最新刊期
卷 49 ， 期 11 ， 2024
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摘要：Fossil fuels have an important contribution to human society, but the large amount of CO2 emissions has a negative impact on the global climate. CO2 hydrogenation to methanol not only effectively reduces the concentration of CO2 in the atmosphere, but also provides high value-added chemicals. A range of non-precious metal (Cu)-based, precious metal (Pd)-based and bimetallic oxide catalysts have been used for CO2 hydrogenation to methanol. However, conventional Cu-based catalysts suffer from harsh reaction conditions and easy sintering as well as agglomeration of active sites. Pd-based catalysts are more resistant to sintering and have excellent reactivity at low temperatures, but noble metals have weak adsorption of CO2, and CO2 is difficult to be activated at low temperatures. Bimetallic oxide catalysts (mainly ln2O3-based and ZrO2-based catalysts) have excellent catalytic performance and good stability. Among which, the stability of In2O3 alone is poor, and the active phase In2O3-x of In2O3-based catalyst is easily deactivated by excessive reduction to form metal In, which needs to be doped with other modified elements to further improve its stability and activity. The catalytic performance of ZrO2 alone for CO2 hydrogenation to methanol is not ideal, and its catalytic performance needs to be improved by interacting with other metals or metal oxides. Rare earth elements (La, Ce and Y) as modified elements or their oxides as catalyst carriers can effectively regulate the surface acidity and alkalinity of catalysts, the dispersion of active phases and their specific surface area and metal-carrier interactions, etc., so as to improve the adsorption and activation capacity of catalysts for CO2, increase the selectivity of products and enhance the stability of the catalysts. The modification effects of La, Ce and Y on Cu-based, Pd-based and bimetallic oxide catalysts were reviewed, in order to provide reference for the development and application of catalysts modified by rare earth elements for CO2 hydrogenation to methanol.关键词：CO2 hydrogenation;methanol;rare earth elements;modification effects- 73
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发布时间：2024-11-25 -
摘要：The extensive use of fossil fuels have led to massive CO2 emissions, causing a series of climate issues. Converting CO2 into methanol can achieve CO2 emission reduction and resource utilization, making it a current research hotspot. CO2 hydrogenation to methanol catalysts have been extensively studied, but issues such as low catalytic activity, poor methanol selectivity and catalyst deactivation caused by water produced during the reaction, which slows the reaction, still exist. A comprehensive understanding of the relationship between the physicochemical properties of catalysts and their catalytic performance is crucial for the development of efficient and stable catalytic systems. Three reaction mechanisms for CO2 hydrogenation to methanol were first introduced. Then the research progress on the impact of the physicochemical properties of CO2 hydrogenation to methanol catalysts on their catalytic performances was reviewed, including metal specific surface area and porosity, metal particle size and dispersion, oxygen vacancy, acid-basicity, metal-support interaction and reducibility. Finally, the future researches for CO2 hydrogenation to methanol catalysts were prospected.关键词：CO2 hydrogenation;methanol catalysts;physicochemical properties;catalytic performances- 24
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发布时间：2024-11-25 -
摘要：The conversion of CO2 to CO via reverse water gas transformation (RWGS) reaction can present a promising strategy to mitigate the environmental impact of CO2 emission. However, the RWGS reaction encounters notable challenges, such as the efficient activation of CO2 and the suppressed generation of CH4. Different doping contents (mass fractions, the same below) of Sn were introduced into 5Co/ZrO2 (Co mass fraction of 5%) for modification, and 5CoxSn/ZrO2 (x = 1, 3 or 5, corresponding to Sn doping content of 1%, 3% or 5%) catalysts were prepared. The experimental parameters for evaluating the catalytic performances of 5Co/ZrO2 and 5CoxSn/ZrO2 in CO2 hydrogenation reaction were adjusted and screened to explore the influence of Sn additives on the active components and catalytic performance. Among them, 5Co5Sn/ZrO2 shows the best RWGS catalytic performance. After pre-reduction for 2 h at 600 ℃, under reaction conditions of temperature of 500 ℃, pressure