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Table of Content
28 June 2022, Volume 46 Issue 6
    Analysis of the nutation and precession of the vortex core and the influence of operating parameters in a cyclone separator
    Pan Zhang, Guanghui Chen, Weiwen Wang, Guodong Zhang, Huaming Wang
    2022, 46(6):  1-10.  doi:10.1016/j.cjche.2021.05.016
    Abstract ( 95 )   PDF (6069KB) ( 67 )  
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    Vortices motion in the anisotropic turbulent flow of cyclones makes a vital impact on flow stability and collection performance. Nevertheless, there remains a lack of clarity in the overall feature of vortices motion. In this work, a numerical analysis was conducted to clarify the complex motion of the vortex core in a cyclone separator. The validity of the numerical model was demonstrated by comparing the computational results with experimental data in the literature. As revealed by the results, the vortex core not only has a precession motion about the geometrical center axis but also does a nutation motion in the axial direction. The frequencies of the precession motions show two main peaks. And the magnitudes of the precession and nutation motions have non-uniform distributions in the cyclone. Moreover, the precession-nutation motions of the vortex cores exhibit a similar fluctuant pattern to the dust ring on the separator wall. The inlet gas velocity and the inlet solid loading show vital effects on the magnitudes and frequencies of precession and nutation motion.
    Operating limits and features of direct air capture on K2CO3/ZrO2 composite sorbent
    Vladimir S. Derevschikov, Janna V. Veselovskaya, Anton S. Shalygin, Dmitry A. Yatsenko, Andrey Z. Sheshkovas, Oleg N. Martyanov
    2022, 46(6):  11-20.  doi:10.1016/j.cjche.2021.07.005
    Abstract ( 56 )   PDF (5073KB) ( 49 )  
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    Potassium carbonate-based sorbents are prospective materials for direct air capture (DAC). In the present study, we examined and revealed the influence of the temperature swing adsorption (TSA) cycle conditions on the CO2 sorption properties of a novel aerogel-based K2CO3/ZrO2 sorbent in a DAC process. It was shown that the humidity and temperature drastically affect the sorption dynamic and sorption capacity of the sorbent. When a temperature at the sorption stage was 29 ℃ and a water vapor pressure in the feed air was 5.2 mbar (1 bar = 105 Pa), the composite material demonstrated a stable CO2 sorption capacity of 3.4% (mass). An increase in sorption temperature leads to a continuous decrease in the CO2 absorption capacity reaching a value of 0.7% (mass) at T = 80 ℃. The material showed the retention of a stable CO2 sorption capacity for many cycles at each temperature in the range. Increasing PH2O in the inlet air from 5.2 to 6.8 mbar leads to instability of CO2 sorption capacity which decreases in the course of 3 consecutive TSA cycles from 1.7% to 0.8% (mass) at T = 29 ℃. A further increase in air humidity only facilitates the deterioration of the CO2 sorption capacity of the material. A possible explanation for this phenomenon could be the filling of the porous system of the sorbent with solid reaction products and an aqueous solution of potassium salts, which leads to a significant slowdown in the CO2 diffusion in the composite sorbent grain. To investigate the regeneration step of the TSA cycle in situ, the macro ATR-FTIR (attenuated total reflection Fourier-transform infrared) spectroscopic imaging was applied for the first time. It was shown that the migration of carbonate-containing species over the surface of sorbent occurs during the thermal regeneration stage of the TSA cycle. The movement of the active component in the porous matrix of the sorbent can affect the sorption characteristics of the composite material. The revealed features make it possible to formulate the requirements and limitations that need to be taken into account for the practical implementation of the DAC process using the K2CO3/ZrO2 composite sorbent.
    Investigation on gas–solid flow regimes in a novel multistage fluidized bed
    Gongpeng Wu, Yan He
    2022, 46(6):  21-30.  doi:10.1016/j.cjche.2021.07.014
    Abstract ( 43 )   PDF (4423KB) ( 36 )  
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    Gas–solid flow regime in a novel multistage circulating fluidized bed is investigated in this study. Pressure fluctuations are first sampled from gas–solid flow systems and then are analyzed through frequency and time–frequency domain methods including power spectrum and Hilbert–Huang transform. According to the flow characteristics obtained from pressure fluctuations, it is found that the gas–solid motions in the multistage circulating fluidized bed exhibit two dominant motion peaks in low and high frequencies. Moreover, gas-cluster motions become intensive for the multistage circulating fluidized bed in comparison with the fast bed. Unlike the traditional methods, the fuzzy C-means clustering method is introduced to objectively identify flow regime in the multistage circulating fluidized bed on the basis of the flow characteristics extracted from bubbling, turbulent, fast, and multistage fluidized beds. The identification accuracy of fuzzy C-means clustering method is first verified. The identification results show that the flow regime in the multistage circulating fluidized bed is in the scope of fast flow regime under examined conditions. Moreover, the results indicate that the consistency of flow regime between two enlarged sections exists. In addition, the transition onset of fast flow regime in the multistage circulating fluidized bed is higher than that in the fast bed.
