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Table of Content
28 May 2024, Volume 69 Issue 5
    Effect of carbon material and surfactant on ink property and resulting surface cracks of fuel-cell microporous layers
    Zhekun Chen, Weitong Pan, Longfei Tang, Xueli Chen, Fuchen Wang
    2024, 69(5):  1-12.  doi:10.1016/j.cjche.2024.01.023
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    Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer (MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene (PTFE) are not mutually soluble, resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.
    Hyperbranched polymer hollow-fiber-composite membranes for pervaporation separation of aromatic/aliphatic hydrocarbon mixtures
    Tong Liu, Hao Sun, Xiangqiong Wang, Jie Li, Zhanquan Zhang, Pei Wu, Naixin Wang, Quanfu An
    2024, 69(5):  13-22.  doi:10.1016/j.cjche.2024.01.009
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    The separation of aromatic/aliphatic hydrocarbon mixtures is crucial in the petrochemical industry. Pervaporation is regarded as a promising approach for the separation of aromatic compounds from alkanes. Developing membrane materials with efficient separation performance is still the main task since the membrane should provide chemical stability, high permeation flux, and selectivity. In this study, the hyperbranched polymer (HBP) was deposited on the outer surface of a polyvinylidene fluoride (PVDF) hollow-fiber ultrafiltration membrane by a facile dip-coating method. The dip-coating rate, HBP concentration, and thermal cross-linking temperature were regulated to optimize the membrane structure. The obtained HBP/PVDF hollow-fiber-composite membrane had a good separation performance for aromatic/aliphatic hydrocarbon mixtures. For the 50%/50% (mass) toluene/n-heptane mixture, the permeation flux of optimized composite membranes could reach 1766 g·m-2·h-1, with a separation factor of 4.1 at 60 ℃. Therefore, the HBP/PVDF hollow-fiber-composite membrane has great application prospects in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures.
    Enhancing capacitive deionization performance and cyclic stability of nitrogen-doped activated carbon by the electro-oxidation of anode materials
    Xiaona Liu, Baohua Zhao, Yanyun Hu, Luyue Huang, Jingxiang Ma, Shuqiao Xu, Zhonglin Xia, Xiaoying Ma, Shuangchen Ma
    2024, 69(5):  23-33.  doi:10.1016/j.cjche.2024.01.022
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    Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization (CDI) community. Understanding the causes of performance decay in traditional carbons is crucial to design a high-performance material. Based on this, here, nitrogen-doped activated carbon (NAC) was prepared by pyrolyzing the blend of activated carbon powder (ACP) and melamine for the positive electrode of asymmetric CDI. By comparing the indicators changes such as conductivity, salt adsorption capacity, pH, and charge efficiency of the symmetrical ACP-ACP device to the asymmetric ACP-NAC device under different CDI cycles, as well as the changes of the electrochemical properties of anode and cathode materials after long-term operation, the reasons for the decline of the stability of the CDI performance were revealed. It was found that the carboxyl functional groups generated by the electro-oxidation of anode carbon materials make the anode zero-charge potential (Epzc) shift positively, which results in the uneven distribution of potential windows of CDI units and affects the adsorption capacity. Furthermore, by understanding the electron density on C atoms surrounding the N atoms, we attribute the increased cyclic stability to the enhanced negativity of the charge of carbon atoms adjacent to quaternary-N and pyridinic-oxide-N.
    Synthesis of granulated Li1.33Mn1.67O4 via two antisolvent methods for lithium adsorption from gas-produced water
    Jun Qiu, Lu-Ri Bao, Wei Guo, Ying Yang, Shu-Ying Sun
    2024, 69(5):  34-46.  doi:10.1016/j.cjche.2024.01.013
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    Gas-produced water is an accompanying wastewater in the natural gas extraction process, and it is a potential liquid lithium resource that contains a considerable amount of lithium. This study investigated the feasibility of using manganese-based ion sieves to adsorb and extract lithium from gas-produced water. And we focused on the applicability of two different granulation methods, extrusion and droplet, in gas-produced water systems. Two types of H1.33Mn1.67O4 particles were prepared by the extrusion method (EHMO) and the droplet method (DHMO). The porosity of DHMO was much higher than that of EHMO, and the adsorption performance of DHMO increased with the decrease of binder concentration. DHMO prepared with a binder concentration of 0.14 g·ml-1 exhibited the best adsorption performance in gas-produced water, and the Li+ adsorption capacity could reach 25.14 mg·g-1. In gas-produced water, the adsorption equilibrium of DHMO only took 9 h, and the adsorption process conformed to the Langmuir model and pseudo-second-order kinetic model. The pore diffusion model (PDM) could well describe its adsorption process. Besides, DHMO showed a great selectivity to Li+, and the selectivity order of DHMO in gas-produced water was Li+>Ba2+≫Mg2+, Ca2+, Sr2+≫Na+≫K+. After 20 cycles, the Li+ adsorption capacity was still higher than 17.30 mg·g-1, and the rate of manganese dissolution was less than 1%.
