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Table of Content
28 October 2018, Volume 26 Issue 10
    Fluid Dynamics and Transport Phenomena
    Online measurement of solids motion in fluidized bed reactor with different distributor for Fischer-Tropsch synthesis
    Xiaolai Zhang, Weixin Qian, Haitao Zhang, Qiwen Sun, Weiyong Ying
    2018, 26(10):  2003-2008.  doi:10.1016/j.cjche.2017.12.003
    Abstract ( 511 )   PDF (2760KB) ( 54 )  
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    In this paper, the distributions of particle velocity in a gas-solid fluidized bed with branched pipe distributor or circle distributor were measured by using a laser Doppler velocimetry. Our results show that, within a certain range of superficial gas velocity, when using circle distributor, the particle velocity is large and the distribution of the particle velocity is even more compared with the branched pipe distributor. On the basis of the amplitude of tangential movement statistics, the amplitude of tangential movement statistics (AVATMS) decreases with increasing the axial height under the appropriate superficial gas velocity.
    Compressibility induced bubble size variation in bubble column reactors: Simulations by the CFD-PBE
    Dongyue Li, Zhipeng Li, Zhengming Gao
    2018, 26(10):  2009-2013.  doi:10.1016/j.cjche.2018.04.032
    Abstract ( 652 )   PDF (481KB) ( 41 )  
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    Bubble column reactors can be simulated by the two fluid model (TFM) coupled with the population balance equation (PBE). For the large industrial bubble columns, the compressibility due to the pressure difference may introduce notable bubble size variation. In order to address the compressibility effect, the PBE should be reformulated and coupled with the compressible TFM. In this work, the PBE with a compressibility term was formulated from single bubble dynamics, the mean Sauter diameters predicted by the compressible TFM coupled with the PBE were compared with the analytical solutions obtained by the ideal gas law. It was proven that the mesoscale formulations presented in this work were physically consistent with the macroscale modeling. It can be used to simulate large industrial plants when the compressibility induced bubble size variation is important.
    Meniscus behaviors and capillary pressures in capillary channels having various cross-sectional geometries
    Yicun Tang, Jingchun Min, Xuan Zhang, Guiling Liu
    2018, 26(10):  2014-2022.  doi:10.1016/j.cjche.2018.04.031
    Abstract ( 545 )   PDF (8300KB) ( 13 )  
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    A numerical study has been conducted to simulate the liquid/gas interface (meniscus) behaviors and capillary pressures in various capillary channels using the volume of fluid (VOF) method. Calculations are performed for four channels whose cross-sectional shapes are circle, regular hexagon, square and equilateral triangle and for four solid/liquid contact angles of 30°, 60°, 120° and 150°. No calculation is needed for the contact angle of 90° because the liquid/gas interface in this case can be thought to be a plane surface. In the calculations, the liquid/gas interface in each channel is assumed to have a flat surface at the initial time, it changes towards its due shape thereafter, which is induced by the combined action of the surface tension and contact angle. After experiencing a period of damped oscillation, it stabilizes at a certain geometry. The interface dynamics and capillary pressures are compared among different channels under three categories including the equal inscribed circle radius, equal area, and equal circumscribed circle radius. The capillary pressure in the circular channel obtained from the simulation agrees well with that given by the Young-Laplace equation, supporting the reliability of the numerical model. The channels with equal inscribed circle radius yield the closest capillary pressures, while those with equal circumscribed circle radius give the most scattered capillary pressures, with those with equal area living in between. A correlation is developed to calculate the equivalent radius of a polygonal channel, which can be used to compute the capillary pressure in such a channel by combination with the Young-Laplace equation.
    Separation Science and Engineering
    Comparison of continuous homogenous azeotropic and pressure-swing distillation for a minimum azeotropic system ethyl acetate/n-hexane separation
    Liping Lü, Lin Zhu, Huimin Liu, Hang Li, Shirui Sun
    2018, 26(10):  2023-2033.  doi:10.1016/j.cjche.2018.02.002
    Abstract ( 840 )   PDF (730KB) ( 118 )  
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    Continuous homogenous azeotropic distillation (CHAD) and pressure-swing distillation (PSD) are explored to separate a minimum-boiling azeotropic system of ethyl acetate and n-hexane. The CHAD process with acetone as the entrainer and the PSD process with the pressures of 0.1 MPa and 0.6 MPa in two columns are designed and simulated by Aspen Plus. The operating conditions of the two processes are optimized via a sequential modular approach to obtain the minimum total annual cost (TAC). The computational results show that the partially heat integrated pressure-swing distillation (HIPSD) has reduced in the energy cost and TAC by 40.79% and 35.94%, respectively, than the conventional PSD, and has more greatly reduced the energy cost and TAC by 62.61% and 49.26% respectively compared with the CHAD process. The comparison of CHAD process and partially HIPSD process illustrates that the partially HIPSD has more advantages in averting the product pollution, energy saving, and economy.