    The process and mechanism for cesium and rubidium extraction with saponified 4-tert-butyl-2-(α-methylbenzyl) phenol
    Dengke Pang, Zhihong Zhang, Yongquan Zhou, Zhenhai Fu, Quan Li, Yongming Zhang, Guangguo Wang, Zhuanfang Jing
    2022, 46(6):  31-39.  doi:10.1016/j.cjche.2021.07.001
    Abstract ( 49 )   PDF (2965KB) ( 59 )  
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    Cesium (Cs) and rubidium (Rb) separation from brine is an important and application-oriented topic. 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) has been used for Cs and Rb extraction. However, the traditional extraction technology is base and acid consumed. In the present work, an innovative process for Cs and Rb extraction with t-BAMBP is developed, which consists of saponification, extraction, scrubbing and stripping. Both infrared spectrum and electrostatic potential analysis indicate the hydrogen of phenolic hydroxyl is dissociated from t-BAMBP during saponification and the oxygen of phenolic hydroxyl is the binding site for alkali metal ions. Saponified organic phase shows an excellent extraction effect for Cs+ and Rb+. The extraction reaches equilibrium in 5 min, with 99.5% Cs+ and 46.7% Rb+ are loaded into the organic phase in the single-stage extraction. Slope method indicates the structure of the extraction complex is MOR·3ROH (M = Cs+, Rb+, K+), where the electrostatic attraction between M+ and the oxygen of phenolic hydroxyl is dominant, and the cation–π interaction has a significant effect also. The extraction complex of MOR·3ROH dissociates in the acid environment while scrubbing and stripping is completed. The Cs+ and Rb+ are separated from the mixture phase, the proton H bonds to the phenolic hydroxyl group, and the extractant is regenerated.
    Particle collision behavior and heat transfer performance in a Na2SO4 circulating fluidized bed evaporator
    Feng Jiang, Di Xu, Ruijia Li, Guopeng Qi, Xiulun Li
    2022, 46(6):  40-52.  doi:10.1016/j.cjche.2021.06.005
    Abstract ( 35 )   PDF (19563KB) ( 16 )  
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    The particle collision behavior and heat transfer performance are investigated to reveal the heat transfer enhancement and fouling prevention mechanism in a Na2SO4 circulating fluidized bed evaporator. The particle collision signals are analyzed with standard deviation by varying the amount of added particles ε (1%–3%), circulation flow velocity u (0.37–1.78 m·s-1), and heat flux q (7.29–12.14 kW·m-2). The results show that the enhancement factor reach up to 14.6% by adding polytetrafluoroethylene particles at ε = 3%, u = 1.78 m·s-1, and q = 7.29 kW·m-2. Both the standard deviation of the particle collision signal and enhancement factor increase with the increase in the amount of added particles. The standard deviation increases with the increase in circulation flow velocity; however, the enhancement factor initially decreases and then increases. The standard deviation slightly decreases with the increase in heat flux at low circulation flow velocity, but initially increases and then decreases at high circulation flow velocity. The enhancement factor decreases with the increase in heat flux. The enhancement factor in Na2SO4 solution is superior to that in water at high amount of added particles. The empirical correlation for heat transfer is established, and the model results agree well with the experimental data.
    Solvent extraction with a three-dimensional reticulated hollow-strut SiC foam microchannel reactor
    Ye Zhang, Yong Gao, Peng Wang, Duo Na, Zhenming Yang, Jinsong Zhang
    2022, 46(6):  53-62.  doi:10.1016/j.cjche.2021.05.018
    Abstract ( 60 )   PDF (11975KB) ( 38 )  
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    Recently, there has been considerable interest in the use of microchannel reactors for hydrometallurgy of rare earths (REs). Here, a novel integrated microchannel reactor based on the hollow-strut SiC foam material is presented and demonstrated to extract Ce3+ and Pr3+ using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) as the extractant. The typical three-dimensional reticulated structure of the hollow-strut SiC foam was characterized by scanning electron microscopy and X-ray micro computed tomography. Since the reactor’s structure plays a key role in fluid mixing and mass diffusion during the extraction process, the structure-performance relationship of the foam was studied by extraction experiments combined with numerical simulations. Using the foam with the optimal structure, the influence of the flow rate Q0 of the two liquid phases on the extraction efficiency η and overall volume mass transfer coefficient KLa was discussed. For both RE ions, with increasing Q0, η decreases while KLa increases. For the total flow rate of the two phases of 4 ml·min-1, the η values of Pr3+ and Ce3+ reached 98.7% and 97.0%, respectively. For the total flow rate of 36 ml·min-1 which was much higher than that of many other microchannel reactors reported in the literatures, the η values of Pr3+ and Ce3+ still reached 92.2% and 86.9%, respectively, and the KLa values of Pr3+ and Ce3+ were 0.198 and 0.161 s-1, respectively, similar to the high values reported for other microchannel reactors studied in previous work. These findings indicate that the hollow-strut SiC foam microchannel reactor is suitable for use in REs extraction.
    Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region
    Youfang Ma, Youfu Ma, Junfu Lyu, Weiye Liu
    2022, 46(6):  63-72.  doi:10.1016/j.cjche.2021.07.017
    Abstract ( 48 )   PDF (4532KB) ( 26 )  
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    The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates. However, this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow, which is corresponding to a region of low FrG (gas phase Froude number) in the flow pattern map of wet gases. In this study, the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low FrG region. By the experiment, the flow pattern transition in the downstream of single-orifice plates, as well as the effects of FrG and FrL (liquid phase Froude number) on ΦG (gas phase multiplier), were determined and compared when the upstream is in the flow pattern transition and the stratified flow region, respectively. Prediction performances were examined on the available pressure drop models. It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low FrG region with an acceptable accuracy. With a new method of correlating FrG and FrL simultaneously, new correlations were proposed for the low FrG region. Among which the modified Chisholm model shows the best prediction accuracies, with the prediction deviations of ΦG being within 7% and 3% when the upstream is in flow pattern transition and stratified flow region, respectively.
