最新刊期
卷 49 ， 期 10 ， 2024
-
摘要：Carbon nanotubes (CNTs) have been a research interest in the field of nanotechnology since their discovery due to their ideal atomic space geometry, high electron mobility and excellent nanoscale size effect. Researchers have conducted in-depth researches on the theoretical model of carbon nanotubes and explored their structures, mechanical properties and electronic structures through experiments. Different kinds of defects are typically introduced during the growing process of carbon nanotubes since they are subject to uncertain factors including kinetics and thermodynamics, and thus functional modification of carbon nanotubes has become a major way to overcome their limitations. By summarizing the studies on modification of carbon nanotubes reported at home and abroad, the structural properties of carbon nanotubes, functionalization methods, grafting groups, and the promotion on the activity of carbon nanotubes by different functional selective agents in a controlled system were elaborated and analyzed. The results show that relying on specific backbone structure of carbon nanotubes, the introduction of functional groups or materials can significantly affect the physicochemical properties and surface activities of carbon nanotubes and promote their applications in a wider range of fields. In the future, achieving high-yield preparation and highly functional modification of ultrapure carbon nanotubes are directions that needs to be focused on.关键词：carbon nanotubes;structural characteristic;controlled modification;functional modification- 67
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The synthesis of higher alcohols from syngas is of great practical importance, and the construction of catalysts is the key to this technology. CuFe and zirconia with rich oxygen vacancies components (ZrO2-OV) were prepared by sodium carbonate co-precipitation and oxalic acid gel precipitation, respectively. A series of composite catalysts CF-Z-n (CF, Z and n stand for CuFe, ZrO2-OV and the mass ratio of the two, respectively) were prepared by physically milling and mixing the two components. The series of catalysts can effectively improve the distribution of higher alcohols in alcohol products. The physicochemical properties of the catalysts were characterized by EPR, N2 adsorption/desorption, XRD, TEM, XPS, H2-TPR and CO-TPSR-MS, and the reaction performances of the catalysts for preparation of higher alcohols by syngas catalytic reforming was investigated. The results show that ZrO2 with rich oxygen vacancies promotes CO activation. After physically mixing ZrO2 with rich oxygen vacancies and CuFe catalyst, a high-carbon and hydrogen-poor chemical environment is formed on the catalyst surface, which facilitates the conversion of CO and generation of higher alcohols. The catalytic performance of the composite catalyst can be optimized by varying n values. Under the reaction conditions of 260 ℃, 5 MPa and space velocity of 4000 h-1, the CO conversion rate of CF-Z-8 is 23.5%, the selectivity of total alcohols of CF-Z-8 is 15.0%, and the mass proportion of higher alcohols can reach 96.1%.关键词：CuFe catalysts;oxygen vacancies;ZrO2;syngas;higher alcohols- 121
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：In order to solve the problems of high diffusion resistance and high synthesis cost of microporous Silicalite-1 molecular sieves, hierarchical Silicalite-1 molecular sieves were synthesized by seed induction method under low dosage of template agent (n(TPA+):n(Si) = 0.01, TPA+ is tetrapropylammonium ion). The molecular sieves were characterized by XRD, FT-IR and N2 adsorption/desorption, and their catalytic performances in methanol to propylene were studied. The results show that for the molecular sieves prepared by one stage crystallization, when the mass fraction of seed in synthesized gel is 10% and the molar ratio of sodium fluoride to Si is 0.8, the obtained molecular sieve (S-110-0.01-NH4F0.8) has an ideal structure, and its mesoporous pore capacity is 0.120 cm3/g. For the molecular sieve prepared by two-stage crystallization, when the crystallization time of the low-temperature phase is 6 h, the mass fraction of seed in synthesized gel is 10%, the molar ratio of urea to Si is 0.5, the obtained molecular sieve (SL-110-0.01-6-CH4N2O0.5) has an ideal structure, and its mesoporous pore capacity is 0.220 cm3/g. Under the reaction conditions of 450 ℃ and methanol mass space velocity of 5.53 h-1 for 30 min to 40 min, SL-110-0.01-6-CH4N2O0.5 exhibits relatively good catalytic performance with the propylene yield of 14.65%, m(propylene):m(ethylene) of 4.6 and the regeneration period of 2600 min.关键词：hierarchical Silicalite-1 molecular sieves;seed;methanol to propene- 23
