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Table of Content
05 February 2023, Volume 74 Issue 2
    Reviews and monographs
    Research progress on regulation of aggregation structure for nascent polyethylene
    Yuming CHEN, Wei LI, Xiang YAN, Jingdai WANG, Yongrong YANG
    2023, 74(2):  487-499.  doi:10.11949/0438-1157.20221089
    Abstract ( 280 )   HTML ( 26)   PDF (2372KB) ( 119 )  
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    The aggregation structure is one of the key factors to achieve high performance of polyethylene. Starting from the design of aggregation structure of nascent polyethylene, aiming at the problems of excessive entanglement, high viscosity, difficult processing and molding of ultra-high molecular weight polyethylene (UHMWPE), the characterization and regulation of nascent polyethylene chain entanglement and its role in the high performance of polyethylene products are reviewed in this paper. The research progress on the regulation of entanglement of nascent polyethylene is reviewed from the aspects of catalyst structure design and polymerization process design, respectively. It is proposed to increase the growth spacing of active chain on the catalyst surface (spatial scale) and introduce the active chain dormancy technology assisted by nanobubbles in the polymerization process to enhance the chain crystallization rate (time scale) and reduce the“scissors difference”between “chain growth and chain crystallization”. The above two control methods provide theoretical guidance for the efficient preparation of low-entanglement polyethylene on the basis of meeting the harsh industrial production requirements.

    The regulation mechanism of additives on the amino acid crystal growth
    Xuan ZHOU, Mengya LI, Jie SUN, Zhenkai CEN, Qiangsan LYU, Lishan ZHOU, Haitao WANG, Dandan HAN, Junbo GONG
    2023, 74(2):  500-510.  doi:10.11949/0438-1157.20220951
    Abstract ( 270 )   HTML ( 15)   PDF (1743KB) ( 154 )  
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    Most of the amino acids grow in needle-like or sheet-like crystal habit, which have problems such as low bulk density and poor fluidity, and seriously affect the post-processing process of the product. Therefore, it is of great significance to control the crystal habit of amino acids. Additives are directly effective in regulating the crystal habit of amino acids and are widely used in industrial production. In this paper, the mechanism of additives on the growth of amino acid crystals is reviewed from the perspectives of inhibiting or promoting crystal growth. There are two main mechanisms for the inhibition of crystal growth by additives: one is that the additive molecules are adsorbed on the crystal surface, which hinders the diffusion and aggregation of solute molecules, the other is that the additive molecules are embedded in the crystal lattice and occupy growth sites. The mechanism of additive promoting crystal growth is that the additive accelerates the aggregation rate of solute molecules on the crystal surface, roughens the crystal surface and reduces the energy barrier removal of the solvent layer. Finally, we propose the prospect of directionally regulating the amino acid crystal growth through molecular design of additives from the perspective of crystal engineering.

    Advances in continuous aerobic oxidation based on nitroxyl radical catalyst in microreactors
    Chenghao ZHANG, Jing LUO, Jisong ZHANG
    2023, 74(2):  511-524.  doi:10.11949/0438-1157.20221021
    Abstract ( 233 )   HTML ( 20)   PDF (2493KB) ( 165 )  
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    The replacement of traditional oxidation technology by continuous liquid-phase aerobic oxidation technology has become a major trend in the development of oxidation reactions. However, molecular oxygen usually needs to be activated by a suitable catalyst system for highly selective oxidation. In recent years, nitroxyl radical catalysts have achieved rapid development due to their ability to efficiently catalyze aerobic oxidation under mild conditions. In addition, sustainable green oxidation processes not only rely on efficient and environmentally friendly catalytic systems, but also on reactor technologies that can enhance mass transfer and reaction performance. This paper introduces the commonly used microreactors and summarizes the research progress of aerobic oxidation reaction in continuous organic synthesis using nitroxide radicals or their derivatives as catalysts. Finally, in view of the potential challenges of the continuous liquid-phase oxidation technology catalyzed by nitrogen oxide radicals at this stage, a prospect for the future application of this technology in the field of fine chemicals is put forward.

    Research progress on synthesis of alkylaluminoxanes
    Mengbo ZHANG, Linjin LOU, Yirong FENG, Yuting ZHENG, Haomiao ZHANG, Jingdai WANG, Yongrong YANG
    2023, 74(2):  525-534.  doi:10.11949/0438-1157.20221002
    Abstract ( 289 )   HTML ( 18)   PDF (1789KB) ( 205 )  
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    The product of methylaluminoxane (MAO) is available commercially, however, central challenges over poor process control, low product yield, and high safety risks, still remain in its synthesis using large-scale reactors. This review presents several conventional hydrolytic routes for MAO synthesis with different techniques to supply water in the reaction system, and primarily focuses upon the development of continuous flow platforms to synthesize MAO, isobutylaluminoxane (IBAO), and modified methylaluminoxane (MMAO) using 3D printed functional devices. In particular, those flow platforms introduce monodisperse microdroplets of water to improve the heat and mass transfer, achieving inherently safe productions of alkylaluminoxanes with high yield and superior co-catalytic activity. The presented flow strategy has a wide array of applications in chemical synthesis, especially when handling fast, highly exothermic, multiphase reactions.

    Synthesis of MoS2-based single atom catalyst and its application in electrocatalysis
    Yue SONG, Qicheng ZHANG, Wenchao PENG, Yang LI, Fengbao ZHANG, Xiaobin FAN
    2023, 74(2):  535-545.  doi:10.11949/0438-1157.20221017
    Abstract ( 343 )   HTML ( 19)   PDF (1805KB) ( 249 )  
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    Due to the advantages of mild reaction conditions and fast reaction rates, electrocatalysis has great prospects in the fields of energy storage and conversion, and synthesis of high-value small molecules. Therefore, the design and development of efficient electrocatalyst are the key to promote the industrialization of electrocatalytic reaction. Molybdenum disulfide (MoS2) is considered as one of the most promising materials for electrocatalysis due to its low cost, adjustable electronic properties and excellent chemical stability. And single atom catalysis is a multi-functional and attractive technology with significant cost reduction and excellent catalytic activity. This article reviews the preparation strategies of MoS2-based single atom catalysts, including electrochemical deposition, wet chemical impregnation, hydrothermal/solvothermal and hydrogen plasma reduction. Furthermore, the applications of corresponding catalysts in the field of electrocatalysis are introduced. Finally, the new research directions and future trends are discussed from three aspects including single atom modification, mechanism study and synthesis process, that means, preparation of polymetallic MoS2-based single atom catalyst, clarifying reaction mechanisms with in-depth characterisation and calculations, development of green synthesis process, etc.

    Progress on rheological properties and multiphase flow of yield stress fluids in microchannels
    Xingyu XIANG, Zhongdong WANG, Yanpeng DONG, Shouchuan LI, Chunying ZHU, Youguang MA, Taotao FU
    2023, 74(2):  546-558.  doi:10.11949/0438-1157.20221091
    Abstract ( 313 )   HTML ( 23)   PDF (2182KB) ( 170 )  
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    Yield stress-type fluids (YSFs) are typical non-Newtonian fluid that have received extensive attention due to their rich rheological properties. Yield stress is an essential feature in high concentration particle dispersion systems and gelatinous substances, such as multiphase emulsions, microencapsule, 3D printing of complex structures and drug delivery. In this paper, the flow characteristics and rheological behavior of simple yield stress fluid and the effects of rheology on multiphase flow systems are reviewed. The coupling mechanism of the fluid flow and fluid rheology, the multiphase flow dynamics, and interfacial phenomena in confined spaces are analyzed. The research directions that need to be promoted are prospected. It provides a reference for numerical simulation, experimental research and application of yield stress-based fluids in microchannels.