    Ni-Al mixed metal oxide with rich oxygen vacancies: CO methanation performance and density functional theory study
    Zhouxin Chang, Feng Yu, Zhisong Liu, Zijun Wang, Jiangbing Li, Bin Dai, Jinli Zhang
    2022, 46(6):  73-83.  doi:10.1016/j.cjche.2021.07.022
    Abstract ( 43 )   PDF (13266KB) ( 59 )  
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    Ni-Al mixed metal oxides have been successfully prepared by high shear mixer (HSM) and coprecipitation (CP) methods for low temperature CO methanation. In this work, Ni-Al (HSM-CP) catalyst presented small Ni crystallite size and high surface area, which all contribute to the methanation reaction at low temperature conditions. The obtained Ni-Al (HSM-CP) sample exhibited a mass of defective oxygen, thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst. Ni-Al (HSM-CP) catalyst offered the best activity with CO conversion = 100% and CH4 selectivity = 93% at 300 ℃, and the CH4 selectivity can reach 81.8% at 200 ℃. In situ Fourier transform infrared spectroscopy and density functional theory show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction, and hydrogen-assisted carbon–oxygen bond scission is more favorable.
    Identification of a sensor histidine kinase (BfcK) controlling biofilm formation in Clostridium acetobutylicum
    Dong Liu, Shikai Ge, Zhenyu Wang, Mengting Li, Wei Zhuang, Pengpeng Yang, Yong Chen, Hanjie Ying
    2022, 46(6):  84-93.  doi:10.1016/j.cjche.2021.04.024
    Abstract ( 53 )   PDF (11507KB) ( 17 )  
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    Clostridium acetobutylicum has been extensively exploited to produce biofuels and solvents and its biofilm could dramatically improve the productivities. However, genetic control of C. acetobutylicum biofilm has not been dissected so far. Here, to identify potential genes controlling C. acetobutylicum biofilm formation, over 40 gene candidates associated with extracellular matrix, cell surface, cell signaling or gene transcription, were tried to be disrupted to examine their individual impact. A total of 25 disruptants were finally obtained over years of attempts, for which biofilm and relevant phenotypes were characterized. Most of these disruptants formed robust biofilm still, or suffered both growth and biofilm defect. Only a strain with a disrupted histidine kinase gene (CA_C2730, designated bfcK in this study) abolished biofilm formation without impairing cell growth or solvent production. Further analysis revealed that bfcK could control flagellar biogenesis and cell motility at protein levels. The bfcK also appeared to repress the phosphorylation of a serine/threonine protein kinase (encoded by CA_C0404) that might negatively regulate biofilm formation. Based on these findings, possible bfcK-mediated mechanisms for biofilm formation were proposed. This is a big step toward understanding the biofilm formation in C. acetobutylicum and will help further engineering of its biofilm-based industrial processes.
    High-gravity technology intensified Knoevenagel condensation-Michael addition polymerization of poly (ethylene glycol)-poly (n-butyl cyanoacrylate) for blood-brain barrier delivery
    Xingzheng Liu, Chuanbo Fu, Manting Wang, Jiexin Wang, Haikui Zou, Yuan Le, Jianfeng Chen
    2022, 46(6):  94-103.  doi:10.1016/j.cjche.2021.05.005
    Abstract ( 49 )   PDF (4430KB) ( 48 )  
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    Poly (ethylene glycol)-poly (n-butyl cyanoacrylate) (PEG-PBCA) is a remarkable drug delivery carrier for permeating blood-brain barrier. In this work, a novel high-gravity procedure was reported to intensify Knoevenagel condensation-Michael addition polymerization of PEG-PBCA. A series of PEG-PBCA containing different block ratios were synthesized with narrow molecular weight distribution of polydispersity indexes less than 1.1. Furthermore, the reaction time reduced 60% compared to conventional stirred tank reactor process. Chemical structures of as-prepared polymers were characterized. In vitro drug delivery performance was evaluated. The cytotoxicity of PEG-PBCA to brain microvessel endothelial cells (BMVEC) decreases with the extension of the PEG chain and the shortening of the PBCA chain. The polymer cellular uptake to BMVECs was better after improving hydrophilicity by PEG block. Results of blood-brain barrier permeability demonstrated that medium length of PBCA chain and short PEG chain are favorable for hydrophobic Nile red permeation, while long PEG chain and short PBCA chain are beneficial to delivery water-soluble doxorubicin hydrochloride (Dox). The average apparent permeability coefficient increased 1.7 and 0.25 times than that of raw Nile red and Dox, respectively. High-gravity intensified condensation polymerization should have great potential in brain drug delivery system.
