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Table of Content
28 July 2022, Volume 47 Issue 7
    Chemical reduction-induced fabrication of graphene hybrid fibers for energy-dense wire-shaped supercapacitors
    Minjie Shi, Hangtian Zhu, Cheng Yang, Jing Xu, Chao Yan
    2022, 47(7):  1-10.  doi:10.1016/j.cjche.2021.05.045
    Abstract ( 163 )   PDF (14792KB) ( 380 )  
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    The emerging one-dimensional wire-shaped supercapacitors (SCs) with structural advantages of low mass/volume structural advantages hold great interests in wearable electronic engineering. Although graphene fiber (GF) has full of vigor and tremendous potentiality as promising linear electrodefor wire-shaped SCs, simultaneously achieving its facile fabrication process and satisfactory electrochemical performance still remains challenging to date. Herein, two novel types of graphene hybrid fibers, namely ferroferric oxide dots (FODs)@GF and N-doped carbon polyhedrons (NCPs)@GF, have been proposed via a simple and efficient chemical reduction-induced fabrication. Synergistically coupling the electroactive units (FODs and NCPs) with conductive graphene nanosheets endows the fiber-shaped architecture with boosted electrochemical activity, high flexibility and structural integrity. The resultant FODs@GF and NCPs@GF hybrid fibers as linear electrodes both exhibit excellent electrochemical behaviors, including large volumetric specific capacitance, good rate capability, as well as favorable electrochemical kinetics in ionic liquid electrolyte. Based on such two linear electrodes and ionogel electrolyte, a high-performance wire-shaped SC is effectively assembled with ultrahigh volumetric energy density (26.9 mW·h·cm-3), volumetric power density (4900 mW·cm-3) and strong durability over 10,000 cycles under straight/bending states. Furthermore, the assembled wire-shaped SC with excellent flexibility and weavability acts as efficient energy storage device for the application in wearable electronics.
    Preparation of aldoxime through direct ammoximation using titanium silicalite-1 catalyst
    Zhigang Xu, Xiongfei Jin, Tao Zhou, Qian Zou, Longcheng Liu, zhongbo Wang, Hanbing Sheng, Huasheng Xie
    2022, 47(7):  11-17.  doi:10.1016/j.cjche.2021.08.016
    Abstract ( 82 )   PDF (677KB) ( 73 )  
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    The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1 (TS-1) catalyst. The effect of reaction parameters on the yield of the product was studied, which include reaction temperature, reaction time, molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde. The influence of the amount of catalyst on the reaction results was also investigated. The maximum 5-isooctyl salicylaldoxime yield of 98.76% was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6, the reaction temperature of 70℃, the amount of TS-1 of 17.5 g·mol-1 (5-isooctyl salicylaldehyde), and the feeding time of 2 h. This method has the mild reaction conditions and avoids the shortcomings of traditional methods. Moreover, useless inorganic salts by-products are avoided, and there is no environmental pollution.
    Efficient synthesis of tyrosol from L-tyrosine via heterologous Ehrlich pathway in Escherichia coli
    Xiaobo Ruan, Sheng Zhang, Wei Song, Jia Liu, Xiulai Chen, Liming Liu, Jing Wu
    2022, 47(7):  18-30.  doi:10.1016/j.cjche.2021.05.026
    Abstract ( 38 )   PDF (7581KB) ( 39 )  
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    For the efficient conversion of L-tyrosine (L-Tyr) to tyrosol, which is an aromatic compound widely used in the pharmaceutical and chemical industries, a novel four-enzyme cascade pathway based on the Ehrlich pathway of Saccharomyces cerevisiae was designed and reconstructed in Escherichia coli. Then, the expression levels of the relevant enzymes were coordinated using a modular approach and gene duplication after the identification of the pyruvate decarboxylase from Candida tropicalis (CtPDC) as the rate-limiting enzymatic step. In situ product removal (ISPR) strategy with XAD4 resins was explored to avoid product inhibition and further improve tyrosol yield. As a result, the titer and conversion rate of tyrosol obtained were 35.7 g·L-1 and 93.6%, respectively, in a 3-L bioreactor. Results presented here provide a potential enzymatic process for industrial production of tyrosol from cheap amino acids.