    A gel polymer electrolyte based on IL@NH2-MIL-53 (Al) for high-performance all-solid-state lithium metal batteries
    Sijia Wang, Ye Liu, Liang He, Yu Sun, Qing Huang, Shoudong Xu, Xiangyun Qiu, Tao Wei
    2024, 69(5):  47-55.  doi:10.1016/j.cjche.2024.01.017
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    Solid polymer composite electrolytes possess the benefits of superior compatibility with electrodes and good thermal characteristics for more secure energy storage equipment. Herein, a new gel polymer electrolyte (GPE) containing NH2-MIL-53(Al), [PP13][TFSI], LiTFSI, and PVDF-HFP was prepared using a simple method of solution casting. The effects of encapsulating different ratios of ionic liquid ([PP13][TFSI]) into the micropores of functionalized metal-organic frameworks (NH2-MIL-53(Al)) on the electrochemical properties were compared. XRD, SEM, nitrogen adsorption-desorption isotherms, and electrochemical measurements were conducted. This GPE demonstrates a superior ionic conductivity of 8.08×10-4 S·cm-1 at 60 ℃ and can sustain a discharge specific capacity of 156.6 mA·h·g-1 at 0.2 C for over 100 cycles. This work might offer a potential approach to alleviate the solid-solid contact with the solid-state electrolyte and electrodes and broaden a new window for the creation of all-solid-state batteries.
    Aggregation-regulated bioreduction process of graphene oxide by Shewanella bacteria
    Kaixin Han, Yibo Zeng, Yinghua Lu, Ping Zeng, Liang Shen
    2024, 69(5):  56-62.  doi:10.1016/j.cjche.2024.01.008
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    The bioreduction of graphene oxide (GO) using environmentally functional bacteria such as Shewanella represents a green approach to produce reduced graphene oxide (rGO). This process differs from the chemical reduction that involves instantaneous molecular reactions. In bioreduction, the contact of bacterial cells and GO is considered the rate-limiting step. To reveal how the bacteria-GO integration regulates rGO production, the comparative experiments of GO and three Shewanella strains were carried out. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and atomic force microscopy were used to characterize the reduction degree and the aggregation degree. The results showed that a spontaneous aggregation of GO and Shewanella into the condensed entity occurred within 36 h. A positive linear correlation was established, linking three indexes of the aggregation potential, the bacterial reduction ability, and the reduction degree (ID/IG) comprehensively.
    Combining reinforcement learning with mathematical programming: An approach for optimal design of heat exchanger networks
    Hui Tan, Xiaodong Hong, Zuwei Liao, Jingyuan Sun, Yao Yang, Jingdai Wang, Yongrong Yang
    2024, 69(5):  63-71.  doi:10.1016/j.cjche.2023.12.005
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    Heat integration is important for energy-saving in the process industry. It is linked to the persistently challenging task of optimal design of heat exchanger networks (HEN). Due to the inherent highly nonconvex nonlinear and combinatorial nature of the HEN problem, it is not easy to find solutions of high quality for large-scale problems. The reinforcement learning (RL) method, which learns strategies through ongoing exploration and exploitation, reveals advantages in such area. However, due to the complexity of the HEN design problem, the RL method for HEN should be dedicated and designed. A hybrid strategy combining RL with mathematical programming is proposed to take better advantage of both methods. An insightful state representation of the HEN structure as well as a customized reward function is introduced. A Q-learning algorithm is applied to update the HEN structure using the ϵ-greedy strategy. Better results are obtained from three literature cases of different scales.
    Facile molybdenum and aluminum recovery from spent hydrogenation catalyst
    Zhenhui Lv, Jianan Li, Dong Xue, Tao Yang, Gang Wang, Chong Peng
    2024, 69(5):  72-78.  doi:10.1016/j.cjche.2024.01.006
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    Industrial catalyst waste has emerged as a hazardous pollutant that requires safe and proper disposal after the unloading process. Finding a valuable and sustainable strategy for its treatment is a significant challenge compared to traditional methods. In this study, we present a facile method for the recovery of molybdenum and aluminum contents from spent Mo-Ni/Al2O3 hydrogenation catalysts through crystallization separation and coprecipitation. Furthermore, the recovered molybdenum and aluminum are utilized as active metals and carriers for the preparation of new catalysts. Their properties were thoroughly analyzed and investigated using various characterization techniques. The hydrogenation activity of these newly prepared catalysts was evaluated on a fixed-bed small-scale device and compared with a reference catalyst synthesized from commercial raw reagents. Finally, the hydrogenation activity of the catalysts was further assessed by using the entire distillate oil of coal liquefaction as the raw oil, specifically focusing on denitrogenation and aromatic saturation. This work not only offers an effective solution for recycling catalysts but also promotes sustainable development.
