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Table of Content
28 December 2023, Volume 64 Issue 12
    Intrinsic kinetics of catalytic hydrogenation of 2-nitro-4-acetylamino anisole to 2-amino-4-acetylamino anisole over Raney nickel catalyst
    Xiangyang Cui, Xin Zhang, Baoju Wang, Yuqi Sun, Haikui Zou, Guangwen Chu, Yong Luo, Jianfeng Chen
    2023, 64(12):  1-8.  doi:10.1016/j.cjche.2023.06.013
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    The catalytic hydrogenation of 2-nitro-4-acetylamino anisole (NMA) is a less-polluting and efficient method to produce 2-amino-4-acetamino anisole (AMA). However, the kinetics of catalytic hydrogenation of NMA to AMA remains obscure. In this work, the kinetic models including power-law model and Langmuir-Hinshelwood-Hougen-Watson (LHHW) model of NMA hydrogenation to AMA catalyzed by Raney nickel catalyst were investigated. All experiments were carried out under the elimination of mass transfer resistance within the temperature range of 70–100 ℃ and the hydrogen pressure of 0.8–1.5 MPa. The reaction was found to follow 0.52-order kinetics with respect to the NMA concentration and 1.10-order kinetics in terms of hydrogen pressure. Based on the LHHW model, the dual-site dissociation adsorption of hydrogen was analyzed to be the rate determining step. The research of intrinsic kinetics of NMA to AMA provides the guidance for the reactor design and inspires the catalyst modification.
    Experiments and model development of p-nitrochlorobenzene and naphthalene purification in a continuous tower melting crystallizer
    Wenlong Xiao, Yonglin Li, Zhengming Yi, Sheng Yang, He'an Luo
    2023, 64(12):  9-17.  doi:10.1016/j.cjche.2023.06.004
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    With the increasing demand for high-purity products, the industrial application of melt crystallization technology has been highly concerned. In this study, the purification process of nitrochlorobenzene binary eutectic system (NBES) and naphthalene–benzothiophene solid solution system (NBSSS) in tower melting crystallizer is analyzed, and a mathematical model of crystallization process is established. The key parameters in terms of feed concentration, crystal bed height, reflux ratio and stirring speed efficiency on purification effects were discussed by the established model. The results show that the concentration of p-nitrochlorobenzene was purified from 90.85% to 99.99%, when the crystal bed height is 600 mm, the reflux ratio is 2.5, and the stirring speed is 12 r·min-1. The naphthalene concentration is purified from 95.89% to 99.99%, when the crystal bed height is 400 mm, the reflux ratio is 1.43, and the stirring speed is 16 r·min-1. The quality of the model is evaluated by the ARD (average relative deviation). The minimum ARD values of the NBES and NBSSS are 2.39% and 5.22%, respectively, indicating the model satisfactorily explains the purification process.
    α-Synuclein: A fusion chaperone significantly boosting the enzymatic performance of PET hydrolase
    Renwen Tian, Yan Sun
    2023, 64(12):  18-25.  doi:10.1016/j.cjche.2023.06.015
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    Extensive use of polyethylene terephthalate (PET) has brought about global environmental problems. A recently reported PET hydrolase (PETase) discovered from Ideonella sakaiensis showed high potential for degrading PET at moderate temperatures, but its activity and stability need further improvement for practical applications. Herein, we proposed to use α-synuclein (αS) as a fusion chaperone and created six PETase-αS fusion enzymes with linkers of different types and lengths. All the fusion enzymes exhibited improved enzymatic performance, presenting 1.5 to 2.6-fold higher activity towards bis-2(hydroxyethyl) terephthalate than PETase, as well as significantly increased stabilities. Fluorescence spectroscopy indicated that the chaperone fusion tightened the overall conformation and resulted in the opening of the substrate binding pocket, which led to the improved thermal stability and catalytic activity of the fusion enzymes. Remarkably, one of the fusion proteins, PETase-[(GS)(EK)]10-αS, showed 3.2 to 5.1 times higher PET degradation capability than PETase. The significantly boosted PET degradation performance was not only attributed to the enhanced enzymatic activity and stability, but also possibly due to the binding affinity of the fused αS domain for PET. These findings demonstrated that αS was an effective fusion chaperone for significantly enhancing the enzymatic performance of PETase.
