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Table of Content
28 April 2019, Volume 27 Issue 4
    Fluid Dynamics and Transport Phenomena
    Structural parameter optimization for novel internal-loop iron-carbon micro-electrolysis reactors using computational fluid dynamics
    Lei Zhang, Mengyu Wu, Yanhe Han, Meili Liu, Junfeng Niu
    2019, 27(4):  737-744.  doi:10.1016/j.cjche.2018.08.001
    Abstract ( 145 )   PDF (2869KB) ( 15 )  
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    It is generally recognized that internal-loop reactors are well-developed mass and heat-transfer multiphase flow reactors. However, the internal flow field in the internal-loop reactor is influenced by the structure parameter of the reactor, which has a great effect on the reaction efficiency. In this study, the computational fluid dynamics simulation method was used to determine the influence of reactor structure on flow field, and a volume-offluid model was employed to simulate the gas-liquid, two-phase flow of the internal-loop micro-electrolysis reactor. Hydrodynamic factors were optimized when the height-to-diameter ratio was 4:1, diameter ratio was 9:1, draft-tube axial height was 90 mm. Three-dimensional simulations for the water distributor were carried out, and the results suggested that the optimal conditions are as follows:the number of water distribution pipes was four, and an inhomogeneous water distribution was used. According to the results of the simulation, the suitable structure can be used to achieve good fluid mechanical properties, such as the good liquid circulation velocity and gas holdup, which provides a good theoretical foundation for the application of the reactor.
    Analysis of deformation and internal flow patterns for rising single bubbles in different liquids
    Xin Li, Pan Zhang, Jianlong Li, Weiwen Wang, Guanghui Chen
    2019, 27(4):  745-758.  doi:10.1016/j.cjche.2018.08.023
    Abstract ( 151 )   PDF (22533KB) ( 20 )  
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    Gas-liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions, and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters, i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol, 86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.
    Understanding self-accelerated water diffusion within poly-lactic acid via molecular dynamics simulation
    Xiaohui Wang, Jiachen Li, Li Zhang
    2019, 27(4):  759-764.  doi:10.1016/j.cjche.2018.09.009
    Abstract ( 154 )   PDF (473KB) ( 23 )  
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    Poly-lactic acid (PLA) is widely used as a controlled drug release material and the diffusion property of water within the polymer matrix is closely related to the drug release profile. This paper studies the water diffusion in PLA by molecular dynamic simulations. Free volume analysis indicates that water molecules are expected to fill in the free volumes of the polymer matrix forming water clusters at low water content. Along with the increase of the water concentration, the polymer starts to swell and the density of the system starts to drop. Due to the high mobility of water within water cluster, the calculated diffusion coefficient dramatically increases along with the incensement of water content. Thus, we conclude that the diffusion of water is a self-accelerate process, with higher mobility of water in the case where more water exists.
    Experimental study of a heavy fuel oil atomization by pressure-swirl injector in the application of entrained flow gasifier
    Pouria Mikaniki, Seyed Mohammad Ali Najafi, Hojat Ghassemi
    2019, 27(4):  765-771.  doi:10.1016/j.cjche.2018.10.001
    Abstract ( 127 )   PDF (4568KB) ( 25 )  
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    The available SMD (Sauter mean diameter) correlations on pressure-swirl injectors predict droplet sizing very different from each other, especially for heavy fuels. Also there was a lack in the literature for comparing available correlations. So an experimental study was conducted on a heavy fuel oil (HFO) spray, Mazut 380. A pressure swirl injector was designed and fabricated. The experiments for Mazut at 40℃ and 80℃ were compared with the results for water, including spray half cone angle, breakup length and mean droplet diameter, at different injection pressures. Lower spray angle, higher breakup length and larger droplets were observed for lower injection pressures and higher liquid viscosity. SMD was about 75 μm for water and about 87 μm for Mazut at 80℃. The results for droplet mean diameter were also compared with correlations from previous studies on pressure swirl atomizers. The SMD results show that for water spray, LISA method was in good agreement, also Babu and Ballester correlations were successful when high viscosity fluid was injected.
    Mass transfer area in a multi-stage high-speed disperser with split packing
    Tao Ai, Aslam M. Mudassar, Ziqi Cai, Zhengming Gao
    2019, 27(4):  772-780.  doi:10.1016/j.cjche.2018.10.012
    Abstract ( 143 )   PDF (4058KB) ( 41 )  
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    In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser (HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%-82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.
