Energy & Fuels最新文献

Carbohydrate polymers have emerged as renewable, biodegradable materials with dual roles in gas hydrate management. This sustainable functionality positions them as a crucial alternative to conventional chemical inhibitors and promoters, which are often associated with significant ecological toxicity and environmental hazards. However, despite their potential, the literature lacks a comprehensive and systematic review that critically consolidates their dual role as both inhibitors and promoters while connecting fundamental research to practical application. To address this gap, this review provides a critical analysis of the current state of knowledge regarding carbohydrate polymers in gas hydrate systems. It comprehensively examines their dual roles as both kinetic inhibitors and promoters. The review also provides a foundational overview of gas hydrate structures and a classification of carbohydrate polymers, followed by a critical analysis of standard experimental methodologies, characterization techniques, and molecular dynamics simulations. Finally, this work underscores the potential of carbohydrate polymers to enable sustainable hydrate management technologies and identifies critical research gaps that must be addressed to develop them into cost-effective and high-performance solutions.

Ammonia (NH₃) has the potential to decarbonize combustion engines for deep-sea shipping as a noncarbonaceous fuel. The low reactivity of NH₃ necessitates the use of a combustion-enhancing strategy. This study explores a dual-fuel approach using small heptane pilot injections to improve the ignition and combustion of liquid NH₃ injections under typical compression ignition engine conditions. A novel constant volume combustion chamber with direct fuel injectors is used. Among other criteria, ignition delay time is defined and measured from heat release analysis. Spray interaction is controlled by various relative injection timings, relative injector rotation, and pilot umbrella spray angle. Seven- and Single-hole pilot injections are performed to reduce the consumption of pilot fuel, reaching ammonia energy shares of 45–96%. The fuel spray interaction, both spatially and temporally, is found to be crucial in controlling the heat release characteristics of NH₃ combustion. To reduce pilot fuel consumption, it is essential to aim the combustion energy and hot combustion products at the locations of the NH₃ spray. The results show that hot pilot combustion products should interact with (1) areas close to the nozzle, where strong NH₃ evaporation cools the surrounding air, resulting in predominantly rich NH₃/O₂ mixtures that lack sufficient temperature to reach autoignition, or (2) regions with lean NH₃ mixtures that fail to sustain a flame. In (1), small pilot injections are prone to extinction owing to the influence of ammonia evaporation. Because (2) requires continuous pilot interaction, it is recommended to avoid very lean zones in general and ignite NH₃ in areas close to stoichiometry, thereby reducing the quenching potential near the chamber walls and crevices. The results were combined to propose an ideal multipoint injection strategy.

High-temperature conditions significantly influence the physicochemical and mechanical characteristics of rocks, directly affecting deep geological applications, such as UCG, CCUS, and nuclear waste management. This research investigates the divergent thermomechanical response of sandstone and shale from the Barakar Formation, Jharia Basin, India, exposed from room temperature to 700 °C. A comprehensive multitechnique approach utilizing UCS, BTS, ultrasonic velocity, LPGA, He Pycnometer, and SEM was employed to analyze the interplay of porosity, microstructure, and mechanical integrity with temperature. We propose a three-zone paradigm for thermal degradation using the integrated data set, which mechanistically describes the nonlinear evolution of both rock types. Zone 1 is a conditioning stage characterized by minimal microcracking, mineral stability, and the loss of absorbed water. Due to intergranular tightness, sandstone temporarily gains strength, whereas shale loses strength due to clay mineral dehydration. The key damage-acceleration window, Zone 2, is characterized by organic matter pyrolysis, clay dehydroxylation, the α–β quartz transition, and the rapid formation of interconnected fracture networks. Both rocks experience significant strength loss, while shale disintegrates catastrophically. In Zone 3, high-temperature reorganization occurs due to partial sintering or recrystallization of certain minerals, expansion of fracture networks, and material degradation. Due to bond reprecipitation, sandstone exhibits a slight strength recovery, although shale’s structural integrity is still impaired. The zone-based paradigm offers a mechanistic understanding of the temperature thresholds governing bulk instability and pore–mineral interactions. The thermal design and risk assessment in UCG, geothermal operations, nuclear waste repositories, and fire-damaged rock engineering are directly impacted by these findings.

