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Table of Content
25 September 2023, Volume 74 Issue 9
    Ionic Liquids and Green Processes
    Research progress on homogeneous processing of cellulose in ionic liquids
    Ruimin CHE, Wenqiu ZHENG, Xiaoyu WANG, Xin LI, Feng XU
    2023, 74(9):  3615-3627.  doi:10.11949/0438-1157.20230529
    Abstract ( 448 )   HTML ( 73)   PDF (3441KB) ( 375 )  
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    Cellulose is the most abundant renewable resource in nature and an ideal material for the preparation of economically sustainable polymers. Since natural cellulose has a highly crystalline aggregate structure and a dense hydrogen bonding network between molecular chains, its dissolution and processing are difficult, and its functional application is greatly limited. Recently, ionic liquids as novel solvent systems of cellulose have developed prosperously, providing a new platform for cellulose homogeneous processing and efficient utilization. This review summarizes the latest research progress on homogeneous processing of cellulose in ionic liquids, from the aspects of the types, characteristics of ionic liquids, the ability to dissolve cellulose, and the construction of cellulose materials based on “dissolution-regeneration” and “homogeneous derivatization”. It would provide references for the green and high-value conversion of cellulose resources in the future.

    Advances in silicon-based ionic liquid microparticle enhanced gas capture and conversion
    Meisi CHEN, Weida CHEN, Xinyao LI, Shangyu LI, Youting WU, Feng ZHANG, Zhibing ZHANG
    2023, 74(9):  3628-3639.  doi:10.11949/0438-1157.20230531
    Abstract ( 251 )   HTML ( 29)   PDF (4425KB) ( 323 )  
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    It is of great scientific and environmental significance to solve the problem of excessive discharge of polluting gases in industrial processes. Ionic liquids (ILs), being green solvents in a liquid state at room temperature, possess unique advantages in gas capture and conversion. However, their inherent high viscosity poses a major challenge for industrial applications. Based on years of research, our team has discovered that instead of significantly reducing the viscosity of ILs, an effective approach to adapt them for industrial use is through the utilization of "micro particulation" technology, enabling efficient deployment of ionic liquids in a quasi-stationary state. In view of this, the research progress on the application of ionic liquid micro particles with silica as a medium and its derived ILs nano-micro interface reaction units for gas capture and conversion is reviewed, the characteristic advantages of micro particulated IL systems over conventional systems are discussed, and the "micro particulation" of ILs is analyzed. The application prospects and industrial feasibility of "micro particulation" of ILs are discussed.

    Application of ionic liquid-based deep eutectic solvents for CO2 conversion
    Yepin CHENG, Daqing HU, Yisha XU, Huayan LIU, Hanfeng LU, Guokai CUI
    2023, 74(9):  3640-3653.  doi:10.11949/0438-1157.20230534
    Abstract ( 350 )   HTML ( 18)   PDF (1395KB) ( 522 )  
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    As a greenhouse gas, CO2 is a precious C1 resource. In order to achieve the strategic goal of “carbon peaking and carbon neutrality”, it is imperative to vigorously develop carbon dioxide utilization and storage technologies. Ionic liquids are green solvents composed of organic cations and organic or inorganic anions, while deep eutectic solvents (DESs) are a novel kind of green solvent formed by hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) via hydrogen bonds. Ionic deep eutectic solvents (iDES) are new green solvents. They not only have similar chemical properties with ionic liquids, such as low vapor pressure, wide liquid temperature range, high thermochemical stability, and tunable structure properties, but also have the characteristics of hydrogen bonds. In recent years, a series of iDES containing choline, quaternary ammonium salts, and quaternary phosphonium salts were reported as green sorbents, solvents, and catalysts for highly efficient capture and transformation of CO2. However, the application and mechanism of iDES in the direction of CO2 conversion have not been systematically summarized. Therefore, this article reviews iDES for CO2 conversion during the last two decades (2003—2023), focusing on the thermal catalysis, biocatalysis, electrocatalysis of CO2 to obtain a variety of high-value chemicals, such as cyclic carbonate, carbamate, methanol, CO and CaCO3. Additionally, the mechanism of iDES on the catalytic reaction of CO2 is discussed. Moreover, the development directions and challenges of DESs for CO2 conversion are discussed.

    Multi-scale simulation and study of volatile phenols removal from simulated oil by ionic liquids
    Minghao SONG, Fei ZHAO, Shuqing LIU, Guoxuan LI, Sheng YANG, Zhigang LEI
    2023, 74(9):  3654-3664.  doi:10.11949/0438-1157.20230634
    Abstract ( 198 )   HTML ( 14)   PDF (3536KB) ( 202 )  
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    A multi-scale simulation was conducted on the extraction of phenol and benzene in simulated oil by ionic liquids. Based on the COSMO-RS model, ionic liquids with good extraction effects were screened, and the σ-profile of ionic liquids and volatile phenols and the excess of the mixture were calculated. Enthalpy is used to explore the polarity and non-ideality of a system. Parameters such as electrostatic potential, weak interactions, radial distribution function, and spatial distribution function between the volatile phenols and ionic liquids were investigated through quantum chemical calculations and molecular dynamics simulations, aiming to understand the interaction mechanisms. A process for extracting volatile phenols from simulated oil using ionic liquids was designed, and the process conditions were further optimized through sensitivity analysis. The computational results confirm the feasibility and advancement of using ionic liquids for the removal of volatile phenols.