    Torque and bending moment acting on a flexible shaft agitated by disk turbines in a gas-liquid stirred vessel
    Yangyang Liang, Zhengming Gao, Dai'en Shi, Haotian Li, Yuyun Bao, Ziqi Cai
    2019, 27(4):  781-793.  doi:10.1016/j.cjche.2018.10.020
    Abstract ( 124 )   PDF (6387KB) ( 21 )  
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    The torque and bending moment acting on a flexible overhung shaft in a gas-liquid stirred vessel agitated by a Rushton turbine and three different curved-blade disk turbines (half circular blades disk turbine, half elliptical blades disk turbine, and parabolic blades disk turbine) were experimentally measured by a customized moment sensor. The results show that the amplitude distribution of torque can be fitted by a symmetric bimodal distribution for disk turbines, and generally the distribution is more dispersive as the blade curvature or the gas flow rate increases. The amplitude distribution of shaft bending moment can be fitted by an asymmetric Weibull distribution for disk turbines. The relative shaft bending moment manifests a "rising-falling-rising" trend over the gas flow number, which is a corporate contribution of the unstable gas-liquid flow around the impeller, the gas cavities behind the blades, and the direct impact of gas on the impeller. And the "falling" stage is greater and lasts wider over the gas flow number for Rushton turbine than for the curved-blade disk turbines.
    CFD analysis of performance improvement of the Savonius water turbine by using an impinging jet duct design
    Narendra Thakur, Agnimitra Biswas, Yogesh Kumar, Mithinga Basumatary
    2019, 27(4):  794-801.  doi:10.1016/j.cjche.2018.11.014
    Abstract ( 216 )   PDF (4263KB) ( 62 )  
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    The majority of research on water turbines focuses on design improvement of large-scale hydrokinetic turbines for power generation, which may have delayed the utilization of kinetic energy contained in rivers and canals. The aim of this paper is to improve the efficiency of a two bladed Savonius type cross-flow hydrokinetic turbine, which can be used as an energy converter to harness free-stream kinetic energy of water. An impinging jet duct design is presented for improving performance of the Savonius turbine in wind application as seen from literature. The performance of the modified turbine is evaluated using CFD software Fluent, and is compared with that of a simple two bladed Savonius water turbine and some of the prominent literature designs of the Savonius turbine. It is shown that the present design exhibits improved performance compared to the selected designs of the Savonius turbine. Further an insight of the improved performance of the modified turbine is also obtained from flow physics study.
    Separation Science and Engineering
    Electrochemical behaviors of anode materials and their performance for bauxite desulfurization
    Yingnan Hu, Aijing Lü, Mingyong Wang, Dong Wang, Junhao Liu, Zhi Wang, Xuzhong Gong
    2019, 27(4):  802-810.  doi:10.1016/j.cjche.2018.04.028
    Abstract ( 135 )   PDF (2970KB) ( 28 )  
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    Pyrite inside bauxite could be oxidized into soluble S-containing ions by electrolysis, and thus achieving bauxite desulfurization by using filtration. However, S-containing ions in electrolyte had some corrosion effects on electrode, especially for anode. In this work, six kinds of traditional materials were selected as anode, and their corrosion behaviors were examined by using electrochemistry characterization. Tafel and CV curves from simulating electrolyte suggested that their corrosion potentials were in the following order:Ni > C > SS > Fe > Cu > Pb-Ag. As expected, the desulfurization ratio and cell voltage from bauxite electrolysis were in the following order respectively:Cu > Ni > Fe > SS > C > Pb-Ag and Ni > Fe > SS > Cu > C > Pb-Ag. Finally, Ni was proposed a kind of excellent electrode material for bauxite desulfurization from electrolysis.
    Separation of methyl linolenate and its analogues by functional mixture of imidazolium based ionic liquid-organic solvent-cuprous salt
    Xianghong Lu, Jiajian Zhu, Xing Qian, Jianbing Ji
    2019, 27(4):  811-817.  doi:10.1016/j.cjche.2018.05.009
    Abstract ( 121 )   PDF (1683KB) ( 24 )  
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    Methyl linolenate was separated from its analogues by a new extraction system constructed by solvent, imidazolium based ionic liquids and cuprous salt. Firstly, the effect of ionic liquid on the dissolution of CuCl in acetonitrile, N,N-dimethylformamide (DMF), methanol and water was evaluated by visual observation.[C4Mim] [Cl] can improve the dissolution of CuCl in acetonitrile. Then, for the new system as acetonitrile-ILs-CuCl, extraction equilibrium, distribution ratio and selectivity of methyl linolenate and its analogues were determined by gas chromatography analysis and the mass balance. The extraction time, IL structures and CuCl concentrations were investigated. Distribution ratio decreased slightly, but selectivity increased significantly with the addition of CuCl,[C4Mim] [Cl] or[C4Vim] [NTF2] into acetonitrile.[C4Vim] [NTF2] had higher selectivity than[C4Mim] [Cl]. But the selectivity of the system combining CuCl with[C4Vim] [NTF2] was much lower than with[C4Mim] [Cl]. For the CuCl-[C4Mim] [Cl]-acetonitrile, the extraction efficiency was better than CuCl-acetonitrile, increasing Cu+ concentration effectively improved the separation selectivity when ratio of CuCl/[C4Mim] [Cl] was less than 1. Compared with previous aqueous AgNO3 extractions, the method of using CuCl is a much cheaper and practical way to enrich unsaturated fatty acid.
