最新刊期
卷 49 ， 期 9 ， 2024
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摘要：Under the goals to reach carbon peaking and carbon neutrality, the clean and efficient utilization of fossil fuels has become a crucial aspect of the energy transition. Methane as one of the cleanest fossil energies, has been widely regarded as a key technology with good development prospects in energy transition for high-value and clean utilization. Methane pyrolysis for hydrogen process has the advantages of producing high-purity H2 and carbon materials without directly generating CO2. Three typical methane pyrolysis for hydrogen processes: catalytic methane pyrolysis in fluidized beds, plasma methane pyrolysis, and molten medium methane pyrolysis were summarized and their principles, advantages, disadvantages and research progress were introduced. Among these processes, catalytic methane pyrolysis in fluidized beds requires the least energy but the catalysts are prone to carbon deposition, leading to unsustainable reactions and difficulty in separating carbon materials from catalysts, affecting downstream use. Plasma methane pyrolysis has a high conversion rate but requires a substantial energy input. Molten medium methane pyrolysis has lower energy consumption, and the carbon materials float on the surface of the molten medium, not hindering the continuous reaction and are easily separated and collected. However, the high temperature of the molten medium requires high requirements for the reactor materials, and the cost of purifying carbon materials also affects the economic viability of this process for industrialization. Combining renewable energy is the future trend towards achieving clean and efficient methane pyrolysis for hydrogen. Utilizing renewable energy sources such as solar and wind energy to provide the energy required for methane pyrolysis processes, can reduce the reliance on traditional energy. From current research and development trends, molten medium methane pyrolysis process for hydrogen integrated with renewable energy sources is expected to become the key process for methane pyrolysis for hydrogen and carbon materials.关键词：natural gas;methane pyrolysis;hydrogen production;carbon products;reaction technology- 60
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发布时间：2024-09-29 -
摘要：As clean energy, hydrogen energy has great potential for development. Methane steam reforming is an economical and environmentally friendly hydrogen production method, which can produce high-purity hydrogen and reduce carbon emissions. However, due to the rapid change of the reaction rate during the chain transfer process of the reaction, the reaction mechanism is still unclear. CHEMKIN simulation software was used to couple the methane steam reforming reaction kinetic model with the Plug Flow Reactor (PFR). The simulation was carried out under the reaction conditions of the temperature of 1200 K, water-carbon ratio (molar ratio) of 3.0, and gas inlet mass flow rate of 0.01 g/s. By analyzing the elementary reaction rates of CH4, H2O and intermediate product CH3, the main substances involved in the reaction were determined, and the reaction mechanism (mainly refers to the reaction pathways) was further analyzed. The results show that the adsorption and desorption reaction of water vapor and methane on the catalyst surface, and the dissociation reaction of H2O(s) (s represents adsorbed state) and CH4(s) on the catalyst has a great influence on methane steam reforming reaction. The two dissociation reactions of CH4(s) on the catalyst surface are direct dissociation and reactive dissociation with O(s), and the reaction rate with O(s) is higher than the direct dissociation rate. The reaction pathway of CH4(s) on the catalyst surface is CH4(g) → CH4(s) → CH3(s) → CH2(s) → CH(s) → C(s), and CH4(g) → CH4(s) → CH3(s) has the greatest influence on the reaction. H2O(g) is also adsorbed on the surface of catalysts, and the reaction pathway is H2O(g) → H2O(s) → OH(s) → H(s).关键词：methane steam reforming;reaction rate;reaction mechanism- 14
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发布时间：2024-09-29 -