    Molecular understanding of interfacial polarization and its effect on ionic liquid hydrogen bonds
    Junfeng LU, Huaiyu SUN, Yanlei WANG, Hongyan HE
    2023, 74(9):  3665-3680.  doi:10.11949/0438-1157.20230489
    Abstract ( 228 )   HTML ( 12)   PDF (5968KB) ( 395 )  
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    The structure and behavior of ionic liquid (IL) at the electrode interface have an important impact on their practical chemical applications such as supercapacitors and immobilized catalysts. In these applications, the interactions between IL with solid surfaces are common. Understanding the effect of the interfacial interactions on hydrogen bonds of IL is crucial for their practical chemical applications. However, due to the diversity of IL and solid surfaces, as well as the coexistence and coupling of many types of interactions on the surface, the effects of interfacial polarization on hydrogen bonds and the quantitative relationship between them are not clear. In this work, the first-principles calculations were performed to investigate the molecular mechanism of interfacial polarization and its influence on the hydrogen bonds for seven imidazole-based IL at the two-dimensional (2D) solid surfaces. The 1-ethyl-3-methylimidazolium (Emim]+) was selected as the cation for the study, used as electrolytes widely owing to their excellent conductivity, quasi-planar structure, and enhanced electrochemical properties. It was paired with seven anions, including [Cl]-, [Br]-, thiocyanate ([SCN]-), dicyanamide ([DCA]-), dicyanoboranuide ([B(H2CN2)]-), tricyanomethanide ([TCM]-) and tetracyanoborate ([TCB]-). The typical three 2D materials, including graphene (Gra), boron nitride (BN), and molybdenum disulfide (MoS2) were chosen as the solid surfaces. The results showed that charge transfer and orbital interaction would occur when ionic liquids are adsorbed on these three 2D surfaces, which further resulted in significant interfacial polarization. Its strength also increased with the decrease of the adsorption energy of IL on the 2D surfaces. Moreover, the change of IL hydrogen bonds on surfaces was described by the bond length, bond angle, bond order, and bond energy. It was found that the interfacial polarization would weaken the strength of HBs, where the strength of hydrogen bonds reduced notably as the IL lost more charge. And the infrared spectra of IL on solid surfaces were also calculated to confirm the evolution of hydrogen bonds with the interfacial polarization. Finally, the canonical correlation analysis was applied to construct a correlating model involving different factors related to the hydrogen bonds at the solid surface, proving that interface polarization was negatively correlated with the hydrogen bond strength. These quantitative results on the hydrogen bonds of IL can not only help understand the molecular mechanism of IL-solid interface but also be beneficial for the rational design of IL toward high-performance applications.

    DFT and COSMO-RS theoretical analysis of SO2 absorption by polyamines type ionic liquids
    Zehao MI, Er HUA
    2023, 74(9):  3681-3696.  doi:10.11949/0438-1157.20230660
    Abstract ( 180 )   HTML ( 17)   PDF (12148KB) ( 103 )  
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    A computational study was conducted to investigate the absorption of sulfur dioxide (SO2) by protic ionic liquids (PILs) comprising the cations of N-hexylammonium ([HHexam]+), hexylethylenediaminium ([HHexen]+), hexyldiethylenetriaminium ([HHexdien]+), and the anion of TFSA[(CF3SO2)2N-]. The most stable configurations of PILs-nSO2 (n=1,2,3,4,5,6) were determined by using density functional theory (DFT) at the M06-2X/6-311G(d,p) level. The results revealed that N—H…O type hydrogen bonding was formed between the polar N—H groups on the cations and the O atoms in SO2. The analysis of vibrational frequency, second-order perturbation energy, and electron density revealed that the maximum hydrogen bonding was achieved when [HHexam][TFSA], [HHexen][TFSA] and [HHexdien][TFSA] combined with 3, 4, and 5 molecules of SO2, respectively, with maximum hydrogen bond energies of 57, 67, and 85 kJ/mol. The absence of further hydrogen bonding networks with SO2 suggests that SO2 absorption has reached saturation. The data also indicate that the SO2 absorption capacity increases with the number of amino groups in the PILs structure. COSMOtherm software calculations corroborate the findings, revealing an increasing trend for the SO2 solubilities from 5.0 to 5.3 to 6.2 mol in 1 mol PILs above, respectively. That is, as the number of amino groups in the cationic structure increases, its ability to absorb SO2 increases, which is basically consistent with the conclusions obtained from density functional theory calculations.

    Hydrodeoxygenation of lignin-derived compounds to alkanes in Raney Ni-protic ionic liquid system
    Shaoqi YANG, Shuheng ZHAO, Lungang CHEN, Chenguang WANG, Jianjun HU, Qing ZHOU, Longlong MA
    2023, 74(9):  3697-3707.  doi:10.11949/0438-1157.20230547
    Abstract ( 169 )   HTML ( 8)   PDF (2555KB) ( 224 )  
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    Lignin is the only aromatic compounds in biomass. Efficient conversion of lignin to alkane is of great significance for the full utilization of biomass. In this work, the reaction characteristics and rules of lignin-derived phenols and ethers hydrodeoxygenation (HDO) to cycloalkanes are investigated under the catalytic system of Raney Ni coupling with synthesized protic alcoholamine ionic liquids (ILs). The research proves that Raney Ni combining with diethanolamine trifluoromethane sulfonate ([2-HDEA]OTf) has the best catalytic effect on HDO of lignin-derived phenolic and ether compounds. The conversion of lignin derived phenols and ethers are >99.0%, and the cycloalkane yields of the target product are >80.0% at 130℃ for 15 h with 3 MPa H2 pressure. Raney Ni catalyst shows similar catalytic effect to noble metals such as Rh/C, and the ionic liquid anion structure (OTf) plays a key role in the catalytic deoxidation process. The catalytic system is recycled five times with phenol as the substrate to test its stability.

    Kinetics of ionic liquid catalyzed synthesis of 2-cyanofuran
    Jiali ZHENG, Zhihui LI, Xinqiang ZHAO, Yanji WANG
    2023, 74(9):  3708-3715.  doi:10.11949/0438-1157.20230255
    Abstract ( 180 )   HTML ( 17)   PDF (1500KB) ( 398 )  
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    2-Cyanofuran (CF) is an important bio-based derivative with a wide range of potential applications. It is a key raw material for the synthesis of furfurylamine, furoic acid and other products, but there are few studies on the synthesis of 2-cyanofuran. In this study, ionic liquid was used as catalyst to explore the kinetic process of preparing 2-cyanofuran by reaction of furfural and hydroxylamine ionic liquid salt. The effect of reaction temperature and reaction time on the product yield was investigated. The kinetic model was established, and the kinetic parameters were validated. The experimental results showed that the furfural conversion and 2-cyanofuran yield were 100% when the reaction temperature is 120℃ and the reaction time was 2 h. The activation energy, pre-exponential factor and kinetic equation were obtained by calculation. By comparing the calculated and experimental values, it was found that the average error was 0.34%, which verified the accuracy of the kinetic equation and provided theoretical guidance for the subsequent application of 2-cyanofuran.