- |
- 0
- |
- 0
发布时间：2024-10-28 -
Study on electrocatalytic performances of Ag/Ag2CO3 wide potential catalysts for CO2 reduction to CO
摘要：Electrocatalytic carbon dioxide reduction reaction (CO2RR) faces challenges of poor stability and low selectivity, and the development of high-performance CO2RR catalysts with a wide potential range has become a research hotspot. An in situ preparation method was adopted, where CO2RR catalyst I-Ag/Ag2CO3 was formed in situ on a silver foil substrate during linear sweep voltammetry in a KHCO3 electrolyte. I-Ag/Ag2CO3 was characterized by XRD, XPS, Raman, SEM and TEM. The electrocatalytic performance of I-Ag/Ag2CO3 was investigated in an H-type electrolytic cell. The results show that I-Ag/Ag2CO3 exhibits efficient catalytic performance for CO2 reduction to CO in a wide potential range (from -0.78 V to -1.78 V). The maximum CO partial current density of the catalyst is up to 53 mA/cm2, and the CO Faradaic efficiency (FECO) of the catalyst is higher than 80% in a wide potential range of 1 V, and the maximum FECO is 96% at -1.18 V (the reference electrode is a reversible hydrogen electrode, the same below) and can maintain no less than 90% within 20 h at -1.0 V. Through structure-performance relationship analysis, it is revealed that the special heterostructure formed between Ag and Ag2CO3 on I-Ag/Ag2CO3 obtained via the in situ preparation method. The special heterostructure reduces the resistance of electron transfer to CO2, and enhances the rate of the rate-determining step of CO2RR process.关键词：Ag/Ag2CO3;electroreduction;CO2;CO;wide potential catalysts- 11
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Supercapacitors, as clean electrochemical energy storage devices, have immense potential in the field of renewable energy storage and conversion. Carbon materials, known for their adjustable micro-porous structures and excellent chemical stability, are widely used in electrochemical energy storage. Concurrently, biomass, as a renewable precursor for preparing carbon-based materials, boasts advantages such as abundant availability, easy access, environmental friendliness and low cost. However, the complex chemical composition of biomass-derived carbon precursors results in significant variations in microstructure and surface properties of the derived carbon materials, posing certain challenges for their practical application in supercapacitors. The current states of research on biomass-based carbon materials for supercapacitors were reviewed. The influences of common compositions of biomass and the primary fabrication techniques of biomass-based carbon materials on the microstructures of the biomass-based carbon materials were summarized, and the applications of biomass-based carbon materials with different dimensional structures in supercapacitors were introduced. The future prospects of biomass-based carbon materials for supercapacitors were discussed, aiming to provide theoretical insights for the structural and surface functional control of biomass-based carbon materials, and the development of low-cost and high-performance electrode materials for supercapacitors.关键词：biomass;pyrolysis;carbon materials;electrochemistry;supercapacitors- 44
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The clean and efficient utilization of coal is of great significance for achieving the dual carbon goals. Five types of coking coal (Guanyintang coking coal, Matou coking coal, Wugou fat coal, Xiaoxian fat coal and Yanzhouxi gas coal) were pyrolyzed into coke using a self-made coke oven, and coal samples at different temperature ranges were extracted. The carbon structures of coal samples were investigated by combining characterization methods such as Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The FTIR results show that the aromatic structures of the five types of raw coal are mainly benzene ring disubstituted and tetrasubstituted, with relative contents exceeding 50%. As the temperature increases, the relative content change of benzene ring disubstituted in the five types of coal samples decreases to varying degrees, while the relative content of benzene ring tetrasubstituted and pentasubstituted shows a two-stage pattern. The fatty structures of five types of raw coal are mainly composed of methyl and methylene. As the temperature increases, the relative contents of methylene in Guanyintang coking coal, Matou coking coal, Wugou fat coal and Xiaoxian fat