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Table of Content
05 July 2023, Volume 74 Issue 7
    Reviews and monographs
    Advances in the design, synthesis and application of calcium-based catalysts
    Yuming TU, Gaoyan SHAO, Jianjie CHEN, Feng LIU, Shichao TIAN, Zhiyong ZHOU, Zhongqi REN
    2023, 74(7):  2717-2734.  doi:10.11949/0438-1157.20230193
    Abstract ( 479 )   HTML ( 47)   PDF (4353KB) ( 341 )  
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    Calcium-based catalyst are solid base catalyst with calcium oxides as metal active sites. It has the advantages of being green and efficient, cheap and easy to obtain, and has good catalytic performance. It can be widely used in the fields of biodiesel preparation, wastewater treatment, and tar cracking and reforming. They have received more and more attention from researchers all over the world. This article introduces the types of calcium-based catalysts, their application research status and mechanism of action, outlines their research progress in various applications, and analyzes and summarizes the history and trends of calcium-based catalyst design and synthesis ideas. From natural calcium-based catalysts such as CaO and Ca(OH)2 to actively designed and synthesized loaded Ca-containing catalyst, it is pointed out that the synthesis of stable and efficient calcium-based catalysts is the key to realize their further development. Finally, the research progress of calcium-based catalysts is summarized and its future development and application prospects are prospected.

    Construction of nanomaterial and integrated catalyst based on biological template: a review
    Yajie YU, Jingru LI, Shufeng ZHOU, Qingbiao LI, Guowu ZHAN
    2023, 74(7):  2735-2752.  doi:10.11949/0438-1157.20230456
    Abstract ( 411 )   HTML ( 42)   PDF (8636KB) ( 423 )  
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    The design, preparation and application of new nano-catalytic materials are one of the research hotspots in the field of catalysis in recent years. Biological templates with complex and fine hierarchically porous structures are ubiquitous and can be used as soft templates, hard templates, or support to prepare nanomaterials with highly connective and hierarchical pores. Based on the regulation of preparation process parameters, the macro-morphology and micro-nano structure of the biological templates could be retained, as well as replacing the original biological components with the required catalytic components (e.g., metals, metal oxides, zeolites, etc.). This strategy provides new ideas for the design of nanomaterial and integrated nanocatalysts. In particularly, the “multi-level space” of such integrated catalytic materials is very difficult to be prepared by the existing traditional methods or the preparation process would be cumbersome in most cases. Starting from several typical biological templates from different sources, this review introduces the common preparation methods of nanomaterials and integrated nanocatalysts using natural biological templates, summarizes the research status of such integrated materials in catalysis, and looks forward to future research works on the utilization of biological templates to fabricate integrated nanocatalysts with multi-components.

    Recent advances in carbon-based catalysts for electrochemical reduction of carbon dioxide
    Qiyu ZHANG, Lijun GAO, Yuhang SU, Xiaobo MA, Yicheng WANG, Yating ZHANG, Chao HU
    2023, 74(7):  2753-2772.  doi:10.11949/0438-1157.20230174
    Abstract ( 498 )   HTML ( 34)   PDF (8041KB) ( 551 )  
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    Converting carbon dioxide (CO2) into high-energy fuel or high-value chemicals by electrochemical reduction technology is an effective way to enhance the added value of CO2 utilization and alleviate the pressure of CO2 emission, and is also one of the conversion and storage methods for green energy such as wind power, hydropower and solar energy, which is of great significance to “peak-clipping and valley-filling” of intermittent power. One of the keys to realize high-efficiency electrochemical reduction of CO2 lies in the creation of high-performance electrocatalytic materials. In this paper, the research progress of carbon-based catalytic materials for electrochemical reduction of CO2 is reviewed, and the structural characteristics of intrinsic defective carbon materials, doped carbon materials, carbon-based composites and monolithic carbon materials are discussed. On this basis, the challenges and future development of carbon-based catalytic materials for electrochemical reduction of CO2 are prospected.

    Advances in enzyme self-immobilization mediated by protein nanocages
    Yaxin CHEN, Hang YUAN, Guanzhang LIU, Lei MAO, Chun YANG, Ruifang ZHANG, Guangya ZHANG
    2023, 74(7):  2773-2782.  doi:10.11949/0438-1157.20230209
    Abstract ( 238 )   HTML ( 24)   PDF (1679KB) ( 305 )  
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    In recent years, new enzyme carrier materials represented by metal-organic frameworks and self-assembled proteins have emerged. Among them, the unique advantages of self-assembled proteins represented by protein nanocages in the field of enzyme self-immobilization are being continuously explored by researchers. Due to the unique cage-like cavity, facile gene/chemical modification and controllable self-assemble of protein nanocages, the self-immobilized enzyme with improved yield, stability and catalytic activity is readily achieved. This review begins with an overview of novel enzyme self-immobilization materials, such as metal-organic framework materials and self-assembled proteins. Then, the characteristics of nanocage proteins are presented in terms of 3D structure, particularly the structural design of ferritin and self-assembly mechanism. Finally, the research progress of protein nanocages in enzyme self-immobilization is reviewed, and the possible research directions in the future are pointed out, providing reference for establishing new self-immobilization strategies, and then promoting self-immobilized enzymes from laboratory research to industrial application.

    Research progress on activation extraction of valuable metals in coal gangue
    Chao KANG, Jinpeng QIAO, Shengchao YANG, Chao PENG, Yuanpeng FU, Bin LIU, Jianrong LIU, Aleksandrova TATIANA, Chenlong DUAN
    2023, 74(7):  2783-2799.  doi:10.11949/0438-1157.20230260
    Abstract ( 349 )   HTML ( 25)   PDF (5069KB) ( 310 )  
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    Coal gangue is a solid waste in the process of coal mining and washing, and it is one of the largest industrial solid wastes in China. Recycling and utilizing potential mineral resources is of great significance to realize the goal of green mine construction and “dual carbon” target in China. Based on the comprehensive analysis of the relevant technology of extracting valuable metals from coal gangue at the present stage at home and abroad, the research progress of efficient enrichment of valuable components such as aluminum and iron by “single/composite activation-alkali fusion/acid leaching” was systematically expounded, and focused on the analysis of the occurrence state and extraction methods of trace key metals such as lithium and rare earth. In view of the complex composition of coal gangue, large fluctuation range, and low content of valuable metals, based on the mineral characteristics, the corresponding mineral processing technology can be used to initially enrich the carrier minerals, improve the grade of valuable metals, and then carry out the synergistic extraction of aluminum, iron, lithium, rare earth, and other elements to realize the high value-added utilization of coal gangue.