    N, P co-doped porous graphene with high electrochemical properties obtained via the laser induction of cellulose nanofibrils
    Jie Wei, Weiwei Yang, Shuai Jia, Jie Wei, Ziqiang Shao
    2022, 47(7):  31-38.  doi:10.1016/j.cjche.2021.07.025
    Abstract ( 36 )   PDF (12263KB) ( 27 )  
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    Cellulose and its derivatives are natural materials with high carbon contents, but it is challenging to convert their carbon into high value-added carbonaceous materials (e.g., graphene). Here, an approach to convert the carbon in cellulose into N, P co-doped porous graphene (LIG) materials via laser induction is proposed. Cellulose nanofibrils (CNFs), a cellulose derivative with high dispersion uniformity and abundant surface hydroxyl groups, were easily formed on a bulk substrate (thickness ≥ 5 mm) containing ammonium polyphosphate (APP). Then, a 10.6 μm CO2 laser was used to scribe for 1-5 passes on the CNFs/APP substrate under an ambient environment to produce N, P co-doped porous LIG. Upon increasing the number of laser scribing passes, the IG/ID of LIG first increased and then decreased, reaching a maximum of 1.68 at 4 passes. The good pore structure and low resistance also showed that 4 laser passes were ideal. Besides, the N, P co-doped LIG also showed excellent electrochemical performance, with a specific capacitance of 221.4 F?g-1 and capacitance retention of 89.9%. This method exploits the advantages of nanocellulose and overcomes the difficulties associated with directly compounding cellulosic materials, providing a method for the further development of biomass nanomaterials.
    Two-stage cyclic ammonium sulfate roasting and leaching of extracting vanadium and titanium from vanadium slag
    Qing Lin, Guoquan Zhang, Kun Wang, Dongmei Luo, Siyang Tang, Hairong Yue
    2022, 47(7):  39-47.  doi:10.1016/j.cjche.2021.05.035
    Abstract ( 39 )   PDF (9757KB) ( 26 )  
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    Compared with traditional sodium or calcification roasting process for vanadium extraction from raw vanadium slag (V-slag), ammonium sulfate (AS) roasting could reduce about 470℃ roasting temperature and avoid Cl2, HCl, sodium-containing waste-water and waste gypsum discharging. To reduce the amount of AS added in vanadium extraction process, an efficient AS two-stage cyclic roasting and acid leaching process was proposed. The result of TG analysis indicates V-slag could be decomposed in 275-380℃ using AS roasting process. Using 2.03:1 total mass ratio of AS to V-slag, 90.86% V and 80.54% Ti could be extracted after 380℃ roasting for 30 min and 8% initial concentration of H2SO4 leaching at 70℃ for 100 min. XRD analysis indicates V-containing spinel phase in the 1st stage leaching residue would be efficiently decomposed by the cyclic two-stage roasting and leaching process. Furthermore, the valence of V(III) in raw V-slag was not changed after the 1st AS roasting stage, but a part of V(III) in the 1st leaching residue was oxidized to V(V) after 2nd roasting process.
    Conjugation of a zwitterionic polymer with dimethyl chains to lipase significantly increases the enzyme activity and stability
    Chunyu Zhang, Yan Sun, Xiaoyan Dong
    2022, 47(7):  48-53.  doi:10.1016/j.cjche.2021.04.023
    Abstract ( 37 )   PDF (2075KB) ( 354 )  
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    Enzyme-polymer conjugates are complex molecules with great practical significance. This work was designed to develop a novel enzyme-polymer conjugate by covalently coupling a zwitterionic polymer with side dimethyl chains (pID) to Candida rugosa lipase (CRL) via the reaction between the anhydrides of polymer chains with the amino groups of the enzyme. The resulting two CRL-pID conjugates with different pID grafting densities were investigated in term of the catalytic activity, stability and structural changes. In comparison with native CRL, both the CRL conjugates displayed 2.2 times higher activity than the native enzyme, and showed an increase in the maximum reaction rate (Vmax) and a decrease in the Michaelis constant (Km), thus resulting in about three-fold increases in the catalytic efficiency (kcat/Km). These are mainly attributed to the activation of lipase by the hydrophobic alky side chains. Moreover, the thermostability and pH tolerance of the lipase conjugates were significantly enhanced due to the stabilizing effect of the zwitterion moieties. For instance, a five-fold increase of the enzyme half-life at 50℃ for the high-pID conjugated CRL was observed. Spectroscopic studies reveal that the pID conjugation protected the enzyme in the changes in its microenvironment and conformation, well correlating with enhanced activity and stability of lipase conjugates. The findings indicate that enzyme conjugation to the zwitterionic polymer is promising for improving enzyme performance and deserves further development.
