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Table of Content
05 December 2021, Volume 72 Issue 12
    Reviews and monographs
    Key role of chemical engineering in transition to low-carbon development in perspective of the linkage between resource utilization and carbon emissions
    Bing ZHU,Dingjiang CHEN,Meng JIANG,Yucheng REN,Yuheng CAO,Wenji ZHOU,Shanying HU,Yong JIN
    2021, 72(12):  5893-5903.  doi:10.11949/0438-1157.20211468
    Abstract ( 951 )   HTML ( 58)   PDF (844KB) ( 551 )  
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    The current material resource utilization model urgently needs to transform to low-carbon development. It requires chemical engineering researchers, practitioners, and stakeholders in process industries to reinvestigate the relationship between resources utilization and carbon emissions from a systematic perspective. Based on the latest progress results on resource efficiency and low-carbon transition, the analysis of this study obtained three understandings on the interlinks between resource efficiency and low-carbon development. (1) Synergy: improving resources efficiency benefits carbon reduction. Utilization of resources is deeply coupled with carbon emissions, and improving the resource efficiency significantly step up the transition towards low-carbon society. (2) Trade-off: the low-carbon transition is built upon large demands for crucial resources. Accelerating technology innovation and advancing the circular economy are essential to offset these impacts. (3) The utilization mode of fossil fuel resources will undergo a fundamental change in the contexts of climate change to form the mode that fossil resources should be used as ‘materials' rather than ‘fuels'. Transiting towards the mode of ‘sustainable energy' and ‘sustainable carbon resource' is the direction of development for low-carbon process industries. As the core discipline dealing with the transformation and utilization of resources, chemical engineering is expected to play an essential and irreplaceable role in the low-carbon transition.

    Early exploration of fluidization theory and its inspiration to the future
    Zhuang WANG, Xiao LYU, Yuanyuan SHAO, Jesse ZHU
    2021, 72(12):  5904-5927.  doi:10.11949/0438-1157.20211278
    Abstract ( 773 )   HTML ( 34)   PDF (5007KB) ( 510 )  
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    Since its inception in 1921, the fluidization science and technology has gone through rapid and successful developments. The first half century has not only seen many new fluidization processes developed in the industry, but also many theoretical and fundamental studies which served as solid building blocks for the advancements. The early theoretical research on fluidization was first represented by Lewis and Elgin of the "American School", who adopted a "general" research approach based on uniformly suspended single particle flow. Then, the two-phase theory was proposed by Toomey, Rowe and Davidson of the "British School", who adopted a "regional" research approach based on dividing and examining different phases to characterize the aggregative nature of fluidization. In addition, Wilhelm and Kwauk proposed the classification of particulate and aggregative fluidization, Ergun and Richardson-Zaki put forward the several basic equations of fluidization for minimum fluidization velocity, bed pressure drop and bed expansion. These results are the cornerstone of fluidization research. The development of early theories are still of great significance that continue to influence the current research strategies and directions, and provide the basis for enhancing multiphase flow reaction processes, for the economic and social developments, and for achieving the strategic objectives of energy conservation, emission reduction and carbon neutralization.

    Pseudo-particle modeling of multi-scale reaction-transport coupling
    Wei GE, Chengxiang LI, Feiguo CHEN
    2021, 72(12):  5928-5935.  doi:10.11949/0438-1157.20211284
    Abstract ( 472 )   HTML ( 21)   PDF (3621KB) ( 613 )  
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    The coupling of reaction and transport is characteristic for many chemical processes. With the ever-rising standards for precise control of the processes, and the fast development of process intensification and micro-chemical systems, the traditional framework of describing reaction and transport at micro- and macro-scales separately has faced many challenges. By integrating the advantages of hard-sphere and soft-sphere molecular dynamics simulation methods, pseudo-particle modeling has provided an effective microscopic method with significantly simplified molecular interactions and tremendously higher efficiency for describing the complexity of strong reaction-transport coupling at the meso-scale between the micro- and macro-scales. This article will briefly review the background and development of the method and demonstrate its application in gas-solid multi-phase adsorption and catalysis, gas-liquid nano-/micro-flow and so forth.

    Review of bubble breakup modelling and experimental study in turbulent flow
    Huahai ZHANG, Yuelin WANG, Banghao LI, Tiefeng WANG
    2021, 72(12):  5936-5954.  doi:10.11949/0438-1157.20211345
    Abstract ( 553 )   HTML ( 33)   PDF (4039KB) ( 468 )  
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    The mechanisms and models of bubble breakup in a fully developed turbulent flow are reviewed. The breakup mechanisms are classified into four categories: turbulent eddy collision, viscous shear stress, vortex shear shedding-off, and interfacial instability. The reported models for predicting the bubble breakup rate and daughter bubble size distribution are systematically summarized. The development and limitations of the existing bubble breakup models are analyzed and discussed, and the future direction of model development and improvement are proposed. Experimental studies of breakup of single bubbles in turbulent flow are summarized. According to the methods of producing turbulence, the experiments are divided into four types: turbulence generated by increasing liquid velocity, turbulence generated by internals, turbulence generated by stirring, and turbulence generated by conical reactor and stirring. The development and limitations of existing bubble breakup experiments are discussed. Finally, the bubble breakup rates predicted by the models are compared with experimental data, showing that several bubble breakup models in the literature have good prediction ability.

    Research progress on quantitative exploration of the interaction mechanism between droplets
    An CHEN, Guangsheng LUO, Jianhong XU
    2021, 72(12):  5955-5964.  doi:10.11949/0438-1157.20210925
    Abstract ( 641 )   HTML ( 20)   PDF (3047KB) ( 441 )  
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    Emulsions have been widely used in various fields including daily life, medical health and industrial production. It plays an important role in understanding and revealing the stability mechanism of emulsions and developing novel functional emulsions for quantitative measurement and study of the interaction force between monodisperse droplets. With the development of quantitative measurement tools, surface force apparatus, atomic force microscopes, and optical tweezers have made it possible to quantitatively study the stable mechanism of emulsions. The surface force apparatus is mainly used to measure the interaction force between two flat surfaces. The polymer or functional material to be measured needs to be coated between the two planes. The atomic force microscope mainly focuses on the study of the relationship between the deformation of the droplet and the surface force. Optical tweezers technology "non-contact" captures and clamps two micron-sized droplets for in-situ measurement of the interaction force between the droplets. This article focuses on the research status of the three quantitative measurement tools and the differences in their research systems, and prospects for future research on the interaction mechanism between droplets.