    Review of gas phase and surface reactions in AlN MOCVD
    Xiaokun HE, Rui LIU, Yuan XUE, Ran ZUO
    2023, 74(7):  2800-2813.  doi:10.11949/0438-1157.20230380
    Abstract ( 376 )   HTML ( 30)   PDF (3319KB) ( 182 )  
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    As a representative of the third-generation semiconductor materials, AlN single crystal has the characteristics of large band gap, high breakdown electric field strength, and high electron saturation mobility, and is widely used in the manufacture of ultraviolet and deep ultraviolet light-emitting devices. Metal organic chemical vapor deposition (MOCVD) is the main technique in the manufacture of AlN thin films. Due to the highest binding energy of Al—N among the group Ⅲ-nitrides (AlN, GaN and InN), severe parasitic reactions occur in AlN MOCVD, which results in the low growth rate, low growth efficiency and very narrow growth window. Besides, the high Al—N binding energy results in the low mobility of Al-containing particles on the surface and consequently deteriorating the surface morphology. The above problems are all related with chemical reactions in AlN MOCVD. In this article, we summarize comprehensively previous research work on the MOCVD growth of AlN thin films from two aspects: gas-phase reactions and surface reactions, and introduce some research work by our team in recent years. Finally, the problems and shortcomings in the current research on MOCVD growth of AlN are summarized, and some further researches are prospected.

    Fluid dynamics and transport phenomena
    Numerical simulation of start-up characteristics and heat transfer performance of ultra-thin heat pipe
    Fangzhe SHI, Yunhua GAN
    2023, 74(7):  2814-2823.  doi:10.11949/0438-1157.20230429
    Abstract ( 237 )   HTML ( 26)   PDF (2778KB) ( 255 )  
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    In this paper, a simplified three-dimensional transient model of ultra-thin heat pipe was proposed to simulate the process of heat pipe from start-up to stable operation. Based on the previous work of the team, the accuracy of the model was verified. Heat pipes with different vapor core thicknesses, types of wicks and bending section geometry were studied by numerical simulation. The influence of different parameters on the vapor flow characteristics, temperature distribution and start-up performance is analyzed. Based on the control theory, the thermal response characteristics of heat pipes with different structures are quantitatively analyzed. The maximum RMSE is only 0.385. The results show that the flow resistance and energy loss of vapor will increase if the vapor core thickness is too small. Different structures of wicks mainly affect the steam flow characteristics through the difference in the width of the steam channel. The smaller the vapor core thickness is, the more easily it is affected by the bending radius and bending angle of the bending section. In addition, if the thickness of the flow channel is less than 0.2 mm, it will also affect the temperature uniformity of the heat pipe and limit the vapor-liquid circulation. The total thermal resistance and start-up time of the heat pipe are mainly affected by the heat load.

    Capillary liquid film condensation and heat transfer enhancement driven by superhydrophilic porous metal structure
    Ben ZHANG, Songbai WANG, Ziya WEI, Tingting HAO, Xuehu MA, Rongfu WEN
    2023, 74(7):  2824-2835.  doi:10.11949/0438-1157.20230538
    Abstract ( 172 )   HTML ( 13)   PDF (5589KB) ( 126 )  
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    Steam condensation can release a large amount of latent heat of phase change at a small temperature difference, and plays an important role in petrochemical, waste heat utilization, seawater desalination and other fields. Here, a capillary liquid film condensation driven by superhydrophilic porous metal structures is proposed by coupling the rapid condensate transport in capillary structures and the reduced thermal resistance of wetted porous structures. Such a capillary liquid film mode is suitable for enhancing condensation heat transfer of water and various low surface energy fluids. A heat and mass transfer model of capillary liquid film condensation is established to investigate the effect of the porosity and thickness of porous structures, the physical properties of working fluids, and the operating conditions of condensation on the heat transfer coefficient, critical heat flux, and flooding threshold of subcooling. The results show that as the thickness and porosity of porous structures increase, the heat transfer coefficient increases while the maximum surface subcooling and critical heat flux decrease. Combined with condensation heat transfer and visualization experiments, the effect of the copper foam structure on liquid condensate behaviors and heat transfer performance is further investigated. The heat transfer model of capillary liquid film condensation is also verified.

    Molecular dynamics study on heterogeneous characteristics of supercritical water
    Ming DONG, Jinliang XU, Guanglin LIU
    2023, 74(7):  2836-2847.  doi:10.11949/0438-1157.20230398
    Abstract ( 159 )   HTML ( 9)   PDF (4927KB) ( 362 )  
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    Understanding the heterogeneous characteristics of supercritical fluids is helpful for its efficient utilization in the fields of power cycle, waste treatment and petrochemical industry. Recently, the heterogeneous structure of supercritical fluids has been verified by experiments. Supercritical fluids can be divided into gas-like, two-phase-like and liquid-like regions. However, most studies focused on Lennard-Jones fluids in near-critical or narrow temperature and pressure parameters. As one of the most widely used supercritical fluids, the influence of hydrogen bond network in water on heterogeneous characteristics was still unclear. In this work, molecular dynamics simulation was performed to investigate the heterogeneous characteristics of supercritical water under a wide range of temperature and pressure parameters, focusing on the evolution of hydrogen bonding, physical structure and kinetic properties. The results show that the turning point of the number of dimers in supercritical water at the same pressure represents the transition from liquid-like phase to gas-like phase, and the turning point of the first peak of the radial distribution function represents the transition from two-phase to gas-like phase, which correspond to the Widom line and corresponding to gas line. According to the significant differences between the liquid-like and gas-like regions in the average number of hydrogen bonding, the physical structure such as the number of neighboring molecules, and the kinetic properties such as diffusion and rotation, the boundary locations of the two-phase-like region of supercritical water are determined. The results are in good agreement with the thermodynamic methods, with an average error of less than 5%. This work reveals the evolution of heterogeneous characteristics of supercritical water at molecular level, and provides theoretical support for relevant applications of supercritical fluids.

    Mode decomposition of flow field in T-junction with rotating impeller
    Kexin HUANG, Tong LI, Anqi LI, Mei LIN
    2023, 74(7):  2848-2857.  doi:10.11949/0438-1157.20230377
    Abstract ( 124 )   HTML ( 16)   PDF (3695KB) ( 194 )  
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    The dynamic mode decomposition method was used to study the pressure and vorticity fields obtained from numerical simulation of thermal mixing in a T-junction with a rotating impeller. By comparing the dynamic mode decomposition results of different blade numbers (2—4), the characteristic modes of the coherent structure of the flow field in a T-junction were obtained at a speed of 20 r/min under the condition of deflecting jet flow (MR=0.49). The diameter ratio of the main duct to branch duct is 2. By observing the spatial structure of the characteristic modes of pressure distribution, it is found that coherent structures mainly appear in the internal region of the impeller, the spatial structure of the characteristic mode of the vorticity field is mainly distributed at the blade tip, and a small amount of strip coherent structures appear near the duct wall. The second-order to fourth-order mode frequencies of the dominant pressure field and vorticity field are equal, corresponding to the 1st, 2nd, and 3rd harmonic frequencies of the blade passing frequency. Their fifth order mode frequencies tend to be equal as the number of blades increases. In addition, when the mode frequency is doubled by the blade passing frequency, “radial interference fringes” appear near the blade. The research results can provide theoretical guidance for flow control in T-junction channels.