    Cycle temporal algorithm-based multivariate statistical methods for fault diagnosis in chemical processes
    Jiaxin Zhang, Wenjia Luo, Yiyang Dai, Yuman Yao
    2022, 47(7):  54-70.  doi:10.1016/j.cjche.2021.03.058
    Abstract ( 30 )   PDF (15931KB) ( 18 )  
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    Multivariate statistical process monitoring methods are often used in chemical process fault diagnosis. In this article, (I) the cycle temporal algorithm (CTA) combined with the dynamic kernel principal component analysis (DKPCA) and the multiway dynamic kernel principal component analysis (MDKPCA) fault detection algorithms are proposed, which are used for continuous and batch process fault detections, respectively. In addition, (II) a fault variable identification model based on reconstructed-based contribution (RBC) model that paves the way for determining the cause of the fault are proposed. The proposed fault diagnosis model was applied to Tennessee Eastman (TE) process and penicillin fermentation process for fault diagnosis. And compare with other fault diagnosis methods. The results show that the proposed method has better detection effects than other methods. Finally, the reconstruction-based contribution (RBC) model method is used to accurately locate the root cause of the fault and determine the fault path.
    Enhancement of acetylene and ethylene yields in partially decoupled oxidation of ethane by changing the composition of heat carrier
    Tianpeng LiZhou, Jiajia Luo, Tiefeng Wang
    2022, 47(7):  71-78.  doi:10.1016/j.cjche.2021.07.012
    Abstract ( 42 )   PDF (1645KB) ( 34 )  
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    In our previous work, a partially decoupled process (PDP) was proposed for efficient conversion of ethane to increase the ethylene yield and a new structural reactor called forward-impinging-back reactor (FIB) was proposed for scale-up. In this work, the influence of changing the composition and temperature of the heat carrier was investigated by simulations with detailed chemistry to further increase of the C2 (C2H2 + C2H4) yield in the PDP of ethane. At ideal mixing conditions, the C2 yield is 75.3% without steam addition and it is 82.9% at steam addition ratio of β=1.4. In comparison, the C2 yield in an FIB reactor is 62.4% without steam addition and it increases to 78.5% with steam addition (β=1.4). The requirement of high mixing efficiency is diminished by steam addition, which is favorable for reactor scale-up.
    Study on the solid–liquid suspension behavior in a tank stirred by the long-short blades impeller
    Zewen Chen, Yongjun Wu, Jian Wang, Peicheng Luo
    2022, 47(7):  79-88.  doi:10.1016/j.cjche.2021.06.009
    Abstract ( 25 )   PDF (8426KB) ( 19 )  
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    We investigated the solid-liquid suspension characteristics in the tank with a liquid height/tank diameter ratio of 1.5 stirred by a novel long-short blades (LSB) impeller by the Euler granular flow model coupled with the standard k-ε turbulence model. After validation of the local solid holdup by experiments, numerical predictions have been successfully used to explain the influences of impeller rotating speed, particle density, particle size, liquid viscosity and initial solid loading on the solid suspension behavior, i.e. smaller particles with lower density are more likely to be suspended evenly in the liquid with higher liquid viscosity. At a low impeller rotating speed (N), increase in N leads to an obvious improvement in the solid distribution homogeneity. Moreover, the proposed LSB impeller has obvious advantages in the uniform distribution of the solid particles compared with single Rushton turbine (RT), dual RT impellers or CBY hydrofoil impeller under the same power consumption.
    Fabrication of super-elastic graphene aerogels by ambient pressure drying and application to adsorption of oils
    Xinxin Zhao, Wenlong Xu, Shuang Chen, Huie Liu, Xiaofei Yan, Yan Bao, Zexin Liu, Fan Yang, Huan Zhang, Ping Yu
    2022, 47(7):  89-97.  doi:10.1016/j.cjche.2021.09.031
    Abstract ( 50 )   PDF (4415KB) ( 34 )  
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    Three-dimensional graphene-based aerogels have promising applications in oil adsorption and environmental restoration. However, current research of graphene-based aerogels is often hindered by high preparation cost, poor mechanical properties and low recycling efficiency. Here, super-elastic graphene aerogel (SGA) was prepared through one-step freezing and twice hydrothermal reduction followed by drying under ambient pressure. The simple atmospheric drying provides a possibility for large-scale preparation of high performance graphene-based aerogels. The prepared SGA not only has the ability of highly repeatable compression rebound, but also exhibits excellent oil adsorption performance. And the overall performance of SGA is better than most of graphene-based aerogels prepared by freeze drying. After the SGA was cyclically compressed with 70% strain for 300 times, it can return to the original shape and height substantially. SGA retained about 90% of the initial adsorption capacity after 50 cycles of adsorption and compression regeneration for cyclohexane.
