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Table of Content
05 February 2021, Volume 72 Issue 2
    Reviews and monographs
    Development and applications of reaction density functional theory
    TANG Weiqiang, XIE Peng, XU Xiaofei, ZHAO Shuangliang
    2021, 72(2):  633-652.  doi:10.11949/0438-1157.20201860
    Abstract ( 902 )   HTML ( 64)   PDF (5519KB) ( 581 )  
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    It is an important issue in green chemistry to improve the selectivity and conversion rate of chemical reactions. Most chemical reactions occur in solution. Solvent plays an important role in determining reaction rate, equilibrium process, and the reaction mechanism. Theories and methods that could describe solvent effect quantitatively in molecular scale are still lacking. This review collects the theoretical models developed in recent years and highlights the reaction density functional theory (RxDFT) recently proposed by our group. The applications of RxDFT in the aqueous solution, organic solution, interfacial system, and confined system are introduced. The effects of different reacting environments on the free energy profiles of chemical reaction are analyzed, and the mechanisms of solvent effect are summarized. In addition, the construction of self-consistent reaction density functional theory (sc-RxDFT), reaction-diffusion coupling, polymer reaction density functional theory, and the application of RxDFT in the screening of reacting solvents, interface reactions and electrolyte design for electrochemistry batteries are prospected.

    Reversible deactivation radical interfacial polymerization
    ZHAO Yuhai, LUO Yingwu
    2021, 72(2):  653-668.  doi:10.11949/0438-1157.20201306
    Abstract ( 605 )   HTML ( 14)   PDF (6487KB) ( 249 )  
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    Interfacial polymerization generally refers to polymerization confined to liquid-liquid or liquid-solid interfaces. Interfacial polymerization had occurred in some specific cases of highly reactive condensation polymerization. Since 1990s, reversible deactivation radical polymerizations (RDRPs) represented by RAFT polymerization and ATRP have been developed into powerful tools to precisely tailor-make microstructures of polymer chains. Besides polymer chains, precise nanostructures have been synthesized robustly from RDRP-based interfacial polymerization. In the current mini-review, we introduce how to create a RDRP-based interfacial polymerization, summarize the up-to-date status of the available nanostructures and promising application fields in nanocapsules, nano-dispersion and polymer brush surface from interfacial RDRPs.

    Research progress on preparation, regulation and application of waterborne superhydrophobic coatings
    WANG Huaiyuan, LIN Dan, ZHANG Xiguang, YUAN Sicheng
    2021, 72(2):  669-680.  doi:10.11949/0438-1157.20200690
    Abstract ( 925 )   HTML ( 42)   PDF (4396KB) ( 682 )  
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    Based on the requirements of sustainable development and environmental protection, novel waterborne superhydrophobic coatings that use water instead of organic volatile solvents have gradually attracted substantial attention from scientists. However, related problems such as the dispersibility of water-based coatings, the hydrophobic stability of the coating, and the coating performance have also followed. In this work, the progress on the preparation method of waterborne superhydrophobic coatings is introduced.The feasible solutions related to the poor mechanical durability of waterborne superhydrophobic coatings are proposed, such as preparing an integrated composite structure with internal and external consistency, enhancing the interfacial interaction in the coating or designing a self-healing waterborne superhydrophobic coating. In addition, the research progress of waterborne superhydrophobic coatings in the fields of oil-water separation, anti-icing, self-cleaning and so forth in recent years have been described. The large-scale preparation of waterborne superhydrophobic coating, the enhancement of coating mechanical properties and the study of durability will become the main exploration direction in the future. The industrial applications of waterborne superhydrophobic coatings would be broken through by deepening their basic research.

    Preparation and applications in electronic materials of metallic nanowires
    LIU Qing, DAI Xiaofeng, ZHANG Teng, SHI Hongbin, ZHANG Yabing, WANG Tao
    2021, 72(2):  681-708.  doi:10.11949/0438-1157.20200631
    Abstract ( 736 )   HTML ( 28)   PDF (8343KB) ( 278 )  
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    As the development of integration and flexibility of electronic devices, the traditional tin-lead solders, indium tin oxide (ITO) films and other materials no longer meet the requirements of properties, such as electric conductivity, thermal conductivity and flexibility. Metallic nanowires have excellent photoelectric properties and unique one-dimensional structure. New materials with them as key components have become the most potential substitutes for traditional electronic materials. The commercialization of metallic nanowires involves the aspects of raw material, equipment, process and application. However, the key technique lies in the large-scale, low-cost, green and efficient preparation of metallic nanowires. In this paper, the preparation methods of metallic nanowires are reviewed, including physical vapor deposition, chemical vapor deposition, template assisted, solvothermal process and polyol method. The applications of metallic nanowires in the field of electronic materials, such as conductive adhesives, transparent conductive films and thermal interface materials are summarized.

    Research progress in polymer-metal-organic frameworks
    ZHANG Jiahe, YUAN Ye, WANG Ming, WANG Zhi, WANG Jixiao
    2021, 72(2):  709-726.  doi:10.11949/0438-1157.20201415
    Abstract ( 845 )   HTML ( 33)   PDF (6216KB) ( 627 )  
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    Metal-organic frameworks (MOFs) have received extensive attention due to their advantages such as large porosity, high specific surface area, and regular and adjustable pore structure. The processability of MOFs is limited by poor thermoplasticity and mechanical properties, which seriously handicaps their further industrial application. In order to solve this problem, researchers used polymers as a component of porous materials to synthesize a three-dimensional and highly porous monolithic material—polyMOFs by direct or indirect methods. PolyMOFs can combine the excellent functionality of MOFs with the processability of polymers, and have broad application prospects in the fields of gas separation, biomedicine, and catalysis. In this paper, three synthetic methods of polyMOFs are reviewed, including postsynthetic polymerization and single-crystal to single-crystal transformations and direct synthesis. The characteristics and shortcomings of the three methods are summarized, and the future development direction of polyMOFs is prospected.

    Research progress of solvent-resistant composite nanofiltration membrane
    HE Pengpeng, ZHAO Song, MAO Chenyue, WANG Zhi, WANG Jixiao
    2021, 72(2):  727-747.  doi:10.11949/0438-1157.20200792
    Abstract ( 790 )   HTML ( 20)   PDF (5063KB) ( 432 )  
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    Solvent-resistant nanofiltration is a new type of membrane separation technology used for the separation of organic mixtures. Commercial solvent-resistant nanofiltration membranes are mostly asymmetric membranes with integral skin layers prepared by phase inversion, with thicker skin layers and low flux. The solvent-resistant composite nanofiltration membrane is composed of a support membrane and a separation layer, and has the advantages of thin skin layer, high solvent flux and high solute rejection rate, so it is widely used in the field of solvent-resistant nanofiltration. Therefore, the preparation and modification of solvent-resistant composite nanofiltration membranes have become research hotspots in recent years. In this paper, the research progress of solvent-resistant nanofiltration membranes are firstly introduced from six aspects including interfacial polymerization, surface coating, layer-by-layer self-assembly, in situ growth, organic-inorganic hybridization and surface modification. And then, we propose the development prospects of solvent-resistant composite nanofiltration membranes.

    Research progress of hydrogen sulfide deep adsorption materials
    YU Tao, WANG Yundong, LIU Zuohua, MA Jianxiu, JING Yu
    2021, 72(2):  748-760.  doi:10.11949/0438-1157.20201063
    Abstract ( 958 )   HTML ( 25)   PDF (2228KB) ( 547 )  
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    At present, hydrogen sulfide (H2S) has increasingly become an important factor restricting the development of industrialization. Even at a low concentration, it will still damage the environment and corrode equipment. The deep purification of sulfur-containing gas by using an environmental and efficient method has gained the attention of researchers on domestic and overseas. Adsorption desulfurization has a good prospective because of its deep removal, high efficiency, environmental-friendly performance and good regeneration. The key of adsorption desulfurization is to develop an adsorbent with good selectivity, large adsorption capacity, stable performance and good reproducibility. This paper summarizes the recent advances in several adsorbent materials such as carbon-based materials, porous metal oxides, zeolite and metal-organic frameworks (MOFs), making a comment on the future development directions of deep removal of H2S, aiming at providing a reference for further research.