    Influence of water vapor on the separation of volatile organic compound/nitrogen mixture by polydimethylsiloxane membrane
    Yifan Liang, Haibo Lei, Xinlei He, Haoli Zhou, Wanqin Jin
    2023, 64(12):  26-36.  doi:10.1016/j.cjche.2023.06.007
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    In the industrial treatment of waste volatile organic compound (VOC) streams by membrane technology, a third impurity, generally, water vapor, coexists in the mixture of VOC and nitrogen or air, and can affect membrane performance and the design of the industrial process. This study focused on the investigation of the effect of water vapor on the separation performance of the separation of VOC/water/nitrogen mixtures by a polydimethylsiloxane (PDMS) membrane. Three types of VOCs: water-miscible ethanol, water-semi-miscible butanol, and water-immiscible cyclohexane, were selected for the study. Different operating parameters including, concentration of the feed VOC, feed temperature, and concentration of the feed water were compared for the separation of binary and ternary VOC/nitrogen mixtures. The interaction between the VOC and water was analyzed to explain the transportation mechanism after analyzing the difference in the membrane performance for the separation of binary and ternary mixtures. The results indicated that the interaction between the VOC (or nitrogen) and water is the key factor affecting membrane performance. Water can promote the permeation of hydrophilic VOC but prevent hydrophobic VOC through the membrane for the separation of ternary VOC/water/nitrogen mixtures. These results will provide fundamental insights for the design of the recovery application process for industrial membrane-based VOCs, and also guidance for the investigation of the separation mechanism in vapor permeation.
    Mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device
    Xin Xu, Na Xu, Wei Zhang, Junwen Wang, Yao Li, Chen Yang
    2023, 64(12):  37-48.  doi:10.1016/j.cjche.2023.06.006
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    Mass transfer performance of gas–liquid two-phase flow at microscale is the basis of application of microreactor in gas–liquid reaction systems. At present, few researches on the mass transfer property of annular flow have been reported. Therefore, the mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device are studied in the present study. We find that the main factors, i.e., flow pattern, liquid film thickness, liquid hydraulic retention time, phase interface fluctuation, and gas flow vorticity, which influence the flow mass transfer property, are directly affected both by gas and liquid flow velocities. But the influences of gas and liquid velocities on different mass transfer influencing factors are different. Thereout, the fitting relationships between gas and liquid flow velocities and mass transfer influencing factors are established. By comparing the results from calculations using fitting equations and simulations, it shows that the fitting equations have relatively high degrees of accuracy. Finally, the Pareto front, namely the Pareto optimal solution set, of gas and liquid velocity conditions for the best flow mass transfer property is obtained using the method of multi-objective particle swarm optimization. It is proved that the mass transfer property of the gas–liquid two-phase flow can be obviously enhanced under the guidance of the obtained Pareto optimal solution set through experimental verification.
    Enhanced photocatalytic activity of methylene blue using heterojunction Ag@TiO2 nanocomposite: Mechanistic and optimization study
    Saptarshi Ghosh, Kamalesh Sen, Priyanka Debnath, Arghadip Mondal, Naba Kumar Mondal
    2023, 64(12):  49-63.  doi:10.1016/j.cjche.2023.06.014
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    The objective in this study is to investigate the adsorption-degradation of the methylene blue (MB) dye using a fabricated heterojunction Ag@TiO2 nanocomposite. The batch factors used in photo catalytic reactions were pH, UV-irradiation time, temperature, catalytic dosage, and concentration of MB. The results showed that 0.2×103 g·ml-1) of the catalytic dose caused the Ag@TiO2 adsorption to degrade by 96.67% with darks and UV exposure. Using the Langmuir-Hinshelwood model to determine the kinetic, the Ag@TiO2 displays a greater kinetic rate than TiO2 and silver nanoparticle (AgNPs). The photocatalytic degradation of MB, which is an endothermic reaction involving all catalysts, is shown by the thermodynamic parameter to have the positive value of enthalpy (ΔH°). The enthalpies observed were Ag@TiO2 (126.80 kJ·mol-1) < AgNPs (354.47 kJ·mol-1) < TiO2 (430.04 kJ·mol-1). Ascorbic acid (·OH scavenger), 2-propanol (·O2 scavenger), and ammonium oxalate (AO) (hole h+ scavenger) were employed to conduct the scavenger effects. The Ag@TiO2 demonstrated a reduction in MB degradation when combined with 2-propanol, and this clearly demonstrated that, in contrast to hydroxyl radicals (·OH) and hole (h+) scavengers, superoxide radical anion (·O2 scavenger) plays a significant role in MB degradation. Utilizing density functional theory (DFT) to elucidate the mechanism and B3LYP/6-311+G(d,p) level optimization, the degradation-adsorption process was explained. When the N-N, C-N or C-C bonds were severed, the Fukui faction was demonstrated for nucleophilic, electrophilic, and radical attack.
