Energy & Fuels最新文献

Natural gas hydrate (NGH) is a promising clean energy source with abundant reserves. Unveiling the mechanisms controlling hydrate dissociation and finding chemical agents that promote hydrate dissociation are of great significance for achieving controllable exploitation of NGH. This study utilized molecular dynamics simulation to investigate the dissociation mechanism of hydrates under different gas saturation levels as well as the influence of poly-N-vinylcaprolactam (PVCap) on hydrate dissociation. The simulation results indicate that in the systems without PVCap, the release rate of methane molecules from the methane hydrate increases with the methane content in the initial liquid phase. The systems with different methane saturations undergo different hydrate dissociation stages. For the systems with PVCap, it was found that PVCap has a certain promoting effect on methane hydrate dissociation; the promotion effect decreased with the increase in methane content in the initial liquid phase. The mechanism by which PVCap on methane hydrate dissociation was proposed: PVCap can adsorb methane molecules, promoting the formation of nanobubbles, reducing methane concentration in the liquid phase, thereby increasing the driving force for methane hydrate dissociation, and promoting the dissociation of methane hydrates.

Underground Hydrogen Storage (UHS) in aquifers is a promising solution. Some aquifers contain natural fractures that enhance permeability, improving injection and recovery. However, these fractures may also intensify mixing and channeling, reducing overall storage efficiency and hydrogen purity. To address these challenges, designing suitable UHS scenarios is essential to minimize hydrogen mixing and uneven distribution within the aquifer. Numerical simulations help optimize UHS operations, yet their high computational cost necessitates efficient alternatives. This study develops a grid-based proxy model using U-Net and Modified U-Net architectures to predict mixing maps and fluid flow dynamics without solving complex physical equations. The model achieves over 96% accuracy in capturing key flow behaviors like channeling and overriding while significantly reducing computational time. Results demonstrate that the optimized Modified U-Net reduces training time while maintaining prediction accuracy. The proposed framework enables rapid evaluation of different scenarios, enhancing decision-making for UHS optimization. It is applicable across various aquifer conditions, including different heterogeneities and operational settings, making it a cost-effective alternative to conventional numerical simulations.

Lithium–sulfur batteries (LSBs) show great potential as next-generation energy storage systems due to their high energy density. However, their practical application is hindered by the slow conversion of lithium polysulfides (LiPSs) and the resulting severe shuttle effect. Catalysis has emerged as a promising solution to address these challenges, but a single catalyst often falls short of meeting all of the requirements for efficient LiPS conversion. This review highlights synergistic catalytic strategies employing metal-based heterostructures with engineered interfaces between distinct materials having complementary properties, including metal/metal compound-based heterostructures, metal-doped metal-compound-based heterostructures, and single-atom heterostructures. These catalysts exhibit exceptional performance by accelerating LiPS conversion to enhance sulfur utilization and enable long-cycling stability. The methods with advanced characterization techniques and theoretical approaches to understand the functions of heterostructures are also discussed, offering insights into catalyst design and optimization. This review provides perspectives and future directions to advance LSB commercialization through catalyst development.

Dual-enhanced stimulation is an innovative technology aimed at enhancing the permeability and strength of marine hydrate reservoirs by injecting and solidifying a dual-enhanced slurry, forming high-permeability slurry veins for gas and water flow, which is essential for commercial hydrate extraction. This study investigates the mechanisms behind fracture initiation and slurry diffusion in marine hydrate reservoirs during the dual-enhanced stimulation process with the goal of improving stimulation effectiveness. The results show that slurry veins diffused rapidly in the early stage, eventually forming a shuttle shape with a thicker middle section and thinner sides. As hydrate saturation increased, sediment particle cementation strengthened, reducing the slurry filtration. This required higher pressure for fracture initiation but also extended the diffusion distance and the area of the slurry veins. Increasing the injection angle created a complex, uneven stress field near the wellbore, making fracture initiation more challenging. The maximum diffusion distance was achieved at a 30° injection angle, although the slurry vein shape became irregular. Higher injection rates improved slurry diffusion, and at 500 L/min, the diffusion radius reached 10 m and covered nearly 240 m², demonstrating significant improvement in the stimulation effect. The sensitivity analysis indicates that the injection angle had the greatest influence on the initiation pressure, while changes in hydrate saturation had minimal impact. Injection rate was the key influencing factor to the diffusion radius; however, it is essential to determine the optimal point to achieve the appropriate diffusion radius. These findings offer practical insights for applying dual-enhanced stimulation technology in marine hydrate reservoirs and will guide future engineering efforts.