    “Relay-mode” promoting permeation of water-based fire extinguishing agent in granular materials porous media stacks
    Kang Wang, Wei Tan, Liyan Liu
    2022, 47(7):  98-112.  doi:10.1016/j.cjche.2021.05.027
    Abstract ( 35 )   PDF (16523KB) ( 19 )  
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    Water-based fire extinguishing agent is the main means to deal with smoldering fires. However, due to the hydrophobic properties of the particle surface, the porous medium channel provide resistance and slow down the extinguishing agent flow during the downward permeation process. To promote the liquid permeation process in such porous media, this work studied liquid imbibition process and analyzed the oscillating and attenuating process of liquid level in capillary channel by theoretical, experimental, and numerical methods. An empirical mathematical equation was proposed to describe the oscillating process, and the effects of the capillary diameter and contact angle parameters on the transportation process were analyzed. Based on this, the "relay-mode" was proposed to promote the liquid transportation forward. Finally, the transient simulation results of liquid permeation in coal stacks showed when the liquid flowed through the channel with changed diameter from large to small ones, the transportation distance was several times longer than that through the unidiameter ones. The trend of liquid "relay-mode" in capillaries can be used to promote the permeation in granular materials porous media stacks. The relevant results also provide new thoughts to develop the water-based fire extinguishing agents and then improve the firefighting efficiency of deep-seated fire in porous media stacks.
    Thermochemical decomposition of phosphogypsum with Fe-P slag via a solid-state reaction
    Lei Sun, Zhongjun Zhao, Xiushan Yang, Yan Sun, Quande Li, Chunhui Luo, Qiang Zhao
    2022, 47(7):  113-119.  doi:10.1016/j.cjche.2021.06.025
    Abstract ( 24 )   PDF (2455KB) ( 22 )  
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    Phosphogypsum is a solid waste sourced from the wet-process phosphoric acid industry, which causes severe environmental damages. Its utilization was limited by its high decomposition temperature and high energy consumption. Herein, an Fe-P slag, which is a solid waste that mainly comprises iron phosphide (FeP) and diiron phosphide (Fe2P), can dramatically decrease the decomposition temperature of phosphogypsum. It was found that the Fe-P slag and CaSO4 can react as shown in the following reaction equation:2Fe1.5P + 3CaSO4 + 6CO2 → Ca3(PO4)2 + Fe3O4 + 3SO2 + 6CO. Its reaction mechanism was further determined using the thermodynamic method. It was found that CaS was the key intermediate for this reaction. The CaSO4 conversion for this method can reach approximately 97% under the optimized roasting conditions:the molar ratio between Fe1.5P and CaSO4 of 2:3, roasting temperature of 900℃, a roasting time of 8 h.
    Superb VOCs capture engineering carbon adsorbent derived from shaddock peel owning uncompromising thermal-stability and adsorption property
    Fu Yang, Wenhao Li, Rui Ou, Yutong Lu, Xuexue Dong, Wenlong Tu, Wenjian Zhu, Xuyu Wang, Lulu Li, Aihua Yuan, Jianming Pan
    2022, 47(7):  120-133.  doi:10.1016/j.cjche.2021.02.013
    Abstract ( 28 )   PDF (11037KB) ( 15 )  
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    High applied thermal-stability and superior structural property for activated carbon adsorbent are extremely promising, which also is the determining short slab in volatile organic compounds (VOCs) adsorption applications. Herein, we develop the outstanding engineering carbon adsorbents from waste shaddock peel which affords greatly-enhanced thermal-stability and super structural property (SLang?=?4962.6?m2·g-1, Vmicro?=?1.67?cm3·g-1). Such character endows the obtained adsorbent with ultrahigh adsorption capture performance of VOCs specific to benzene (16.58?mmol·g-1) and toluene (15.50?mmol·g-1), far beyond traditional zeolite and activated carbon even MOFs materials. The structural expression characters were accurately correlated with excellent adsorption efficiency of VOCs by studying synthetic factor-controlling comparative samples. Ulteriorly, adsorption selectivity prediction at different relative humidity was demonstrated through DIH (difference of the isosteric heats), exceedingly highlighting great superiority (nearly sixfold) in selective adsorption of toluene compared to volatile benzene. Our findings provide the possibility for practical industrial application and fabrication of waste biomass-derived outstanding biochar adsorbent in the environmental treatment of threatening VOCs pollutants.