    Comparative analysis on gas–solid drag models in MFIX-DEM simulations of bubbling fluidized bed
    Ruiyu Li, Xiaole Huang, Yuhao Wu, Lingxiao Dong, Srdjan Belošević, Aleksandar Milićević, Ivan Tomanović, Lei Deng, Defu Che
    2023, 64(12):  64-75.  doi:10.1016/j.cjche.2023.06.002
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    In this study, the open-source software MFIX-DEM simulations of a bubbling fluidized bed (BFB) are applied to assess nine drag models according to experimental and direct numerical simulation (DNS) results. The influence of superficial gas velocity on gas–solid flow is also examined. The results show that according to the distribution of time-averaged particle axial velocity in y direction, except for Wen–Yu and Tenneti–Garg–Subramaniam (TGS), other drag models are consistent with the experimental and DNS results. For the TGS drag model, the layer-by-layer movement of particles is observed, which indicates the particle velocity is not correctly predicted. The time domain and frequency domain analysis results of pressure drop of each drag model are similar. It is recommended to use the drag model derived from DNS or fine grid computational fluid dynamics–discrete element method (CFD-DEM) data first for CFD-DEM simulations. For the investigated BFB, the superficial gas velocity less than 0.9 m·s-1 should be adopted to obtain normal hydrodynamics.
    In situ growth of cobalt on ultrathin Ti3C2Tx as an efficient cocatalyst of g-C3N4 for enhanced photocatalytic CO2 reduction
    Tongming Su, Jundong Meng, Ya Xiao, Liuyun Chen, Hongbing Ji, Zuzeng Qin
    2023, 64(12):  76-86.  doi:10.1016/j.cjche.2023.06.018
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    Photocatalytic CO2 reduction to valuable product exhibit promising prospect for solving the energy crisis and the greenhouse effect. Herein, Co-Ti3C2Tx/g-C3N4 (Co-TC/CN) composite with enhanced photocatalytic performance for converting CO2 to CO and CH4 was constructed by electrostatic self-assembly method. The close contact interface between Co-Ti3C2Tx and g-C3N4 nanosheets can be used as fast transport channels of photogenerated electrons and effectively promote the separation of photogenerated electrons and holes, and the interface between the Co and Ti3C2Tx might be the active sites for CO2 adsorption and activation. The optimized Co-Ti3C2Tx/g-C3N4 composite exhibited the highest photocatalytic performance with the CO and CH4 production of 55.04 μmol·g-1 and 2.29 μmol·g-1, respectively, which were 7.5 times and 5.8 times than those of g-C3N4. Furthermore, the stability of g-C3N4 was improved after coupling with Co-Ti3C2Tx.
    Tailoring the separation performance of a carbon nanotube-based mixed matrix membrane decorated with metal–organic framework
    Hui-Yong Wu, Hong-Xin Fu, Yu Liu, Xiao-Sa Zhang, Wen-Ze Li, Jian Luan
    2023, 64(12):  87-95.  doi:10.1016/j.cjche.2023.06.016
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    Synthesis of mixed matrix membranes (MMM) using carbon nanotubes (CNTs) has shown great prospects for achieving excellent selective separation because of its special structure. Nevertheless, the preparation of highly selective MMM faces challenges, which is attributed to the obstacles encountered by CNTs dispersion in polymer matrix and elimination of interface defects. A novel CNT-based composite decorated with metal–organic framework (MOF) was synthesized and applied to the preparation of MMM. MOF was post modified, and then carboxyl groups were inserted on the outer surface of CNTs. The synthetic MMM (Cu-MOF-en@MWCNT) not only has selective adsorption on dyes, but also has selective photodegradation on dyes. The method of using CNTs to wrap the outside of MOF has great potential in dye separation. The performance of MMM was further improved by decorating MOF on the filler to improve the selectivity to the designated dye.
    Synergistic effect of CuO coupled with MoS2 for enhanced photodegradation of organic dyes under visible light
    Umsalama Abuelgasim Abubakr Yasin, Zhixin Jia, Ziwen Qin, Tianyu Guo, Ruihua Zhao, Jianping Du
    2023, 64(12):  96-105.  doi:10.1016/j.cjche.2023.06.017
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    A series of MoS2-modified CuO (CuO/MoS2) heterostructures were successfully fabricated. The photodegradation properties of organic dyes were explored in detail under visible light. The photocatalytic results demonstrate that the CuO/MoS2-3 heterostructure delivers superior degradation rates towards methyl violet dye (MV) and rhodamine B (RhB), reaching 99.8% and 95.3% within 30 min, respectively. The decent photodegradation activity is due to improved visible light adsorption and faster transfer of electron-hole pairs. The radical trapping experiments show that superoxide radicals (·O2-) and holes (h+) are the main active species in the removal of MV. Furthermore, the CuO/MoS2-3 composite possesses the prominent stability and recyclability. This work offers a highly sustainable technique for designing a high-efficiency photocatalyst to remove environmental pollutants.