    Characterization technique for kinetic coefficients of free radical polymerization
    Yuxiao LI, Qingyue WANG, Khak Ho LIM, Xiaohui LI, Erlita MASTAN, Bo PENG, Wenjun WANG
    2023, 74(2):  559-570.  doi:10.11949/0438-1157.20221217
    Abstract ( 257 )   HTML ( 8)   PDF (699KB) ( 115 )  
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    Free radical polymerization (FRP) is one of the key polymerization reactions, its kinetic coefficient is imperative for mechanism study, chain structure customization, and reaction process control. In this paper, we review the state-of-art characterization technique involved in determination of critical parameters in FRP, i.e., propagation rate coefficient and termination rate coefficient. A pulsed laser polymerization (PLP) in conjunction with size exclusion chromatography (SEC) is effective to determine propagation rate coefficient. A particular single pulse-pulsed laser polymerization (SP-PLP) in conjunction with near infrared (NIR) and electron paramagnetic resonance (EPR) spectroscopy is unrivaled to identify termination rate coefficient. The theory, test prerequisites, and testing conditions for each detection method are outlined, and the effects of increased radical chain length on propagation and termination rate coefficient are discussed. In addition, the potential on the improvement and development of new technique for the propagation rate coefficient and termination rate coefficient is delivered.

    Research progress on film-forming electrolyte additives for Si-based lithium-ion batteries
    Weijiang CHENG, Heqi WANG, Xiang GAO, Na LI, Sainan MA
    2023, 74(2):  571-584.  doi:10.11949/0438-1157.20221106
    Abstract ( 705 )   HTML ( 39)   PDF (3379KB) ( 676 )  
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    Lithium-ion batteries are a key technology for energy storage and utilization. Energy density has become a key indicator in the development of modern batteries. Si-based anodes have received extensive research attention due to their high theoretical specific capacity. But the Si-based materials suffer from serious volume expansion problems. Functional additives are an indispensable part of the electrolyte system which has a significant improvement effect on battery performance, with the characteristics of “small dosage, quick effect”. A stable solid-state electrolyte interface (SEI) film is formed by film-forming additives to stabilize the electrode-electrolyte interface and improve the performance of Si-based anode batteries. This paper summarizes the research progress on film-forming additives for Si-based anodes in recent years. The film-forming additives are discussed in categories according to functional groups or elements, and the synergistic effect of multi-component film-forming additives is briefly described. Finally, the current research status of electrolyte additives for Si-based anodes is summarized and future research directions are prospected.

    The construction of biomimetic materials and their research progress in the field of aquatic environmental chemistry
    Tanjie ZHA, Han YANG, Hejie QIN, Xiaohong GUAN
    2023, 74(2):  585-598.  doi:10.11949/0438-1157.20221204
    Abstract ( 304 )   HTML ( 23)   PDF (851KB) ( 160 )  
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    Inspired by the biomorphic structures or chemical properties of biological molecules, many biomimetic materials are designed and attract considerable attention in the field of aquatic environmental chemistry. In this review, the research progress of biomimetic materials in that field is systematically summarized. Biomimetic materials can be designed by molecular bionics or biomorphic design. Molecular bionic approaches include re-construction or immobilization of the natural material, mimicking the active sites of biological molecules, and mimicking the catalytic environments of natural materials. These biomimetic materials have been applied in the studies of oxidative or reductive removal of contaminants from water and their detection. Its unique structure, mechanism of action and excellent performance make it have strong potential for practical application. The correlation between its microstructure and performance and the controllable synthesis method of the optimized structure are the key issues to be paid attention to in the follow-up research. Finally, the challenges and future development directions of biomimetic materials research in the field of water environment chemistry are discussed.

    Advances in benzimidazole-linked polymer adsorbents and membranes
    Min LI, Xueru YAN, Xinlei LIU
    2023, 74(2):  599-616.  doi:10.11949/0438-1157.20221088
    Abstract ( 286 )   HTML ( 8)   PDF (3652KB) ( 138 )  
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    Benzimidazole-linked polymers have excellent chemical stability, thermal stability, high porosity, high specific surface area, dielectric properties and good mechanical properties by virtue of the strong bonds in their chains, strong interactions among their chains and their versatile functional groups, and thus they were used as materials for efficient separation. In this review, the types and properties of benzimidazole-linked polymers are discussed. Applications, such as adsorbents and membranes separation are extensively reviewed. Finally, the brief summary and tentative perspectives of benzimidazole-linked polymers are presented.

    Research progress of enzymatic reactive crystallization
    Weiyi SU, Jiahui DING, Chunli LI, Honghai WANG, Yanjun JIANG
    2023, 74(2):  617-629.  doi:10.11949/0438-1157.20221223
    Abstract ( 176 )   HTML ( 10)   PDF (1046KB) ( 67 )  
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    Under the background of“carbon peaking and carbon neutrality”, green and sustainable enzymatic reaction is receiving extensive attention. However, it still faces many challenges in practical application, such as the limitation of reaction equilibrium, the decomposition of unstable products, and the product inhibition of enzyme. As an efficient and mature separation technology, crystallization can effectively solve the above problems by removing liquid phase products. Moreover, crystallization is also the “generation”process of crystals, and the combination of crystallization and enzymatic reaction can realize the efficient, green and controllable preparation of crystal products in one step. This paper reviews the research progress of enzymatic reactive crystallization in recent years. Specifically, the development of in situ product crystallization (ISPC) was introduced, and the interplay between crystallization and enzymatic reaction was discussed. From the perspective of crystallization mode and process control, the realization form and continuous process of enzymatic reactive crystallization were described. Finally, the development and application of this coupled process were summarized and prospected.

    Thermodynamics
    A critical discussion on developing molecular property prediction models: density of ionic liquids as example
    Jiahui CHEN, Xinze YANG, Guzhong CHEN, Zhen SONG, Zhiwen QI
    2023, 74(2):  630-641.  doi:10.11949/0438-1157.20221060
    Abstract ( 232 )   HTML ( 15)   PDF (2417KB) ( 261 )  
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    Molecular property prediction models are powerful tools for screening or designing chemicals to meet specific application requirements. However, many key aspects in model development such as the size and diversity of dataset, test set partitioning method, cross-validation, and algorithm selection are not treated with enough rigor, which could lead to doubtful estimation of the true predictive performance of models. Taking the group contribution method to predict the density of ionic liquids as an example, the importance of dataset partitioning and cross-validation in the modeling of molecular property prediction models was discussed. An automatic group fragmentation method of ILs is proposed and the effect of group occurrence threshold(evaluated by the number of ILs containing the group in the dataset) on the prediction accuracy is investigated. By comparing five regression algorithms(multiple linear regression, ridge regression, random forest, support vector machine, and neural network), the group contribution model based on ridge regression has the best prediction performance. The average relative error obtained on the composed dataset is 1.88%.