    Flow process calculation and performance analysis of methane BOG ejector
    Chao NIU, Shengqiang SHEN, Yan YANG, Bonian PAN, Yiqiao LI
    2023, 74(7):  2858-2868.  doi:10.11949/0438-1157.20230237
    Abstract ( 118 )   HTML ( 3)   PDF (3155KB) ( 152 )  
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    The introduction of ejectors in the boil-off gas (BOG) reliquefaction system in a liquefied natural gas (LNG) carrier can save energy and improve system operating efficiency. Due to the special storage condition of LNG, it is important to design a high-performance ejector. The structural design calculation of methane BOG ejector under giving operating condition was carried out by using the gas dynamic method. Based on the Mixture multiphase flow model and SST k-ω turbulence model, a numerical model of methane BOG ejector was established. The effect of operating conditions and structural parameters on the entrainment performance of methane BOG ejector was calculated and analyzed. The results showed that for the ejector with a fixed structure, there is an optimal motive pressure for the entrainment ratio to reach the maximum. Increasing the induced pressure can always improve the entrainment ratio. Under giving design operating conditions, keeping other structural parameters fixed, the energy losses caused by shock waves and vortices inside the ejector is the lowest and the entrainment ratio reaches a maximum when the primary nozzle outlet diameter and primary nozzle outlet position are 9.6 mm and 41 mm, respectively.

    Investigation of enhanced boiling heat transfer on porous structural surfaces by high voltage electric field
    Hai WANG, Hong LIN, Chen WANG, Haojie XU, Lei ZUO, Junfeng WANG
    2023, 74(7):  2869-2879.  doi:10.11949/0438-1157.20230419
    Abstract ( 193 )   HTML ( 21)   PDF (6652KB) ( 155 )  
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    The porous micro-structured surfaces with different pore sizes were developed by adjusting electroplating current density and duration time. Pool boiling heat transfer performance of porous micro-structured surfaces under electric field was investigated by using mesh electrodes and dielectric fluid AE-3000. Through microscopic visualization measurement and boiling heat transfer characteristics experiments, boiling heat transfer enhancement of different porous micro-structured surfaces by electric field was analyzed. The experimental results indicated maximum heat transfer enhancement was achieved in the low heat flux region on the surface with small pore structures by high-voltage electric field. It was found when electric field intensity of 1600 kV/m was applied to the porous micro-structured surfaces in the low heat flux region, bubble detachment frequency could be increased by 5.11 times, and bubble detachment diameter could be decreased by 53.57%, as compared to those without electric field. The introduction of an active electric field can effectively solve the problems of difficulty in detachment of boiling bubbles on the surface of a small pore structure and high resistance to escape, improve the efficiency of detachment of bubbles, and enhance the performance of boiling heat transfer.

    Experimental study on the downward-facing surface enhanced boiling heat transfer of multiscale groove-fin structures
    Haopeng SHI, Dawen ZHONG, Xuexin LIAN, Junfeng ZHANG
    2023, 74(7):  2880-2888.  doi:10.11949/0438-1157.20230076
    Abstract ( 123 )   HTML ( 1)   PDF (2920KB) ( 348 )  
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    External pressure vessel cooling (ERVC) technology, as a technical means to achieve in-reactor melt retention (IVR) in nuclear reactors, needs to achieve higher heat transfer rates. This study used heated plate surfaces with different downward orientations to simulate the boiling heat transfer during ERVC process on the local area of the outer reactor pressure vessel (RPV) lower head, and the advanced additive manufacturing of cold spraying (CS-AM) was applied to directly fabricate multiscale groove-fin arrays on the heated surfaces. After going through downward-facing critical pool boiling experiments in the environment of atmosphere and saturated water, the boiling curves were obtained and compared with bare surface to evaluate the performance of enhancing boiling heat transfer. The results indicated that the mulitscale structured surfaces not only had excellent critical heat flux (CHF)-enhancing ability with more than 60% CHF increase over the bare surface, but also had better boiling heat transfer coefficient (BHTC) performance. In terms of thermal characteristics, the positive impact of the synergistic effect of multiscale structures on CHF was fully reflected. Significantly, this work provided an important basis for the application of CS-AM technology in the field of ERVC.

    Ferrofluid droplet neck self-similar breakup behavior
    Xuanzhi HE, Yongqing HE, Guiye WEN, Feng JIAO
    2023, 74(7):  2889-2897.  doi:10.11949/0438-1157.20230564
    Abstract ( 217 )   HTML ( 10)   PDF (2200KB) ( 345 )  
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    Control of the droplet generation process can be used to improve the efficiency of chemical processes such as mixing, extraction, and emulsification. This paper investigates the magnetic manipulation of ferrofluid droplet generation at the capillary in a liquid-liquid system. The continuous phase is dimethyl silicone oil with various viscosities, and the dispersed phase is a ferrofluid with a volume concentration of 3.6%. The study provides insight into the formation and breakup behavior of the ferrofluid droplet neck. We classified the different stages of droplet generation and analyzed the force processes: θ> 90°, the initial stage, where the interfacial tension dominates; θ< 90°, the necking stage, where the magnetic and viscous drag forces dominate. The magnetic force, viscous resistance and inertial force are dimensionless by interfacial tension. The changes of the limit length of the ferrofluid droplet, the thinning rate of the minimum neck diameter and its relative neck position under different magnetic Bond numbers, Weber numbers and Ohnesorge numbers are systematically studied. The results demonstrate that the droplet limiting length is inversely proportional to the magnetic force, proportional to the viscous drag, and independent of the inertial force (0.19 ≤ We ≤ 1.34). The minimum neck diameter thinning rate decreases with increasing viscous drag but is not affected by magnetic and inertial forces, exhibiting self-similar breakup behavior at different magnetic Bond and Weber numbers.

    Water-lubricated drag reduction and pressure drop model modification for heavy oil pipeline
    Yuying GUO, Jiaqiang JING, Wanni HUANG, Ping ZHANG, Jie SUN, Yu ZHU, Junxuan FENG, Hongjiang LU
    2023, 74(7):  2898-2907.  doi:10.11949/0438-1157.20230378
    Abstract ( 108 )   HTML ( 25)   PDF (1722KB) ( 67 )  
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    Based on a self-built water-lubricated heavy oil drag-reducing loop system, mineral oil and tap water with a viscosity ratio of 1176 and a density ratio of 0.9 were used to systematically study the effects of oil superficial velocity (0.12—0.93 m/s) and water superficial velocity (0.04—1.54 m/s) on the distribution of flow patterns, frictional pressure drop, and drag reduction effect in horizontal pipes. The applicability of the Rodriguez, Brauner, and Colombo models was evaluated. Considering the influence of oil core eccentricity, the Rodriguez model with the highest accuracy was modified around the mixed viscosity. The results indicate that annular flow is the main flow pattern in the experimental conditions. When the moisture content is between 0.04 and 0.93, there is always a minimum value in the pressure gradient, and it will increase in a parabolic form after exceeding this value. If the mixing flow rate is lower than the critical value, it will lead to a transition from annular flow/plug flow to stratified flow and the pressure drop will increase suddenly. A complete water film between the oil and the wall can effectively lubricate and reduce drag, with a maximum pressure reduction factor up to 73.1. A new calculation formula for mixed viscosity was provided, and the average relative error of the modified Rodriguez model is 3.89%.