    Influence of support properties on selective oxidation of 2-methylnaphthalene on vanadia-molybdena based catalyst
    Yi Yu, Fanfan Li, Xiaocong Li, Guoji Liu, Li Xu, Xingchuan Yang
    2023, 64(12):  106-116.  doi:10.1016/j.cjche.2023.06.011
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    In this work, the catalytic performance of vanadia-molybdena loaded on TiO2, MgO, ZSM-5, NaY and Mordenite was investigated in the selective oxidation of 2-methylnaphthalene (2-MN) to 2-naphthaldehyde (2-NA). Results show that strong interactions between supports (TiO2, ZSM-5) and active components can promote the dispersion of active component. Monolayer VOx and MoOx are the main form on the catalyst surface, which is beneficial to the 2-NA selectivity. However, the corresponding weak interactions between Mordenite and active components may lead to the production of oxide crystals and the separation of active components, thus reducing the 2-NA selectivity. Due to the high Na content, new crystal NaVMoO6 forms on the NaY surface, which is inactive in the reaction. For V-Mo/TiO2, V and Mo can be inserted into the TiO2 lattice, changing the electronic structures of active components and support and improving the activity of surface oxygen species. This investigation highlights an important consideration on supports properties when designing supported catalysts.
    The extraction of aromatics using N-methylpyrrolidone: Liquid-liquid equilibrium determination and mechanism exploration
    Yanjing Li, Shilong Dong, Lili Wang, Xiaoyan Sun, Wenying Zhao, Shuguang Xiang
    2023, 64(12):  117-127.  doi:10.1016/j.cjche.2023.05.016
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    LLE data of cyclooctane/3-methylpentane + benzene/toluene + N-methylpyrrolidone (NMP) at 298.15 K and 313.15 K under a pressure of 101.3 kPa were measured in this work. The Othmer-Tobias and Hand equations were adopted to validate the reliability of LLE data, where the correlation coefficients (R2) were close to unity, indicating the high reliability of the experimental data. The experimental data were analyzed using the distribution coefficient (D) and separation factor (S), and the effect of NMP extracting benzene and toluene from aromatics was explored. Meanwhile, the reason for the different extraction efficiencies of benzene and toluene using NMP was analyzed by quantum chemical calculations. The NRTL and UNIQUAC thermodynamic models were used to correlate the liquid–liquid equilibrium data, and the relevant binary interaction parameters were obtained. The calculated root mean square deviation (RMSD) were all less than 0.0063, indicating that the obtained binary interaction parameters can be used to simulate and calculate the extraction of aromatics using NMP.
    Gold/Mg-Al mixed oxides catalysts for oxidative esterification of methacrolein: Effects of support size and composition on gold loading
    Wangtao Li, Qiancheng Zheng, Huayu Zhang, Yunsheng Dai, Zhengbao Wang
    2023, 64(12):  128-138.  doi:10.1016/j.cjche.2023.05.006
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    Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation. Effects of the support particle size, concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated. The catalysts are characterized by CO2-TPD, EDS, XPS, STEM and XRD techniques. Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion, resulting in a higher catalytic performance, and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution. The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst, and the optimum Mg/Al molar ratio is 0.1–0.2. This study underlines the importance of engineering support particle size, concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.
    Engineering of Ag@Pd/Al2O3 with varied Pd-shell thickness: Dynamic evolution of ligand and strain effects on acetylene selective hydrogenation
    Mingbo Yang, Tianxing Yang, Rui Ma, Sha Li, Yufei He, Dianqing Li
    2023, 64(12):  139-148.  doi:10.1016/j.cjche.2023.06.012
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    Bimetallic nanoparticles exhibit a synergistic effect that critically depends on their surface composition, but such promotion mechanisms become vague with varying surface compositions. Here, alumina supported Ag@Pd core–shell and PdAg alloy structure with controlled size and surface compositions were prepared to demonstrate synergetic mechanisms, particularly, ligand and strain effects on activity and ethylene selectivity for acetylene hydrogenation. The performance evaluation indicates that Ag@Pd catalysts with well-controlled Pd-shell thickness can effectively lower apparent activation energy and improve ethylene selectivity. Hydrogenation activity increases from 0.019 to 0.062 s-1 with decreasing Pd-shell thickness under mild conditions, which is 3–6 times higher than their alloyed and monometallic counterparts. Combined characterizations and density functional theory are conducted to reveal such shell-thickness-dependent performance. The ligand effect arising from Ag alloying in the interface of Ag@Pd2ML observes the strongest binding of acetylene, but it diminished sharply and the strain effect gets more prevailing with increasing shell thickness. The competition of ethylene desorption and deep-hydrogenation were also investigated to understand the selectivity governing factors, and the selectivity descriptor (0.5BE(C2H4) – BE(H)) was built to match the contribution of ligand and strain effect on the different surfaces of Pd-Ag bimetallic NPs. The exploration of synergetic mechanisms among bimetallic NPs with varied structure and surface compositions in this work can help us to deepen the understanding catalyst structure–activity relationship and provide a feasible way to optimize the overall catalytic performance.