    Pressure relief-dipping-microwave assisted polymerization of melamine-L-aspartic acid resin at activated carbon for purification of L-threonine fermented crude product
    Bin Li, Wenshuai Tang, Aiguo Yuan, Guanping Jin
    2018, 26(10):  2034-2039.  doi:10.1016/j.cjche.2017.12.013
    Abstract ( 601 )   PDF (2144KB) ( 35 )  
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    L-threonine (L-Thr) obtained by fermentation often contains vestigial hydrosoluble Pb(Ⅱ), Fe(Ⅱ), L-glutamic acid (L-Glu) etc., which affect the product quality. Poly melamine and L-aspartic acid (L-Asp) resin functional coconut shell activated carbon composite (PMA/AC) was prepared by a pressure relief-dipping-microwave assisted polymerization method for the simultaneous removals. The adsorption capacities of Pb(Ⅱ), Fe(Ⅱ) and L-Glu could reach to 82.34 mg·g-1, 57.82 mg·g-1 and 102.58 mg·g-1 at conditions of pH 5.0, 45℃ and 4 h with an initial concentration of 0.01 mol·L-1, respectively. The present PMA/AC was successfully used to the simultaneous removals of vestigial Pb(Ⅱ), Fe(Ⅱ) and L-Glu from the fermented crude product solution of L-Thr. Moreover, the PMA/AC was carefully characterized by FE-SEM, IR et al. analysis techniques, the results show that abundant PMA particles evenly distributed at the inner and outside surface of AC with a size of (50±20) nm.
    Conceptual design of an extractive distillation process for the separation of azeotropic mixture of n-butanol-isobutanol-water
    Hengjun Gai, Kaiqiang Lin, Yirong Feng, Meng Xiao, Kai Guo, Hongbing Song
    2018, 26(10):  2040-2047.  doi:10.1016/j.cjche.2018.05.003
    Abstract ( 575 )   PDF (588KB) ( 114 )  
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    In many chemical processes, large amounts of wastewater containing butanol and isobutanol are produced. Given that n-butanol-isobutanol-water can form triple azeotrope, high-purity butanol cannot be recovered from the wastewater by ordinary distillation. To economically and effectively recover butanol from this kind of wastewater, 1,4-butanediol is selected as an extractant to break the formation of the azeotropes, and a doubleeffect extractive distillation process is proposed. The conceptual design of the proposed process is accomplished based on process simulation. With the proposed process, the purity of recovered butanol and water is greater than 99.99 wt%. In comparison with the conventional azeotropic distillation process, economic analysis shows that the operating cost of the proposed process is lower:when the capacity of wastewater treatment is 100 t·h-1, the total operating cost decreases by 5.385×106 USD per year, and the total annual cost of the new process decreases by 5.249×106 USD per year. In addition, in the extractive distillation system, variable effects on separation purities and cost are more complex than those in the ordinary distillation system. The method and steps to optimize the key variables of the extractive distillation system are also discussed in this paper and can provide reference for similar studies.
    De-emulsification of 2-ethyl-1-hexanol/water emulsion using oil-wet narrow channel combined with low-speed rotation
    Ling Lü, Kejing Wu, You Tang, Siyang Tang, Bin Liang
    2018, 26(10):  2048-2054.  doi:10.1016/j.cjche.2018.04.027
    Abstract ( 569 )   PDF (2199KB) ( 104 )  
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    Low-speed rotation of disc in an internal circulation of a novel de-emulsification with rotation-dise horizental contactor (RHC-D) realized de-emulsification for O/W emulsions due to repeated coalescence in oil-wet narrow channels at a low rotation speed. For three emulsions included ethanol/water/2-ethyl-1-hexanol, ethanol/water/2-ethyl-1-hexanol/SDS (Sodium Dodecyl Sulfonate) and 2-ethyl-1-hexanol/water/SDS emulsion, deemulsification ratios of oil phase could reach 1, 1 and 0.67 respectively at 170 r·min-1, and de-emulsification ratios increased obviously after agitating 10 min. De-emulsification experiment in the seam indicated that oil droplet sizes in O/W emulsion became larger after de-emulsification. The main de-emulsification mechanism in RHCD was the coalescence of oil droplets in oil-wet narrow channels. With increase of the rotation speed, oil droplets dispersed better in the aqueous phase. However, de-emulsification effect enhanced due to the increase of the coalescence rate at a bit higher rotation speed. In addition, internal circulation made those O/W emulsions to be broken repeatedly, consequently de-emulsification ratio increased. Repeated de-emulsification through internal circulation might make continuous extraction of ethanol come true at a low rotation speed.