of 0.1 MPa and space velocity of 36000 mL/(g·h), the CO2 conversion rate reaches 11.9%, and the CO selectivity is 99.4%. The role of Sn promoter in CO2 hydrogenation reaction was comprehensively analyzed by characterization methods such as XRD, H2-TPR, and H2-TPD. The results indicate that the introduction of Sn regulates the CO2 hydrogenation reaction from methanation to RWGS. After reduction, Sn and Co species form Co-Sn alloy, and new active sites reduce the ability of the catalyst surface to adsorb CO2, H2 and CO. Compared with 5Co/ZrO2, 5Co5Sn/ZrO2 shows weaker adsorption and activation ability of H2 and much lower adsorption amount of CO2 and CO, which reduces the activity of CO2 hydrogenation and inhibits the deep CO2 hydrogenation, resulting in a decrease in the catalytic performance of the catalyst, a decrease in CH4 selectivity and an increase in CO selectivity to about 100%.关键词：CO2 hydrogenation;RWGS;selectivity switch;Co-Sn alloy;chemisorption- 44
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发布时间：2024-11-25 -
摘要：In order to promote the transformation of China’s energy structure and alleviate the pressure of energy shortage, it is of great practical significance to partially oxidize natural gas (methane) with abundant reserves into syngas. The catalysts commonly used in this process is the Ni-based catalysts, which are prone to carbon deposition and inactivation. In-depth study of the catalytic mechanism on the surface of Ni-based catalysts can help to solve this problem. Based on the first-principles calculation method of density functional theory, the most favorable adsorption configuration of related species on Ni(111) in methane partial oxidation was determined, and the transition states of each element reaction in the reaction process were searched by the dimer method, and the whole process of methane partial oxidation on Ni(111) to CO was analyzed. The results show that the adsorption energy of CH* on Ni(111) is 6.98 eV, and the activation energy of CH2* dehydrogenation to CH* is 0.28 eV, which is much lower than that of CH* dehydrogenation (1.29 eV), indicating that CH* can exist in large quantities on the Ni surface, and its change can affect the whole reaction pathway. In the whole process of methane partial oxidation to CO, the activation energy of CH* to CO* oxidation by OH* is 1.48 eV, which is 0.11 eV lower than that of C* direct oxidation by O* to CO (1.59 eV), so the formation of OH* is more conducive to CO formation. In the process of oxidation of CH* by OH* to form CO*, the conversion process of CHOH* → COH* → CO* is undertaken, and the activation energy of the whole conversion process is 0.91 eV. The activation energy of the conversion procces (CHOH* → CHO* → CO*) is 0.73 eV, so CHOH* is more inclined to dehydrogenation to form CHO* and then CO*, and the optimal reaction path of methane partial oxidation to CO* is CH4* → CH3* → CH2*→ CH* + OH* → CHOH* → CHO* → CO*.关键词：OH*;methane partial oxidation;Ni(111);density functional theory- 29
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发布时间：2024-11-25 -
摘要：Key chemical p-tert-butylethylbenzene (p-TBEB) has broad application prospects in engineering plastics, high-speed rail aviation, electronic information and so on. At present, the process of producing p-TBEB through alkylation has drawbacks, such as limited raw materials and rapid catalyst deactivation. There is also a lack of systematic research on the performance of different molecular sieves with different configurations for the preparation of p-TBEB. HBeta, HUSY, HMOR, HMCM-22 and HZSM-12 hydrogen molecular sieves with BEA, FAU, MOR, MWW and MTW topological structures were selected, and their structures and properties were characterized by XRD, SEM, NH3-TPD and N2 physical adsorption/desorption. The results show that the selected molecular sieves are all pure phase molecular sieves with typical morphology and acid distribution. The catalytic performances of different topological structure molecular sieves for the liquid-phase alkylation of ethylbenzene and isobutylene to prepare p-TBEB was systematically studied under the reaction conditions of reaction temperature of 200 ℃, reaction pressure of 2.5 MPa, molar ratio of ethylbenzene to isobutylene feedstock of 4.0 and isobutylene mass space velocity of 1.0 h-1. The results show that the acid amount has a low correlation with the reaction activity and target product selectivity of the molecular sieve, and the pore structure is the key factor affecting its alkylation performance. Compared with several other molecular sieves, the HZSM-12 hydrogen molecular sieve with one-dimensional twelve-membered ring pores not only maintains a high ethylbenzene conversion rate (about 20%), but also has high target product selectivity, making it the most preferred molecular sieve catalytic material for the reaction of ethylbenzene and isobutylene to prepare p-TBEB.关键词：zeolites;ethylbenzene;isobutene;alkylation;p-tert-butylethylbenzene- 34