    Catalysis, kinetics and reactors
    Effect of the morphology of Ru/α-MnO2 on NH3-SCO performance
    Pan LI, Junyang MA, Zhihao CHEN, Li WANG, Yun GUO
    2023, 74(7):  2908-2918.  doi:10.11949/0438-1157.20230420
    Abstract ( 174 )   HTML ( 15)   PDF (6544KB) ( 328 )  
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    α-MnO2 with different morphology, such as wire (w), tube (t) and rod (r) were synthesized as supports to prepare Ru/α-MnO2, and the effects of support morphology on the ammonia selective catalytic oxidation (NH3-SCO) were investigated. Meanwhile, the physical and chemical properties, redox properties and acidity of the catalysts were characterized by various methods. The exposed facet was closely related to the morphology of α-MnO2, for (110), (310) and (200) crystal planes were observed on the wire-, tube-, and rod-α-MnO2, respectively. The introduction of Ru improves the water resistance of the catalyst, and the tubular Ru/α-MnO2 has a NH3 conversion rate of 86% and a N2 selectivity of 98% under water vapor conditions. The effects of Ru on NH3-SCO activity performance was closely related to its effect on the surface acidity and redox property of α-MnO2. The addition of Ru reduced the surface acid amount of α-MnO2-w and thus lowered its activity, while the improved reducibility of Ru to α-MnO2-r compensated for the decreasing in the surface acid amount. However, for Ru/α-MnO2-t, the simultaneous increase in reducibility and surface acid amount by the presence of Ru was the main reason for the enhancement in NH3-SCO activity.

    Clean and efficient synthesis of accelerator CBS by hydrogen peroxide catalytic oxidation method
    Bin LI, Zhenghu XU, Shuang JIANG, Tianyong ZHANG
    2023, 74(7):  2919-2925.  doi:10.11949/0438-1157.20230406
    Abstract ( 145 )   HTML ( 8)   PDF (1262KB) ( 211 )  
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    At present, the industrial production of rubber accelerator CBS (N-cyclohexylbenzothiazole-2-sulphenamide) mainly adopts the sodium hypochlorite oxidation method. To solve the problem of high salt content, large discharge of wastewater and strong equipment corrosion in this process, using hydrogen peroxide as oxidant, the accelerator DM (2, 2'-dibenzothiazoledisulfde) was used as the raw material and oxidized together with cyclohexylamine to obtain the accelerator CBS. The effects of pH, oxidation reaction temperature, cyclohexylamine dosage, and catalyst type on the yield were studied. The optimal conditions are copper acetate as catalyst, n(DM)∶n(cyclohexylamine)=1∶4.9, the oxidation reaction temperature of 35℃, and pH 12. The yield of accelerator CBS reaches 94.6%, and the purity is 94.3%. Further, using accelerator M (2-mercaptobenzothiazole) as the raw material, oxidized by hydrogen peroxide to form accelerator DM, and then oxidized with cyclohexylamine to obtain accelerator CBS, established a new one-pot process for step-by-step oxidation of hydrogen peroxide with M as start material and DM as intermediate. In addition, the influence laws of key factors such as the oxidation reaction temperature in the first stage and the concentration of hydrogen peroxide in the first stage were explored. The results show that the total yield of accelerator CBS reaches 91.0%, and the purity is 94.8%. The optimal reaction conditions are as follows: the dosage of cyclohexylamine is n(M)∶n(cyclohexylamine)=1∶2.45, the first stage oxidation reaction temperature is 50℃ and the concentration of hydrogen peroxide is 30%, the second stage reaction conditions are the same as before.

    Biosynthesis of chiral epichlorohydrin by halohydrin dehalogenase based on Pickering emulsion system
    Xiaoling TANG, Jiarui WANG, Xuanye ZHU, Renchao ZHENG
    2023, 74(7):  2926-2934.  doi:10.11949/0438-1157.20230450
    Abstract ( 110 )   HTML ( 11)   PDF (2589KB) ( 111 )  
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    Biosynthesis of chiral epichlorohydrin (ECH) from 1,3-dichloro-2-propanol (1,3-DCP) catalyzed by halohydrin dehalogenases is an efficient and green synthetic route which exhibits advantages of mild reaction conditions, high atomic economy and environmental friendliness. Therefore, it has broad application prospects. Since the substrate and product in this route is easily to be degraded in aqueous phase, a two-phase system of water and organic solvents was applied. In order to improve the stability of the enzyme in organic solvents, a Pickering emulsion system was constructed with modified SiO2 as emulsifier for the enzyme-medicated biocatalysis of chiral ECH, and its catalytic performance was characterized. The results showed that the stability of the Pickering emulsion-based halohydrin dehalogenase in the water-organic solvent two-phase system was significantly improved, and its half-life was increased from 9.7 h to 20.1 h. After that, the reaction conditions were optimized and 50 mmol/L 1,3-DCP was effectively converted within 40 min. The yield of product (S)-ECH reached 93.6% with e.e. value of 95.3%. The obtained results laid the foundation for highly efficient biocatalytic synthesis of chiral ECH.

    Study on coke dissolution loss reaction and its mechanism based on molecular dynamics simulations
    Ji CHEN, Ze HONG, Zhao LEI, Qiang LING, Zhigang ZHAO, Chenhui PENG, Ping CUI
    2023, 74(7):  2935-2946.  doi:10.11949/0438-1157.20230207
    Abstract ( 151 )   HTML ( 9)   PDF (2695KB) ( 86 )  
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    In order to study the coke dissolution loss reaction and its mechanism at the molecular level, a molecular model of coke containing graphitized carbon and non-graphitized carbon was constructed by molecular dynamics and first principles. The accuracy of the model was verified by comparing the true density of the molecular model. The influence of charge density and pore structure on the coke dissolution loss reaction was analyzed, and the mechanism of the reaction was also discussed. The results show that the true density of the model is within the range of the measured true density of coke. The higher the graphitization degree of coke, the smaller the charge density around carbon atoms, and the lower the degree of dissolution loss reaction. The experimental results are similar to the simulation results. CO2 is mainly diffused in pores above 50 Å, with the lowest diffusion activation energy (131.24 kJ /mol), while it is mainly adsorbed in pores below 2 Å, with the highest adsorption energy (-192.54 kJ/mol). The mechanism of coke dissolution loss reaction includes the cracking reaction of graphitized carbon and non-graphitized carbon atoms, the isomerization reaction between two kinds of carbon atoms and the oxidation reaction between two kinds of carbon atoms and CO2. In the process of oxidation reaction, the ketene structure generated by the reaction of two kinds of carbon atom and CO2 will be cracked into CO due to its instability, which completes the reaction process.

    Separation engineering
    Study on selective extraction of nicotine by ionic liquids composite extractant and DFT calculation
    Yuanliang ZHANG, Xinqi LUAN, Weige SU, Changhao LI, Zhongxing ZHAO, Liqin ZHOU, Jianmin CHEN, Yan HUANG, Zhenxia ZHAO
    2023, 74(7):  2947-2956.  doi:10.11949/0438-1157.20230327
    Abstract ( 170 )   HTML ( 9)   PDF (4410KB) ( 257 )  
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    Aiming at the problem that ionic liquid has high viscosity and is not conducive to the separation of target substances in the application of extraction and separation, a strategy of ionic liquid-water composite extractant was proposed to extract nicotine from tobacco absolute. The extraction rate of nicotine by pure ionic liquids and ionic liquids-water composite extractant was investigated. Among them, [EMIm][BF4] and [EMIm][BF4]-H2O composite extractants have higher extraction rates of nicotine, 97.8% and 96.5%, respectively. At the same time, the interaction between ionic liquids, water and nicotine was analyzed. The effects of ionic liquids content, extraction time and extraction temperature on the extraction rate of nicotine were investigated. Under the optimal extraction conditions, the cyclic extraction performance of ionic liquids for nicotine was tested. The results showed that the extraction rate of nicotine by [EMIm][BF4]-H2O composite extractant was still as high as 93.4% after 5 cycles of extraction, and the recovery rate of [EMIm][BF4] was above 96%. Finally, the interaction strength of [EMIm][BF4]-H2O with nicotine and three main impurities (neophytadiene, ethyl hexadecanoate and linolenic acid) was analyzed, and the reason for the good selectivity of [EMIm][BF4]-H2O composite extractant to nicotine was explained.

