Search Results (593)

This study investigates the solubility correlation of oil extracted from Sabah green Robusta coffee (Coffea canephora) beans through supercritical carbon dioxide (SC-CO₂) extraction. Sabah, recognized as the largest coffee-producing region in Malaysia, serves as a significant source of Robusta beans for this research. The solubility of coffee bean oil was evaluated under varying pressures (10–30 MPa) and temperatures (40–80 °C). The maximum solubility, 2.681 mg/g CO₂, was recorded at 30 MPa and 40 °C, whereas the lowest solubility, approximately 0.440 mg/g CO₂, occurred at 20 MPa and 80 °C. A clear inverse relationship between solubility and temperature was observed, with solubility decreasing as temperature increased to 80 °C. Conversely, elevated pressure, particularly at 30 MPa, enhanced solubility due to the increased density and solvent power of SC-CO₂. Experimental data exhibited strong agreement with Chrastil’s equation, yielding a relatively low percentage error of 3.37%, compared with 14.57% for the del Valle-Aguilera model. These findings demonstrate the reliability of Chrastil’s model in predicting the solubility of Sabah green coffee bean oil in SC-CO₂. Overall, the research highlights the potential of SC-CO₂ extraction as a sustainable, solvent-free approach for obtaining high-quality coffee oil extracts, with promising applications in the food industry and possible extension to the recovery of other bioactive compounds in food processing. Full article

In recent years, advanced CO₂ cycles, including supercritical CO₂ power cycles, transcritical CO₂ power cycles and refrigeration cycles, have demonstrated significant potential for application across a broad spectrum of energy conversion processes, owing to their high efficiency and compact components that are environmentally benign and non-polluting. This study presents a comprehensive review of the dynamic performance and control strategies of these advanced CO₂ cycles. It details the selection of system configurations and various control strategies, detailing the principles behind different control strategies, their applicable scopes, and their respective advantages. Furthermore, this study conducts a comparison between the joint control strategy and single control strategies for CO₂ cycles, demonstrating the superiority of the joint control strategy in CO₂ cycles. It then delves into the potential of novel control technologies for CO₂ cycles, using model-based control technology powered by artificial intelligence as a case study. This study also offers an extensive overview of control theory, methodology, scope of application, and the pros and cons of various control strategies, with examples including extreme value-seeking control, model predictive control (MPC) based on an artificial neural network model, and MPC based on particle swarm optimization. Finally, it explores the application of AI-controlled CO₂ cycles in new energy vehicles, solar power generation, aerospace, and other fields. It also provides an outlook on the development direction of CO₂ cycle control strategies in light of the evolving trends in the energy sector and advancements in AI methodologies. Full article

Carbon Capture and Storage (CCS) is a vital climate mitigation strategy aimed at reducing CO₂ emissions from industrial and energy sectors. This review presents a comprehensive analysis of CCS technologies, focusing on capture methods, transport systems, geological storage, geomechanical and geochemical aspects, modeling, risk assessment, monitoring, and economic feasibility. Among capture technologies, pre-combustion capture is identified as the most efficient (90–95%) due to its high purity and integration potential. Notably, most operational CCS projects in 2025 utilize pre-combustion capture, particularly in hydrogen production and natural gas processing. For geological storage, saline aquifers and depleted oil and gas reservoirs are highlighted as the most promising due to their vast capacity and proven containment. In the transport phase, pipeline systems are considered the most effective and scalable method, offering high efficiency and cost-effectiveness for large-scale CO₂ movement, especially in the supercritical phase. The study also emphasizes the importance of hybrid integrated risk assessment models, such as NRAP-Open-IAM, which combine deterministic simulations with probabilistic frameworks for robust site evaluation. In terms of monitoring, Seismic monitoring methods are regarded as the most reliable subsurface technique for tracking CO₂ plume migration and ensuring storage integrity. Economically, depleted reservoirs offer the most feasible option when integrated with existing infrastructure and supported by incentives like 45Q tax credits. The review concludes that successful CCS deployment requires interdisciplinary innovation, standardized risk protocols, and strong policy support. This work serves as a strategic reference for researchers, policymakers, and industry professionals aiming to scale CCS technologies for global decarbonization. Full article