    Molecular simulation study on the evolution process of hydrate residual structures into hydrate
    Liwei Cheng, Yunfei Li, Jinlong Cui, Huibo Qin, Fulong Ning, Bei Liu, Guangjin Chen
    2024, 69(5):  79-91.  doi:10.1016/j.cjche.2023.12.023
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    The clathrate hydrate memory effect is a fascinating phenomenon with potential applications in carbon capture, utilization and storage (CCUS), gas separation, and gas storage as it can accelerate the secondary formation of clathrate hydrate. However, the underlying mechanism of this effect remains unclear. To gain a better understanding of the mechanism, we conducted molecular dynamic simulations to simulate the initial formation and reformation processes of methane hydrate. In this work, we showed the evolution process of hydrate residual structures into hydrate cages. The simulation results indicate that the residual structures are closely related to the existence of hydrate memory effect, and the higher the contribution of hydrate dissociated water to the hydrate nucleation process, the faster the hydrate nucleation. After hydrate dissociation, the locally ordered structures still exist after hydrate dissociation and can promote the formation of cluster structures, thus accelerating hydrate nucleation. Additionally, the nucleation process of hydrate and the formation process of clusters are inseparable. The size of clusters composed of cup-cage structures is critical for hydrate nucleation. The residence time at high temperature after hydrate decomposition will affect the strength of the hydrate memory effect. Our simulation results provide microscopic insights into the occurrence of the hydrate memory effect and shed light on the hydrate reformation process at the molecular scale.
    Enhanced photocatalytic nitrogen fixation performance via in situ constructing BiO2-x/NaNbO3 heterojunction
    Jiayu Zhang, Zhihao Zeng, Lin Yue, Chunran Zhao, Xin Hu, Leihong Zhao, Xiuwen Wang, Yiming He
    2024, 69(5):  92-100.  doi:10.1016/j.cjche.2024.02.003
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    The fabrication of heterojunction catalysts is an effective strategy to enhance charge separation efficiency, thereby boosting the performance of photocatalysts. In this study, BiO2-x nanosheets were synthesized through a hydrothermal process and loaded onto NaNbO3 microcube to construct a series of BiO2-x/NaNbO3 heterojunctions for photocatalytic N2 fixation. Results indicated that 2.5% BiO2-x/NaNbO3 had the highest photocatalytic performance. The NH3 production rate under simulated solar light reached 406.4 μmol·L-1·g-1·h-1, which reaches 2.6 and 3.8 times that of NaNbO3 and BiO2-x, respectively. BiO2-x nanosheets primarily act as electron trappers to enhance the separation efficiency of charge carriers. The strong interaction between BiO2-x and NaNbO3 facilitates the electron migration between them. Meanwhile, the abundant oxygen vacancies in BiO2-x nanosheets may facilitate the adsorption and activation of N2, which may be another possible reason of the high photocatalytic activity of the BiO2-x/NaNbO3. This study may offer new insights for the development of semiconductor materials in photocatalytic nitrogen fixation.
    Phosphotungstic acid ionic liquid for efficient photocatalytic desulfurization: Synthesis, application and mechanism
    Chenchao Hu, Suhang Xun, Desheng Liu, Junjie Zhang, Minqiang He, Wei Jiang, Huaming Li, Wenshuai Zhu
    2024, 69(5):  101-111.  doi:10.1016/j.cjche.2024.02.002
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    An efficient mass transfer process is a critical factor for regulating catalytic activity in a photocatalytic desulfurization system. Herein, a phosphotungstic acid (HPW) active center is successfully composited with a quaternary ammonium phosphotungstate-based hexadecyltrimethylammonium chloride ionic liquid (CTAC-HPW) by the ion exchange method for the photocatalytic oxidative desulfurization of dibenzothiophene sulfide. The keggin structure of HPW and highly mass transfer performance of organic cations synergistically enhanced the photocatalytic activity towards the effective convertion of dibenzothiophene (DBT) with the excitation of visible light. The deep desulfurization (<10 mg·kg-1) is attained within 30 min, and well stability is demonstrated within 25 cycles. Moreover, the CTAC-HPW photocatalyst projects well selectivity to interference from coexisting compounds such as olefins and aromatic hydrocarbons and universality of dibenzothiophenes, for example, 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Ultimately, a possible photocatalytic desulfurization mechanism is proposed according to the Gaschromatography-mass spectrometry (GC-MS), proving that the final product is the corresponding sulfone. The trapping experiment and electron spin resonance (ESR) analysis confirmed that h+ and ·COOH played critical roles in the oxidation process. The work offers a practicable strategy for efficiently converting DBT to DBTO2 with added value.