    Study on the separation characteristics of a downstream gas-liquid vortex separator in a closed hood
    Jinming GAO, Yujiao GUO, Chenglin E, Chunxi LU
    2023, 74(7):  2957-2966.  doi:10.11949/0438-1157.20230363
    Abstract ( 124 )   HTML ( 7)   PDF (3311KB) ( 201 )  
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    To solve the escape phenomenon of small droplets entrained above the swirling arm in the gas-liquid vortex separator (GLVS), a downstream gas-liquid vortex separator in a closed hood (D-GLVS) was designed. The pressure drop characteristics and separation efficiency of D-GLVS were investigated in a large-scale cold separator model. The experimental results show that D-GLVS separates the separation space and exhaust space by adding a closed hood, resulting in a relatively large proportion of the exhaust pressure drop, about 60% of the total pressure drop. However, its resistance coefficient is still within the range of common cyclone separators. The separation efficiency increases first and then decreases with the increase of swirl arm velocity, and reaches the maximum near the swirl arm velocity of 14.69 m/s. The separation efficiency corresponding to the inlet mass of even nozzles is obviously higher than that of odd nozzles, which is also confirmed in the backward gas-liquid vortex separator (B-GLVS). The separation performance differences between D-GLVS and B-GLVS are further compared. The results show that the closed hood can optimize the internal airflow direction and greatly improve the escape of droplets from B-GLVS entrained by the airflow, leading to a significant increase in gas-liquid separation efficiency. The separation efficiency of D-GLVS is more similar to that of a common cyclone separator. At low gas velocity, the total pressure drop of the two is almost the same. When the gas velocity at the jet outlet of the spiral arm is higher, the total pressure drop of D-GLVS is slightly larger than that of B-GLVS, with an average increase of about 5.04%.

    Process system engineering
    Incipient fault detection method for chemical process based on ensemble learning transfer entropy
    Guang WANG, Fashun SHAN, Yucheng QIAN, Jianfang JIAO
    2023, 74(7):  2967-2978.  doi:10.11949/0438-1157.20230287
    Abstract ( 166 )   HTML ( 6)   PDF (3966KB) ( 247 )  
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    Traditional multivariate statistical analysis methods directly perform fault analysis on the mean and variance of process data. But as long as the monitoring statistics remain within the normal region surrounded by control limits, changes in the data distribution cannot be detected. To solve this problem, a method based on ensemble learning transfer entropy is proposed to obtain monitoring statistics and control limits based on this data set. Firstly, the transfer entropy is used to measure the information transfer between variables, and then the transfer entropy dataset is obtained through a sliding window, and the monitoring statistics and control limits are derived from this dataset. Then, the constructed indicators are ranked and binned using the rank sum ratio method, and the probability density parameters of the transfer entropy and the corresponding monitoring statistics of the part with good binning results are screened. Finally, the monitoring results are fused using an algorithm combining ensemble learning and Bayesian inference strategies to detect process faults in real-time. The method is used for fault detection of numerical examples and continuously stirred tank reactor processes and is compared with kernel principal component analysis, kernel independent component analysis, weighted statistical local kernel principal component analysis and weighted statistical feature kernel independent component analysis to verify that the proposed the method has good performance in detecting minor faults.

    Surge diagnosis method of centrifugal compressor based on multi-source data fusion
    Ye XU, Wenjun HUANG, Junpeng MI, Chuanchuan SHEN, Jianxiang JIN
    2023, 74(7):  2979-2987.  doi:10.11949/0438-1157.20230454
    Abstract ( 125 )   HTML ( 3)   PDF (1957KB) ( 281 )  
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    The centrifugal compressor is the key power equipment for oil refining and chemical production. Once it breaks down, it may cause major plant's accidents. Therefore, online equipment monitoring and fault diagnosis throughout the life cycle is conducive to the continuous and stable operation of plant. This paper proposes a surge diagnosis method for centrifugal compressor based on multi-source data fusion such as flow, pressure and vibration. First, the vibration data is decomposed into a specified number of sub band signals by using empirical wavelet transform and the signal is reconstructed according to the correlation order. Convolutional neural network is used to pre-diagnose the reconstructed vibration signal, flow signal and pressure signal, and the final diagnosis is made using the weighted D-S evidence theory for the normalized diagnosis results of the three signals. Through the experiment of surge simulation test on centrifugal compressor, the diagnosis accuracy can reach 97.25% by using the multi-source fusion fault diagnosis method proposed in this paper. Compared with the use of single sensor data, this method significantly improves the fault tolerance ability of diagnosis, and it has higher diagnosis accuracy compared with other methods.

    Design and optimization of cryogenic air separation process with dividing wall column based on self-heat regeneration
    Zhaolun WEN, Peirui LI, Zhonglin ZHANG, Xiao DU, Qiwang HOU, Yegang LIU, Xiaogang HAO, Guoqing GUAN
    2023, 74(7):  2988-2998.  doi:10.11949/0438-1157.20230240
    Abstract ( 286 )   HTML ( 12)   PDF (1612KB) ( 279 )  
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    Industrial gases commonly obtained by cryogenic distillation are widely used currently. The energy consumption of the process is always huge, and the energy consumption of compression and rectification accounts for the largest proportion. A cryogenic air separation process with a dividing wall column was proposed based on the self-heat regeneration, in which the double-tower distillation air separation process was replaced by a single-tower distillation process applying the self-heat regeneration technology to complete the process of heat exchange. The energy of the process was analyzed by the pinch principle, and the total energy consumption (TEC), carbon dioxide emissions ([CO2]em), and total annual cost (TAC) were evaluated, respectively. The results showed the cryogenic air separation process based on the self-heating regeneration in the dividing wall column reduced energy consumption for oxygen production by 26.19%, CO2 emission by 25.18%, and the TAC by 31.93%. The optimized air separation process using self-heat regeneration technology and dividing wall column technology has shown stronger advantages in energy saving, economy, and environmental protection.