    Online temperature estimation of Shell coal gasification process based on extended Kalman filter
    Kangcheng Wang, Jie Zhang, Dexian Huang
    2022, 47(7):  134-144.  doi:10.1016/j.cjche.2021.07.030
    Abstract ( 33 )   PDF (921KB) ( 15 )  
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    Obtaining the temperature inside the gasifier of a Shell coal gasification process (SCGP) in real-time is very important for safe process operation. However, this temperature cannot be measured directly due to the harsh operating condition. Estimating this temperature using the extended Kalman filter (EKF) based on a simplified mechanistic model is proposed in this paper. The gasifier is partitioned into three zones. The quench pipe and the transfer duct are seen as two additional zones. A simplified mechanistic model is developed in each zone and formulated as a state-space representation. The temperature in each zone is estimated by the EKF in real-time. The proposed method is applied to an industrial SCGP and the effectiveness of the estimated temperatures is verified by a process variable both qualitatively and quantitatively. The prediction capability of the simplified mechanistic model is validated. The effectiveness of the proposed method is further verified by comparing it to a Kalman filter-based single-zone temperature estimation method.
    Characterization of four diol dehydrogenases for enantioselective synthesis of chiral vicinal diols
    Jiandong Zhang, Rui Dong, Xiaoxiao Yang, Lili Gao, Chaofeng Zhang, Fan Ren, Jing Li, Honghong Chang
    2022, 47(7):  145-154.  doi:10.1016/j.cjche.2021.05.019
    Abstract ( 24 )   PDF (4560KB) ( 13 )  
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    Enantiopure vicinal diols are important building blocks used in the synthesis of fine chemicals and pharmaceutical compounds. Diol dehydrogenase (DDH) mediated stereoselective oxidation of racemic vicinal is an efficient way to prepare enantiopure vicinal diols. In this study, four new bacterial DDHs (AnDDH from Anoxybacillus sp. P3H1B, HcDDH from Hazenella coriacea, GzDDH from Geobacillus zalihae and LwDDH from Leptotrichia wadei) were mined from the GenBank database and expressed in E. coli T7. The four DDHs were purified and biochemically characterized for oxidation activity toward (R)-1-phenyl-1,2-ethanediol, with the optimal reaction condition of pH9.0 (AnDDH), 10.0 (HcDDH) and 11.0 (GzDDH and LwDDH) and the temperatures at 40℃ (AnDDH), 50℃ (HcDDH) and 60℃ (GzDDH and LwDDH), respectively. The four enzymes were stable at the pH from 7.0 to 9.0 and below 40℃. Kinetic parameters of four DDHs showed that the HcDDH from Hazenella coriacea had high activity toward a broad range of vicinal diols. A series of racemic vicinal diols were successfully resolved by recombinant E. coli (HcDDH-NOX) resting cells co-expression of an NADH oxidase (NOX), affording (S)-diols and (1S, 2S)-trans-diols in ≥ 99% ee. The synthetic potential of HcDDH was proved by E. coli (HcDDH-NOX) via kinetic resolution of racemic trans-1,2-indandiol on a 100 ml scale reaction, (S, S)-trans-1,2-indandiol was prepared in 46.7% yield and >99% ee. In addition, asymmetric reduction of four α-hydroxy ketones (10-300 mmol·L-1) by E. coli (HcDDH-GDH) resting cells resulted in >99% ee and 69-98% yields of (R)-vicinal diols. The current research expands the toolbox of DDHs to synthesize chiral vicinal diols and demonstrated that the mined HcDDH is a potential enzyme in the synthesis of a broad range of chiral vicinal diols.
    The selective adsorption of rare earth elements by modified coal fly ash based SBA-15
    Jinglei Cui, Qian Wang, Jianming Gao, Yanxia Guo, Fangqin Cheng
    2022, 47(7):  155-164.  doi:10.1016/j.cjche.2021.07.033
    Abstract ( 33 )   PDF (8020KB) ( 30 )  
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    Rare earth elements (REE) are strategic resources and the recycling of REE in alternative resources is urgent and gets increasingly attention. However, the separation of REE in these alternative resources is still a challenge due to the low concentration of REE and multi coexisted ions in acidic system. In this study, the species distribution of REE within the pH 0-8.0 was calculated. The SBA-15 originated from coal fly ash was modified by two steps with (3-aminopropyl) triethoxysilane (APTES) and diethylenetriaminepentaacetic dianhydride (DTPADA) to obtain DTPADA-SBA-15 adsorbent, which was applied to the selective adsorption of REE. The results showed that DTPADA-SBA-15 possessed excellent adsorption performance on the selective adsorption of REE, including Eu, Gd, Tb, Nd and Sm, in acidic solution (pH 2) with multi competing ions. The FT-IR and Zeta potential characterization verified that the chemical adsorption through the coordination of O in DTPADA-SBA-15 with REE was dominant at lower pH value. The study of adsorption kinetics indicated that the adsorption of rare earth metal ions followed pseudo-second-order kinetic, of which the adsorption process followed the Langmuir isotherm model.