    Experiment and prediction for the solubility of AlCl3·6H2O in FeCl3, CaCl2, KCl and KCl-FeCl3 solutions
    Wenting CHENG, Jie LI, Li XU, Fangqin CHENG, Guoji LIU
    2023, 74(2):  642-652.  doi:10.11949/0438-1157.20221368
    Abstract ( 255 )   HTML ( 22)   PDF (1027KB) ( 85 )  
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    How to selectively crystallize and separate AlCl3·6H2O from many components is the key to extracting Al from coal gangue, and the thermodynamic equilibrium data of AlCl3·6H2O in the acid leaching system of coal gangue is very important for the control of the crystallization process. The solubilities of AlCl3·6H2O in FeCl3, CaCl2, KCl and KCl-FeCl3 solutions were measured and modeled at temperatures from 25℃ to 85℃ in this work. The effects of temperature and solution concentration on the solubility of AlCl3·6H2O were studied. The concentration of solution was found to be the main factor which affected the solubility. Solubility of AlCl3·6H2O in all solutions was found to decrease obviously with increasing concentration of solution due to the common ion effect of added Cl-. The effect of temperature on the solubility of AlCl3·6H2O in all solutions was slight for the little increment of solubility with increasing temperature. New Bromley–Zemaitis activity coefficient model parameters for the Al3+-Cl- ion pair were obtained by using experimental solubility data. Then the practicability of the modified model was verified, and the results show that it could be used to predict the solubility of AlCl3·6H2O in any single and mixed solution of FeCl3, CaCl2 and KCl.

    Study on viscosity-temperature characteristics and component characteristics of rocket kerosene
    Jiaqing ZHANG, Rongpei JIANG, Weikang SHI, Boxiang WU, Chao YANG, Zhaohui LIU
    2023, 74(2):  653-665.  doi:10.11949/0438-1157.20221560
    Abstract ( 263 )   HTML ( 8)   PDF (2108KB) ( 103 )  
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    In order to study the influence law of temperature change and component change on viscosity of liquid rocket propellant, coal-based/petroleum-based rocket kerosene was used as the research object, and the viscosity data of the two fuels in a wide range of temperature and pressure were obtained, and two kinds of fuels were constructed. The “viscosity-temperature-pressure” mathematical models of the two fuels were constructed. Most model deviations are within the 5% range of experimental expansion uncertainty. It can accurately predict the change of fuel viscosity with temperature and pressure. The viscosity-temperature coefficient and the change rate of isobaric viscosity can reflect the viscosity-temperature characteristics of different fuels. The comparison results show that the absolute values of viscosity-temperature coefficient and isobaric viscosity change rate of coal-based kerosene and petroleum-based kerosene are similar, and they are affected by temperature to almost the same degree. According to the kinematic viscosity gradient, two kinds of critical preheating temperatures for the best atomization combustion effect of rocket kerosene are provided. Grey relation theory was used to analyze the correlation between the composition of rocket kerosene and the viscosity and viscosity change rate, and to study the sensitive component factors affecting the viscosity of rocket kerosene. The results show that monocyclic alkanes have the greatest influence on the viscosity index of low-temperature rocket kerosene, while bicyclic alkanes have the greatest influence on the viscosity index of high-temperature rocket kerosene.

    Hydrate equilibrium model of hydrogen-containing gas considering hydrates structure transformation
    Jingbo GAO, Qiang SUN, Qing LI, Yiwei WANG, Xuqiang GUO
    2023, 74(2):  666-673.  doi:10.11949/0438-1157.20221326
    Abstract ( 185 )   HTML ( 7)   PDF (597KB) ( 204 )  
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    Hydrogen-containing gases commonly used in industry often contain many light hydrocarbons. The change of light hydrocarbons composition will cause the transformation of hydrate structure, which is one of the important reasons for reducing the calculation precision of hydrate thermodynamic model. Therefore, for the light hydrocarbon mixed system, a new hydrate structure parameter (niI) is introduced into the core equation of Chen-Guo hydrate model, and its coefficients are obtained by fitting experimental data, which can be used to judge and calculate the sⅠ/sⅡ hydrate transition. On this basis, hydrogen in hydrogen-containing gas is regarded as an inert gas adsorbed only by small cavities (link cavities) of hydrate, and an improved model considering hydrate structural transition is proposed to improve the prediction accuracy of hydrogen-containing gas. The calculated results show that the average relative deviation of the improved model for different light hydrocarbon gases is reduced from about 5.6% to 2.1%, and for different hydrogen-containing gases is reduced from about 8% to 2.3%. The prediction accuracy of the model has been significantly improved, which can meet the requirements of engineering applications.

    Fluid dynamics and transport phenomena
    Heat dissipation performance of the module combined CPCM with air cooling for lithium-ion batteries
    Jianglong DU, Wenqi YANG, Kai HUANG, Cheng LIAN, Honglai LIU
    2023, 74(2):  674-689.  doi:10.11949/0438-1157.20221068
    Abstract ( 193 )   HTML ( 12)   PDF (4418KB) ( 122 )  
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    The heat generated during the discharge of lithium-ion batteries cannot be dissipated in time, which will lead to a decrease in battery performance. Designing a reasonable heat dissipation structure of the battery pack is a key part of improving battery performance. In this paper, a cooling structure of battery pack based on the combination of composite phase change materials (CPCM) and air cooling is proposed. By combining the pseudo two-dimensional electrochemical model with the three-dimensional heat dissipation model, the heat generation process of the battery and the heat transfer process between the battery and the outside were analyzed, and the effects of the thickness of phase change material (PCM), the content of expanded graphite (EG) in the CPCM, the number of air cooling channels and the flow direction of air cooling gas on the heat dissipation performance of the battery pack were investigated. The results show that the heat dissipation performance of the CPCM/air cooling composite heat dissipation structure is significantly better than that of the battery pack only using CPCM. When the PCM thickness is equal to the battery radius and the EG mass fraction is 20%, the heat dissipation performance of the battery pack is the best. In addition, the two-way ventilation duct design can reduce the battery temperature more effectively. The conclusions can provide theoretical guidance for the heat dissipation design of lithium-ion battery pack.

    Study on gas-liquid mass transfer characteristics in microchannel with array bulges
    Wanyuan HE, Yiyu CHEN, Chunying ZHU, Taotao FU, Xiqun GAO, Youguang MA
    2023, 74(2):  690-697.  doi:10.11949/0438-1157.20221061
    Abstract ( 152 )   HTML ( 8)   PDF (1431KB) ( 86 )  
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    The gas-liquid two-phase mass transfer characteristics of CO2 absorption into N-methyldiethanolamine (MDEA) aqueous solution in the microchannel with the array bulges were studied. The influences of gas/liquid flow rate and MDEA concentration on the volumetric mass transfer coefficient kLa, CO2 absorption rate X, pressure drop ΔP and energy consumption ε were studied under slug flow regime. The deformation of slug bubbles due to the squeezing effect of the array bulges promotes the gas-liquid mass transfer efficiency. Compared with non-array bulge microchannel, the array bulge microchannel obviously enhanced CO2 absorption rate and has larger volumetric mass transfer coefficient for the same energy consumption.