    Process design and evaluation of CO2 to methanol coupled with SOEC
    Guixian LI, Abo CAO, Wenliang MENG, Dongliang WANG, Yong YANG, Huairong ZHOU
    2023, 74(7):  2999-3009.  doi:10.11949/0438-1157.20230519
    Abstract ( 194 )   HTML ( 17)   PDF (2338KB) ( 314 )  
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    The utilization of CO2 coupled with renewable energy in electrolytic hydrogen production for synthesizing high-energy-density methanol products not only reduces CO2 emissions but also enhances the on-site absorption capacity of intermittent and fluctuating renewable energy sources. In this study, a novel process called SOEC-CO2tM, which couples solid oxide electrolysis cell (SOEC) with CO2-to-methanol synthesis, is proposed. This process involves hydrogen production by SOEC, flue gas CO2 capture, methanol synthesis, and refining units. Based on comprehensive process simulation data, heat integration design and optimization are carried out, and the technical and economic evaluation of the new process is carried out by using energy efficiency, investment, production cost, etc., and a comparative analysis is made with the traditional coal-to-methanol process and the green hydrogen coupled coal-to-methanol process. The results demonstrate that before energy integration, the process energy consumption is 420.05 MW, which is reduced to 254.88 MW after energy integration, resulting in a decrease of 39.32% in energy consumption. The energy utilization efficiency of the SOEC-CO2tM process is 62.94%, comparable to that of the coal-based methanol synthesis coupled with green hydrogen, and 1.46 times higher than that of the traditional coal-based methanol synthesis. The total capital investment of unit methanol for the new process is 2964.68 CNY/t, with a production cost of 3742 CNY/t, where electricity cost constitutes 64.7% of the production cost. In the future, with the vigorous development of renewable energy, the economic performance of the new process will become more prominent. It has the potential to sequester 2 million tons of CO2 annually and utilize 1245 MW of renewable electricity. The traditional coal-based methanol synthesis process has a CO2 emission intensity of 2.66 t/t. Compared to the traditional coal-based methanol synthesis, the new process exhibits significant advantages in carbon reduction and on-site utilization of renewable energy.

    Surface and interface engineering
    Preparation and performance evaluation of magnolol-based epoxy resin anti-corrosion coatings
    Jing ZHAO, Chengwen GU, Xigao JIAN, Zhihuan WENG
    2023, 74(7):  3010-3017.  doi:10.11949/0438-1157.20230492
    Abstract ( 181 )   HTML ( 12)   PDF (2026KB) ( 121 )  
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    Using epichlorohydrin and bio-based compound magnolol as raw materials, magnolol epoxy resin (DGEM) was prepared by one-step reaction, and polyetheramine D230 was used as curing agent to prepare anti-corrosion coating containing mica powder. Comprehensive analyses and characterizations were performed by using multiple techniques, including infrared spectroscopy, wear resistance testing, thermogravimetric analysis, differential scanning calorimetry, electrochemical workstation, pencil hardness testing, and impact testing. The effects of varying mica powder filler content on the corrosion resistance of the coating were investigated. The results revealed that the addition of 3% (mass) mica powder filler significantly enhanced the mechanical and corrosion resistance properties of the DGEM-D230 coating. Specifically, the DGEM-D230-3% exhibited a pencil hardness of 4H, an impact strength of 30 cm, an electrochemical impedance value of 8.47×108 Ω∙cm2, a residual carbon yield of 37.1% at 800°C under a nitrogen atmosphere, and a flexibility of 0.5 mm, with 0-level adhesion, surpassing those of the pure DGEM-D230 coating. These findings highlight the potential of DGEM-D230-3% coating as a promising corrosion-resistant coating for various applications.

    Energy and environmental engineering
    Drying characteristics and mathematical model of CaO-conditioned oil sludge
    Chunyu LIU, Huanyu ZHOU, Yue MA, Changtao YUE
    2023, 74(7):  3018-3027.  doi:10.11949/0438-1157.20230367
    Abstract ( 139 )   HTML ( 4)   PDF (3645KB) ( 157 )  
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    Thermal drying technology is one of sludge pretreatment technologies. To improve drying efficiency and reduce energy consumption, CaO was added to the oil sludge, and the microstructural changes were observed. The effects of temperature and CaO on oil sludge drying characteristics were analyzed, and the drying model of CaO-conditioned oil sludge was established. The results show that the added CaO is concentrated within the pore structure of oil sludge and increases the pore space, so moisture evaporates more easily from the pore channels. The evaporation of water is mainly concentrated in the fast drying stage, and drying at 100℃ retains the most organic matter in CaO-conditioned oil sludge. CaO shows facilitating effects on the drying process, reduces the total drying time significantly, and the optimal CaO addition ratio is 10%—12%. Page model can be used to describe the CaO-conditioned oil sludge drying process, and the effective moisture diffusion coefficient Deff obtained by Fick's second law varies from 0.9581×10-8 m2/s to 3.3395×10-8 m2/s. The Deff reaches the maximum when the CaO content is 10%. Considering the drying rate and economic benefit, the optimum drying conditions of oil sludge are at 100—120℃ and adding 10%—12% CaO.

    Experimental study on dielectric properties of coal ash based on coplanar capacitance principle
    Mengbin ZHANG, Rui LI, Jiajie ZHANG, Suxia MA, Jiansheng ZHANG
    2023, 74(7):  3028-3037.  doi:10.11949/0438-1157.20230339
    Abstract ( 109 )   HTML ( 7)   PDF (3431KB) ( 78 )  
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    Aiming at the demand of ash deposition monitoring in industrial boiler, the capacitance characteristics of ash at high temperature were tested based on the principle of coplanar capacitance. The phase structure and microstructure of quenched ash were analyzed by XRD and SEM, and the effects of temperature, frequency and composition on the dielectric properties of ash were analyzed by broadband dielectric spectrometer. The results show that with the increase of temperature (>700℃), magnesia-iron spinel is formed in the ash phase and the grain size increases gradually. The complex impedance spectrum of the ash conforms to the IBLC dielectric model, resulting in a gradual increase in the dielectric constant and test capacitance of the ash slag. The capacitance value of the reference slag at 1200℃ is about 282.0 times that of 700℃. The change of Si/Al has little effect on the dielectric properties of ash. With the increase of Fe2O3 content or the decrease of CaO content, the grain size in ash gradually increases, resulting in the increase of dielectric constant, so the test capacitance value increases.

    Study on electro-osmotic dewatering of sludge assisted by activated carbon/graphite
    Yuanhao QU, Wenyi DENG, Xiaodan XIE, Yaxin SU
    2023, 74(7):  3038-3050.  doi:10.11949/0438-1157.20230354
    Abstract ( 135 )   HTML ( 10)   PDF (4615KB) ( 99 )  
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    Using activated carbon, graphite, and their mixtures in different proportions as additives, the mechanism of influence of different proportions of additives on sludge electro-osmotic dewatering performance and filtrate quality (total organic carbon (TOC) content, heavy metal concentration, organic composition, etc.) was studied. The results indicated that both graphite and activated carbon can increase the dewatering performance and conductivity of sludge. Compared with graphite, activated carbon showed the most obvious impact on lowering the moisture content of sludge cake. The optimal dewatering performance was achieved when the dose of carbon materials was set at 5% of dry sludge mass (DS), and the real moisture content of sludge cake was decreased from 46.0%(mass) to 42.2%(mass), while the apparent moisture content was decreased to 41.0%(mass). The addition of activated carbon or graphite can significantly reduce the TOC and heavy metal concentration of cathodic electrodialysis, the effect of activated carbon is the best, and the effect of graphite is the weakest. The TOC content of the cathodic filtrate decreased from 3740.4 mg/L to 2160.0 mg/L when the dose of activated carbon was increased from 0%DS to 20%DS, whereas the concentrations of heavy metals like Cu, Mn, Cr, Ni, Cd, Zn, Hg, and Pb decreased by 57%—100%. The research findings will provide fundamental data support for enhancing sludge electro-dewatering through carbon-containing materials and establish a theoretical foundation for the promotion and application of sludge electro-osmotic dewatering technology.