coal decrease by 18.85%, 13.75%, 16.50% and 12.65%, respectively. The relative content of methylene in Yanzhouxi gas coal reaches the lowest at 450 ℃, followed by a rapid decrease in methenyl content from 42.11% to 22.87% after 450 ℃. The FTIR structural parameters of the five coal samples were calculated, and it is found that the aromatic carbon and hydrogen rates of the coal samples significantly increase during the stage from 450 ℃ to 550 ℃, while alkyl chain length rapidly decreases. The XRD results show that as the temperature increases, the interplanar spacings of coking coal and fat coal decrease to 0.344 nm to 0.346 nm, while the interplanar spacing of gas coal only decreases by 0.007 nm. The lateral dimensions of the five coal samples show a trend of first decreasing and then increasing, while stacking heights show an increasing trend. The carbon structure parameters of coking coal and fat coal show significant changes, with the aromaticity of coking coal increasing to around 0.82, fat coal increasing to around 0.73, and gas coal having an aromaticity of only 0.57.关键词：coal pyrolysis;colloidal layer;fourier transform infrared spectroscopy;X-ray diffraction;carbon structure- 19
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Desulfurization of fuel gases such as natural gas, biogas and coal gas is an important step to achieve their high-value utilization, and is of great significance for clean and efficient utilization of energy. Hydrogen sulfide (H2S) is a sulfur-containing gas that is toxic and corrosive, posing great hazards to industrial equipment, ecological environment and human health. The dry desulfurization process has the advantages of high desulfurization accuracy, wide application range, simple equipment, etc. In particular, the room temperature dry desulfurization process has attracted widespread attention due to its low desulfurization cost and high efficiency. The research progress of three desulfurizers for room temperature dry desulfurization was reviewed, namely activated carbon, metal oxides, and zeolite molecular sieves. The preparation methods, desulfurization mechanisms, operating conditions, advantages and disadvantages of the three desulfurizers were analyzed. And the research progress of the desulfurizers for room temperature dry desulfurization was summarized to provide reference for related research.关键词：dry desulfurization;activated carbons;metal oxides;zeolite molecular sieves- 37
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：In view of the environmental pollution and easy poisoning problems of commercial vanadium-titanium denitrification catalysts, a non-toxic and environmentally friendly single-metal copper catalyst was used and the addition of additive Ni was used to improve its denitrification performance. Based on density functional theory (DFT), the effect of additive Ni on the catalytic reduction of NO by NH3 on Cu(111) surface was investigated. By analyzing the adsorption of reactive species, reaction mechanism and electronic structure on the catalysts surface, the catalytic activities of Cu(111) surface before and after additive Ni doping were compared. The results show that the adsorption effect of all reactive species on the CuNi(111) surface is better than that on the Cu(111) surface. The energy barriers for the three elementary reactions occurring on the CuNi(111) surface are lower than those on the Cu(111) surface, among which the energy barrier for the rate-determining step (NH2NO → N2 + H2O) decreases by 63.6 kJ/mol, indicating that the catalytic activity of CuNi(111) surface is significantly higher. Compared with the Cu(111) surface, the d-band center of the CuNi(111) surface is closer to the Fermi level, indicating that the doping of additive Ni enhances the electronic activity of the Cu(111) surface, thereby improving its catalytic activity.关键词：Cu surface;additive Ni;denitrification;density functional theory- 16