    Study on liquid-liquid distribution in comb parallel microchannels
    Xingyu YANG, You MA, Chunying ZHU, Taotao FU, Youguang MA
    2023, 74(2):  698-706.  doi:10.11949/0438-1157.20221110
    Abstract ( 177 )   HTML ( 8)   PDF (1535KB) ( 90 )  
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    For industrial applications, the parallel amplification of microreactors has become one of the most effective strategies, in which the study on the phase distribution in the parallel multiple microchannels is an important foundation. In this study, the influences of the subchannel interval and flow rates on distribution of liquid-liquid two-phase in comb parallel microchannels were investigated by the use of a high-speed camera. Results indicated that for low flow rates of dispersed and continuous phases (Qc and Qd), the dispersed phase volume fraction in the front branch microchannels was low, while it was high in the rear branch microchannels and the uniformity of daughter droplets was worse. With the increases of two-phase flow rates Qc and Qd, the dispersed phase volume fractions in three different configurations of microreactors were inclined to be consistent. At higher two-phase flow rate, the uniformity of droplets size in the branch microchannels could be significantly increased, and the variation coefficient is less than 0.15. Within the experimental range, the operating range of uniform droplet size distribution in the microreactor with the subchannel interval S = 0.6 mm is the largest.

    Effect of roll on pressure drop in concurrent gas-liquid columns with tridimensional rotational flow sieve tray
    Jianzhao BAI, Zixuan GUO, Dewu WANG, Yan LIU, Ruojin WANG, Meng TANG, Shaofeng ZHANG
    2023, 74(2):  707-720.  doi:10.11949/0438-1157.20221393
    Abstract ( 142 )   HTML ( 2)   PDF (2648KB) ( 119 )  
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    With air-water as the experimental medium, the pressure drop of tridimensional rotational flow sieve tray (TRST) under gas-liquid co-flow mode was measured, under the range of different sprinkle density 78—182 m3·(m2·h)-1, gas phase loading factor 1.19—2.77 m·s-1·(kg·m-3)0.5, the rolling amplitudes Θ=5°—15°, and the rolling periods T=8—20 s. The effects of gas-liquid flux, the number, position and mode of tray installation on pressure drop were investigated and compared with the vertical and tilt conditions. It turns out that, the dry plate pressure drop is less than 35 Pa for forward installation and less than 80 Pa for backward installation. And the dry plate pressure drop is not affected by incline and rolling, but decreases slightly with the increase of incline and rolling amplitude when the gas volume is large. The wet plate pressure drop during rocking is between upright and inclined, and is greatly affected by the rocking angle, and is basically not affected by the cycle. Increasing the gas volume is beneficial to resist the influence of incline and rolling, while increasing the liquid volume will aggravate the influence of incline and rolling. On the whole, the wet pressure drop during the forward and backward installation of the tray is within 90 Pa and 170 Pa respectively, while the change rate of pressure drops during the backward installation is about twice of the forward installation. This is because the gas-liquid flow direction is changed under the backward installation and the energy loss is increased. The pressure drop and the pressure drop change rate of the second and third trays were similar. The prediction models of dry pressure drop and wet pressure drop of TRST under the rolling condition of gas-liquid co-current flow mode were established, and errors are within 10% and 15% respectively.

    Numerical simulation and performance optimization of a new loop gravity heat pipe
    Jianxun CHEN, Jinping LIU, Xiongwen XU, Yinhao YU
    2023, 74(2):  721-734.  doi:10.11949/0438-1157.20221530
    Abstract ( 223 )   HTML ( 8)   PDF (10786KB) ( 61 )  
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    A new loop gravity heat pipe (LGHP) is researched and a simplified two-phase flow numerical model based on VOF method is proposed to study the flow characteristics of the working fluid in the evaporator, which can effectively simulate the generation of bubbles and the location of the dry area in the evaporator of LGHP. Based on the numerical simulation, the channel structure of the evaporator is improved to delay the appearance of the dry zone of the evaporator when it is placed horizontally. Through experimental verification, it is found that the heat transfer performance of the improved evaporator has been greatly improved, and the liquid phase storage capacity of the refrigerant in the evaporator has been improved, which double its critical heat flux (CHF) to 140 kW/m2 (heating power 2000.7 W). It is proved that the simplified model is accurate in simulating the location of the dry area, and can provide a reference for further design and improvement of the flow channel structure of the flat evaporator.

    Lattice Boltzmann simulations of the effect of particles movement on momentum transfer process
    Longfei JIA, Shaotong FU, Xing XIANG, Huahai ZHANG, Tao ZHANG, Limin WANG
    2023, 74(2):  735-747.  doi:10.11949/0438-1157.20221423
    Abstract ( 206 )   HTML ( 5)   PDF (4443KB) ( 61 )  
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    The particle vibration in a gas-solid fluidized bed has a significant effect on transfer process. Lattice Boltzmann method coupled with an improved immersed moving boundary method is used to simulate the single particle vibration with different amplitude A/D and frequency k = fe/f0, and the effect of two-particle vibration with different arrangement and spacing on the drag coefficient, lift coefficient and vortex shedding frequency. The results show that when one single particle oscillating transversely at Re = 100, with increasing A/D, particle locking range becomes larger and the drag coefficient inside the locking interval is larger than that outside, which is beneficial to transfer process. When one single particle oscillating stream wisely at A/D = 1.50, the fluid flow mode changes from 2S→2P→2P+2S→chaos with increasing k. At the same A/D when k < 1.25, the drag coefficient of the transversely oscillating particles is larger than that of the stream wisely oscillating particles, but when k > 1.25, it is opposite. Therefore, the particle transversely oscillating is more favorable for transport at k < 1.25, and the particle stream wisely oscillating is more favorable for transport at k > 1.25. The formation of mutual inhibition vortices of the series double particles reduces the drag coefficient, which is not conductive to the transfer, on the contrary, the parallel double particles promote the transfer, and the effect is the best when H = 3D. The above numerical results provide an idea for strengthening transfer process.

    Catalysis, kinetics and reactors
    Study on efficient dissolution of D-7-ACA using membrane dispersion microreactor
    Yu XIE, Min ZHANG, Weiguo HU, Yujun WANG, Guangsheng LUO
    2023, 74(2):  748-755.  doi:10.11949/0438-1157.20221130
    Abstract ( 146 )   HTML ( 9)   PDF (1854KB) ( 94 )  
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    3-Decarbamoyl-cefuroxime (DCC), the key intermediate for the synthesis of cefuroxime, is obtained by condensing the 3-deacetyl-7-aminocephalosporanic acid (D-7-ACA) solution with the acid chloride. The dissolution of D-7-ACA in water and methanol using high concentration NaOH solution is the first step. However, the β-lactam ring in D-7-ACA is prone to ring-opening reaction under strong alkaline condition, resulting in low yield. The D-7-ACA dissolution has low concentration and low efficiency in a traditional tank, due to the imprecise pH control and poor micro-mixing. Therefore, a new membrane dispersion microreactor was designed and used to dissolute D-7-ACA. Firstly, the degradation kinetics of D-7-ACA at different concentration, temperature and pH value were investigated. Then the effects of the pH, temperature, and circulation flow rate on the dissolution concentration were investigated carefully. The results showed that the concentration of the D-7-ACA solution is about 76.50 mg/ml, and the target product DCC yield is about 91.90% under the optimal conditions using membrane dispersion microreactor, which were increased by 5.91% and 5.61%, respectively, compared to using traditional reactor. The microreactor provides a good choice for industrially dissolving pH-sensitive drugs.