    Recent progress in scale-up integration of microfluidic droplet generators
    Chuanfu DENG,Wei WANG,Rui XIE,Xiaojie JU,Zhuang LIU,Liangyin CHU
    2021, 72(12):  5965-5974.  doi:10.11949/0438-1157.20210921
    Abstract ( 500 )   HTML ( 38)   PDF (3421KB) ( 383 )  
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    Compared with conventional emulsification method, droplet microfluidics can controllably prepare monodisperse droplet templates in microchannels for synthesis of various functional microspheres, and is widely used in a lot of fields such as biological, medical, pharmaceutical and environmental engineering. Due to the low production rate of a single microfluidic droplet generator, scale-up integration of microfluidic droplet generators has become the technical difficulty to widespread utilization at the industrial scale. This paper reviews recent progress in scale-up integration of microfluidic droplet generators. Scale-up integration strategies for different types of microfluidic droplet generators, including droplet generators based on shear force, interfacial tension and passive break-up mechanisms, are mainly introduced.

    Application of copper-based catalysts for hydrogen production in methanol steam reforming
    Xiaoming SUN, Qihao SHA, Chenwei WANG, Daojin ZHOU
    2021, 72(12):  5975-6001.  doi:10.11949/0438-1157.20211085
    Abstract ( 647 )   HTML ( 32)   PDF (9643KB) ( 330 )  
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    In recent years, with the ever-increasing demand for energy, the greenhouse effect caused by the burning of fossil fuels has made the earth's climate worse. How to effectively reduce carbon emissions has become the research focus of scientists from all over the world. The conversion of carbon dioxide into green liquid fuels (such as methanol) is an important direction. Carbon capture is realized by methanol synthesis (MS), and then methanol steam reforming (MSR) is carried out to prepare hydrogen energy when energy is needed, so as to realize the closed-circuit circulation of carbon dioxide and the storage of hydrogen energy. Among many catalysts used in methanol steam reforming (MSR), Cu-based catalysts have attracted extensive attention because of their low price and high activity. This review summaries the research progress of Cu-based catalysts in methanol steam reforming, including mechanism exploration, catalyst optimization and future development outlooks, highlighting the effect of high dispersion and valence states engineering of Cu, together with synergy between Cu and metal oxides supports in tailoring the performance of Cu-based catalysts.

    Progress in the aromatization of methanol or alkane in multi-stage fluidized beds
    Hongmei WANG, Huiqiu WANG, Wenlong SONG, Chaojie CUI, Zhaohui CHEN, Chenxi ZHANG, Weizhong QIAN, Fei WEI
    2021, 72(12):  6002-6015.  doi:10.11949/0438-1157.20211199
    Abstract ( 242 )   HTML ( 6)   PDF (3938KB) ( 125 )  
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    For the aromatization of methanol with metal-zeolite catalysts, the shape selectivity effect of ZSM-5 is invalid for C2—C5 hydrocarbons, resulting in the formation of by-products (inert alkanes) in large quantities and the decrease of the single pass yield of aromatics. The present work reviewed the catalytic transformation mechanism, the structure of multi-stage fluidized bed reactor and their application, and the progress of the enhanced conversion of methanol and the intermediates (alkanes) with temperature shifting, multi-stage fluidized bed technology. In different axial positions of the fluidized bed, according to the activity of the gaseous reactants and intermediates, different temperatures can be used to promote the conversion of methanol and alkane intermediates. As a result, the single pass yield of aromatics can be significantly improved, as well as reducing the downstream separation cost and energy consumption. In addition, the alkane aromatization involved in it may also be developed into an independent technology for the wide use.

    A states-of-the-art review on research progresses and prospects of liquid-liquid extraction columns
    Jiyizhe ZHANG, Yundong WANG, Weiyang FEI
    2021, 72(12):  6016-6029.  doi:10.11949/0438-1157.20210922
    Abstract ( 599 )   HTML ( 27)   PDF (3723KB) ( 326 )  
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    Liquid-liquid extraction is a widely used separation technique, and has important applications in petrochemical, pharmaceutical extraction, metal separation and other fields. Extraction column is one of the common extractors to realize this process. Nowadays, the design of extraction column still highly relies on the previous experience and tedious experiments. Recent research progresses on extraction column were reviewed. Experimental measurement techniques for fluid flow, drop size and concentration field were summarized. Drop-based modeling method and multi-scale computational fluid dynamic simulation were introduced. Studies on process intensification were reviewed. As moving towards digitalization and sustainability chemical processes, some future work was suggested. For experimental methods, in situ measurements and real-time analysis need to be developed. For modeling and simulation methods, more attention should focus on microscopic interfacial behaviors and influence of mass transfer. Based on the advanced experimental and simulation method, new column and internal design need to be further developed based on new extraction system for process intensification to face future challenges in chemical processes.

    Research progress in CO2 removal technology of natural gas
    Zongping HONG, Chumei YE, Hong WU, Peng ZHANG, Cuijia DUAN, Biao YUAN, Shuo YAN, Zan CHEN, Zhongyi JIANG
    2021, 72(12):  6030-6048.  doi:10.11949/0438-1157.20210855
    Abstract ( 1201 )   HTML ( 61)   PDF (1869KB) ( 1015 )  
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    Natural gas is a kind of clean energy with high calorific value, but raw natural gas contains a certain amount of acid gas CO2, which will cause problems like heating value reduction and pipeline corrosion. Therefore, it is necessary to remove CO2 from natural gas before subsequent transportation and utilization. This article introduces four decarburization technologies: cryogenic distillation, solvent absorption, adsorption and membrane separation. The process characteristics and typical industrial applications of each technology are analyzed in details and compared from the aspects of feed conditions of raw gas, removal efficiency, energy consumption and cost efficiency, which is of great engineering significance and provides guidance for the selection of separation processes in different actual conditions. Membrane separation technology has certain advantages of small equipment foot print, low energy consumption and high-cost efficiency. Moreover, the flexibility and adjustability of stages in membrane process enables it with high CO2 removal rate and low hydrocarbon loss. Therefore, membrane separation technology exhibits good development and application prospects, which is especially suitable for space-limited applications, such as CO2 removal from natural gas on offshore platform.

    Absorption of low-concentration CO2 by industrial effluents: feasibility and application
    Wenjiao XU, Huaigang CHENG, Fangqin CHENG
    2021, 72(12):  6049-6061.  doi:10.11949/0438-1157.20211075
    Abstract ( 397 )   HTML ( 8)   PDF (2072KB) ( 165 )  
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    The low-concentration CO2 waste gas produced by the combustion of chemical fuels can be absorbed by industrial waste water. Based on the current research status, this review reports the research progress of CO2 waste gas uptake with industrial waste water, the feasibility is analyzed. The reaction principle of waste gas with CO2 and industrial effluents is summarized, which can be roughly divided into three reaction types: neutralization reaction, metathesis reaction, and microbial degradation. Its absorption kinetics is discussed. The equipment and process of industrial waste water absorbing low-concentration CO2 waste gas are summarized. In this treatment mode, the adsorption of CO2 has a good effect on reducing the pH of lye and removing harmful substances from the waste water. Meanwhile, it can also obtain products with recycling value, such as micro/nano calcium carbonate and biodiesel, which can be applied to industrial production to realize the deep recycling of waste resources. In addition, the life cycle assessment of CO2 waste gas absorbed by industrial waste water are analyzed, and further the environmental impact and economic feasibility are analyzed by evaluating energy consumption, carbon emission and cost under specific process conditions. Combining the prospect of CO2 emission reduction, this review discusses the challenges of using industrial waste water as a low-concentration CO2 absorbent from the perspective of industrial application, and prospects for its future industrialization development.