    Application of continuous micro-reaction hydrogenation technology in deprotection reaction
    LOU Fengyan, YIN Jiabin, DUAN Xiaonan, WANG Qining, AI Ning, ZHANG Jisong
    2021, 72(2):  761-771.  doi:10.11949/0438-1157.20201299
    Abstract ( 551 )   HTML ( 26)   PDF (1664KB) ( 413 )  
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    Protection and deprotection is a common organic synthesis strategy in fine chemical fields such as pharmaceutical intermediates. The commonly used protecting groups are benzyl and benzyloxycarbonyl, which can be removed by catalytic hydrogenation. The conventional high-pressure hydrogenation batch reactors have several drawbacks, such as low mass and heat transfer rate, poor operation safety and slow hydrogenolysis rate. The continuous hydrogenation for heterogeneous catalytic deprotection can achieve high selectivity and significantly shorten the reaction time due to the excellent gas-liquid mass transfer and plug flow characteristics. This paper summarizes the advantages of continuous flow hydrogenation technology in deprotection reaction and its applications in the synthesis of pharmaceutical intermediates, and discusses the effects of catalyst and solvent on the deprotection reaction. Finally, the application of continuous microreaction hydrogenation technology in deprotection is prospected.

    Progress on droplet formation mechanism in non-Newtonian fluids in microchannels
    LIU Xiyang, FU Taotao, ZHU Chunying, MA Youguang
    2021, 72(2):  772-782.  doi:10.11949/0438-1157.20200994
    Abstract ( 596 )   HTML ( 15)   PDF (2164KB) ( 333 )  
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    Good controllability of microfluidic technology provides a new way to prepare uniform and controllable microdroplets, and non-Newtonian fluids have attracted attention due to their wide application. In recent years, the research progress of droplet formation mechanism in two typical non-Newtonian fluids, namely shear thinning and viscoelasticity, is reviewed. Around the two typical microchannel structures of flow-focusing and T-shaped microchannels, the dynamics of the interface evolution in the droplet generation process when shear-thinning and viscoelastic fluids are used as the dispersed and continuous phases respectively were introduced. Compared with the droplet generation process of Newtonian fluids, the effects of shear-thinning and elasticity on the generation of main droplets and satellite droplets were analyzed. The key scientific problems to be solved in the process of non-Newtonian fluids droplet generation were pointed out, providing reference for further simulation and experimental research.

    Progress on surfactant and interfacial transport phenomena in microchannels
    LIU Langyu, ZHU Chunying, MA Youguang, FU Taotao
    2021, 72(2):  783-798.  doi:10.11949/0438-1157.20201094
    Abstract ( 465 )   HTML ( 14)   PDF (5024KB) ( 388 )  
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    Surfactants play an important role in microfluidic applications, often accompanied by dynamic interfacial tension. The research progress of multiphase flow containing surfactants in microchannels is reviewed, and the relationship between droplet size, liquid rheology, pressure drop and dynamic interfacial tension in microfluidics is analyzed. The interfacial transport phenomena under the action of surfactants, such as the formation, movement, deformation, breakup and coalescence of bubbles and droplets are summarized. The adsorption kinetics of surfactants in microfluidics are reviewed, and research directions in this field for the future are prospected.

    Progress in separation of monovalent/divalent inorganic salt solutions by nanofiltration
    YANG Fengrui, WANG Zhi, YAN Fangzheng, HAN Xianglei, WANG Jixiao
    2021, 72(2):  799-813.  doi:10.11949/0438-1157.20200570
    Abstract ( 636 )   HTML ( 13)   PDF (1602KB) ( 298 )  
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    The separation of monovalent and divalent inorganic salts in mixed solution is in great demand in many industrial fields. Nanofiltration is an emerging method for separating monovalent/divalent inorganic salt solutions with potential advantages in economy and operability. In this paper, the main viewpoints of ion transfer mechanism in nanofiltration membrane were introduced, and the impacts of some key issues, such as hydrated ions size, membrane structure, hydrated ion-water-membrane interaction and feed composition, on ions transfer process were analyzed. Next, the methods of high flux NF membrane preparation and high selectivity NF membrane preparation were introduced. After that, the application of nanofiltration in monovalent/divalent inorganic salt solution separation fields, such as resource exploitation, chlor-alkali brine desulfate, wastewater treatment, water softening and heavy metal ion removal were introduced. At last, the problems in the previous works were analyzed, and the development prospects of this field were given.

    Progress on surface-induced nucleation of drug for controlling polymorphism
    LIN Jiawei, SHI Peng, GONG Junbo, WU Songgu
    2021, 72(2):  814-827.  doi:10.11949/0438-1157.20201482
    Abstract ( 361 )   HTML ( 9)   PDF (4647KB) ( 343 )  
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    Surface-induced nucleation refers to utilize the interaction between solute molecule and heterogeneous surface to regulate the nucleation process. It can not only promote the nucleation by reducing the energy requirement during the process of heterogeneous nucleation but also control crystal polymorphism while without changing solvent, temperature and so on. In recent years, surface-induced nucleation has been widely studied in screening and controlling of polymorphism of active pharmaceutical ingredients. The mechanism of heterogeneous surfaces inducing nucleation for controlling polymorphism is reviewed. In addition, four surface substrates used to induce nucleation for controlling crystal polymorphism including polymers, small organic molecular crystals, self-assembled monolayers and gels are reviewed. Besides, four strategies for selection and design of surface substrates are summarized. At last, we introduce the existing problems about surface-induced nucleation of polymorphism and prospect the future development of this research field.

    Research advances of drug-drug co-crystals
    SUN Jingjing, JIA Lina, LIN Bo, WANG Yan, GONG Junbo
    2021, 72(2):  828-840.  doi:10.11949/0438-1157.20201139
    Abstract ( 859 )   HTML ( 17)   PDF (2237KB) ( 583 )  
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    Combination drugs show the potential advantages of reducing drug dosage, toxicity, drug resistance and improving therapeutic effect in clinical treatment. As a new method of combined medicine, drug-drug co-crystals have achieved drug efficiency at the molecular level. It is expected to solve the problems of significant solubility difference, incompatibility and poor stability between drug ingredients. This paper reviews the concept and advantages of drug-drug co-crystals, the formation, dissolution and metabolism mechanisms of drug-drug co-crystals. How to design and predict drug-drug co-crystals from both theoretical and experimental aspects is introduced. Finally, the problems of drug-drug co-crystals that need to be solved are summarized, and the future development direction of drug-drug co-crystals is prospected.

    Preparation of linear low density polyethylenes/polyolefin thermoplastic elastomers by tandem polymerizations
    LI Qiulin, LUO Liqiong, LIU Pingwei, LI Bogeng, WANG Wenjun
    2021, 72(2):  841-851.  doi:10.11949/0438-1157.20201529
    Abstract ( 477 )   HTML ( 15)   PDF (1514KB) ( 217 )  
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    The ethylene/α-olefin copolymers including linear low density polyethylene and polyolefin thermoplastic elastomer can be synthesized by a tandem polymerization with ethylene as only monomer, in the present of a combination of oligomerization and copolymerization catalysts as a tandem catalyst system. However, the development of tandem catalyst systems with high α-olefin selectivity and high copolymerization reactivity at high temperature still remains great challenging. Herein, the progress in the study of ethylene dimerization, trimerization, and tetramerization and polyolefin macromonomer synthesis, and their related tandem polymerizations are reviewed. Majority of tandem polymerizations have been carried out at low temperature. Very few tandem catalyst systems were suitable for polymerization at high temperature. Although ethylene/1-butene and ethylene/1-hexene copolymers could be produced by tandem polymerizations with high α-olefin selectivity in the oligomerization, 1-octene selectivity in the tandem polymerization with ethylene tetramerization should be enhanced. The incorporation of polyolefin macromonomers into polyolefin backbones via tandem polymerization offered alternative approach for developing high-performance polyolefin thermoplastic elastomers with special chain topology.