    Hybridization of metal-organic framework and monodisperse spherical silica for chromatographic separation of xylene isomers
    Bixuan Gao, Minhui Huang, Zhiguo Zhang, Qiwei Yang, Baogen Su, Yiwen Yang, Qilong Ren, Zongbi Bao
    2019, 27(4):  818-826.  doi:10.1016/j.cjche.2018.06.016
    Abstract ( 161 )   PDF (1852KB) ( 23 )  
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    Metal-organic frameworks (MOFs) packed in the column have been a promising candidate as the stationary phase for high performance liquid chromatography (HPLC). However, the direct packing of irregular MOF powder could raise some problems like high back pressure and low column efficiency in the HPLC separation. In this work, UiO-66 capable of separating xylenes was supported effectively on the surface of the monodisperse spherical silica microspheres by one-pot method. The hybridization of UiO-66 and silica microspheres (termed UiO-66@SiO2 shell-core composite) was prepared by stirring the suspension of the precursors of UiO-66 and—COOH terminated silica in the N,N-dimethylformamide with heating. The shell-core composite material UiO66@SiO2 was characterized by SEM, TEM, PXRD and FTIR. Then, it was used as a packing material for the chromatographic separation of xylene isomers. Xylene isomers including o-xylene, m-xylene and p-xylene were efficiently separated on the column with high resolution and good reproducibility. Moreover, the UiO-66@SiO2 shell-core composites packed column still remained reverse shape selectivity as UiO-66 possessed, and the retention of xylenes was probably ascribed to the hydrophobic effect between analytes and the aromatic rings of the UiO-66 shell. The UiO-66@SiO2 shell-core composites obtained in this study have some potential for the separation of structural isomers in HPLC.
    Adsorption equilibria of paeoniflorin and albiflorin on cyano-silica column from supercritical carbon dioxide/ethanol
    Huisheng Lü, Zhi Wang, Zhongfeng Geng, Yonghui Li, Shuangyan Liu, Jiatao Liu
    2019, 27(4):  827-834.  doi:10.1016/j.cjche.2018.05.026
    Abstract ( 133 )   PDF (689KB) ( 12 )  
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    Adsorption equilibria of paeoniflorin and albiflorin on a cyano-silica column (CN column) from the solution of supercritical carbon dioxide (scCO2) modified with ethanol were studied. The adsorption capacity at 308.15 K, 313.15 K, 318.15 K and 323.15 K under pressures corresponding to carbon dioxide/ethanol densities from 0.347 g·cm-3 to 0.662 g·cm-3 were determined using the elution by characteristic point method (ECP). The effects of temperature and pressure on the solute loading were investigated. The results showed that the lower the temperature, the higher the adsorption capacity. With the decrease of density of scCO2, the adsorption capacity strengthens. The maximum adsorption capacity of paeoniflorin (albiflorin) on the CN column was 15.24 mg·ml-1 (31.14 mg·ml-1) in the range of 0-1.84 mg·ml-1 (0-1.67 mg·ml-1) of paeoniflorin (albiflorin) standard solution. The adsorption capacity of albiflorin was twice as much as that of paeoniflorin under the same conditions. Adsorption data of paeoniflorin and albiflorin could be well described by the Langmuir model and Freundlich model. Compared with the two model fitting results, the adsorption of paeoniflorin and albiflorin belonged to the monolayer adsorption under conditions of 308.15-323.15 K and 10-17 MPa.
    QSPR modeling of azeotropic temperatures and compositions for binary azeotropes containing lower alcohols using a genetic function approximation
    Yixin Ma, Kang Ma, Huixin Wang, Xueli Geng, Jun Gao, Zhaoyou Zhu, Yinglong Wang
    2019, 27(4):  835-844.  doi:10.1016/j.cjche.2018.06.031
    Abstract ( 132 )   PDF (3365KB) ( 17 )  
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    Binary azeotropes, which contain two chemicals with a relative volatility of 1, are very common in the chemical industry. Understanding azeotropes is essential for effectively separating binary azeotropes containing lower alcohols. Experimental techniques and ab initio approaches can produce accurate results; however, these two processes are time consuming and labor intensive. Although thermodynamic equations such as UNIFAC are widely used, experimental values are required, and it is difficult to choose the best groups to represent a complex system. Because of their high efficiency and fast calculation speed, quantitative structure-property relationship (QSPR) tools were used in this work to predict the azeotropic temperatures and compositions of binary azeotropes containing lower alcohols. The QSPR models for 64 binary azeotropes based on centroid approximation and weighted-contribution-factor approximation were established using the genetic function approximation (GFA) procedure in Materials Studio software, and a leave-one-out cross-validation procedure was conducted. External tests of an additional 16 azeotropes were also investigated, and high determination coefficient values were obtained. The best QSPR models were explained in terms of the molecular structure of the azeotropes, and good predictive ability was obtained within acceptable prediction error levels.