    Research progress in poly(ionic liquids) materials for CO2 membrane separation
    Yifei CHEN, Jiaming WANG, Xuehua RUAN, Gaohong HE
    2021, 72(12):  6062-6072.  doi:10.11949/0438-1157.20211082
    Abstract ( 388 )   HTML ( 9)   PDF (1909KB) ( 787 )  
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    In recent years, global carbon dioxide emissions have exceeded 37 billion tons per year, which has severely affected the climate and the natural environment. There is an urgent need to develop carbon capture, utilization and storage technologies. Gas membrane separation, as a kind of process without phase change, could be launched under mild condition and concise operation. This technique, along with the continuous upgrade in both selectivity and permeability for membrane materials, has been the major tendency for global carbon capture. In this work, poly(ionic liquids), honored to be the next-generation membrane materials, are introduced. These new emergent materials, generally abundant with CO2-philic groups, are hopeful to achieve ultra-high selectivity for carbon capture. The design and synthesis of specific cationic poly(ionic liquids), including both main-chain and branched-chain types, were summarized from the viewpoint of solution-diffusion mechanism for gas permeation. The emphases in this review are the selection of cationic and anionic groups, the selection of synthesis routes, and the micro-structure design for membranes. Furthermore, the advantages and the challenges to utilize those functional poly(ionic liquids) as membrane materials for CO2 separation are discussed.

    Research progress on microstructure regulation of molecular sieving membranes for H2/CH4 separation
    Bo LIU, Yichang PAN, Rongfei ZHOU, Weihong XING
    2021, 72(12):  6073-6085.  doi:10.11949/0438-1157.20211119
    Abstract ( 545 )   HTML ( 17)   PDF (4171KB) ( 287 )  
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    Hydrogen energy has the advantages of high combustion value and zero carbon emissions. The development of hydrogen energy technology is an important measure to realize the“carbon peak and carbon neutral”strategy. The current hydrogen is mainly produced from the water shift reactions of natural gas, by-produced from the fabrication of ethylene and propylene in the petroleum industry and purge gas. Separation of hydrogen from hydrocarbons (methane as the typical composition) is necessary for the natural gas and petroleum- based hydrogen production. Separation technologies of H2/CH4 mixture include pressure swing adsorption, cryogenic distillation and membrane separation. Molecular sieving membranes [zeolite and metal organic frameworks (MOFs)] become the most potential ones for the energy-saving separation of H2/CH4 mixtures due to their advantages of precise molecular sieving, high separation performance and anti-aging properties. The strategies of microstructure regulation and H2/CH4 separation performance of molecular sieving membranes and the relationship of structure-performance were stated in this review. Opportunities and challenges of molecular sieving membranes were analyzed for H2/CH4 separation. In order to quantify and compare the separation performance of different membrane materials, the performance data of molecular sieving membranes for H2/CH4 separation were summarized in 2008 Robeson upper bound chart that was previously used for the comparison of polymeric membranes. The economically available target regions of the separation performance of molecular sieving membranes for hydrogen separation were also predicted.

    Advances in nanostructured enzyme catalysts
    Huan XIA, Diannan LU, Jun GE, Jianzhong WU, Zheng LIU
    2021, 72(12):  6086-6092.  doi:10.11949/0438-1157.20211409
    Abstract ( 385 )   HTML ( 15)   PDF (948KB) ( 284 )  
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    Loading the enzyme on the carrier can improve the stability of the enzyme in industrial applications and facilitate repeated use. Utilizing nanostructured materials for enzyme immobilization has offered unprecedented opportunities in enhancing enzyme stability in adverse conditions found in industrial practices and thus extending the application spectra of enzymatic catalysis. This review summarizes recent progress of our group in exploring nanostructured enzyme catalysts using inorganic crystals, metal-organic frameworks, graphene and environmentally responsive polymers as matrixes, as well as a new molecular simulation method that combines with Markov-state modeling for establishing a process profile with molecular insight. The prospects of the nanostructured enzyme catalysts are also discussed.

    Intelligent design of microbial cell factory
    Zhen ZHANG, Xuecheng ZENG, Lei QIN, Chun LI
    2021, 72(12):  6093-6108.  doi:10.11949/0438-1157.20211163
    Abstract ( 718 )   HTML ( 47)   PDF (3157KB) ( 1130 )  
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    Design-build-test-learn (DBTL) cycle in the construction of cell factories is the basic research idea for the development of microbial cell factories. However, the traditional design methods of microbial cell factories are time-consuming, laborious and low accuracy, which affects the development efficiency of microbial cell factories. At present, the growing scale of biological database and artificial intelligence have promoted the rapid development of computer-aided intelligent design of microbial cell factorials, and improved the design efficiency and application in synthetic pathway design, regulatory element design and global optimization design. This article reviews the intelligent design tools in the three links of pathway prediction, component design, and combination of pathways and components in microbial cell factories. The rapid development of intelligent design of microbial cell factory will have a transformative impact on the field of biological manufacturing.

    Progress for chemicals production via microbial cell factory: selecting several small molecules and macromolecular products as examples
    Yukun ZHENG, Qing SUN, Zhen CHEN, Huimin YU
    2021, 72(12):  6109-6121.  doi:10.11949/0438-1157.20211285
    Abstract ( 628 )   HTML ( 46)   PDF (3972KB) ( 363 )  
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    The creation and optimization of microbial cell factories are an important part of green biological manufacturing. Based on introduction of important enabling technologies for construction of high-efficiency microbial cell factories, recent progress for producing representative chemicals via microbial cell factories was reviewed. First, the important roles of some key enabling technologies, including both the classical methods such as promoter engineering and metabolic flow analysis and the new developments such as CRISPR gene editing, mutagenesis-coupled high throughput screening and artificial-intelligence-based bioinformatics, were described and discussed. Next, taking organic alcohols, organic acids, organic amines, polysaccharides and polyesters as examples, diverse genetic strategies for developing superior engineered cell factories were highlighted, and the highest production levels of different representative products were also summarized. Finally, the overall development trend and prospect for production of bulk chemicals and macromolecules by microbial cell factories in the future are forecasted.