    Phosphorus and nitrogen co-doped graphene for catalytic dehydrochlorination of 1,2-dichloroethane
    Haonan Yu, Xiaofeng Yang, Hongbin Yang, Jinming Xu, Yanqiang Huang
    2023, 64(12):  149-155.  doi:10.1016/j.cjche.2023.05.012
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    A phosphorus and nitrogen co-doped graphene (PNG) was developed via a two-step pyrolysis approach through the intermedium of g-C3N4 template and glyphosate as the phosphorus source, and was used for the catalytic dehydrochlorination of 1,2-dichloroethane (EDC) to vinyl chloride monomer (VCM) production. The characterization results indicate that a volcano relationship of surface area and surface properties with the usage of phosphorus precursor was observed, and the sample of PNG-900-6 possesses not only the thin film structure with enhanced surface area but also the smaller grain size of PNG attachments. Accordingly, such PNGs show a great improvement of catalytic performance in the dehydrochlorination of EDC, and the PNG-900-6 catalyst behaves the best with a 4-times higher activity than that on the nitrogen doped graphene (NG). It was also proved that the synergetic effect of the unique P-C coordination on the graphene to generate more quaternary nitrogen species was crucial in determining the catalytic performance of EDC conversion. Our results demonstrate that the phosphorus and nitrogen co-doped graphene offers many advantages in physical structure and chemical property, and are also great potential on the catalytic application in the dehydrochlorination of 1,2-dichloroethane.
    Construction of CuNiAl-LDHs electrocatalyst with rich-Cu+ and —OH for highly selective reduction of CO2 to methanol
    Gaiqin Miao, Lifei Liu, Xia An, Xu Wu
    2023, 64(12):  156-167.  doi:10.1016/j.cjche.2023.06.022
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    In this work, a high-performance CuNiAl-LDHs catalyst was innovatively synthesized for electrochemical carbon dioxide reduction (CO2RR) of methanol (CH3OH) through the modulated synthesis of Cu-based layered double hydroxide (LDHs). It was found that the optimal CuNiAl-LDHs has superior CH3OH selectivity compared to CuAl-LDHs and CuMgAl-LDHs, with the Faraday efficiency (FE) of 76.4% for CH3OH generation at -1.2 V. And their FE and current density (4.8 mA·cm-2) remained stable during up to 24 h of electrolysis. Meanwhile, this study confirms the significant performance advantages of CuNiAl-LDHs over their derived composite oxides. Series characterization further proves that the excellent catalytic performance of CuNiAl-LDHs is importantly associated with their richness in Cu+ and hydroxyl group (—OH). The research expands the application fields of LDHs compounds. Meanwhile, the series of discoveries provide a new insight for the preparation of CH3OH by constructing CO2RR.
    Separation of fuel additives based on mechanism analysis and thermodynamic phase behavior
    Mengjin Zhou, Yanli Zhang, Ke Xue, Haixia Li, Zhaoyou Zhu, Peizhe Cui, Yinglong Wang, Jingwei Yang
    2023, 64(12):  168-176.  doi:10.1016/j.cjche.2023.05.015
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    tert-butanol and ethyl acetate, as fuel additives and oxygenated fuels, can improve fuels quality and reduce exhaust emissions. Therefore, the recovery of these compounds from azeotropic systems is of great significance. Ionic liquids (ILs) are promising green solvents for separating azeotropic systems. In this study, an efficient extraction strategy based on 1-butyl-3-methylimidazolium acetate ([Bmim][AC]) is proposed. The mechanism by which ILs enable the separation of binary alcohol-ester azeotropes was revealed by evaluating the lowest conformational energy through combining an independent gradient model based on the Hirshfeld partition (IGMH) and frontier molecular orbitals, to preliminarily screen the extractants. The range of extractants was further reduced by a vapor–liquid phase equilibrium (VLE) experiment, and a modeling method for separating the alcohol–ester system and recovering the solvent using [Bmim][AC] and 1-ethyl-3-methyl-3-imidazolium acetate ([Emim][AC]) is established. Under the optimal operating conditions, the use of [Bmim][AC] can reduce the total annual cost (TAC) per year by 17.78%, and the emissions of CO2, SO2, and NO can be reduced by 10.86%. In this study, a comprehensive method for screening extractants is proposed, and the simulation process is optimized in combination with the economic and environmental impact. The results have important guiding significance for realizing efficient, energy-saving, and green azeotropic separation systems in industry.
    Preparation of ZIF-8@PEBAX/PVDF nanocomposite membrane by the combination of self-assembly and in-situ growth for removing thiophene from the model gasoline
    Zhesai Zhao, Qingwen Han, Wenwen He, Xiaolong Han
    2023, 64(12):  177-187.  doi:10.1016/j.cjche.2023.06.019
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    Metal-organic frameworks (MOFs) have gained attention in the development of MOFs/polymer hybrid membranes for pervaporation. However, the agglomeration of MOFs particles and interfacial defects limit its further application. In this study, we present a novel approach to fabricate a ZIF-8@PEBAX/PVDF nanocomposite membrane for removing thiophene from the model gasoline by combination of self-assembly and in-situ growth. Firstly, a PVDF supporting membrane was modified to have a negative charge. Next, positively charged zinc ions were attracted onto the negatively charged PVDF supporting membrane through electrostatic interaction. Afterwards, the Zinc ions deposited PVDF membrane was immersed into dimethylimidazole solution to form a uniform ZIF-8 layer. Finally, the ZIF-8 layer was coated with poly (ether-block-amide) (PEBAX) using the pouring method. Experimental results showed that the separating efficiency of the ZIF-8@PEBAX/PVDF nanocomposite membrane was improved significantly compared to that of pristine PEBAX membrane. The optimal permeation flux and enrichment factor of membrane were 27.80 kg·(m2·h)-1 and 6.9, respectively.