    Concentration of linoleic acid from cottonseed oil by starch complexation
    Dan Liang, Yufeng Hu, Weiting Ma, Zhengtang Zhao, Siqi Jiang, Yichuan Wang, Xianming Zhang
    2019, 27(4):  845-849.  doi:10.1016/j.cjche.2018.07.001
    Abstract ( 119 )   PDF (398KB) ( 21 )  
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    The extraction of linoleic acid from fatty acids (FA) of the cottonseed oil using starch-FA complexes was developed for the first time. We showed that starch can form inclusion complexes of different strengths with FA and that the different strengths stem from the differences in chain length, degree of unsaturation, and position of double bonds of FA. The optimal separation conditions were determined as follows:The inclusion temperature is 69℃, the inclusion time is 30 min, the starch/FA mass ratio is 10:1, and the ratio of the volume of methanol-water solution and the mass of FA is 18:1. Compared to urea inclusion complexation, starch complexation has milder reaction temperature and shorter reaction time. Under these conditions, linoleic acid can be concentrated from 38.9% to 70.04% by one-off extraction. Moreover, the experimental results demonstrate the almost perfect reusability of starch. These results show that starch complexation is a promising method that can be used to obtain highly concentrated linoleic acid from cottonseed oil.
    Degradation of simulated organic wastewater by advanced oxidation with oxidants generated from oxygen reduction
    Yi Ouyang, Qing Xu, Yang Xiang, Wei Liu, Junqi Du
    2019, 27(4):  850-856.  doi:10.1016/j.cjche.2018.07.004
    Abstract ( 124 )   PDF (900KB) ( 12 )  
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    The degradation capacity of advanced oxidants generated from oxygen reduction was investigated in model effluent containing chlorobenzene, aniline and benzene through the advanced oxidation processes (AOPs). Intermediate products of the degradation process were determined by GC-MS, and they contributed to specify the degradation pathways of monoaromatic compounds. The study particularly focused on the influence of the dosage of the oxidant, pH and the initial concentration of organic compounds on the degradation effectiveness. When the dosage of oxidant was 4 wt% and the pH was 7, the maximum degradation rates of 74.83% chlorobenzene, 70.32% aniline and 37.69% benzene were achieved. Furthermore, microwave was applied to intensify the oxidation process under optimal operation conditions, and the degradation rates were increased to 87.85% chlorobenzene, 89.11% aniline and 39.03% benzene, respectively.
    Separation of mixed salts (Cl-/SO42-) by ED based on monovalent anion selective membranes
    Jiefeng Pan, Wei Zhang, Huimin Ruan, Jiangnan Shen, Congjie Gao
    2019, 27(4):  857-862.  doi:10.1016/j.cjche.2018.08.007
    Abstract ( 168 )   PDF (2583KB) ( 29 )  
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    The industrial products or wastewater rich in the mixed salts (Cl-/SO42-) not only causes the environmental damage, but also induces waste of resource. In this study, an ED stack with monovalent selective AEMs and conventional CEMs was employed to separate the Cl-and SO42- from simulated wastewater. The effect of current density and mass fraction percentage was investigated in order to optimize the experimental conditions during ED process. It was found that at a concentration ratio between NaCl and Na2SO4 of 95/5 (wt%/wt%) and a current density of 40 mA·cm-2, a current efficiency of 72%, an energy consumption of 1.6 kW·h·kg-1 NaCl and a Cl-/SO42- concentration (67.5/3.5 g·L-1) were obtained. Hence, it is appropriate and effective to separate Cl-and SO42- by ED using the monovalent selective AEMs.
    Adsorption/desorption of toluene on a hypercrosslinked polymeric resin in a highly humid gas stream
    Bing Zhou, Bin Sun, Wenjuan Qiu, Ying Zhou, Junqian He, Xiao'ai Lu, Hanfeng Lu
    2019, 27(4):  863-868.  doi:10.1016/j.cjche.2018.09.027
    Abstract ( 167 )   PDF (943KB) ( 30 )  
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    In many sources of volatile organic compounds (VOCs), large amounts of water vapor come from the air and the reactors. The relative humidity (RH) of exhaust gas is normally>60% and is supersaturated. Maintaining the property of adsorbent on VOCs in a highly humid gas stream is a serious industrial problem. In this study, the adsorption/desorption behavior of toluene in a micro-mesoporous polymeric resin was investigated in a highly humid environment to explore the influence of abound water vapor on resin adsorption and regeneration. This resin could selectively adsorb toluene at an RH of 80%, and its adsorption property was unaffected by the presence of water vapor. In the case of humidity saturation, the resin displayed a high adsorption capacity at a moisture content of<30%. Therefore, the polymer resin is an excellent water-resistant adsorbent of VOCs. In the regenerative experiment, the resin maintained its original adsorption capability after four adsorption/desorption cycles of toluene purging with nitrogen gas at 120℃. The resin exhibited excellent regeneration performance at high humidity.