    Catalysis, Kinetics and Reaction Engineering
    Cerium phosphate-supported Au catalysts for CO oxidation
    Yulin Wang, Huan Liu, Zhen Ma
    2018, 26(10):  2055-2063.  doi:10.1016/j.cjche.2017.08.008
    Abstract ( 620 )   PDF (3874KB) ( 81 )  
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    LaPO4 and hydroxyapatite (Ca10(PO4)6(OH)2) are typical metal phosphates recently found to be useful for making supported metal or metal oxide catalysts, but CePO4 (also belonging to the metal phosphate family) has been rarely used to make supported catalysts. It would be interesting to develop CePO4-supported catalysts and explore their catalytic applications. Herein, hexagonal CePO4 nanorods (denoted as CePO4-H), hexagonal CePO4 nanowires (CePO4-HNW), monoclinic CePO4 nanoparticles (CePO4-M), and monoclinic CePO4 nanowires (CePO4-MNW) prepared by different methods were used to support gold via deposition-precipitation with urea (DPU). The gold contents of these catalysts were all around 1 wt%. The catalytic activities of these Au/CePO4 catalysts in CO oxidation were found to follow the sequence of Au/CePO4-MNW > Au/CePO4-HNW > Au/CePO4-M > Au/CePO4-H. These catalysts were characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES), N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O2-TPD), and CO2 temperature-programmed desorption (CO2-TPD) to find possible correlations between the physicochemical properties and catalytic activities of these catalysts.
    CH4 oxidation to oxygenates with N2O over iron-containing Y zeolites: Effect of preparation
    Jing Zhu, Lisong Fan, Lina Song, Fengqiu Chen, Dangguo Cheng
    2018, 26(10):  2064-2069.  doi:10.1016/j.cjche.2018.05.021
    Abstract ( 535 )   PDF (1590KB) ( 20 )  
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    Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH4 to oxygenates have remained challenging topics so far. In this paper, we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene, which was conducted under water-free conditions followed by a series of calcination. Moreover, extra-framework dinuclear Fe2+ complexes are identified as so-called active α-iron sites on zeolites. ICP-OES, N2 adsorption-desorption test, X-ray diffraction, solid-state 27Al NMR, N2O titration, TEM, EPR and 57Fe Mössbauer spectra were carried out to characterize properties of sample structure, acid sites, as well as the supported iron species. Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites. Compared with catalysts synthesized by conventional impregnation, the samples prepared by the facile approach possess abundant dinuclear Fe2+ complexes but no Fe2O3 bulks and show weak acidity. These lead to a higher oxygenate selectivity in CH4 oxidation to oxygenates. Remarkably, the oxygenate (HCHO and CH3OH) selectivity of 6.5% at 375℃ can be eventually obtained.
    Optimization of conditions for preparation of ZSM-5@silicalite-1 core-shell catalysts via hydrothermal synthesis
    Chuang Liu, Yihua Long, Zhengbao Wang
    2018, 26(10):  2070-2076.  doi:10.1016/j.cjche.2018.03.030
    Abstract ( 608 )   PDF (1763KB) ( 86 )  
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    Although the preparation of ZSM-5@silicalite-1 (ZS) core-shell catalysts has been reported in the literature, their selectivity to para-xylene (PX) in the toluene alkylation with methanol is difficult to control. Here we present the effects of water and ZSM-5 adding amounts in the synthesis solution, the hydrothermal synthesis time, and the Si/Al ratio of core ZSM-5 on the catalytic performance of ZS core-shell catalysts. The ZS core-shell catalysts were characterized by X-ray diffraction (XRD), N2 adsorption, and NH3 temperature-programmed desorption (NH3-TPD) techniques. The highest PX selectivity of 95.5% was obtained for the ZS (Si/Al=140) catalyst prepared in the synthesis solution with a molar ratio of 0.2TPAOH:1TEOS:250H2O at 175℃ and 10 r·min-1 for only 2 h and the corresponding toluene conversion is as high as 22.8% for the alkylation of toluene with methanol.