    Tailoring chain structures of polyesters and their effect on physical and degradation properties
    WANG Songlin, WU Haiqiang, JIANG Bingxue, ZHAO Zhichao, OUYANG Jie, XU Zhiyu, XU Jinlong, LIU Pingwei, WANG Wenjun
    2021, 72(2):  852-862.  doi:10.11949/0438-1157.20201101
    Abstract ( 540 )   HTML ( 7)   PDF (2174KB) ( 403 )  
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    The physical properties and biodegradability of polyester materials are determined by its aggregate structure. The chemical composition, sequence and topological structure of the polymer chain are the most critical factors that determine the polymer aggregate structure. We herein summarize the methods for precisely tailor polyester chains, including block, long chain branch, comb, star, hyperbranch and dendrimer, with the aid of polymerization process control. We also review the relationships between the chain structures and polyester thermal and mechanical properties, and discuss the effect of the chain structures on degradation performances of polyesters. Previous studies have shown that the copolymer block length determines the crystalline structure, the presence of long chain branches contributes to the increase of crystallization temperature and crystallinity of polyester, and the crystallization ability, length, and hydrophobicity of the chains determine the degradation performance of polyester. Meanwhile, we prospect the development of high-performance biodegradable polyesters.

    Research progress of rubber composite with low dynamic heat generation
    WANG Liming, DU Miao, SHAN Guorong, LU Qing, SONG Yihu
    2021, 72(2):  863-875.  doi:10.11949/0438-1157.20201246
    Abstract ( 481 )   HTML ( 6)   PDF (2276KB) ( 207 )  
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    Dynamic heat generation is the direct embodiment of rubber viscoelasticity, which is the transformation from external mechanical energy to thermal energy. The accumulation of heat generated by dynamic heat generation directly affects the performance of materials, as a result, the temperature rise reduces the mechanical strength, static and dynamic modulus and wear resistance of rubber composites. Therefore, research on dynamic heat generation mechanism and low heat generation regulation of rubber composites have been carried out. In this paper, from the perspectives of rubber matrix network structure, enhancing particle dispersion, processing technology and theoretical simulation, the research on low dynamic heat generation of rubber is summarized and analyzed, and the prospect is put forward.

    Progress in clean synthesis technology and application of rubber accelerator NS
    ZHANG Tianyong, YANG Kunlong, CUI Xianbao, LI Bin, SONG Yuxin, JIANG Shuang
    2021, 72(2):  876-885.  doi:10.11949/0438-1157.20200659
    Abstract ( 589 )   HTML ( 15)   PDF (1380KB) ( 449 )  
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    Ulfonamides rubber vulcanization accelerators can be divided into aldehydes, thiurams, thioureas, dithiocarbamates, thiazoles, guanidines, xanthates, and sulfenamides according to their chemical structure. Among them, sulfenamide accelerators have the advantages of long anti-scorch time, high vulcanization activity, high vulcanization flatness, and excellent mechanical properties, and are most widely used. Compared with the other sulfenamide accelerators, accelerator NS (N-tert-butyl-2-benzothiazolesulfenamide, TBBS) does not produce carcinogenic toxic nitrosamines in the process of vulcanization, so it is known as“standard accelerator”. The traditional method for synthesis of accelerator NS with sodium hypochlorite as oxidant is reviewed, and the green synthetic processes such as catalytic oxidation, chlorine oxidation, electrolytic oxidation and hydrogen peroxide oxidation are summarized. A brief overview of the application of the microreactor in the synthesis accelerator NS is provided. At the same time, the applications of accelerator NS in the fields of natural rubber, styrene-butadiene rubber, silica-filled rubber modifier and synthetic phosphoramidate were also introduced.

    Review and outlook on municipal solid waste smart incineration
    YING Yuxuan, LIN Xiaoqing, WU Angjian, LI Xiaodong
    2021, 72(2):  886-900.  doi:10.11949/0438-1157.20200733
    Abstract ( 596 )   HTML ( 17)   PDF (1407KB) ( 221 )  
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    Based on the advantages and disadvantages of technologies that applied in incineration disposal, including internet of things, incineration status diagnosis, online real-time monitoring of pollutants, as well as artificial intelligence algorithms, this paper reviews the domestic and foreign research status on intelligent monitoring, automatic control, and management of processes composed by municipal waste collection, transportation and storage, incineration disposal, and pollutant emission control. Furthermore, the future development of intelligent incineration technology has been prospected. We suggest to carry out systematic integration and coupling of the existing subsystems and modules, build transient closed-loop feedback and optimization model through big data analysis and cloud computing platform, and further develop intelligent incineration technologies and equipment.

    Review on the bioleaching of spent refinery catalysts for metals removal
    WANG Yuejie, LI Lingling, HE Chunhong
    2021, 72(2):  901-912.  doi:10.11949/0438-1157.20201106
    Abstract ( 340 )   HTML ( 4)   PDF (1945KB) ( 149 )  
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    The green and low energy consumption bioleaching technology of spent refinery catalysts has been widely concerned. This article reviews the related research from the perspectives of metal contents and characteristics of spent refinery catalysts, bioleaching microorganisms, leaching efficiency of metals, influencing factors and bioleaching kinetics. The research status and development prospects are brief analyzed. Acidithiobacillus, Aspergillus niger, and Penecillum simplicissimum are the most common strains used in bioleching of spent refinery catalysts. Under the action of bioleaching, the leaching efficiency of metals from spent hydrogenation catalysts are very high, and metals from spent fluid catalytic cracking (FCC) catalysts are more difficult to leaching. Temperature, pulp density and particle size of spent catalysts are the main factors affecting the bioleaching process of spent catalysts. Chemical reaction kinetics and membrane diffusion kinetics are widely used kinetic models in the research of bioleaching of spent refinery catalysts. At present, the research on the treatment of spent refinery catalysts by bioleaching still in the laboratory research stage, and relevant research on small-scale, pilot-scale or industrial applications has not been carried out.

    Thermodynamics
    Calculating adsorption isotherm of gas mixture at solid interface using molecular thermodynamic model of two-dimensional fluid
    CHEN Boya, LI Mingyan, ZHU Yuhang, PENG Changjun, LIU Honglai
    2021, 72(2):  913-920.  doi:10.11949/0438-1157.20200598
    Abstract ( 389 )   HTML ( 11)   PDF (1120KB) ( 120 )  
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    Coupled with mixing rule, the molecular thermodynamic model for two-dimensional square-well chain fluid with variable range (SWCF-VR-2D) was extended to mixture. The model was applied to calculate the adsorption isotherms for gas mixtures such as methane-carbon dioxide, methane-nitrogen and methane-ethane on different adsorbents. Because of the interaction between mixed gases, the adsorption of mixed gases is different from the pure gases. This change is described by adjusting the interaction parameter εw between the gas and the solid surface. After adjusting the energy parameters, the model can satisfactorily calculate the adsorption isotherm of the mixed gas, and the total average deviation is 5.06%.

    Fluid dynamics and transport phenomena
    Investigation of secondary flow in helical coils based on residence time distribution
    HUANG Zhengliang, WANG Chao, GUO Yanni, YANG Yao, SUN Jingyuan, WANG Jingdai, YANG Yongrong
    2021, 72(2):  921-927.  doi:10.11949/0438-1157.20200640
    Abstract ( 375 )   HTML ( 7)   PDF (1050KB) ( 225 )  
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    The existence of secondary flow in the helical coil can significantly enhance the mass and heat transfer performance. In this work, based on the residence time distribution of the liquid, the dimensionless variance (σ2) was obtained to characterize the strength of the secondary flow in helical coils. Furthermore,the influence of structural parameters such as the coiling diameter, tube diameter and coiling angle, on the secondary flow in the helical coil was also revealed by this method. The results showed that when the migration distance of radial flow had not reached its limitation in helical coils, σ2 decreased first and then increased with the increase of Reynolds number (Re) of the liquid, corresponding to theturbulent flow action zone and secondary flow action zone. While the migration distance of radial flow had reached its limitation, σ2 decreased first, then increased and finally changed to be steady with the increase of Re of the liquid, corresponding to the turbulent flow action zone, secondary flow action zone and secondary flow limit zone. The critical Reynolds number ReS that changes from the turbulent area to the secondary flow area decreases with the decrease of the winding diameter and pipe diameter of the winding pipe, and the winding angle has little effect on ReS.