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Surface modification by promoters is one of the classic methods to improve the thermal stability, reducibility, and low-temperature activity of cerium-based materials and their supported Pd-only three-way catalysts. Revealing the mechanism of surface modification by promoters is of practical significance for the development of high-performance CeO2-ZrO2-Al2O3 (CZA) materials to meet the increasingly strict regulations on gasoline vehicle exhaust emission and to solve the exhaust pollution. On the basis of the promoting effects of Pr6O11 on improving the low-temperature reducibility of CZA materials, the effects of different content of Pr6O11(0, 3%, 5%, 7%, and 9%, mass fraction) on the redox performance and thermal stability of CZA materials were further studied. The characterization results of N2 adsorption/desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR) and oxygen storage capacity show that the surface modification of CZA by Pr6O11 can reduce the driving force of CeO2-ZrO2 (CZ) sintering and thus inhibit the growth of nanoparticles. At the same time, the introduction of Pr6O11 also promotes to produce more oxygen vacancies in the material, thus improving its reducibility and oxygen storage performance. Among them, when the content of Pr6O11 is 5%, the modified CZA exhibits the best thermal stability, redox performance and oxygen storage performance. After aging at 1000 ℃ for 4 h, it exhibits the highest specific surface area (85 m2/g) and pore volume (0.33 mL/g), the smallest crystal size of CZ (6.9 nm), the lowest reduction temperature (532 ℃) and the highest oxygen storage capacity of 109 μmol/g at 400 ℃. Therefore, the modified CZA supported Pd-only three-way catalyst exhibits the optimal catalytic activity, with the t50 (required temperature at the pollutant conversion rate of 50%) of CO, NO, C3H8 and C3H6 reduced by 6 ℃, 15 ℃, 18 ℃ and 6 ℃, respectively, compared to the unmodified catalysts. In summary, the low-temperature activity of Pd-only thee-way catalysts can be improved by adding an appropriate amount of Pr6O11 to the CZA support, which is simple, economical, and has great application prospects.关键词：exhaust purification;surface modification;CeO2-ZrO2-Al2O3;Pr6O11- 26
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Carbon dioxide (CO2) capture, utilization and storage technology is one of the main technological ways to achieve the carbon peaking and carbon neutrality goal. Alcohol amine method to absorb CO2 in flue gas is the most mature and widely used CO2 capture process, which has been commonly used in the industrial decarbonization of flue gas. Absorbents are the core elements of the alcohol amine method, and the selection of suitable absorbents has become a key research direction at present. The classification and working principles of alcohol amine absorbents and the process flow of CO2 absorption in flue gas were reviewed. The performances of a binary mixed absorption system of ethanolamine (MEA) and methylenediamine (MDEA) as absorbents and MEA and MDEA as main absorbents respectively were analyzed in depth. A series of optimization measures, including adding activators and additives into the alcohol amine solution, using new absorbents, were proposed to address the drawbacks of low regeneration efficiency, high desorption energy consumption, easy corrosion of absorbents and high recovery costs in the alcohol amine method to absorb CO2 in flue gas. Finally, the development of the alcohol amine method to absorb CO2 in flue gas was discussed, so as to provide a reference for the development of high-efficiency alcohol amine absorbents.关键词：CO2;carbon capture;alcohol amine method;MEA;MDEA;flue gas- 66
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The phase change absorbents have received a lot of research attentions because of their excellent ability to reduce the energy consumption during regeneration. Density functional theory has been widely used to calculate the absorption and desorption performances of phase change absorption system, which provides an effective explanation for the reaction process and phase change phenomenon. However, there is currently no systematic introduction about the application of hydrogen bond, dipole moment, reaction energy barrier and electron cloud density obtained by density functional theory in phase change absorption systems. The absorption mechanism, phase change mechanism and desorption mechanism of phase change absorbents were briefly described. The latest research progress of density functional theory applied to novel phase change absorbents was systematically reviewed from four aspects: hydrogen bond, dipole moment, reaction energy barrier and electron cloud density. Improved methods were proposed to address the shortcomings of density functional theory in existing applications, and building a correlation model between calculation results and absorption performance was also recommended to guide the design of phase change absorbents.关键词：CO2;phase change;absorption;density functional theory;reaction mechanism;quantum chemistry- 23
