最新刊期
卷 49 ， 期 5 ， 2024
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摘要：In order to prepare methanol to olefin (MTO) catalysts with higher performance and achieve efficient conversion of methanol to low-carbon olefins, crystal with defect sites was prepared by post-treatment of conventional SAPO-34 molecular sieve. And then hierarchical SAPO-34 molecular sieve was successfully prepared in the hydrothermal synthesis system. The crystal structures, morphologies, pores and acidities of the prepared SAPO-34 molecular sieve were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption/desorption, mercury intrusion porosimetry and NH3 temperature programmed desorption (NH3-TPD). The catalytic activity of the prepared SAPO-34 molecular sieve for MTO reaction was carried out in a fixed bed reactor (reaction temperature of 460 ℃, atmospheric pressure, mass space velocity of methanol of 3.0 h-1 and raw material of pure methanol). The results indicate that the hierarchical SAPO-34 molecular sieve has a three-level pore structure of macropore, mesopore and micropore. The presence of macro/mesopores can, on the one hand, make the target products diffuse from the pore quickly, reducing the probability of secondary reactions, and on the other hand, make it easier for heavy hydrocarbon molecules to diffuse to the active sites for further reactions. Therefore, in the MTO reaction, the hierarchical SAPO-34 molecular sieve shows the highest selectivity of ethylene and propylene, which is 85.3%, and lower selectivity of C4 and C5+ (hydrocarbons with carbon numbers of four and carbon numbers greater than or equal to five) and can maintain stable performance within 135 min. At the same time, after multiple reactions and regeneration, the catalyst can still maintain excellent catalytic performance.关键词：defect crystal;molecular sieve;hierarchical SAPO-34;methanol to olefin- 15
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发布时间：2024-05-23 -
摘要：Copper-zinc coprecipitation method is a commonly used method for preparing copper-zinc based methanol synthesis catalysts, but this method is difficult to achieve the construction and regulation of copper-zinc oxide interface active sites on the surface of catalysts. To solve this problem, a stepwise precipitation method was applied. Keeping the overall Zn content unchanged, a part of zinc was co-precipitated with copper to form a bulk core, while a part of zinc was coated on the particle surface to form copper-zinc oxide interface sites. The influence of Zn coated ratios on the catalyst performance was studied. X-ray diffraction (XRD), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) were used to analyze the particle sizes, pore properties, valence and electronic properties and reducing abilities. The results show that the catalysts synthesized by stepwise precipitation method have smaller particle sizes, richer pore structures, stronger copper-zinc interactions, more stable low valent copper sites and greater reductive capacity, compared with the catalyst synthesized by co-precipitation method. The methanol synthesis results show that the initial activity and the activity after a thermal treatment of catalyst are optimal when 25% zinc is encapsulated under the reaction conditions of 5.0 MPa, 250 ℃ and the space velocity of 10000 h-1. The initial activity increases by 6% and activity after thermal treatment increases by 11%, compared with the catalyst synthesized by co-precipitation method. When 50% zinc is encapsulated, the activity degradation rate of the catalyst after thermal treatment is the lowest (14.1%), which is only 66% of that of the catalyst synthesized by co-precipitation method. The activity and thermal stability of catalysts synthesized by stepwise precipitation have been significantly improved. This method achieves effective regulation of the active sites on the methanol catalyst surface, so as to successfully improve the activity and thermal stability of the copper-zinc based methanol catalysts.关键词：methanol synthesis;catalyst;reactivity;stepwise precipitation- 16
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发布时间：2024-05-23 -