    Catalytic reduction of NOx by biomass-derived activated carbon supported metals
    Yun Shu, Fan Zhang, Fan Wang, Hongmei Wang
    2018, 26(10):  2077-2083.  doi:10.1016/j.cjche.2018.04.019
    Abstract ( 511 )   PDF (665KB) ( 67 )  
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    In this study, to prepare a series of activated carbon-supported metals for the catalytic reduction of NOx to N2 in excess O2, activated carbons derived from lignocellulosic and herbaceous biomasses were selected as the reducing agents, and alkali and transition metals were used as the catalytic active phases. The effects of the type of biomass, carbonization temperature and catalyst composition on NOx reduction efficiency were analyzed in a fixed-bed flow reactor. The results showed that two temperature regimes are present for the NOx-carbon reaction:at temperatures below 250℃, the NOx adsorption process on the carbon surface was predominant, whereas true NOx reduction by carbon occurred at temperatures above 250℃, producing N2, CO2 and CO. The influence of the carbonization temperature on carbon reactivity depended on the effect of the carbonization temperature on the carbon surface area and the reduction of the metal species on carbon. All studied metals catalyzed both NOx and O2 reduction by carbon, and potassium could strongly enhance the C-NOx reaction without substantial carbon consumption by O2. Moreover, the potassium supported by sawdust-derived activated carbon exhibited higher selectivity and capacity towards NOx reduction than did its previously reported coal-derived counterparts. These properties were ascribed to the high dispersion of the active potassium species on the carbon surface, as observed through the comparison of X-ray photoelectron spectroscopy and powder X-ray diffraction results for the carbons made from biomass and coal-based precursors.
    Process Systems Engineering and Process Safety
    Multi-objective optimization of methane production system from biomass through anaerobic digestion
    Weijun Li, Jakob Kjøbsted Huusom, Zhimao Zhou, Yi Nie, Yajing Xu, Xiangping Zhang
    2018, 26(10):  2084-2092.  doi:10.1016/j.cjche.2018.01.001
    Abstract ( 495 )   PDF (554KB) ( 34 )  
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    This work addressed the multi-objective optimization of a biogas production system considering both environmental and economic criteria. A mixed integer non-linear programming (MINLP) model was established and solved with non-dominated sorting genetic algorithm Ⅱ, from which the Pareto fronts, the optimal technology combinations and operation conditions were obtained and analyzed. It's found that the system is feasible in both environmental and economic considerations after optimization. The most expensive processing section is decarbonization; the most expensive equipment is anaerobic digester; the most power-consuming processing section is digestion, followed by decarbonization and waste management. The positive green degree value on the process is attributed to processing section of digestion and waste management. 3:1 chicken feces and corn straw, solar energy, pressure swing adsorption and 3:1 chicken feces and rice straw, solar energy, pressure swing adsorption are turned out to be two robust technology combinations under different prices of methane and electricity by sensitivity analysis. The optimization results provide support for optimal design and operation of biogas production system considering environmental and economic objectives.
    Data-driven intelligent monitoring system for key variables in wastewater treatment process
    Honggui Han, Shuguang Zhu, Junfei Qiao, Min Guo
    2018, 26(10):  2093-2101.  doi:10.1016/j.cjche.2018.03.027
    Abstract ( 594 )   PDF (2483KB) ( 230 )  
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    In wastewater treatment process (WWTP), the accurate and real-time monitoring values of key variables are crucial for the operational strategies. However, most of the existing methods have difficulty in obtaining the real-time values of some key variables in the process. In order to handle this issue, a data-driven intelligent monitoring system, using the soft sensor technique and data distribution service, is developed to monitor the concentrations of effluent total phosphorous (TP) and ammonia nitrogen (NH4-N). In this intelligent monitoring system, a fuzzy neural network (FNN) is applied for designing the soft sensor model, and a principal component analysis (PCA) method is used to select the input variables of the soft sensor model. Moreover, data transfer software is exploited to insert the soft sensor technique to the supervisory control and data acquisition (SCADA) system. Finally, this proposed intelligent monitoring system is tested in several real plants to demonstrate the reliability and effectiveness of the monitoring performance.