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Dimethyl ether is an ideal engine clean fuel. Under the background of carbon neutrality, the preparation of dimethyl ether from CO2 has been actively carried out at home and abroad. The methods of catalytic hydrogenation of CO2 to dimethyl ether mainly include one-step and two-step method. The thermodynamic analysis of the processes based on different methods can provide reference for process optimization and related catalyst development. Process one was constructed based on the one-step method, and process two (with methanol as the intermediate) and process three (with CO as the intermediate) were respectively constructed based on the two-step method. Under the condition that the composition of raw gas is n(H2):n(CO2) = 3:1, the effects of reaction temperatures (from 150 ℃ to 350 ℃) and reaction pressures (from 1.0 MPa to 9.0 MPa) on the corresponding equilibrium constants, CO2 equilibrium conversion rates and dimethyl ether yields in each process were studied. The results show that at 150 ℃ and 9.0 MPa, the process one is superior to the other two processes, with CO2 equilibrium conversion rate of 94.61% and dimethyl ether yield of 85.31%. For the two-step method process with CO as the intermediate, the development of high efficiency reverse water gas low temperature catalyst should be strengthened in the future. For the one-step method process, the composite system coupling reaction system and separation system is the main research direction in the future.关键词：carbon dioxide;catalytic hydrogenation;dimethylether;process analysis;thermodynamic calculation- 49
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The content (mole fraction) of ethane and helium in the natural gas of a domestic gas field is increasing year by year, and the recovery value is highlighted. A process of helium extraction and ethane co-production by nitrogen double expansion refrigeration was proposed. The process was simulated by HYSYS software, and the influences of the key parameters of the process (temperature of the cryogenic separator, reflux ratio of the demethanizer top, feed temperature of the secondary helium extraction tower, reflux ratio of the secondary helium extraction tower top, inlet pressure of the nitrogen expansion end, outlet pressure of the nitrogen expansion end and flow rate of the nitrogen refrigerant) on the process indexes were investigated. Based on the optimisation theory, the Back Propagation (BP) neural network algorithm was used to optimise the key parameters with the objectives of minimising the total energy consumption of the unit when the C2 yield and the secondary crude helium concentration were maximised. The results show that the total energy consumption of the unit is mainly affected by temperature of the cryogenic separator, the outlet pressure of the nitrogen expansion end and the flow rate of the nitrogen refrigerant, and the C2 yield is mainly affected by temperature of the cryogenic separator and the reflux ratio of the demethanizer top, and the helium yield is mainly affected by the feed temperature of the secondary helium extraction tower. The optimal combination of key parameters is as follows: Temperature of the cryogenic separator is -95.30 ℃, flow rate of the nitrogen refrigerant is 1549.22 kmol/h, inlet pressure of the nitrogen expansion end is 3.25 MPa, outlet pressure of the nitrogen expansion end is 0.44 MPa, reflux ratio of the demethanizer top is 0.13, feed temperature of the secondary helium extraction tower is -150.57 ℃, and eflux ratio of the secondary helium extraction tower top is 0.80. Compared with the pre-optimization, the total energy consumption of the optimized unit is reduced by 1.46%, the C2 yield is increased by 5.64%, and the secondary crude helium concentration (mole fraction) is increased by 1.81%.关键词：nitrogen double expansion refrigeration;helium extraction from natural gas;ethane recovery;co-production process;parameter optimization;BP neural network algorithm- 36
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The Rankine cycle can convert liquefied natural gas (LNG) cold energy into electrical energy, which is an effective cold energy recovery and utilization technology. Based on engineering practice, the lowest pressure in the LNG cold energy power generation system was set to be higher than normal pressure, and the effect of circulating working fluids on system performance was explored. Seven commonly used working fluids were selected as candidates, with the objective function of maximizing the net output power of the system. Under the same operating conditions, three common cold energy power generation systems, namely single-stage combined cycle (CC), cascade combined