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发布时间：2024-11-25 -
摘要：In order to address the issue of poor stability of loaded Ru catalysts in the hydrodeoxygenation reaction of phenolic compounds, a series of hollow mesoporous core-shell catalysts, Ru@Alx-mSiO2 (x = 0.5, 1.0, 1.5 or 2.0), with varying Al loadings (mass fractions) were prepared by selective etching under alkaline conditions with Ru-containing silica microspheres (Ru@SiO2) as the precursor and sodium meta-aluminate (NaAlO2) as the aluminum source. The microstructures and physicochemical properties of the catalysts were characterized by TEM, HAADF-STEM, XRD, N2 adsorption/desorption, NH3-TPD and H2-TPD. The catalytic performances of Ru@Alx-mSiO2 catalysts were investigated using phenol hydrodeoxygenation to prepare benzene as a model reaction. The results show that the incorporation of Al into Ru@mSiO2 under the reaction conditions of 60 ℃ and 2.0 MPa can significantly improve the selectivity of benzene. This is attributed to the fact that the Al loading provideds abundant acidic sites, which can not only assist the dissociation of H2 from the metal Ru to increase the phenol hydrogenation activity, but also enhance the deoxygenation of phenol and thus improve the benzene selectivity. Among all the catalysts, Ru@Al1.0-mSiO2 exhibits the highest phenol conversion (80.5%) and benzene selectivity (96.5%), which is attributed to the synergistic effect between the Ru metal and the silicoaluminate shell layer. Furthermore, the hollow mesoporous silica-aluminate shell layer exhibites a domain-limiting protective effect, and Ru@Al1.0-mSiO2 still exhibits excellent stability in multiple catalytic cycle hydrodeoxygenation experiments.关键词：phenolic compound;Ru-based core-shell catalysts;phenol;hydrodeoxygenation;benzene- 21
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发布时间：2024-11-25 -
摘要：The selective conversion of biomass and its derivatives to lactic acid is one of the important ways to realize the high value utilization of such resources, and the role of heterogeneous catalysts in the selective conversion reaction is crucial. The construction of heterogeneous catalysts for the selective conversion of biomass and their derivatives (including glycerol, xylose, fructose, glucose, starch and cellulose and raw biomass, etc) to lactic acid was reviewed, and the structure-activity relationships of different catalysts were discussed. The influences of the compositions, structures and active sites of heterogeneous catalysts on the selective conversion of different reaction materials to lactic acid were analyzed, and the future research direction of related catalysts was prospected.关键词：biomass;lactic acid;heterogeneous catalysis;catalysts;structure-activity relationships- 84
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发布时间：2024-11-25 -
摘要：The preparation of high specific surface area activated carbon by KOH activation method usually requires a large amount of KOH consumption. In order to improve the utilization efficiency of KOH, a method based on intercalation and de-intercalation of K (hereinafter referred to as “K recycle”) for preparing high specific surface area activated carbon and co producing H2 from activation of petroleum coke with KOH was developed. During the heating activation process, KOH reacted with carbonaceous raw materials and converted into K, K2O and K2CO3 and produced H2, while K2CO3 can continue to react to generate K and K2O. During the cooling de-intercalation process, water vapour as the de-intercalation reagent was introduced to react with the intercalated K, free state K and K2O to generate KOH and H2. The regenerated KOH can react again with the carbonaceous raw materials during the secondary heating activation process, forming the K recycle. The effects of different carbonaceous raw materials (petroleum coke and graphite), activation agent KOH and its activation intermediate K2CO3 on the gas evolution during activation process and the pore structure properties of activated carbon were investigated in a horizontal boat reactor. Based on this, the K recycle mechanism was analyzed. The results show that the efficiency of K recycle