SiCp/Al composites (Silicon Carbide Particle-Reinforced Aluminum Matrix Composites), due to their light weight, high strength, and superior wear resistance, are extensively utilized in aerospace and other sectors; nonetheless, they are susceptible to tool wear and surface imperfections during machining, which negatively impact overall machining performance. Supercritical carbon dioxide minimal quantity lubrication (SCCO₂-MQL) is an environmentally friendly and efficient lubrication method that significantly improves interfacial lubricity and thermal stability. Nonetheless, current lubrication models are predominantly constrained to gas–liquid two-phase scenarios, hindering the characterization of the three-phase lubrication mechanism influenced by the combined impacts of SCCO₂ phase transition and ultrasonic vibration. This study formulates a lubricant film thickness model that incorporates droplet atomization, capillary permeation, shear spreading, and three-phase modulation while introducing a pseudophase enhancement factor β_ps(p,T) to characterize the phase fluctuation effect of CO₂ in the critical region. Simulation analysis indicates that, with an ultrasonic vibration factor Af = 1200 μm·kHz, a lubricant flow rate Q_f = 16 mL/h, and a pressure gradient Δp_tot = 6.0 × 10⁵ Pa/m, the lubricant film thickness attains its optimal value, with Δp_tot having the most pronounced effect on the film thickness (normalized sensitivity S = 0.488). The model results align with the experimental trends, validating its accuracy and further elucidating the nonlinear regulation of the film-forming process by various parameters within the three-phase synergistic lubrication mechanism. This research offers theoretical backing for the enhancement of performance and the expansion of modeling in SCCO₂-MQL lubrication systems. Full article

In this study, a new type of double crosslinked nanospheres (DCNPM-A) was developed to solve the problem of gas channeling caused by fracture development in the process of CO₂ oil displacement, and the microsphere system with delayed swelling was successfully synthesized by inverse micro lotion polymerization. The microsphere adopts a dual crosslinking structure of stable crosslinking agent (MBA) and unstable crosslinking agent (UCA), achieving intelligent sealing function of shallow low expansion and deep high temperature triggered secondary expansion. The successful preparation of microspheres was verified by characterization methods such as Zeta potential and SEM, and the effects of reaction temperature, time, initiator and crosslinking agent dosage on microsphere properties were systematically studied. The experimental results show that DCNPM-A microspheres exhibit excellent expansion performance, thermal stability, and acid resistance in acidic, high-temperature, and high mineralization environments. Their expansion ratio can reach 13.5 times, and they can maintain stability for more than 60 days in supercritical CO₂ environments. Core displacement experiments have confirmed that the microspheres have the best sealing performance in matrices with a permeability of 10 × 10⁻³ μm² and fractures with a width of 0.03 mm. The combination of 0.8 PV injection volume, 0.5 mL·min⁻¹ injection rate, and continuous injection method significantly improved the plugging rate and recovery rate of CO₂ flooding. This study provides new technical support for the efficient development of low-permeability fractured reservoirs. Full article

The growing demand for sustainable technologies in the extraction and functionalization of bioactive compounds has driven the development of innovative, eco-efficient methodologies. This study assesses the feasibility of high-pressure green technologies—Enhanced Solvent Extraction (ESE) and Pressurized Liquid Extraction (PLE)—for extracting bioactive compounds from the leaves of Petiveria alliacea, a medicinal plant with significant pharmacological potential. The extracts obtained under optimal PLE conditions (100 bar, 75 °C, ethanol/water: 50:50 v/v) exhibited the highest total phenolic content (76.27 mg GAE/g) and notable antioxidant capacity. The same extract was tested for its antimicrobial activity against Escherichia coli, showing a minimum inhibitory concentration (MIC) of 9.48 µg/mL. Furthermore, the extract was successfully impregnated into polylactic acid (PLA) filaments via supercritical CO₂ processing, achieving a maximum antioxidant inhibition of 6.81% under mild conditions (100 bar, 35 °C). The combination of pressurized extraction and supercritical impregnation provides a scalable and environmentally friendly pathway for producing functional biomaterials. These findings highlight the potential of integrating green extraction and material functionalization within the context of the circular bioeconomy and industrial biotechnology. Full article