    Tailoring the thermodynamic properties of complex oxides for thermochemical air separation and beyond
    Runxia CAI, Fanxing LI
    2021, 72(12):  6122-6130.  doi:10.11949/0438-1157.20211333
    Abstract ( 381 )   HTML ( 9)   PDF (1578KB) ( 379 )  
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    Carbon dioxide emission reduction has become one of the important issues for the development of various countries. Conventional separation steps in chemical manufacturing usually come with a low second law efficiency, leading to large amounts of energy consumption as well as CO2 emissions. By coupling separation with chemical reactions using an oxygen storage material, the chemical looping technology represents a promising approach to intensify chemical manufacturing via simplified product separation and cascade energy utilization. As a result, a significant increase in exergy efficiency can be realized. A combination of the chemical looping strategy and high throughput computation based on ab-initio materials simulation has the potential to rationalize the design of complex oxides for various applications. In this paper, three representative chemical looping processes, i.e., chemical looping air separation (CLAS), chemical looping oxidative dehydrogenation (CL-ODH), and chemical looping thermochemical energy storage (CL-TES), are used to exemplify the strategy to tailor the thermodynamic properties of complex oxides. Thermodynamic analysis showed that the desired thermodynamic properties for the oxides vary considerably depending on the target application. Therefore, a key direction for the development of the chemical looping strategy is application-specific and precision-engineering of complex oxides to push the existing boundaries for process efficiency and emission reduction.

    Fundamentals and pilot demonstration of coal directional pyrolysis to high quality tar and gas products based on process intensification and reaction regulation
    Fang WANG, Xi ZENG, Tingting WANG, Xiaorong WANG, Rongcheng WU, Guangwen XU
    2021, 72(12):  6131-6143.  doi:10.11949/0438-1157.20211334
    Abstract ( 330 )   HTML ( 8)   PDF (4546KB) ( 350 )  
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    From the viewpoint of reaction engineering, this study compared the characteristics of existing coal pyrolysis technologies to tar and gas products, summarized the effect of heat and mass transfer in the key steps of coal pyrolysis process on volatiles, such as intra-particle generation and release, inter-particle diffusion and residence in the reactor, analyzed the effect of secondary reactions on products quality, and finally revealed the root of low yield, poor quality and high dust content in the target products of the existing coal pyrolysis technologies. On this basis, the effective measures of coal directional pyrolysis were proposed, including high temperature heating and fast heat transfer in the volatiles generation and char poly-condensation, tar reforming and dust filtering in the char bed during volatiles release, and directional overflow of volatiles by setting up gas channels in the reactor. Then, the technology of coal directional pyrolysis by a moving bed with internals developed by the research group was introduced. The adopted internals included heat transfer plate and gas collection cavity, by which the heat and mass transfer was intensified, the direction of gas flow in reactor was guided orderly and dust was filtered by the slowly moving char bed. With respect to this pyrolysis technology, the fundamental research in a pyrolysis equipment with a processing capacity (PC) of 1—5 kg/time, the model test on a pyrolysis equipment with a PC of 100 kg/time, and a pilot demonstration on a plant with a PC of 1000 t/a have been conducted. The results fully confirm the advantages of this pyrolysis technology in the simultaneous improvement of yield and quality for both of tar and pyrolysis gas, the reduction of dust content in oil, the good adaptability of crushed coal feedstock. Based on the above research, the internal component directional pyrolysis technology and the heat/electricity-oil-gas co-generation technology based on this technology have been formed.

    Recent progress on lithium plating/stripping mechanisms in lithium metal batteries
    Rui ZHANG, Xin SHEN, Hong YUAN, Xinbing CHENG, Jiaqi HUANG, Qiang ZHANG
    2021, 72(12):  6144-6160.  doi:10.11949/0438-1157.20211242
    Abstract ( 584 )   HTML ( 20)   PDF (4917KB) ( 512 )  
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    Lithium metal is one of the most promising materials for the next generation secondary batteries. Lithium metal batteries possess an extremely high theoretical energy density, but still face many challenges, such as low Coulombic efficiency and short battery lifespan. In order to realize the reasonable design and optimization of lithium metal battery with high energy density and high safety, it is necessary to have a clear understanding on the mechanisms of ion transport, electron transport, interface reaction and so on. Recently, aiming at the mechanism of dendrite growth, dead lithium formation and solid electrolyte interphase in lithium metal anode, researchers have made many progress in the mechanism research with theoretical calculations and experiments, providing a more comprehensive mechanism understanding for the rational design of lithium metal battery.

    Hydrogen production based-on anion exchange membrane water electrolysis: a critical review and perspective
    Peican WANG, Lei WAN, Zi'ang XU, Qin XU, Baoguo WANG
    2021, 72(12):  6161-6175.  doi:10.11949/0438-1157.20211264
    Abstract ( 2394 )   HTML ( 113)   PDF (2290KB) ( 1718 )  
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    The development of clean and efficient renewable energy is an inevitable trend in the future energy transition. Hydrogen, as a green and pollution-free energy carrier can achieve efficient conversion of hydrogen energy and electric energy via water electrolysis technology, which is expected to be an important regulating means of wind and photovoltaic power generation. Water electrolysis produces hydrogen without pollutant emission, which is expected to be used as an efficient tool to storage and regulate the intermittent power of wind and photovoltaic generation. Comparing with the conventional water electrolysis using alkaline aqueous solution, water electrolysis based-on alkaline membrane can increase current density and improve energy conversion efficiency. Moreover, non-precious metals such as iron and nickel can be used to prepare catalysts for both hydrogen emission reaction (HER) and oxygen emission reaction (OER), no suffering from the drawbacks of expensive resources caused by the use of precious metal catalysts in proton exchange membrane electrolysis of water (PEMWE). In this study, we review the present status of alkaline membrane electrolysis technology for hydrogen production, focusing on self-supported catalytic electrode, alkali corrosion resistant anion exchange membranes (AEMs) and ordered membrane electrode assembles (MEA), including the preparation strategy of self-supported catalysts, the development trend of alkali corrosion resistant ion membrane and advantages of ordered MEA, explaining the coupling principle of mass transfer and reaction in electrochemical engineering. Therefore, this paper will provide guidance for further research of high-performance electrochemical key materials, and promote the development of hydrogen production technology from water electrolysis.

    Research progress of microsphere formulations with narrow size distribution
    Yi WEI, Guanghui MA
    2021, 72(12):  6176-6187.  doi:10.11949/0438-1157.20211117
    Abstract ( 580 )   HTML ( 26)   PDF (4601KB) ( 407 )  
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    Microsphere preparation is a new type of drug delivery system, and its particle size uniformity is very important. It not only affects the repeatability of product batches, but also affects the application effect. Therefore, manufacture of microspheres with uniform and controlled size play key role in microsphere formulations. Our team has studied on membrane emulsification technology for more than 20 years and successfully prepared various polymer microspheres with uniform and controlled size, and applied them in formulation application. The uniform microsphere formulations have the advantages of green production, low cost, good batch-to-batch repeatability, beneficial to scale up. Furthermore, the uniform size of microsphere helps to study the structure–drug efficacy relationships. The drug-loaded microspheres prepared by our team have been successfully applied in sustained-release formulations, vaccines delivery and malignant tumor treatment.