摘要：Biogas steam reforming is one important way for hydrogen production, and the development of efficient and stable catalysts is the key for its large-scale application. Based on this, a series of Ni-based catalysts based on ZrO2-Al2O3 composite support were prepared by continuous impregnation method, and the catalytic performances for hydrogen production by biogas steam reforming were tested. The texture properties and crystal phase compositions of catalysts were analyzed by characterization methods such as N2 adsorption/desorption and XRD. The influence mechanisms of the physical structure and chemical properties of catalysts on their catalytic performances of biogas steam reforming for hydrogen production were studied. The effects of calcination temperatures and metal promotor Fe on the catalytic performances of catalysts were also discussed. The results show that Ni/ZrO2-Al2O3 exhibits outstanding catalytic performance for hydrogen production at 700 ℃ and gas volume space velocity of 12000 h-1, with CH4 conversion rate of 89.94% and H2 yield of 81.49%. Compared with Al2O3 support, ZrO2-Al2O3 composite support increases the specific surface area of catalysts, promotes the high dispersion of small particle size Ni on the surface of the support, and thus improves the catalytic performances of catalysts in biogas steam reforming for hydrogen production. The calcination temperature can regulate the specific surface area and pore volume of catalysts. The specific surface area and pore volume of Ni/ZrO2-Al2O3 calcined at 550 ℃ are larger than those of Ni/ZrO2-Al2O3 calcined at 700 ℃. The coupled modification of Fe and ZrO2 improves the reduction performance of catalysts, and more highly active Ni0 is formed, which is conducive to the occurrence of methane dry reforming for hydrogen production, and the- 23
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发布时间：2024-09-29 -
摘要：To improve the energy efficiency of a coupled natural gas hydrate exploitation and reforming hydrogen production system, process design and modeling were conducted, and models for energy efficiency assessment and economic analysis were established. Focusing on the selection between fuel heating or electric reforming in the reforming process, whether offshore wind power is integrated in electric reforming, and the selection between membrane separation or amine scrubbing in H2 separation, the exergy efficiency ratio and annual total cost of different technical schemes were compared. The results show that System C, with electric reforming without offshore wind power integration and membrane separation, has the highest exergy efficiency ratio (2.25). System B, with fuel heating reforming and membrane separation, has the lowest annual total cost (5803.91 × 106 CNY/a). System F, which integrates offshore wind power and uses amine scrubbing for separation, has the highest annual total cost (5862.09 × 106 CNY/a), only about 1.0% higher than the most economically efficient System B, but with higher energy efficiency. This indicates that the application of membrane separation and offshore wind power on hydrate exploitation platforms has significant potential in both energy efficiency and economy.关键词：natural gas hydrate exploitation;reforming hydrogen production;process design;energy efficiency;economic evaluation- 25
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发布时间：2024-09-29 -
摘要：The preparation methods can affect the type and dispersion of Cu species, as well as the interaction between Cu species and supports in catalysts. Cu/Ce0.8Zr0.2O2 catalysts with Ce0.8Zr0.2O2 sosolid as the support and Cu loading (mass fraction) of 15% were prepared by deposition precipitation, ammonia evaporation, impregnation and co-precipitation methods, respectively. The phase compositions, texture properties, Cu dispersions and microstructures of the catalysts were characterized by XRD, N2 physical adsorption/desorption, N2O titration, SEM, etc. And the catalytic performances of the catalysts for methanol steam reforming to produce hydrogen were evaluated in a fixed-bed reactor. The results show that compared with the Cu/Ce0.8Zr0.2O2 catalysts prepared by another three methods, the Cu/Ce0.8Zr0.2O2 catalyst (Cu/Ce0.8Zr0.2O2-DP) prepared by deposition precipitation method has the largest specific surface area (82.5 m2/g) and Cu specific surface area (206.0 m2/g), as well as the highest Cu dispersion (30.5%). Under the reaction conditions of 250 ℃, atmospheric pressure, n(deionized water):n(methanol) of 1.3:1.0 and liquid space velocity of 6 mL/(g·h) for 24 h, Cu/Ce0.8Zr0.2O2-DP shows relatively optimal catalytic performance with methanol conversion rate of 95.2%, hydrogen production rate of 286.8 mmol/(g·h) and CO selectivity of 0.86%.关键词：methanol steam reforming;Cu-based catalysts;preparation methods;cerium-zirconium sosolid;Cu dispersion- 31
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发布时间：2024-09-29 -