    Formation and size prediction of bubble in slurry system in T-junction microchannel
    CHEN Zhen, LIU Jing, ZHU Chunying, FU Taotao, MA Youguang
    2021, 72(2):  928-936.  doi:10.11949/0438-1157.20201081
    Abstract ( 370 )   HTML ( 9)   PDF (1731KB) ( 139 )  
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    The formation process and size of bubbles in the slurry in the T-shaped microchannels were experimentally studied. The slurries with different polystyrene microsphere concentrations and nitrogen were used as the continuous phase and the dispersed phase in the experiment. The bubble formation process could be divided into three stages: expansion, squeezing and pinch-off stages. With the increase of slurry concentration, the duration of expansion stage is hardly various, the squeezing stage shortens obviously, while the pinch-off stage shortens slightly. The neck width of bubble presents power ratio relationship with dimensionless remaining time in the expansion and pinch-off stages, but linear in squeezing stage. The influences of slurry concentration, gas and liquid flow rates on bubble size were investigated. The results show that the bubble size increases with the increase of gas flow rate and decreases with the increase of liquid flow rate and slurry concentration.

    One-dimensional amplification and gas-liquid mass transfer characteristics of microchannel reactor
    WANG Guanqiu, LIN Guanyi, ZHU Chunying, FU Taotao, MA Youguang
    2021, 72(2):  937-944.  doi:10.11949/0438-1157.20201064
    Abstract ( 516 )   HTML ( 8)   PDF (1217KB) ( 169 )  
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    The microchannel reactor can effectively enhance the mass transfer between gas and liquid, but its processing capacity is limited. To increase the productivity of the microchannel, one-dimensional amplification and the gas-liquid mass transfer characteristics of the microchannel reactor were investigated. By using CO2 absorption into monoethanolamine (MEA) and methyldiethanolamine (MDEA) mixed aqueous solution as the working system, the effects of microchannel width and gas-liquid flow rate on mass transfer characteristics were studied under a constant channel depth. The results show that both the mass transfer coefficient and volumetric mass transfer coefficient increase firstly and then slightly decrease with increasing channel width, and the maximum values are attained in 400 μm × 1000 μm channel. The specific surface area decreases with the increase of channel width. Therefore, a reasonable increase in the width of the microchannel can improve the processing capacity while still maintaining good mass transfer characteristics.

    Investigation on heat transfer characteristics of subcritical and supercritical water in an inclined rifled tube
    ZHANG Xin, LIU Zhaohui, BI Qincheng, LYU Haicai, YANG Dong
    2021, 72(2):  945-955.  doi:10.11949/0438-1157.20201028
    Abstract ( 335 )   HTML ( 2)   PDF (2721KB) ( 107 )  
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    To explore the heat transfer characteristics of rifled tube water wall in the supercritical (ultra-supercritical) boiler,an experiment was carried out in a ?35 mm×7.75 mm upwards inclined rifled tube at different inclination angles from 5° to 90°. The experimental parameters are as follows: pressures from 15 to 28 MPa, mass flow rate from 600 to 1000 kg?m-2?s-1, heat flux from 300 to 500 kW?m-2. The wall temperature characteristics were compared between the rifled tube and the ?25 mm×3 mm smooth tube. The effects of inclination angles, mass flow rate and pressures on the heat transfer characteristics of subcritical, near-critical and supercritical water in the rifled tube were discussed. The heat transfer correlations of supercritical water in the rifled tube at different inclination angles were developed. The results revealed that the rifled tube used in the experiment had the property of delaying heat transfer deterioration and enhancing heat transfer. The heat transfer characteristics of the rifled tube at different inclination angles were different. The mass flow rate had little influence on the heat transfer coefficients in the two-phase region at subcritical pressure. And with the increase of mass flow rate, the heat transfer coefficients increased at near-critical and supercritical pressure. The heat transfer coefficients at 15 MPa were higher than those at other pressures.Under supercritical pressure, as the pressure increases, the heat transfer coefficient of the large specific heat zone decreases.

    Simulation on heat transfer and thermal storage processes of foamed metal composite PCM microstructure
    XU Xianggui, WANG Liqiong, WANG Junlei, WANG Yan, HUANG Qiao, HUANG Yun
    2021, 72(2):  956-964.  doi:10.11949/0438-1157.20201128
    Abstract ( 496 )   HTML ( 8)   PDF (2663KB) ( 244 )  
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    Paraffin wax is used as the phase change material (PCM), and the three-dimensional structure model of six-sided round holes is used to numerically simulate the phase change melting process of the foam metal composite PCM. The effects of different metal foam materials (Cu, Al, Ni, Fe), pore density and porosity on the heat transfer and heat storage performance of composite PCM were studied by monitoring the liquid phase fraction and total heat storage during the phase change interface evolution. The results show that the heat transfer process of foamed metal composite PCM is affected by heat conduction and natural convection. The complete melting time of composite PCM can be shortened and heat transfer can be accelerated by increasing pore density, but the shortening range decreases with the increase of pore density and the higher the thermal conductivity of the foam metal, the greater the influence of pore density on the heat transfer rate. Thermal non-equilibrium phenomenon exists in the foamed metal composite PCM, and the increase of pore density and porosity can both reduce the maximum average temperature difference, but the effect on the final equilibrium time is quite different. Increasing pore density can shorten the final equilibrium time, while increasing porosity will prolong the final equilibrium time. In addition, the heat storage density per unit mass of foam metal composite PCM increases with the increase of porosity. Compared with foam Cu, Ni and Fe composite PCM, foam Al composite PCM has a higher heat storage density per unit mass and a higher rate.

    A computational mass transfer model for the simulation of biodegradation process of phenol waste water in an internal loop airlift reactor
    ZHANG Chao, LIU Youzhi, JIAO Weizhou, ZHANG Qiaoling
    2021, 72(2):  965-974.  doi:10.11949/0438-1157.20200716
    Abstract ( 331 )   HTML ( 7)   PDF (3693KB) ( 114 )  
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    In this paper, the process of biodegradation of phenol wastewater in the internal loop airlift reactor (ILALR) was studied using computational mass transfer method. The Euler approach is carried out with RNG k-ε method to predict the hydrodynamics of the reactor. The population balance model is adopted to describe the bubble size distribution. The recently developed computational mass transfer c2ˉ-εc model is used to close the turbulent mass transfer differential equations, so the turbulent mass diffusivity can be determined without using empirical methods. The simulated results of dissolved phenol concentration and cell concentration are compared to the experimental data in the literature, and good agreement is observed. The simulated results reveal that the distribution of the calculated turbulent Schmidt number is not a constant in the ILALR, so the traditional method of assuming a constant turbulent Schmidt number by experience is not reasonable. Moreover, the simulated shear stress in the ILALR is increased with the increase of the superficial gas velocity, and the highest shear stress is found in the top region of the draft tube.

    Catalysis, kinetics and reactors
    Strategy for numerical optimization of safe and efficient operation of semi-batch reactors
    LU Qiushi, YE Guanghua, ZHOU Xinggui
    2021, 72(2):  975-983.  doi:10.11949/0438-1157.20201381
    Abstract ( 484 )   HTML ( 15)   PDF (1975KB) ( 159 )  
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    When the materials in the semi-batch tank reactor accumulate too much and the reaction exotherms too quickly, it is easy to cause the risk of thermal runaway and cause chemical safety accidents. A preferable feeding operation can avoid the risk of thermal runaway, shorten operation cycle, and improve production efficiency. In this work, a strategy for numerical optimization of the safe and efficient feeding operation is proposed, based on a mathematical model of semi-batch reactors and with hydrolysis of acetic anhydride as the model reaction. In this strategy, the range for safe feeding temperature is firstly determined under different feeding modes (e.g., one-stage, two-stage and three-stage), and then the specific feeding temperature corresponding to the shortest operating cycle is found within this temperature range. This feeding temperature is optimal. The results show that the range for safe feeding temperature and the optimal operating temperature for the three-stage feeding mode are 60.9% wider and 1.9 K lower than these of the one-stage feeding. The six-stage feeding mode can almost achieve the minimum operating cycle, and increasing the operating pressure can also shorten the operating cycle.