    Investigation on and industrial application of degrading of methanol feed in methanol to propylene process
    Lixiang Jiang, Chufu Li, Ming Xu, Aihua Xing, Rui Feng, Jianjun Wu
    2018, 26(10):  2102-2111.  doi:10.1016/j.cjche.2018.09.010
    Abstract ( 666 )   PDF (3383KB) ( 74 )  
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    At present, methanol to propylene (MTP) technology developed by Lurgi Company is adopted for commercial plants and refined methanol with the purity ≥ 99.85 wt% is required as the feed of MTP unit in Lurgi's technology. Therefore, high energy cost for refined methanol production is one of the bottlenecks to improve the economy of MTP technology. Reducing the grade of feed refined methanol may be an effective method to save energy and reduce operation costs in MTP process. In this work, experiments and process simulation were carried out to investigate the influence and feasibility of degrading the methanol feed. Experiments were conducted to investigate the influence of crude methanol feed on conversion and selectivity of MTP reaction as well as the performance of ZSM-5 catalyst. The experimental results showed that degrading the methanol feed had no obvious influence on the conversion and selectivity of MTP reactions and the catalyst deactivation was caused by the carbon accumulation and metals deposition on the active sites. The process simulation results showed that the influence on the conversion and selectivity as well as the stream load of MTP process was negligible if 98mol% methanol was used as feed. Finally, industrial experiments were conducted by adjusting the operation parameters to degrade of feed methanol of the commercial 500 kt·a-1 MTP unit of Ningmei Group in China. The results of industrial application illustrated that annually 180 kt fuel coal and 150 kt desalted water as well as1770 MW·h-1 electricity would be saved when the water content increased from 0.01% to 0.4%. This work has identified the feasibility to improve MTP technology by degrading the methanol feed.
    Chemical Engineering Thermodynamics
    Transformation of microstructure and phase of disodium guanosine 5'-monophosphate: Thermodynamic perspectives
    Qiao Chen, Fengxia Zou, Pengpeng Yang, Jingwei Zhou, Jinglan Wu, Wei Zhuang, Hanjie Ying
    2018, 26(10):  2112-2120.  doi:10.1016/j.cjche.2018.06.003
    Abstract ( 639 )   PDF (5547KB) ( 52 )  
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    Microstructure and phase transformation of disodium guanosine 5'-monophosphate (5'-GMPNa2) are extremely important for controlling the process and understanding the mechanism of crystallization. In this work, the thermodynamic properties of polymorphous 5'-GMPNa2 especially the solubility were studied, the solubility results show that 5'-GMPNa2 is more soluble in ethanol-water (E-W) than in isopropanol-water (I-W). The amorphous form of 5'-GMPNa2 is more soluble than the crystalline form at the same mole fraction and temperature. Meanwhile, the crystalline forms and morphologies of the residual solids were characterized by PXRD and SEM. The results indicate that solid forms of 5'-GMPNa2 transformed spontaneously from amorphous to crystalline when the ethanol proportion is ≥ 20%. In addition, increasing the pH facilitates the dissolution of 5'-GMPNa2 and helps to maintain the crystalline form. The associated Gibbs free energy values were calculated to verify the trend of transformation from amorphous to crystalline 5'-GMPNa2. These results should help to guide the industrial crystallization process and to obtain the crystalline form of 5'-GMPNa2.
    Equilibrium morphology of gas-liquid Janus droplets: A numerical analysis of buoyancy effect
    Shaobin Zhang, Helen Yan, Yuhao Geng, Ke Wang, Jianhong Xu
    2018, 26(10):  2121-2126.  doi:10.1016/j.cjche.2018.06.007
    Abstract ( 453 )   PDF (2683KB) ( 46 )  
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    In this article, a theoretical model for predicting the equilibrium morphology of gas-liquid Janus droplets was built. Based on this model, the effects of bubble radius and volume ratio on morphology change was systematically studied. The increase of bubble radius causes the two parts (bubble and oil drop) in Janus droplets tend to merge while the impact of volume ratio is complicated. When volume ratio increases, these two parts firstly tend to merge, then gradually separate. The accuracy of this model was verified by experimental results.
    Commentary on the “Measurement and correlation of solubility of meropenem trihydrate in binary (water + acetone/tetrahydrofuran) solvent mixtures”
    Renjie Xu, Min Zheng, Jiao Chen, Hongkun Zhao
    2018, 26(10):  2127-2129.  doi:10.1016/j.cjche.2018.08.012
    Abstract ( 458 )   PDF (148KB) ( 23 )  
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    Problem was discussed on the reported equation parameters by Zhou and co-workers[Chinese Journal of Chemical Engineering 25 (10) (2017) 1461-1466] for expressing the meropenem trihydrate solubility in binary (water + acetone and water + tetrahydrofuran) mixtures with the modified Apelblat equation. The reported model parameters do not back-calculate correctly the evaluated solubility as shown in their published work. The reported parameters of the modified Apelblat equation tabulated in Tables 3 and 4 by Zhou and coworkers are in mistake.