摘要：Transition metal sulfide catalysts with abundant reserves and low prices exhibit high activity for hydrogen production from photocatalytic water splitting and are ideal choices to replace precious metal platinum catalysts. The preparation methods, structural morphologies and hydrogen production rates of transition metal sulfide catalysts for hydrogen production from photocatalytic water splitting were reviewed. Strategies for improving the efficiency of hydrogen production from photocatalytic water splitting by transition metal sulfide catalysts and their composite catalysts were discussed, including expanding the light absorption range, enhancing the separation of photogenerated electron-hole pairs and promoting catalyst surface reactions, to prepare more efficient transition metal sulfide catalysts that meet commercial requirements. At last, the future research trends in the field of hydrogen production from photocatalytic water splitting by transition metal sulfide catalysts were prospected.关键词：hydrogen;transition metal sulfides;photocatalysis;water splitting;solar energy- 54
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发布时间：2024-09-29 -
摘要：The structural regulation of photocatalysts is important to improve the efficiency of photocatalysis. g-C3N4 was prepared from melamine as raw material, and a series of MCx-g-C3N4 (x is the molar ratio of melamine to cyanuric acid, and x = 1, 2, 3 or 4) catalysts were prepared using melamine-cyanuric acid supramolecular as precursor. XRD, FT-IR, SEM, TEM, N2 adsorption/desorption, and XPS were used to characterize g-C3N4 and MCx-g-C3N4, and it is found that g-C3N4 and MCx-g-C3N4 exhibit different morphologies, structures, compositions and specific surface areas. Among them, MC3-g-C3N4 displays porous nanosheet structure with n(C element):n(N element) of 1.23, and the specific surface area is 45.63 m2/g, which is 4.5 times larger than that of g-C3N4. Using Pt as the co-catalyst and triethanolamine as the sacrificial agent, the catalytic performance of catalysts for hydrogen production from photocatalytic water splitting was investigated under visible light (≥ 400 nm). The results show that MC3-g-C3N4 shows the best catalytic performance for hydrogen production from photocatalytic water splitting, and its hydrogen production rate reaches 1127.83 μmol/(h·g), which is 35 times higher than that of g-C3N4. The large surface area and porous structure of MC3-g-C3N4 provide more active sites for the reaction, and the nanosheet structure shorens the migration distance of photogenerated electrons to the catalyst surface, which promotes the separation of photogenerated electrons and holes, and thus significantly improving its catalytic performance for hydrogen production from photocatalytic water splitting.关键词：photocatalysis;visible light;hydrogen production;supramolecular precursor;carbon nitride- 37
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发布时间：2024-09-29 -
摘要：Developing green hydrogen energy and hydrogen fuel cells is considered an important approach to achieving China’s carbon peaking and carbon neutrality goals, which requires the development of highly active, stable and cost-effective electrocatalysts. High-entropy alloy (HEA), with their surface complexity and tunable compositions, offers potential for creating high-performance catalytic active sites. By selecting and regulating components, it is possible to optimize surface active sites for various electrochemical reactions, thereby significantly enhancing the performance of HEA catalysts. In recent years, HEA has garnered widespread attention in the field of electrocatalysis and is expected to become the ideal new electrocatalyst. The main synthesis methods of HEA catalysts were introduced, the latest applications of HEA catalysts in water electrolysis for hydrogen production and hydrogen fuel cells were summarized, and the development trends and challenges faced by HEA catalysts were discussed. The aim is to provide a reference for the design and preparation of HEA catalysts.关键词：high-entropy alloy catalyst;water electrolysis for hydrogen production;hydrogen fuel cells- 62
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发布时间：2024-09-29 -