摘要：Domestic large methanol plants mainly use foreign methanol synthesis process packages and catalysts, which is not conducive to the long-term and stable development of modern coal chemical technology in China. China Shenhua Coal to Liquid Chemical Co., Ltd. realized the application of domestic methanol synthesis catalyst in a methanol plant with productivity of 180 × 104 t/a for the first time. The physicochemical parameters, heating reduction process and operation of a foreign methanol synthesis catalyst (M catalyst) and a domestic methanol synthesis catalyst (C catalyst) were compared and analyzed. The results show that compared with M catalyst, C catalyst has the advantages of high activity (especially low temperature activity), strong stability, high per pass conversion rates of gas, and less by-products and wax. In addition, C catalyst has a better energy saving effect than M catalyst, and under set up conditions (electricity price is 0.3 CNY/(kW·h), water price is 0.15 CNY/t and steam price is 100 CNY/t), using C catalyst can save about 667.8 × 104 CNY/a. At present, C catalyst has been running stably in the plant for more than one year, and the production load of the plant is close to 110%.关键词：methanol plant;methanol synthesis catalysts;domestic application- 13
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发布时间：2024-05-23 -
摘要：All-inorganic lead halide perovskites with excellent optoelectronic properties are ideal materials for photocatalytic carbon dioxide reduction. However, the toxicity and inherent instability of Pb limit their practical commercial application. To this end, lead-free perovskite materials Cs2PtBr6 microcrystal and Cs2PtBr6 nanocrystal were synthesized by anti-solvent method. The morphologies, compositions and optoelectronic properties of the samples were characterized by SEM, TEM, XRD and Ultraviolet-visible absorption spectrum, et al. The results show that the specific surface area of the sample is increased and the absorption performance is enhanced after Cs2PtBr6 microcrystal is converted into Cs2PtBr6 nanocrystal. The average photogenerated carrier lifetime is extended from 1.83 ns in Cs2PtBr6 microcrystal to 2.42 ns in Cs2PtBr6 nanocrystal. Moreover, the average photocurrent density of Cs2PtBr6 nanocrystal is 6.4 times stronger than that of Cs2PtBr6 microcrystal, and the charge transfer resistance of Cs2PtBr6 nanocrystal is smaller than corresponding value of Cs2PtBr6 microcrystal, so the separation and transfer efficiency of photogenerated carriers are improved. Among them, Cs2PtBr6 nanocrystal synthesized under 50 ℃ of stirring temperature has the highest photocatalytic activity, and the carbon monoxide yield under the set up conditions of- 8
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发布时间：2024-05-23 -
摘要：Ethanol dehydroamination is a clean, safe and economical way to obtain high purity acetonitrile. The effects of preparation conditions (calcination atmospheres and Co loadings) on the catalytic performances in ethanol dehydroamination to acetonitrile over xCo0.25La/Al2O3-y (x and 0.25 represent the loading (mass fraction, %) of Co and La, respectively, and y represents calcination atmospheres) were investigated in a fixed flow bed. And the reactions were carried out for 45 min at 410 ℃ 0.1 MPa, anhydrous ethanol space velocity of 0.5 h-1, and the ratio of ammonia to alcohol of 6:1. The catalysts were characterized by XRD, XRF, N2 absorption/desorption and CO pulse chemisorption. The results show that the metal active surface area of xCo0.25La/Al2O3-10H2/N2 first increases and then decreases with the increase of Co loading, and the reduced Co surface area of 10Co0.25La/Al2O3-10H2/N2 is 23.38 m2/g, and its acetonitrile selectivity is the highest (88.47%). 10Co0.25La/Al2O3-10H2/N2 is continuously operated at 430 ℃ for 120 h while other reaction conditions unchanged, and the acetonitrile selectivity rapidly decreases from the initial 88.32% to 66.80% at 21 h, and then satabilizes at about 65%. The corresponding selectivity of ethylamine and butyronitrile remain about 12% and 5%, respectively.关键词：preparation conditions;ethanol dehydroamination;acetonitrile;CoLa/Al2O3 catalyst- 26
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发布时间：2024-05-23 -
Study on copper-nickel bimetallic catalysts for amination of ethylene glycol to ethylenediamine AI导读