    Effect of different metal salt demulsifiers on vulcanization behavior of isobutylene isoprene rubber
    Xianxian RAO, Miao DU, Guorong SHAN, Pengju PAN
    2023, 74(2):  756-765.  doi:10.11949/0438-1157.20220998
    Abstract ( 173 )   HTML ( 9)   PDF (1588KB) ( 52 )  
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    In order to explore the effect of metal salt demulsifiers on the vulcanization behavior of isobutylene isoprene rubber (IIR), the vulcanization process of IIR demulsified by stirring and 11 metal salts was measured by a rheometer, and the vulcanization kinetics was analyzed. It was found that the cation and anion species of metal salts had significant effects on the vulcanization process. Compared with traditional Ca2+ coagulants, the demulsification of transition metal ions Cu2+ and Zn2+ can prolong the scorch period and positive vulcanization time, reduce the apparent activation energy of vulcanization, and the storage modulus of the vulcanized film is higher. The demulsification by using the main group metal ions Ca2+, Mg2+, Al3+ has little effect on the vulcanization process of IIR. Chloride ion and nitrate ion have significant vulcanization inhibition, reducing the apparent rate constant of vulcanization, and prolonging the positive vulcanization time. Sulfate ion and acetate ion have little effect on the vulcanization process of IIR, and the corresponding IIR vulcanizates have higher modulus.

    Study on preparation of Pd catalyst supported on carbon nitride for the selective hydrogenation of SBS
    Mengxin LIANG, Yan GUO, Shidong WANG, Hongwei ZHANG, Pei YUAN, Xiaojun BAO
    2023, 74(2):  766-775.  doi:10.11949/0438-1157.20221307
    Abstract ( 289 )   HTML ( 17)   PDF (2292KB) ( 180 )  
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    The selective catalytic hydrogenation of styrene-butadiene-styrene block copolymer (SBS) is to selectively hydrogenate the unsaturated CC in polybutadiene segment while maintaining the phenyl group in polystyrene segment intact so as to yield high-valued hydrogenated products SEBS with greatly improved performance. In order to eliminate the diffusion limitation, herein, three-dimensional ordered super-macroporous carbon nitride (3DOM g-C3N4) was successfully synthesized via thermal condensation of cyanamide with colloidal SiO2 sub-microspheres as the template. Afterwards, the Pd/3DOM g-C3N4 catalyst was obtained by chemical reduction method and applied for selective catalytic hydrogenation of SBS. The results showed that the Pd/3DOM g-C3N4 catalyst possessed a three-dimensional penetrating structure of super-macroporous-macroporous-mesoporous multistage pore with the small-sized and well-dispersed Pd nanoparticles over it. Such catalyst exhibited excellent hydrogenation activity and selectivity under mild reaction conditions. According to the Fourier transform infrared (FTIR) characterization, the total hydrogenation degree of 1,2-CC and 1,4-CC to SBS was 98%, while the benzene ring was not hydrogenated thus the selectivity to CC was 100%. The excellent catalytic performance is mainly attributed to the unique three-dimensional penetrating structure of super-macroporous-macroporous-mesoporous multistage pore of the support, which can effectively eliminate the macromolecules diffusion limitation in pores, thereby greatly improving the accessibility to the active sites. The strong interaction between Pd and pyridinic N in the g-C3N4 support is beneficial to anchoring Pd2+ during impregnation process, and then obtains Pd nanoparticles with small particle size and high dispersion and stability.

    Advantage of microreactor on the synthesis of high-activity Cu-Mn catalyst by co-precipitation
    Jiawei FU, Shuaishuai CHEN, Kailun FANG, Xin JIANG
    2023, 74(2):  776-783.  doi:10.11949/0438-1157.20221575
    Abstract ( 231 )   HTML ( 20)   PDF (1549KB) ( 92 )  
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    Cu-Mn coprecipitates with different copper manganese molar ratios were synthesised by co-precipitation method in the Caterpillar microreactor, and Cu-Mn composite oxide catalysts were prepared after calcining. The phase and structure of the precipitates and catalysts were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TG), Raman spectroscopy (Raman spectrum) and X-ray photoelectron spectroscopy (XPS). The results show that with the content of Cu increasing, the proportion of Mn3+ in the catalyst decreased gradually, the content of the surface lattice oxygen increased first and then decreased, and the catalytic performance of oxidation of toluene increased first and then decreased. The flow reaction characteristics of microreactor make Cu and Mn element in the catalyst maintain good dispersion, which contributes to increasing the content of Mn3+ in the catalyst. On the basis of high Mn3+ catalyst, the surface lattice oxygen becomes the dominating factor of catalytic performance.

    Separation engineering
    Modeling and simulation of CH4/N2 separation process with two absorption-adsorption columns using ZIF-8 slurry
    Xiaowan PENG, Xiaonan GUO, Chun DENG, Bei LIU, Changyu SUN, Guangjin CHEN
    2023, 74(2):  784-795.  doi:10.11949/0438-1157.20221488
    Abstract ( 228 )   HTML ( 14)   PDF (1525KB) ( 96 )  
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    Due to the unique flowability of ZIF-8 slurry, the traditional absorption-desorption process can be used for reference to realize the multi-stage continuous high-efficiency enrichment of methane in coalbed methane. In this paper, based on the single absorption-adsorption column process, a new process with two absorption-adsorption columns operated at high and low pressures is proposed aiming to reduce the energy consumption. The whole process modeling and simulation of the process was conducted. Using the equilibrium stage method, the mathematical model of each mass transfer unit in the process was established, including absorption-adsorption column, flash tank, and desorption column. Moreover, sensitivity analysis was carried out to explore the effects of equilibrium stages, feed stage, gas-slurry ratio, and desorption pressure on process performance, such as methane concentration in product gas and recovery ratio. The simulation results show that the recovery rate is 90.25% when the methane concentration reaches 90.13%(mol). In addition, the energy consumption per unit feed is 0.445 kW·h·m-3 (feed gas), which is lower than the energy consumption of the process with a single column (0.510 kW·h·m-3). The results show that compared with the single-column process, the improved double-column process can further reduce energy consumption while fulfilling the requirements of methane purity and recovery ratio.

    Process system engineering
    Synthesis of heat-integrated distillation sequences with intermediate heat exchangers
    Haiou YUAN, Fangjun YE, Shuo ZHANG, Yiqing LUO, Xigang YUAN
    2023, 74(2):  796-806.  doi:10.11949/0438-1157.20221352
    Abstract ( 170 )   HTML ( 14)   PDF (2075KB) ( 71 )  
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    This study addressed the synthesis problem of distillation sequences considering intermediate heat exchanger (IHE). Using the stochastic optimization strategy, a new method was proposed to synthesize heat-integrated distillation sequences with intermediate heat exchanger (IHE-HIDSs). The binary variables 0/1 are introduced to define whether the IHE is used in the corresponding merge point of two separation tasks in one distillation column. In this way, the synthesis problem is formulated as an implicit mixed-integer nonlinear programming (MINLP) problem, and could be solved by using the hybrid simulated annealing and particle-swarm optimization (SA-PSO) algorithm with the goal to minimize the total annual cost (TAC) of the distillation process. To illustrate the proposed method, two distillation sequence syntheses of five-component alcohols and five-component alkanes were investigated. The results show that IHE-HIDS has a lower TAC than the distillation sequence considering both thermal coupling and energy integration. In addition, the method proposed in this paper can obtain multiple separation sequence solutions with high probability in a reasonable computational time.