Abnormal skin pigmentation can cause significant esthetic concerns and impact quality of life. As melanin determines pigmentation, melanogenesis is a key target to manage pigmentation disorders. This study investigated the effects of extracts from the rhizome of Iris ×germanica L. var. florentina Dykes (often called Iris florentina L.) on melanogenesis. Active phytochemicals were identified by combining LC-MS-MS metabolic profiling with subsequent bioassay-directed fractionation of chromatographic eluent collected into 96-well plates. Fractions 41–43 increased melanin and contained germanaism B, providing evidence that it is a melanogenesis stimulator. In contrast, fractions 90–93 reduced melanin and contained iriflorental and iripallidal, identified as prospective melanogenesis inhibitors. To explore extract-based applications, the plant was subjected to ethanolic, chloroform, and supercritical carbon dioxide (SC-CO₂) extractions and tested in skin equivalent tissues. The ethanolic extract (rich in germanaism B) increased pigmentation, while the chloroform extract (higher in iriflorental and iripallidal) decreased it. The SC-CO₂ extract, with minimal germanaism B and enriched iriflorental and iripallidal, showed stronger depigmenting effect. This study is the first to report that rhizome of I. florentina contains phytochemicals with opposing effects on melanogenesis. Through different extraction processes, targeted extracts from a single botanical can address both hyper- and hypopigmentation, offering a novel approach to pigmentation modulation. Full article

Printed circuit heat exchangers (PCHE) are ideal for use in very demanding operating conditions. In addition, they are characterized by very high efficiency, which can still be increased. This paper presents new concepts for improving PCHE heat exchangers. The aim of the described work was to evaluate the potential for improving the performance of printed circuit heat exchangers by incorporating open-cell metal foam as the heat exchanger packing material. The evaluation was conducted based on the results of numerical simulation of supercritical carbon dioxide cooling flowing through printed circuit heat exchanger channels filled with 40 PPI copper foam with 90% porosity. A unit periodic region of the heat exchanger comprising two adjacent straight channels for cold and hot fluid was analyzed. The channels had a semicircular cross-section and a length of 200 mm. Studies were conducted for three different channel diameters—2, 3, and 4 mm. The range of mass flux variations for cold fluid (water) and hot fluid (sCO₂) were 300–1500 kg/(m²·s) and 200–800 kg/(m²·s), respectively. It was found that in channels filled with metal foam, carbon dioxide cooling is characterized by a higher heat transfer coefficient than in channels without metal foam. In channels of the same diameter, heat flux was 33–63% higher in favor of the channel with metal foam. Thermal effectiveness of the heat exchanger with metal foam can be up to 20% higher than in the case of a heat exchanger without foam. Despite very high pressure drop through channels filled with metal foam, thermal–hydraulic performance can also be higher—even 4.7 in the case of a 2 mm channel. However, both these parameters depend on flow conditions and channel diameter, and under certain conditions may be lower than in a heat exchanger without metal foam. The results of the presented work indicate a new direction for the development of PCHE heat exchangers and confirm that the use of metal foams in the construction of PCHE heat exchangers can contribute to increasing the efficiency and effectiveness of the processes in which they are used. Full article

The corrosion behavior of austenitic steel HR3C in supercritical CO₂ at 550–600 °C under 25 MPa for 1000 h was investigated. The corrosion kinetics of HR3C were evaluated using weight change measurements. The microstructure and phase composition of HR3C were studied via scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and secondary ion mass spectroscopy. Weight gain data showed that the HR3C exhibited excellent corrosion resistance and that the corrosion kinetics followed a near-parabolic law. The surface of the sample is composed of fine granular oxides, with the main elements including C, O, Cr, Fe and Ni. The oxide phase analysis indicated that protective Cr₂O₃ formed, and a small amount of Fe₂O₃ was also detected. Carbon enrichment was observed on the surface of the outmost layer and the interface of the oxide layer and substrate. The corrosion mechanism and carbon diffusion process are furthermore discussed. Full article