    Kinetics of red base KD diazotization in microreactor system
    WANG Fajun, HUANG Jinpei, XU Jianhong
    2021, 72(2):  984-992.  doi:10.11949/0438-1157.20200741
    Abstract ( 500 )   HTML ( 7)   PDF (1392KB) ( 337 )  
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    Diazotization reaction is a traditional method for synthesizing diazonium salt intermediates. Because of their huge synthesis potential, diazonium salt intermediates are widely used in fine chemical fields such as medicine, pesticides, dyeing and pigment industries. Firstly, the quantitative method of diazonium salt intermediates was established by the azo-coupling reaction and UV-visible spectrophotometry. Precision experiments and reproducibility experiments were performed for this measurement method. The results showed that the accuracy and reproducibility of the method were good, and the relative standard error was less than 1%, indicating that the method could be used in the quantitative study of diazonium salts. Then, a microreactor system for the determination of kinetic parameters of the diazotization reaction was established. Compared with the traditional batch reactor method, this method could strictly control the reaction conditions, such as reaction time and reaction temperature. Finally, under the condition of low red base KD concentration and far excess hydrochloric acid concentration, the reaction was determined to be a secondary reaction, and the pre-exponential factor of the reaction was 1.57×1014 L/(mol·s), and the activation energy was 72.88 kJ/mol. The reaction kinetics model was established within the experimental research scope, and the verification experiments showed that the simulation results were in good agreement with the experimental results.

    Impacts of calcination atmosphere and pore structure on performance of hydrodemetallization catalysts
    SUI Baokuan, SHI Yao, LIN Jianyang, LIU Wenjie, YUAN Shenghua, GENG Xinguo, DUAN Xuezhi
    2021, 72(2):  993-1000.  doi:10.11949/0438-1157.20200658
    Abstract ( 469 )   HTML ( 7)   PDF (1872KB) ( 174 )  
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    Three kinds of Mo-Ni hydrodemetallization (HDM) catalysts are prepared by an incipient wetness impregnation method with the varied calcination atmosphere, i.e., air, nitrogen and water-steam, then their hydrogenation performances for residual oil are evaluated. It is found that these calcination atmospheres have a little impact on the activity of the hydrodemetalization reaction, while the catalyst roasted in the air atmosphere shows relatively high hydrodesulfurization and carbon residue removal activity. The impacts of the pore structures of alumina on the hydrodemetallization activity are further investigated by combining experiments and numerical simulations. The results show that the most probable pore size of 22 nm is favorable for the hydrodemetallization, because of the facilitated reaction-diffusion balance.

    Study on reaction characteristics of solution polymerization system for butyl rubber preparation in microreactor
    HE Yuhang, LIU Qingjie, LYU Yangcheng
    2021, 72(2):  1001-1008.  doi:10.11949/0438-1157.20200999
    Abstract ( 375 )   HTML ( 2)   PDF (1397KB) ( 200 )  
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    Reaction characteristics of solution polymerization system for butyl rubber preparation in microreactor has been studied. Results showed that polyisobutylene with Mn over 300000 can be quantitatively obtained in minutes when using H2O as proton source, EtAlCl2 as co-initiator, and keeping reaction temperature at -60℃, water concentration between 0 (control) and 0.27 mmol/L. Chain transfer was efficiently suppressed under this condition. Enhancing the initial mixing of reactants was good for improving product quality. Incorporating isoprene in the system will significantly decrease molecular weight of final products and reaction rate. Replacing EtAlCl2 with less acidic Et2AlCl can stabilize carbocation and inhibit chain transfer. Copolymer with Mn near 150000 can be obtained at -60℃, but the reaction rate was moderate and need further optimization of system water concentration to enhance this process.

    Thermodynamic analysis and kinetic simulation of liquid phase oxidation of prehnitene to mellophanic acid
    LYU Quanming, SUN Weizhen, ZHAO Ling
    2021, 72(2):  1009-1017.  doi:10.11949/0438-1157.20201038
    Abstract ( 480 )   HTML ( 7)   PDF (1612KB) ( 216 )  
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    The liquid phase oxidation of prehnitene (PR) to mellophanic acid (MPA) is a key step in the synthesis process of polyimide monomers. In this work, thermal properties of PR liquid phase oxidation were calculated, in which the thermodynamic parameters of MPA were estimated by group contribution methods. The results show that this reaction is a strong exothermic reaction within the studied temperature range, thus the reaction heat should be carefully controlled during the reaction process. Then the optimal reaction conditions were determined by batch experiments in the ranges of 200—240℃, and a lumped kinetics model under different temperatures, catalyst concentrations and ratios were established. It is found that the catalyst ratio of Co/Mn/Br has a great influence on the generation rate of MPA, while little on the oxidation rate of PR. Particularly, the increase of Mn content has the best effect on the increase of MPA generation rate. Simultaneously, the increase of temperature can significantly accelerate the rate of PR oxidation with an activation energy of 57.20 kJ·mol-1. However, the activation energy of other methyl groups increased to 120.30 kJ·mol-1 when part of methyl groups on the benzene ring were oxidized to carboxyl groups, indicating that the existence of carboxyl groups can weaken the activity of methyl groups and increase the difficulty of further oxidation. The related research results of the thesis can provide references for the development of new MPA production processes and the design of industrial reactors.

    Study on catalytic degradation of PCDD/Fs over Mn-Ce-Co-Ox/PPS catalytic filter
    LIU Honglei, PENG Yaqi, TAO Junyi, TANG Minghui, LU Shengyong
    2021, 72(2):  1018-1025.  doi:10.11949/0438-1157.20201294
    Abstract ( 406 )   HTML ( 4)   PDF (1809KB) ( 104 )  
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    To decompose PCDD/Fs(polychlorinated dibenzo-p-dioxins and dibenzofurans) in flue gas, Mn-Ce-Co-Ox/PPS catalytic filter was prepared by in-situ oxidation method. The effect of catalyst loading on catalytic degradation of furan by Mn-Ce-Co-Ox/PPS catalytic filter was investigated. Furthermore, effect of operating temperature in the range of 140—200℃ on catalytic degradation of PCDD/Fs by Mn-Ce-Co-Ox/PPS catalytic filter was studied. Several physicochemical methods, including SEM(scanning electron microscope), EDS(energy dispersive spectroscopy) and XRD(X-ray diffraction) were employed to characterize the structure and properties of the composite catalytic filter. With the increase of catalyst loading from 81.8 g/m2 to 154.2 g/m2, degradation efficiency of furan by Mn-Ce-Co-Ox/PPS kept increasing, and the monolayer saturated loading of Mn-Ce-Co-Ox/PPS was 120.5 g/m2. Mn-Ce-Co-Ox/PPS catalytic filter can remove more than 90% of PCDD/Fs at 140—200℃. Degradation efficiencies of PCDD/Fs over Mn-Ce-Co-Ox/PPS showed a rapid growth with the increase of reaction temperature, achieving the highest of 78.01% at 200℃. The degradation efficiency of 17 dioxin homologs was analyzed, and it was found that the degradation rate of Mn-Ce-Co-Ox /PPS to low-chlorinated dioxin homologs was higher than that of high-chlorinated homologs.

    Separation engineering
    Metal ions mediated amine-based post-combustion CO2 capture
    TAN Fangyuan, LI Kangkang, YU Hai, JIANG Kaiqi, HAN Yueheng, WANG Xiaolong, ZHAI Rongrong, LI Yulong, CHEN Jian
    2021, 72(2):  1026-1035.  doi:10.11949/0438-1157.20201024
    Abstract ( 495 )   HTML ( 16)   PDF (3415KB) ( 254 )  
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    To solve the problem of too high energy consumption for the regeneration of carbon dioxide after the combustion of alcohol amine method, a method of adding metal ions to the amine solution to reduce the energy consumption of CO2 desorption was studied, and it is called the metal ion complex thermal buffer self-heating utilization technology. Using the benchmark mono-ethanolamine (MEA) absorbent, we investigated two metal-ion additives [Cu(Ⅱ) and Ni(Ⅱ)] and revealed the mechanism of metal-ion mediated amine regeneration through the development and analysis of a chemical model of MEA-Me(Ⅱ)-CO2-H2O. It is revealed that in such system the metal-amine complexes act as chemical energy buffer to store the CO2 absorption enthalpy and liberate it for CO2 desorption, thus reducing the regeneration energy requirement. Comprehensive experiments of metal-ion mediated CO2 capture process were performed to characterize the performance of CO2 absorption and desorption, including heat of CO2 reaction, CO2 desorption rate, cyclic CO2 loading, vapor-liquid equilibrium. The results showed that adding Cu(Ⅱ) or Ni(Ⅱ) into MEA increased the absorbent's cyclic CO2 loading by 14%—20% or 7%—10%, leading to a reduction of CO2 reaction heatby 6.6%—24% in Cu(Ⅱ)/MEA system and 6.0%—20% in Ni(Ⅱ)/MEA system.