    A core–shell Ni/SiO2@TiO2 catalyst for highly selective one-step synthesis of 2-propylheptanol from n-pentanal
    Hualiang An, Rui Wang, Wenhao Wang, Daolai Sun, Xinqiang Zhao, Yanji Wang
    2022, 46(6):  104-112.  doi:10.1016/j.cjche.2021.05.042
    Abstract ( 53 )   PDF (5083KB) ( 56 )  
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    One-step synthesis of 2-propylheptanol (2-PH) from n-pentanal via a reaction integration of n-pentanal self-condensation and successive hydrogenation is of great significance for it can simplify process flow and reduce energy consumption. The key to promotion of 2-PH selectivity is to enhance the competitiveness of n-pentanal self-condensation with respect to its direct hydrogenation. For this purpose, a core–shell structured Ni/SiO2@TiO2 catalyst was designed and prepared. With the precise architecture of this core–shell structured catalyst, n-pentanal can be firstly in contact with TiO2 to 2-propyl-2-heptenal (2-PHEA) while the direct hydrogenation to n-pentanol can be effectively inhibited, and then 2-PHEA diffuses into the core of Ni/SiO2 and is hydrogenated to 2-PH. The spatial threshold of the core–shell catalyst significantly enhanced its catalytic performance; a 2-PH selectivity of 77.9% was reached with a 100% n-pentanal conversion. The 2-PH selectivity is much higher than that obtained by employing Ni/TiO2 catalyst. Furthermore, the reaction kinetics of one-step synthesis of 2-PH from n-pentanal catalyzed by Ni/SiO2@TiO2 was studied and its kinetic model was established which is useful for reactor design and scale-up.
    Promotional effect for SCR of NO with CO over MnOx-doped Fe3O4 nanoparticles derived from metal-organic frameworks
    Yu Zhang, Ling Zhao, Ziang Chen, Xinyong Li
    2022, 46(6):  113-125.  doi:10.1016/j.cjche.2021.03.043
    Abstract ( 44 )   PDF (15682KB) ( 195 )  
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    MnOx-Fe3O4 nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H2-TPR and O2-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O2- species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway.
    Production of aromatic hydrocarbons by co-cracking of bio-oil and ethanol over Ga2O3/HZSM-5 catalysts
    Xing Zhang, Jingfeng Wu, Junhao Chen, Liang Lu, Lingjun Zhu, Shurong Wang
    2022, 46(6):  126-133.  doi:10.1016/j.cjche.2021.07.011
    Abstract ( 25 )   PDF (5203KB) ( 50 )  
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    The catalytic cracking of bio-oil is important to produce aromatic hydrocarbons, which can partially replace gasoline or diesel to greatly reduce carbon emissions from transportation. To further promote the formation of aromatic hydrocarbons, this work studied the effects of the preparation method and the acid strength of Ga2O3/HZSM-5 on catalytic cracking of the bio-oil distilled fraction systematically. The preparation method of Ga2O3/HZSM-5 had an important effect on its catalytic activity: the Ga2O3/HZSM-5 prepared by physical mixing showed the low dispersion of active phases and poor pore structure, resulting in its insufficient activity and severe coke deposition; the Ga2O3/HZSM-5 prepared by precipitation exhibited the higher activity, while many polycyclic aromatic hydrocarbons unfavorable for the subsequent utilization were in the oil phase; the Ga2O3/HZSM-5 prepared by impregnation showed the highest activity and 35.5% (mass) selectivity of the oil phase, including 80.3% monocyclic aromatic hydrocarbons and 12.0% polycyclic aromatic hydrocarbons. The Brønsted acidity of Ga2O3/HZSM-5 decreased with Si/Al ratio, leading to the decline in reactant conversion, oil phase selectivity and quality. Meanwhile, the polymerization between monocyclic aromatic hydrocarbons and oxygenates was promoted to produce many polycyclic aromatic hydrocarbons and even coke, causing catalyst deactivation.
    Emergy evaluation of aromatics production from methanol and naphtha
    Siyue Ren, Xiao Feng
    2022, 46(6):  134-141.  doi:10.1016/j.cjche.2021.04.025
    Abstract ( 47 )   PDF (2907KB) ( 109 )  
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    Aromatics are traditionally produced by the catalytic reforming of naphtha. However, with the demand of aromatics increasing and the reserves of petroleum resources declining, measures should be made to reduce the dependence of aromatics production on petroleum resources. Methanol-to-aromatics is proved to be an effective way to replace traditional naphtha-to-aromatics path. In order to compare the economic and environmental performance of aromatics production from naphtha and methanol, this paper carries out an emergy evaluation for each system by sorting out the simulation and literature data. Based on the emergy data collected, the emergy indices of each system are calculated. The results show that the sustainabilities of methanol-to-aromatics systems are higher than that of the naphtha-to-aromatics system, indicating the advantages of aromatics production from methanol. Among the methanol-to-aromatics systems, the aromatics from biomass-methanol system has the highest sustainability, indicating that the biomass based methanol-to-aromatics system is worth promoting. The sustainability indexes of methanol-to-aromatics systems based on coal and coke oven gas are less than 1, which means unsustainable. Meanwhile, the sustainability of natural gas based system is slightly higher than 1. The economic and environmental benefits of these systems can be optimized by improving resource utilization and reducing investment costs. Furthermore, the combination of different raw materials for methanol production should be considered.