    Study on catalytic synthesis of sec-butanol by tunable choline-based basic ionic liquids
    Jie CHEN, Yongsheng LIN, Kai XIAO, Chen YANG, Ting QIU
    2023, 74(9):  3716-3730.  doi:10.11949/0438-1157.20230548
    Abstract ( 163 )   HTML ( 14)   PDF (2987KB) ( 197 )  
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    The use of basic catalysts to catalyze the transesterification of sec-butyl acetate and methanol to prepare sec-butanol has become a research hotspot in the chemical industry. Compared to traditional basic catalysts, basic ionic liquids have more efficient catalytic efficiency and robust reusability, making them a new class of green catalysts with development potentials. Therefore, this study designed and synthesized five choline-based basic ionic liquids, and confirmed through characterization and experiments that the basicity of anions is a key factor affecting their catalytic activity. The results from the response surface method (RSM) analysis showed that suitable reaction conditions of imidazolized choline [Ch][IM] were as follows: the reaction temperature was 45℃, the alcohol ester ratio was 4.42∶1, and the catalyst dosage was 8.91%, the conversion rate of sec-butyl acetate reached 93.95%, which was much higher than that of traditional catalysts such as sodium alcohol, thus confirming its high catalytic efficiency in the transesterification reaction and the possibility of application in the industrial production of sec-butanol.

    Separation of methyl propionate + methanol azeotrope using ionic liquid entrainers
    Lizhi WANG, Qiancheng HANG, Yeling ZHENG, Yan DING, Jiaji CHEN, Qing YE, Jinlong LI
    2023, 74(9):  3731-3741.  doi:10.11949/0438-1157.20230517
    Abstract ( 239 )   HTML ( 13)   PDF (3857KB) ( 452 )  
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    Using ionic liquids [BMIM][NTF2] and [HMIM][NTF2] as entrainer, the separation of the azeotropic mixture for methyl propionate + methanol through extractive distillation was investigated. The mechanism for extractive distillation separation was analyzed by molecular structure optimization. Based on the experimental data from literature and the authors’ previous work, the new thermodynamic model parameters of NRTL were obtained. The conventional two-column process for the separation of binary mixture was employed for the investigated system in this work. As a comparison, the process of extractive distillation and pressure swing distillation using phenol as entrainer was constructed at the same time. Based on the Aspen Plus simulation software, the influence of the main operation parameters of the above-mentioned separation process on the separation performance was analyzed, and the energy consumption, annual total cost (TAC) and CO2 emission of each process were calculated and compared. The results show that the ionic liquid process can separate the investigated azeotrope, and the purity of the product can reach to 99.9%(mass). The process with [HMIM][NTF2] entrainer can decrease, 11.68%—43.68% TAC and 32.11%—68.46% CO2 emission. The results of this work would provide theoretical basis and practical guide for the design and optimization of the separation process for azotropic methyl propionate + methanol mixture.

    Reviews and monographs
    Research progress in dry purification technology of highly toxic gas PH3
    Xuejin YANG, Jintao YANG, Ping NING, Fang WANG, Xiaoshuang SONG, Lijuan JIA, Jiayu FENG
    2023, 74(9):  3742-3755.  doi:10.11949/0438-1157.20230604
    Abstract ( 227 )   HTML ( 16)   PDF (5026KB) ( 298 )  
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    Phosphine (PH3) is a highly toxic gas that comes from a wide range of sources. If it is discharged into the atmosphere without treatment, it will cause serious harm to the human body and the environment. In recent years, the state has imposed strict regulations on the emission of PH3, so the deep purification of PH3 from exhaust gas has received widespread attention. The dry methods are the mainstream PH3 purification technology, which mainly include adsorption and catalytic methods. Compared with the wet method, the dry method has the advantages of good performance, high stability, low water consumption, and no secondary pollution. In this paper, starting from the adsorption method, the research status of composite metal oxide adsorbent, activated carbon adsorbent, and other materials (molecular sieve, silica, etc) were discussed, and the structural properties and advantages and disadvantages of various types of dephosphorylated adsorbents were analyzed in depth. Secondly, the mechanism of catalytic decomposition of PH3 was summarized, focusing on the structure-activity relationship of various types of catalysts. Finally, the application of other dry methods (combustion, plasma degradation, and biological methods) in the field of PH3 purification were introduced. On this basis, the main advantages of dry dephosphorization technologies as well as the challenges are discussed, and the direction of development of dry PH3 removal technologies is envisioned. This work is expected to provide reference and guidance for the construction and design of adsorbents/catalysts for phosphorus removal.

    Molecular dynamics simulation insight into translocation behavior of organic cage across the cellular membrane
    Jianbo HU, Hongchao LIU, Qi HU, Meiying HUANG, Xianyu SONG, Shuangliang ZHAO
    2023, 74(9):  3756-3765.  doi:10.11949/0438-1157.20230550
    Abstract ( 173 )   HTML ( 5)   PDF (4589KB) ( 149 )  
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    Nanomedicines have targeted and sustained-release properties and are important tools for cancer treatment. Among them, the optimized design of nanocarriers is the key to improving the efficacy of anti-tumor nanomedicines. Organic cages (OCs) are an innovative kind of porous nanomaterial that has found widespread use in nanomedicine due to advantages such as physicochemical tenability and modularity design. Based on the dynamics and thermodynamic perspectives, a series of OCs with varied architectures and their derivatives derived surface-modification were constructed, and their transmembrane transport behavior was studied. The dynamic and thermodynamic properties of OCs during transport were studied. It was discovered that the structural deformation of OCs played an important role in transmembrane transport. Furthermore, surface modification boosts the organic cage's target identification ability while making it more hydrophilic, which causes a larger transmembrane transport energy barrier and hampers transmembrane transport. This article systematically explains the interaction rules between organic cages and cell membranes at the molecular level, providing theoretical guidance for the design of nanocarriers and their application in biomedicine.