    Research progress of graphitic carbon nitride nanosheets membrane
    Ya ZHANG, Rui WANG, Sisi WEN, Yisa ZHOU, Jian XUE, Haihui WANG
    2021, 72(12):  6188-6202.  doi:10.11949/0438-1157.20210624
    Abstract ( 608 )   HTML ( 20)   PDF (5905KB) ( 276 )  
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    Graphitic carbon nitride (g-C3N4) nanosheets have the characteristics of intrinsic pores, high pore density, high stability, high mechanical strength, large specific surface area and adjustable chemical environment. This review systematically describes the structural properties of g-C3N4 nanosheets and summarizes the typical preparation methods of g-C3N4 nanosheets. Then the different types of g-C3N4 nanosheets-based membranes and relative applications in various separation processes are discussed in detail. Meanwhile, the current existing challenges and future development directions for g-C3N4 nanosheets separation membranes have also been presented. We wish this paper would be helpful for the design and synthesis of high-performance g-C3N4 nanosheets membranes for purification processes.

    Some recent advances in Janus particulate emulsifiers
    Dayin SUN, Yilan YE, Fuxin LIANG, Zhenzhong YANG
    2021, 72(12):  6203-6215.  doi:10.11949/0438-1157.20211277
    Abstract ( 484 )   HTML ( 15)   PDF (5388KB) ( 433 )  
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    Janus particulate emulsifiers integrate the amphiphilic performance of molecular surfactants and the Pickering effect of homogeneous particles, which are highly effective to stabilize emulsified systems. A new tool is thus provided to manipulate and functionalize interfaces, and to deliver functional materials toward interfaces. Relevant developments along with the Janus particulate emulsifier as a tool and soft matter interfacial engineering provide new opportunities for the interdisciplinary fusion of materials science with multiple fields. Composition, size, and microstructure are the key to fine-tuning the Janus granular emulsifier. The large-scale preparation of magnetically responsive Janus particles has been achieved, and it has shown advantages in the advanced treatment of the emulsification system. In recent years, the polymer single-chain nanoparticles and functional composite colloids have enriched the Janus material family, which are attractive in engineering micro-scale objects. Janus emulsifiers at multiple-length scales serve as a powerful tool to solve interfacial engineering problems.

    Research progress on the preparation and properties of biodegradable polyester
    Wenqi ZOU, Tong CHEN, Haimu YE, Shujing ZHANG, Jun XU, Baohua GUO
    2021, 72(12):  6216-6231.  doi:10.11949/0438-1157.20211200
    Abstract ( 936 )   HTML ( 21)   PDF (4971KB) ( 303 )  
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    Compared with traditional polymer materials, biodegradable polymer materials can be degraded into environmentally harmless substances in the natural environment. As one of the important means to solve the white pollution of plastics, biodegradable polymer materials have developed rapidly in recent years. This review summarizes the research progress of biodegradable polyester structure design, modification and industrialization in our laboratory. The introduction of comonomer units and long/short branched structure into the poly(alkylene dicarboxylates) through random/block copolymerization can effectively control the crystalline properties, melt strength and other properties of the material, and then achieve the control of processing properties, mechanical properties and biodegradation rate of the polyesters. Through the innovation and optimization of the polymerization process, the synthesis of high molecular weight unsaturated polyester was achieved, and its polymerization mechanism was clarified. Furthermore, the preparation of reversible crosslinking elastomers was achieved by introducing Diels-Alder reaction/metal coordination active sites in the unsaturated polyester. In-depth study on the crystal structure control and crystallization mechanism of poly(alkylene dicarboxylate) has been carried out, and a method based on the crystallization nucleation kinetics to determine the secondary critical nucleus size of polymer crystals is proposed. Based on isomorphic crystal structure conformation matching, a new type of high-efficiency macromolecular nucleating agent was designed. On the basis of laboratory research, a production line with an annual output of 10000 tons of biodegradable polyester and its copolyesters has been established in cooperation with enterprises. The products have been applied to the preparation of disposable tableware, supermarket shopping bags and plastic film, and the application demonstration of farmland degradable plastic film has been carried out in Xinjiang.

    Fluid dynamics and transport phenomena
    Study and application of FGP packing in energy saving and emission reduction of methanol distillation
    Qunsheng LI, Yang LI, Zhongqi REN, Jiaxing XUE
    2021, 72(12):  6232-6240.  doi:10.11949/0438-1157.20211048
    Abstract ( 336 )   HTML ( 9)   PDF (869KB) ( 183 )  
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    A new series of flow guided packing (FGP-A, FGP-B packing) was designed and developed. The hydrodynamics and mass transfer performance were analyzed in the cold model column by using an air-water-oxygen system, and compared with Mellapak125X packing under the same conditions. The results show that compared with Mellapak125X, the dry pressure drop of FGP125-A and FGP125-B reduced by 22.94% and 31.99% respectively; the wet pressure drop reduced by 41.48% and 47.32% respectively; the flooding gas velocities increased by 4.93% and 7.76% respectively; and the theoretical stages per meter of packing increased by 26.72% and 22.78% respectively. Meanwhile, considering the hydrodynamics and mass transfer performance of FGP packing, it was applied to the methanol distillation section.The results show that the heat load of the condenser is reduced by 16.01% after the application of FGP packing, which can save 461.10 kt of cooling water every year; the heat load of the reboiler is reduced by 26.30%, which is equivalent to carbon dioxide emission reduction of 6651.83 t/a.

    Study on the effects of structural parameters of bubble-cap distributor with Venturi downcomer on the liquid distribution performance
    Hanyang MO, Yumei YONG, Guangji ZHANG, Kang YU, Wenqiang CHEN, Chao YANG
    2021, 72(12):  6241-6253.  doi:10.11949/0438-1157.20210871
    Abstract ( 397 )   HTML ( 14)   PDF (2788KB) ( 596 )  
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    In order to improve the liquid center aggregation of bubble-cap typed gas-liquid distributor in trickle bed reactor and investigate the relationship between structural parameters and performance of liquid distribution, a new gas-liquid distributor with the Venturi downcomer was designed while the effect of its structure parameters on the distribution quality was explored. A cold experimental bench was established, and the performance of the new gas-liquid distributor was verified. Euler-Euler-PBE mathematical model was built up and validated to simulate the gas-liquid flow in the new gas-liquid distributor. Combining the experimental and numerical data, the effect of the structure parameters on pressure drop, liquid distribution, and spray area was analyzed systematically. The results show that the use of a Venturi with a shrink-and-expansion structure as a downcomer can effectively improve the distribution uniformity and spray radius of the entrainment type distributor, and significantly reduce the pressure drop. Based on the orthogonal cases numerically, the significance of main structure parameters was clarified, and empirical correlations of the distribution performance with structural parameters were obtained. The expansion section of the downcomer is a key structure to improve the liquid distribution performance, and the liquid distribution performance is the best when the expansion angle is 30°.