    Simulation and analysis of rapid pressure swing adsorption for hydrogen production
    NIU Zhaoyang, JIANG Nan, SHEN Yuanhui, WU Tongbo, LIU Bing, ZHANG Donghui
    2021, 72(2):  1036-1046.  doi:10.11949/0438-1157.20201393
    Abstract ( 909 )   HTML ( 36)   PDF (2820KB) ( 350 )  
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    At present, pressure swing adsorption is the main technology to produce hydrogen product gas from steam methane reformed gas in the industry. However, the rapid increase in energy demand makes the shortcomings of traditional pressure swing adsorption technology more obvious in terms of productivity. For this reason, a simulation study of hydrogen production from steam methane reformed gas by rapid pressure swing adsorption was carried out. The activated carbon and 5A zeolite were used as adsorbents and the numerical simulation and analysis of six bed rapid pressure swing adsorption process were carried out based on the measured adsorption data of each component in the feed gas on the two adsorbents. After analyzing the temperature, pressure and gas and solid concentration distribution in the bed, the three operating parameters of the feed flow rate, the height ratio of the two-layer adsorbent and purge-to-feed ratio have been investigated for the effect of the rapid pressure swing adsorption process performance. When the feed gas composition is H2/CH4/CO/CO2=76%/3.5%/0.5%/20%, the adsorption pressure is 22 bar, the pressure of purge desorption is 1.0 bar, the feed flow rate is 0.8875 mol·s-1, the adsorbent bed height ratio is 0.5∶0.5, and purge-to-feed ratio is 22.37%, the purity of H2 is 99.90% and the recovery is 69.88%. At this time, the yield of H2 is 0.4713 mol·s-1. In contrast, although the H2 recovery of the PSA process is 83.40%, the processing capacity is only 0.39 mol·s-1, so the productivity is only 0.2472 mol·s-1 when the purity is 99.90%.

    Process system engineering
    Optimal design of heat integrated water allocation networks combining mathematical programming with graphical tools
    PENG Xiaoyi, DONG Xuan, LIAO Zuwei, YANG Yao, SUN Jingyuan, JIANG Binbo, WANG Jingdai, YANG Yongrong
    2021, 72(2):  1047-1058.  doi:10.11949/0438-1157.20200559
    Abstract ( 398 )   HTML ( 9)   PDF (3012KB) ( 98 )  
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    The mathematical programming method and the graphic method are combined to explore the heat integrated water allocation networks. First, a mixed integer non-linear programming model (MINLP) was constructed to optimize the combined curve area of the separation system in the case of unknown stream parameters under minimum utility consumption, and the most energy-efficient water network structure with the minimum heat exchange area was obtained. Then, design heuristics are proposed for the composite curve of the new separation system. The heat exchanger network structure with a small number of heat exchange units can be obtained. The calculation example shows that compared with the existing design method of heat integrated water network based on separation system, it can further reduce the number of heat exchangers and the total heat exchange area while minimizing the amount of public works.

    Online adaptive wavelength selection method and its application in gasoline blending process
    WANG Kai, DU Wenli, LONG Jian
    2021, 72(2):  1059-1066.  doi:10.11949/0438-1157.20201300
    Abstract ( 483 )   HTML ( 5)   PDF (1331KB) ( 99 )  
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    The near-infrared spectroscopy analysis technology has been widely used in industry as a non-invasive analysis method. However, most of the wavelength selection methods of NIR models are established offline, which cannot effectively track the change of process characteristics. In this paper, a new online adaptive wavelength selection method, online adaptive interval Gaussian process regression (AIGPR), is proposed and applied in gasoline blending process. The proposed method can adjust the wavelength structure according to the characteristics of the query samples. In order to reduce the computing cost of online applications, the proposed method is divided into two parts: offline and online. In the offline part, the spectrum is divided into several wavelength intervals, and a local model is established in each wavelength interval to prepare for online application; in the online part, the query samples are segmented according to the division rules and used to calculate the wavelength importance index by the corresponding local model to obtain the optimal wavelength interval. The effectiveness of the method is proved on the gasoline data. Compared with the variable importance in the projection (VIP) method and the improved relation-variance(RV) method, AIGPR has better performance.

    Surface and interface engineering
    Study on anticorrosive properties of epoxy soybean oil resin coating
    HE Jizhe, LIU Mingyan, XU Yangshuhan
    2021, 72(2):  1067-1077.  doi:10.11949/0438-1157.20200842
    Abstract ( 566 )   HTML ( 24)   PDF (5373KB) ( 186 )  
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    Using epoxy soybean oil (ESO) as the main raw material and tetraethylenepentamine as the curing agent, epoxy soybean oil resin (ESOR) coatings were prepared on the surface of carbon steel. Field emission scanning electron microscope, Fourier infrared change spectrometer, nano-indenter, thermogravimetric analyzer, contact angle measuring instrument, electrochemical impedance spectroscopy and other techniques were used to characterize the performance of the ESOR coatings. It was found that the content of ESO in the raw materials helps to improve the water resistance of the ESOR coating. When the content of ESO in the raw material gradually increases, the hardness, elastic modulus and corrosion resistance of the ESOR coating will also increase. According to the fitted equivalent circuit, the coating resistance Rc of ESOR coating with a molar ratio of epoxy soybean oil to tetraethylenepentamine equal to 2 can reach 8.22×1011 Ω·cm2, and the charge transfer resistance Rct can reach 1.32×1010 Ω·cm2, which shows excellent anti-corrosion performance.

    Energy and environmental engineering
    Heterogeneous modeling and internal mass transfer mechanism of lithium-ion batteries: effect of particle size distribution
    CHEN Yiqin, XU Yu, ZHOU Jinghong, SUI Zhijun, ZHOU Xinggui
    2021, 72(2):  1078-1088.  doi:10.11949/0438-1157.20201095
    Abstract ( 722 )   HTML ( 20)   PDF (3856KB) ( 389 )  
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    Lithium-ion batteries, as a kind of energy storage device with high energy density and long service life, have been widely applied in many fields. As the actual energy densities of cathode materials approach their theoretical values, the optimization of assembling parameters has become a crucial way to improve the performance of lithium-ion batteries. And the particle size distribution of the electrode particles is a very important parameter. In this work, heterogeneous models were used to construct geometry of electrode with single-sized particles and bimodal-sized LiFePO4 (LFP) particles. Then the corresponding discharge processes of C-LFP system were quantitatively simulated by Newman model to investigate the impact of particle size distribution on the performance of lithium-ion batteries. The simulation results show that the reduction of the particle size reduced the influence of solid phase diffusion coefficient on battery performance, but increased the liquid phase diffusion resistance. Proper particle size distribution of active material could promote the diffusion of lithium ion in electrolyte and increase the lithium insertion amount inside the small particles, but cause heavier polarization, thus decreasing the lithium insertion amount inside the large particles. The wider distribution of the particles and the larger overall particle size, the smaller the energy density of the lithium ion battery. Choosing an appropriate active particle size with proper distribution can effectively enhance the energy density of lithium-ion batteries. The research results provide useful basic knowledge and guidance for the selection of particle size distribution of electrode active materials for lithium-ion batteries.

