Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Ca2MnO4-layered perovskite modified by NaNO3 for chemical-looping oxidative dehydrogenation of ethane to ethylene
No full textChemical-looping oxidative dehydrogenation (CL-ODH) is a process designed for the conversion of alkanes into olefins through cyclic redox reactions, eliminating the need for gaseous O2. In this work, we investigated the use of Ca2MnO4-layered perovskites modified with NaNO3 dopants, serving as redox catalysts (also known as oxygen carriers), for the CL-ODH of ethane within a temperature range of 700 degrees C -780 degrees C. Our findings revealed that the incorporation of NaNO3 as a modifier significantly enhanced the selectivity for ethylene generation from Ca2MnO4. At 750 degrees C and a gas hourly space velocity of 1300 h-1, we achieved an ethane conversion up to 68.17%, accompanied by a corresponding ethylene yield of 57.39%. X-ray photoelectron spectroscopy analysis unveiled that the doping NaNO3 onto Ca2MnO4 not only played a role in reducing the oxidation state of Mn ions but also increased the lattice oxygen content of the redox catalyst. Furthermore, formation of NaNO3 shell on the surface of Ca2MnO4 led to a reduction in the concentration of manganese sites and modulated the oxygen-releasing behavior in a step-wise manner. This modulation contributed significantly to the enhanced selectivity for ethylene of the NaNO3-doped Ca2MnO4 catalyst. These findings provide compelling evidence for the potential of Ca2MnO4-layered perovskites as promising redox catalysts in the context of CL-ODH reactions. (c) 2024 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved
The 42307111Chongqing Natural Science Fund for Distinguished Young Scholars[CSTB2022NSCQ-JQX0003]
No full textA non-linear convex model based energy management strategy for dual-storage offshore wind system
No full text-Using hydrogen production as energy storage can realize large-scale storage and transportation of energy, which is conducive to flexible scheduling of offshore wind power resources. However, compared with the battery energy storage system, the energy management strategy (EMS) of the dual-storage offshore wind power system with hydrogen production is more complex and nonlinear due to the large number of state variables and control variables. In order to realize the EMS of the system to maximize the benefits and minimize the aging cost, a nonlinear convex model is first established, and then an iterative solution method combining convex programming (CP) and dynamic programming (DP) is proposed. Among them, CP solves the global optimization problem of power distribution, and DP determines the start and stop of the electrolyzer. Finally, the feasibility of the proposed method is verified by simulation analysis
Unveiling the role of lignin feature on bio-ethanol and xylose derived from poplar during combined alkali/ethanol synergistic pretreatment
No full textThis study adopted a mixed experimental research design to investigate the effects of alkali and alkali-catalyzed ethanol pretreatment of poplar wood under different NaOH loadings on the pretreatment liquid, pretreatment solids, and polysaccharide conversion, with a particular emphasis on the utility of the lignin for subsequent conversion. Specifically, NaOH catalyzed ethanol pretreatment at 10% NaOH loading resulted in the removal of more than 80% lignin with >80% carbohydrates remaining in the residual solids. Simultaneous saccharification fermentation of this pretreated residue resulted in 29.09 g/L (72.84%) and 14.86 g/L (69.26%) of ethanol and xylose, respectively, following a fermentation period of 72 h. Then, an integrated evaluation of the lignin characterization in raw and pretreated residues was carried out to emphasize their influence on ethanol and xylose yield by two-dimensional heteronuclear single quantum coherence (2D-HSQC) NMR and gel permeation chromatography (GPC) analysis. The results showed that most of the side-chain structures were oxidized and the aryl-ether bond was dissociated with the synergistic influence of NaOH and ethanol treatment, accompanied by low molecular weight lignin obtained in the solid fraction. Overall, NaOH catalyzed ethanol pretreatment offered a strategy for selective biomass fractionation into carbohydrates conversion and lignin valorization with a high yield
Dynamic geothermal resource assessment: Integrating reservoir simulation and Gaussian Kernel Density Estimation under geological uncertainties
No full textThis paper presents a dynamic geothermal resource assessment method that integrates reservoir simulation and Gaussian kernel density estimation (KDE). This approach addresses geological uncertainties by employing reservoir simulation techniques to model the fluid and heat flow under the condition of permeability heterogeneity. Incorporating probabilistic resource assessment through Gaussian KDE, the study quantifies uncertainties, estimating the probability density function (PDF) of ensemble results under conditions like thermal breakthrough thresholds, fixed reservoir lifespans, and target energy production. The demonstrations of assessment start with a simple homogeneous model. The results show that larger doublet well distances result in extended lifespan, higher final production well temperatures, and increased energy production. Brugge reservoir emphasizes the impact of heterogeneity and uncertainty on production outcomes, especially at smaller doublet well distances. Assessment of fluvial Egg model reveals that drilling in fluvial channels causes rapid thermal breakthrough. This result indicates that, to optimize reservoir performance, it is recommended to refrain from drilling doublet wells within high -permeability fluvial channels. Furthermore, it is worthy of mention that the Gaussian kernel is not always favored for KDE, particularly in scenarios involving nonGaussian distribution ensembles. The proposed method, which integrates reservoir simulation and Gaussian KDE, enhances understanding of geological uncertainties and the intricate nature of geothermal reservoirs, facilitating more reliable and accurate resource assessments
Benedict-Webb-Rubin-Starling Equation of State plus Hydrate Thermodynamic Theories: An Enhanced Prediction Method for CO<sub>2</sub> Solubility and CO<sub>2</sub> Hydrate Phase Equilibrium in Pure Water/NaCl Aqueous Solution System
No full textAccurately predicting the phase behavior and physical properties of carbon dioxide (CO2) in pure water/NaCl mixtures is crucial for the design and implementation of carbon capture, utilization, and storage (CCUS) technology. However, the prediction task is complicated by CO2 liquefaction, CO2 hydrate formation, multicomponent and multiphase coexistence, etc. In this study, an improved method that combines Benedict-Webb-Rubin-Starling equation of state (BWRS EOS) + hydrate thermodynamic theories was proposed to predict CO2 solubility and phase equilibrium conditions for a mixed system across various temperature and pressure conditions. By modifying the interaction coefficients in BWRS EOS and the Van der Waals-Platteeuw model, this new method is applicable to complex systems containing two liquid phases and a CO2 hydrate phase, and its high prediction accuracy was verified through a comparative evaluation with a large number of reported experimental data. Furthermore, based on the calculation results, the characteristics of CO2 solubility and the variation of phase equilibrium conditions of the mixture system were discussed. These findings highlight the influence of hydrates and NaCl on CO2 solubility characteristics and clearly demonstrate the hindrance of NaCl to the formation of CO2 hydrates. This study provides valuable insights and fundamental data for designing and implementing CCUS technology that contribute to addressing global climate change and environmental challenges
Porous carbon fabrication techniques: A review
No full textPorous carbons are multipurpose materials with substantial industrial applications characterized by their large surface areas and porosities. They have immense potential for multifarious applications due to their outstanding features. This review focuses on the pore-forming mechanisms of present fabrication techniques, considering how the reaction conditions affect the final properties of the synthesized porous carbon. The benefits and drawbacks of each fabrication technique are also discussed. We also summarized the application of porous carbons in numerous fields, highlighting their versatility. Finally, some prospective research suggestions for the future are considered
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