and H2 production vary with the carbonaceous raw materials and activation agents. The reactivity of petroleum coke is much higher than that of graphite, and the activation ability of KOH is better than that of K2CO3. In the activation process of petroleum coke with KOH, the conversion rate of KOH reaches 80%, while that of K2CO3 is only 18.5%, indicating that the efficiency of K recycle is determined by the conversion of K2CO3.With petroleum coke as carbonaceous raw materials and KOH as activation agent, under the conditions of activation temperature 800 ℃ and de-intercalation temperature 250 ℃, 4.5 g dried petroleum coke and 13.5 g KOH are subjected to secondary intercalation and de-intercalation, resulting in activated carbon with the specific surface area of 2808 m2/g and co producing 1403 mL/g H2 (1403 mL H2 produced by 1 g petroleum coke).关键词：activated carbon;petroleum coke;K recycle;KOH;hydrogen- 34
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发布时间：2024-11-25 -
摘要：Compared with traditional combustion methods, solid fuel low-carbon combustion technologies can not only improve energy efficiency, but also reduce environmental pollution to a certain extent. Currently, the mature solid fuel low-carbon combustion technologies include ammonia co-firing with coal, coal-biomass co-combustion, chemical looping combustion and oxygen-enriched combustion. Taking the ammonia mixing ratio of ammonia co-firing with coal, the biomass mixing ratio of coal-biomass co-combustion, the oxygen carrier and reaction conditions of chemical looping combustion, the reaction conditions and pollutant emissions of oxygen-enriched combustion as entry points, the current development status of solid fuel low-carbon combustion technology was summarized and its future development was prospected. Comparing the working conditions of different forms of coal combustion, it is found that the ammonia mixing ratio and biomass mixing ratio have a significant impact on the nitrogen oxides emissions during coal combustion, and even affect the operating environment and overall efficiency of the boiler. Chemical looping combustion and oxygen-enriched combustion can improve CO2 capture efficiency, promote carbon conversion, increase oxygen release rate, and thus increase chemical reaction rate.关键词：ammonia co-firing with coal;coal-biomass co-combustion;chemical looping combustion;oxygen-enriched combustion;pollutant control- 34
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发布时间：2024-11-25 -
摘要：Pipeline transportation is the most economical long-distance transportation method for liquid ammonia, and the standardization of liquid ammonia pipeline transportation technology is an important link to ensure the standardized construction, operation and maintenance of pipelines. However, there is relatively little information on liquid ammonia pipeline transportation technology in the current domestic standards. For this purpose, a systematic analysis was conducted on the current status of liquid ammonia pipeline construction at home and abroad, as well as the current technical standards for liquid ammonia pipeline transportation. The focus was on exploring the similarities and differences in the provisions of transportation processes, pipeline routes, pipeline (pipeline accessories, supports) design and ammonia transportation stations in relevant standards, and providing applicability suggestions. For the quality requirements, medium flow rate, pipe material selection, corrosion allowance and station protection facilities of liquid ammonia pipelines, reference can be made to standards such as GB/T 536, GB 50253, SY/T 7629, SH/T 3074 and ASME B31.4 (the United States), respectively. For the buried pipeline clearance of the liquid ammonia pipeline, regional classification, maximum spacing of isolation valve chambers, fire protection spacing at stations and safety relief, relatively strict standards and regulations related to oil and gas pipelines (GB 51142, GB50253, GB50160, and 29 CFR1910.11 (the United States)) can be referred to for implementation. Considering the differences in the toxic properties, diffusion characteristics and prevention and control measures between liquid ammonia and oil and gas, it is recommended to conduct risk assessment and prediction research on the diffusion and safe release of liquid ammonia leakage, and further demonstrate the spacing values and regulations applicable to liquid ammonia scenarios.关键词：liquid ammonia;pipeline transportation;standardization development;standard comparison- 109
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发布时间：2024-11-25 -