    Fluid dynamics and transport phenomena
    Two-phase flow simulation and surrogate-assisted optimization of gas film drag reduction in high-concentration coal-water slurry pipeline
    Song HE, Qiaomai LIU, Guangshuo XIE, Simin WANG, Juan XIAO
    2023, 74(9):  3766-3774.  doi:10.11949/0438-1157.20230674
    Abstract ( 125 )   HTML ( 15)   PDF (2388KB) ( 175 )  
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    To solve the problem of high-concentration coal-water slurry (CWS) pipeline transportation with large resistance, it was proposed to inject gas into the coal-water slurry pipeline and adopt gas film to reduce the resistance loss of the pipeline. For Bingham non-Newtonian fluid CWS, based on the volume of fluid (VOF) multiphase flow model, the effects of the key parameters of the gas pipe on the drag coefficient were analyzed through numerical simulation, and the influence of genetic aggregation response surface model and nonlinear programming by quadratic Lagrangian (NLPQL) algorithm were combined to perform surrogate-assisted optimization. The results show that the gas pumping inlet into the CWS pipeline can effectively reduce the wall shear stress, the gas velocity and the diameter of the gas pipe have a significant effect on the pipeline resistance coefficient. In addition, increasing the gas velocity and the diameter of the gas pipe can reduce the resistance coefficient, while the pipeline resistance coefficient is almost unaffected by the angle of the gas pipe. Taking the minimization of the resistance coefficient as the objective function, a set of gas pipe parameters is obtained. After optimization the resistance coefficient of the pipeline decreased by 0.0207, and the drag reduction rate is improved by 16.90%. The research results provide theoretical guidance for the mechanism and structural optimization of gas injection for drag reduction in high-concentration CWS pipelines.

    A rapid simulation method of gas-solid flow by coupling CFD and deep learning
    Kaijie WEN, Li GUO, Zhaojie XIA, Jianhua CHEN
    2023, 74(9):  3775-3785.  doi:10.11949/0438-1157.20230711
    Abstract ( 268 )   HTML ( 24)   PDF (1799KB) ( 425 )  
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    In the field of computational fluid dynamics (CFD), deep learning has been used for reconstructing flow field, predicting drag force, solving the Poisson equation, accelerating simulation and so on. In order to accelerate the simulation of gas-solid two-phase flow, the neural network of convolutional long short-term memory was used to predict physics quantities and it was coupled with OpenFOAM through LibTorch. Comparing the results of coupled calculations with those of pure OpenFOAM calculations, it was found that the present deep learning model prediction had problems such as non-conservative particle volume fraction and inaccuracy of very small values. These problems were eliminated through volume fraction correction and grid data filtering. Then different combinations of three physical quantities were selected for accelerating CFD by the deep learning model prediction. Given model prediction of the particle volume fraction and the gas velocity, the influence of adding prediction of the particle velocity and the pressure on the results of the coupling process was compared. It was found that the former was more accurate, and the difference may be related to the invoking order of different variables in the solver. In addition, the coupled calculation results and acceleration effects under different deep learning model prediction span ratios (1∶1, 3∶1, 5∶1, 10∶1) were studied, and it was found that within a certain error range, the current calculation process can accelerate by about 9 times, and the acceleration ratio has an approximately linear relationship with the span ratio.

    Study on influence mechanism of vacuum multi-layer insulation coupled with vapor-cooled shield on self-pressurization process of liquid hydrogen storage tank
    Ke LI, Jian WEN, Biping XIN
    2023, 74(9):  3786-3796.  doi:10.11949/0438-1157.20230544
    Abstract ( 306 )   HTML ( 10)   PDF (3470KB) ( 371 )  
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    Based on MATLAB program, a transient simulation model considering the vacuum multi-layer insulation, the vapor-cooled shield and the internal fluid domain of liquid hydrogen storage tank is constructed, which can be used to simulate the state change of the storage tank during the full cycle. The dimensionless vapor consumption factor ηc, dormancy extension factor ηs and unit factor η are introduced. ηc represents the vapor consumption of vapor-cooled shield during the full cycle of storage, ηs represents the extension of the dormancy period with vapor-cooled shield opened relative to that with vapor-cooled shield closed, and η is the ratio of ηs to ηc, representing the ability of vapor-cooled shield in shielding heat leakage. The effects of the dimensionless position of vapor-cooled shield, ηc, vapor flow rate and start-up time on ηs and η are investigated. The results show that the optimal position of vapor-cooled shield that maximizes ηs is 0.622 when the starting-up time of vapor-cooled shield is constant. Decreasing ηc helps to increase η. When the position of vapor-cooled shield is 0.622, and ηc decreases from 0.0640 to 0.0128, η increases by 34.7%. However, when the setting of the cooling screen deviates further from the optimal position, decreasing makes the increase smaller. When ηc and the duration time of vapor-cooled shield are fixed, ηs firstly increases then decreases with the delay of the start-up time. When the position of vapor-cooled shield is 0.622, the starting-up time that maximizes ηs is 23.26 d.

    Experimental study on flow boiling heat transfer of R134a in mini channel with diamond pin fin array
    Yubing WANG, Jie LI, Hongbo ZHAN, Guangya ZHU, Dalin ZHANG
    2023, 74(9):  3797-3806.  doi:10.11949/0438-1157.20230784
    Abstract ( 86 )   HTML ( 5)   PDF (3534KB) ( 62 )  
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    The flow boiling heat transfer characteristics of refrigerant R134a in rhombus discrete rib mini channels with angles of 30°, 60° and 90° were studied. The distribution area of diamond pin fin array in the mini channel is 300 mm long and 20 mm wide. The experiments were performed at a saturation pressure of (700±5) kPa at the inlet of the test channel, vapor quality from 0 to 1, mass flux between 200 kg/(m2·s) and 500 kg/(m2·s), and heat flux in range of 10—30 kW/m2. The results indicate that the flow boiling in the pin fin array is governed by nucleate boiling and convective boiling, the boiling heat transfer coefficient increases with the increase of mass flux and heat flux, but as vapor quality increases, the influence of heat flux almost disappears. In addition, differences in geometry of pin fin will affect the flow boiling heat transfer, the heat transfer coefficient of the diamond pin fin array at 90° is higher than that at 30°and 60°, and it is more significant at high vapor quality. Finally, on the basis of the analysis conclusion and the experimental data, a new correlation is proposed to predict the flow boiling heat transfer coefficient for mini channel with pin fin array of different structures.