    Removal of rubidium from brine by an integrated film of sulfonated polysulfone/graphene/potassium copper ferricyanide
    Huanxi Xu, Peihua Lin, Pei-Jun Liu, Hai-Gang Liu, Hui-Bin Guo, Chao-Xiang Wu, Ming Fang, Xu Zhang, Guan-Ping Jin
    2024, 69(5):  112-121.  doi:10.1016/j.cjche.2023.11.028
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    A novel integrated film of sulfonated polysulfone/graphene/potassium copper ferricyanide (KCuFC/SPSG) was used for selectively extracting rubidium ion (Rb+) from brine. To form KCuFC/SPSG, the precursor film of sulfonated polysulfone/graphene (SPSG) was synthesized by phase conversion process, which was alternately immersed in 0.1 mol·L-1 CuSO4/K4[Fe(CN)6] by in-situ adsorption coupled co-precipitation method. Various data such as nuclear magnetic resonance spectrometer, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, X-ray diffraction, scanning electron microscope, and energy dispersive spectroscopy all verified that abundant KCuFC were uniformly located on the film. The resulting KCuFC/SPSG was used in film separation system. As the solution was fed into the system, the Rb+ could be selectively adsorption by KCuFC/SPSG. After the saturation adsorption, 0.5 mol·L-1 NH4Cl/HCl was fed into the film cell, Rb+ could be quickly desorbed by ion-exchange between Rb+ and NH4+ in the lattice of KCuFC. The purpose of separating and recovering Rb+ from the brine can be achieved after the repeated operation. The effects of pH, adsorption time, and interferential ions on the adsorption capacity of Rb+ were investigated by batch experiments. The adsorption behavior fits the pseudo-second order kinetic process, while KCuFC has a higher adsorption capacity (Langmuir maximum sorption 165.4 mg·g-1). In addition, KCuFC/SPSG shows excellent selectivity for Rb+ even in complex brine systems. KCuFC/SPSG could maintain 93.5% extraction efficiency after five adsorption/desorption cycles.
    A strategy for strengthening chaotic mixing of dual shaft eccentric mixers by changing non-Newtonian fluids kinetic energy distribution
    Songsong Wang, Tong Meng, Qian Zhang, Changyuan Tao, Yundong Wang, Zequan Li, Zuohua Liu
    2024, 69(5):  122-134.  doi:10.1016/j.cjche.2024.01.016
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    Efficiently modulating the velocity distribution and flow pattern of non-Newtonian fluids is a critical challenge in the context of dual shaft eccentric mixers for process intensification, posing a significant barrier for the existing technologies. Accordingly, this work reports a convenient strategy that changes the kinetic energy to controllably regulate the flow patterns from radial flow to axial flow. Results showed that the desired velocity distribution and flow patterns could be effectively obtained by varying the number and structure of baffles to change kinetic energy, and a more uniform velocity distribution, which could not be reached normally in standard baffle dual shaft mixers, was easily obtained. Furthermore, a comparative analysis of velocity and shear rate distributions is employed to elucidate the mechanism behind the generation of flow patterns in various dual-shaft eccentric mixers. Importantly, there is little difference in the power number of the laminar flow at the same Reynolds number, meaning that the baffle type has no effect on the power consumption, while the power number of both unbaffle and U-shaped baffle mixing systems decreases compared with the standard baffle mixing system in the transition flow. Finally, at the same rotational condition, the dimensionless mixing time of the U-shaped baffle mixing system is 15.3% and 7.9% shorter than that of the standard baffle and the unbaffle mixing system, respectively, which shows the advantage of the U-shaped baffle in stirring rate.