摘要：Silica-aluminum zeolite molecular sieve is widely used in adsorption field, and its hydrophilic and hydrophobic properties have great influence on adsorption properties. Howerer, the dynamic adsorption properties of water vapor in silica-aluminum zeolite molecular sieve under different conditions are still unclear. Beta molecular sieves (Beta-30, Beta-135 and Beta-679) with different silicon to aluminum ratios (n(SiO2)/n(Al2O3) = 30, 135 or 679) were used as research objects, and were characterized by XRD, FT-IR and TG, etc. Then the water vapor adsorption capacities and corresponding kinetics of Beta-30, Beta-135 and Beta-679 were analyzed under different temperatures and relative humidities (HR), respectively. The results show that Beta-679 has the lowest adsorption capacity when temperature is 25 ℃ or 35 ℃ and HR is less than 80%. The equilibrium rate of Beta-679 is the fastest when temperature is 15 ℃ and HR is 5% to 10%. When temperature is 15 ℃ and HR is 50% to 70%, the equilibrium rates of Beta-30, Beta-135 and Beta-679 show great difference (the equilibrium rate of Beta-135 is much smaller than that of Beta-30 and Beta-679).关键词：Beta molecular sieves;silicon to aluminum ratios;water vapor adsorption;dynamics- 26
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发布时间：2024-11-25 -
摘要：High purity ethylene can be obtained by the solid adsorption separation technology, which is of great significance to improve the quality of ethylene products. Mn-doped high-silica MFI zeolite (H-MFI-Mn) were modified by surface modification strategy to obtain P-modified H-MFI-Mn (H-MFI-Mn-P) and HCOOH-modified H-MFI-Mn (H-MFI-Mn-COOH and H-MFI-Mn-P-COOH), respectively. The prepared zeolites were characterized by XRD, SEM and N2 adsorption/desorption, etc. The ethane/ethylene adsorption separation performances of prepared zeolites were evaluated in mixed gas (V(ethane):V(ethylene) = 50:50). And the ethane/ethylene adsorption separation mechanisms of prepared zeolites were analyzed by UV-Vis and XPS. The results show that the micropore size (0.68 nm) and average pore size (2.70 nm) of H-MFI-Mn-P-COOH are significantly larger than the micropore size (0.55 nm) and average pore size (1.61 nm) of H-MFI-Mn. Compared with the specific surface area of H-MFI-Mn (446 m2/g), the specific surface areas (about 400 m2/g) of H-MFI-Mn-P, H-MFI-Mn-COOH and H-MFI-Mn-P-COOH decrease. H-MFI-Mn-P-COOH shows better ethane/ethylene adsorption separation performance with ethane dynamic equilibrium adsorption capacity of 1 mmol/g and ethane/ethylene dynamic separation selectivity of 2.08. Compared with H-MFI-Mn, Mn3+ and Mn2+ in H-MFI-Mn-P-COOH accounted for higher proportions in total Mn ions, indicating that P-modification + HCOOH-modification can weaken the electron transfer performance of Mnδ+ species in the zeolite structure, and then inhibit the ethylene adsorption performance of H-MFI-Mn-P-COOH.关键词：high-silica MFI zeolites;ethane/ethylene adsorption separation;surface modification- 41
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发布时间：2024-11-25 -
摘要：As a new type of CO2 capture technology, moisture swing adsorption has the characteristics of capture-release CO2 driven by moisture change, which can effectively reduce the energy consumption and operation cost of CO2 capture. The mechanism of moisture swing adsorption technology of quaternary ammonium-based adsorbents and the mechanism of action from the perspective of thermodynamics and kinetics were described. The influencing factors of adsorbents performance were introduced. The synthesis and modification methods and research progress of adsorbents in recent years were summarized. Finally, the current challenges in this field were summarized and the development trend was pointed out. The process of CO2 adsorption by quaternary ammonium-based adsorbents is driven by water evaporation and affected by moisture fluctuation. When the adsorbents are loaded with divalent and trivalent acid anions, the hydrophilic/hydrophobic layer spacing and cation spacing are small, and the CO2 adsorption performance is strong. The adsorbent materials with smaller particle size, richer porosity and higher specific surface area can be prepared by directional regulation of pore structure. In addition, the quaternary ammonium functional groups are chemically grafted by enhanced quaternization or biquaternization to enhance the density of active sites and efficient utilization. Moisture swing adsorption technology is currently in the development stage. On the basis of maintaining a high specific surface area and functional group utilization, improving the adsorption capacity and cycle rate is an inevitable demand for practical applications. Its large-scale application, reducing capture energy consumption, improving environmental tolerance, and the treatment of CO2 after capture are also the key directions to be studied.关键词：CO2 capture;moisture swing adsorbents;quaternary ammonium-based;kinetics;thermodynamics- 39