摘要：Catalytic amination of ethylene glycol (EG) to ethylenediamine (EDA) is a green, efficient and economical route to obtain EDA, but there are still some problems to be solved, such as harsh reaction conditions and poor product selectivity. By adjusting n(Cu):n(Ni), a series of Cua-Ni1-a-Al-O (the value of a is 0.09, 0.30, 0.50, 0.70 and 0.91, respectively) catalysts were prepared by co-precipitation method and used for amination of EG to EDA. The catalysts were characterized by X-ray diffraction (XRD), N2 absorption/desorption and high-resolution transmission electron microscopy (HR-TEM), etc, and the reaction conditions of catalytic amination of EG to EDA were optimized. The results show that the specific surface area of Cu-based monmetallic catalyst can be significantly increased by the introduction of Ni, and Cu0.09-Ni0.91-Al-O has the largest specific surface area (150.20 m2/g) and the smallest average pore size (5.84 nm). The Cu and Ni in Cua-Ni1-a-Al-O exist in the form of CuNi alloy, and the crystallinity and crystal size of the catalyst decrease with the decrease of a. Under the optimal reaction conditions (200 mg Cu0.09-Ni0.91-Al-O, 1 mmol EG, 15 mL 1,2-dimethoxy-ethane, 7 g NH3, 3 MPa H2, 180 ℃ and reaction for 13 h), the EG conversion rate and EDA yield are 100% and 60%, respectively. Cu0.09-Ni0.91-Al-O is recycled for four times under the optimal reaction conditions, and the catalytic performance of Cu0.09-Ni0.91-Al-O does not change significantly.关键词：copper-nickel bimetallic catalysts;catalytic amination;ethylenediamine;ethylene glycol- 27
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发布时间：2024-05-23 -
摘要：Precious metal deoxidation catalysts and chemisorbed deoxidation catalysts used for deoxidation from ethylene gas have drawbacks such as high cost, limited deoxidation capacity, and frequent regeneration requirements. Deep deoxidation catalysts for ethylene gas were prepared by loading Pd-Ag bimetallic active components onto the γ-Al2O3 support modified with rare earth oxides. The performance of the deep deoxidation catalysts for ethylene gas was investigated, and the structures of both the support and the catalyst were characterized using X-ray diffraction (XRD), N2 adsorption/desorption and thermogravimetric analysis. The results show that the rare earth-modified support has larger pore volume and pore size (average pore size increases from 1.90 nm before modification to 2.50 nm after modification), while the active component exhibits high dispersion and excellent low-temperature deoxidation activity. Oxygen in the ethylene gas can be reduced to less than 1 × 10-6 (volume fraction of O2) at temperature between 110 °C and 180 °C. The catalyst maintains high deoxidation activity during a 1650 h life test at conditions of space velocity of 5000 h-1 and reaction temperature of 145 °C, without requiring reduction and regeneration before or during use.关键词：ethylene;catalyst;deep deoxidation;rare earth modification- 14
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发布时间：2024-05-23 -
摘要：The large-scale use of fossil fuels has led to excessive CO2 emissions, and the resulting global climate problems have received widespread attention. Chemical looping combustion improves the traditional combustion method by using a circulating oxygen carrier to provide active oxygen to the fuel, avoiding the dilution of N2 to the flue gas, reducing the cost of CO2 capture and has the advantage of internal separation of CO2, which has a great potential for development in the field of CO2 capture. Oxygen carrier is the core of chemical looping combustion technology, which plays the dual role of transferring heat and releasing lattice oxygen, but the oxygen carrier faces the problems of large attrition rate and short lifetime, which seriously affect the economy of chemical looping combustion technology. The apparent phenomena and intrinsic mechanism of oxygen carrier attrition were reviewed, and chemical attrition is found to be the main factor of oxygen carrier attrition. The methods of assessing and predicting the attrition of oxygen carrier as well as the methods of improving the abrasion resistance of oxygen carrier were summarized, and the future research of oxygen carrier was also prospected.关键词：chemical looping combustion;CO2 capture;oxygen carrier;attrition- 20
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发布时间：2024-05-23 -
Mechanism simplification and combustion characteristics verification of dimethyl ether combustion 增强出版 AI导读