    Effect of solvent on the initiation mechanism of living anionic polymerization of styrene: A computational study
    Shen Li, Yin-Ning Zhou, Zhong-Xin Liu, Zheng-Hong Luo
    2024, 69(5):  135-142.  doi:10.1016/j.cjche.2024.01.007
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    For living anionic polymerization (LAP), solvent has a great influence on both reaction mechanism and kinetics. In this work, by using the classical butyl lithium-styrene polymerization as a model system, the effect of solvent on the mechanism and kinetics of LAP was revealed through a strategy combining density functional theory (DFT) calculations and kinetic modeling. In terms of mechanism, it is found that the stronger the solvent polarity, the more electrons transfer from initiator to solvent through detailed energy decomposition analysis of electrostatic interactions between initiator and solvent molecules. Furthermore, we also found that the stronger the solvent polarity, the higher the monomer initiation energy barrier and the smaller the initiation rate coefficient. Counterintuitively, initiation is more favorable at lower temperatures based on the calculated results of ∆GTS. Finally, the kinetic characteristics in different solvents were further examined by kinetic modeling. It is found that in benzene and n-pentane, the polymerization rate exhibits first-order kinetics. While, slow initiation and fast propagation were observed in tetrahydrofuran (THF) due to the slow free ion formation rate, leading to a deviation from first-order kinetics.
    Deep decalcification of factory-provided freezing acidolysis solution to achieve α-high-strength gypsum
    Wencai Ye, Yulu Li, Yonggang Dong, Lin Yang, Yun Yi, Jianxin Cao
    2024, 69(5):  143-151.  doi:10.1016/j.cjche.2024.01.015
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    The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content, which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products. Here, based on the potential crystallization principle of calcium sulfate in NH4NO3-H3PO4-H2O, the deep decalcification (i.e. calcium removal) technology to achieve α-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated. Typically, calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia, followed by the addition of ammonium sulfate solution. As a result, the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO4·2H2O (DH), as well as its dissolution and crystallization into short columnar α-CaSO4·0.5H2O (α-HH). Remarkably, with the molar ratio of SO42-/Ca2+ at 1.8, the degree of neutralization (NH3/HNO3 molar ratio) at 1.7, the reaction temperature of 94 ℃, and the reaction time of 300 min, the decalcification rate can reach 86.89%, of which the high-strength α-CaSO4·0.5H2O (α-HH) will be obtained. Noteworthy, the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers. Consequently, the 2 h flexural strength of α-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa, which is up to the standard of commercial α-HH.
    Data-driven Wasserstein distributionally robust chance-constrained optimization for crude oil scheduling under uncertainty
    Xin Dai, Liang Zhao, Renchu He, Wenli Du, Weimin Zhong, Zhi Li, Feng Qian
    2024, 69(5):  152-166.  doi:10.1016/j.cjche.2023.12.007
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    Crude oil scheduling optimization is an effective method to enhance the economic benefits of oil refining. But uncertainties, including uncertain demands of crude distillation units (CDUs), might make the production plans made by the traditional deterministic optimization models infeasible. A data-driven Wasserstein distributionally robust chance-constrained (WDRCC) optimization approach is proposed in this paper to deal with demand uncertainty in crude oil scheduling. First, a new deterministic crude oil scheduling optimization model is developed as the basis of this approach. The Wasserstein distance is then used to build ambiguity sets from historical data to describe the possible realizations of probability distributions of uncertain demands. A cross-validation method is advanced to choose suitable radii for these ambiguity sets. The deterministic model is reformulated as a WDRCC optimization model for crude oil scheduling to guarantee the demand constraints hold with a desired high probability even in the worst situation in ambiguity sets. The proposed WDRCC model is transferred into an equivalent conditional value-at-risk representation and further derived as a mixed-integer nonlinear programming counterpart. Industrial case studies from a real-world refinery are conducted to show the effectiveness of the proposed method. Out-of-sample tests demonstrate that the solution of the WDRCC model is more robust than those of the deterministic model and the chance-constrained model.
    Particle residence time distribution and axial dispersion coefficient in a pressurized circulating fluidized bed by using multiphase particle-in-cell simulation
    Jinnan Guo, Daoyin Liu, Jiliang Ma, Cai Liang, Xiaoping Chen
    2024, 69(5):  167-176.  doi:10.1016/j.cjche.2024.01.020
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    The particle residence time distribution (RTD) and axial dispersion coefficient are key parameters for the design and operation of a pressurized circulating fluidized bed (PCFB). In this study, the effects of pressure (0.1-0.6 MPa), fluidizing gas velocity (2-7 m·s-1), and solid circulation rate (10-90 kg·m-2·s-1) on particle RTD and axial dispersion coefficient in a PCFB are numerically investigated based on the multiphase particle-in-cell (MP-PIC) method. The details of the gas-solid flow behaviors of PCFB are revealed. Based on the gas-solid flow pattern, the particles tend to move more orderly under elevated pressures. With an increase in either fluidizing gas velocity or solid circulation rate, the mean residence time of particles decreases while the axial dispersion coefficient increases. With an increase in pressure, the core-annulus flow is strengthened, which leads to a wider shape of the particle RTD curve and a larger mean particle residence time. The back-mixing of particles increases with increasing pressure, resulting in an increase in the axial dispersion coefficient.