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发布时间：2024-11-25 -
摘要：The membrane separation method for capturing carbon dioxide (CO2) in flue gas has attracted wide attention because of its characteristics such as low pollution, simple operation and small equipment size. Based on the research progresses of CO2 capture in flue gas by membrane separation method at home and abroad, the performance indexes and development of CO2 separation membrane materials were firstly summarized. And then the characteristics of different membrane modules were compared and the factors affecting the design and optimization of membrane separation process were analyzed, and the difficulties of large-scale industrialization of membrane separation method were summarized. Finally, the future development of membrane separation technology for capturing CO2 in flue gas was prospected, including research and development of new membrane materials and supporting preparation processes, development of new membrane modules, optimization of process flow and construction of industrial demonstration equipment.关键词：membrane separation method;membrane materials;membrane modules;carbon dioxide capture;flue gas- 54
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发布时间：2024-11-25 -
摘要：The conventional three-stage cascade Rankine cycle system for liquefie natural gas (LNG) cold energy power generation fails to effectively utilize the working fluid’s cold energy, therefore an improved multi-stream three-stage cascade combined cycle (MS-3CC) system was proposed. By adding a multi-stream heat exchanger, the system can utilize the cold energy of LNG and working fluid in multiple stages, effectively reducing the complexity of the system and improving its thermodynamic performance and economy. Through genetic algorithm optimization calculation, when the exhaust pressure of natural gas (NG) is 5.5 MPa, and the working fluid is selected as propane in all syetems, the maximum net output power of the MS-3CC system is 6027 kW, which is 5.4% and 80.3% higher than that of the parallel three-stage cascade combined cycle (P-3CC) system and single-stage combined cycle (SCC) system, respectively, and its annual total net income increases by 16.9% and 68.0%, respectively. Comparing 64 working fluid combinations, it is found that the net output power of the MS-3CC system is highest when using CH2F2 + CH2F2 + C3H8. The proposal of MS-3CC system provides a reference for more effective multi-stage utilization of LNG cold energy in industrial practice.关键词：LNG cold energy power generation;three-stage Rankine cycle;multi-stream heat exchange;economic analysis;working fluid selection;genetic algorithm- 26
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发布时间：2024-11-25 -
摘要：The boil-off gas (BOG) from liquefied natural gas (LNG) storage tanks has a high helium content, which makes it a suitable raw material for helium extraction. The traditional two tower expansion refrigeration process for helium extraction has low separation efficiency and limited helium product concentration. A three tower nitrogen expansion process for low-temperature helium extraction was proposed, and HYSYS software was used for simulation and optimization. The results show that the three tower nitrogen expansion process for low-temperature helium extraction has significant advantages in terms of LNG liquefaction rate, helium product concentration and helium recovery rate, compared to the traditional two tower expansion refrigeration process for helium extraction. After further optimization, the three tower nitrogen expansion process for low-temperature helium extraction can achieve a helium product concentration (mole fraction) of 95.60% and a helium recovery rate of 99.99% with a slight increase in total power consumption. This process obtains high-concentration helium with high recovery rate using only low-temperature distillation, and has obvious comprehensive performance advantages.关键词：BOG;helium extraction;nitrogen expansion;three tower process- 30
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发布时间：2024-11-25
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