摘要：The seawater electrolysis for hydrogen production has a wide range of raw materials, which can effectively couple with marine new energy to reduce the cost of offshore electricity, and has become a hot topic in the hydrogen production industry. However, the deposition of Mg2+ and Ca2+, as well as the corrosion of chlorides on the electrolysis cell, hinder the large-scale application of seawater electrolysis hydrogen production technologies. Therefore, improving hydrogen production technologies and developing new electrode materials to reduce the impact of impurities in seawater have become the focus of research and development for seawater electrolysis hydrogen production. Firstly, the main components of seawater and their impacts on the performance and lifespan of seawater electrolysis systems were analyzed. The advantages and disadvantages of different electrolysis seawater hydrogen production technologies were discussed, as well as research progress. It is believed that electrolysis seawater hydrogen production technologies still mainly rely on hydrogen production after seawater purification. Then, the electrode materials for seawater electrolysis were summarized, including precious metal materials, transition metal compound catalytic materials, and new structural materials. Among them, transition metal compound catalytic materials have good development prospects. Finally, the challenges and prospects faced by the industrial application of seawater electrolysis hydrogen production technologies were discussed, and it is pointed out that combining the research results of efficient and long-life transition metal compound catalytic materials, as well as the hydrogen production technologies after seawater purification, will be the development direction of seawater electrolysis in the future.关键词：seawater electrolysis;hydrogen energy;hydrogen production technology;electrode materials- 54
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发布时间：2024-09-29 -
摘要：In order to prepare anion exchange membrane (AEM) with high conductivity and high stability, 1,6-dibromohexane was used as crosslinking agent, and cross-linked poly (biphenyl-piperidine) AEM (PBP-Pip-x% membrane, x represents crosslinking degree and the values of x are 5, 10 and 15, respectively) with different crosslinking degrees were prepared by casting method. The structures and morphologies of PBP-Pip-x% membranes were characterized by 1H NMR and AFM,respectively, and the properties of PBP-Pip-x% membranes were studied by using uncross-linked poly (biphenyl-piperidine) AEM (PBP-Pip membrane) as the control group. The results show that PBP-Pip-15% membrane has better microphase separation structure, and its conductivity (99.14 mS/cm) is significantly higher than that of the PBP-Pip membrane (49.89 mS/cm). PBP-Pip-15% membrane shows good alkali stability, and after soaking in 1 mol/L KOH solution at 80 ℃ for 300 h, the conductivity of PBP-Pip-15% membrane is 37.50 mS/cm and the conductivity retention rate is 79.73%. Under the set up conditions (temperature of 80 ℃, 1 mol/L KOH solution and cell voltage of 2.0 V), the current density of PBP-Pip-15% membrane is 0.5 A/cm2, and the stability of PBP-Pip-15% membrane does not change significantly within 100 h.关键词：cross-linked structure;poly (biphenyl-piperidine);anion exchange membrane;water electrolysis technology- 14
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发布时间：2024-09-29 -
摘要：Formic acid, with a volumetric hydrogen storage capacity of up to 53 g/L, has relatively low toxicity and flammability, making it convenient for storage and transportation, so it is a promising hydrogen carrier for practical applications. Utilizing formic acid as a hydrogen storage medium can effectively avoid the cumbersome processes of hydrogen liquefaction and compression, thereby achieving efficient utilization of hydrogen energy. The principles of hydrogen production from formic acid were elucidated and the latest research advancements of catalysts in this field were reviewed, including supported heterogeneous catalyst systems and homogeneous catalyst systems comprising precious and non-precious metals. The current development status of skid-mounted formic acid hydrogen production systems and skid-mounted formic acid hydrogen production-fuel cell power generation systems were summarized. Their potential application directions were discussed, and a concept of zero-carbon cycle based on green formic acid hydrogen production was proposed.关键词：formic acid hydrogen production;catalyst;skid-mounted hydrogen production;skid-mounted power generation;green formic acid- 27
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发布时间：2024-09-29 -