    Two-stage stochastic programming of steam power system based on Markov chain
    Kenian SHI, Jingyuan ZHENG, Yu QIAN, Siyu YANG
    2023, 74(2):  807-817.  doi:10.11949/0438-1157.20221430
    Abstract ( 126 )   HTML ( 5)   PDF (2794KB) ( 41 )  
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    The existing optimization methods to solve the uncertainty of steam demand in steam power system include stochastic programming and robust optimization. However, these methods can not trade off the stability and economy at the same time. This paper proposes a two-stage stochastic programming based on Markov chain to solve this problem. In the first stage, uncertain variables are divided based on spatial distance expression and divided into different working conditions by clustering algorithm. In the second stage, the Markov chain is constructed based on the state transition probability, and the demand value of steam is predicted by the method of scenario generation and reduction. The steam power system of a coal-to-gas enterprise is taken as an example to establish the corresponding optimization model, and the predicted steam value is brought into the optimization model to solve. The optimal operation scheme obtained is compared and analyzed with stochastic programming and robust optimization. The results show that the proposed optimization method combines the advantages of high economy of stochastic programming and high stability of robust optimization, both stability and economy are intermediate between stochastic programming and robust optimization, and provides a new idea for solving uncertain optimization problems of steam power system.

    Online optimization of gasoline blending considering carbon emissions
    Renchu HE, Zhaohui ZHANG, Minglei YANG, Cong WANG, Zhenhao XI
    2023, 74(2):  818-829.  doi:10.11949/0438-1157.20221022
    Abstract ( 243 )   HTML ( 12)   PDF (2336KB) ( 224 )  
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    According to the requirements of the national “two carbon” strategic objectives, taking the online optimization of gasoline blending in refining and chemical enterprises as the research object, this paper analyzes the characteristics of more controlled attributes, stricter requirements and higher blending efficiency under the new national Ⅵ gasoline standard, as well as the changes of carbon emissions of blended gasoline caused by the adjustment of blending components. Considering that the traditional online optimization of gasoline blending only considers the blending cost, quality and other objectives, this paper first establishes a nonlinear soft sensor model of gasoline blending octane number, vapor pressure and distillation range, and the goal of minimizing carbon dioxide emissions from blended refined oil was introduced into the optimization objective, and a gasoline blending optimization model incorporating carbon emission characteristics was developed. In order to meet the demand of online blending optimization, the actual cumulative blending process is considered in the optimization model. The qualified attributes of tank gasoline in blending process are transformed into qualified attributes of blending head. The optimized attributes of blending head are used to compensate the attribute deviation of blended volume and tank bottom oil. The simulation results show that the gasoline blending optimization technology considering carbon emission can well meet the demand of gasoline blending online optimization, and provide technical support for gasoline blending process design and online optimization control under the background of national Ⅵ standard and carbon trading.

    Energy and environmental engineering
    Qualitative and quantitative study on Pb2+ adsorption by biochar in solution
    Jiahao JIANG, Xiaole HUANG, Jiyun REN, Zhengrong ZHU, Lei DENG, Defu CHE
    2023, 74(2):  830-842.  doi:10.11949/0438-1157.20221299
    Abstract ( 158 )   HTML ( 14)   PDF (4296KB) ( 92 )  
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    Biochar produced by pyrolysis of lignocellulosic biomass can efficiently adsorb heavy metal ions in sewage, and it has broad application prospects as a Pb2+ adsorbent. In this paper, pine wood and soybean straw were applied as raw materials to prepare biochar at 400, 600, and 800℃, respectively. The relationship between physicochemical properties and adsorption performance of biochar was investigated, and the relative contributions of adsorption mechanisms were qualitatively and quantitatively analyzed. The results showed that the adsorption performance of soybean straw biochar (the adsorption capacity was 209.35, 180.62 and 226.64 mg·g-1 respectively) was much higher than that of pine wood biochar (4.62, 12.02 and 23.47 mg·g-1). The adsorption process of Pb2+ on the six biochars were all in accordance with the Langmuir model and the pseudo-second-order kinetic model, and was dominated by chemical adsorption, which was less affected by the microstructure. Cation exchange played an important role in the adsorption of Pb2+ by biochar, among which Ca2+ had the strongest exchange capacity. The precipitation of Pb2+ was mainly to form hydrocerussite and lead carbonate. With the increase of pyrolysis temperature, the content of organic functional groups and aromatic rings on the surface of biochar decreased. Mineral precipitation (relative contribution of 21.9%—76.8%) and cation exchange (18.1%—72.5%) were the main Pb2+ adsorption mechanisms of soybean straw biochar and pine wood biochar, followed by π-electron interaction and functional group complexation.

    Density functional theory study on thermal cracking reaction mechanism of phenolic resin
    Na ZHANG, Helin PAN, Bo NIU, Yayun ZHANG, Donghui LONG
    2023, 74(2):  843-860.  doi:10.11949/0438-1157.20221063
    Abstract ( 278 )   HTML ( 16)   PDF (5205KB) ( 193 )  
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    2,2'-Methylene diphenol was selected as the model compound of phenolic resin, and density functional theory (DFT) was used to predict the reaction trend from the perspective of atomic activity and chemical bond level, proposed the reaction path, and combined kinetic and thermodynamic analysis to determine the priority of each pathway and the mechanism of product formation. The results show that: due to the high activity of phenolic hydroxyl groups and methylene groups, the cracking of phenolic resin first occurs by dehydration condensation reaction. Methylene bridge cleavage is the main initial cracking reaction, mainly generating phenol and o-cresol. It is dissociated into OH, and the methylene group is oxidized by OH in the subsequent reaction, and phenol, CO and CO2 are generated by decarbonylation and carboxyl reaction. For the cracking process of boron-modified phenolic resin, the results show that the B—O bond in the boronate structure has low activity, is not easy to break, and has enhanced thermal stability. The methylene bridge is more stable and the tendency of decarbonylation and carboxyl group is obviously weakened, and the kinetic analysis shows that its energy barrier is increased, indicating that the introduction of boron can effectively improve its thermal stability and carbon residue rate.

    Effects of torrefaction with flue gas on grindability of corn stalk
    Shaozhuang WANG, Dunxi YU, Jiayi LI, Jingkun HAN, Xin YU, Fangqi LIU
    2023, 74(2):  861-870.  doi:10.11949/0438-1157.20221270
    Abstract ( 171 )   HTML ( 12)   PDF (2257KB) ( 124 )  
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    Grindability is one of the issues that must be considered in the large-scale combustion of biomass in existing coal-fired units. Corn stalk was torrefied in a fixed-bed reactor at various conditions. Aiming at biomass single burning and mixed burning with coal, the effects of torrefied atmosphere, temperature on the grindability of fuel were investigated via the mortar grinder, the automatic particle size sieving instrument, the cellulose analyzer, and the Fourier transform infrared spectroscopy. The results showed that compared with torrefaction with nitrogen atmosphere, torrefaction with flue gas atmosphere improved the grindability of corn stalk to be close to that of typical power coal at lower torrefied temperature. This is because the oxidizing components in the flue gas promote the decomposition of cellulose and hemicellulose. When co-grinding, the coal particles showed the role of grinding aid to improve the grindability of corn stalks. The grindability of mixed samples was approximately or even better than that of coal at higher temperatures or flue gas torrefaction condition.