    Energy, Resources and Environmental Technology
    Poly (ether ether ketone ketone) based imidazolium as anion exchange membranes for alkaline fuel cells
    Tiantian Li, Xuemei Wu, Wanting Chen, Xiaoming Yan, Dongxing Zhen, Xue Gong, Jiafei Liu, Shaofeng Zhang, Gaohong He
    2018, 26(10):  2130-2138.  doi:10.1016/j.cjche.2018.05.015
    Abstract ( 525 )   PDF (4514KB) ( 55 )  
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    An imidazolium functionalized poly (ether ether ketone ketone) (PEEKK-DImOH) anion exchange membrane (AEM) readily soluble in certain low-boiling-point solvents (isopropanol) is prepared. The solubility results are consistent with the results of molecular dynamics simulations. By varying the chloromethylation reaction temperature or concentrated sulfuric acid concentration of PEEKK, the degrees of chloromethylation of PEEKK are changed from 54% to 92%, the corresponding PEEKK-DImOH AEMs with the ion exchange capacities (IECs) of 1.14-1.65 mmol·g-1. The PEEKK-DImOH 92% AEM shows high hydroxide conductivity (31 mS·cm-1), suitable water uptake (94%) and acceptable swelling ratio (39%) at 60℃. In addition, the PEEKK-DImOH AEMs possess good thermal and alkaline stability. The maximum power density (46.16 mW·cm-2) of fuel cell prepared with PEEKK-DImOH 92% AEM as exchange membrane and ionomer is much higher than that with commercial AHA membranes. All the above results indicate that the PEEKK used in this study is a promising AEM matrix material for alkaline fuel cells.
    Feasibility analysis of SO2 absorption using a hydrophilic ceramic membrane contactor
    Xingyin Gao, Minghui Qiu, Kaiyun Fu, Peng Xu, Xiangli Kong, Xianfu Chen, Yiqun Fan
    2018, 26(10):  2139-2147.  doi:10.1016/j.cjche.2018.07.011
    Abstract ( 563 )   PDF (2928KB) ( 58 )  
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    Hydrophilic ceramic membranes would be potential candidates for membrane gas absorption if they could be applied to appropriate separation processes. This study highlights a novel concept for the practical implementation of SO2 absorption in hydrophilic ceramic membrane that exhibits outstanding thermal and mechanical stabilities. With this aim, we investigated experimentally the performance of SO2 absorption into aqueous sodium hydroxide (NaOH) solution in a hydrophilic alumina (Al2O3) membrane contactor in terms of SO2 removal efficiency and SO2 mass transfer flux, and compared the performance with that in a hydrophobic one. A series of experiments were performed at various conditions over a NaOH concentration range of 0-1.0 mol·L-1, a liquid flow rate range of 30-180 ml·min-1, a gas flow rate range of 120-1000 ml·min-1, an inlet SO2 concentration range of 400-2000 μl·L-1, and a temperature range of 10-35℃. It was found that the hydrophilic membrane was more competitive when using a NaOH concentration higher than 0.2 mol·L-1. Furthermore, it can be inferred that the hydrophilic α-Al2O3 membrane exhibited exceptional long-term stability under 480 h continuous operation.
    Comparative analysis of residence and diffusion times in rotating bed used for biogas upgrading
    Liang Zhang, Akiber Chufo Wachemo, Hairong Yuan, Yunzhi Pang, Xiujin Li
    2018, 26(10):  2148-2152.  doi:10.1016/j.cjche.2018.02.016
    Abstract ( 504 )   PDF (2221KB) ( 72 )  
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    Rotating bed can be used in desorption operation of biogas upgrading as a new technology. For enough time to desorb, it is important to study the relationship between the residence time of liquid in rotating bed and the material diffusion time of liquid droplet in desorption process. By theoretical deduction, the exponential relation between residence time and liquid flow rate and rotational speed and kinematic viscosity is obtained. By analyzing the solution of nonlinear partial differential equation, the time law of material diffusion in the droplet is obtained. Moreover, by comparing the residence and diffusion times, the diffusion time can be within or out of residence time range, which has a direct relationship to rotational speed and liquid flow. By experiment, the comparison between residence and diffusion times is more realistic when the rotational speed is higher.