    Modeling of propane dehydrogenation combined with chemical looping combustion of hydrogen in a fixed bed reactor
    Junru Liu, Rui Hu, Xinlei Liu, Qunfeng Zhang, Guanghua Ye, Zhijun Sui, Xinggui Zhou
    2022, 47(7):  165-173.  doi:10.1016/j.cjche.2021.07.032
    Abstract ( 63 )   PDF (5743KB) ( 49 )  
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    A redox process combining propane dehydrogenation (PDH) with selective hydrogen combustion (SHC) is proposed, modeled, simulated, and optimized. In this process, PDH and SHC catalysts are physically mixed in a fixed-bed reactor, so that the two reactions proceed simultaneously. The redox process can be up to 177.0% higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor. The reason is twofold:firstly, SHC reaction consumes hydrogen and then shifts PDH reaction equilibrium towards propylene; secondly, SHC reaction provides much heat to drive the highly endothermic PDH reaction. Considering propylene yield, operating time, and other factors, the preferable operating conditions for the redox process are a feed temperature of 973 K, a feed pressure of 0.1 MPa, and a mole ratio of H2 to C3H8 of 0.15, and the optimal mass fraction of PDH catalyst is 0.5. This work should provide some useful guidance for the development of redox processes for propane dehydrogenation.
    Insights into the confinement effect on isobutane alkylation with C4 olefin catalyzed by zeolite catalyst: A combined theoretical and experimental study
    Shuo Li, Jianlin Cao, Xiang Feng, Yupeng Du, De Chen, Chaohe Yang, Wenhua Wang, Wanzhong Ren
    2022, 47(7):  174-184.  doi:10.1016/j.cjche.2021.08.005
    Abstract ( 35 )   PDF (10988KB) ( 20 )  
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    Elucidating the confinement effect harbours tremendous significance for isobutane alkylation with C4 olefin. Herein, the confinement effect over zeolite catalysts was elucidated by combining DFT calculations, experiments (using the novel Beta zeolite exposing only external surfaces (Beta-E) and conventional Beta-I zeolite with both external and internal surfaces) and multi-techniques (e.g., TGA-DTG, HRTEM, SEM and XRD). It is found that the main active sites for C4 alkylation reaction are located on internal surface rather than external surface. On the external surface, the hydride transfer reaction does not occur because the H-shared intermediate cannot be formed without the confinement effect. Moreover, the external surface has stronger selectivity for C4 olefin adsorption than isobutane, leading to enhanced oligomerization reactions. Therefore, the suitable micropore with confinement effect is essential for zeolite-catalyzed C4 alkylation. The atomic-scale insights of this work are of great referential importance to the design of highly effective zeolite catalyst.
    Hybrid CuO-Co3O4 nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries
    Yingmeng Zhang, Luting Liu, Qingwei Deng, Wanlin Wu, Yongliang Li, Xiangzhong Ren, Peixin Zhang, Lingna Sun
    2022, 47(7):  185-192.  doi:10.1016/j.cjche.2021.06.026
    Abstract ( 25 )   PDF (10676KB) ( 256 )  
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    Hybrid CuO-Co3O4 nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional (3D) hybrid architecture (CuO-Co3O4-RGO), which are successfully applied as enhanced anodes for lithium-ion batteries (LIBs). The CuO-Co3O4-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g-1 after 200 cycles' cycling at 100 mA·g-1 with a capacity retention of 79%. The CuO-Co3O4-RGO compounds show superior electrochemical properties than the comparative CuO-Co3O4, Co3O4 and CuO anodes, which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages; the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co3O4 nanospheres; the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.
    Hydrothermal synthesis of zeolitic material from circulating fluidized bed combustion fly ash for the highly efficient removal of lead from aqueous solution
    Zhibin Ma, Xueli Zhang, Guangjun Lu, Yanxia Guo, Huiping Song, Fangqin Cheng
    2022, 47(7):  193-205.  doi:10.1016/j.cjche.2021.05.043
    Abstract ( 36 )   PDF (7555KB) ( 16 )  
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    The utilization of coal fly ash derived from circulating fluidized bed combustion (CFBFA) still faces great challenges because of its unique characteristics. In this study, a zeolitic material with Na-P1 zeolite as the main phase was successfully synthesized via a hydrothermal method by using CFBFA as the raw material. The effects of hydrothermal temperature, time, and added CTAB amount on the characterizations of synthesized materials were investigated by XRD, SEM, and XPS. The properties of the optimal zeolitic material and its adsorption performance for Pb2+ in aqueous solution were evaluated. The influences of pH, initial concentration, dosage, and temperature on Pb2+ adsorption were also examined. Results revealed the following optimal parameters for the synthesis of zeolitic material:NaOH concentration of 2 mol·L-1, solid-to-liquid ratio of 1:10 g·ml-1, hydrothermal temperature of 110℃, hydrothermal time of 9 h, and CTAB amount of 1 g (per 100 ml solution). The adsorption capacities of the zeolitic material reached 329.67, 424.69, and 542.22 mg·g-1 when the pH values of aqueous solution were 5, 6, and 7, respectively. The Pb2+removal efficiency can reach more than 99% in aqueous solution with the initial concentrations of 100-300 mg·L-1 under pH 6 and suitable adsorbent dosage. The adsorption and kinetics of Pb2+ on the zeolitic material can be described by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The ion exchange between Pb2+ and Na+ and chemisorption are the main adsorption mechanism. All these findings imply that the synthesis of low-cost adsorbent for Pb2+ removal from weak acid and neutral aqueous solution provides a highly effective method to utilize CFBFA.