摘要：As a fuel, dimethyl ether (DME) has the advantages of wide source, renewable and low carbon, and has become the most potential alternative fuel for internal combustion engine and gas turbine. However, the research on the combustion mechanism of DME is still insufficient. The skeleton mechanism (Mech_191) was obtained by simplifying the detailed mechanism of DME combustion under high pressure by using DRGEPSA method with error propagation and sensitivity analysis, and then the simplified mechanism was obtained by optimizing Mech_191 by adjusting the pre-exponential factor. The predicted values of the important parameters indicating DME combustion (ignition delay time and laminar flame velocity) obtained by the simplified mechanism were compared with those in the literature. The results show that the predicted values of the simplified mechanism are in good agreement with those in the literature, which verifies the effectiveness of the mechanism in simulating the combustion characteristics of DME. In addition, it is also found that the determination of some key reactions (such as the consumption reaction of ·CH3OCH2) plays an important role in accurately obtaining important combustion parameters.关键词：dimethyl ether combustion mechanism;DRGEPSA method;ignition delay time;laminar flame speed- 16
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发布时间：2024-05-23 -
摘要：The solar energy driven methane dry reforming and conversion technology can convert CO2 and CH4 into fuel synergistically, which is an effective way to achieve solar energy storage and CO2 emission reduction. Because of its good thermal conductivity, high mechanical strength and gas permeability, the porous foam reactor has become a research hotspot in the large-scale energy application of solar energy driven methane dry reforming and conversion technology. The effect of inlet conditions on the reactor performance was studied by computational fluid dynamics simulation (CFD). The results show that the reaction performance is best when the total incident radiation is 130.8 W and inlet flow rate is 0.85 L/min, and the conversion rates of CH4 and CO2, and light-fuel efficiency are 79.73%, 87.53% and 37.03%, respectively. The relationship between pore structure and reaction performance of uniformly porous Ni foam reactor (“Ni foam reactor” for short) was studied by CFD coupled with genetic algorithm (GA). The results show that the reaction performance of the Ni foam reactor can be improved to a certain extent by increasing the porosity, and the reaction performance increases first and then decreases with the increase of the pore size. The Ni foam reactor (structure 3) with porosity of 0.93 and the pore size of 1.72 mm has the best reaction performance. The conversion rates of CH4 and CO2, and light-fuel efficiency are 83.55%, 89.53% and 46.47%, respectively. Then, two optimization strategies for the design of Ni foam reactors with double gradient gradient aperture are proposed, namely, the gradient from large to small in the axial direction and from small to large in the radial direction (structure 1) and the gradient from large to small in both the axial and radial direction of the aperture (structure 2). Comparing with structure 3, structure 1 helps to penetrate the radiation while ensuring a higher temperature in the central region, and the light-fuel efficiency is 55.00%. And structure 2 contributes to the gradual absorption of solar energy, which in turn enhances temperature uniformity, with a light-fuel efficiency of 52.20%.关键词：methane dry reforming;solar energy;foam reactor;computational fluid dynamics;genetic algorithms- 38
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发布时间：2024-05-23 -
摘要：CaO is a kind of efficient and cheap CO2 capture adsorbents, but it is prone to sintering in the process of recycling, resulting in a significant decrease in capture capacity and making it unsuitable for long-term cyclic applications. Semi-inert Al2O3-doped CaO was used to prepare the calcium-aluminum composite adsorbents. The capture performance and cycle stability of the calcium-aluminum composite adsorbents were studied by thermogravimetric adsorption/desorption method. The regeneration performance of the calcium-aluminum composite adsorbents was further studied by air regeneration method at room temperature, and the relationships between regeneration performance and cycle times were established. The results show that the adsorption performance, cycle stability and regeneration performance of calcium-aluminum composite adsorbents are much better than those of pure CaO adsorbents because of the establishment of inert skeleton phase of Ca3Al2O6 and the formation of micro-nano structure. After 100 cycles, the CO2 adsorption capacity and carbonation conversion rate of the calcium-aluminum composite adsorbents reach 0.23 g/g and 34.0% respectively when n(Ca):n(Al) = 10:1, and remain at 0.19 g/g and 32.8% respectively when n(Ca):n(Al) = 10:2, but n(Ca):n(Al) should not exceed 10:2. It is proved by the deactivation mathematical model of the adsorbents that the sintering of CaO adsorbents is irreversible, and the doping of Al2O3 can inhibit the sintering of CaO adsorbents and keep the regeneration activity of calcium-aluminum composite adsorbents. The carbonation conversion rate of the calcium-aluminum composite adsorbents (n(Ca):n(Al) = 10:2) after regeneration for twice under air remains basically unchanged, which is still 32.7% after 100 cycles.