    Characteristics of reactivity and structures of palm kernel shell (PKS) biochar during CO2/H2O mixture gasification
    Guozhang Chang, Ximin Yan, Pengyu Qi, Mei An, Xiude Hu, Qingjie Guo
    2018, 26(10):  2153-2161.  doi:10.1016/j.cjche.2018.03.003
    Abstract ( 574 )   PDF (2124KB) ( 65 )  
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    Palm kernel shell (PKS) biochars with different levels of carbon conversion were initially prepared using a tube furnace, after which the reactivity of each sample was assessed with a thermogravimetric analyzer under a CO2 atmosphere. The pore structure and carbon ordering of each biochar also examined, employing a surface area analyzer and a Raman spectroscopy. Thermogravimetric results showed that the gasification index Rs of the PKS biochar decreased from 0.0305 min-1 at carbon conversion (x)=20% to 0.0278 min-1 at x=40%. The expansion of micropores was the dominant process during the pore structure evolution, ad mesopores with sizes ranging from 6 to 20, 48 to 50 nm were primarily generated during gasification under a CO2/H2O mixture. The proportion of amorphous carbon in the PKS biochar decreased significantly as x increased, suggesting that the proportion of ordered carbon was increased during the CO2/H2O mixed gasification. A significantly reduced total reaction time was observed when employing a CO2/intermittent H2O process along with an 83.46% reduction in the steam feed, compared with the amount required using a CO2/H2O atmosphere.
    Insight into the structural features of organic species in Fushun oil shale via thermal dissolution
    Shengkang Wang, Xianyong Wei, Zhimin Zong
    2018, 26(10):  2162-2168.  doi:10.1016/j.cjche.2018.05.013
    Abstract ( 493 )   PDF (697KB) ( 112 )  
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    Fushun oil shale (FOS) was subjected to thermal dissolution (TD) under different conditions. The results show that the optimal solvent, temperature, time, and ratio of solvent to FOS are ethanol, 300℃, 2 h, and 5 ml·g-1, respectively and the corresponding yield of the soluble portion (SP) is 32.2% (daf), which is much higher than the oil content of FOS (ca. 6%), suggesting that TD in ethanol is an excellent way to extract organics from FOS. According to 3 direct analyses, aliphatic moieties in FOS are the most abundant followed by C-O-containing moieties and each cluster in FOS has 3 conjugated aromatic rings on average with fewer substituents. According to the analysis with a gas chromatograph/mass spectrometer, alkanes are predominant in all the SPs. A number of alkenes were identified in the SPs from the TD, while none of the alkenes were detected in acetone-SP obtained at room temperature, implying that the TD can destroy the π-π and intertwining interactions between alkenes and macromolecular structures in FOS. Moreover, a small amount of alkyl-substituted phenols and alkoxysubstituted phenols were detected in ethanol-SP from the TD, which could be the products from ethanolyzing the macromolecular moiety of FOS.
    Reliable, environmentally friendly method for the recycling of spent Ag/α-Al2O3 catalysts using (NH4)2Ce(NO3)6
    Xulong Dong, Jian Li, Qinggui Xiao, Hui Zhang, Tao Qi
    2018, 26(10):  2169-2175.  doi:10.1016/j.cjche.2018.04.018
    Abstract ( 541 )   PDF (2280KB) ( 45 )  
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    Traditionally, Ag-containing solid wastes are leached by nitric acid in order to recycle the noble metal. However, the huge amounts of emission of toxic nitrogen oxides demand the development of a new method for silver recycling. Recently, considering the Ce(IV) solution could be regenerated with electrolyzation method, our group invented a novel environmentally friendly process by using Ce(IV) as the oxidant to dissolve silver from the spent Ag/α-Al2O3 catalysts without NOx emission. To find out the optimal parameters, in this work, the leaching reaction was thoroughly investigated with respect to the temperature, oxidant and HNO3 concentrations, stirring speed, and time. The optimized leaching reaction gave the leaching silver rate 99.8% in 1 h. The kinetic plots suggested a shrinking core model with the internal diffusion-controlled process and the activation energy of 38.83 kJ·mol-1. The order in which the experimental conditions influence the reaction was determined through orthogonal analysis:temperature > oxidant concentration > HNO3 concentration > stirring speed.