Extreme high-temperature and high-salinity environments pose severe challenges for the field application of water-based drilling fluids. The thermal degradation of conventional polymer loss control agents is a key factor limiting their performance. The incorporation of nanomaterials offers a novel approach to enhance the high-temperature resistance of polymer loss control agents, making it a research hotspot in this field. In this study, a novel composite additive (DANT/HCM) was developed by physically blending β-cyclodextrin (β-CD) hydrothermal carbon microspheres (HCMs) with a comb-like polymer (DANT). Thermogravimetric analysis showed that DANT/HCM has excellent thermal stability. Structural characterization results reveal that oxygen-containing functional groups on the HCM surface form stable interfacial interactions with polymer segments via hydrogen bonding, conferring unique structural synergistic effects to the system. Scanning electron microscopy images showed that the HCM maintained an intact spherical structure after compositing. Performance tests showed that after aging at 240 °C, the filtration loss of the base mud with 1.5 wt % DANT/HCM was only 9.0 mL, significantly lower than the 20.8 mL of DANT alone. Additionally, this composite material exhibits excellent salt resistance, maintaining a filtration volume of 27 mL even in 30 wt % NaCl drilling fluid. Combined with the zeta potential, particle size distribution, and SEM analyses, the performance enhancement was mainly due to the enhanced thermal stability of the composite system, improved particle dispersion, and the formation of a dense, uniform filter cake structure. This study achieves highly efficient filtration loss reduction by introducing thermally stable, nanosized, water-based, thermally carbonized microspheres and combining them with long-chain comb polymers, thereby forming a unique synergistic loss reduction mechanism. It provides a theoretical basis and practical reference for the development of high-performance, high-temperature-resistant filtration loss reduction additives suitable for ultradeep wells and high-temperature environments and has a good prospect for engineering applications.

Direct air capture (DAC) represents a vital technology for atmospheric CO₂ remediation, but few studies have tested catalysts at dilute atmospheric CO₂ concentrations. Inspired by the carbonic anhydrase metalloenzyme, we report a catalytic DAC strategy employing robust zinc(II) enzyme mimics that enable efficient CO₂ sequestration pathways. A catalyst-mediated CO₂ hydration cycle in aqueous sorbents facilitates accelerated capture from dilute atmospheric air, thereby addressing the kinetic limitations observed in carbonate-based systems. Our developed complexes [ZnC1] and [ZnC2] enhance capture rates up to 2-fold at millimolar concentrations and improve the CO₂ mass transfer by 40–60% in 1 M K₂CO₃ sorbent under ambient conditions. These bench-stable, earth-abundant zinc catalysts operate effectively under dilute CO₂ concentrations, overcoming the kinetic limitations of conventional carbonate-based sorbents. Mechanistic studies support a biomimetic catalytic cycle that facilitates rapid CO₂ conversion, demonstrating that a catalyst-assisted DAC can enable energy-efficient, scalable carbon capture technologies.

The specific division and interpretation of shale formations are crucial for the sustainable development of shale reservoirs. Conventional methods, which rely on well logging curves, seismic analysis, and geochemistry often face high costs, subjective uncertainties, and limited resolution. However, microbial DNA distribution analysis provides a promising alternative. Previous studies have primarily applied underground microbial distribution to production dynamic monitoring, such as interwell communication, production profiling, and fracture height monitoring. However, the application of microbial DNA in specific stratigraphic division has not been fully explored. This paper presents an approach for stratigraphic division and interpretation based on DNA sequencing in shale cuttings. Using DNA sequencing results and rank abundance, a method is developed to establish a geological microbial response profile and monitor the microbial diversity. In addition, a preliminary division method is developed to identify representative bacteria markers for each formation. Furthermore, a specific division method is established through a principal coordinate analysis of bacteria markers. This method provides a resolution of 1–2 m and can assist in stratigraphic division when logging curves have multiple solutions. This user-friendly, environment-friendly, and cost-effective approach offers a more scientific foundation and technical support for the sustainable development of shale oil and gas in a carbon-constrained world.

Tight sandstone reservoirs, characterized by low porosity and permeability, present substantial potential for CO₂ utilization and sequestration. Understanding the mechanical behavior of tight sandstone under the influence of CO₂ is critical for assessing geological CO₂ sequestration and the CO₂ fracturing capabilities of reservoirs. As the burial depth of the target reservoir increases, the formation temperature gradually rises, considerably altering the mechanical properties of reservoir sandstone, especially the interaction between CO₂ and sandstone. However, few studies on the coupled effects are available. In this study, we built a high-temperature CO₂ soaking system that allows CO₂ injection across various formation temperatures (25 °C–160 °C). Uniaxial compression tests were conducted to explore the mechanical properties of the tight sandstone subjected to CO₂ soaking at various temperatures. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy were used to quantitatively characterize the evolution of the mineral composition and micromorphology of tight sandstone after CO₂ soaking at different temperatures. A stress–strain damage constitutive model was established to describe the behavior of tight sandstone under the coupled effects of temperature and CO₂. The quantitative relationships between mineral dissolution, pore-throat evolution, and crack propagation revealed by SEM, XRD, and EDS analyses were integrated into the model to describe the prepeak damage evolution and deformation characteristics. The proposed model not only effectively characterized the macroscopic mechanical behavior of tight sandstone under coupled temperature–CO₂ conditions but also provides a mechanistic explanation for the role of microstructural changes in controlling damage accumulation and strength degradation.