关键词：CaO adsorbents;Al2O3-doped;CO2 capture;air regeneration at room temperature;multiple cycles capture- 16
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发布时间：2024-05-23 -
摘要：The carbon fixation and alkali reduction process of fly ash absorbent is of great significance in reducing carbon dioxide (CO2) emission, comprehensive utilization of resources and treatment of alkaline wastewater. Using the solid waste fly ash from Sandaogou Fugu Power Plant in Yulin, Shaanxi as raw materials, fly ash CO2 absorbents (“absorbent” for short) were prepared by modification treatment. The effects of different pretreatment agents (acetic acid (CA), sodium chloride (NaCl) and sodium hydroxide (NaOH) solution, respectively, all the mass fractions are 85%) on the carbon fixation and alkali reduction performance and carbonation and leaching property of absorbent were studied, and the effects of temperature and CO2 injection rate on the carbon fixation and alkali reduction process were analyzed. The results show that NaOH can effectively destroy the spherical vitreous structure of fly ash and release the active components. Increasing the temperature can increase the ion leaching rate in fly ash and make the reaction move forward. Increasing CO2 injection rate can improve the dissolution rate of CO2 in the absorber, but too high CO2 injection rate will shorten the gas-liquid contact time, resulting in lower absorption efficiency. With NaOH solution as pretreatment agent, under the conditions that temperature is 60 ℃, CO2 injection rate is 40 mL/min and absorption time is 5 h, the carbon fixation and alkali reduction process has the best effect. The absorption efficiency of the absorber can reach 27.89%, and the carbon fixation capacity is 30.16 kg/t.关键词：fly ash;absorbent;carbon dioxide;carbon fixation and alkaline reduction;process optimization- 24
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发布时间：2024-05-23 -
摘要：H2 as a kind of clean energy is considered to be one of the most promising alternative energy sources to alleviate energy crisis and reduce environmental pollution. Using renewable energy to electrolyze water for H2 production is an important method for green hydrogen production. However, low current density and high energy consumption are the problems of industrial electrolysis of water for hydrogen production. Increasing the current density is the most direct way to increase the hydrogen production rate, but if the electrocatalyst is not optimized, increasing the current density will cause the increase of power consumption. Therefore, it is urgently needed to develop high-performance electrocatalysts for the hydrogen evolution reaction (hereinafter referred to as “HER”) with low overpotential under high current density. Firstly, the mechanism of HER reaction in acidic and alkaline media was introduced, including Volmer-Heyrovsky and Volmer-Tafel, and the requirements of high performance electrocatalysts under high current density were put forward. Then, the research progress of precious metal and non-precious metal HER electrocatalysts in recent years from the aspects of single atom electrocatalysts, alloy electrocatalysts and heterostructure electrocatalysts were reviewed. Finally, the challenges and opportunities in the future for the development of HER electrocatalysts were discussed.关键词：electrocatalyst;hydrogen evolution reaction;high current density- 34
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发布时间：2024-05-23 -