    Material science and engineering, nanotechnology
    Study on curing phthalonitrile resin with novel poly(phthalazinone ether nitrile)
    Yue HU, Shoujun MA, Xigao JIAN, Zhihuan WENG
    2023, 74(2):  871-882.  doi:10.11949/0438-1157.20221229
    Abstract ( 213 )   HTML ( 12)   PDF (2946KB) ( 69 )  
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    A amino-terminated poly(phthalazinone ether nitrile) (A-PPEN) was prepared by a two-step one-pot method. It had better thermal stability than the commonly used aromatic diamine curing agent 4,4'- diaminodiphenylsulfoxide (DDS). The curing process of A-PPEN for resorcinole-based phthalonitrile resin precursor (DPPH) was studied by differential scanning calorimetry (DSC). The results showed that the curing system had the characteristics of autocatalytic curing, and the feeding ratio of A-PPEN would affect the curing activity of the system. In addition, the rheological properties and thermal stability of the curing system were studied. The results showed that the resin had a maximum 5% mass loss temperature (Td5%) of 552.9℃, a char yield (Cy800) of 78.6% at 800℃, and a minimum viscosity of 0.06 Pa·s. The resin had excellent thermal stability and a wide processing temperature window.

    Modification of unsaturated polyester resin by HTPB: effect of introducing method of the rubber
    Yajing ZHAO, Jijiang HU, Suyun JIE, Bo-Geng LI
    2023, 74(2):  883-892.  doi:10.11949/0438-1157.20221112
    Abstract ( 182 )   HTML ( 14)   PDF (1609KB) ( 45 )  
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    By using the co-curing method and copolycondensation method, three kinds of modified unsaturated polyester resin (UPR) with high cis-1,4 hydroxyl-terminated polybutadiene (HTPB) were prepared, which were blends of UPR and HTPB [UPR+HTPB (blend)], random copolycondensate of UPR and HTPB (UPR-HTPB), and block copolycondensate of UPR and HTPB (UPR-MAH-HTPB). Mechanical and physical properties of their curing products were investigated. It has been found that the elongation at break, the tensile strength and the impact strength of the three modified UPR are superior to those of the pure UPR, and their curing shrinkage are significantly reduced. The toughening and strengthening effects of UPR-HTPB and UPR-MAH-HTPB are more obvious than UPR+HTPB (blend). In addition, it is found that the tensile modulus of UPR-MAH-HTPB is superior to that of pure UPR, and the hardness and thermal deformation temperature are almost unchanged. It is shown by analyses of the impact section morphology, the crosslinking density and the dynamic mechanics that agglomeration of HTPB rubber is existed in the curing system of UPR+HTPB (blend), while microphase separation occurs in the curing system of modified UPR by copolycondensation, especial by block copolycondensation in which the HTPB units are inserted into the main chain of modified UPR, and more HTPB units participate in the crosslinking network. The modified UPRs by copolycondensation maintain their good rigidity and strength while being toughened.

    Pore network model of low-temperature nitrogen adsorption-desorption in mesoporous materials
    Jinlin MENG, Yu WANG, Qunfeng ZHANG, Guanghua YE, Xinggui ZHOU
    2023, 74(2):  893-903.  doi:10.11949/0438-1157.20221406
    Abstract ( 250 )   HTML ( 17)   PDF (4439KB) ( 95 )  
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    Characterization and analysis of mesoporous structure are essential for the development of mesoporous materials, and one of the most commonly used mesoporous characterization methods is low-temperature nitrogen adsorption-desorption. However, the current analytical model used in the nitrogen adsorption-desorption method is still based on the assumption of parallel pores, which cannot describe the pore blocking phenomenon during desorption and obtain important pore structural parameters such as pore connectivity. In this work, a pore network model for low-temperature nitrogen adsorption-desorption is developed, which can be used to analyze the effect of mesoporous structure on the isothermal adsorption-desorption behavior of nitrogen. By comparing experimental data and simulation results of nitrogen adsorption-desorption in alumina materials, the established pore network model is proved can well describe the low-temperature nitrogen adsorption-desorption behavior in mesoporous materials. The simulation results show that when the average pore size is small, the partial pressure of capillary condensation is low, the pore blocking effect of liquid nitrogen is significant, and thus the range and area of the hysteresis loop of nitrogen adsorption-desorption curve are larger; when the pore size distribution is wide, the numbers of both small and large pores are larger, the capillary condensation and pore blocking effects are significant, and thus the area of the hysteresis loop is larger. The pore connectivity does not affect the adsorption process, but significantly affects the desorption process by changing the pore blocking effect, and the worse the connectivity, the stronger the pore blocking effect. This work indicates that pore blocking should be accounted for in method of nitrogen adsorption-desorption as pore blocking importantly affects the adsorption process, and also provides a pore network model for mesoporous structure analysis.

    Regulation of structure and mechanical properties of poly(propylene-butene) alloys by monomer composition switching
    Shaojie ZHENG, Jianbin WANG, Jijiang HU, Bo-Geng LI, Wenbo YUAN, Zong WANG, Zhen YAO
    2023, 74(2):  904-915.  doi:10.11949/0438-1157.20221523
    Abstract ( 152 )   HTML ( 7)   PDF (2717KB) ( 46 )  
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    In order to solve the problem of low impact strength of polypropylene (PP) materials and utilize a large number of cheap 1-butene resources in China, the monomer composition switching method was used to carry out bulk homopolymerization of propylene and bulk copolymerization of propylene/butene in the reactor, and in situ preparation of polypropylene alloy. The obtained polypropylene alloys were mainly composed of propylene-butylene random copolymer, propylene-butylene block copolymer with long PP segments and high isotacticity polypropylene. As the rubber phase, the copolymer was dispersed in the polypropylene matrix to form a sea-island structure, which acted as the loci for stress concentration to induce and terminate crazes, and absorb impactive energy. The block copolymer with long PP segments increased the compatibility between the rubber phase and the matrix, resulting in the alloy material with balanced toughness and stiffness. The impact strength of the alloy was up to 48.91 kJ/m2. The influences of the polymerization conditions on the alloy composition were investigated. The relationship between the alloy composition, phase morphology and mechanical properties was revealed.

    Preparation and heat and salt resistance of AM/AMPS/SSS terpolymer
    Zhiyuan JIN, Guorong SHAN, Pengju PAN
    2023, 74(2):  916-923.  doi:10.11949/0438-1157.20221020
    Abstract ( 229 )   HTML ( 9)   PDF (999KB) ( 236 )  
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    China's oil fields have entered the stage of tertiary oil recovery. The development of oil displacement agents adapted to high temperature and high salt production environment has attracted extensive attention. In this paper, polyacrylamide, a traditional oil displacement agent, was modified, and acrylamide / 2-acrylamyl-2-methyl-1-propane sulfonic acid / sodium p-styrene sulfonate (AM/AMPS/SSS) terpolymer was prepared and optimized using aqueous solution polymerization. The effects of various reaction conditions on the apparent viscosity of the product aqueous solution were explored, and the optimum preparation conditions of terpolymer were obtained. The apparent viscosity, heat and salt resistance of terpolymer solution were studied by using rotary viscosimeter. Finally, AM/AMPS/SSS terpolymer with obvious heat and salt resistance and good thermal stability was obtained, which has a good application prospect in the current severe crude oil exploitation environment.