    Hydrothermal preparation of Nb-doped NaTaO3 with enhanced photocatalytic activity for removal of organic dye
    Hao Zhou, Qi Yin
    2022, 46(6):  142-149.  doi:10.1016/j.cjche.2021.05.037
    Abstract ( 21 )   PDF (4326KB) ( 82 )  
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    The construction of efficient photocatalysts has received much attention in wastewater treatment. In this study, Nb-doped NaTaO3 was prepared with different doping ratio by a facile hydrothermal method. The prepared catalysts were analyzed by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) theory, ultraviolet–visible diffuse reflectance spectroscopy. Then the synthesized catalysts were employed to degrade a model pollutant, methylene blue (MB), under a 250 W mercury lamp. The characterization tests confirm that Nb was successfully doped into the crystal structure of NaTaO3 and the modified NaNbxTa1-xO3 (x is the doping ratio; x = 0.25, 0.5, 0.75) samples were formed, which were in regular cubic shapes just like pure NaTaO3. The synthesized NaNbxTa1-xO3 (x = 0.25, 0.5, 0.75) had improved specific surface area and narrowed band gaps compared with pure NaTaO3. In photocatalytic degradation experiments, NaNb0.75Ta0.25O3 presented the best photocatalytic activity ascribed to the narrow band gap and the high surface area, degradating 95.7% of MB after 180 min of reaction, which was even twice the ability of pure NaTaO3. Besides, the effects of possible inorganic anions and cations in wastewater on photocatalytic degradation were investigated. Electron spin resonance (ESR) tests and capture experiments were also conducted and a possible photocatalytic mechanism was proposed. This work provides a direction for constructing superior NaTaO3-based photocatalysts to be widely utilized in environmental protection.
    Synergistic effects of phosphoric acid modified hydrochar and coal gangue-based zeolite on bioavailability and accumulation of cadmium and lead in contaminated soil
    Qilong Ge, Qi Tian, Sufang Wang, Fang Zhu
    2022, 46(6):  150-160.  doi:10.1016/j.cjche.2021.03.029
    Abstract ( 38 )   PDF (5052KB) ( 23 )  
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    In this paper, a novel compound was developed by mixing H3PO4-modified cauliflower leaves hydrochar (CLH) and coal gangue-based Na-X zeolite (ZL). An alkaline soil contaminated with cadmium (Cd) and lead (Pb) was amended through the individual and synergistic application of CLH and ZL (1%CLH, 2%CLH, 1%ZL, 2%ZL and 1%CLH + 1%ZL), and Chinese cabbage was grown on it. Individual application of CLH was superior to ZL on decreasing the pH of alkaline soil and increasing soil available phosphorus (Olsen-P) and soil organic matter (SOM). In contrast, their combined application significantly improved the soil cation exchange capacity (CEC). Besides, the 1%CLH + 1%ZL was the most efficient treatment in decreasing diethylenetriamine pentaacetate (DTPA)-extractable Cd/Pb and concentrations of these two metals in cabbage root and shoot. Their synergistic application could better increase Cd and Pb immobilization and cabbage yield than their alone application. Furthermore, the immobilization of Pb for all treatments was higher than that of Cd. The synergistic immobilization mechanism of CLH and ZL reflected that the CLH precipitated and complexed with these two metals, which may block the pores of hydrochar or wrap on the surface of hydrochar. So the continuous adsorption and complexation were prevented. Nevertheless, ZL could probably alleviate this obstacle. This finding provides helpful information about using CLH combined with ZL as a soil stabilizer to immobilize heavy metals in contaminated alkaline soil.
    Polyoxymethylene dimethyl ethers synthesis from methanol and formaldehyde solution over one-pot synthesized spherical mesoporous sulfated zirconia
    Xiangjun Li, Shujun Li, Xiaoping Wang, Muhammad Asif Nawaz, Dianhua Liu
    2022, 46(6):  161-172.  doi:10.1016/j.cjche.2021.04.022
    Abstract ( 37 )   PDF (10530KB) ( 12 )  
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    The synthesis of polyoxymethylene dimethyl ethers as an ideal diesel fuel additive is the current hot topic of modern petrochemical industry for their expedient properties in mitigating air pollutants emission during combustion. In this work, a series of spherical sulfated zirconia catalysts were prepared by a one-pot hydrothermal method assisted with surfactant cetyltrimethylammonium bromide (CTAB). The prepared sulfated zirconia catalysts were used to catalyze PODEn synthesis from methanol and formaldehyde solution. Various characterization (XRD, BET, SEM, TGA, NH3-TPD, FTIR, and Py-IR) were employed to elaborate the structure–activity relationship of the studied catalytic system. The results demonstrated that S/Zr molar ratio in precursor solution played an effective role on catalyst morphology and acidic properties, where the weak Brønsted acid sites and strong Lewis acid sites were favorable to the conversion of methanol and formation of long-chain PODEn, respectively. The reaction parameters such as catalyst amount, molar ratio of FA/MeOH, reaction time, temperature and pressure were optimized. The speculated reaction pathway for PODEn synthesis was proposed based on the synergy of Brønsted and Lewis acid sites, which suggested that Brønsted and Lewis acid sites might be advantageous to the activation of polyoxymethylene hemiformals [CH3(OCH2)nOH] and methylene glycol (HOCH2OH), respectively.