    Parameter analysis and optimization of power and heat cogeneration system with biomass fueled SOFC and engine
    ZHU Pengfei, GUO Leilei, YAO Jing, YANG Fusheng, ZHANG Zaoxiao, WU Zhen
    2021, 72(2):  1089-1099.  doi:10.11949/0438-1157.20201016
    Abstract ( 591 )   HTML ( 17)   PDF (2605KB) ( 209 )  
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    In response to the need for clean and efficient energy conversion technology, a new hybrid power generation system using biomass as fuel is proposed. The system consists of a biomass gasification device, a solid oxide fuel cell, an engine and a waste heat recovery subsystem. The thermodynamic modeling of the system was established by Aspen Plus. Based on the modeling results, parametric analysis was conducted to investigate the influence of key parameters on the performance of the system. Besides, bi-objective optimization was conducted to maximize the exergy efficiency and simultaneously to minimize the specific electric energy cost via the Epsilon-constraint approach. The results showed that the net electrical efficiency of the system increases from 47.3% to 50.3% with the increase of the steam to biomass ratio and also increases from 45.5% to 48.2% with the increase of fuel utilization factor. The efficiency of power generation tends to decrease with the increase of biomass and air equivalent ratio. It was found, at the Pareto optimum solution, the hybrid power generation system can achieve an optimal exergy efficiency of 53.5% and specific electric energy cost of 0.0576 USD/(kW·h). The specific electrical energy cost is comparable to the energy cost (0.0546 USD/(kW·h)) of the standard power plant and is 19.6% lower than the natural gas-fueled SOFC-Engine system, indicating that the proposed biomass fueled hybrid system is a kind of clean, efficient and economical energy conversion technology.

    Study on reaction force field simulation of pyrolysis interaction among components of oily sludge
    WEN Yanjun, JIANG Chi, LI Wenxuan, XIE Yingshen, WANG Gang, HOU Yingfei
    2021, 72(2):  1100-1106.  doi:10.11949/0438-1157.20201206
    Abstract ( 388 )   HTML ( 9)   PDF (1619KB) ( 137 )  
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    The composition of petroleum hydrocarbons in oily sludge is complex, and it is difficult to reveal the interaction between components in the pyrolysis process only by the macroscopic analysis results of products. Five compounds, namely n-dodecane, 1-dodecene, methylcyclohexane, p-xylene, and 1-methylnaphthalene, were represented as alkanes, alkenes, cyclanes, monocyclic aromatics and polycyclic aromatic hydrocarbons in oily sludge to construct model compounds of petroleum hydrocarbon in oily sludge. The molecular dynamics simulation method based on reaction field was used to study the distribution of products and the interactions among components during pyrolysis. The results showed that the pyrolysis products of model compounds were dominated by small molecular compounds H2 and C1—3, C2H4 and C3H6 in the early pyrolysis phase, and C2H2, C3H4 and H2 in the late pyrolysis phase. Compared with the separate pyrolysis of each component in the model compound, the consumption rate of each component in the mixed pyrolysis process of petroleum hydrocarbon is obviously accelerated, and the number of pyrolysis product fragments also increases to a certain extent. According to the first-order reaction kinetic model, the apparent activation energy of petroleum hydrocarbon components in the mixed pyrolysis process decreased to different degrees, among which the apparent activation energy of alkanes, alkenes, and cycloalkanes decreased by 16.493 kJ/mol, 50.571 kJ/mol and 146.289 kJ/mol, respectively, which proved the synergistic effect of pyrolysis among petroleum hydrocarbon components of oily sludge from the level of molecular simulation.

    Properties analysis of dry-process calcium carbide slag and study on acetylene gas escape behavior
    MU Xiujuan, ZHU Ganyu, YAN Kun, ZHAO Liwen, LI Shaopeng, LI Huiquan, SUN Guoxin
    2021, 72(2):  1107-1115.  doi:10.11949/0438-1157.20201263
    Abstract ( 605 )   HTML ( 17)   PDF (2557KB) ( 583 )  
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    Dry-process calcium carbide slag is a large amount of calcium-based solid waste produced in the process of making acetylene by the calcium carbide process, in which residual calcium carbide and acetylene gas have a greater impact on resource utilization. Focusing on the hidden safety problem caused by the acetylene gathering, the physical and chemical properties of dry calcium carbide slag were analyzed. The changes of residual calcium carbide content and the influences of different temperature, humidity, vibration, open time, gas replacement and other factors on the escape behavior of acetylene gas were investigated. The results show that the main component of calcium carbide slag is calcium hydroxide, and the particle size is concentrated below 75 μm. The morphology of the slag is polyhedral and loose sheet-like. The residual amount of calcium carbide in the slag fluctuates from 0 to 0.71%. The increase of temperature and moisture can promote the escape of acetylene gas from calcium carbide slag. Vibration has no obvious promotion or suppression effect, moreover, most acetylene can escape from calcium carbide slag with the combination of hanging and air replacement. Through this method, the explosion risk caused by the gathering of acetylene gas can be effectively reduced. The research can provide a reference for the storage, transportation and utilization of calcium carbide slag in the industrial production process.

    Performances and kinetics analyses of co-combustion of alcohol extracted herb residue and wasted activated coke
    ZHU Xinyu, ZHANG Guangyi, ZHANG Jianwei, WEN Hongyan, LI Yunjia, ZHANG Jianling, XU Guangwen
    2021, 72(2):  1116-1124.  doi:10.11949/0438-1157.20201333
    Abstract ( 370 )   HTML ( 3)   PDF (1573KB) ( 110 )  
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    The combustion characteristics of alcohol extracted herb residue, wasted activated cokes and their mixtures with different proportions at different heating rates were studied by thermogravimetric analysis, and the combustion kinetic parameters were calculated by The Coats-Redfern method. The results showed that the combustion of alcohol extracted herb residues was a continuous process of volatiles and a small amount of fixed carbon, while that of wasted activated cokes was mainly a process of fixed carbon combustion. The alcohol extracted herb residues had better combustion characteristics and lower average activation energy than wasted activated coke. TG-MS analyzer was used to compare the flue gases produced from the combustions of alcohol extracted herb residues and its mixture. The results show that the addition of waste activated coke has a significant adsorption and reduction effect on the NOx produced during the combustion of alcohol-extracted herb residue. The kinetic analyses showed that the activation energy of the mixture of alcohol extracted herb residues and wasted activated cokes decreased with the increasing addition amount of alcohol extracted herb residues compared to pure wasted activated cokes, which improved the reaction activities of wasted activated cokes to boost their combustion. The use of thermogravimetric analysis to predict the combustion properties of mixed fuels is reliable, and has a guiding role in the development of technology for co-combustion treatment of alcohol-extracted herb residues and waste activated coke.

    Effect of X-ray diffraction analysis of polyvinylpyrrolidone on decomposition process of hydrate
    TANG Cuiping, ZHOU Xuebing, LIANG Deqing
    2021, 72(2):  1125-1131.  doi:10.11949/0438-1157.20201062
    Abstract ( 305 )   HTML ( 5)   PDF (1449KB) ( 124 )  
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    With the exploration and development of deepwater oil and gas resources and the environmental protection requirements, the use of gas hydrate kinetic inhibitors is inevitable. So the study of gas hydrate decomposition containing kinetic inhibitors has important guiding significance for the plug removal after hydrate formation. In this paper, a mixture of methane and propane is used in the high-pressure reactor to form natural gas hydrate, and the hydrate decomposition process containing kinetic inhibitor polyvinglpyrrolidone is analyzed by X-ray powder crystal diffractometer. The results showed that methane and propane can form SⅡ gas hydrates, but there still exists some SⅠ methane hydrates. After the addition of kinetic inhibitors, the decomposition rate of hydrate slowed down. At -60℃, in the first 20 min, 69% hydrate decomposed in the non-inhibitor system, about 18% in the system with 0.5% polyvinylpyrrolidone. During dissociation process of CH4-C3H8 SⅡ hydrates, crystal planes decomposition rate of hydrate cell is the same and there is no preferential rate of dissociation of either planes with or without polyvinylpyrrolidone, which implies that the unit cell decomposes as a single entity. Kinetic inhibitor polyvinylpyrrolidone cannot change this decomposition way.

    Study on deposition and decomposition characteristics of ammonium bisulfate/ammonium sulfate as by-product of denitration in coal-fired flue gas
    QING Mengxia, ZHANG Xin, LIU Liang, ZHANG Wei, WANG Lele, SU Sheng, KONG Fanhai, XIANG Jun
    2021, 72(2):  1132-1141.  doi:10.11949/0438-1157.20200972
    Abstract ( 836 )   HTML ( 15)   PDF (4388KB) ( 197 )  
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    A special multi-stage temperature control experimental bench for simulated air preheater was built, and the generation, deposition and decomposition of ammonium bisulfate (ABS) and ammonium sulfate (AS) under different SO3 concentrations, SO3/NH3 ratio, and different temperature conditions were studied. At the initial deposition site under high temperature conditions, the deposits are all liquid ABS, and its weight loss characteristics are basically the same as pure ABS. However, under lower temperature ranges, the characteristics of the sediments will change with SO3/NH3. When SO3/NH3 is 2∶1, the sediments are the mixture of H2O, H2SO4 and a small amount of ABS, which exists in the form of dense droplets, and it has multi-stage decomposition characteristics. When SO3/NH3 is 1∶1 and 1∶2, the sediments are the dry AS power with strong dispersion, and its decomposition characteristics are basically the same as pure AS. The results can provide guidance for ABS prevention and control.