    Co-pyrolysis characteristics of typical components of waste plastics in a falling film pyrolysis reactor
    Zechen Jin, Lijie Yin, Dezhen Chen, Yuanjie Jia, Jun Yuan, Yuyan Hu
    2018, 26(10):  2176-2184.  doi:10.1016/j.cjche.2018.07.005
    Abstract ( 609 )   PDF (1324KB) ( 62 )  
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    Waste plastics mainly come from MSW and usually exist in the form of mixed plastics. During the co-pyrolysis process of mixed plastics, various plastic components have different physicochemical properties and reaction mechanisms. Considering the high viscosity and low thermal conductivity of molten plastics, a falling film pyrolysis reactor was selected to explore the rapid co-pyrolysis process of typical plastic components (PP, PE and PS). The oil and gas yields and the compositions of pyrolysis products of the three components under different ratios at pyrolysis temperatures were analyzed to explore the co-pyrolysis characteristics of PP, PE, and PS. The study is of great significance to the recycling of waste plastics.
    Distribution and degradation kinetics of cyhalodiamide in Chinese rice field environment
    Yiping Liu, Ya Zhang, Shuangqing Liu, Yuntao Lü, Ronghua Lin, Min Li, Xiaolan Liao, Xiaogang Li
    2018, 26(10):  2185-2191.  doi:10.1016/j.cjche.2018.07.003
    Abstract ( 715 )   PDF (691KB) ( 127 )  
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    Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests, including Cnaphalocrocis medinalis, Chilo suppressalis, Pieris rapae, Plutella xylostella, Helicoverpa armigera, etc. In the study, a fast and accurate analytical method was developed to detect cyhalodiamide in Chinese typical rice field environment by a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method with UPLC-MS/MS (ultra-high performance chromatography-tandem mass spectrometry). The mean recoveries of cyhalodiamide varied from 73.5% to 107.5%, with the RSDs from 1.2% to 10.7%. The limits of determination (LODs) were 0.0005 mg·kg-1, and the limits of quantitation (LOQs) were from 0.002 to 0.01 mg·kg-1 in all five matrices. This method was used to determine cyhalodiamide residues for studies of the distribution and degradation kinetics in rice field environment. The field trials results showed that cyhalodiamide was easily degradable and the half-lives were 4.2-13.6 d in rice straw, 8.77 d in paddy soil and 5.37-8.45 d in paddy water, respectively. The final residues of cyhalodiamide in brown rice were below 0.35 mg·kg-1. The used dosage of 33.75 g·hm-2 with pre-harvest interval (PHI) of 21 d and the maximum residue limit (MRL) of cyhalodiamide in rice at 0.1 mg·kg-1 were recommended, which would be safe to human health and environment. The developed analytical method will be useful to monitor cyhalodiamide residues and safety evaluation in rice environment.
    Materials and Product Engineering
    Controllable preparation of ZnO porous flower through a membrane dispersion reactor and their photocatalytic properties
    Feng Zhang, Zhilong Xu, Kun Wang, Rizhi Chen, Zhaoxiang Zhong, Weihong Xing
    2018, 26(10):  2192-2198.  doi:10.1016/j.cjche.2018.06.034
    Abstract ( 537 )   PDF (5213KB) ( 60 )  
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    Three dimensional (3D) flower-like basic zinc carbonate constructed by multilayered nanoplates were rapidly prepared at room temperature through the direct precipitation method coupled with membrane dispersion technology, and porous ZnO with similar structures could be obtained after calcining the precursor. The structural properties of the products before and after the calcining process were characterized by SEM, TEM and XRD. The supersaturation of the reaction system due to the membrane dispersion played an important role in the formation of uniform Zn5(CO3)2(OH)6 precursors. A plausible mechanism was proposed for the formation of the flower-like ZnO assembled by nanoplates composed of nanoparticles. The obtained ZnO microspheres showed excellent photocatalytic properties, which could be attributed to the open structure and remarkable amount of porous nanoplates.
    One-step synthesis of hydrophobic magnesium hydroxide nanoparticles and their application in flame-retardant polypropylene composites
    Hongyan Shen, Youzhi Liu
    2018, 26(10):  2199-2205.  doi:10.1016/j.cjche.2018.08.008
    Abstract ( 538 )   PDF (4851KB) ( 49 )  
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    Hydrophobic magnesium hydroxide (MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream-rotating packed bed (IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween 80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties (e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index (LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.
    Recent progress in the green synthesis of rare-earth doped upconversion nanophosphors for optical bioimaging from cells to animals
    Yuan Pu, Jingning Leng, Dan Wang, Jiexin Wang, Neil R. Foster, Jianfeng Chen
    2018, 26(10):  2206-2218.  doi:10.1016/j.cjche.2018.03.005
    Abstract ( 602 )   PDF (7834KB) ( 14 )  
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    Rare-earth doped upconversion nanophosphors (UCNPs), which convert low energy near-infrared (NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented, with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.