    Insight into the green route to dimethyl succinate by direct esterification of bio-based disodium succinate using CO2 and CH3OH
    Yu-Gao Wang, Xiao-Chen Han, Bao Gu, Hua-Shuai Wu, Jun Shen
    2023, 64(12):  188-195.  doi:10.1016/j.cjche.2023.05.017
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    The fermentation for succinic acid production outperforms other methods by low energy consumption and environmental benignity, with the resulting products mainly as disodium succinate (DSA). By directly esterifying DSA using CO2 and CH3OH, it is expected to avoid the use of inorganic acids. By high-resolution mass spectrometry analysis and theoretical calculation, this study establishes that the reaction consists of three steps, i.e., first forming 3-carboxypropanoate, then monomethyl succinate (MMS), and finally dimethyl succinate (DMS). A detailed kinetic analysis is further performed, the results demonstrate that the transformation of DSA to MMS is regarded to be a second-order reaction for reactant DSA, while the transformation of MMS to DMS is a first-order reaction for reactant MMS. The activation energy for the generation of MMS from DSA is 37.15 kJmol-1, and that for the generation of DMS from MMS is 85.80 kJmol-1, indicating the latter one is the rate-determining step.
    Computational fluid dynamics-discrete element method simulation of stirred tank reactor for graphene production
    Shuaishuai Zhou, Jing Li, Kaixiang Pang, Chunxi Lu, Feng Zhu, Congzhen Qiao, Yajie Tian, Jingwei Zhang
    2023, 64(12):  196-207.  doi:10.1016/j.cjche.2023.06.005
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    Liquid phase exfoliation (LPE) process for graphene production is usually carried out in stirred tank reactor and the interactions between the solvent and the graphite particles are important as to improve the production efficiency. In this paper, these interactions were revealed by computational fluid dynamics–discrete element method (CFD-DEM) method. Based on simulation results, both liquid phase flow hydrodynamics and particle motion behavior have been analyzed, which gave the general information of the multiphase flow behavior inside the stirred tank reactor as to graphene production. By calculating the threshold at the beginning of graphite exfoliation process, the shear force from the slip velocity was determined as the active force. These results can support the optimization of the graphene production process.
    Micro-interface enhanced mass transfer sodium carbonate absorption carbon dioxide reaction
    Hu Shen, Yingyu Xu, Jigang An, Bowen Jiang, Jinnan Sun, Guoqiang Yang, Zhibing Zhang
    2023, 64(12):  208-223.  doi:10.1016/j.cjche.2023.06.003
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    Micro-interface intensified reactor (MIR) can be applied in series/parallel in the absorption of CO2 in industrial gases by Na2CO3 due to the ability to produce large numbers of stable microbubbles. This work focuses on the variation pattern of mass transfer characteristics parameters of the reaction gas in Na2CO3 solution under the influence of different solution properties and operating parameters in the reaction of CO2 absorption by Na2CO3. The mass transfer characteristics parameters include bubble Sauter mean diameter, gas holdup, interfacial area, liquid side mass transfer coefficient, and liquid side volume mass transfer coefficient kLa. The solution properties and operating parameters include Na2CO3 concentration (0.05–2.0 mol·L-1), superficial gas velocity (0.00221–0.01989 m·s-1), superficial liquid velocity (0.00332–0.02984 m·s-1), and ionic strength (1.42456–1.59588 mol·kg-1). And volumetric mass transfer coefficients kLa and superficial reaction rates r of the MIR and the bubble column reactor are compared in the reaction of sodium carbonate absorption of carbon dioxide, and the former shows a greater improvement under different solution properties and operating parameters. The enhanced role of MIR in mass transfer in non-homogeneous reactions is verified and the feasibility of industrial practical applications of MIR is demonstrated.