    Investigation on energy conversion characteristics of vortex pump under bubble inflow
    Jiaqi YUAN, Zheng LIU, Rui HUANG, Lefu ZHANG, Denghui HE
    2023, 74(9):  3807-3820.  doi:10.11949/0438-1157.20230696
    Abstract ( 133 )   HTML ( 8)   PDF (8400KB) ( 78 )  
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    The vortex pump, a common type of centrifugal pump, finds wide application in the chemical industry. In chemical reaction processes, the pumped fluid often exhibits two-phase flow conditions, such as bubbly inflow. Understanding the evolution mechanism of the flow field in vortex pumps under bubbly inflow conditions is crucial for optimizing their structure and improving gas-liquid transportation performance. This study aims to investigate the gas-liquid two-phase flow field of a vortex pump under four different inlet gas volume fractions (IGVF) (1%, 5%, 10% and 15%) and three liquid flow rates (96, 120 and 144 m3/h), by coupling the mixture multiphase model and the population balance model. The energy gradient theory, entropy generation analysis, and flow field evolution law are used to reveal the energy conversion characteristics of the vortex pump under bubbly inflow conditions. The results indicate that in the vaneless chamber, the circulating flow takes the form of a vortex strip, with intensified circulation near the volute. The vortex strip distribution is wide-ranging and exhibits a stable structure. However, the strength of the circulating flow in the smaller radius section of the vaneless chamber is weak and only present in part of the flow channels. With an increase in IGVF, the vortex area in the vaneless chamber progressively expands, along with an increase in the number of vortex nuclei. However, when the IGVF increases to 10% and the gas content continues to increase, the number of circulating flows does not change significantly. At higher IGVF, gas accumulates at the impeller channel, resulting in an augmented energy gradient at the outer edge of the recessed chamber and vaneless chamber, as well as an increase in pulsation entropy production loss. This condition also leads to a more turbulent flow field. Consequently, the pressure increment and efficiency of the vortex pump decrease rapidly under high IGVF.

    Catalysis, kinetics and reactors
    Study on the catalytic denitrification performance of low-temperature NH3-SCR over LaMnO3/biochar catalyst
    Xiaoxiong FAN, Lifang HAO, Chuigang FAN, Songgeng LI
    2023, 74(9):  3821-3830.  doi:10.11949/0438-1157.20230455
    Abstract ( 148 )   HTML ( 12)   PDF (3275KB) ( 262 )  
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    Selective catalytic reduction with ammonia (NH3-SCR) is one of the most widely adopted technology to reduce the emission of nitrogen oxides. The activity and stability of catalyst plays a major role in the denitration process, and the increasing requirements for low working temperature, strong SO2/H2O resistance capability have stimulated the development of new type NH3-SCR catalyst. In this work, La-Mn perovskite oxide as active component and porous biochar as support were introduced to a biochar-supported catalyst, LMO/BCNA. The catalytic performance and SO2/H2O resistance of catalysts was tested in a fixed bed reactor. NO conversion achieved over 80% and N2 selectivity was over 90% within the temperature range of 100—250℃, and the highest NO conversion reached 95.8% with N2 selectivity of 95.4% at 225℃. Compared to LMO, LMO/biochar catalyst significantly improved denitration efficiency and widened working temperature window due to the synergistic catalytic effect of biochar. The introduction of biochar carrier weakens the catalyst’s adsorption of H2O and SO2, and enhances sulfur and water resistance. The kinetic model was built based on steady-state dynamics. On the test conditions and the presence of 5% O2, the NH3-SCR reaction order with respect to NO, O2 and NH3 was 0.66, 0 and 0, respectively. Accordingly, the activation energy for LMO/BCNA was 25.52 kJ/mol, which was much lower than that for commercial vanadium-wolframium-titanium catalysts of 40—94 kJ/mol.

    Study on operating conditions of proton exchange membrane fuel cells with non-uniform catalyst distributions
    Yitong LI, Hang GUO, Hao CHEN, Fang YE
    2023, 74(9):  3831-3840.  doi:10.11949/0438-1157.20230341
    Abstract ( 139 )   HTML ( 10)   PDF (3190KB) ( 235 )  
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    The gradient distribution of platinum loading in the catalyst layer along the flow channel direction affects the utilization of reactants and the transfer of heat and species. On this basis, the influence of operating conditions on the cell performance, heat and mass transfer of proton exchange membrane fuel cells with platinum loading gradient distribution along the flow channel direction is still unclear. Therefore, based on a two-dimensional, non-isothermal, two-phase proton exchange membrane fuel cell model, the effects of reactants flow direction and stoichiometric ratio on proton exchange membrane fuel cells with the two-gradient distribution or the three-gradient distribution of platinum loading in the multi-gradient distributions were investigated. The results show that the reactant flow direction has a weak impact on the electrical performance and species content of platinum loading gradient distribution fuel cells and the increase of stoichiometric ratio can improve the performance of the fuel cell with platinum loading gradient distribution. Furthermore, with the increase of stoichiometric ratio, the performance improvement degree of the cell with gradient distribution of platinum loading increases compared with the uniform distribution.