摘要：The inefficient storage hydrogen is the bottleneck that restricts the large-scale application of green hydrogen energy. Compared with the existing hydrogen storage technologies, naphthalene-decalin organic liquid hydrogen storage, as a highly promising hydrogen storage technology, is expected to provide a new and efficient solution for future energy storage and utilization. The naphthalene-decalin hydrogen storage system can enhance the hydrogen storage capacity of organic liquids, improve the hydrogenation/dehydrogenation cycle and increase economic efficiency. The research progress on naphthalene-decalin organic liquid hydrogen storage technology was reviewed, and the mechanisms of naphthalene hydrogenation and decalin dehydrogenation were analyzed, and the structures of catalysts, processes and technical economy of naphthalene hydrogenation and decalin dehydrogenation were discussed, and the main challenges of naphthalene-decalin organic liquid hydrogen storage technology were summarized. Starting from the key points of demand, through in-depth exploration of the mechanism of decalin dehydrogenation, highly efficient catalysts from the atomic point of view are designed and structures of catalyst surface are constructed to improve the efficiency of decalin dehydrogenation and promote the commercialization of naphthalene-decalin organic liquid hydrogen storage technology.关键词：naphthalene;decalin;hydrogenation;dehydrogenation- 54
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发布时间：2024-09-29 -
摘要：Orthohydrogen and parahydrogen (hereinafter referred to as “orthohydrogen-parahydrogen”) conversion reaction affects the liquefaction process of hydrogen at low temperature and is an important step in the storage and transportation of liquid hydrogen. Traditional iron-based catalysts face problems such as the aggregative growth of active species, the insufficient resistance ability of water and the poor tolerance ability of high temperature. To solve above problems, α-Fe2O3 was encapsulated into amorphous silica with abundant pore structures, and the encapsulated α-Fe2O3@SiO2 catalyst with high catalytic performance in orthohydrogen-parahydrogen conversion was prepared. SEM、XRD and H2-TPR were used to investigate the effects of the encapsulated structure on surface morphologies, crystal structures and reduction abilities of catalysts. The catalytic performances of catalysts were evaluated by test device, and the relationship between the encapsulated structure and catalytic performance was analyzed and summarized. The results show that the encapsulated structure can optimize the pore structure of the catalyst, regulate the electronic property of active sites, improve the structural stability and high temperature tolerance ability of the catalyst, and thereby improve the catalytic performance. When the volume space velocity is 600 min-1, under the action of α-Fe2O3@SiO2 and α-Fe2O3/SiO2 (without encapsulation), parahydrogen volume fractions at the outlet of the device are 41.8% and 37.6%, and the orthohydrogen conversion rates are 22.4% and 16.8%, respectively, indicating that encapsulated iron-based catalysts have high potential for application in the field of orthohydrogen-parahydrogen conversion.关键词：orthohydrogen-parahydrogen conversion;encapsulation;catalysts;electronic property- 7
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发布时间：2024-09-29 -
摘要：To address the high energy consumption and low efficiency of hydrogen liquefaction, a novel hydrogen liquefaction process based on liquefied natural gas (LNG) terminals is proposed. The process utilizes LNG cold energy for precooling and mixed refrigerants for cooling, converting hydrogen at 25 ℃, 2.1 MPa with parahydrogen concentration (mole fraction, the same below) of 25.00% into liquid hydrogen at -252.4 ℃, 130 kPa with parahydrogen concentration of 98.01%. The process, with a handling capacity of 50 t/d, can support 5 × 104 to 10 × 104 hydrogen-powered vehicles. By leveraging the pressure energy of natural gas expansion while maintaining the gas grid entry pressure, the energy consumption of hydrogen liquefaction is reduced. The process was simulated using Aspen HYSYS software. With minimized specific energy consumption as the objective function, MATLAB software was used to optimize key process parameters. Exergy efficiency, figure of merit and coefficient of performance were used as evaluation indicators for energy analysis of the system. The results show that the optimized process reduces specific energy consumption (5.257 kW·h/kg) by 28.09%, which is 17.86% lower than the European IDEALHY project and below the levels reported for similar processes in the literature. The exergy efficiency, figure of merit and coefficient of performance are 45.73%, 0.4573, and 0.2346, respectively, which increase by 39.04% 39.04% and 39.06% compared to before optimization. The exergy efficiency is higher than that reported for most similar processes in the literature. The lower liquefaction pressure of hydrogen is more favorable for equipment manufacturing and safe operation. The process is reasonable and highly efficient, which can provide a reference for hydrogen liquefaction at LNG terminals.关键词：LNG cold energy;pressure energy;hydrogen liquefaction;process optimization- 19