    A novel kind of multiple steady states characteristics in the dividing wall column
    Erwei Song, Zengxi Li, Erqiang Wang
    2019, 27(4):  869-876.  doi:10.1016/j.cjche.2018.10.003
    Abstract ( 140 )   PDF (822KB) ( 25 )  
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    In this article, one kind of multiple steady states (MSS) phenomenon was investigated for a dividing wall column (DWC). The four-section model constructed in Aspen Plus was employed to simulate two DWC cases:mixture of n-hexane, n-heptane and n-octane; system of methanol, ethanol and n-propanol. It can be seen that there is a range of vapor split ratio in which multiple solutions of reflux ratio exist for fixed DWC configuration with the same feed and product streams. The width and the curve shapes of the MSS region, and the number of solutions change with the liquid split ratio. This MSS phenomenon was further explained using the component recovery around the prefractionator and the component recycling flow inside the DWC. This MSS phenomenon is helpful for DWC design by knowing the probable existence of multiple solutions in advance.
    Crosslinked P84 copolyimide/MXene mixed matrix membrane with excellent solvent resistance and permselectivity
    Runlin Han, Yongli Xie, Xufeng Ma
    2019, 27(4):  877-883.  doi:10.1016/j.cjche.2018.10.005
    Abstract ( 139 )   PDF (4304KB) ( 34 )  
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    MXene is a novel 2D lamellar material with excellent hydrophilicity and permselectivity. MXene was introduced in the P84 polymer matrix and the matrix was crosslinked with triethylenetetramine (TETA) to improve the permselectivity and solvent resistance of the polyimide membrane. The membrane was characterized with SEM, AFM and ATR-FTIR, and effects of MXene content on the membrane morphology and separation performance are investigated. The membrane prepared with 18% P84 and 1% MXene shows high rejection (100%) to gentian violet (408) and high flux (268 L·m-2·h-1) at 0.1 MPa and ambient temperature. MXene endows the membrane with much water channel and denser functional layer which improves the membrane performance obviously. The membrane shows excellent solvent resistance to dimethylformamide (DMF), acetone and methanol after crosslinking with TETA during the 18 days of immersion.
    Catalysis, Kinetics and Reaction Engineering
    Gas-phase oxidation of NO at high pressure relevant to sour gas compression purification process for oxy-fuel combustion flue gas
    Qian Cheng, Dunyu Liu, Jun Chen, Jing Jin, Wei Li, Shuaishuai Yu
    2019, 27(4):  884-895.  doi:10.1016/j.cjche.2018.06.017
    Abstract ( 160 )   PDF (1180KB) ( 18 )  
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    The removal of NO from oxy-fuel combustion is typically incorporated in sour gas compression purification process. This process involves the oxidation of NO to NO2 at a high pressure of 1-3 MPa, followed by absorption of NO2 by water. In this pressure range, the NO conversion rates calculated using the existing kinetic constants are often higher than those obtained experimentally. This study aimed to achieve the regression of kinetic parameters of NO oxidation based on the existing experimental results and theoretical models.
    Based on three existing NO oxidation mechanisms, first, the expressions for NO conversion against residence time were derived. By minimizing the mean-square errors of NO conversion ratio, the optimum kinetic rate constants were obtained. Without considering the reverse reaction for NO oxidation, similar mean-square errors for NO conversion ratio were calculated. Considering the reverse reaction for NO oxidation based on the termolecular reaction mechanism, the minimum mean-square error for NO conversion ratio was obtained. Thus, the optimum NO oxidation rate in the pressure range 0.1-3 MPa can be expressed as follows:
    Detailed elementary reactions for N2/NO/NO2/O2 system were established to simulate the NO oxidation rate. A sensitivity analysis showed that the critical elementary reaction is 2NO + O2 ⇌ 2NO2. However, the simulated NO conversions at a high pressure of 10-30 bar are still higher than the experimental values and similar to those obtained from the models without considering the reverse reaction for NO oxidation.