    Process system engineering
    Industrial data driven transition state detection with multi-mode switching of a hydrocracking unit
    Yue CAO, Chong YU, Zhi LI, Minglei YANG
    2023, 74(9):  3841-3854.  doi:10.11949/0438-1157.20230729
    Abstract ( 3472 )   HTML ( 17)   PDF (3390KB) ( 459 )  
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    The hydrocracking unit has many operating conditions and frequent switching. There must be a transition state when switching between different stable working conditions, which may cause fluctuations in the operating status of the unit and even cause accidents. Usually, experts will judge that the hydrocracking unit is currently in a stable or transitional state based on expert experience, and adopt corresponding monitoring and adjustment strategies, respectively. However, manual judgment has shortcomings due to individual differences and long experience accumulation period, which may lead to inaccurate transition state judgment. Therefore, a transition state detection method for multi-mode switching of the hydrocracking unit is proposed in this paper. First, combined with industrial big data and device process mechanism, wavelet based noise reduction and smoothing are used for industrial data collection, and then correlation analysis and principal component analysis (PCA) are used to reduce data dimensionality, which extracts the extra highly correlated variables that increase calculation cost and decrease information interference. Combining moving window split and moving variance computation with K-means clustering, transition state detection of the hydrocracking unit is realized. Finally, compared with classical K-means clustering and hierarchical clustering, the proposed method has better performance on transition state detection.

    Model simplification strategy of cracking furnace coking based on adaptive spectroscopy method
    Hao WANG, Zhenlei WANG
    2023, 74(9):  3855-3864.  doi:10.11949/0438-1157.20230582
    Abstract ( 114 )   HTML ( 4)   PDF (1820KB) ( 291 )  
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    Furnace tube coking is an important operation of ethylene cracking furnace, and accurate coking model is an important prerequisite for optimizing the control of the scorching process and improving the scorching efficiency. The common scorching process mechanism model is in the form of partial differential equation, which has the characteristics of infinite dimensionality and space-time coupling, and has high computational complexity, which is difficult to meet the requirements of lightweight models for real-time optimization and control. Therefore, a lightweight modeling strategy for the coking process of ethylene cracker based on adaptive spectroscopy method is proposed. Firstly, according to the characteristics of the change of coke layer in the coke and coking process of the furnace tube, the furnace tube is adaptively divided into focal section and non-focal section. Secondly, the Legendre polynomial is used as the spatial basis function to approximate the dimensionality reduction of the distribution parameters of the focal segment and the non-focal section, and the concentrated parameter model of the time dimension coefficients of the coke layer thickness distribution and temperature distribution in the furnace tube control input and the furnace tube is established to avoid the problem of large error caused by directly using the spectral method to approximate the distribution parameter system with local features.

    Fault detection using grouped support vector data description based on maximum information coefficient
    Yihao ZHANG, Zhenlei WANG
    2023, 74(9):  3865-3878.  doi:10.11949/0438-1157.20230501
    Abstract ( 114 )   HTML ( 4)   PDF (5447KB) ( 75 )  
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    There are often complex correlations among many variables in the industrial process. Traditional fault detection models often ignore the differences in correlation between different variables and use the same feature extraction method for variables with different correlation relationships, resulting in poor detection performance. In response to the above issues, this article proposes a fault detection model based on maximum information coefficient grouping support vector data description. Firstly, the maximum information coefficient matrix between variables is calculated, and the variables are grouped according to different correlations. Then, the maximum information coefficient provides theoretical guidance for the weight allocation of Gaussian and polynomial kernels in the mixed kernel function of the model. Thus, different support vector data description detection models are established for each group, achieving a close combination of maximum information coefficient and support vector data description, and ultimately achieving distributed fault detection. The feasibility and effectiveness of the model were verified through simulation comparison.

    Biochemical engineering and technology
    Removal of monoclonal antibody aggregates with ion exchange chromatography by flow-through mode
    Yaxin ZHAO, Xueqin ZHANG, Rongzhu WANG, Guo SUN, Shanjing YAO, Dongqiang LIN
    2023, 74(9):  3879-3887.  doi:10.11949/0438-1157.20230666
    Abstract ( 215 )   HTML ( 5)   PDF (2582KB) ( 433 )  
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    Two cation exchange media, Eshmuno CP-FT and Eshmuno CPX, with the same matrix and ligand but different ligand density and grafting methods, were compared in their ability to remove monoclonal antibody aggregates in flow-through mode. First, the static adsorption properties of monoclonal antibody (mAb) monomers and aggregates with two resins under different pH and conductivity were investigated. It was found that high monomer purity and yield could be achieved under low pH and high conductivity, or high pH and low conductivity conditions. The comprehensive performance of Eshmuno CP-FT was better than that of Eshmuno CPX. The breakthrough curves under different residence times were measured at the optimal adsorption conditions. With the target of mAb monomer purity higher than 99%, the loading capacity of Eshmuno CP-FT resin could reach 556 g/L, and the monomer yield was 83.2%. For Eshmuno CPX, the loading capacity was only 269 g/L with a yield of 60.4%. In addition, the productivity of Eshmuno CP-FT was twice that of Eshmuno CPX, and the buffer consumption was only about half. The adsorption kinetics results indicated that Eshmuno CP-FT showed faster adsorption of the aggregates and stronger displacement effect on the monomers. In general, to remove monoclonal antibody aggregates with flow-through mode, it is important to design the resins in a rational way. The optimization of ligand density and its distribution can adjust and balance the binding between monomers and aggregates, and promote the adsorption and separation of aggregates. The results in the present work provide some guidance for the development of new resins for flow-through chromatographic separation.

    Energy and environmental engineering
    System integration and energy conversion mechanism of the power technology with integrated supercritical water gasification of coal and SOFC
    Zhewen CHEN, Junjie WEI, Yuming ZHANG
    2023, 74(9):  3888-3902.  doi:10.11949/0438-1157.20230689
    Abstract ( 149 )   HTML ( 6)   PDF (3565KB) ( 185 )  
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    Based on the hydrogen-rich characteristic of the syngas produced through supercritical water gasification of coal, a power system with integrated supercritical water gasification of coal with solid oxide fuel cell (SOFC) and gas turbine is proposed. The high-temperature and high-pressure sensible enthalpy of the gasification products is recovered by an expander, and the chemical energy is successively utilized by the SOFC and gas turbine for power generation. The sensible heat of the exhaust flue gas at the outlet of the gas turbine and the air at the outlet of the SOFC cathode is mostly used for preheating the feed water of the boiler. Under the conditions of gasification temperature and pressure of 660℃/250 bar and coal-water-slurry concentration (CWSC) of 11.3% (mass) in the gasifier, the power generation efficiency of the system can reach 54.01%, and the exergy efficiency is 52.79%. Compared with the most advanced 1000 MW ultra-supercritical steam Rankine cycle coal-fired power station, the new system proposed in this article can achieve an annual CO2 emission reduction of 390000 t. The coal based power generation system proposed in this article further deepens the cascade utilization of coal chemical energy, and achieves efficient matching of the energy levels between various subunits, which will help to achieve the carbon peaking and carbon neutrality goal.