    Application of different fiber structures and arrangements by electrospinning in triboelectric nanogenerators
    Hebin Li, Zifei Meng, Dehua Wang, Ye Lu, Longlong Jiang, Le Zhang, Hanbin Wang, Xiaoxiong Wang
    2024, 69(5):  177-191.  doi:10.1016/j.cjche.2023.09.017
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    In recent years, nanogenerators (NGs) have attracted wide attention in the energy field, among which triboelectric nanogenerators (TENGs) have shown superior performance. Multiple reports of electrospinning (ES)-based TENGs have been reported, but there is a lack of deep analysis of the designing method from microstructure, limiting the creative of new ES-based TENGs. Most TENGs use polymer materials to achieve corresponding design, which requires structural design of polymer materials. The existing polymer molding design methods include macroscopic molding methods, such as injection, compression, extrusion, calendering, etc., combined with liquid-solid changes such as soluting and melting; it also includes micro-nano molding technology, such as melt-blown method, coagulation bath method, ES method, and nanoimprint method. In fact, ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation. At present, these characteristics have not been reviewed. Therefore, in this paper, we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method. Based on the rich microstructure research results in the field of ES, much more new types of TENGs can be designed in the future.
    Efficient adsorption separation of methane from C2-C3 hydrocarbons in a Co(II)-nodes metal-organic framework
    Jie Zhang, Xingzhe Guo, Bing Lin, Guangzu Xiong, Hanshuang Wang, Min Zhang, Liwen Fan, Bingwen Li, Shuisheng Chen
    2024, 69(5):  192-198.  doi:10.1016/j.cjche.2024.02.001
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    Methane (CH4) as a substitute for other mineral fuels plays a crucial role in reducing energy consumption and preventing environmental pollution. The present study employs a solvothermal method to fabricate a porous framework Co-metal-organic framework (Co-MOF) containing two distinct secondary building units (SBUs): an anionic [Co22-OH)(COO)4(H2O)] and a neutral [CoN2(COO)2]. Notably, within the anionic SBUs, the coordinated water molecules induce the generation of divergent unsaturated Co(II) centers in the unidirectional porous channels, thereby creating open metal sites. The adsorption performance of Co-MOF towards pure component gases was systematically investigated. The results demonstrated that Co-MOF exhibits superior adsorption capacity for C2-C3 hydrocarbons compared to CH4, which offers the potential for efficient adsorption and separation of CH4 from C2-C3 hydrocarbons. The gas selectivity separation ratios of Co-MOF for C2H6/CH4 and C3H8/CH4 were calculated using the ideal adsorbed solution theory method at 273/298 K and 0.1 MPa. The results revealed that Co-MOF achieved remarkable equilibrium separation selectivity for CH4 and C2-C3 hydrocarbon gases among non-modified MOFs, signifying the potential of the synthesized Co-MOF for efficient recovery and purification of CH4 from C2-C3 hydrocarbons. Breakthrough experiments further demonstrate the ability of Co-MOF to purify methane from C2-C3 hydrocarbons in practical gas separation scenarios. Additionally, molecular simulation calculations further substantiate the propensity of anionic SBUs to interact with C2-C3 hydrocarbon compounds. This study provides a novel paradigm for the development of porous MOF materials in the application of gas mixture separation.
    MXene: Promising materials for magnesium-ion batteries
    Liuyu Song, Haibo Li, Pengkai Wang, Yu Shang, Yue Yang, Zhaoyu Wu
    2024, 69(5):  199-211.  doi:10.1016/j.cjche.2024.01.018
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    Magnesium-ion batteries (MIBs) have attracted extensive attention due to their high theoretical capacity, superior safety, and low cost. Nonetheless, the development of MIBs is hindered by the lack of cathode materials with long cycle life and rate capability. MXene stands out as a prime choice for MIB cathode or collector for anode-free magnesium batteries (AFMBs) because of its larger surface area, adjustable surface properties, and good electrical conductivity. In this paper, we summarized the preparation and layering methods of MXene and discussed the prospects of MXene as a cathode or collector for MIBs. This review will be immensely beneficial in critically analyzing the synthesis techniques and the applications of MXene material as MIB cathode or AFMB collector. In addition, the challenges of the preparation and layering were concluded, along with raising the research strategies of MXene for storing Mg ions.