Xanthones from mangosteen pericarp (MP) are bioactive compounds with promising pharmaceutical and nutraceutical applications. However, their efficient and selective extraction using environmentally friendly solvents remains a challenge. This study aimed to evaluate tricaprylin (C8) and tricaprin (C10) as novel green co-extractants in supercritical carbon dioxide (scCO₂) extraction for the recovery of xanthones from MP, using a mass ratio of C8:C10 = 0.64:0.36, hereafter referred to as C8/C10, and to model extraction kinetics for process design and scale-up. Extraction performance was investigated using different C8/C10–MP mass ratios and scCO₂ conditions at temperatures of 60 °C and 70 °C and pressures of 250 bar, 350 bar, and 450 bar. A pseudo-first-order kinetic model was applied to describe the extraction profile, and the kinetic parameters were generalized using second-order polynomial functions of temperature and pressure. The highest xanthone yield (39.93 ± 0.37%) and total xanthone content (51.44 ± 2.22 mg/g) were obtained at a 40% C8/C10–MP ratio under 70 °C and 350 bar, where the C8/C10 mixture outperformed other tested co-extractants in both efficiency and selectivity, particularly for α-mangostin. The extraction profiles were well described by the pseudo-first-order kinetic model, and the generalized model predicted the extraction yield with an uncertainty of 2.3%. C8/C10 is a highly effective and scalable co-extractant for scCO₂ extraction of xanthones, offering a foundation for industrial applications in food, nutraceutical, and pharmaceutical sectors. Full article

Fruit pomace, generated as a by-product of juice processing, is a valuable source of bioactive compounds but requires sustainable extraction approaches to enable its valorisation. Supercritical CO₂ extraction (SFE-CO₂) represents a promising green technology due to its efficiency, solvent-free character, and tuneable selectivity. In this study, the response surface methodology (RSM) was applied to evaluate the effects of pressure, temperature, and time on the recovery of fat, protein, and total phenolic compounds (TPCs) from blackcurrant (Ribes nigrum) and redcurrant (Ribes rubrum) pomace subjected to conventional- and freeze-drying. The highest protein content (14.5%) was obtained in freeze-dried blackcurrant at 400 bar, 60 min, and 30 °C, while the maximum TPCs (24.60 mg GAE/g d.w.) was reached at 500 bar, 60 min, and 40 °C. The redcurrant samples consistently showed lower extractable values across all the responses. Pressure and time were identified as the most influential process variables, enhancing the solvent density and mass transfer during extraction. These results demonstrate that both the drying pre-treatment and raw material type significantly affect the SFE efficiency and confirm the potential of optimised SFE-CO₂ as a viable strategy for converting fruit pomace into functional ingredients for food, nutraceutical, and cosmetic applications. Full article

Clarifying the phase evolution history of hydrocarbon fluids helps formulate exploration and development strategies. The discovery of the Xinguang Gas Field marks a significant breakthrough in the Western Junggar Basin. However, the phase evolution history of this gas field remains unclear, which hinders the formulation of subsequent exploration strategies. This study employs a comprehensive approach, combining organic geochemistry, fluid inclusions, basin modeling, and PVT testing and simulation, to investigate the characteristics and phase behavior of deep-seated hydrocarbon fluids in this gas field. It also examines the charging history, compositional evolution, and temperature and pressure histories of the reservoir, thereby clarifying the phase transition process of hydrocarbon fluids in the Xinguang Gas Field. This study finds that the deep-seated reservoir fluids in the Jiamuhe Formation (Fm.) of the Xinguang Gas Field exhibit low densities of 0.77 to 0.83 g/cm³, high gas-to-oil ratios (GORs) of 1014.41 to 13,054.77 m³/m³, high methane contents of 91.16% to 92.74%, and retrograde condensation characteristics. Additionally, the reservoir temperature and pressure exceed the critical point and the saturation pressure at reservoir temperature, indicating a supercritical condensate gas phase. The present condensate gas in the Xinguang Gas Field is a mixed hydrocarbon from two charging events. Initially, during the Middle–Late Triassic period, both Block 1 and the Xinguang Gas Field were charged with mature oil. Later, from the Late Cretaceous to Early Neogene periods, a secondary charging of highly mature oil and gas occurred in the Xinguang Gas Field, while the reservoir in Block 1 remained largely unchanged. In the co-evolution of reservoir fluid composition, temperature, and pressure, the phase transitions of the hydrocarbon fluids in the Xinguang Gas Field passed through several stages, including liquid black oil (231.9–80.3 Ma), liquid volatile oil (80.3–79.1 Ma), vapor–liquid two-phase volatile oil (79.1–78.3 Ma), vapor–liquid two-phase condensate gas (78.3–69.1 Ma), and supercritical condensate gas (69.1 Ma–present). Full article