    Microchannel reactors for Fischer-Tropsch synthesis: Experimental investigation and mathematical modeling
    Huili Cao, Run Xu, Xiaojin Tang, Tao Yang, Shuandi Hou, Chaopeng Hou
    2023, 64(12):  224-240.  doi:10.1016/j.cjche.2023.04.027
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    The Fischer-Tropsch synthesis is a significant technology for converting coal, natural gas, and biomass into synthetic fuels. In recent years, the use of microchannel reactors for the Fischer-Tropsch synthesis has attracted significant attention. Fischer-Tropsch synthesis experiments were carried out in a microchannel reactor and the influences of reaction conditions on the experimental results were investigated in this study. Based on the experimental data, a dynamic multi-component pseudo-homogeneous variable-volume flow model of microchannel reactors for the Fischer-Tropsch synthesis was built to determine the pressure-, velocity-, conversion- and (component-wise) concentration-distributions in reaction channels. The model takes into account the combined effects of gas volume expansion caused by the frictional pressure drop and gas volume contraction caused by reaction consumption. A novel effective method for calculating the pressure and superficial gas velocity values in microchannel reactors was proposed in the model. Besides that, two sets of experimental data were selected from references to evaluate the validity and accuracy of the model. The reaction performances in the microchannels were analyzed carefully based on the calculated results.
    Polybenzoxazine/organosilicon composites with low dielectric constant and dielectric loss
    Manlin Yuan, Xin Lu, Xiaoyun Ma, Hao Lin, Angui Lu, Liyan Shao, Zhong Xin
    2023, 64(12):  241-249.  doi:10.1016/j.cjche.2023.06.024
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    The evolution of electronic communication technology raises higher requirements for low dielectric constant (low-k) materials. For this, a benzoxazine functional organosilicon (HP-aptes) with dense Si—O—Si crosslinking networks and large sterically hindered tert-butyl groups was prepared by the sol–gel method. Then, a series of polybenzoxazine composites (PPHP) were prepared from intrinsically low dielectric constant bis-functional benzoxazine monomer (P-aptmds) and HP-aptes. The double crosslinking networks of polybenzoxazine and organosilicon further increased the crosslinking density and decreased the dipole density of composites, which endowed the composites with enhanced low-k properties. When the content of HP-aptes is 30% (mass), the crosslinking density was 2.05×10-3 mol·cm-3, while that of PP-aptmds was 3.31×10-3 mol·cm-3. In addition, the dielectric constant and dielectric loss of PPHP composite at 1 MHz could reach 2.61 and 0.0056, respectively.
    Solubility study of hydrogen in direct coal liquefaction solvent based on quantitative structure–property relationships model
    Xiao-Bin Zhang, A. Rajendran, Xing-Bao Wang, Wen-Ying Li
    2023, 64(12):  250-258.  doi:10.1016/j.cjche.2023.05.014
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    Direct coal liquefaction (DCL) is an important and effective method of converting coal into high-value-added chemicals and fuel oil. In DCL, heating the direct coal liquefaction solvent (DCLS) from low to high temperature and pre-hydrogenation of the DCLS are critical steps. Therefore, studying the dissolution of hydrogen in DCLS under liquefaction conditions gains importance. However, it is difficult to precisely determine hydrogen solubility only by experiments, especially under the actual DCL conditions. To address this issue, we developed a prediction model of hydrogen solubility in a single solvent based on the machine-learning quantitative structure–property relationship (ML-QSPR) methods. The results showed that the squared correlation coefficient R2 = 0.92 and root mean square error RMSE = 0.095, indicating the model’s good statistical performance. The external validation of the model also reveals excellent accuracy and predictive ability. Molecular polarization (α) is the main factor affecting the dissolution of hydrogen in DCLS. The hydrogen solubility in acyclic alkanes increases with increasing carbon number. Whereas in polycyclic aromatics, it decreases with increasing ring number, and in hydrogenated aromatics, it increases with hydrogenation degree. This work provides a new reference for the selection and proportioning of DCLS, i.e., a solvent with higher hydrogen solubility can be added to provide active hydrogen for the reaction and thus reduce the hydrogen pressure. Besides, it brings important insight into the theoretical significance and practical value of the DCL.
    Sustainable catalytic graphitization of biomass to graphitic porous carbon by constructing permeation network with organic ligands
    Pengfei Liu, Wenqiao Du, Xiangjing Liu, Long Zhang, Zhimin Chen
    2023, 64(12):  259-270.  doi:10.1016/j.cjche.2023.06.025
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    Common strategies for catalytic graphitization of biochar into graphitic porous carbon (GPC) still face great challenges, such as the realization of simple procedures, energy conservation, and green processes. Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification. Herein, a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon (RHC) at a relatively low temperature of 800–1000 ℃ with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt (EDTA-iron) and the recovery ratio of catalyst is as high as 97%. The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron, resulting in highly graphitized and developed porous GPCs. The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading, temperature, and holding time. The catalyst EDTA-iron with a lower concentration mainly plays the role of etching, which promotes the formation of porous carbon with larger surface area (SBET = 1187.2 m2·g-1). The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree (ID/IG = 0.19). The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET, XRD, Raman, TEM and TGA. This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon, but also provides a feasible method for the preparation of biomass-based porous carbon.