    Process Systems Engineering and Process Safety
    Temperature inferential control of a reactive distillation column with double reactive sections
    Lijing Zang, Kejin Huang, Ting Guo, Yang Yuan, Haisheng Chen, Liang Zhang, Xing Qian, Shaofeng Wang
    2019, 27(4):  896-904.  doi:10.1016/j.cjche.2018.11.023
    Abstract ( 122 )   PDF (1021KB) ( 14 )  
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    Temperature inferential control (TIC) is studied for a reactive distillation column with double reactive sections (RDC-DRSs) processing a hypothetical two-stage consecutive reversible reaction (A + B ⇌ C + D, C + B ⇌ E + D with αD > αB > αC > αA > αE). Because of the complicated dynamic behaviors, the controlled stages by sensitivity analysis lead to great steady-state deviations (SSDs) in top and bottom product purities. Since TIC involves considerably reduced settling times in comparison with direct composition control, small SSDs in product qualities correspond generally to small transient deviations (TDs) in product qualities. An objective function that measures SSDs in product qualities is formulated to represent the performance of a TIC system and an iterative procedure is devised to search for the best control configuration. The application of the procedure to the RDC-DRS gives considerably suppressed TDs and SSDs in top and bottom product qualities as compared with the one by sensitivity analysis. The method is simpler in principle and less computationally intensive than the current practice. These striking outcomes show the effectiveness of the proposed principle for the development of TIC systems for complicated reactive distillation columns.
    Chemical Engineering Thermodynamics
    Measurements and correlation of liquid-liquid equilibrium data for the ternary (methyl tert-butyl ketone + o, m, p-benzenediol + water) system at (333.2, 343.2 and 353.2) K
    Kangning Xiong, Shuai Shen, Youchang Wang, Yun Chen
    2019, 27(4):  905-911.  doi:10.1016/j.cjche.2018.09.011
    Abstract ( 160 )   PDF (396KB) ( 16 )  
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    In this work, liquid-liquid equilibria (LLE) data for the ternary system methyl tert-butyl ketone (MTBK) + o, m, p-benzenediol + water were investigated at 333.2 K, 343.2 K and 353.2 K under 101.3 kPa. The performance of MTBK to extract o, m, p-benzenediol from wastewaters was estimated by partition coefficients and separation factors. The Hand and Bachman equations were both applied to check the reliability of the experimental LLE data. Furthermore, the Non-Random Two-Liquid (NRTL) and Universal Quasi Chemical (UNIQUAC) models were applied to correlate the measured LLE data. The results showed a good agreement with the determined ternary LLE data with the root-mean-square error (RMSE) values below 0.71%. MTBK was proved to be a promising extracting agent in extracting benzenediols from effluents.
    Energy, Resources and Environmental Technology
    Non-linear modeling of kinetic and equilibrium data for the adsorption of hexavalent chromium by carbon nanomaterials: Dimension and functionalization
    Miguel de la Luz-Asunción, Eduardo E. Pérez-Ramírez, Ana L. Martínez-Hernández, Victor M. Castano, Víctor Sánchez-Mendieta, Carlos Velasco-Santos
    2019, 27(4):  912-919.  doi:10.1016/j.cjche.2018.08.024
    Abstract ( 140 )   PDF (1441KB) ( 31 )  
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    The adsorption capacities for the removal of hexavalent chromium from aqueous solutions by six carbon nanomaterials have been evaluated. Single-walled and multi-walled carbon nanotubes as received and after oxidation treatment, graphene oxide and reduced graphene oxide are the materials with different dimension and functionalization compared in this research. Carbon nanotubes have been modified using hydrogen peroxide as oxidizing agent under microwave radiation. The oxidation treatment on carbon nanotubes has a positive effect increasing the adsorbent-adsorbate interaction. Rate-controlling mechanisms and equilibrium data are analyzed using non-linear models. Non-linear method is proposed as the most suitable method for determining the kinetic and equilibrium parameters. The values of adsorption energy (E) obtained from the Dubinin-Radushkevich isotherm, have been found around 0.371 and 0.870 kJ·mol-1, indicating physical adsorption. Therefore, the pseudo-second order model represents better the kinetic experimental data. The results show that the Langmuir isotherm provides a slightly better fit to the experimental data compared with the Freundlich isotherm, indicating homogeneous distribution of active sites on carbon nanomaterials and monolayer adsorption. The separation factors RL are found in the range of 0-1, suggesting that the adsorption process is suitable for all adsorbents. The mechanisms for hexavalent chromium removal have been proposed as electrostatic interactions and hydrogen bonding.