    Comparative catalytic study on butene/isobutane alkylation over LaX and CeX zeolites: The influence of calcination atmosphere
    Zhiqiang Yang, Ruirui Zhang, Honghua Zhang, Hongguo Tang, Ruixia Liu, Suojiang Zhang
    2022, 46(6):  173-183.  doi:10.1016/j.cjche.2021.05.041
    Abstract ( 36 )   PDF (4721KB) ( 20 )  
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    Lanthanum-containing (LaX) and cerium-containing X zeolites (CeX) were prepared by a double-exchange, double-calcination method. By changing the calcination atmospheres between nitrogen and air, the CeIV contents in CeX zeolites were adjusted and their impacts on physicochemical properties and catalytic performance in isobutane alkylation were established. The crystallinity of CeX zeolite was found to be negatively correlated with the CeIV content. This i s believed to be due to the water formed during the oxidation of CeIII, which facilitates the framework dealumination. As a consequence, calcining in air resulted in a great elimination of strong Brønsted acid sites while under nitrogen protection, this phenomenon was mostly hindered and the sample's acidity was preserved. When tested in a continuously flowed slurry reactor, the catalyst lifetime for isobutane alkylation was found to be linearly related to the strong Brønsted acid concentration. In addition, Ce3+ was found more benefit for the hydride transfer compared with La3+, which is ascribed to the stronger polarization effect on the CH bond of isobutane. Moreover, the decline of hydride transfer activity can be slowed down by the catalytic cracking of the bulky molecules. Based on the product distribution, a new catalytic cycle of dimethylhexanes (DMHs) involving a direct formation of isobutene rather than tert-butyl carbocation was proposed in isobutane alkylation.
    Insight into SO2 poisoning and regeneration of one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NOx by NH3
    Xin Yong, Hong Chen, Huawang Zhao, Miao Wei, Yingnan Zhao, Yongdan Li
    2022, 46(6):  184-193.  doi:10.1016/j.cjche.2021.06.012
    Abstract ( 36 )   PDF (7586KB) ( 17 )  
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    The effects of SO2 on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NOx by NH3 were examined. The addition of SO2 inhibited NOx conversion significantly below 300 ℃, while no effect on NOx conversion was observed above 300 ℃. TGA, TPD, and XPS results showed that the deactivation was caused by the formation of (NH4)2SO4, SO2 chemisorption on the isolated Cu2+ ion sites, as well as the formation of CuSO4-like species. Among them, the site-blocking effect of (NH4)2SO4 on Cu2+ was the primary reason for deactivation. Fortunately, 89% of deNOx activity of the poisoned catalyst was recovered after thermal treatment at 500 ℃ in air, where (NH4)2SO4 was completely decomposed. The activity was further recovered with regeneration temperature increasing to 600 ℃, removing the adsorbed SO2 on the Cu2+ sites. The regeneration at 600 ℃ could not recover the activity completely, because of the high stability of CuSO4-like species.
    Superhigh selective capture of volatile organic compounds exploiting cigarette butts-derived engineering carbonaceous adsorbent
    Wenjian Zhu, Xuhua Shen, Rui Ou, Manoj Murugesan, Aihua Yuan, Jianfeng Liu, Xiaocai Hu, Zhen Yang, Ming Shen, Fu Yang
    2022, 46(6):  194-206.  doi:10.1016/j.cjche.2021.01.012
    Abstract ( 45 )   PDF (9301KB) ( 36 )  
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    Herein, we develop cost-efficient superhigh-performance of engineering carbonaceous adsorbent from cigarette butts using combined wet-impregnated and re-dispersed method of KOH, which optimizes the implant approach of activator, breaking the restriction of selective capture of toluene using traditional activated carbon. The Brunauer-Emmett-Teller (BET) surface area and pore volume of targeted adsorbent can attain 3088 m2·g-1 and 1.61 cm3·g-1, respectively, by optimizing the temperature-dependent synthetic factor effect of the adsorbent. The adsorption capacity of resultant adsorbent for presenting volatile benzene and toluene shows a positive correlation with increasing carbonization temperature of carbon precursor. Besides, we demonstrated the unsmoked and smoked butts derived adsorbents afford feeble difference in saturated adsorbed capacity of volatile organic compounds (VOCs). The highest adsorption capacity of sample CF-800 for benzene and toluene in CF group is as high as 1268.1 and 1181.6 mg·g-1 respectively, slightly higher than that of sample UF-800, but far outperforming reported other adsorbents. The predicted adsorption selectivity of CF-800 and UF-800 for C7H8/H2O (g) using the DIH (difference of isosteric heats) equation reach up to ca. 3800 and 7500 respectively, indicating the weak adsorbability of water vapor on the developed adsorbent and greater superiority of the smoked butts derived adsorbents in selective capture of VOCs at low relative humidity in the competitive adsorption process for practical mixed VOCs.
    Fabrication of nickel oxide functionalized zeolite USY composite as a promising adsorbent for CO2 capture
    Jipeng Dong, Fei Wang, Guanghui Chen, Shougui Wang, Cailin Ji, Fei Gao
    2022, 46(6):  207-213.  doi:10.1016/j.cjche.2021.10.011
    Abstract ( 36 )   PDF (1544KB) ( 24 )  
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    Adsorption process is considered to be the most promising alternative for the CO2 capture to the traditional energy-intensive amine absorption process, and the development of feasible and efficient CO2 adsorbents is still a challenge. In this work, the NiO@USY (ultrastable Y) composites with different NiO loadings were prepared for the CO2 adsorption using Ni(NO3)2 as the precursor. The composites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption–desorption test, scanning electron microscopy analysis, and thermogravimetric analysis, and were evaluated for the CO2 adsorption capacity, CO2/N2 adsorption selectivity and CO2 cycle adsorption capacity. The characterization results show that after the activation at 423 K, the Ni(NO3)2 species were well dispersed into the surface of zeolite USY, and after the further activation at 823 K, Ni(NO3)2 could be converted into highly dispersed NiO. The adsorption results show that the presence of the active component NiO plays an important role in improving the CO2 adsorption performance, and the NiO@USY composite with a NiO loading of 1.5 mmol·g-1 USY support displays a high adsorption capacity and adsorption selectivity for CO2, and shows a good cycle stability. In addition, the Clausius–Clapeyron equation was used to evaluate the isosteric heat of adsorption of CO2 on the NiO(1.5)@USY composite, and the heat of adsorption was 17.39–38.34 kJ·mol-1.