    Synthesis of carbon-coated cobalt ferrite core–shell structure composite: A method for enhancing electromagnetic wave absorption properties by adjusting impedance matching
    Jing Gao, Zhijun Ma, Fuli Liu, Cunxin Chen
    2022, 47(7):  206-217.  doi:10.1016/j.cjche.2021.07.006
    Abstract ( 25 )   PDF (14893KB) ( 23 )  
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    Cobalt ferrite has problems such as poor impedance matching and high density, which results in unsatisfactory electromagnetic wave (EMW) absorption performance. In this study, the CoFe2O4@C core-shell structure composite was synthesized by a two-step hydrothermal method. X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and vector network analysis et al. were used to test the structure and EMW absorption properties of CoFe2O4@C composite. The results show that the reflection loss (RL) of the CoFe2O4@C composite reaches the maximum value of -25.66 dB at 13.92 GHz, and the effective absorbing band (EAB) is 4.59 GHz (11.20-15.79 GHz) when the carbon mass content is 6.01%. The RL and EAB of CoFe2O4@C composite are increased by 219.55% and 4.59 GHz respectively, and the density is decreased by 20.78% compared with the cobalt ferrite. Such enhanced EMW absorption properties of CoFe2O4@C composite are attributed to the attenuation caused by the strong natural resonance of the cobalt ferrite, moreover, the carbon coating layer adjusts the impedance matching of the composite, and the introduced dipole polarization and interface polarization can cause multiple Debye relaxation processes.
    A numerical study of mixing intensification for highly viscous fluids in multistage rotor–stator mixers
    Liying Chen, Junheng Guo, Wenpeng Li, Shuchun Zhao, Wei Li, Jinli Zhang
    2022, 47(7):  218-230.  doi:10.1016/j.cjche.2021.08.012
    Abstract ( 32 )   PDF (11680KB) ( 17 )  
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    How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research. A typical multistage rotor-stator mixer (MRSM) equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation, considering the influence factors associated with different geometric parameters of both MRSM and the distributor. The mixing index and power consumption are used to evaluate the performance of the mixers. The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate, rotor speed, the number of mixing units. Adopting the optimized mixer with the distributor (X1-T1), the mixing index increases to 0.85 (obviously higher than 0.46 for the mixer T1 without a distributor), meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect. It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption. These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.
    Two-tier control structure design methodology applied to heat exchanger networks
    Siwen Gu, Lei Zhang, Yu Zhuang, Weida Li, Jian Du, Cheng Shao
    2022, 47(7):  231-244.  doi:10.1016/j.cjche.2021.08.022
    Abstract ( 21 )   PDF (4397KB) ( 31 )  
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    Because of its paramount importance in the successful industrial control strategy of a given heat exchanger network (HEN), the control structure designs for providing appropriate manipulated variable (MV) and controlled variable pairings have received considerable attention. However, quite frequently HENs with such control structures face the problem of hard constraints, typically holding the HENs at less controlled operating space. So both the MV pairings and the above control pairings should be considered to design a control structure. This paper investigates the systematic incorporation of the two pairings, and presents a methodology for designing such two-tier control structure. This is developed based on the sequential strategy, coupling an indirect-tier with direct-tier control structure design, wherein the intention is realized in the former stage and the latter is implemented for further optimization. The MV identification and pairing are achieved through variations in heat load of heat exchangers to design the indirect-tier control structure. Then the direct-tier control structure is followed the relative gain array pairing rules. With the proposed methodology, on the one hand, it generates an explicit connection between the MV pairings and the HEN configuration, and the quantitative interaction measure is improved to avoid the multiple solutions to break the relationship among all the control pairings into individuals; on the other hand, a two-tier control structure reveals control potentials and control system design requirements, this may avoid complex and economically unfavourable control and HEN structures. The application of proposed framework is illustrated with two cases involving the dynamic simulation analysis, the quantitative assessment and the random test.