CO₂-enhanced oil recovery (CO₂-EOR) is a key carbon capture, utilization, and storage (CCUS) technology, delivering the dual benefits of enhanced oil recovery and CO₂ geological storage. However, conventional CO₂ gas flooding suffers from high gas mobility, early breakthrough, and a poor sweep efficiency. This study innovatively employed the green biodegradable surfactant alkyl polyglucoside (APG) and polymer xanthan gum (XG) to stabilize microbubbles, establishing a microbubble CO₂ (MB-CO₂) flooding system. The microscopic mechanisms of MB-CO₂ flooding in heterogeneous porous media were systematically investigated by using a custom-built in situ visual microfluidic platform. The results reveal that MB-CO₂ enhances oil recovery through three synergistic mechanisms: plugging mechanism (enabling dynamic synergistic plugging via the Jamin effect to expand sweep volume), interfacial interactions (weakening oil adhesion through wettability alteration and oleophilic interaction to promote oil stripping), and emulsification promotion (improving oil mobility via local shear and disturbance). Experimental results demonstrate a remarkable oil recovery factor of 93.64% and an extended breakthrough time of 0.734 PV for MB-CO₂ flooding, substantially outperforming the results of CO₂ gas flooding (45.25%) and APG-XG solution flooding (87.26%). Sector-based analysis further confirms superior recovery efficiency and uniformity across all radial directions, with effective adaptation to both high- and low-porosity zones and suppression of premature gas breakthrough. This work elucidates the multimechanistic synergy of MB-CO₂ flooding and provides a theoretical and experimental foundation for its industrial application, offering significant insights for advancing CCUS deployment and fostering a sustainable energy transition.

An extended-duration gas production test from a gas hydrate-hosting sand layer was conducted in the JOGMEC–DOE–USGS Collaborative Gas Hydrate R&D Project in Alaska. Thick gas hydrate-bearing sand layers within the Prudhoe Bay Unit, sampled as part of the project, were studied to obtain fundamental data relevant to reservoir characterization and insights into the evolution of gas hydrate-hosting sand layers. Geochemical and petrophysical data were collected from pressure-cored sediments, gas hydrates, and interstitial water in approximately 15-m thick D1 and B1 sands (699 and 844 m in top, respectively) and from the overlying clay-rich layers. The proportion of sand-sized particles increased upward within the B1 sand of the progradation deposit; quartz content also increased upward. These parameters correlated with the electrical resistivity profile. The degree of gas hydrate saturation could be linked to the grain size pattern of the host sediments. Grain size and mineralogical data indicated a less smooth progradation process for the D1 sand than for the B1 sand. Scattered authigenic pyrite contents in the D1 sand suggest that geochemical processes within the sediments were accompanied by fluctuations. Distributions of spherical aggregates of fine siderite particles were restricted to the upper part of the B1 sand, where the highest hydrate saturation was observed. The local occurrence of carbonate-saturated brine was probably linked to high gas hydrate formation in the past. In situ chloride concentrations of interstitial water were ∼70 mM in the clay-rich layer above the D1 sand and ∼35 mM above and within the B1 sand. The downward freshening trend is consistent with diffusion following brine formation caused by thickening permafrost during the most recent glaciation 20 ky ago. The lower half of the D1 sand may have been influenced by present freshwater input, then exhibit unexpectedly low in situ chloride concentrations.

The search for efficient catalysts for the electrochemical reduction of CO₂ into value-added fuels is ongoing. In this work, we investigate Mo₂B, a two-dimensional (2D) MBene and an extension of the MXene family, as a potential catalyst for CO₂ capture and reduction using first-principles calculations. In this study, the CO₂ capture properties of pristine 2D Mo₂B in the 2H phase, along with its functionalized derivatives Mo₂BX₂ (X = O, OH, H), are systematically evaluated. We found that Mo₂BX₂ is inert toward CO₂ capture, while pristine Mo₂B interacts strongly and effectively activates CO₂ with a stronger adsorption energy of −2.47 eV. Projected density of states and Bader charge analyses reveal that pristine Mo₂B exhibits a stronger CO₂ capture affinity, which can be attributed to the high population of Mo d_z² states near the Fermi level and the substantial charge donation (∼0.31e) from each surrounding Mo atom to the O atoms of CO₂. This substantial Mo-to-O charge transfer weakens the C═O bonds, thereby facilitating CO₂ activation and the subsequent reduction mechanism. In contrast, surface functionalization weakens the direct interaction between Mo and CO₂, leading to suppressed charge transfer. Electronic structure analysis also reveals that the stronger C═O interaction on Mo₂B is primarily governed by the Mo d_z² and C/O p_z orbitals of CO₂. Further analysis of the reduction pathways indicates that captured CO₂ can be converted to CH₄, with the CO → HCO step exhibiting the highest Gibbs free energy change. The low limiting potential of Mo₂B (−0.570 V), in comparison with the Gibbs free energy of H adsorption (−0.63 eV), suggests higher selectivity toward the CO₂-to-CH₄ conversion over the competing hydrogen evolution reaction. These results highlight Mo₂B as a promising candidate for the electrochemical reduction of CO₂. These theoretical insights may pave the way for the experimental realization of MBenes tailored for the CO₂ reduction reactions.