    Catalysis, kinetics and reactors
    A study on kinetics of heterogeneous synthesis of piperacillin
    Yu XIE, Yujun WANG
    2021, 72(12):  6254-6261.  doi:10.11949/0438-1157.20211095
    Abstract ( 374 )   HTML ( 13)   PDF (2568KB) ( 552 )  
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    Piperacillin is an important antibiotic, which can be synthesized by the reaction of ampicillin aqueous solution and methylene chloride solution of 4-ethyl-2, 3-dioxy-1-piperazine formyl chloride (EDPC) at the oil-water interface. In this paper, the constant interface cell is used to study the apparent synthesis reaction kinetics at the interface, and it is determined that it conforms to the first-order reaction kinetic model. The effects of stirring rate, specific boundary area, pH and temperature on the reaction rate were discussed in details. The experimental results showed that when the stirring rate was greater than 250 r/min, there is a "flat zone" of chemical reaction control which is independent of the stirring strength. Under the "flat zone", the reaction rate constant increases with the increase of specific boundary area, pH and temperature. Through the relationship between temperature and reaction rate constant, the kinetic and thermodynamic data of the reaction were obtained, and then the reaction mechanism was deduced by combining with density functional theory (DFT).

    Investigation of electroreduction of carbon dioxide into formate based on machine learning
    Wenxuan LIU, Jiayi ZHANG, Qi LU, Haochen ZHANG
    2021, 72(12):  6262-6273.  doi:10.11949/0438-1157.20211258
    Abstract ( 888 )   HTML ( 44)   PDF (3255KB) ( 418 )  
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    Electrocatalytic reduction of carbon dioxide to high value-added chemical products has provided a new route to alleviate greenhouse effect and other global problems, attracting intensive attention from both industry and academia. However, it still remains a great challenge to develop electrocatalysts with high performance for practical applications. As one of the major products from carbon dioxide electroreduction, formate is of key importance due to its stability, portability, and high volumetric energy density. In this work, we systematically studied the performance of electrochemical reduction of carbon dioxide to formate on various dual-metal-site catalysts using machine learning in conjunction with density functional theory (DFT) calculations. It was determined that the atomic number, electronegativity and ionization energy of metal atoms in the reaction center are major factors influencing the adsorption of formate intermediates over dual-metal-site catalysts. Based on these features, we predicted the adsorption free energy change for the electroreduction of carbon dioxide to formate and its main competitive reaction, hydrogen evolution reaction. 29 out of 105 dual-metal-site catalysts were identified as potential catalysts for formate production from carbon dioxide electroreduction. A similar method was used to predict the structure of the carbon dioxide reduction intermediates on the surface of 105 dual-metal-site catalysts, and it was found that the adsorption energy of the intermediates has a significant correlation with their adsorption configuration.

    Selective oxidation of 5-hydroxymethylfurfural over α-MnO2 nanowires with tunable surface oxidation state
    Wanna ZHAO, Chunmei ZHOU, Yuguang JIN, Yanhui YANG
    2021, 72(12):  6274-6281.  doi:10.11949/0438-1157.20211300
    Abstract ( 388 )   HTML ( 18)   PDF (1664KB) ( 363 )  
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    A series of α-MnO2 nanocatalysts were synthesized by hydrothermal method for the selective catalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). The results showed that the surface average oxidation state (AOS) of the catalysts was positively correlated with the activity of the catalysts, and could be regulated by oxidation/reduction calcination. After optimization, 79% HMF conversion and almost 99% DFF selectivity were achieved in 1 h over a MnO2-NW2 catalyst with the highest AOS of Mn. And the MnO2-NW2 catalyst can be recycle used for more than six times under a simple redox regeneration treatment.

    Separation engineering
    Separation of n-octane and o-xylene by liquid-liquid extraction with ionic liquids
    Mengfan YIN, Zheng TANG, Rui ZHANG, Zhichang LIU, Haiyan LIU, Chunming XU, Xianghai MENG
    2021, 72(12):  6282-6290.  doi:10.11949/0438-1157.20211073
    Abstract ( 442 )   HTML ( 13)   PDF (2084KB) ( 282 )  
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    Separating straight-run naphtha into aliphatic hydrocarbons and aromatic hydrocarbons helps to optimize the utilization of naphtha resource. Solvent extraction is an important way to separate aromatic hydrocarbons and aliphatic hydrocarbons. The design and optimization of extractants are crucial to the extraction process. The effects of various ionic liquids on the extraction and separation performance of n-octane/o-xylene mixtures were studied, and the ionic liquid 1-butyl-2,3-dimethylimidazole ferric tetrachloride ([Bm2im][FeCl4]) was selected with extraction selectivity, distribution coefficient and extraction performance index as evaluation indicators. For low and medium concentration of aromatic hydrocarbons in naphtha (<33%), the extraction selectivity of o-xylene was above 45, the distribution coefficient was in the range of 0.38—0.40, the extraction performance index was above 18, and the dearomatization rate of single extraction reached above 60% at the temperature of 30℃ and the mass ratio of solvent to feed of 4. Compared with traditional solvent (sulfolane), the system had a larger two-phase zone with [Bm2im][FeCl4], which was helpful to separate n-octane and o-xylene. The weak interaction and the binding energy between [Bm2im][FeCl4] and n-octane/o-xylene were investigated with quantum chemistry software, and the results explained the reason why the ionic liquid could extract o-xylene with high selectivity.

    Study on the influence of granulation conditions on Li/Al-LDHs for lithium recovery from low grade brine
    Rui ZHANG, Jing ZHONG, Sen LIN, Jianguo YU
    2021, 72(12):  6291-6297.  doi:10.11949/0438-1157.20211079
    Abstract ( 553 )   HTML ( 17)   PDF (925KB) ( 311 )  
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    The aluminum-based adsorbent is an effective adsorbent for lithium recovery from brines with an ultrahigh Mg/Li ratio. And the granulated Li/Al-LDHs adsorbent has been widely used in the salt lake lithium extraction industry, but low adsorption capacity, slow adsorption rate and powder loss are the common problems in industrial. In this work, the anti-solvent method is used to granulate the Li/Al-LDHs adsorbent powder with high hydrophilicity and the effects of granulating conditions are also investigated comprehensively. The experimental results show that, the smaller the diameter of the adsorbent particles, the faster the adsorption equilibrium is reached. When particle diameter <1 mm, the adsorbent can reach adsorption equilibrium in about 24 h. Diluting the binder concentration can effectively accelerate the adsorption rate of the adsorbent, but would increase the powder loss in the adsorbent particles. Adding NaCl as a porogen can shorten the time for the adsorbent reaching equilibrium, specially, the adsorbent particles can accomplish the rapid adsorption in about 4 h and the lithium adsorption capacity at equilibrium can reach 4.97 mg·g-1 with 20% of the NaCl addition ratio in the Qarham old brine with a high Mg2+/Li+ ratio.