Biogas separation can provide quality CH₄ gas which can be used as a fuel alongside CO₂ capture and sequestration. Hydrate-based gas separation can be a potential technology for effective separation of biogas owing to its compact storage, environmentally benign nature, safe and a simplified process with no chemical reactions involved. This study investigates the effect of 1,3 dioxolane (DIOX) on the kinetics and separation of 50–50 mol % CO₂–CH₄ (biogas) mixture using DIOX concentrations of 1, 3, and 5.56 mol % and presents morphological observations during hydrate formation/dissociation. Addition of bioadditives (l-methionine and l-arginine at 0.5 wt % concentration) was also examined particularly with the stoichiometric concentration (5.56 mol %) of DIOX. Experimental results showed the kinetic promotion effect in terms of rate of hydrate formation, t₉₀, and final gas uptake was enhanced with the increasing concentration of DIOX. The highest gas uptake of 49.88 ± 0.75 mmol/mol was obtained using 5.56 mol % DIOX + 0.5 wt % l-methionine with the shortest t₉₀ of 45.4 ± 1.83 min. Kinetic promotion ability of DIOX was found to increase with the increasing concentration of DIOX for the 50–50 mol % CO₂–CH₄ biogas mixture. A dissociation study showed a decrease in rate of normalized moles of gas release on increasing concentration of DIOX from 1 to 5.56 mol %. On adding additives, dissociation rate increased for 0.5 wt % l-methionine and it was observed to be the highest for 0.5 wt % l-arginine; thus, the kinetic additives have a strong influence on hydrate dissociation despite their effect in enhancing the formation kinetics, gas recovery, and the separation factor. Based on the observations, it was inferred that for the separation of equimolar biogas mixture, nonstoichiometric concentrations (<5.56 mol %) are preferred rather than stoichiometric concentrations of DIOX.

The cofiring of coals with biomasses is already a common practice, largely due to the German government’s decision to phase out coal use. For example, biomasses in the form of wood pellets are being employed to replace coal firing and cocombustion. In order to understand the mechanisms and subsequently counteract the increased deposit formation and corrosion caused by the increased concentrations of alkali, S, and HCl, two different coals, two woody biomasses, one sludge, and their mixtures have been comprehensively investigated regarding their release and ash behavior under simulated combustion conditions. The substances released during combustion at temperatures of 800 and 1200 °C were quantified in situ using molecular beam mass spectrometry (MBMS). Additionally, solid- and gas-phase interactions were calculated using FactSage with the GTKT and SGPS databases. The results of the calculations and the XRD data of the fuels and ashes were employed to facilitate the analysis of the complex matrix and the released compounds. The main released fraction in all experiments was SO_x and the hydrogen chloride (HCl) compounds. The distinction between the two temperatures is illustrated by the alkali elements released. These were predominantly released at the higher temperature from the biomasses. Additionally, MCl⁺ [M = Na, K] were identified, but M₂SO₄⁺ [M = Na, K] could not be detected. The effect of sewage sludge on the mixtures is dependent upon the distribution and ash content of the fuel as this influences the slagging temperature.

The stress differences between the overburden weight and horizontal soil pressure result in the reservoir of the South China Sea being subjected to various stress states. Understanding the mechanical responses of hydrate-bearing silty-clay sediments under varying consolidation states, particularly under typical deviatoric consolidation conditions, is essential for the sustainable and safe extraction of hydrates. Hydrate-bearing silty-clayey sediments were prepared under varying consolidation states using isotropic or deviatoric consolidation methods, and their mechanical behaviors were analyzed through triaxial shearing tests. The results indicate that hydrate saturation affects the inflection point of strain hardening curves in deviatoric consolidation sediments. The sediment failure strength demonstrates a positive linear correlation with hydrate saturation, consolidation stress ratio, and effective confining pressure. Sediments subjected to deviatoric consolidation exhibit stronger cohesion; however, the deviatoric consolidation method does not alter the effect of hydrate saturation on sediment cohesion and the internal friction angle. The consolidation stress ratio and effective confining pressure influence the volumetric deformation of sediments through competing effects of compaction-induced reduction in residual compressibility and particle breakage-induced filling of pores by smaller particles. The effect of hydrate saturation on sediment volumetric strain is jointly influenced by variations in pore space, shearing dilation trend, and effective stress. The strength and deformation characteristics of hydrate-bearing silty-clayey sediments under deviatoric consolidation conditions are investigated in this study, with the objective of providing theoretical support for hydrate extraction in the South China Sea.