    Formation characteristics of Taylor bubbles in a T-junction microchannel with chemical absorption
    Yaran Yin, Xianming Zhang, Chunying Zhu, Taotao Fu, Youguang Ma
    2022, 46(6):  214-222.  doi:10.1016/j.cjche.2021.06.002
    Abstract ( 32 )   PDF (5680KB) ( 34 )  
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    This study focuses on the effect of chemical absorption on the formation dynamic characteristics and initial length of Taylor bubbles. The temporal evolutions of neck width and length of gaseous thread and initial length with and without chemical absorption were investigated with the Capillary number and Hatta number between 0.0010–0.0073 and 1.8–5.8 respectively. The squeezing regime with typical three stages, expansion, squeezing and pinch off is observed for both two processes. Compared with the non-absorption process, the increase of formation time in the chemical absorption process arises mainly from the expansion stage, and the decrease of initial length is from the necking stage. In addition, the temporal length evolution satisfies the power-law scale with the same exponent but a smaller pre-exponential factor. The correlations of neck width for stage transition and initial length with Hatta number demonstrate the enhancement effect of chemical absorption on bubble formation dynamics and initial length at relatively high chemical reaction rates and long formation time. This study provides insight into the bubble formation mechanism and helps to regulate the bubble initial size with chemical absorption.
    Preparation of novel magnetic nanoparticles as draw solutes in forward osmosis desalination
    Dongze Ma, Ye Tian, Tiefei He, Xiaobiao Zhu
    2022, 46(6):  223-230.  doi:10.1016/j.cjche.2021.07.013
    Abstract ( 34 )   PDF (6444KB) ( 33 )  
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    Novel magnetic nanoparticles (MNPs), Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2, were prepared by loading different amounts of SiO2 or/and PEG-(COOH)2 onto Fe3O4 nanoparticles, and their feasibility to be used as forward osmosis (FO) draw solutes was investigated. The characterization of the materials showed that, compared to normal Fe3O4 nanoparticles, the modified MNPs exhibited enhanced dispersity and high osmotic pressure in aqueous solution. The FO experiment indicated that the synthesized draw solutes could obtain a water flux as high as 10 L·m-2·h-1 with an aquaporin FO membrane. The optimal concentration of the added tetraethyl orthosilicate was 30% during the synthesis. The novel MNPs could be easily recovered from draw solutions by magnetic field, and the recovery rate of Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2 was 83.95% and 63.37%, respectively. Moreover, after 5 recycles of reuse, the water flux of Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2 as draw solutes still remained 64.36% and 85.26%, respectively. The experimental results demonstrated that the synthesized core–shell magnetic nanoparticles are promising draw solutes, and the Fe3O4@SiO2@PEG-(COOH)2 was more suitable to be used as draw solute in FO process.
    Monte Carlo simulation of sequential structure control of AN-MA-IA aqueous copolymerization by different operation modes
    Tong Qin, Zhenhao Xi, Ling Zhao, Weikang Yuan
    2022, 46(6):  231-242.  doi:10.1016/j.cjche.2021.06.022
    Abstract ( 32 )   PDF (7073KB) ( 16 )  
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    The regulation of polyacrylonitrile (PAN) copolymer composition and sequence structure is the precondition for producing high-quality carbon fiber high quality. In this work, the sequential structure control of acrylonitrile (AN), methyl acrylate (MA) and itaconic acid (IA) aqueous copolymerization was investigated by Monte Carlo (MC) simulation. The parameters used in Monte Carlo were optimized via machine learning (ML) and genetic algorithms (GA) using the experimental data from batch copolymerization. The results reveal that it is difficult to control the aqueous copolymerization to obtain PAN copolymer with uniform sequence structure by batch polymerization with one-time feeding. By contrary, it is found that the PAN copolymer with uniform composition and sequence structure can be obtained by adjusting IA feeding quantity in each reactor of a train of five CSTRs. Hopefully, the results obtained in this work can provide valuable information for the understanding and optimization of AN copolymerization process to obtain high-quality PAN copolymer precursor.