This study introduces a novel, two-stage extraction system that combines Ohmic-Accelerated Steam Distillation (OASD) with Supercritical CO₂ Extraction (SSCO₂) to efficiently recover bioactive compounds from plant-based wastes with varying cell wall complexities. Brewer’s spent grain (BSG) and cocoa shell were selected as representative models for soft and rigid cell wall structures, respectively. The optimized extraction process demonstrated significantly enhanced efficiency compared to traditional methods, achieving recovery rates in BSG of 89% for antioxidants, 91% for phenolic acids, and 90% for polyphenolic compounds. Notably, high yields of p-coumaric acid (95%), gallic acid (94%), ferulic acid (82%), quercetin (87%), and resveratrol (82%) were obtained with minimal cellular structural damage. For cocoa shells, despite their lignin-rich, rigid cell walls, recovery rates reached 73% for antioxidants, 79% for phenolic acids, and 74% for polyphenolic compounds, including chlorogenic acid (94%), catechin (83%), vanillin (81%), and gallic acid (94%). Overall, this hybrid technique significantly improved extraction efficiency by approximately 60% for BSG and 50% for cocoa shell relative to conventional approaches, highlighting its novelty, scalability, and potential for broad application in the sustainable valorization of diverse plant-based waste streams. This research presents a green and efficient platform suitable for valorizing agri-food by-products, supporting circular economy goals. Further studies may explore scale-up strategies and economic feasibility for industrial adoption. Full article

Carbon dioxide capture, utilization, and storage for enhanced oil recovery (CCUS-EOR) represents an effective strategy for reducing CO₂ emissions while improving oil recovery efficiency. However, harsh environmental conditions during the process can induce a supercritical state in captured CO₂, which may undermine the structural integrity of tubular components through corrosion. This study systematically investigated the corrosion behaviors of two tubing steels (P110 and Super 13Cr) in 20 MPa supercritical CO₂ containing trace H₂S/O₂ impurities at 60–120 °C using weight loss tests and surface analysis. The results demonstrate that in water-unsaturated supercritical CO₂ with ≤500 ppmv H₂S, both steels exhibited low general corrosion rates (P110: 0.03 mm/y; S13Cr: 0.01 mm/y), with incomplete surface films partially covering grinding traces. However, S13Cr suffered pitting corrosion at >500 ppmv H₂S. Oxygen introduction triggered severe general/localized corrosion characterized by cracked, non-protective surface films. Reducing O₂ to 500 ppm yielded thin, continuous protective films, eliminating pitting. Temperature critically influenced S13Cr corrosion: decreasing from 120 °C to 60 °C increased the corrosion rates from 0.0031 mm/y to 0.08 mm/y due to enhanced water precipitation and impurity gas dissolution. These findings establish impurity thresholds to ensure acceptable corrosion performance. Full article

Tight oil reservoirs are characterized by low porosity, low permeability, and low saturation, making it difficult to achieve economic development through conventional water injection. This study experimentally evaluated different injection media and oil displacement methods and used nuclear magnetic resonance methods to explain the micro mechanisms of oil displacement during different oil displacement processes. The experiments showed that supercritical CO₂ flooding and supercritical CO₂ and active water alternating flooding were much more useful for low-permeability reservoirs compared with conventional water flooding. This technology can increase the recovery rate by more than 12.0%, which is 33.24% higher than the rate achieved with conventional water injection. In addition, it can effectively improve the rapid increase in water content caused by the rapid advance in the water front during the water injection process. The NMR results indicated good consistency for the recovery efficiency of pores under different oil displacement conditions. When the aperture varied between 0.1 µm and 1 µm (type III), the utilization rate was highest, followed by type IV (1–10 µm), type II (0.01–0.1 µm), and type I (0.001–0.01 µm). By comparison, conventional water and CO₂ alternating flooding was more effective for type III pores, increasing oil recovery by 12.58%, while active water + CO₂ alternating flooding can further drive oil, increasing oil recovery by 33.24% and greatly displacing oil in micro-pores and macro-pores. Full article