    Foaming biocompatible and biodegradable PBAT/PLGA as fallopian tube stent using supercritical carbon dioxide
    Yue Wang, Luyao Huan, Haiyan Liang, Xuejia Ding, Jianguo Mi
    2022, 47(7):  245-253.  doi:10.1016/j.cjche.2021.04.028
    Abstract ( 40 )   PDF (4304KB) ( 26 )  
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    Tubal pregnancy is a common abnormal pregnancy manifestation, and the ordinary conservative treatment of tubal adhesion usually leads to the rupture of fallopian tube, which increases the risk of a second ectopic pregnancy. To avoid this symptom, it is suitable to implant a stent to separate the adhesion. Here we prepared the PBAT/PLGA foam as the stent material using supercritical CO2 foaming technology. With uniform macroporous structure and thin-wall feature, the foam possessed low compressive modulus in prevention of the possible second injury to the fallopian tube. The introduction of PLGA 50/50 improved the biodegradable capability of the foam, with a mass loss about 20% after a 12-week hydrolysis. After implanted into the ruptured fallopian tube of the rabbit model, the foam displayed excellent biocompatibility, and provided a good support to prevent tubal adhesion. As such, this work provides the foam material as a promising candidate for fallopian tube stent to remedy the tubal adhesion.
    Numerical investigation for the suitable choice of bubble diameter correlation for EMMS/bubbling drag model
    Nouman Ahmad, Jianqiang Deng, Muhammad Adnan
    2022, 47(7):  254-270.  doi:10.1016/j.cjche.2021.10.006
    Abstract ( 29 )   PDF (12296KB) ( 17 )  
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    Mesoscale bubbles exist inherently in bubbling fluidized beds and hence should be considered in the constitutive modeling of the drag force. The energy minimization multiscale bubbling (EMMS/bubbling) drag model takes the effects of mesoscale structures (i.e., bubbles) into the modeling of drag coefficient and thus improves the coarse-grid simulation of bubbling and turbulent fluidized beds. However, its dependence on the bubble diameter correlation has not been thoroughly investigated. The hydrodynamic disparity between homogeneous and heterogeneous fluidization is accounted for by the heterogeneity index,Hd, which can be affected by choice of bubble diameter correlation. How this choice of bubble diameter correlation influences the model prediction calls for further fundamental research. This article incorporated seven different bubble diameter correlations into EMMS/bubbling drag model and studied their effects onHd. The performance of these correlations has been compared with the correlation used previously by EMMS/bubbling drag model. We found that some of the correlations predicted lower Hd by order of a magnitude than the correlation used by the original EMMS/bubbling drag. Based on such analysis, we proposed a modification in the EMMS drag model for bubbling and turbulent fluidized beds. A computational fluid dynamics (CFD) simulation using two-fluid model with the modified EMMS/bubbling drag model was performed for two bubbling and one turbulent fluidized beds. Voidage distribution, time averaged solid concentration and axial solid concentration profiles were studied and compared with the previous version of the EMMS/bubbling drag model and experimental data. We found that the right choice of bubble diameter correlations can significantly improve the results for CFD simulations.
    The study of the effect of gas-phase fluctuation on slag flow and refractory brick corrosion in the slag tapping hole of an entrained-flow gasifier
    Kuo Lin, Zhongjie Shen, Qinfeng Liang, Jianliang Xu, Haifeng Liu
    2022, 47(7):  271-281.  doi:10.1016/j.cjche.2021.07.029
    Abstract ( 33 )   PDF (6208KB) ( 26 )  
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    The service life of refractory brick in the slag tapping hole of the entrained flow gasifier was significantly lower than that in other locations. It was critically important to study the corrosion mechanism of refractory brick in the slag tapping hole for guiding industrial production. Considering the complex flow field in the slag tapping hole, the influence of gas velocity and temperature fluctuation on the service life of refractory brick was investigated in this study. The results showed that the slag flow characteristics periodically changed with the gas temperature and velocity fluctuations. The brick corrosion rate increased with the decrease of fluctuation frequency. Compared with the gas-phase velocity fluctuation, the gas-phase temperature fluctuation had a more significant influence on the brick corrosion rate. When the fluctuation frequency was 0.01 Hz and the gas temperature fluctuation amplitude was 200 K, the corrosion rate of refractory bricks increased by 25%. It could be concluded that the fluctuation of gas-phase temperature was the main cause for the low service life of refractory bricks in the tapping hole.