摘要：Developing high-performance, low-cost catalysts for the oxygen evolution reaction (OER) is of paramount importance for reducing energy consumption and enhancing economic viability in hydrogen production through water electrolysis. Using conductive nickel foam as a substrate, a series of nickel-iron bi-metallic oxide catalysts were prepared by in-situ growth of nickel-iron Prussian blue analogs through an ice-water bath method, followed by oxidation. The catalysts were characterized for its phase composition, microstructure, and surface chemical states using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscope and X-ray photoelectron spectroscop. The catalytic performances of the catalysts for OER were investigated through electrochemical tests. The results show that when oxidized at a temperature of 200 ℃ for 2 h, nickel-iron bi-metallic oxide is highly dispersed on the nickel foam substrate of the prepared catalyst. The nanoparticles are the smallest, with an average particle size of 71 nm, providing numerous exposed catalytic active sites, thus demonstrating optimal OER electrocatalytic performance. In 1.0 mol/L KOH electrolyte, the catalyst achieves a low overpotential of only 272 mV at a current density of 10 mA/cm² and exhibites excellent electrochemical stability, maintaining stable operation for 40 h at a current density of 100 mA/cm².关键词：Prussian blue analogs;nickel-iron bi-metallic oxide catalysts;oxygen evolution reaction;alkaline water electrolysis- 15
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发布时间：2024-05-23 -
Research status and development trends of FPLNG pretreatment and liquefaction integrated process AI导读
摘要：The compactness of offshore natural gas processing systems is particularly crucial for adapting to offshore environments. To address the limited deck space and load-bearing capacity faced by floating liquefied natural gas production, storage, and offloading units (FLNG), the concept of a novel FLNG with pressurized liquefaction process (FPLNG) was proposed. The key technologies and application status of FLNG were elaborated, and the key technologies and storage solutions of FPLNG were analyzed. The key technologies of FPLNG enhance the solubility of CO2 and heavy hydrocarbons, simplifying the pretreatment and liquefaction processes. The synergy between low-temperature decarbonization technology and liquefaction process enables the integration of offshore natural gas pretreatment and liquefaction into a single process. Pressurized liquefied natural gas (PLNG) can be stored in high-pressure tanks with high-strength, low-temperature steel structures and tank containers. The high-pressure tank solution has lower costs than atmospheric pressure transportation when the pressure is approximately 0.5 MPa, and the transportation distance is less than 400 km. FPLNG has significant potential for the efficient development of China’s deep-sea natural gas resources and is expected to be widely applied in the future. However, further research is needed to address issues such as fluid phase equilibrium.关键词：FPLNG;decarbonization;liquefaction;integration;storage- 14
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发布时间：2024-05-23 -
摘要：The cold energy released during the liquefaction process of liquefied natural gas (LNG) is often underutilized. An LNG cold energy recovery system that combines refrigeration with power generation to effectively recover LNG cold energy was proposed. The system structure includes two-stage organic Rankine cycles (ORC), air conditioning (AC), and direct expansion cycle (DEC). Using HYSYS software, the system performance was simulated and analyzed. Genetic algorithm (GA) was employed to optimize the mixture ratio of the four-component working fluid (methane, ethane, propane and isobutane), evaporation pressure, condensation pressure, and primary expansion pressure in the system. Subsequently, an economic evaluation of the optimized scheme was conducted. The results show that the optimal mass fraction of the four-component working fluid for the front and rear stages of the ORC are 28.9%, 57.3%, 5.5%, 8.3% and 0.4%, 20.3%, 56.4%, 22.9%, respectively. In the optimized scheme, the net output power of the system can reach 218.28 kW, and the utilization rate of LNG cold energy, thermal efficiency and exergy efficiency are 54.69%, 20.89% and 41.18%, respectively. The system exhibits good economic feasibility, with an economic and benefit of 160.30 × 104 CNY. The total investment cost of the equipment is 1215.91 × 104 CNY, and the levelized energy cost is 0.63 CNY/(kW·h), with an expected payback period of within 7.59 a.关键词：LNG;mixed working fluid;exergy analysis;economic analysis- 24
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发布时间：2024-05-23
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