacGill, Iain, and Amal, Rose
- Subjects
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STEAM reforming , *CARBON sequestration , *CONSUMPTION (Economics) , *GEOLOGICAL carbon sequestration , *CARBON dioxide , *NATURAL gas , *NATURAL resources , *HYDROGEN production - Abstract
Hydrogen (H 2) generation using Steam Methane Reforming (SMR) is at present the most economical and preferred pathway for commercial H 2 generation. This process, however, emits a considerable amount of CO 2 , ultimately negating the benefit of using H 2 as a clean industrial feedstock and energy carrier. That has prompted growing interest in enabling CO 2 capture from SMR for either storage or utilisation and producing zero-emission "blue H 2 ". In this paper, we propose a spatial techno-economic framework for assessing blue hydrogen production SMR hubs with carbon capture, utilisation and storage (CCUS), using Australia as a case study. Australia offers a unique opportunity for developing such 'blue H 2 ' hubs given its extensive natural gas resources, availability of known carbon storage reservoirs and an ambitious government target to produce clean/zero-emission H 2 at the cost of A$2.7 kg H2 −1). On the other hand, Western Australia offers lower gas pricing and relatively lesser storage costs, which would lead to more economically favourable hydrogen production (
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- 2021
- Full Text
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50. Thermodynamic performance study of a new SOFC–CCHP system with diesel reforming by CLHG to produce hydrogen as fuel.
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Wang, Heng, Zhao, Hongbin, and Zhao, Zefeng
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SOLID oxide fuel cells , *DIESEL particulate filters , *WASTE heat , *POWER resources , *BURNUP (Nuclear chemistry) , *ENERGY consumption , *CARBON dioxide , *PROPANE as fuel - Abstract
In this paper, a combined cooling, heating and power system based on diesel-fueled chemical looping hydrogen generation and solid oxide fuel cell, and with CO 2 capture was established. The system can achieve efficient power generation while separating CO 2 without energy consumption, and effectively avoid the carbon deposition problem. Aspen software is used to simulate the process of the system, and FORTRAN program is used to calculate, through the thermodynamic analysis model, the unique performance change law of the new system using diesel is obtained, and thermodynamic analysis is performed on the system at last. The results show that the power efficiency of the new system is 54.1%, while the exergy efficiency and fuel energy saving ratio can reach 53%. At the same time, the influence of fuel flow and fuel utilization factor on the system performance does not continue to increase or decrease, and the system performance parameters will have a peak value with the change of pressure. The results not only provide a theoretical basis for the future construction of new diesel-fueled energy supply system, but also provide a new idea for the optimization scheme of energy-saving system and carbon recovery. • Propose a new type of SOFC–CCHP system with diesel reforming by CLHG to produce hydrogen as fuel. • The new system can avoid the carbon deposition and separate CO 2 without energy consumption. • Established the thermal analysis models obtaining the unique performance change law of the integrated system. [ABSTRACT FROM AUTHOR]
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- 2021
- Full Text
- View/download PDF
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