    Optimization of hydrothermal pretreatment for co-utilization of xylose and glucose of cassava anaerobic residue for producing ethanol
    Huisheng Lü, Jinyi Zhou, Jiatao Liu, Chunliu Lü, Feng Lian, Yonghui Li
    2019, 27(4):  920-927.  doi:10.1016/j.cjche.2018.08.025
    Abstract ( 115 )   PDF (3622KB) ( 27 )  
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    The development of a process that could recover biofuel from industrial cellulose waste can not only reduce the negative environmental impacts by using fossil fuels, but also bring a green idea for the waste's disposing. In this study, hydrothermal pretreatment was optimized for cassava anaerobic residue, a cellulosic waste from cassava ethanol industry, to co-utilize xylose and glucose for producing bioethanol. The effect of the main pretreatment conditions, namely, temperature, solid content and time, was explored for the highest recovery of xylose in prehydrolysate and glucose in enzymatic hydrolysate. The single factor experiment results showed that the conditions for maximum xylose recovery in prehydrolysate and glucose recovery in enzymatic hydrolysate were 60℃, 75 min, 10% solids and 160℃, 75 min, 10% solids, respectively. Whereafter, response surface methodology (RSM) was applied to further optimize the pretreatment conditions for the maximum theoretical ethanol production through utilizing both xylose and glucose. A treatment at 163℃, for 59 min and with 9.5% solids was found optimal, with the highest ethanol production of 20.2 mg·g-1 raw material. Furthermore, in order to assess the impacts of the pretreatment on cassava anaerobic residue, the changes in crystallinity and morphology for untreated and pretreated solids were investigated.
    Thermal conductivity of natural rubber nanocomposites with hybrid fillers
    Junping Song, Xiteng Li, Kaiyan Tian, Lianxiang Ma, Wei Li, Shichune Yao
    2019, 27(4):  928-934.  doi:10.1016/j.cjche.2018.09.019
    Abstract ( 149 )   PDF (4239KB) ( 35 )  
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    Natural rubber nanocomposites filled with hybrid fillers of multi-walled carbon nanotubes (CNTs) and carbon black (CB) were prepared. CNTs were ultrasonically modified in mixture of hydrogen peroxide (H2O2) and distilled water (H2O). The functional groups on the surface of CNTs, changes in nanotube structure and morphology were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman Spectroscopy, and transmission electron microscopy (TEM). It shows that hydroxyl (OH·) is successfully introduced. The surface defects of modified CNTs were obviously higher than those of original CNTs, and the degree of agglomeration was greatly reduced. Thermal conductivity of the composites was tested by protection heat flow meter method. Compared with unmodified CNTs/CB filling system, the thermal conductivity of hybrid composites is improved by an average of 5.8% with 1.5 phr (phr is parts per hundred rubber) of hydroxyl CNTs and 40 phr of CB filled. A three-dimensional heat conduction network composed of hydroxyl CNTs and CB, as observed by TEM, contributes to the good properties. Thermal conductivity of the hybrid composites increases as temperature rises. The mechanical properties of hybrid composites are also good with hydroxyl CNTs filled nanocomposites; the tensile strength, 100% and 300% tensile stress are improved by 10.1%, 22.4% and 26.2% respectively.
    Materials and Product Engineering
    Fabrication and characterization of novel foaming polyurethane hollow fiber membrane
    Yanjie Wu, Changfa Xiao, Hailiang Liu, Qinglin Huang
    2019, 27(4):  935-943.  doi:10.1016/j.cjche.2018.09.016
    Abstract ( 149 )   PDF (3188KB) ( 24 )  
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    Foam-like materials had attracted great interest as promising absorbent. In this study, thermoplastic polyurethane (TPU) block sponge was synthesized. Polyester (PET) braid tubular reinforced polyurethane (PU) spongy hollow fiber membrane was prepared by a concentric circular spinning method. The method was woven from an outer coated water-blown PU separation layer and inner PET braid tubular. We have developed a simple and useful preparation technique for the PU spongy hollow fiber membrane. For the first time, the PU spongy hollow fiber membrane was prepared using a coating and controlled foaming technique. The influence of toluene isocyanate index on the physical properties, morphology, and structure of flexible PU sponge was discussed in terms of water contact angle (CA), pure water flux (PWF), Fourier Transform Infrared Analysis (FTIR), pressure-responsive property, and pull-out strength. The morphologies of the membranes were investigated by scanning electron microscopy. We have characterized the foams from an intuitive point of view and demonstrated that the dimensional morphology of the membrane was closely related to isocyanate index. The result showed that the surface cell size of the PU sponge hollow fiber membrane gradually decreased with an increase of the isocyanate index. Due to the elasticity of PU at room temperature, the pressure responsive characteristic of the membrane was prepared. When isocyanate index was 1.05, the interface bonding strength of PU spongy hollow fiber membranes reached as high as 0.37 MPa, porosity and PWF were 71.5% and 415.5 L·m-2·h-1, respectively.