P2-type transition-metal oxides as promising cathode materials for sodium-ion batteries (SIBs) possess unique layered structures and superior electrochemical properties, but suffer from the kinetic retardation and structural instability caused by problems such as Na⁺/vacancy ordering, Jahn–Teller distortion, and irreversible P2–O2 phase transition. Herein, we report the fabrication of a P2-type Na_0.67Li_0.05Ni_0.28Mn_0.67O₂ cathode material via a simple solid-state method, using micro-octahedral Mn₂O₃ as Mn-precursor with simultaneous Li-doping. The combined adoptions of micro-octahedral Mn₂O₃ precursors and Li-doping effectively enhance the structural stability of the Na_0.67Li_0.05Ni_0.28Mn_0.67O₂ cathode by inhibiting the Jahn–Teller distortion and suppressing the phase transition of P2–O2 and increase the electronic conductivity and ion diffusion coefficient during charging and discharging processes. Consequently, the as-fabricated Na_0.67Li_0.05Ni_0.28Mn_0.67O₂ cathode demonstrates superior sodium storage performance, delivering a reversible capacity of 144.6 mAh g^–1 at 0.1C with 91.8% capacity retention after 50 cycles and sustaining 82.6% capacity retention after 500 cycles at 5C. This research offers a viable approach for creating high-performance P2-type cathodes for advanced SIBs.

The growth of zinc dendrites and side reactions such as the hydrogen evolution reaction (HER) significantly impede the practical implementation of aqueous zinc-ion batteries (AZIBs). To overcome these obstacles, a strategy for interfacial layer design inspired by the fluid mosaic model is proposed. Sodium decane-1-sulfonate (C₁₀SO), an anionic surfactant with a suitable carbon chain length, is introduced to replicate the dynamic behavior of phospholipid molecules, resulting in the formation of a stable interfacial layer that enhances the cycling stability of the electrode/electrolyte interface. Theoretical calculations and experimental analyses indicate that the SO₃^– headgroup of C₁₀SO preferentially adsorbs onto the zinc anode surface, while the carbon chain tail aligns in an orderly manner due to van der Waals forces and hydrophobic interactions. The combined interaction between the zinc-affinitive headgroup and the hydrophobic tail facilitates the spontaneous formation of a stable interfacial layer. This layer effectively prevents water molecules from directly contacting the zinc anode and provides pathways for Zn²⁺ migration, thereby improving the zinc deposition behavior. Experimental results reveal that a Zn||Zn symmetric cell incorporating C₁₀SO achieved a cycling life of 3800 h at a current density of 1 mA cm^–2. Additionally, the Zn||AlVO-NMP full cell demonstrated a capacity retention of 70.3% after 5000 cycles at 5 A g^–1. These findings confirm the significant impact of this interfacial design strategy on zinc anode stability and present a novel approach for the selection and optimization of electrolyte additives.

One of the chemical methods to prevent gas hydrate formation in oil and gas operations is the deployment of kinetic hydrate inhibitors (KHIs). During the past decade, polyamine oxides have been shown to be powerful KHIs. Here, we present the first study on polyvinyldialkylamine oxides as KHIs. First, Structure II tetrahydrofuran hydrate crystal growth inhibition was observed to be the most powerful when the alkyl group in the polymer was n-butyl (PVBu₂AO). High-pressure tests in steel rocking cells were carried out, with both methane and a synthetic natural gas (SNG) mixture. Slow constant cooling and isothermal testing were used. The butylated polymer was also the best in the gas hydrate experiments, with the lowest molecular weight polymer, PVBu₂AO-LMw (Mw ca. 20,000 g/mol), giving the best results. It performed better than poly(N-vinyl caprolactam) (PVCap) with both gases and with both test methods, even though PVCap had a lower and more optimized molecular weight of about 4000 g/mol. The high flash point solvent, n-butyl glycol ether (nBGE), was shown to be an excellent synergist. For example, in isothermal tests with SNG using 5000 ppm of PVBu₂AO-LMw and 5000 ppm of nBGE, hydrate formation onset was delayed about 1.5 days at 70 bar and 13.1 °C subcooling. The same blend using 101 bar of methane at 8.1 °C subcooling gave no hydrates in 18 h, but hydrates did form after ca. 12–18 h at 10.9 °C subcooling. In summary, polyvinyldialkylamine oxides were shown to be a powerful new class of KHI polymers which could probably be further optimized for even higher performance, for example, at lower molecular weight.