    Material science and engineering, nanotechnology
    Preparation and properties of polyether-based vinylogous urethane reversible crosslinked polymers
    Jie LIU, Lisheng WU, Jinjin LI, Zhenghong LUO, Yinning ZHOU
    2023, 74(7):  3051-3057.  doi:10.11949/0438-1157.20230510
    Abstract ( 185 )   HTML ( 9)   PDF (2638KB) ( 179 )  
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    Reversible crosslinked polymers, also known as covalent adaptable networks (CANs) based on vinylogous urethane were fabricated by condensation between bis-acetoacetate terminated polyether and tris (2-aminoethyl)amine. Three different bis-acetoacetate terminated polyethers with different repeat-units but similar molecular weight were synthesized. The effects of building block on the network structure, thermal and mechanical properties, and viscoelastic behaviors of CANs are examined. The results indicate that higher flexibility of the building blocks enables easier movement of chains in the network, leading to larger ductility, and lower modulus of the resulting CAN. In addition, the network topology rearrangement of the dynamic network is faster and the stress relaxation time is shorter at high temperature. Furthermore, the activation energies of vinylogous urethane CANs exhibit dual temperature response, which is distinguished from the CANs based other dynamic chemistries that are typically have a single linear relationship with temperature.

    Synthesis of FeF3 nanoparticles covered by vertical porous carbon for high performance Li-ion battery cathode
    Jiali GE, Tuxiang GUAN, Xinmin QIU, Jian WU, Liming SHEN, Ningzhong BAO
    2023, 74(7):  3058-3067.  doi:10.11949/0438-1157.20230437
    Abstract ( 213 )   HTML ( 21)   PDF (3911KB) ( 395 )  
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    The development of low-cost, high-performance cathodes is one of the major research goals for next-generation rechargeable lithium and lithium-ion batteries. As a promising alternative to traditional intercalated electrode materials, metal fluorides offer much higher theoretical capacity and energy density than conventional cathodes. Herein, a self-assembled iron fluoride/carbon/porous graphene oxide (FeF3/C/HRGO) cathode material covered by vertical porous carbon structure was designed and fabricated. This vertical porous carbon structure presents a double-layer carbon-clad frame with primary and secondary carbon-clad layers. Among them, the primary carbon shell generated by glucose wraps around FeF3 nanoparticles which effectively inhibits the growth of particle volume during fluorination process. Meanwhile, the porous conductive network in the secondary carbon-clad layer significantly shortens the transport path of Li+ and increase the electronic conductivity. As a result, the FeF3/C/HRGO electrode delivered an excellent reversible capacity of 406 mAh·g-1 after 200 cycles at 0.1 A·g-1.

    Preparation and properties of polyelectrolyte electrostatic deposition modified PHBV antioxidant films
    Jie WANG, Xiaolin QIU, Ye ZHAO, Xinyang LIU, Zhongqiang HAN, Yong XU, Wenhan JIANG
    2023, 74(7):  3068-3078.  doi:10.11949/0438-1157.20230383
    Abstract ( 86 )   HTML ( 3)   PDF (2493KB) ( 74 )  
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    Transition metal ions in food can catalyze the oxidation of lipids and lead to food quality degradation, so it has great significance to carry out antioxidant packaging research. In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films covered with poly(acrylic acid) (PAA) graft layer as the substrate, chitosan (CS) and sodium alginate (SA) as polyelectrolytes were used to produce PHBV-g-PAA/(CS/SA) n non-release antioxidant packaging films with metal chelating ability by layer self-assembly method. The effects of polyelectrolyte solution concentration and pH on the chemical properties, microscopic morphology, active group content and Cu() ion chelating ability of the active membranes were investigated. The results show that the active films were characterized by Fourier transform infrared spectroscopy with acid orange 7 staining, demonstrating that CS and SA polyelectrolytes have been successfully assembled alternately onto the surface of PHBV-g-PAA films. It was found that the thickness of the assembled layer increased with the growth of the polyelectrolyte solution concentration and pH by SEM. When the concentration of CS and SA polyelectrolyte solutions was 1.0 mg/ml and the pH was 5.0 and 7.0 respectively, the polyelectrolyte assembly layer was more uniform and flat. At this time, the surface amino density of the active film was 136.38 nmol/cm2 and the amount of Cu(Ⅱ) ions chelated was 124.93 nmol/cm2. The active film has a certain antioxidant capacity and was higher than PHBV and PHBV-g-PAA films, which has a broad application prospect in the field of food packaging.

    Low modulus, high elasticity and high peel adhesion acrylate pressure sensitive adhesives
    Ao ZHANG, Yingwu LUO
    2023, 74(7):  3079-3092.  doi:10.11949/0438-1157.20230381
    Abstract ( 317 )   HTML ( 7)   PDF (3632KB) ( 233 )  
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    Acrylate pressure sensitive adhesives are widely used in the assembly of electronic devices. With the development of flexible electronics such as foldable phone, traditional pressure sensitive adhesives fail to meet the needs of flexible electronics for repeated deformation due to the trade-off effect among low modulus, high elasticity and high peel adhesion. The poly(styrene-b-2-ethylhexyl acrylate-b-styrene) (SEHAS) and poly(styrene-b-2-ethylhexyl acrylate) (SEHA) copolymers of styrene and 2-ethylhexyl acrylate were prepared by design via RAFT emulsion polymerization. The mechanical properties, viscoelasticity and adhesion properties of SEHAS/SEHA blends were studied. By adjusting the blending ratio of SEHAS/SEHA from 100/0 to 25/75, it was found that the glass transition temperature remained unchanged at -68℃, the shear storage modulus decreased from 27 kPa to 15 kPa, the peel strength increased from 8.1 N/25 mm to 10.3 N/25 mm, and the strain recovery ratio remained above 95%. SEHAS/SEHA blending turns out to be a new and facile method to significantly reduce the modulus while maintain the integrality of a network and improve viscoelasticity. Thus, very soft pressure sensitive adhesives with good elasticity and adhesion can achieve.

    Enhanced phase change energy storage/release properties by combining porous materials and water-based carbon nanotube under magnetic regulation
    Meibo XING, Zhongtian ZHANG, Dongliang JING, Hongfa ZHANG
    2023, 74(7):  3093-3102.  doi:10.11949/0438-1157.20230359
    Abstract ( 98 )   HTML ( 6)   PDF (5414KB) ( 187 )  
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    In this paper, a porous material composite water-based magnetic multi-walled carbon nanotubes (MWCNT) is used to enhance the solidification/melting phase transition process. The magnetic modification of MWCNT was carried out by coating Fe3O4 on the sidewall of MWCNT, and the synergistic effect of the porous material properties and the solidification/melting properties of the water-based MWCNT phase change working fluid under the influence of a magnetic field was investigated experimentally. The results show that the thermal cycle time of the composite phase change materials with the addition of porous materials such as expanded graphite, nickel metal foam and copper metal foam were reduced by 30.9%, 15.6% and 36.9% respectively compared to pure water. The storage/release capacity of phase change materials increased with the increase of porosity and the decrease of pore density of copper metal foam. Under the action of 75 mT magnetic field, the water-based magnetic MWCNT with a concentration of 0.08% (mass) composite copper metal foam with the porosity of 95% and a pore density of 5 PPI has the highest cold storage/release capacity and average rate compared with other specifications of copper metal foam. Compared with pure water, the thermal cycling time decreased by 38.9%, the average rate increased by 50.3%, and the supercooling decreased by 74.4%. However, the storage/release capacity only decreased by 4.7% and 4.9%.