    Biochemical engineering and technology
    Comparative omics study of Spirulinaplatensis mutants based on ARTP mutagenesis breeding system
    Nan SU, Yinan WU, Yinyee TAN, Lihua JIN, Chong ZHANG, Aikawa SHIMPEI, Hasunuma TOMOHISA, Kondo AKIHIKO, Xinhui XING
    2021, 72(12):  6298-6310.  doi:10.11949/0438-1157.20211340
    Abstract ( 386 )   HTML ( 7)   PDF (4841KB) ( 245 )  
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    As an important biological resource on the earth, microalgae provides a large number of primary metabolites for the hydrosphere, and is an important chassis microorganism for the research and application of synthetic biology and biological manufacturing. Spirulina platensis is one of the cyanobacteria that has advantages of high polysaccharide content, high nutritional value, mature culture technology and wide application. The mutagenesis breeding and comparative omics studies can provide important basis for the development of microalgae cell-factory system modification. With atmospheric and room temperature plasmas (ARTP) mutagenesis method, we obtained three S. platensis mutants. By continuous light culture in this study, we characterized the mutants' important physiological characteristics. It was found that the mutants have much higher flocculation intensity than wild strain and differences in important metabolites content. Furthermore, through the mutants' metabolomic analysis and whole genome sequencing, we preliminarily analyzed the mechanism related to mutant phenotype.

    Energy and environmental engineering
    Economic and environmental assessment of biomass coupled coal-fired power generation
    Huimin YUN, Jianjun DAI, Hui LI, Xiaotao BI
    2021, 72(12):  6311-6327.  doi:10.11949/0438-1157.20211165
    Abstract ( 404 )   HTML ( 11)   PDF (2493KB) ( 159 )  
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    This paper establishes an economic and environmental system evaluation model for biomass direct combustion, biomass-coupled coal-fired power generation, and coal-fired power generation. Four types of biomass pretreatment methods are compared. This work quantifies the supply chain costs of different densified solid biomass fuels, levelized cost of electricity (LCOE), emission intensity (EI), marginal abatement costs (MAC) and the profit rate of cost (PRC) considering carbon trading of different power generation strategies. It is found that biomass coupled coal-fired power generation is a lower-carbon biomass utilization path than direct-fired power generation, and can take advantage of the scale effect, i.e., as the power plant scale increase, the LCOE decreases and the PRC increases, respectively, while the direct-fired power generation is the opposite. In comparison with coal-fired power generation, biomass coupled coal-fired power generation has lower LCOE and can benefit from carbon trading, thus has higher PRC. Therefore, biomass coupled coal-fired power generation is an effective way for coal phase-down program.

    Reuse of wastewater from dicamba production by bipolar membrane electrodialysis
    Yuanhui TANG, Wenwen SUN, Taiyu LI, Peng MAO, Yifan JIN, Lin WANG, Yakai LIN, Xiaolin WANG
    2021, 72(12):  6328-6339.  doi:10.11949/0438-1157.20211051
    Abstract ( 268 )   HTML ( 5)   PDF (1959KB) ( 85 )  
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    Bipolar membrane electrodialysis (BMED) is used to convert NaCl in dicamba production wastewater into HCl and NaOH and reuse it in pesticide production to realize the resource utilization of pesticide wastewater. Firstly, batch experiments of BMED that last for 110 minutes were conducted to explore the best-operating conditions for treating sodium chloride solution. The results showed that when the initial concentration of the feed solution was 160 g/L, the current density was 70 mA/cm2 and the initial concentration of acid and base compartment was 0.075 mol/L, the concentration of the resultant HCl and NaOH solution could reach 1.98 mol/L and 2.06 mol/L, respectively. Meanwhile, the current efficiency was as high as 42.74%. Then, considering the COD index of the actual wastewater is because of methanol, sodium chloride solution with different concentrations of methanol was used to simulate the actual wastewater from the dicamba production. After the experiments, a small amount of methanol was detected in the acid and alkali compartments, indicating that there was a certain degree of permeation during the operation of the BMED, but it did not significantly affect the performance of the membrane stack. Based on the results, BMED was adopted to treat the actual wastewater obtained from the dicamba production after some pretreatment, and it was found that the performance of the membrane resembled the situation of treating NaCl solution with high concentration during the operation time. It was proved that the BMED is feasible to realize the reuse of dicamba production wastewater.

    Engineering hierarchical pore network for Li-ion battery electrodes
    Yu WANG, Yu ZHANG, Weiwen TONG, Guanghua YE, Xinggui ZHOU, Weikang YUAN
    2021, 72(12):  6340-6350.  doi:10.11949/0438-1157.20210813
    Abstract ( 426 )   HTML ( 14)   PDF (3396KB) ( 776 )  
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    At higher charging and discharging rates, Li+ diffusion in the electrodes of lithium batteries is severely restricted, resulting in a significant decrease in battery performance. To reduce the diffusion limitations, engineering pore structure of electrodes can be an efficient approach. In this work, a LiCoO2 cathode is taken as a model electrode, the hierarchical pore network of the cathode with low-tortuosity pores is engineered with the aid of a two-dimensional model. The low-tortuosity pores act as "highways" for the transport of Li+, and their porosity and diameter are optimized to achieve the maximum energy density at high discharge rates. The optimal porosity of low-tortuosity pores is highly dependent on the diameter of low-tortuosity pores, and a diameter of low-tortuosity pores less than 10 μm is preferable. The preferable hierarchically structured electrode can be 45.9%—91.4% higher in energy density when the electrode thickness is 200 μm and the total porosity is 0.36. Besides, optimizing hierarchically structured electrodes is unnecessary when the diffusion limitation of Li+ is weak (e.g., electrode thickness ≤50 μm and total porosity ≥0.48). This work should provide some guidance to engineer the hierarchical pore network for high-performance Li-ion battery electrodes.

    Evaluation of aging performance under high temperature of ionic liquid-based pouch supercapacitor
    Zhenzhen YE, Xinqi CHEN, Jian WANG, Bofan LI, Chaojie CUI, Gang ZHANG, Luming QIAN, Ying JIN, Weizhong QIAN
    2021, 72(12):  6351-6360.  doi:10.11949/0438-1157.20211181
    Abstract ( 389 )   HTML ( 9)   PDF (4719KB) ( 353 )  
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    In this paper, a pouch supercapacitor with a structure of mesoporous carbon, ionic liquid (EMIMBF4) and aluminum foam (capacity 40 F) was constructed, and its performance in the 2.7 V, 65℃, 1500 h aging experiment was evaluated. The capacitance of the supercapacitor attenuates about 10% and the internal resistance increases less than 40% after the 1500 h aging. Its performance is compared with the conventional acetonitrile-based pouch. Although the latter exhibits low initial internal resistance, gases in large amounts are produced and the capacitance attenuation ratio and the internal resistance increase ratio are higher under the high temperature cycling condition, compared to the ionic liquid-based pouch. The above comparison shows that ionic liquid-based electrolyte exhibits excellent cycling performance under the assistance of three dimensional conductive and thermal conductivity structure of aluminum foam. In addition, the advantage of non-toxic, low volatile point of ionic liquids would provide the intrinsic safety as used in enclosed spaces, such as in the elevators of skyscrapers.