    Research on discharge path and evaluation of spent lithium-ion batteries
    Fei KANG, Weiguang LYU, Feng JU, Zhi SUN
    2023, 74(9):  3903-3911.  doi:10.11949/0438-1157.20230759
    Abstract ( 152 )   HTML ( 14)   PDF (2342KB) ( 210 )  
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    With the rapid development of new energy vehicles, the recycling of spent lithium-ion batteries has received widespread attention. Discharge is an important step in the recycling process of spent lithium-ion batteries. At present, sodium chloride solution is mainly used to achieve discharge, which leads to the discharge of a large amount of waste liquid containing heavy metals and high organic matter, and will produce hydrogen, methane, etc., which has high treatment cost and serious environmental and safety risks. This study systematically studied the effects of different discharge media during solution treatment on discharge time, gas generation, electrolyte leakage, metal dissolution, etc., analyzed the change law of gas-liquid-solid three-phase composition, explored the discharge path mechanism of lithium-ion batteries, and clarified the evaluation and control methods of discharge process resources, environment, and safety. An intrinsically safe and efficient discharge technique is further constructed. It is found that the decrease of residual voltage of lithium-ion battery during chemical discharge is mainly caused by three paths: electrolytic water, electrolyte leakage and battery short circuit heat release. The positive and negative electrodes of lithium-ion batteries produce oxygen and hydrogen respectively during the early water electrolysis process, and then the competitive reaction of electrochemical corrosion or external short circuit of metal deposition occurs, and the metal dissolution and electrolyte leakage process occur successively. Through the evaluation of different discharge media, it is found that a sodium sulfate solution based on electrolyzed water with a very small amount of electrolyte dissolved out is optimal. Using the electricity release path as a guide, it solved the problems of large amounts of electrolyte leakage and heavy metal dissolution during the solution discharge process from the source. It provides effective support for the efficient recycling of spent lithium-ion batteries.

    Chemical conversion of dissolved organic matter in petrochemical spent caustic along a wet air oxidation pretreatment process
    Baiyu YANG, Yue KOU, Juntao JIANG, Yali ZHAN, Qinghong WANG, Chunmao CHEN
    2023, 74(9):  3912-3920.  doi:10.11949/0438-1157.20230702
    Abstract ( 99 )   HTML ( 3)   PDF (3185KB) ( 444 )  
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    Wet air oxidation (WAO) is an effective pretreatment process for high-concentration petrochemical spent caustics. In this study, an integrated analysis based on three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), gas chromatography-mass spectrometry (GC-MS) and orbitrap mass spectrometry (Orbitrap MS) was established to investigate chemical conversion behaviors of petrochemical spent caustic along a WAO process at molecular level. Oxygen-dehydrogenation (+1O-2H and +2O-2H), oxygenation (+3O) and dealkylation (-C2H6) reactions happened in WAO process, resulting in a very significant change of DOM constituents. The molecular structures of fluorescent DOM converted from high ring number (≥5 rings) to low ring number (3 or 4 rings). Weak polar DOM, mainly thiobenzaldehyde and 3,4-bis(ethoxymethyl)-thiophene, is converted to sulfates, thiophenic acid and thioethers. The polar DOM, mainly O2—4 and O3S1 species with low unsaturation (DBEwa 3.727) and O/Cwa (0.386), is converted into O5—9 and O4—9S1 species with high unsaturation (DBEwa 5.911) and O/Cwa (0.537). Compound types of polar DOM increased from 1792 to 4909 by WAO pretreatment and the biodegradability of effluent improved by 35%.

    Study on solar thermoelectric power generation characteristics based on selective absorption nanofilm
    Cong QI, Zi DING, Jie YU, Maoqing TANG, Lin LIANG
    2023, 74(9):  3921-3930.  doi:10.11949/0438-1157.20230461
    Abstract ( 102 )   HTML ( 4)   PDF (3194KB) ( 83 )  
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    In order to improve the efficiency of solar thermoelectric power generation, this paper designs a new thermoelectric power generation device based on selective absorption nanofilm. The effects of light intensity and light angle on its performance were studied, and a comparative study was conducted with a thermoelectric generator based on commercial solar paint. The results showed that compared to commercial solar coating-based thermoelectric generators, adopting selective absorption nanofilms as the heat-absorbing layer can effectively increase the output power of the system, the temperature difference between the hot and cold ends of the temperature differential power generation sheet can be increased by 1—2℃, and the output power can be increased by up to 42.6% under low light intensity conditions.