    Simultaneous purification of minor components in natural products using twin-column recycling chromatography with a step solvent gradient
    Guangxia Jin, Yuxue Wu, Feng Wei
    2024, 69(5):  212-219.  doi:10.1016/j.cjche.2024.02.004
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    The isolation of minor components from complex natural product matrices presents a significant challenge in the field of purification science due to their low concentrations and the presence of structurally similar compounds. This study introduces an optimized twin-column recycling chromatography method for the efficient and simultaneous purification of these elusive constituents. By introducing water at a small flowing rate between the twin columns, a step solvent gradient is created, by which the leading edge of concentration band would migrate at a slower rate than the trailing edge as it flowing from the upstream to downstream column. Hence, the band broadening is counterbalanced, resulting in an enrichment effect for those minor components in separation process. Herein, two target substances, which showed similar peak position in high performance liquid chromatography (HPLC) and did not exceed 1.8% in crude paclitaxel were selected as target compounds for separation. By using the twin-column recycling chromatography with a step solvent gradient, a successful purification was achieved in getting the two with the purity almost 100%. We suggest this method is suitable for the separation of most components in natural produces, which shows higher precision and recovery rate compared with the common lab-operated separation ways for natural products (thin-layer chromatography and prep-HPLC).
    Supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions
    Xinyue Duan, Zeyu Zhang, Ziyuan Zhao, Yang Liu, Liang Gong, Xuewen Cao, Jiang Bian
    2024, 69(5):  220-226.  doi:10.1016/j.cjche.2023.12.024
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    This paper introduced supersonic expansion liquefaction technology into the field of hydrogen liquefaction. The mathematical model for supersonic condensation of hydrogen gas in a Laval nozzle model was established. The supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions were investigated. The simulation results show that the droplet number rises rapidly from 0 at the nozzle throat as the inlet temperature increases, and the maximum droplet number generated is 1.339×1018 kg-1 at inlet temperature of 36.0 K. When hydrogen nucleation occurs, the droplet radius increases significantly and shows a positive correlation with the increase in the inlet temperature, and the maximum droplet radii are 6.667×10-8 m, 1.043×10-7 m, and 1.099×10-7 m when the inlet temperature is 36.0 K, 36.5 K, and 37.0 K, respectively. The maximum nucleation rate decreases with increasing inlet temperature, and the nucleation region of the Laval nozzle becomes wider. The liquefaction efficiency can be effectively improved by lowering the inlet temperature. This is because a lower inlet temperature provides more subcooling, which allows the hydrogen to reach the thermodynamic conditions required for large-scale condensation more quickly.
    Thermal pretreatment of willow branches impacts yield and pore development of activated carbon in subsequent activation with ZnCl2 via modifying cellulose structure
    Linghui Kong, Chao Li, Runxing Sun, Shu Zhang, Yi Wang, Jun Xiang, Song Hu, Dong Wang, Chuanjun Leng, Xun Hu
    2024, 69(5):  227-237.  doi:10.1016/j.cjche.2024.01.014
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    Development of pore structures of activated carbon (AC) from activation of biomass with ZnCl2 relies on content and structure of cellulose/hemicellulose in the feedstock. Thermal pretreatment of biomass could induce dehydration and/or aromatization to change the structure of cellulose/hemicellulose. This might interfere with evolution of structures of AC, which was investigated herein via thermal pretreatment of willow branch (WB) from 200 to 360 ℃ and the subsequent activation with ZnCl2 at 550 ℃. The results showed that thermal pretreatment at 360 ℃ (WB-360) could lead to substantial pyrolysis to form biochar, with a yield of 31.9%, accompanying with nearly complete destruction of cellulose crystals and remarkably enhanced aromatic degree. However, cellulose residual in WB-360 could still be activated to form AC-360 with specific surface area of 1837.9 m2·g-1, which was lower than that in AC from activation of untreated WB (AC-blank, 2077.8 m2·g-1). Nonetheless, the AC-200 from activation of WB-200 had more developed pores (2113.9 m2·g-1) and superior capability for adsorption of phenol, due to increased permeability of ZnCl2 to the largely intact cellulose structure in WB-200. The thermal pretreatment did increase diameters of micropores of AC but reduced the overall yield of AC (26.8% for AC-blank versus 18.0% for AC-360), resulting from accelerated cracking but reduced intensity of condensation. In-situ infrared characterization of the activation showed that ZnCl2 mainly catalyzed dehydration, dehydrogenation, condensation, and aromatization but not cracking, suppressing the formation of derivatives of cellulose and lignin in bio-oil. The thermal pretreatment formed phenolic -OH and CO with higher chemical innerness, which changed the reaction network in activation, shifting morphology of fibrous structures in AC-blank to “melting surface” in AC-200 or AC-280.