    Rapid velocity reduction and drift potential assessment of off-nozzle pesticide droplets
    Shidong Xue, Jingkun Han, Xi Xi, Junyi Zhao, Zhong Lan, Rongfu Wen, Xuehu Ma
    2022, 46(6):  243-254.  doi:10.1016/j.cjche.2021.06.011
    Abstract ( 29 )   PDF (8919KB) ( 39 )  
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    The droplet velocity and diameter significantly affect both the spatial drift loss and the interfacial deposition behaviors, thus determining the ultimate utilization efficiency during pesticide spraying. Investigating the spatial velocity and diameter evolutions can reveal the mechanism of drift loss and guide to design regulation strategy. Here, we explored the spatial velocity distribution of droplets after leaving the nozzle by particle image velocimetry technology and particle tracking model, considering that the effect of nozzle configuration and the air velocity. It shows that all droplets decelerate rapidly with the velocity attenuation ratio ranging from 50% to 80% within the region of 200 mm below the nozzle. The spatial velocity evolution differences between droplets in crossflow are determined by the competition of vertical drag force and net gravity, and the drag force sharply increases as the droplet diameter decreases, especially for that smaller than 150 μm. Based on the spatial evolution differences of the droplet velocity and diameter, a functional adjuvant was added to the liquid for improving the diameter distribution. And the drift loss was significantly reduced due to the reduction of the proportion of easily drifting droplets.
    The motion mechanism and characteristic of bubble in a pseudo-2D tapered fluidized bed
    Wenjuan Bai, Dianming Chu, Kuanxin Tang, Lei Geng, Yan Li, Yan He
    2022, 46(6):  255-270.  doi:10.1016/j.cjche.2021.06.024
    Abstract ( 31 )   PDF (7310KB) ( 14 )  
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    The different carbon nanotube (CNT) particles (@A and @V) were bed materials in the pseudo-2D tapered fluidized bed (TFB) with/without a distributor. A detailed investigation of the motion mechanism of bubbles was carried out. The high-speed photography and image analysis techniques were used to study bubble characteristic and mixing behavior in the tapered angle of TFB without a distributor. The fractal analysis method was used to analyze the degree of particles movement. Results showed that an S-shaped motion trajectory of bubbles was captured in the bed of @V particles. The population of observational bubbles in the bed of @V particles was more than that of @A particles, and the bubble size was smaller in the bed of @V particles than that of @A particles. The motion mechanism of bubbles had been shown to be related to bed materials and initial bed height in terms of analysis and comparison of bubble diameter, bubble aspect ratio and bubble shape factor. Importantly, compared to the TFB with a distributor, the TFB without a distributor had been proved to be beneficial to the CNT fluidization according to the study of bubble characteristic and the degree of the particle movement. Additionally, it was found that the mixing behavior of @V particles was better than @A particles in the tapered angle of TFB without a distributor.
    Mechanism analysis of solvent selectivity and energy-saving optimization in vapor recompression-assisted extractive distillation for separation of binary azeotrope
    Xiaomin Qiu, Yuanyuan Shen, Zhengkun Hou, Qi Wang, Zhaoyou Zhu, Yinglong Wang, Jingwei Yang, Jun Gao
    2022, 46(6):  271-279.  doi:10.1016/j.cjche.2021.06.010
    Abstract ( 57 )   PDF (4962KB) ( 119 )  
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    Octane and p-xylene are common components in crude gasoline, so their separation process is very important in petroleum industry. The azeotrope and near azeotrope are often separated by extractive distillation in industry, which can realize the recovery and utilization of resources. In this work, the vapor–liquid equilibrium experiment was used to obtain the vapor–liquid equilibrium properties of the difficult separation system, and on this basis, the solvent extraction mechanism was studied. The mechanism of solvent separation plays a guiding role in selecting suitable solvents for industrial separation. The interaction energy, bond length and charge density distribution of p-xylene with solvent are calculated by quantum chemistry method. The quantum chemistry calculation results and experiment results showed that N-formylmorpholine is the best solvent among the alternative solvents in the work. This work provides an effective and complete solvent screening process from phase equilibrium experiments to quantum chemical calculation. An extractive distillation simulation process with N-formylmorpholine as solvent is designed to separate octane and p-xylene. In addition, the feasibility and effectiveness of the intensified vapor recompression assisted extraction distillation are also discussed. In the extractive distillation process, the vapor recompression-assisted extraction distillation process is globally optimal. Compared with basic process, the total annual cost can be reduced by 43.2%. This study provides theoretical guidance for extractive distillation separation technology and solvent selection.
    Scalable synthesis of Na3V2(PO4)3/C with high safety and ultrahigh-rate performance for sodium-ion batteries
    Guijia Cui, Hong Wang, Fengping Yu, Haiying Che, Xiaozhen Liao, Linsen Li, Weimin Yang, Zifeng Ma
    2022, 46(6):  280-286.  doi:10.1016/j.cjche.2021.06.008
    Abstract ( 47 )   PDF (8397KB) ( 19 )  
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    NASICON-type Na3V2(PO4)3 is a promising electrode material for developing advanced sodium-ion batteries. Preparing Na3V2(PO4)3 with good performance by a cost-effective and large-scale method is significant for industrial applications. In this work, a porous Na3V2(PO4)3/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method. The Na3V2(PO4)3/C cathode displayed specific capacities of 113.4 mAh·g-1, 107.0 mAh·g-1 and 87.1 mAh·g-1 at 0.1 C, 1 C and 10 C, respectively. For the first time, the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na3V2(PO4)3/C electrodes are successfully fabricated. The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83% at 0 ℃ owing to the rapid sodium ion migration ability and structural stability of Na3V2(PO4)3/C. Moreover, the thermal runaway features are revealed by accelerating rate calorimetry (ARC) test for the first time. Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries. Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na3V2(PO4)3/C have a prospect of practical application in high safety requirement fields.