    Synthesis and curing kinetic analysis of eugenol-based siloxane epoxy resin
    Jieyuan ZHENG, Xianwei ZHANG, Jintao WAN, Hong FAN
    2023, 74(2):  924-932.  doi:10.11949/0438-1157.20221001
    Abstract ( 211 )   HTML ( 13)   PDF (1700KB) ( 146 )  
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    A novel eugenol-based siloxane epoxy resin (D4EUEP) was synthesized from eugenol glycidyl ether and tetramethyl-cyclotetrasiloxane. The molecular structure was characterized by 1H NMR and MALDI-TOF. The non-isothermal curing behavior of D4EUEP/33DDS system was characterized with differential scanning calorimetry (DSC), showing the relationship between temperature and heat rate. The isoconversional Šesták–Berggren model and Málek method were used to analyze the curing kinetics and established curing kinetic model. All the kinetic parameters were acquired and the explicit rate equations were constructed. The curing kinetic prediction was made in great coincidence with the experimental data. On the other hand, advanced isoconversional method (AICM) revealed the relationship between the conversion and activation energy and discussed the microscopic mechanisms during the curing process. Vyazovkin method was also used to predict the isothermal curing process in different temperature.

    Preparation of medium- and high-molecular-weight poly(glycolic acid) by melt/solid-state polycondensation
    Wangkai XIANG, Yuanyuan LIU, Ying ZHENG, Pengju PAN
    2023, 74(2):  933-940.  doi:10.11949/0438-1157.20221019
    Abstract ( 194 )   HTML ( 8)   PDF (1913KB) ( 234 )  
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    Poly(glycolic acid) (PGA) is usually prepared by ring-opening polymerization of glycolide and melt polycondensation of glycolic acid. However, the ring-opening polymerization process of glycolide is complicated, resulting in the high cost of PGA. In contrast, the preparation of PGA by melt polycondensation of glycolic acid has simple process and low cost, but it is difficult to obtain the medium- and high-molecular-weight PGA. In this work, the effects of polymerization process conditions such as catalyst type and content, esterification temperature and solid-state polycondensation temperature on the appearance, intrinsic viscosity and thermal stability of PGA were systematically studied in the melt/solid-state polycondensation route. It is found that bismuth trifluoromethanesulfonate had good catalytic effect on the melt polycondensation of glycolic acid. The optimal melt/solid-state polycondensation conditions were as follows: the catalyst content of 0.20%(mass), the esterification temperature of 180℃, the melt polycondensation and solid-state polycondensation temperatures of 210℃, and the solid-state polycondensation time of 12 h. Under such optimal melt polycondensation conditions, the highest intrinsic viscosity of PGA was 0.36 dl/g. The intrinsic viscosity of PGA can be increased to 0.59 dl/g by further solid-state polycondensation.

    Study on synthesis, adsorption and desorption performance of linear temperature-sensitive segment polymer regulated intelligent ReO4- ion-imprinted polymer
    Wan XU, Zhenbin CHEN, Huijuan ZHANG, Fangfang NIU, Ting HUO, Xingsheng LIU
    2023, 74(2):  941-952.  doi:10.11949/0438-1157.20221291
    Abstract ( 127 )   HTML ( 5)   PDF (1897KB) ( 43 )  
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    The linear temperature-sensitive polymer poly(N,N-dimethyl acrylamide) (PDEA) was firstly synthesized by reversible addition-fragmentation chain transfer (RAFT). Subsequently, it was introduced into the ion-imprinted polymer preparation system using acrylic acid (AA), acrylamide (AM), and N,N-diethylacrylamide (DEA) as functional monomers, ReO4- as template ion, N,N-methylenebisacrylamide (NMBA) as crosslinker, and a mixture of methanol and water (VmethanolVwater=3∶7) as solvent. After the self-assembly was completed, polymerization was initiated by Vc-H2O2 to prepare an intelligent ion-imprinted polymer ReO4--IIP with linear temperature-sensitive polymer block regulation. The structure and morphology of ReO4--IIP were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and the adsorption and separation performance of ReO4--IIP was evaluated by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results showed that ReO4--IIP was successfully prepared, the saturated adsorption capacity of ReO4--IIP was 0.1126 mmol/g, the desorption rate was 75%, and it had good selectivity in the binary mixed solution. After 7 adsorption/desorption cycles, ReO4--IIP still maintains good adsorption-desorption capacity, indicating that ReO4--IIP has great industrial application prospects.

    Process safety
    Influence of physical properties of working fluids on leakage and diffusion characteristics of refrigerant in limited space
    Peixu ZHOU, Yalun LI, Gongran YE, Yuan ZHUANG, Xilei WU, Zhikai GUO, Xiaohong HAN
    2023, 74(2):  953-967.  doi:10.11949/0438-1157.20221046
    Abstract ( 217 )   HTML ( 9)   PDF (4293KB) ( 68 )  
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    A new generation of environmentally friendly working fluids such as R290 and R32 will cause certain safety hazards if they leak due to their explosive characteristics, while the leakage of widely used working fluids such as R22 will also aggravate the greenhouse effect, thereby lead to deterioration of the global climate. Thus, it is necessary to study the leakage, diffusion and deposition of working fluid. In this paper, the numerical simulation of the leakage and diffusion process of working fluids with different physical properties is carried out. In the simulation, the Species component transport model is used to study the concentration of the working fluids under the leakage hole in the limited space, and the influence of the physical properties such as density and viscosity on the leakage and diffusion process. The results show that in the space under the leakage hole, density has a great influence on the concentration distribution of the working fluids, followed by viscosity. The higher the density, the greater the mass fraction of working fluid in the space under the leakage hole. The higher the viscosity, the worse the fluidity of the working fluid, and the greater the mass fraction in the space under the leakage hole. In the whole space, the greater the density of the working fluid, the easier it is to diffuse to the middle and lower part of the room and form a higher mass fraction. The greater the viscosity of the working fluid, the easier it is to entrain with the surrounding air.

    Inhibition effect of porous materials on hydrogen detonation
    Huanjuan ZHAO, Jing LIU, Donglei ZHOU, Min LIN
    2023, 74(2):  968-976.  doi:10.11949/0438-1157.20221400
    Abstract ( 229 )   HTML ( 13)   PDF (6535KB) ( 95 )  
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    In order to study the inhibition effect of porous materials on the detonation propagation of 2H2+O2+3Ar premixed gas, series of experiments were carried out in the detonation tube. The inner diameter of tube is 80 mm and the length is 6000 mm. 30 mm thick Al2O3 ceramics foam with different porosity (10, 20, 40 ppi), foam iron nickel metal with different thickness (10, 30, 50 mm) and porosity of 20 ppi were placed at a distance of 5000 mm from the ignition head. The pressure sensor and smoke film are used to record the detonation wave pressure and cell structure respectively, and the detonation wave propagation velocity is calculated. The results show that the velocity deficit and cell size increase with the increase of pore density or thickness. But both are inversely proportional to the initial pressure. The material properties of the two porous materials are different. The foam iron nickel metal has good thermal conductivity. So its inhibition effect on detonation wave is stronger than that of Al2O3 ceramic foam.