cycle (CCC) and parallel combined cycle (PCC), were optimized. The differences in system performance and their reasons when selecting different working fluids were analyzed, and the effect of direct expansion process on working fluid selection was explored. The results show that the optimal working fluids for CC, CCC and PCC systems are CH2F2, C2H6 + C3H8 and C2H4 + C3H8, respectively. When selecting the optimal working fluid, the CCC system reduces irreversible energy loss within the system by effectively segmenting the utilization of LNG cold energy, resulting in relatively optimal performance. Compared with CC and PCC systems, the thermal efficiency of CCC system increases by 54.8% and 35.4%, and the required heat exchange area does not significantly increase. The presence or absence of direct expansion does not affect the selection of working fluids within the system, while the absence of direct expansion can lead to a slight decrease in the maximum net output power of the system.关键词：LNG cold energy power generation;genetic algorithm optimization;Rankine cycle;working fluid selection;system performance comparison;direct expansion- 31
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：Large-scale carbon capture requires the transportation of carbon dioxide (CO2) through pipelines. The formation of CO2 hydrate can affect the safety of pipeline transportation. Glycine has a strong disturbing effect on water molecules and can inhibit the formation of CO2 hydrate. Using a high-pressure visual reaction kettle as the experimental platform, the formation of CO2 hydrate was studied in single glycine systems and their composite systems with polyvinylpyrrolidone (PVP K90) under the conditions of temperature 275.15 K, pressure 3.5 MPa and stirring speed 700 r/min. The results show that the inhibition effect is best in the single system when the glycine concentration (mass fraction) is 4.0%, and the induction time is 439.02% of that of the pure water system. The highest point of the temperature rise during hydrate formation shows a trend of first decreasing and then increasing with the increase of glycine concentration. The compounding of glycine and PVP K90 can significantly prolong the induction time of hydrate formation and lower the highest point of temperature rise. Among them, the inhibition effect of the compounding 4.0% glycine and 0.7% PVP K90 is the best. Compared with the single system of 4.0% glycine, the induction time is extended by 105.43% and the highest point of temperature rise is lowered by 0.15%. This study can provide a reference for the development of hydrate inhibitors.关键词：kinetic inhibitor;polyvinylpyrrolidone;glycine;carbon dioxide;hydrate- 20
- |
- 0
- |
- 0
发布时间：2024-10-28 -
摘要：The separation and purification of coalbed methane (CBM) are crucial for ensuring safe production in mines and achieving carbon neutrality goals. Using hydrate separation technology, experiments were conducted to separate high-concentration CBM (with methane volume fraction of 60%) in sodium dodecyl sulfate (SDS), oil-water emulsion and pure water systems under four different driving pressures (1 MPa, 2 MPa, 3 MPa and 4 MPa). The results indicate that the growth rate of CBM hydrate increases continuously with the driving pressure in all three systems. The addition of SDS and oil-water emulsion further increases the hydrate growth rate. Under different driving pressures, the methane recovery rates after separation in pure water, SDS and oil-water systems are 10.02% to 11.75%, 31.00% to 43.36% and 21.68% to 24.36%, respectively. Compared to the pure water system, the methane recovery rate is 3 to 4 times higher in the SDS system and approximately 2 times higher in the oil-water emulsion system. The methane recovery rate increase with the driving pressure in all three systems. However, the separation factors of SDS and oil-water emulsion systems decrease at driving pressures of 3 to 4 MPa, indicating increased separation difficulty. Therefore, 3 MPa is identified as the optimal driving pressure. At this pressure, the methane volume fraction after purification in the SDS and oil-water emulsion systems reach 81.13% and 82.32%, respectively.关键词：coalbed methane hydrate;hydration separation;driving pressure;sodium dodecyl sulfate;oil-water emulsion- 20
- |
- 0
- |
- 0
发布时间：2024-10-28
- Postal code：610225
- Tel：028-85964717 Email：dthxyhg@swchem.com
- Technical support is provided by Beijing Founder electronics co., LTD 蜀ICP备12008600号-10
蜀公网安备51012202001533 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
- Total Visits：128596 Visits Today：713
0