    Solubility determination and comparison of β-HMX and RDX in two binary mixed solvents (acetonitrile + water, nitric acid + water)
    Yuehua Yao, Fan Wang, Yinguang Xu, Zishuai Xu, Lizhen Chen, Jianlong Wang
    2024, 69(5):  238-249.  doi:10.1016/j.cjche.2023.12.016
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    In order to remove hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), the main impurity, in process of polymorphic transformation of octrahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the solubility of β-HMX and RDX in acetonitrile (ACN) + water in the temperature range of 288.15-333.15 K and in nitric acid (HNO3) + water in the temperature range of 298.15-333.15 K were measured by laser dynamic method. The results showed that the solubility of both β-HMX and RDX in binary mixed solvents increased monotonously as the temperature increase at a given solvent composition or with increasing of mole fraction of solvent (ACN and nitric acid). Solubility data were well correlated by the modified Apelblat equation, Jouyban-Acree model, Yaws equation and van't Hoff equation, and the Yaws equation achieved the best fitting results according to the relative error and the mean square error root. Furthermore, the solubility of β-HMX and RDX in binary mixed solvent was compared, based on the solubility difference and the solvent's own properties, the best separation degree of β-HMX and RDX was found when the mole fraction of nitric acid was 0.22 at room temperature, which provided data support for HMX crystallization in mixed solvent. The solubility differences between RDX and β-HMX in mixed solvents were explained from the formation of intermolecular and intramolecular hydrogen bonds.
    Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells
    Guodong Xia, Xiaoya Zhang, Dandan Ma
    2024, 69(5):  250-262.  doi:10.1016/j.cjche.2024.01.010
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    This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels: a smooth channel (Case 1); eight rectangular baffles were arranged in the upstream (Case 2), midstream (Case 3), downstream (Case 4), and the entire cathode flow channel (Case 5) to study the effects of baffle position on mass transport, power density, net power, etc. Moreover, the effects of back pressure and humidity on the voltage were investigated. Results showed that compared to smooth channels, the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60% and 7.81%-9.80% at 1.68 A·cm-2 by adding baffles. The closer the baffles were to upstream, the higher the total oxygen flux, but the lower the flux uniformity the worse the water removal. The oxygen flux of upstream baffles was 8.14% higher than that of downstream baffles, but oxygen flux uniformity decreased by 18.96% at 1.68 A·cm-2. The order of water removal and voltage improvement was Case 4 > Case 5 > Case 3 > Case 2 > Case 1. Net power of Case 4 was 9.87% higher than that of the smooth channel. To the Case 4, when the cell worked under low back pressure or high humidity, the voltage increments were higher. The potential increment for the back pressure of 0 atm was 0.9% higher than that of 2 atm (1 atm = 101.325 kPa). The potential increment for the humidity of 100% was 7.89% higher than that of 50%.
    Process synthesis for the separation of coal-to-ethanol products
    Qingping Qu, Daoyan Liu, Hao Lyu, Jinsheng Sun
    2024, 69(5):  263-278.  doi:10.1016/j.cjche.2023.12.019
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    The coal-to-ethanol process, as the clean coal utilization, faces challenges from the energy-intensive distillation that separates multi-component effluents for pure ethanol. Referring to at least eight columns, the synthesis of the ethanol distillation system is impracticable for exhaustive comparison and difficult for conventional superstructure-based optimization as rigorous models are used. This work adopts a superstructure-based framework, which combines the strategy that adaptively selects branches of the state-equipment network and the parallel stochastic algorithm for process synthesis. High-performance computing significantly reduces time consumption, and the adaptive strategy substantially lowers the complexity of the superstructure model. Moreover, parallel computing, elite search, population redistribution, and retention strategies for irrelevant parameters are used to improve the optimization efficiency further. The optimization terminates after 3000 generations, providing a flowsheet solution that applies two non-sharp splitting options in its distillation sequence. As a result, the 59-dimension superstructure-based optimization was solved efficiently via a differential evolution algorithm, and a high-quality solution with a 28.34% lower total annual cost than the benchmark was obtained. Meanwhile, the solution of the superstructure-based optimization is comparable to that obtained by optimizing a single specific configuration one by one. It indicates that the superstructure-based optimization that combines the adaptive strategy can be a promising approach to handling the process synthesis of large-scale and complex chemical processes.