    Impact of polydimethylsiloxanes on physicochemical and tribological properties of naphthenic mineral oil (KN 4010)-based titanium complex grease
    Jitai Li, Chu Zhai, Hengbo Yin, Aili Wang, Lingqin Shen
    2019, 27(4):  944-948.  doi:10.1016/j.cjche.2018.09.002
    Abstract ( 123 )   PDF (703KB) ( 24 )  
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    Titanium complex greases were prepared by using naphthenic mineral oil and polydimethylsiloxane as the mixed base oil. The effect of polydimethylsiloxane molecular weight and polydimethylsiloxane content in mixed base oil on the physicochemical and tribological properties of titanium complex greases was investigated. As compared to the sole mineral oil-based titanium complex grease, the use of polydimethylsiloxane (H201-350) as a co-base oil increased the dropping point from 310 to 329℃, decreased the oil separation from 3.7% to 2.3%, reduced the corrosion extent, and obviously improved the tribological properties. When the mixed oil-based titanium complex grease was used as a lubricant, lubricating films of polydimethylsiloxane were probably formed on the surfaces of friction pairs, giving good lubricating property.
    Removal of lead and cadmium ions by single and binary systems using phytogenic magnetic nanoparticles functionalized by 3-marcaptopropanic acid
    Imran Ali, Changsheng Peng, Iffat Naz
    2019, 27(4):  949-964.  doi:10.1016/j.cjche.2018.03.018
    Abstract ( 187 )   PDF (9111KB) ( 18 )  
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    The present research study is focused on green fabrication of superparamagnetic Phytogenic Magnetic Nanoparticles (PMNPs), and then its surface functionalization with 3-Mercaptopropionic acid (3-MPA). The resulting material (i.e. 3-MPA@PMNPs) characterized by FTIR, powder XRD, SEM, TEM, EDX, VSM, BET and TGA techniques and then further employed for the investigation of the adsorptive removal of lead (Pb2+) and cadmium (Cd2+) ions from aqueous solutions in single and binary systems. The material showed fastest adsorptive rate (98.23%) for Pb2+ and (96.5%) Cd2+ within the contact time of 60 min at pH 6.5 in the single system. The experimental data were fitted well to Langmuir isotherm, indicated monolayer adsorption of both metal ions onto 3-MPA@PMNPs and an estimated comparable adsorptive capacity of 68.41 mg·g-1 (Pb2+) and 79.8 mg·g-1 (Cd2+) at pH 6.5. However, kinetic data agreed well with pseudo-second-order model, and indicated that the removal mainly supported chemisorption and/or ion-exchange mechanism. Thermodynamic parameters such as ΔGo°, ΔHo°, and ΔSo°, were -3259.20, 119.35 and 20.73 for Pb2+, and -1491.10, 45.441 and 7.87 for Cd2+ at temperature 298.15 K, confirmed that adsorption was endothermic, spontaneous and favorable. The material demonstrated higher selectivity of Pb2+ and its removal efficiency was (98.20 ±0.3)% in binary system experiments. The material persisted performance up-to seven (07) consecutive treatment cycles without losing their stability and offered comparable fastest magnetic separation (35 s) from aqueous solutions. Therefore, it is recommended that the prepared material can be employed to remove toxic heavy metal ions from water/wastewaters and this "green" method can easily be implemented at large scale in low economy countries.
    Synthesis, characterization and electrochemical evaluation of anticorrosion property of a tetrapolymer for carbon steel in strong acid media
    Shamsuddeen A. Haladu, Saviour A. Umoren, Shaikh A. Ali, Moses M. Solomon, Abdul-Rashid I. Mohammed
    2019, 27(4):  965-978.  doi:10.1016/j.cjche.2018.07.015
    Abstract ( 165 )   PDF (8159KB) ( 15 )  
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    A novel tetrapolymer (TP) consisting of carboxylate, sulphonate, phosphonate and sulfur dioxide based comonomers was synthesized using Butler cyclopoymerization technique. The synthesized tetrapolymer was characterized using FTIR, 1H-NMR, 13C NMR and elemental analysis. The performance of the tetrapolymer as a corrosion inhibitor for St37 carbon steel in 15% HCl and 15% H2SO4 acid media was assessed using electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), potentiodynamic polarization (PDP) and electrochemical frequency modulation (EFM) techniques. The influence of addition of a small amount of KI on the corrosion inhibition efficiency of TP was also assessed. Results obtained showed that the tetrapolymer moderately inhibited the corrosion of St37 steel in the acid media with protection efficiency of 79.5% and 61.1% at the optimum concentration of 1000 mg·L-1 studied in HCl and H2SO4 media respectively. On addition of 5 mmol·L-1 KI to the optimum tetrapolymer concentration, the protection efficiency was upgraded to 90.6% and 93.5% in HCl and H2SO4 environment, respectively. The enhanced performance of the polymer in the presence of KI is due to synergistic action deduced from synergism parameter (S1) which was found to be greater than unity. The tetrapolymer afforded the corrosion inhibition of St37 steel in the acid media by virtue of adsorption of the polymer molecules on the steel surface which was confirmed by ATR-FTIR analysis of the adsorbed film extracted from the steel surface. TP + KI formed complex with St37 steel surface in H2SO4 solution but not in HCl solution.