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发布时间：2024-09-29 -
摘要：Hydrogen energy is favored as an ideal clean energy source, and doping hydrogen into natural gas pipelines is an effective way to realize large-scale delivery of hydrogen energy. Once pipelines leaking during transportation, the safe operation of pipelines will be seriously affected. At present, the leakage and diffusion law of hydrogen-doped natural gas buried pipelines in tunnels is not clear. A numerical model of leakage and diffusion for hydrogen-doped natural gas buried pipelines in tunnels was established to study the effects on hydrogen doping ratio (volume fraction), leakage aperture and incoming wind speed of leakage and diffusion characteristics of the gas mixture. The results show that hydrogen-doped natural gas accumulates at the top of tunnel after leaking, showing the phenomenon of high concentration in the center area and low concentration in the edge area. With the increase of hydrogen doping ratio, the lower explosion limit of the gas mixture decreases, and the leakage volume increases. Due to the confined space of tunnel, the gas mixture can not be fully diffused in a short period of time, so the larger the hydrogen doping ratio, the larger the explosion area, and the shorter the time to reach explosion limit. When hydrogen doping ratio increases from 5% to 20%, the explosion danger area increases by 3.18%, the gas to reach explosion limit time decreases by 3.7%. As the leakage aperture increases, the leakage amount of the mixed gas increases, the explosion danger area increases, and the time for the mixed gas to reach the explosion limit decreases. When leakage aperture increases from 20 mm to 100 mm, the distance from ground to the explosion danger area in the radial direction of tunnel decreases from 1.49 m to 0.30 m, the axial explosion danger area increases from 13.4 m to 91.9 m, and the time for gas to reach explosion limit decreases from 95.2 s to 11.3 s. The advection transport effect of incoming wind speed promotes the diffusion of mixed gas along axial direction of tunnel, reduces the high concentration area at the top of tunnel, and makes the explosion danger area significantly smaller. When incoming wind speed increases from 0.5 m/s to 2.0 m/s, the explosion danger area decreases by 81.7%. Therefore, tunnels should be ventilated in time when gas leakage occurs to avoid the occurrence of combustion and explosion. The results of this study can provide a theoretical basis for the safe operation of hydrogen-doped natural gas buried pipelines.关键词：numerical simulation;hydrogen-doped natural gas buried pipelines;leakage and diffusion;hydrogen doping ratio;explosion limit- 19
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发布时间：2024-09-29 -
摘要：As hydrogen energy, a clean energy source, is to be developed and utilized on a large scale, the construction of long-distance hydrogen pipelines and related stations along the route is also increasing. To study the dispersion patterns of hydrogen leakage under different conditions, a three-dimensional FLACS model of the hydrogen station was established. Simulations of hydrogen leakage and dispersion were conducted under different leakage pressures, leakage apertures, and leakage temperatures in the presence of obstacles. The dispersion ranges of flammable gas clouds were compared, and the influencing factors were analyzed. The results show that obstacles cause changes in the direction of hydrogen leakage, leading to a rapid increase in the dispersion range. In scenario 7, within 7 s (8 s to 15 s), the area of the flammable gas cloud rapidly increases to 73.3% of the entire station area. The increase of leakage pressure and leakage aperture both result in a larger dispersion range of the flammable gas cloud. For low-pressure leakage at 4 MPa, the change in leakage aperture has a more significant impact, while for large aperture leakage at 100 mm, the change in leakage pressure has a more significant impact. When the leakage temperature increases from 293 K to 353 K, the thermal motion of hydrogen molecules accelerates, but the change in leakage temperature does not significantly affect the dispersion range of the gas cloud. This study can provide a reference for the prevention and control of leakage accidents in hydrogen station.关键词：hydrogen station;leakage dispersion;simulation;obstacles;flammable gas cloud;dispersion range- 10
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发布时间：2024-09-29
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