    Material science and engineering, nanotechnology
    Application of CdSe@ZnS quantum dot fluorescence sensor in detection of copper ion pollution in water
    ZHAO Xinyu, GENG Yuhao, TIAN Zhenhao, XU Jianhong
    2021, 72(2):  1142-1148.  doi:10.11949/0438-1157.20200324
    Abstract ( 500 )   HTML ( 9)   PDF (3213KB) ( 125 )  
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    CdSe@ZnS core-shell quantum dots were continuously synthesized by using microfluidic technology. The surface of quantum dots was modified with mercaptopropionic acid to prepare water-soluble CdSe@ZnS core-shell quantum dots that can be quenched by copper ions. Subsequently, polyvinyl alcohol (PVA) hydrogel is used as a skeleton, and the modified quantum dots are loaded on the skeleton through hydrogen bonding force to obtain a composite fluorescent sensor device with simple preparation process and high thermal stability. The fluorescence intensity of the sensor has a linear negative correlation with the copper ion concentration in the aqueous solution, and the detection sensitivity can reach 20 μmol/L. Its simple operation and sensitive response make it complementary to the advantages of atomic absorption spectrophotometry. It is suitable for in situ detection of copper ion pollution in water. This loading method is universal, and provides a new way to apply other quantum dots to devices for the detection of certain metal ions, which achieves the purpose of rapid, recyclable and environmentally friendly detection of heavy metal ions.

    Study on aqueous precipitation copolymerization of AN-MA-IA initiated by water-soluble azo initiator AIBA
    QIN Tong, XI Zhenhao, ZHAO Ling, YUAN Weikang
    2021, 72(2):  1149-1155.  doi:10.11949/0438-1157.20201061
    Abstract ( 652 )   HTML ( 12)   PDF (1208KB) ( 294 )  
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    PAN copolymers with different molecular weights were prepared by aqueous precipitation polymerization using hydrophilic groups containing 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AIBA) as an initiator, acrylonitrile (AN), methyl acrylate (MA) and itaconic acid (IA) as monomers, and β- Mercaptoethanol (β-ME) as chain transfer agent. The effects of monomer concentration, AIBA concentration and β-ME concentration on the polymerization reaction were studied. According to the decomposition half-life of AIBA and the law of monomer reactivity, the polymerization temperature of 70℃ and pH=4.7 were determined as the optimal reaction conditions. The experimental results showed that the AIBA concentration is key factor for monomer conversion. PAN copolymers with molecular weight of 60000 to 500000 can be obtained by adjusting the AIBA concentration, and higher AIBA concentration results in boarder molecular weight distribution due to the change of the polymerization site. When the concentration is within 0.2%(mass), the molecular weight regulator β-ME can control the molecular weight of PAN copolymer and narrow its distribution.

    Influence of pore volume and heating process on preparation of aluminum nitride powder by carbothermal reduction method
    WEI Juan, WANG Yujun, LUO Guangsheng
    2021, 72(2):  1156-1168.  doi:10.11949/0438-1157.20200905
    Abstract ( 399 )   HTML ( 3)   PDF (3580KB) ( 176 )  
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    Carbothermal reduction nitriding method is the main method for industrial preparation of high-purity aluminum nitrite (AlN) powder. In this paper, the aluminum sources with different pore volumes were synthesized through a micro-reactor, and the influence of the pore volume and micro-morphology of the precursor on the AlN powder was systematically investigated, and the activity of the selected precursor was verified by kinetic simulation. At the same time, the influence of the heating process of the nitriding reaction was also explored. Finally, through optimizing the aluminum source and heating process, the AlN powder with a purity of more than 99% was obtained, with an average particle size of about 150 nm and element O content of 0.55%.

    Study on preparation and performance of aqueous binder for lithium iron phosphate electrodes in lithium-ion battery
    CAO Jianing, GAO Xiang, LUO Yingwu, SU Rongxin
    2021, 72(2):  1169-1180.  doi:10.11949/0438-1157.20201085
    Abstract ( 797 )   HTML ( 9)   PDF (6573KB) ( 347 )  
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    LiFePO4 is a widely used cathode material for lithium-ion batteries. Polyvinylidenefluoride (PVDF), as a traditional organic solvent soluble binder, is still used in the preparation of LiFePO4 cathode. The water-based binder which can be used in the preparation of LiFePO4 cathode still needs to be further studied. A novel water-based binder PSEHA with different structures for LiFePO4 cathodes was prepared via copolymerizing polystyrene (St) and 2-ethylhexyl acrylate (2-EHA) with a reactive emulsifier to improve the performance of lithium-ion battery. The influence of binder structure on battery performance was studied. Without unsaturated double bonds, PSEHA binder has good oxidation resistance. Its low swelling ratio can effectively prevent structural damage caused by excessive swelling, and the use of reactive emulsifiers can solve the residue of emulsifier. The LiFePO4 cathode prepared with the optimal binder showed excellent electrochemical stability. After 100 cycles, the LiFePO4 cathode in coin cells maintained stable cycling performance with retention of 96% at the rate of 1 C, while the SBR was only 93.9%. The capacity retention rate of the soft-packed full battery after 170 cycles at 1 C rate is still 98.9%. This new type of water-based binder is of great significance to promote the preparation of LiFePO4 cathode in water-based systems.

    Crystallization and degradation behavior of poly(lactic acid)/poly(ethylene glycol) blends
    ZHANG Kuangsheng, TANG Meirong, XUE Xiaojia, LI Kai, SHAO Yan, ZHOU Jian, YUE Chongchong, LI Zhuangzhuang, PAN Pengju
    2021, 72(2):  1181-1190.  doi:10.11949/0438-1157.20200323
    Abstract ( 615 )   HTML ( 10)   PDF (3156KB) ( 221 )  
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    Aiming at the problem of poor hydrophilicity and long degradation period of polylactic acid (PLLA), it is modified by blending with hydrophilic polymer polyethylene glycol (PEG). A series of PLLA/PEG blends with different blend compositions were prepared by melt blending in torque rheometer. The crystallization and melting behavior, hydrophilicity and degradation properties of PLLA/PEG blends were systematically studied. Results shows that the addition of PEG enhances both the crystallization ability of PLLA and its crystallization temperature during cooling. In isothermal crystallization process, the crystallization rate of PLLA in blends is much faster than that of pure PLLA. Hydrophilicity and degradation rate of the material can be tuned by varying the blend composition. The surface contact angle of PLLA/PEG blends decreases with the increase of PEG content. Both PLLA and PLLA/PEG blends can be degraded in aqueous solution; the degradation ability is significantly improved with PEG presents. The degradation rate of PLLA/PEG blends can be accelerated by increasing of PEG content and increasing of acid or alkali solutions concentration.

    Study on oil-water separation of superhydrophobic and self-cleaning fluorinated graphite modified stainless steel mesh
    LEI Ran, WANG Jiarou, ZHAO Song, WANG Zhi
    2021, 72(2):  1191-1201.  doi:10.11949/0438-1157.20200864
    Abstract ( 436 )   HTML ( 13)   PDF (7644KB) ( 145 )  
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    Epoxy resin and fluorinated graphite (FG) nanosheets were used to modify the surface of 200 mesh(75 mm), 300 mesh(50 mm) and 400 mesh(37.5 mm) stainless steel meshes to prepare fluorinated graphite modified steel meshes with superhydrophobic and self-cleaning properties. The mixture of hexane/water, dichloromethane/water, decane/water, toluene/water and diesel/water can be quickly separated by the FG modified steel mesh under its own gravity, and the separation efficiency is above 99.89%. At the same time, the fluorinated graphite modified stainless steel mesh also has good reusability and mechanical durability. After 100 cycles of recycling and 100 times of wear under the action of external force, it still maintains good superhydrophobic properties.