    AlCl3 modified Pd/Al2O3 catalyst for enhanced anthraquinone hydrogenation
    Qinqin Yuan, Jingyue Liang, Wei Li, Jinli Zhang, Cuili Guo
    2023, 64(12):  271-280.  doi:10.1016/j.cjche.2023.06.021
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    Anthraquinone hydrogenation to produce H2O2 is an economically interesting reaction with great industrial importance. Here, we report a series of Pd/xAl catalysts with different AlCl3 contents by a conventional stepwise impregnation method. The optimal Pd/1.0Al catalyst exhibits a higher performance toward anthraquinone hydrogenation with 8.3 g·L-1 hydrogenation efficiency, 99.5% selectivity and good stability, obviously superior to that of Pd/Al2O3 catalyst (5.2 g·L-1 and 97.2%). Detailed characterization demonstrates that AlCl3 can be grafted on the γ-Al2O3 support to obtain a modified support with abundant surface weak acid and Lewis acid, which can adsorb and activate anthraquinone. Meanwhile, its steric hindrance could isolate and disperse active metals to form more active sites. The synergies between metal sites and acid sites promotes the anthraquinone hydrogenation. Furthermore, the good stability after grafting AlCl3 could attribute to the enhanced metal-support interaction inhibiting metal particles agglomeration and leaching.
    Pressure drop of structured packing in pilot column and comparison to common correlations
    Emil Madsen, Randi Neerup, Arne Gladis, Jens K. Jørsboe, Nicolas von Solms, Philip L. Fosbøl
    2023, 64(12):  281-291.  doi:10.1016/j.cjche.2023.06.009
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    Packed columns are widely used in the chemical industry such as absorption, stripping, distillation, and extraction in the production of e.g. organic chemicals, and pharmaceuticals. Pressure loss and pressure drop correlations are of special interest when it comes to the hydrodynamic properties of a column. The pressure loss across the column is of interest in the design phase when the size of the blower to drive the gas stream through the column has to be decided. The loading point and flooding point are also influenced by the pressure loss and the area of operation is determined from these points. This work examines four different correlations on pressure drop. The correlations are (i) Ergun’s equation (1952), (ii) an improved version of Ergun’s equation by Stichlmair, Bravo, and Fair (1989), (iii) an equation developed by Billet and Schultes (1999), and (iv) an equation by Rocha, Bravo, and Fair (1993). The complexity of the correlations is increasing in the mentioned order, Ergun’s equation being the simplest one. This study investigates if the more complicated correlations give better predictions to pressure drop in packed columns. This is determined by comparing the correlations to experimental data for pressure drop in a packed column with 8.2 m of structured packing using water as the liquid and atmospheric air as the gas. Seven experiments were carried out for determining the pressure drop in the column with liquid flows varying from 0 to 500 kg·h-1. At constant liquid flow, the gas flow was varied from approximately 10 to 70 kg·h-1. The pressure drop across the non-wetted column was best described by the correlation by Rocha et al. while the pressure drop for liquid flows from 100 to 500 kg·h-1 was, in general, best described by Stichlmair’s equation. For an irrigated column, the highest deviation was a predicted pressure drop 69.6% lower than measured. The best prediction was 0.1% higher than the measured. This study shows, surprisingly, that for a system of water and atmospheric air, complicated correlations on pressure drop determination do not provide better estimates than simple equations.
    Use of biopolymers in wastewater treatment: A brief review of current trends and prospects
    Ahmed M. Elgarahy, M.G. Eloffy, Eric Guibal, Huda M. Alghamdi, Khalid Z. Elwakeel
    2023, 64(12):  292-320.  doi:10.1016/j.cjche.2023.05.018
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    Indeed, polymeric materials have thrived in worldwide sectors over the last five decades due to their versatility and durability, to the point that we can no longer envisage a product that does not contain them. However, many synthetic polymers that have been produced are mostly sourced from petroleum and coal as raw materials, making them environmentally incompatible because they cannot be integrated with what is a natural recycling system. One of the most important aspects of the transition to a circular bioeconomy (CBE) is the provision of more sustainable strategies for resource and waste management. Considering the environmental consequences associated with petroleum-based polymers (PBPs), natural biopolymers, originating from biomass, can be conceived as a promising solution to gradually replace the PBPs, and address, and resolve the potential challenges and prevailing research gaps in the PBPs. The biopolymers have significant advantages over PBPs in terms of low-cost/zero-cost precursors, environmental friendliness, and user-friendliness. The present review dissects the sources, synthesis pathways, structures, characterization, and employment of biopolymers and their composites in water and wastewater treatment applications via different scenarios. Furthermore, the CBE model framework proposes potential approaches to applying CBE principles in the wastewater management sector, with a heavy emphasis on not only technology but also organizational and societal reforms. To sum up, the reliance on biopolymers can be considered a crucial tool for assessing the global progress toward CBE, as well as future environmental management and planning.