    Microscopic mechanism of SiO2-H2O nanofluids to enhance the wettability of coal dust
    Jiajia ZHAO, Shixiang TIAN, Peng LI, Honggao XIE
    2023, 74(9):  3931-3945.  doi:10.11949/0438-1157.20230557
    Abstract ( 158 )   HTML ( 0)   PDF (13485KB) ( 100 )  
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    Coal dust pollution is one of the problems that the world’s coal industry needs to solve urgently. Exploring green and efficient new coal dust wetting agents has potential application value in this field. In this study, the mechanism of the effect of SiO2-H2O nanofluid on the wettability of coal dust was investigated by the Wender model using Materials Studio molecular simulation software and physical experiments. The results show that the reactivity of SiO2 nanoparticles (NPs) is high, and their surface hydroxyl groups can easily form hydrogen bonds with coal molecules and water molecules, thus affecting the wetting properties of coal dust. NPs have a strong ability to interact with coal molecules, and their adsorption on the surface of coal dust can adsorb more water molecules. When the adsorption number of NPs was 0—5, the interaction energies between coal and NPs, NPs and water, and the number of hydrogen bonds between solid-liquid molecules in the adsorption system tended to increase with the increase in the number of NPs. The g(r) curves between hydrogen and oxygen atoms in coal and NPs have the largest values and higher peaks, while the g(r) curves between hydrogen and oxygen atoms in coal and water are the opposite. With the increase of the adsorbed number of NPs, the water molecule mean square displacement and diffusion coefficient tended to increase, which accelerated the wetting of coal dust. Compared with water, the nanofluids have lower surface tension, and when the particle concentration is 2.0%(mass), the decrease rate of contact angle of modified coal dust reaches about 52.85%—61.51%, while the adsorption and agglomeration of NPs on the surface of nanofluid-treated coal dust is obvious. In this study, the molecular simulation results were verified with the experimental results, which elucidated the microscopic mechanism of NPs to enhance the wettability of coal dust, obtained the influence law of NPs on the wettability of coal dust, revealed the adsorption characteristics of NPs on the surface of coal dust, and laid a theoretical foundation for the enhancement of the wettability of coal dust by SiO2-H2O nanofluids.

    Material science and engineering, nanotechnology
    Study of the enhanced thermoelectric properties of ionic hydrogel materials by 2,5-dihydroxybenzenesulfonate
    Yang WANG, Yongqiang DAI, Wei ZENG
    2023, 74(9):  3946-3955.  doi:10.11949/0438-1157.20230474
    Abstract ( 140 )   HTML ( 6)   PDF (2695KB) ( 105 )  
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    At present, ion conductor thermoelectric materials have made some progress in thermoelectric conversion of low-grade heat sources, but there are still problems such as low thermoelectric conversion efficiency and poor sustainability. This study investigated the effect of 2,5-dihydroxybenzenesulfonate (HQS) on the thermoelectric properties of ionic thermoelectric hydrogels under different conditions. By combining proton-coupled electron transfer (PCET) reaction with the Soret effect of protons with high diffusion coefficient, the results showed that the introduction of HQS can enhance the thermoelectric performance with a thermopower of 19.16 mV·K-1, an ionic thermoelectric figure of merit of 0.98, and a thermoelectric conversion efficiency of 0.19%. At a temperature gradient of 20 K, it can maintain a power output of 120 mW·m-2 for nearly 2.5 hours.

    Catalytic microwave pyrolysis of low-rank pulverized coal for preparation of high value-added modified bluecoke powders containing carbon nanotubes
    Lei WU, Jiao LIU, Changcong LI, Jun ZHOU, Gan YE, Tiantian LIU, Ruiyu ZHU, Qiuli ZHANG, Yonghui SONG
    2023, 74(9):  3956-3967.  doi:10.11949/0438-1157.20230132
    Abstract ( 150 )   HTML ( 11)   PDF (2694KB) ( 85 )  
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    The limitation of large-scale utilization of bluecoke powders in industrial production due to their small particle size and low volatiles, and their preparation through high value-added modification therefore is an attractive and promising research subject for now. In this study, the high value-added modified bluecoke powders containing carbon nanotubes were prepared by KOH-assisted microwave pyrolysis of low-rank pulverized coal. The effects of KOH addition (alkali-carbon ratio) on the morphological structure, graphitization, microcrystalline structure and carbon nanotubes content of the modified bluecoke powders were investigated, and the generation mechanism of carbon nanotubes in the modified bluecoke powders was speculated. The results showed that carbon nanotubes with diameters of 30—50 nm and lengths of several tens of micrometers were produced in the modified bluecoke powders at the alkali-carbon ratio of 1.0, and the content was about 3.01%(mass). With the increment of the alkali-carbon ratio, the formation of carbon nanotubes was promoted by the etching of K and Fe3C produced from minerals in the raw coal, meanwhile the ordering of modified bluecoke powders and the interaction of graphite layer spacing were enhanced. The characteristic peak G' in the Raman spectra of carbon nanotubes was found that indicated the high value-added modified bluecoke powders containing carbon nanotubes were successfully produced. In addition, the intensities of C—C, C—H and ether bonded C—O—C structures in FT-IR spectra of the modified bluecoke powders were significantly weakened. This phenomenon was caused by two potential reasons. On the one hand, these carbon structures became the direct solid-phase carbon source of carbon nanotube with the presence of catalysts. On the other hand, the thermal decomposition of these carbon structures released CO and CH4, which could be used as the gas-phase carbon source for carbon nanotubes. The formation of carbon nanotubes in the high value-added modified bluecoke powders may be the result of the joint action of the “top formation” model and the “particle-wire-tube formation” model.

    Investigation of thermoelectric transport properties of single-layer XSe2 (X=Zr/Hf)
    Yuanchao LIU, Bin GUAN, Jianbin ZHONG, Yifan XU, Xuhao JIANG, Duan LI
    2023, 74(9):  3968-3978.  doi:10.11949/0438-1157.20230622
    Abstract ( 92 )   HTML ( 1)   PDF (4379KB) ( 54 )  
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    Based on the density functional theory of first-principles, the thermoelectric transport properties of monolayer ZrSe2 and HfSe2 are systematically studied by combining Boltzmann transport equation and deformation potential theory. The influence mechanism of phonon harmonic effect and anharmonic effect on lattice thermal conductivity was analyzed, and the thermoelectric parameters such as Seebeck coefficient, power factor and conductivity at different temperatures were calculated. The conclusions indicate that the lattice thermal conductivities of monolayer ZrSe2 and HfSe2 are 3.23 and 4.50 W/(m·K) at 300 K respectively, and decrease with the increase of temperature. Meanwhile, the transverse acoustic branch (TA) in phonon branches plays a major role in the thermal conductivity. The highest ZT of n-type single-layer ZrSe2 and HfSe2 at 300 K are 1.50 and 1.95 respectively (higher than p-type). Among them, single-layer HfSe2 performs better, so n-type single-layer HfSe2 is a good thermoelectric material. Finally, the research results could provide theoretical guidance and reference for thermoelectric design and application based on single-layer ZrSe2 and HfSe2.