    High-efficient preparation of cardanol-based self-healing microcapsules
    Wentao WU, Liangyong CHU, Lingjie ZHANG, Weimin TAN, Liming SHEN, Ningzhong BAO
    2023, 74(7):  3103-3115.  doi:10.11949/0438-1157.20230320
    Abstract ( 135 )   HTML ( 8)   PDF (5678KB) ( 190 )  
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    The efficient preparation of bio-based microcapsules is of great significance for the development of bio-based self-healing coatings. To solve the issue that traditional petroleum-based surfactants cannot effectively encapsulate biological healing agents such as cardanol-based epoxy resins and curing agents, it is reported that cardanol-based surfactants can be used as an emulsifier in the preparation of microcapsules. Using the solvent evaporation method, bio-based microcapsules with polymethyl methacrylate as the shell have been efficiently prepared. Based on the solvent volatilization mechanism, a hypothesis has been proposed to explain the efficient packaging of cardanol-based emulsifiers. The morphology of the microcapsules was analyzed by scanning electron microscopy, and the stability and size distribution of the microcapsules were analyzed by thermogravimetry and laser particle size analyzer. By systematic optimization of process parameters such as emulsifier concentration, the ratio of core to the wall, stirring speed, and temperature, bio-based microcapsules with controllable particle size, mono dispersibility, and spherical structure were prepared. The results show that the microcapsules prepared at evaporation temperature of 40℃ and core-wall ratio of 1∶1 have better surface morphology, and there are regular effects between emulsifier concentration, stirring speed and average particle size. Moreover, the healing efficiency of the self-healing coating embedded with 20%(mass) bio-based microcapsules reaches 61.25%. The application of bio-based surfactants in the high-efficient preparation of bio-based microcapsules may guide the development of bio-based self-healing coatings and contribute to the replacement of petroleum-based materials with bio-based materials in the coating field.

    Effect of electrolyte types on the storage behaviors of anions and cations for dual-ion batteries
    Mengmeng ZHANG, Dong YAN, Yongfeng SHEN, Wencui LI
    2023, 74(7):  3116-3126.  doi:10.11949/0438-1157.20230015
    Abstract ( 115 )   HTML ( 9)   PDF (3395KB) ( 133 )  
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    Dual-ion batteries (DIBs) have attracted extensive attention due to the virtues of high working voltage, low cost and environmental friendliness. However, the high voltage characteristics of the positive electrode will cause the electrolyte to oxidize and decompose. Since the electrolyte acts as the only source of active charge carriers, the electrochemical performance is limited by long-term decomposition and gas production of the electrolyte. We herein systematically investigate the effects of electrolyte concentration and types on the PF6- intercalation behaviors and the compatibility between solvent composition and anodes by adjusting electrolyte concentration and solvent composition. The linear ethyl methyl carbonate (EMC) solvent is more favorable for the PF6- to insert into the graphene layers than cyclic ethylene carbonate (EC) solvent. Moreover, EC solvent is the key component for the stability of anode. The mixed electrolyte of 1 mol·L-1 LiPF6-EC/EMC (3∶7, volume ratio) with the combination of linear EMC and cyclic EC is more applicable for DIBs, and the graphite//soft carbon DIB configuration assembled by the above electrolyte can provide an energy density of 98 W·h·kg-1 at a power density of 580 W·kg-1 with a capacity retention rate of 86.9% after 1000 cycles at 1 A·g-1.

    Influence of mixing time and sequence on the dispersion properties of the cathode slurry of lithium-ion battery
    Zhilong WANG, Ye YANG, Zhenzhen ZHAO, Tao TIAN, Tong ZHAO, Yahui CUI
    2023, 74(7):  3127-3138.  doi:10.11949/0438-1157.20230528
    Abstract ( 308 )   HTML ( 17)   PDF (7637KB) ( 156 )  
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    This paper comprehensively used electrical impedance spectroscopy (EIS) method, scanning electron microscopy (SEM) method and rheological method to analyze the electrochemical, morphological and rheological properties of the cathode slurry of lithium-ion battery, as a result, the dispersion properties of the cathode slurry are summarized. In addition, based on the COMSOL Multiphysics software, a static simulation model of the cathode slurry was established, and the correctness of the EIS experimental results was verified from the perspective of electrochemical characteristics. Taking into account experiment analysis and simulation verification, the results show that stirring time has a significant impact on the dispersion properties of the cathode slurry, and more (more than 9 min) or less (less than 3 min) stirring time is able to increase the impedance value and deteriorate the dispersion of particles in the positive electrode slurry, while 6 min stirring time is able to reduce the impedance value, thereby dispersing the particles in the cathode slurry. Carbon black (CB) is pre-mixed with PVDF-NMP solution to form CB slurry, and then lithium cobalt oxide (LiCoO2) particles are mixed with CB slurry to form cathode slurry. This slurry preparation order enables cathode slurry to have good dispersion properties. Finally, this paper proposed a slurry preparation scheme to improve the dispersion properties of cathode slurry with the aim of providing theoretical basis and experimental reference for the preparation of high-performance lithium batteries.

    Process safety
    Effect of spiral microchannel on detonation propagation of hydrogen-doped methane
    Xiaoyang LIU, Jianliang YU, Yujie HOU, Xingqing YAN, Zhenhua ZHANG, Xianshu LYU
    2023, 74(7):  3139-3148.  doi:10.11949/0438-1157.20230365
    Abstract ( 165 )   HTML ( 6)   PDF (2752KB) ( 297 )  
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    To explore the detonation propagation characteristics of CH4/H2 binary fuel mixture system in complex structure pipeline, this paper studies the detonation failure and re-initiation characteristic behavior of CH4/H2-O2 mixture under the disturbance of continuous elbow (spiral structure). The variation of flame velocity and cell structure is measured by using photoelectric detection technology and smoke trace technology by varying the hydrogen ratio and initial pressure. The experimental results show that the spiral structure has an inhibitory effect on the propagation of detonation waves. The propagation process of detonation flame before and after passing through the spiral tube can be divided into three stages: acceleration, deceleration, and re-initiation. The addition of H2 can effectively improve the detonation sensitivity of the premixed gas and reduce the velocity loss of the flame through the spiral tube. When the hydrogen ratio exceeds 50%, the change of velocity loss is less affected by the hydrogen ratio. The increase of initial pressure can also reduce the velocity loss of the flame. As the initial pressure increases from 50 kPa to 200 kPa, the velocity deficit decreases by 40.5%. The existence of the spiral tube reduces the initiation energy of re-initiation and increases the detonation cell size.