    Material science and engineering, nanotechnology
    Preparation and performance of para-aramid aerogel powders
    Chunjie XIE, Ran HE, Xinlin TUO, Wantai YANG
    2021, 72(12):  6361-6370.  doi:10.11949/0438-1157.20211071
    Abstract ( 479 )   HTML ( 19)   PDF (25109KB) ( 194 )  
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    Using para-aramid nanofiber (PANF) hydrogel as raw material, the cryogel crushing method and freeze-drying method are combined together to prepare PANF aerogel powder. The microstructure and performance parameters of para-aramid aerogel powder and the influence of preparation conditions on the morphology of the product were systematically studied, and its application was preliminarily explored. The results showed that the aerogel powders have a porous structure. The apparent density, porosity, and Brunauer-Emmett-Teller surface aerogel area are about 17.0 kg?m-3, 98.8% and 126.30 m2?g-1, respectively. The thermal stability of aerogel powders is excellent and almost no decomposition occurs before 500°C under nitrogen atmosphere. The thermal conductivity of aerogel powder is as low as 0.03 W?m-1·K-1. The aerogel powders can be utilized for the adsorption of some kinds of dyes, such as Rhodamine B. Furthermore, the aerogel powders can be used as nanofiller to improve the mechanical performance of some kinds of polymers, such as the hardness of polyurethane latex film. The low thermal conductivity indicated that the aerogel powder might be applied in the area of thermal insulation.

    Biomass-derived B/N co-doped carbon nanosheets decorated with single-layered MoS2 for sodium storage
    Yizhou ZHANG, Xianhong WU, Zhiyu WANG, Jieshan QIU
    2021, 72(12):  6371-6379.  doi:10.11949/0438-1157.20210786
    Abstract ( 354 )   HTML ( 7)   PDF (3509KB) ( 270 )  
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    This work proposed a new strategy for the fabrication of biomass-derived B/N co-doped carbon nanosheets decorated with single-layered MoS2 by the self-assembly of renewable biomass molecules on the surface of 2D layered crystals and fusion of their coordination with ammonium tetrathiomolybdate. In such nanostructure, the presence of carbon nanosheets is beneficial to enlarging the electrochemically active surface area, offering continuous and short electron-transfer pathway, while enabling uniform dispersion of single-layer MoS2 nanostructure within them. The single-layered MoS2 nanostructure significantly increases the Na+ storage capacity and accelerates the redox reaction kinetics upon the charge-discharge process. When applied to sodium ion anode materials, this two-dimensional composite structure exhibits excellent sodium storage specific capacity, rate performance and cycle stability.

    Studies on the performance of high voltage LiCoPO4 cathode materials
    Shengrui CUI, Lintao DONG, Yongcheng JIN, Lan XIANG
    2021, 72(12):  6380-6387.  doi:10.11949/0438-1157.20211076
    Abstract ( 390 )   HTML ( 11)   PDF (5184KB) ( 227 )  
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    The urgent need for high-performance, high-safety energy storage batteries has accelerated the pace of research on olivine-type high-voltage cathode materials. Lithium cobalt phosphate (LiCoPO4) with different Fe and Mn doping contents (10% of the total doping elements) was synthesized by using solvothermal method with diethylene glycol (DEG) and H2O as mixed solvent. The effects of the solvent ratio and element doping contents on the morphology, size, antisite defects and electrochemical properties of as-prepared cathode materials were discussed. The results show that LiCoPO4 demonstrated the highest discharge capacity of 163.1 mAh·g-1 when the solvent ratio of 2.3 was used and LiCo0.9Mn0.05Fe0.05PO4 cathode material prepared under the solvent ratio of 2.3 had outstanding cycling performance and the capacity retention after 100 cycles was 78.9% at 0.5C.

    S-doped carbon nanotubes used as conductive additives to improve the electrochemical performance of LMFP
    Lu ZHAO, Guoqing NING, Xingxun LI
    2021, 72(12):  6388-6398.  doi:10.11949/0438-1157.20210956
    Abstract ( 753 )   HTML ( 12)   PDF (4508KB) ( 498 )  
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    Lithium manganese iron phosphate (LMFP) has a higher energy density compared with lithium iron phosphate (LFP), but its conductivity is lower, resulting in poor rate performance. In this paper, sulfur-doped carbon nanotubes were used to enhance the conductivity of the LMFP electrode, which effectively improved the energy density and power density of the LMFP electrode. Firstly, sulfur-doped carbon nanotubes (SCNT) were obtained by gaseous S doping treatment on carbon nanotubes (CNT), using SO2 generated by CaSO3 pyrolysis as dopant. Compared with the undoped CNTs, SCNTs exhibit better conductivity and hydrophilicity. The LMFP electrodes were prepared by using water as solvent and SCNTs aqueous suspension as conductive additive. The rate performance, cyclic stability and AC impedance were tested at room temperature and low temperature of -10℃, respectively. The results showed that the addition of SCNT as conductive agent effectively improved the conductivity and dynamics of LMFP electrode. The reversible capacities of LMFP electrode with SCNT at 0.2C and 5C were 200 mAh/g and 145 mAh/g, respectively, which were significantly higher than that of LMFP electrode with CNT or CB as conductive agent. Finally, the SCNT-added LMFP electrode was matched with graphite to assemble a full battery, showing ultra-high energy density and power density of 185.0 Wh/kg and 665.5W/kg.

    Preparation and thermal properties research of a novel magnesium chloride hexahydrate-magnesium nitrate hexahydrate/graphite phase carbon nitride composite phase change material
    Wenbo ZHANG, Ziye LING, Xiaoming FANG, Zhengguo ZHANG
    2021, 72(12):  6399-6406.  doi:10.11949/0438-1157.20211067
    Abstract ( 397 )   HTML ( 6)   PDF (3573KB) ( 121 )  
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    The low utilization rate of magnesium resources in Qinghai Salt Lake in China has caused serious resource waste and environmental pollution. If magnesium salt is developed as a phase change heat storage material, its application fields can be improved, thereby promoting the full utilization of magnesium salt resources. In view of the application requirements of medium-low temperature heat preservation and heat insulation, this work selects eutectic salt MgCl2·6H2O-Mg(NO3)2·6H2O(MCH-MNH) with mass ratio of 41∶59 as phase change material based on previous work. MgCl2·6H2O-Mg(NO3)2·6H2O/g-C3N4(MCH-MNH/CN) composite phase change material with low thermal conductivity is prepared by using porous graphite carbon nitride (g-C3N4, CN) as the support material in order to reduce its supercooling and improve its thermal insulation performance. The porous CN is obtained by calcination of urea at 550℃, then MCH-MNH/CN composite phase change material is prepared by adsorption method. The morphology, structure and thermal properties of the composite phase change material are characterized and measured. The results show that the eutectic salt phase change material is uniformly adsorbed in the microporous structure of CN, and the recombination with CN is a physical process without chemical reaction. The composite phase change material has a phase change temperature of 55.2℃ and phase change enthalpy of 92.7 J/g without supercooling. The thermal conductivity of the composite phase change material is 0.3 W/(m·K), which is only half of thermal conductivity of the eutectic salt MCH-MNH, and the heat insulation performance is improved. In addition, the composite phase change material has good thermal stability and has application prospects in the field of medium and low temperature thermal insulation.